Physiological Impacts and Lactational Performance of Dairy Cow Fed Brown Midrib Corn Silage During Dry Period Through Early to Midlactation

Transcription

1 Utah State University All Graduate Theses and Dissertations Graduate Studies Physiological Impacts and Lactational Performance of Dairy Cow Fed Brown Midrib Corn Silage During Dry Period Through Early to Midlactation Alexandra Windley Kelley Utah State University Follow this and additional works at: Part of the Agriculture Commons, and the Dairy Science Commons Recommended Citation Kelley, Alexandra Windley, "Physiological Impacts and Lactational Performance of Dairy Cow Fed Brown Midrib Corn Silage During Dry Period Through Early to Midlactation" (2014). All Graduate Theses and Dissertations This Thesis is brought to you for free and open access by the Graduate Studies at It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of For more information, please contact

2 PHYSIOLOGICAL IMPACTS AND LACTATIONAL PERFORMANCE OF DAIRY COWS FED BROWN MIDRIB CORN SILAGE DURING DRY PERIOD THROUGH Approved: EARLY TO MIDLACTATION by Alexandra Windley Kelley A thesis submitted in partial fulfillment of requirements for the degree of MASTER OF SCIENCE in Animal, Dairy, and Veterinary Sciences Dr. Jong-Su Eun Major Professor Dr. J. Earl Creech Committee Member Dr. Allen J. Young Committee Member Dr. Dirk K. Vanderwall Department Head Dr. Mark R. McLellan Vice President for Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2014

3 ii ABSTRACT Physiological Impacts and Lactational Performance of Dairy Cows Fed Brown Midrib Corn Silage During Dry Period Through Early to Midlactation by Alexandra Windley Kelley, Master of Science Utah State University, 2014 Major Professor: Dr. Jong-Su Eun Department: Animal, Dairy, and Veterinary Sciences Developing solutions to the metabolic stress experienced by cows during the transition period is very important because it can negatively influence lactational performance. The objectives were to: 1) compare physiological changes through body weight (BW) and concentrations of non-esterified fatty acids (NEFA) and β- hydroxybutyric acid (BHBA) and 2) evaluate feed intake, milk production, and energy balance (EB) of cows fed brown midrib corn silage (BMRCS)-based diets when compared with conventional corn silage (CCS)-based diets during the transition. At 4 wk prior to parturition, 40 dry multiparous Holstein cows were randomly assigned treatments. The treatment groups consisted of 2 close-up transition diets (CCS-based and BMRCS-based diet) offered to 2 groups of 20 cows each beginning at 4 wk prepartum. After calving, 10 cows from each prepartum group were individually fed 1 of 4 dietary treatments. The four dietary treatments postpartum were defined as follows: 1) CC = CCS-based close-up diet + CCS-based lactation diet; 2) CB = CCS-based close-up diet +

4 iii BMRCS-based lactation diet; 3) BB = BMRCS-based close-up diet + BMRCS-based lactation diet; 4) BC = BMRCS-based close-up diet + CCS-based lactation diet. Cows were sampled weekly for feed intake, and feed composition was taken monthly. After calving, milk yields were recorded daily and milk components were analyzed monthly. Body weights were taken twice per week on wk -4, -2, 1, 2, 3, 4, 8, 12, 16, and 20. Blood serum was sampled 3 times per week from wk -4 through 4 and then on wk 6, 8, 14, and 20. Rumen fluid was sampled on wk -4, 4, 8, 14, and 20. Feeding BMRCS-based diets during the transition did have a positive influence on dry matter intake, milk production, and energy balance. Interestingly, feeding BMRCS-based diets only during the close-up period and feeding a CCS-based diet during the lactation had similar positive effects as feeding a BMRCS-based diet through the dry period and during the lactation. This finding is meaningful because producers, especially in the Intermountain West, have experienced BMR crop yields that have been less than that of conventional crop yields and may be unwilling to utilize BMRCS in dairy rations. However, if feeding a BMRCSbased diet for a limited amount of time is beneficial, producers could be more willing to utilize this silage hybrid as an important transition period management tool. (70 pages)

5 iv PUBLIC ABSTRACT Physiological Impacts and Lactational Performance of Dairy Cows Fed Brown Midrib Corn Silage During Dry Period Through Early to Midlactation by Alexandra Windley Kelley, Master of Science Utah State University, 2014 Developing solutions to the metabolic stress experienced by cows during the transition period is very important because it can negatively influence lactational performance. The objectives were to: 1) compare physiological changes through body weight (BW) and concentrations of non-esterified fatty acids (NEFA) and β- hydroxybutyric acid (BHBA) and 2) evaluate feed intake, milk production, and energy balance (EB) of cows fed brown midrib corn silage (BMRCS)-based diets when compared with conventional corn silage (CCS)-based diets during the transition. At 4 wk prior to parturition, 40 dry multiparous Holstein cows were randomly assigned treatments. The treatment groups consisted of 2 close-up transition diets (CCS-based and BMRCS-based diet) offered to 2 groups of 20 cows each beginning at 4 wk prepartum. After calving, 10 cows from each prepartum group were individually fed one of four dietary treatments. The four dietary treatments postpartum were defined as follows: 1) CC = CCS-based close-up diet + CCS-based lactation diet; 2) CB = CCS-based close-up diet + BMRCS-based lactation diet; 3) BB = BMRCS-based close-up diet + BMRCSbased lactation diet; 4) BC = BMRCS-based close-up diet + CCS-based lactation diet. Cows were sampled weekly for feed intake, and feed composition was taken monthly. After calving, milk yields were recorded daily and milk components were analyzed monthly. Body weights were taken twice per week on wk -4, -2, 1, 2, 3, 4, 8, 12, 16, and 20. Blood serum was sampled 3 times per week from wk -4 through 4 and then on wk 6, 8, 14, and 20. Rumen fluid was sampled on wk -4, 4, 8, 14, and 20. Feeding BMRCSbased diets during the transition did have a positive influence on dry matter intake, milk production, and energy balance. Interestingly, feeding BMRCS-based diets only during the close-up period and feeding a CCS-based diet during the lactation had similar positive effects as feeding a BMRCS-based diet through the dry period and during the lactation. This finding is meaningful because producers, especially in the Intermountain West, have experienced BMR crop yields that have been less than that of conventional crop yields and may be unwilling to utilize BMRCS in dairy rations. However, if feeding a BMRCSbased diet for a limited amount of time is beneficial, producers could be more willing to utilize this silage hybrid as an important transition period management tool.

