Using dietary crude protein to manipulate energy balance in early lactation dairy cows S.J. Whelan 1,3, F.J. Mulligan 2 B. Flynn 3, J.J. Callan 3 and K.M. Pierce 1 1 School of Agriculture and Food Science and 2 School of Veterinary Medicine University College Dublin, Belfield, Dublin 4 3 UCD Lyons Research farm, Newcastle, Dublin, Ireland
Introduction Dairy production in Ireland Nutritional issues of the early lactation dairy cow Recent energy balance experiments conducted at UCD Effect of supplementary concentrate type on energy balance in the early lactation, pasture fed dairy cow Effect of dietary CP and starch content on energy balance in early lactation dairy cows Conclusions Overview of Presentation
Dairy Production in Ireland Largely seasonal production system 1.1 million dairy cows 5,000 kg average milk production Contributes 2.7 billion to Irish exports However, still room for improvement Replacement rate is 25% 15% are replaced due to infertility Calving interval is 394 days
Nutritional issues of the early lactation dairy cow Early lactation is a challenging period for the dairy cow Important to explore dietary strategies that reduce these challenges Optimising DMI is important in improving energy balance Moderating milk yield through dietary CP may also improve energy balance
Manipulating CP intake in the pasture fed early lactation dairy cow
Basis for Experiment Pasture is the most abundant forage source available to Irish dairy farmers However Chemical composition of grass can vary considerably This flux in nutrient supply may be detrimental to the animals health Therefore Concentrate supplementation is often required, but Concentrate type will be important
Materials and Methods Randomised block design Day 1 until day 100 postpartum 11 animals per dietary treatment Balanced for parity, milk yield, constituent yield and calving date Blood samples harvested on weeks 2 through to 5 postpartum Milk samples taken weekly Energy balance determined during week 6 post partum
Concentrate Treatments Supplements were fed twice daily during milking (6kg total) 4 supplementary concentrate treatments HP(180g CP kg -1, rolled barley) LP(140g CP kg -1, rolled barley) LP+ HMBi (140g CP kg -1, rolled barley + supplementary methionine (HMBi)) LP Corn (140g CP kg -1, ground maize grain)
Chemical Composition of diets offered HP LP LP+HMBi LP Maize Pasture DM (g kg -1 ) 867 858 862 859 207 Energy (UFL) 1.12 1.10 1.10 1.14 0.98 Crude protein 192 150 150 150 170 PDIA 72 52 52 74 39 PDIN 145 108 108 122 107 PDIE 139 120 120 133 98 NDF 219 218 222 223 438 ADF 91 106 111 115 219 ADL 7 10 12 7 63 Ash 87 81 80 79 73 Starch 296 303 307 344 -
Results
Pasture DMI (kg d -1 ) Pasture Dry Matter Intake 16 14 n.s. 12 10 8 6 4 2 0 Concentrate Type HP LP LP+HMBi LP Maize
Milk Yield kg d -1 34 32 30 28 26 24 22 20 18 16 HP vs. LP (P < 0.05) Week (P < 0.01) Week x Trt. (P < 0.05) Weekly Milk Yield 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Week Postpartum HP LP LP+ HMBi LP Maize
Intake(UFL d -1 ) Energy Intake 20 18 16 14 12 10 8 6 4 2 0 ns Concentrate Type HP LP LP+ HMBi LP Maize
ECM (kg d -1 ) Energy Corrected Milk 40 35 30 ab b a ab 25 20 15 10 5 0 Concentrate Type HP LP LP+ HMBi LP Maize a vs. b, P < 0.05
Energy Balance (UFL d -1 ) Energy Balance 0.6 0.4 0.2 0-0.2-0.4-0.6-0.8 ns Concentrate Type HP LP LP+HMBi LP Maize
Blood Metabolites
Blood Urea N (mmol L -1 ) Blood Urea Nitrogen 7 6 a 5 b b b 4 3 2 1 0 Concentrate Type HP LP LP+ HMBi LP Maize
βhba (mmol L -1 ) Beta Hydroxy Butyric Acid 0.8 a 0.7 0.6 b b b 0.5 0.4 0.3 0.2 0.1 0 Concentrate Type HP LP LP+ HMBi LP Maize a vs. b (P < 0.05)
NEFA (mmol L -1 ) Non Esterified Fatty Acids 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 a ab b ab Concentrate Type HP LP LP+ HMBi LP Maize a vs. b (P < 0.05)
Glucose (mmol L -1 ) Glucose 4 3.5 3 2.5 2 1.5 1 0.5 b b ab a 0 Concentrate Type HP LP LP+ HMBi LP Maize a vs. b (P < 0.05)
