POTASSIUM NUTRITION: COW REQUIREMENTS AND WHOLE FARM BALANCE

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1 POTASSIUM NUTRITION: COW REQUIREMENTS AND WHOLE FARM BALANCE Joe Harrison, Tamilee Nennich, Ron Kincaid, and Lynn VanWieringen Washington State University Introduction This paper summarizes information on potassium (K) related to the concept of whole farm nutrient alance, K alance in the lactating dairy cow, and the role of K feeding and optimum DCAD in the lactating diet. Although K is not perceived to cause environmental concerns, when excess K is imported to the farm, high K levels in forages can result. An awareness of whole farm alance and the K needs of the early lactation dairy cow provide a asis to make sound management decisions for K nutrition and nutrient management. Whole farm import of nutrients Figure 1 depicts the concept of whole farm nutrient management. Ideally the goal is for the input to equal the output from the farm. This is rarely the case ecause only ~ 13 to 27 % of feed input of N, P, and K are exported in milk and animals (Figure 2). The remainder of the N, P, and K are excreted. The import/export imalance is further impacted y the increase in cow density at the farmstead. From 1954 to 1987 there was a continual increase in cow density on dairy farms across the US (Lanyon, 1992). Coincident with this increase in cows per acre was an increased importation of feedstuffs to the farm to achieve higher levels of milk production. Data shown in Tale 1 indicate that the amount of concentrate (assumed to e imported) fed on dairy farms increased 10 to 50 fold etween 1954 and Potassium an essential nutrient for plants and animals Plants. Although K is a required nutrient for the physiological activity of grasses, grasses take up more K than needed (luxury consumption) for maximal yield (Blaser and Kimrough, 1968; James et. al., 1975). Figure 3 represents the yield of orchardgrass as related to various soil levels of potassium. The zone of maximal yield is suggested to e aout 80 ppm of soil K with plant K levels of approximately 2.5%. Orchardgrass can remove K from the upper soil profile (35- to 45-cm thickness) to a greater extent than alfalfa (Figure 4). Of particular note is that grasses can attain K levels of 6.0% dry matter when grown on soils that are high in availale K (Fisher et. al., 1994; MacLeod, 1965). The maturity or stage of development of grasses also affects the concentration of potassium. When leaf lades of perennial ryegrass were evaluated for mineral content at five developmental stages from unemerged to dead, K levels declined from approximately 3% to 1% or less (Wilman et al., 1994). The decline to levels of 1% or less occurred in plant material that was dead, while living plant tissue was relatively stale with levels around 3%. Other work (Blaser and Kimrough, 1968) suggests a more progressive decline in grass (romegrass) K with increasing maturation, particularly when grown in comination with alfalfa. Nitrogen fertilization increases total uptake of K y grasses as a result of increased yield of iomass (MacLeod, 1965). While total K uptake was increased in orchardgrass as the rate of N fertilization increased from 0 to 200 l/acre, the relative concentration of K declined (range of 12% to 75%) at each level of K fertilization (Figure 5). Animals. Potassium is the principal intracellular cation of most ody tissues. Potassium ions participate in many essential iological processes such as the maintenance of osmotic potential within cells, nerve impulse transmission, enzyme reactions in cellular metaolism, cardiac, skeletal and smooth muscle function, and the maintenance of normal kidney function. Because milk is an intracellular fluid, milk contains a large amount of K. Potassium use y the lactating dairy cow Potassium retention and excretion, along with the effect of K on milk production, were evaluated using a comination of data from various total collection metaolism trials conducted at Washington State University. There were 9 feeding trials included in the original dataset. However, one study with early lactation cows (AjWP2 study) averaged 36 DIM, and was different from the remainder of the data in that all of the cows in this data set had negative K retentions. Other early lactation cows (21 to 61 DIM, n = 9) in the dataset, with one exception, had positive K retentions, averaging 48.7 g/d. Milk production for cows in the caliration dataset ranged from 3.8 to 45.0 kg/d whereas milk production in the AjWP2 study ranged from 48.2 to 86.1 kg/day. The AjWP2 cows were the only animals in the dataset that produced more than 45 kg of milk/d. Due to the differences in the AjWP2 study, 2004 Penn State Dairy Cattle Nutrition Workshop 17