6 v ACKNOWLEDGMENTS I would like to express my gratitude for all those who have helped me on this journey. First I want to thank my husband, Andy, for his never-ending support of my goals and ambitions and his constant encouragement during my education. He has supported me in every way possible and never complained once even going as far as to help me sample my project cows over Thanksgiving, Christmas, and every other holiday when no one else was available. I would also like to thank my parents, siblings, and inlaws for their understanding and support when I couldn t always make it to family events. I appreciate their sincere interest in how my project and writing was going and am especially grateful that they always let me tell them all about it. All were encouraging and supportive in every way. No project of this magnitude is completed without assistance. I am ever thankful for all the members of the lab who helped with sampling, sample analysis, moral support, and anything else I needed. Braden Tye, Estelle Carr, Fona Cockett, and Yong-Joon Lee sacrificed much sleep and comfort to help me sample, always bright and early in the morning and even on weekends. Their help with sample analysis was also much appreciated. Katie Neal especially went above and beyond with her support and I am so grateful for her help and also her friendship. She had no responsibility to help me in any way but she helped me every week at the dairy and many more times every day in more ways than I can count. I am grateful for everyone at the dairy and their assistance, especially Jon Schumann and Glenn Mickelson. Organizing my project and keeping it going for 11 months was no small feat and I am grateful for their weekly management of

7 vi my cows and the employees that assisted us with feeding them and keeping them as comfortable as possible. I would like to thank my committee members for their guidance throughout this process and their individual support. I want to thank Dr. Creech for being willing to be on my committee even though he didn t know me. He was still so supportive and interested. I am grateful for Dr. Young and his encouragement when I needed it most and for always making time for me, no matter how busy he was. Finally, I would like to thank Dr. Eun. I am very grateful for his efforts on my thesis as well as all other aspects of my education. I am grateful for his guidance through this scientific writing process and for his efforts to help me have the best end result possible. I know he has worked many hours for my thesis so I could defend within a certain timeframe and I am ever grateful for his dedication. I am also extremely grateful to Mycogen Seeds for financially supporting this project and giving me this opportunity in the first place. Alli Kelley

8 vii CONTENTS Page ABSTRACT... ii PUBLIC ABSTRACT... iv ACKNOWLEDGMENTS...v LIST OF TABLES... ix LIST OF FIGURES...x LIST OF ABBREVIATIONS... xi INTRODUCTION... 1 REVIEW OF LITERATURE... 4 Energy Balance... 4 The Transition Period... 7 The dry period... 7 Early lactation... 7 Effects of the dry period on early lactation... 8 Blood Parameters during the Transition... 9 Non-esterified fatty acids... 9 Ketone bodies Glucose Dry Matter Intake Changes in DMI during the transition Intake and hormone changes relate to metabolism changes during the transition... 17

9 viii Brown Midrib Corn Silage Effect of BMR on DMI and fiber digestibility Ruminal fermentation characteristics MATERIALS AND METHODS Cows and Experimental Design and Diets Feed Sampling and Analysis Blood Serum Sampling and Analysis Ruminal Fluid Sampling and Analysis Statistical Analyses RESULTS AND DISCUSSION Diet Composition and Dietary Treatments Prepartum BW, Blood Parameters and DMI Postpartum Blood Parameters, DMI, and Milk Production Feed Efficiency, BW, and Net Energy Utilization Postpartum Ruminal Fermentation Characteristics CONCLUSIONS REFERENCES... 51

10 ix LIST OF TABLES Table Page 1. Parity, BW, and milk production of ketotic and nonketotic cows Chemical composition (means ± SD) of forages Ingredients and nutrient composition (means ± SD) of the prepartum experimental diets Ingredients and nutrient composition (means ± SD) of the postpartum experimental diets Body weight of Holstein dairy cows fed CCS vs. BMRCS prepartum (wk -4 and -2) Productive performance of Holstein dairy cows fed corn silage-based diets through peak lactation (wk 1, 4, and 8) Productive performance of Holstein dairy cows fed corn silage-based diets from peak lactation through midlactation (wk 12, 16, and 20) Dairy efficiency, BW, and net energy utilization of Holstein dairy cows fed corn silage-based diets through peak lactation (wk 1, 4, and 8) Dairy efficiency, BW, and net energy utilization of Holstein dairy cows fed corn silage-based diets from peak lactation through midlactation (wk 12, 16, and 20) Ruminal fermentation characteristics of Holstein dairy cows fed corn silage-based diets through midlactation (wk 4, 8, 14, and 20)... 50

11 x LIST OF FIGURES Figure Page 1. Energy intake ( ), requirements ( ) and balance ( ) (mega joules (MJ) of NEL per day) and milk production ( ) (kilograms per day) over DIM Production and metabolism of NEFA The pattern of voluntary DMI around calving in heifers and cows Mean concentrations of NEFA, BHBA, and glucose in dairy cows in wk 3 prepartum (wk -3) and in wk 4 (+4 wk) and 13 (+13 wk) postpartum Experimental layout and dietary treatments tested prepartum and postpartum Blood parameters of Holstein dairy cows fed corn silage-based diets prepartum at wk -4 up to wk 20 of lactation Dry matter intake of Holstein dairy cows fed corn silage-based diets prepartum at wk -4 up to wk 20 of lactation Milk yields of Holstein dairy cows fed corn silage-based diets at wk 1 up to wk 20 of lactation Net energy utilization for milk of Holstein dairy cows fed corn silage-based diets at wk 1 up to wk 20 of lactation Net energy for lactation based on DMI of Holstein dairy cows fed corn silagebased diets at wk 1 up to wk 20 of lactation... 48