Conclusions Milk yield was reduced where LP was offered. However ECM was not different Lower BHBA and blood urea N indicated a more favourable metabolic status where low CP concentrates were offered The use of maize grain or supplementary methionine in low CP concentrates improved milk production without impacting on metabolic status
Dietary manipulation of crude protein and starch content affects energy balance in early lactation dairy cows
Basis for Experiment Early lactation is a challenging period for the dairy cow Reducing dietary CP intake can improve EB Similarly providing glucogenic diets can improve the metabolic status of the diary cow However, the simultaneous application of these strategies has not been tested to date
Materials and Methods Randomised block design Day 1 until day 63 postpartum 10 animals per dietary treatment Balanced for milk yield, constituent yield and calving date Blood samples harvested on days 0, 7, 14, 21, 28, 35 and 63 Milk samples taken weekly Post experiment All animals offered a pasture based diet
Dietary Treatments Diets were offered once daily as a TMR 1. High CP low starch TMR (HP-LS) 15% CP 6% Starch 2. Low CP high starch TMR (LP-HS) 12% CP 28% Starch Diets were iso-energetic (1.05 UFL/ kg DM)
Chemical Composition of diets offered HP-LS LP-HS Composition (% unless stated) DM 29.3 37.3 UFL/ kg DM 1.05 1.05 CP 14.6 11.9 NDF 54.5 39.3 PDIA 4.0 3.8 PDIN 8.9 7.8 PDIE 9.4 9.3 ADF 35.1 25.3 ADL 4.1 2.9 NDF for. 32.2 27.4 Ash 7.5 5.7 Starch 5.7 27.5
Results
Intake (kg DM d -1 ) Dry Matter Intake over the Duration of the Experiment 22 20 18 16 14 12 10 1 2 3 4 5 6 7 8 9 Week of Lactation Diet P = 0.25 HP-LS LP-HS Week P < 0.01 Diet x Week P = 0.17
Milk Yield (kg/ d) Daily Milk Yield for the Experiment 34 32 30 28 26 24 22 20 P < 0.01 Diet HP-LS LP-HS
Milk Constituent Yield (kg/ d) Milk Constituent Yield 1.4 1.2 1 0.8 0.6 0.4 0.2 0 P < 0.01 P < 0.01 P < 0.01 Fat Protein Casein HP-LS LP-HS
Milk Yield (kg d -1 ) 305d Lactation Yield 8000 7000 6000 HP-LS LP-HS 5000 Fat (Kg) 349 P = 0.99 334 4000 Protein (Kg) 255 261 3000 2000 1000 0 Diet HP-LS LP-HS
Energy Balance (UFL/ d) Energy Balance over the Duration of the Experiment 4 3 2 1 0-1 -2-3 -4 1 2 3 4 5 6 7 8 9 Week of Lactation HP-LS LP-HS Diet P = 0.02 Week P < 0.01 Diet x Week P = 0.75
BCS Units BCS at Calving and Day 63 3.6 3.2 2.8 2.4 2 1.6 1.2 0.8 0.4 0 P = 0.47 BCS at Calving HP-LS Loss = 0.2 BCS P = 0.36 BCS at d63 LP-HS
Blood Metabolites
BHBA (mmol/ L) Beta Hydroxy Butyric Acid 0.9 0.8 0.7 0.6 0.5 0.4 0.3 P = 0.03 0.2 0.1 0 HP-LS Diet LP-HS
NEFA (mmol/ L) Non Esterified Fatty Acids 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 P = 0.54 0.1 0.05 0 HP-LS Diet LP-HS
Glucose (mmol/ L) Glucose 3.5 3 2.5 2 1.5 P = 0.36 1 0.5 0 HP-LS Diet LP-HS
Conclusions Offering early lactation dairy cow a low CP, high starch diet improves energy balance Reductions in milk yield observed during early lactation did not affect 305 d lactation yields Blood metabolites did not indicate a severe metabolic challenge in this experiment
Overall Conclusions Regardless of production system, the maintenance of DMI is key in maintaining a more positive energy balance Reducing CP intake moderates milk production and reduces the urea burden on the animal, thus reducing energy demands Further work is required in pasture based production systems to determine the extent to which CP can be reduced Work is also required to determine the lifetime effects of these strategies on the survival of the dairy cow
Acknowledgements This research was funded under the National Development Plan through the Research Stimulus Fund administered by the Irish Department of Agriculture, food and Marine Additionally I would like to acknowledge the assistance of the farm and laboratory staff at UCD Lyons Research Farm
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