2 cows in this study were removed from the dataset used for development of the regression equations. Descriptive values for the cows in the caliration dataset are included in Tale 2. Potassium retention. Potassium retention in this data set was positive for over 85% of cows in the caliration dataset, and was negative for all early lactation cows in the AjWP2 study. Early lactation cows (less than 75 DIM) had an average K retention of 66 g/d (Figure 6). In most cases, the K retention was aove 20 g/d, with an average of 35 g/d. A value of 1.5 g K/kg milk was used to calculate the secretion of K in milk (NRC, 2001). However, previous studies indicate that the concentration of K in milk may e increased in some feeding situations (Sanchez et al., 1997). Therefore, it is possile that K secretion in milk was increased in these cows, and they were therefore retaining lesser amounts of K than indicated in this dataset. Equations developed for prediction of K retention indicate that K intake is a significant predictor of K retention (Equations 1 and 2). In this dataset, milk production, dry matter intake (DMI) and milk protein were significant independent variales and were important in determining K retention. (1) K retention (g/d) = K intake (g/d) * 0.29 Milk protein (g/g) * Milk (kg/d) * DMI (kg/d) * Residual SE = (2) K retention (g/d) = K intake (g/d) * Residual SE = Inter-study SE = Potassium excretion. Excretion of K is directly related to K intake. Figure 7 shows the relationship of K intake and K excretion. As expected, an increase in K intake led to an increase in excreted K (Equation 3). The addition of days in milk to the equation improved the residual SE y 6% (Equation 4). When the caliration dataset was compared to cows in the early lactation dataset, cows in the caliration dataset excreted less K than early lactation cows (Figure 7). (3) K excretion (g/d) = K intake (g/d) * Residual SE = Inter-study SE = (4) K excretion (g/d) = K intake (g/d) * DIM (days) * Residual SE = Inter-study SE = Early lactation cows. Potassium metaolism of cows in the early lactation dataset varied from cows in the caliration dataset. Early lactation cows tended to excrete greater amounts of K even though K intakes were similar to cows in the caliration dataset (Figure 7). Due to the greater K excretion and the greater secretion of K in milk, early lactation cows were in a negative K alance. Silanikove et al. (1997) found that cows in early lactation are often in a negative K alance and suggested that increased amounts of K in the diet may e eneficial to milk production. Figure 8 shows the relationship of K intake to milk production for early lactation cows in the AjWP2 study. For these early lactation cows, there was a positive relationship etween K intake and milk production. The cows in the early lactation dataset tended to have greater DMI and K intake as DIM increased. Similarly, K excretion was also greater as K intake and DIM increased. High levels of K feeding. Fisher et al. (1994) reported that DM intake was improved and milk production unchanged when dietary K increased from 1.6% to 3.1% of diet dry matter. A further increase of the K level to 4.6% of diet dry matter decreased feed intake and milk yield. As the level of K in the diet increased, animals drank more water, and excreted more urine, K, and sodium (Na). Interference in asorption of magnesium (Mg) with high levels of K feeding was evident. The ideal dietary concentration of K for high producing cows is etween 1.6% and 3.1%. Cows were physiologically challenged when fed levels of potassium from 3.1 to 4.6% of diet dry matter. Effect of additional K on Mg asorption. As indicated aove, added dietary K will reduce the asorption of dietary Mg. When feeding high levels of dietary K optimal levels of dietary Mg appear to e in the 0.35 to 0.38% of diet DM range. Another rule of thum is to maintain less than a 5:1 ratio of dietary K to Mg (the ratio is calculated with minerals on a percent of diet DM asis) Penn State Dairy Cattle Nutrition Workshop