12 xi LIST OF ABBREVIATIONS ADF = acid detergent fiber ATP = adenosine triphosphate BB = brown midrib corn silage-based TMR prepartum and postpartum BC = brown midrib corn silage-based TMR prepartum and conventional corn silagebased TMR postpartum BCS = body condition score BHBA = β-hydroxybutyric acid BMRCS = brown midrib corn silage-based TMR BMR = brown midrib BW = body weight CB = conventional corn silage-based TMR prepartum and brown midrib corn silagebased TMR postpartum CC = conventional corn silage-based TMR prepartum and postpartum CCS = conventional corn silage-based TMR CP = crude protein CS = corn silage DCAD = dietary cation-anion difference DIM = days in milk DM = dry matter DMI = dry matter intake EB = energy balance

13 xii LFC = liver fat concentrations MJ = mega joules MUN = milk urea nitrogen NDF = neutral detergent fiber NE = Net energy NEB = negative energy balance NEFA = non-esterified fatty acid NEL = net energy lactation NH3-N = ammonia nitrogen NRC = national research council OM = organic matter PEB = positive energy balance RDP = ruminally degradable protein RUP = ruminally undegradable protein SBMCM = soybean meal canola meal 50:50 mix TAG = triacylglycerides TMR = total mixed ration TP = true protein VFA = volatile fatty acids

14 INTRODUCTION During the past decade, dairy producers have increased their use of corn silage (CS) as a forage source in dairy rations. This has been influenced by a few factors including high price of corn grain feed and high energy content of CS. Feeding forage levels at 55 to 60% of dietary dry matter (DM) is becoming more common, but this can create a problem. Lack of energy from concentrates and distention from rumen fill can limit DM intake (DMI) which can reduce the performance of high producing dairy cows (Zebeli et al., 2012). In order to achieve high milk production, dairy cows must have adequate DMI. Because of this, great emphasis has been placed on dietary factors affecting the DMI of lactating dairy cows. Physical fill can be the most limiting mechanism of DMI for high yielding cows around peak lactation (Allen, 2000), and can also be a limiting mechanism of DMI during the close-up period (Ingvartsen and Andersen, 2000). One of the most challenging times for a dairy cow is the transition period. The transition period is often defined as 3-4 wk prior to calving, or the close-up period, up until 4 wk post calving. This is a challenging time for cows, because they often enter a negative energy balance (NEB). When a cow is in NEB, she is requiring more energy than she is able to take in (De Vries et al., 1999). During the transition period, control of feed intake is likely dominated by hepatic oxidation of NEFA (Allen et al., 2009). When cows enter a NEB, they will start to utilize body stores of energy, lowering BW and body condition score (BCS). A cow s body stores of energy that were built up during the dry period will be insufficient to meet the intense demand placed on her body when she begins lactating, which can lead to various metabolic problems (Coffey et al., 2002).

15 2 Some of the most common metabolic problems cows experience during the transition period are ketosis and fatty liver. Ketosis is a result of NEB. When body energy stores are mobilized, NEFA and ketone body [acetoacetate, BHBA, and acetone) concentrations are elevated. Elevated NEFA concentrations contribute to ketosis, because the liver becomes overloaded with triglycerides, forcing an increased number of fatty acids to undergo incomplete oxidation into ketone bodies (Weber et al., 2013a). Other health problems like left-displaced abomasum can have increased incidence when a cow is ketotic and ketosis can also impair the function of immune cells in the blood and milk (Graber et al., 2010). Minimizing NEB and maximizing energy intake are two of most critical management aspects associated with feeding dairy cows in early lactation. Finding an optimal balance between physically effective fiber and readily fermentable carbohydrates is difficult but crucial not only for maintaining proper ruminal metabolism (Zebeli et al., 2006), but also for maintaining a stable metabolic health status while enhancing productivity (Zebeli et al., 2012). One way to help mitigate this problem of NEB during the transition period is to feed a more digestible feed so that instead of decreasing DMI during the transition, it would remain constant or even increase. Subsequently, this would provide the cow with more energy at the start of her lactation and reduce metabolic stress. An option for a more digestible feed source is BMRCS which is a CS hybrid that has a lower lignin concentration and consequently higher digestibility than CCS (Holt et al., 2010). Feeding forages with enhanced digestibility of neutral detergent fiber (NDF) has been reported to improve DMI and milk yield (Oba and Allen, 1999a). Brown midrib corn silage has been well documented to have higher NDF digestibility and will likely increase

16 3 DMI and milk yield compared to cows fed CCS. Because of the increased fiber digestibility, BMRCS-based diets would increase DMI during the transition period and therefore increase nutrient supply. Brown midrib corn silage has already been shown to mitigate BW loss prior to peak lactation (Holt et al., 2013), indicating that it would also be beneficial for overall metabolic status during the transition period. Brown midrib CS demonstrates many benefits, but some farmers are hesitant to grow it due to lower yields of BMR hybrid crops, although the yields can be somewhat offset by the higher digestibility of the fiber, making it a better quality forage (Holt et al., 2010). Because of this concern, if a dairy farmer does not want to grow all BMR corn hybrid or if the farmer is unable to get enough BMRCS, feeding BMRCS-based diets only at certain times, such as during the transition period, could be an option. Little data is currently available regarding the influence of feeding BMRCS-based diet on physiological changes, control of feed intake, milk production, and nutrition utilization during the transition period as well early and midlactation. Research presented here will test the hypothesis that feed intake and milk yields will increase when cows are fed BMRCS-based diet during the transition and lactation periods due to increased nutrient digestion through feeding BMRCS-based diets.

17 4 REVIEW OF LITERATURE The transition period is metabolically a crucial time for a dairy cow. Her diet during the close-up period before calving will influence her positively or negatively after calving and throughout her lactation. It is the purpose of this review to examine the effects EB, metabolic parameters, and intake can have on a cow in the transition period. It will also examine how corn silage hybrids can benefit the cow during this challenging time. Energy Balance After a cow calves and begins her lactation, she is often unable to meet the energy demands associated with her production levels. This can cause a NEB, which is a state of requiring more energy than she can consume prior to peak lactation (De Vries et al., 1999). Cows enter a state of NEB when they cannot sustain the metabolic load placed on their body from production, which leads to metabolic stress (Collard et al., 2000). De Vries et al. (1999) conducted a field study to examine EB in first, second, and third lactation cows, and they found that over all the test groups, it took 120 to 150 days-inmilk (DIM) for the cows EB to stabilize (Figure 1). This study also showed that for all lactations on average, the energy deficit in the NEB was approximately equal to the amount of energy required for one cow to produce 540 kg of fat- and protein-corrected milk during the time she was returning to a positive energy balance (PEB; De Vries et al., 1999). A cow in a NEB will start mobilizing body stores of energy (Collard et al., 2000). A cows BCS can be a good indicator of a NEB and that body stores are being utilized. If

18 5 a cow is mobilizing her body fat stores to meet energy demands, her BCS will decrease (De Vries and Veerkamp, 2000). When a cow has experienced NEB, she may be able to regain condition by the end of the lactation, or she may need to continue to gain condition during the dry period. If condition is not adequately gained back at that time, it may not be gained back until after the next lactation. Both of these scenarios will increase the possibility that cows may experience metabolic health problems as well as fertility issues (Coffey et al., 2002). Figure 1. Energy intake ( ), requirements ( ) and balance ( ) (mega joules (MJ) of NEL per day) and milk production ( ) (kilograms per day) over DIM (De Vries et al., 1999).

19 6 Collard et al. (2000) tried to estimate if there was a relationship between a cow s EB during early lactation and her health during that same lactation. They used 140 cows over 6 years and measured performance parameters (DMI and BW) and all health information. All cows were fed a similar ration that was balanced for what they defined as high production, or more than 36 kg/d of milk. Estimates of EB were calculated by evaluating the severity and length of NEB and how long it lasted, along with the cows total energy deficit. Energy balance was calculated daily by multiplying DMI by the concentration of net energy in the TMR and subtracting the expected amount of energy required for maintenance based on parity and BW. The severity of the NEB was evaluated by the minimum daily EB the cow had during a 5 day period. Collard et al. (2000) investigated various health problems but their data indicated specifically that locomotion problems, such as laminitis, are associated with a NEB and more specifically the intensity of the metabolic stress, not the duration. They also point out the negative affect NEB can have on digestion. When a cow has inadequate DMI, the deficit is often compensated for by increasing the amount of concentrates with readily digestible carbohydrates being fed. This decreases saliva production and rumination time because of the decrease in forages which in turn decreases ruminal ph. Not only can this lead to acidosis, it can also lead to lameness, specifically laminitis or other locomotion problems. When cows are lame, they spend more time resting than eating, further exacerbating the problem of NEB.

20 7 The Transition Period The dry period The dry period is usually described as having 2 categories, far-off dry which is the 4 to 6 wk before parturition or close-up dry which is usually the last 3 wk before parturition (Dann et al., 2006). Nutrition during the entire dry period is important because it can have an effect on metabolic health and therefore the subsequent lactational performance of the cow (Dann et al., 2005). The feeding program during the dry period can impact a lactation because a cow will use stored body reserves after parturition to meet her energy demands. Although this is a normal process for all mammals, the modern dairy cow has a particularly difficult time meeting these energy requirements without having health problems (Agenäs et al., 2003). Early lactation Early lactation is defined as the period immediately following calving until about 4-6 wk after calving. This period is often when metabolic problems are evidenced by a cow s poor productive performance and poor health metabolically or overall. Although DMI will start to increase during this period, it is not an immediate increase following calving and the change does not adequately match productive performance leading to DMI deficits during this time (Ingvartsen and Andersen, 2000).

21 8 Effects of the dry period on early lactation Because of the correlation between nutrition during the dry period and lactational performance, it is important to determine how changing what is being fed during the dry period will affect early lactation and how EB can be improved in early lactation. The objective of a study done by Dann et al. (2006) was to determine the effects of dry period diet, both far-off and close-up, on metabolism and lactational performance postpartum. In the far-off period, 86 multiparous Holstein cows were feed either a control diet, meeting National Research Council (NRC) requirements for net energy for lactation (NE L ), or a higher density diet supplying a minimum of 150% of NEL requirements. Both diets were fed ad libitum. During the close-up period, cows were fed a diet that either met or exceeded the NRC recommendations at either ad libitum or restricted intake. Restricted intake diets were calculated to provide 80% of the NEL requirement. After all cows calved, they were switched to a common lactation diet. Dann et al. (2006) found that during the far off period, DMI and EB were significantly higher with the diet supplying 150% of NEL requirements. Although glucose concentrations in blood serum were similar, insulin was much higher in cows fed the energy dense diet (150% of NEL). In the close-up period, because one diet was restricted (80% of the NEL), those cows had a lower DMI which resulted in a NEB for those cows. Cows on the restricted diet also had lower BW and insulin concentrations and higher NEFA concentrations, which corresponded to higher lipid concentrations in the liver. After calving, Dann et al. (2006) observed cows up to 56 DIM. Although DMI was not statistically different postpartum based on prepartum diets for the entire dry period, NEFA concentrations had a tendency