3 Potassium s role in milk production can e tied to the concept of dietary cation anion difference (DCAD). Potassium is a cation that raises the DCAD, which represents interaction among the macrominerals. Interacting effects among the macrominerals Na, K, chloride (Cl), and sulfur (S) have een oserved in the pre-calving cow, ut little has een written on this suject for the postcalving cow. For a general review and roader examination of these and other related topics please see the review y Block (1994). DCAD affects the cow y altering its acid-ase status. Only a rief review of acid-ase status and DCAD are presented here. The numer of cation and anion charges asored into the lood ultimately determines the concentration of oth lood ph and the primary lood uffer, icaronate (HCO 3- ). If more anions than cations enter the lood from the digestive tract, lood ph will decrease and lood HCO 3 - will increase. Mongin (1980) proposed that the sum of Na plus K minus Cl in milliequivalents (meq) per 100 g diet dry matter could e used to predict net acid intake. This sum commonly is the dietary cationanion alance (Tucker et al., 1988) or dietary electrolyte alance (West et al., 1991). Sanchez and Beede (1991) coined the term cation-anion difference to represent, more precisely, the mathematical calculation used and to avoid the erroneous conclusion that mineral cations truly are alanced with mineral anions in the diet. Research on DCAD for lactating dairy cows Recently, there has een a lot of research on DCAD for lactating cows. Both a three-element (Na+K-Cl) and a four-element (Na+K-Cl-S) equation have een researched. A summary of this information is presented in Figures 9 and 10 and Tale 3. Differences etween K and Na as the source of increased DCAD. There are differences in the response to DCAD that depend on the source of Na and K used in these studies. This difference appears to show up mainly in cows in the early lactation period. Perhaps the most complete study on the effects of Na, K, and DCAD on early lactation dairy cows was y Elliot Block and associates from McGill University, Queec (E. Block, personal communication, 1999). They fed a control diet with no added Na or K (+18 DCAD) and two higher (+25 and +52) DCAD diets to early lactation Holstein cows (0 10 weeks in milk). Within the higher DCAD diets they manipulated the source of DCAD (y using either sodium icaronate or potassium caronate alone or a comination of oth) to determine the individual or comined effects of Na and K. Block and associates determined that the comination of Na and K yielded the est response in DMI and milk production and that the +52 DCAD diet yielded the highest milk production response (Figure 11). The cominations of Na and K also resulted in the highest lood icaronate concentrations (Figure 11). The aove positive responses oserved with cominations of Na and K point to the unique role that dietary K plays in early lactation. A similar role has een noted for cows in heat stress. Heat stressed cows lose K via sweat and milk is high in K. Thus the heat stressed dairy cow is often K deficient. Research conducted y Joe West in Texas, and Griffel and Sanchez in Idaho in which potassium caronate was the source of dietary K, indicates that there is a linear response in milk production to up to 2.1% dietary K during the summer in Texas and Idaho (West et al., 1986, West et al., 1987a,, Griffel et al., 1997). Figure 12 shows the fat-corrected milk responses to varying dietary K in oth mid and early lactation. Notes There are three reasons that guidelines for Na and K are higher than NRC (2001). First, ecause early lactation cows eat less than mid-lactation cows, there is a need to increase nutrient concentrations to reflect reduced feed intakes. Second, most of the macromineral research was conducted with low and medium producing cows; high producing cows secrete more of these minerals in milk and generate more acid in the rumen and lood. Third, the higher