22 9 to be higher for cows fed the energy dense diet only in the far-off period than those fed a restricted diet; β-hydroxybutyric acid followed a similar pattern. The energy restricted cows recovered EB quicker than the cows fed an energy dense diet. These results led Dann et al. (2006) to conclude that cows that are overfed during the far-off dry period have a greater chance of being in a NEB and therefore have a greater risk for metabolic health problems. This study by Dann et al. (2006) demonstrates the important point that what is fed during the dry period can and will have important repercussions in early lactation. Although this study looked at energy dense diets and energy restricted diets, there are many other ways EB can be manipulated in early lactation. Blood Parameters During the Transition Energy demands on a cow s body after parturition for maintenance can be approximately 3 times higher than they were before calving (Weber et al., 2013b). The demand these physiological changes have on a cow are expressed through several parameters commonly measured to reflect this change: glucose, BHBA, and NEFA concentrations (van Dorland et al., 2009). Non-esterified fatty acids Studies have shown (Winkelman et al., 2008) that if a cow has a high BCS prepartum, they have an increased incidence of mobilization of body fat stores to meet energy demands postpartum. Because of this preference to mobilize fat stores for extra energy, plasma concentrations of NEFA are increased (Weber et al., 2013b). When

23 10 NEFA are taken up by the liver, they can either be oxidized completely creating carbon dioxide, oxidized incompletely creating ketone bodies, or reesterified and then stored as triacylglycerides (TAG) (Figure 2; Weber et al., 2013a). When NEFA plasma concentrations increase and TAG concentrations in the liver increase, cows experience metabolic stress that can eventually lead to poor overall health, decreased lactational performance, and poor reproductive performance (Ingvartsen and Andersen, 2000). Hormone changes occurring during the transition period drive these negative associations with increased TAG in the liver. Fatty liver syndrome is a result of increased levels of TAG in the liver. Often, cows with fatty liver have an increased level of NEB because the high TAG concentrations affect hormone changes and decrease the amount of gluconeogenesis the liver can perform (Allen et al., 2009). The hormone that drives all of these changes during the transition period is insulin. Immediately following parturition, insulin level decrease which reduces glucose uptake into insulin sensitive organs like the muscle and adipose tissue. This shift favors insulin uptake in the mammary gland, shuttling energy for higher production. This creates the increased drive for body fat mobilization and therefore the increased TAG concentrations in the liver. This lowered insulin in glucose sensitive organs was shown by giving lactating and non-lactating cows a glucose infusion. In cows given the glucose infusion, pancreatic insulin stimulation was lower in lactating cows compared with non-lactating cows (Aschenbach et al., 2010).

24 Figure 2. Production and metabolism of NEFA (Cornell University, 2013). 11

25 12 Weber et al. (2013b) studied how lipid metabolism was impaired by increased fat mobilization during the transition period. They also studied strategies that could be developed to better adapt metabolism and hormone changes to energy metabolism in high yielding dairy cows. They looked at cows of the same lactation, kept in the same conditions and diets, but differing only in liver fat concentrations (LFC). In all cows, LFC was higher post calving for 2 wk than it was prior to calving but the proportions of LFC between the groups remained the same. Plasma NEFA concentrations were also higher post calving, being higher for 2 wk longer in the group with the higher LFC. Plasma TAG concentrations followed this same pattern. The group determined that although there were no marked differences in milk yield and milk energy, cows in the group with the highest LFC had increased acetone concentrations in their milk, indicating that NEFA were being oxidized to ketone bodies. They unexpectedly found that cows in the group with medium LFC had the highest rates of fat mobilization, but lower plasma NEFA concentrations compared to the cows in the high LFC group. Overall, although all cows mobilized body fat, NEFA concentrations were lower in cows with the lowest LFC. Weber et al. (2013b) concludes that this correlation of low LFC to low NEFA concentrations is most likely due to decreased DMI, but acknowledges that none of the cows had clinical fatty liver, indicating individual adaptation by each cow per her LFC concentration, DMI, and energy metabolism to milk production. They speculate this could be due to which fat depots were being mobilized, but suggest further investigation.

26 13 Ketone bodies After parturition, ketosis is common in dairy cows because cows in NEB experience elevated concentrations of NEFA and ketone bodies (acetoacetate, BHBA, acetone). Ketosis is determined by measuring BHBA concentrations in the blood. Ketotic cows often have lower BW and milk production when compared to nonketotic cows so avoiding ketosis in a dairy herd is ideal (Table 1; Li et al., 2012). As mentioned before, body fat is mobilized and used for energy during the transition period. When the liver becomes overloaded with NEFA, a greater amount undergoes incomplete oxidation into ketone bodies leading to ketosis or in most cases subclinical ketosis (Weber et al., 2013a). Finding methods to mitigate this problem would be beneficial because as many as 40-60% of herds have cases of subclinical ketosis in early lactation cows even though only 2-15% of herds regularly report clinical ketosis (McArt et al., 2012). Subclinical ketosis is a major problem because it can lead to displaced abomasum, poor reproductive performance, early culling, and losses in milk yield during early lactation. It has also been estimated that economic losses associated with these problems are $211 per case of clinical ketosis and $78 per case of subclinical ketosis (McArt et al., 2013). Table 1. Parity, BW, and milk production of ketotic and nonketotic cows (Li et al., 2012) Item Ketotic cows (n=6) Nonketotic cows (n=6) Parity 3.8 ± ± 1.1 BW (kg) ± ± Milk production (kg/d) ± ± P< ± means standard error