concentrations of Na and K represent an additional role these nutrients play in rumen uffering and acid-ase alance, and recent data suggests that cows can e deficient in K and Na in early lactation. No recommendation is given for sodium (Na) ecause of its dependency on K and DCAD concentrations. Salt per se is not a required nutrient y dairy cows. However, ecause salt is one of the four taste sensors on the tongue, we recommend a minimum of salt (~ 0.1 l) in every lactation ration. Chloride should e kept to as low as the NRC minimum as possile to avoid complications due to chloride s contriution in suclinical metaolic acidosis. When dietary K is high, magnesium (Mg) also should e increased to maintain a K:Mg ratio of approximately 4:1 to 5:1 (%:%). Potassium caronate can e reactive in certain ration environments, causing ration heating and feed mixing challenges. DCAD Plus Feed Grade Potassium Caronate 2004 Penn State Dairy Cattle Nutrition Workshop 19

4 goes through a patented production process to reduce the risk of heating and improve mixing so it is the safest choice for increasing K in the diets of lactating dairy cows. Pre-partum cows and DCAD High levels of K in forages create a challenge for the dairy cow, particularly in the late pre-partum period (Fisher et al., 1994). During the dry period, the K requirement is 0.65% DM. When grass silage high in K (4.0 to 6.0% DM) makes up a major portion of the diet, potassium intake generally exceeds the recommended level. Potassium levels in pre-partum diets should e low and need to e monitored to avoid metaolic prolems around calving. Many dairy cows have low lood calcium (hypocalcemia) at calving, although not low enough to show classical signs of milk fever (Sanchez and Blauwiekel, 1994). Clinical milk fever has een associated with increased incidence of dystocia, retained placenta, and displaced aomasum (Sanchez and Blauwiekel, 1994). In addition to the K content of the ration, the most current and widely adopted nutritional strategy to avoid clinical and suclinical milk fever in dairy cows is to alance the diet of the pre-partum cow (3 weeks efore calving) to have a negative alance of cations (Na and K) and anions (Cl and S). High levels of K in the forage (grass silage) portion of the diet make it difficult to achieve the desired levels of a negative cationanion alance due to the contriution that potassium makes to the cation side. As a result, anionic salts such as ammonium sulfate, calcium sulfate, magnesium sulfate, ammonia chloride, calcium chloride, and magnesium chloride need to e added to the ration to lower the cation-anion alance. The annual economic loss due to fresh cow disorders has een estimated to e $383 per 100 cows (Schoonmaker, 2000). Dietary K and whole farm nutrient management Any program that increases the amount of K fed to cows must consider the overall effect of K on the dairy ecause feeding extra K to pre-calving dry cows can contriute to milk fever prolems. Therefore, a nutrient management plan that considers K in oth the manure and purchased fertilizer is needed to avoid growing forages with excessively high K. We are aware of two whole-farm case histories that have evaluated K alance. These examples help illustrate the importance of nutrient management plans to control excess K in soils and harvested forages. In the first case, the Cornell University Dairy Farm monitored N, P, and K alances over 25 years (Wang et al., 1999). Tale 4 provides the details of the mass alance of K in 1979 and Feed imports of K increased greatly; however, ecause fertilizer sources of K were drastically reduced and the amount of K captured in milk increased, the net alance of K on the farm was reduced y 30%. The second case history comes from the Washington State University Dairy at Buckley. At the dairy we noticed K concentrations in the grass forage were as high as 6%. Therefore, we eliminated K in the purchased fertilizer (manure was still applied to fields and supplied K). After a three-year period, the K concentrations in the grass forage returned to normal. Based on soil samples taken three years later, purchased K in the fertilizer was reintroduced ut at a reduced level. Summary Take the opportunity to understand the K nutrient management