27 14 McArt et al. (2012) studied 2 commercial dairy farms to determine subclinical ketosis in early lactation cows and what BHBA concentration were indicative of subclinical ketosis. They also monitored the development of a displaced abomasum in cows with subclinical ketosis. To track BHBA concentration, they used a handheld Precision Xtra meter and defined ketosis as a BHBA concentration of 1.2 to 2.9 mmol/l. Of the cows in the study, 43.2% were determined to have subclinical ketosis within 30 DIM. The average DIM for cows to develop subclinical ketosis was 5. It took up to 14 DIM for cows to recover from subclinical ketosis and have BHBA concentrations out of the defined range. Of the non-ketotic cows, only 0.3% developed a displaced abomasum while 6.5% of the subclinical ketotic cows developed a displaced abomasum and it was determined that ketotic cows were 19.3 times more likely to develop a displaced abomasum. All the cows that had subclinical ketosis and a displaced abomasum within 30 DIM, had BHBA concentrations in the range for subclinical ketosis within 3-5 DIM. The authors concluded that when cows develop subclinical ketosis within the first week of calving, they are also more likely to develop displaced abomasum eventually leading to decreased milk production and a greater chance of being removed from the herd within the first 30 DIM. Glucose Following parturition, hormonal changes affect in how glucose is metabolized. Less glucose is used in the peripheral tissues, like muscle and adipose, and more is used in the mammary gland (Overton and Waldron, 2004). This high priority and high demand for glucose in the mammary gland also causes a shift in hepatic gluconeogenesis. The

28 15 liver increases its glucose production to try and meet these changing and increasing energy demands (Hammon et al., 2009). Overton and Waldron (2004) have suggested that there is a 267% total increase in the glucose output from splanchnic tissues from about 9 d before calving to about 21 d following calving. Almost all of this increase is due to increased hepatic gluconeogenesis. As discussed earlier, TAG buildup can become so great that cows develop fatty liver syndrome which can impair hepatic glucogenic capacity. Although NEFA are needed by the liver to provide adenosine triphosphate (ATP) for gluconeogenesis, too much can be damaging (Hammon et al., 2009). Hammon et al. (2009) performed a study specifically looking at glucose metabolism in highyielding dairy cows with either low or high LFC. They found significantly increased plasma NEFA and BHBA concentrations from parturition to 28 DIM for cows with high LFC; but no significant difference for low LFC cows. Even with these significant changes in NEFA and BHBA concentrations, there was only slight decreases in plasma glucose concentrations prior to parturition and only a tendency for the concentrations to be lower in the high LFC cows. The authors did not look at endogenous glucose output and could not determine what these decreased glucose concentrations were due to, but suggested that individual cow factors influence the transition period more than previously thought. Although glucose plays an important role in the metabolic patterns seen around the transition period, it can be difficult to determine significant changes in glucose concentrations because blood glucose is maintained at stable levels. Because of this, BHBA and NEFA concentration data are used to determine changes during the transition period.

29 16 Dry Matter Intake Dry matter intake is critically important for dairy cows because it is one of the main influencing factors affecting milk yield. There are many factors that can affect DMI throughout a cow s lactation, but in particular during the transition period (Ingvartsen and Andersen, 2000). Dry matter intake can be greatly affected during the transition because there are so many physical and hormonal changes happening during that time. Changes in DMI during the transition Prior to calving, DMI has been shown to decrease in dairy heifers by 0.17 kg per wk from 26 wk of pregnancy to 3 wk before calving (Ingvartsen and Anderson, 2000). In Holstein cows, DMI can decrease 32% from approximately 21 d prepartum until calving. For dairy heifers or cows the lowest intakes are at calving (French, 2006). After calving, intakes will gradually increase, but DMI usually peaks after peak milk production. This is increase is variable and depends on the BCS and possibly prepartum diet along with lactation diet (Ingvartsen and Anderson, 2000). Figure 3 demonstrates these trends, decreasing DMI prior to calving with DMI increasing shortly after calving, but not peaking until wk 18-24, after a cow has reached peak milk production.

30 17 Figure 3. The pattern of voluntary DMI around calving in heifers and cows (Ingvartsen and Anderson, 2000). Intake and hormone changes relate to metabolism changes during the transition Along with changing DMI in the close-up period, a cow s energy demands increase due to the growing fetus. These demands are reflected in metabolic changes influenced by the type of energy supply in her diet. These changes are clearly reflected in blood parameters like blood glucose, NEFA, and BHBA concentrations. When DMI is depressed, as often happens close to calving, there is a negative relationship between DMI and NEFA levels (French, 2006). In a cow with an energetically dense diet, prepartum plasma concentrations of glucose will be high while NEFA and BHBA concentrations will be low. Looking at the same cow postpartum will reflect the converse, low glucose and high NEFA and BHBA plasma concentrations. This

31 18 phenomenon indicates a need for more energy by the mammary gland after calving for milk production (Ingvartsen and Anderson, 2000). Allen et al. (2009) explain the decreased DMI and the changes in glucose and NEFA concentrations are due to a decreased sensitivity in the adipose tissue to insulin. This decreased sensitivity allows fat to be stored in the liver and later used as energy, resulting in increased NEFA concentrations postpartum. Because of increased TAG concentrations in the liver, the livers ability to perform gluconeogenesis is decreased, making the time required to recover normal plasma glucose concentrations. Grummer et al. (2004) reasons that although decreased rumen volume is potentially a factor for decreases in DMI, a more likely reason during the transition period is steroid hormone concentration changes prepartum, (i.e. estradiol). When cows experience low blood glucose concentrations with high blood NEFA and BHBA concentrations, indicative of a NEB, metabolic disorders are very common. Risk for a left-displaced abomasum increases when high concentrations of ketone bodies are in the blood. Ketone bodies also can lower milk and blood immune cell function (Graber et al., 2010). Negative energy balance can also be associated with non-metabolic problems such as retained placenta and a greater risk for infection. Increasing feed intakes prepartum could be a practical way to mitigate these metabolic issues in the transition period because most of the time a NEB prepartum is caused by a decrease in DMI (Grummer et al., 2004). Figure 4 demonstrates the typical pattern observed during the transition period for BHBA, NEFA, and glucose concentrations.

32 19 Figure 4. Mean concentrations of NEFA, BHBA, and glucose in dairy cows in wk 3 prepartum (wk -3) and in wk 4 (+4 wk) and 13 (+13 wk) postpartum. Different letters (a, b, c) indicate differences (P < 0.05) between the measured time points (Graber et al., 2010). Brown Midrib Corn Silage Brown midrib (BMR) corn plants have been studied for decades. The first BMR plant appeared in a self-pollinated line of dent corn in The gene responsible for the BMR phenotype was named bm1 and later more genes were described: bm2 (1932), bm3 (1935), and bm4 (1947; Barrière et al., 2004). What makes these hybrids unique is the lowered lignin content in the cell wall. Lignin is resistant to bacterial and fungal degradation in the gut and is probably the only cell wall component to have such a property. The association of lignin with other cell wall matrix components can greatly influence cell wall properties like the degradability of structural polysaccharides by

33 20 enzymatic means (Grabber et al., 2004). The study of these BMR hybrids is what first lead researchers to believe that the amount of lignification could impact digestibility. The majority of focus in corn has been on the bm3 mutant because of its ability to increase feed value. These bm3 mutants have 25 to 40% reduced lignin content and have consistently lower lignin at all stages of maturity (Barrière et al., 2004). Lignin is a polymer in plants that is indigestible but important to maintain the structural integrity of the plant tissue. Lignin is the main component of the cell wall that can limit digestion, even though it makes up little of the total carbohydrate system of the plant. Lignin will reduce digestibility because of strong covalent bonds that form with hemicellulose in addition to its ability to physically block enzymes from accessing the digestible carbohydrate part of the plant structure (Holt, 2013). Effect of BMR on DMI and fiber digestibility Research in using BMR hybrids for silage began in the early 1970 s. In vitro studies agreed with in vivo studies that feeding BMRCS increased digestibility. In a study on sheep fed silage made from the bm3 hybrid, it was found that there was greater digestibility of fiber as well as increased DMI compared with sheep fed a conventional silage (Sommerfeldt et al., 1979). Subsequent studies on heifers showed the same results with the addition of increased growth and feed efficiencies (Rook et al., 1977). Recent studies of BMRCS in lactating dairy cows show somewhat varied results with some reports of no difference when compared with a CCS and some reports of improved lactational performance (Kung et al., 2008; Holt et al., 2013). Fiber digestibility plays an important role in maintaining a positive rumen environment. Without a proper balance of

34 21 physically effective fiber and readily fermentable carbohydrates, proper ruminal metabolism cannot be maintained (Zebeli et al., 2006) and neither can a stable metabolic health status while still improving productivity (Zebeli et al., 2012). A challenge with fiber digestibility can be physical fill and limiting DMI. Oba and Allen (2000) report that the fibrous fractions of feed will have a greater impact on physical fill than the non-fiber fractions because of the slow fermentation and longer rumen retention time of fiber. They also report that the digestibility forage NDF can impact an animal s performance regardless of the overall concentration of NDF in the diet. Additionally, Oba and Allen (1999b) found that in vitro NDF digestibility was associated with an increase in DMI by 0.17 kg. If NDF is more digestible, rumen fill would be decreased and DMI could be increased. The concentration, digestibility, and fragility of forage NDF contributes most to the rumen-filling effect of a diet (Holt et al., 2013). Because brown midrib hybrids have less lignification of the plant cell wall, increasing their NDF digestibility with little difference in NDF and crude protein (CP) content (Holt, 2013). When compared with a control silage, the digestibility in vitro of NDF by the BMR hybrid improved productivity overall in lactating dairy cows (Oba and Allen, 2000). Because of the increased fiber digestibility, BMR hybrids are a good option to increase DMI and subsequently diet energy during the transition period. Ruminal Fermentation Characteristics Ruminal fermentation characteristics can also be effected by feeding a BMRCS. Feeding BMRCS can shift the site of digestion from the rumen to the intestines. Due to greater DMI associated with feeding BMRCS increasing rate of passage. Consequently

35 22 this shift in digestion to the intestines could lead to greater glucose availability in BMRCS diets (Oba and Allen, 2000). A study done by Greenfield et al. (2001) reported that compared with normal corn silages, ruminal starch digestibility of BMRCS was decreased by 36%. However, no difference in total tract digestibility was observed leading the authors to reason that this postruminal starch digestion was compensatory. Ruminal ph can also be lowered by feeding BMRCS because it is a more fermentable forage source and ruminal NDF digestibility may be reduced as well (Oba and Allen, 2000). Greenfield et al. (2001) reported a decrease in ruminal ph when cows were fed BMRCS-based diets. Taylor and Allen (2005) also saw decreased ruminal ph when comparing BMRCS-based diets to CCS-based diets (5.99 vs. 6.22) and a corresponding 3.5 mm higher total VFA concentration in the BMRCS-based diet. This would suggest that the decreased ruminal ph is due to increased total VFA concentrations. Other studies (Qiu et al., 2003; Holt et al., 2010) found no effects on ruminal ph or total VFA concentration when feeding BMRCS-based diets. Little data is currently available regarding the influence of feeding BMRCS-based diet on physiological changes, control of feed intake, milk production, and nutrition utilization during the transition period as well early and midlactation. Research presented here will test the hypothesis that feed intake and milk yields will increase when cows are fed BMRCS-based diet during the transition and lactation periods due to increased nutrient digestion through feeding BMRCS-based diets.

36 23 MATERIALS AND METHODS The dairy cows used in this study were cared for according to the Live Animal Use in Research Guidelines of the Institutional Animal Care and Use Committee at Utah State University (approved protocol number: 2213). The dairy experiment was conducted at the Caine Dairy Research Center (Wellsville, UT), Utah State University. Cows and Experimental Design and Diets Forty multiparous Holstein cows were used in this study. Cows were blocked by previous lactation and parity into 4 treatment groups and used in this study from 4 wk prepartum through 20 wk postpartum. The treatment groups consisted of 2 close-up transition diets (CCS-based or BMRCS-based diet) of 20 cows each beginning at 4 wk prepartum. After calving, 10 cows from each prepartum group were individually fed either a CCS-based lactation diet or a BMRCS-based lactation diet. Four dietary treatments tested postpartum included: 1) CC = CCS-based close-up diet + CCS-based lactation diet; 2) CB = CCS-based close-up diet + BMRCS-based lactation diet; 3) BB = BMRCS-based close-up diet + BMRCS-based lactation diet; 4) BC = BMRCS-based close-up diet + CCS-based lactation diet (Figure 5). The number of animals that completed the trial for each group were 7, 8, 9, and 8 for CC, CB, BB, and BC, respectively. Animals removed from the study were removed for the following reasons: 5 for starting the study under the pretense they were pregnant but were not, 1 for terminal illness (cancer), and 2 for severe milk fever.

37 24 The chemical composition of feed components is shown in Table 2, ingredient and nutrient composition of the close-up diets is shown in Table 3, and the lactation diets in Table 4. Close-up rations were formulated based on NRC (2001) recommendations to provide sufficient NEL, metabolizable protein, vitamins, and minerals to provide the appropriate dietary cation-anion difference (DCAD) requirements. Diets were isocaloric and isonitrogenous across treatments averaging 11.9% CP and are typical of a close-up dry cow ration in the Intermountain West (i.e., Utah, Idaho, Wyoming, Montana, and parts of Arizona and Nevada). Lactation rations were formulated based on NRC (2001) recommendations to provide sufficient NEL, metabolizable protein, vitamins, and minerals to produce 40 kg/d of milk with 3.5% fat and 3.0% true protein (TP) with the inclusion of Rumensin (Elanco Animal Health, Greenfield, IN). Diets were isocaloric and isonitrogenous across treatments averaging 15.4% CP and are typical of a highforage diet for high producing dairy cows in the Intermountain West. Table 2. Chemical composition (means ± SD) of forages Forages 1 Item, % of DM Conventional CS Brown midrib CS Oat hay Alfalfa hay DM, % 40.3 ± ± ± ± 1.07 OM 94.6 ± ± ± ± 6.99 CP 8.72 ± ± ± ± 3.16 NDF 37.9 ± ± ± ± 3.85 ADF 20.7 ± ± ± ± CCS = conventional corn silage; BMRCS = brown midrib corn silage.

38 Table 3. Ingredients and nutrient composition (means ± SD) of the prepartum experimental diets Prepartum Item CCS 1 BMRCS 1 Ingredient, % of DM Conventional corn silage 30.7 Brown midrib corn silage 31.2 Oat hay Alfalfa hay Corn grain, flaked SBMCM Beet pulp shred SoyChlor Vitamin and mineral mix Chemical composition, % of DM DM, % 56.8 ± ± 3.68 OM 90.4 ± ± 9.26 CP 11.9 ± ± 1.17 RDP, 5 % of CP RUP, 5 % of CP NDF 39.7 ± ± 2.14 ADF 23.2 ± ± 0.89 NEL 6, Mcal/kg 4.00 ± ± CCS = conventional corn silage-based TMR; BMRCS = brown midrib corn silage-based TMR. 2 Mixture of soybean meal and canola meal at 50:50 in a DM basis. 3 West Central Cooperative, Ralston, Iowa. 4 Formulated to contain (per kg DM): mg of Ca, mg of P, mg K, mg S, mg Fe, mg of Se, mg of Cu, mg of Zn, mg of Mn, mg I, 221,346.4 IU of vitamin A, 64,959.4 IU of vitamin D, and 4,365.3 IU of vitamin E. 5 Based on tabular value (NRC, 2001). 25

39 Table 4. Ingredients and chemical nutrient (means ± SD) of the postpartum experimental diets Postpartum Item CCS 1 BMRCS 1 Ingredient, % of DM Conventional corn silage 30.6 Brown midrib corn silage 31.0 Alfalfa hay Corn grain, flaked Corn DDGS SBMCM Cottonseed, whole Beet pulp shred Sodium bicarbonate Vitamin and mineral mix Chemical composition, % of DM DM, % 60.2 ± ± 3.62 OM 90.3 ± ± 0.91 CP 15.2 ± ± 1.10 RDP, 5 % of CP RUP, 5 % of CP NDF 31.7 ± ± 1.99 ADF 19.3 ± ± 1.29 NEL, 5 Mcal/kg CCS = conventional corn silage-based TMR; BMRCS = brown midrib corn silage-based TMR. 2 DDGS = dried distillers grains with solubles. 3 Mixture of soybean meal and canola meal at 50:50 in a DM basis. 4 Formulated to contain (per kg DM): mg of Ca, mg of Mg, mg of S, mg of Na, mg of Cl, mg Fe, mg of Se, mg of Cu, mg of Zn, mg of Mn, mg of Co, mg of I, 378,809.2 IU of vitamin A, 46,888.6 IU of vitamin D, 1,152.4 IU of vitamin E, and 250 mg of Rumensin (Elanco Animal Health, Greenfield, IN). 5 Based on tabular value (NRC, 2001). 26

40 27 Figure 5. Experimental layout and dietary treatments tested prepartum and postpartum. Two CS hybrids, BMR corn hybrid (Mycogen F2F569, Mycogen Seeds, Indianapolis, IN) and conventional corn (DeKalb DKC61-72, Monsanto Company, St. Louis, MO) were planted in spring 2012 at the Utah State University South Farm (Wellsville, UT). Corn crops were harvested at approximately 30% whole plant DM, using a pull-type harvester (model FP230, New Holland USA, New Holland, PA) equipped with a mechanical processor, and treated with a silage inoculant (Silage PT, Nurturite, Twin Falls, ID) at a rate of 112 g/t of fresh forage to enhance Lactobacillus fermentation. Silage hybrids were placed in bag silos (Ag/Bag International Ltd., Warrenton, OR) and ensiled for 120 d. Alfalfa was preserved as sun-cured hay and processed for approximately 15 min in a total mixed ration (TMR) wagon (model 455, Roto-Mix, Dodge City, KS). Cows were housed in individual tie stalls fitted with rubber mattresses,