and nutrition at the whole farm and cow level as it can provide the opportunity for reduced costs of production and healthier and more productive cows. References Blaser, R. E., and E. L. Kimrough Potassium nutrition of forage crops with perennials. Am. Soc. Agron., Crop Sci. Soc., and Soil Sci. Soc. Am. pp Block, E Manipulation of dietary cation-anion difference on nutritionally related production diseases, productivity, and metaolic responses of dairy cows. J Dairy Sci. 77:1437 Delaquis, A. M., and E. Block Dietary cation-anion difference, acid-ase status, mineral metaolism, renal function, and milk production of lactating cows. J. Dairy Sci. 78:2259 Fisher, L. J., N. Dinn, R. M. Tait, and J. A. Shelford Effect of level of dietary potassium on the asorption and excretion of calcium and magnesium y lactating cows. Can. J. Anim. Sci. 74:503. Griffel, L. A., W. K. Sanchez, R. C. Bull, R. F. Rynk, M. A. Guy, and B. A. Swanson Effects of dietary protein and sodium or potassium uffers during summer on lactational performance, acid-ase status and nitrogen metaolism of dairy cows. J. Dairy Sci. 80(Suppl. 1):241. Hart, J., M. Gangwer, M. Graham, and E. Marx Dairy manure as a fertilizer source. EM Oregon State Univ. Ext. Serv. James, D. W., W. H. Weaver, S. Roerts, and A. H. Hunter Potassium in an arid loessial soil: changes in availaility as related to cropping and fertilization. Soil Sci. Soc. Am. Proc. 39: Lanyon, L Implications of dairy herd size for farm material transport, plant nutrient management, and water quality. J Dairy Sci. 75: Penn State Dairy Cattle Nutrition Workshop

5 MacLeod, L. B., Effect of nitrogen and potassium on the yield and chemical composition of alfalfa, romegrass, orchardgrass, and timothy grown as pure species. Agron. J. 57: Mongin, P Electrolytes in nutrition: review of asic principles and practical application in poultry and swine. In Third Ann. Int. Mineral Conf. Orlando, FL. Page.1. National Research Council Nutrient requirements of dairy cattle. 7 th rev. ed. Natl. Acad. Sci., Washington, DC. Nelson, C. J Managing nutrients across regions of the United States. J Dairy Sci. (suppl 2): Sanchez, W. K., and R. Blauwiekel Prevention of milk fever y application of the dietary cation-anion alance concept. EB Washington State Univ. Coop. Ext., Pullman. Sanchez, W. K., and D. K. Beede Interactions of sodium, potassium, and chloride on lactation, acid-ase status, and mineral concentrations. J. Dairy Sci. 77:1661. Sanchez, W. K., D. K. Beede, and J. A. Cornell Dietary mixtures of sodium icaronate, sodium chloride, and potassium chloride: effects on lactational performance, acid-ase status, and mineral metaolism of Holstein cows. J. Dairy Sci. 80: Sanchez, W. K Another new look at DCAD for postpartum dairy cows. Proc. Mid-South Ruminant Nutrition Conf. pp Texas Animal Nutrition Council. Sanchez, W. K. and D. K. Beede Interrelationships of dietary Na, K and Cl and cation-anion difference in lactation rations. In Proc. Florida Rum. Nutr. Conf. Univ. Florida, Gainesville. Page 31. Schoonmaker, K Fresh-cow prolems steal profits. Dairy Herd Management. August, pp Tucker, W. B., G. A. Harrison, and R.W. Hemken Influence of dietary cationanion alance on milk, lood, urine, and rumen fluid in lactating dairy cattle. J. Dairy Sci. 71:346. Wang, S. J., D. G. Fox, D. J. R. Chearney, S. D. Klausner, and D. R. Bouldin Impact of dairy farming on well water nitrate level and soil content of phosphorus and potassium. J. Dairy Sci. 82:2164. West, J. W., B. G. Mullinix, and T. G. Sandifer Changing dietary electrolyte alance for dairy cows in cool and hot environments. J. Dairy Sci. 74:1662. West, J. W., C. E. Coppock, D. H. Nave, and G. T. Schelling Effects of potassium uffers on feed intake in lactating dairy cows and on rumen fermentation in vivo and in vitro. J. Dairy Sci. 69:124. West, J. W., C. E. Coppock, D. H. Nave, J. M. Laore, and L. W. Greene. 1987a. Effects of potassium caronate and sodium icaronate on rumen function in lactating Holstein cows. J. Dairy Sci. 70:81. West, J. W., C. E. Coppock, K. Z. Milam, D. H. Nave, and J. M. Laore Potassium caronate as a potassium source and dietary uffer for lactating cows during hot weather. J. Dairy Sci. 70:309. West, J. W., K. D. Haydon, B. G. Mullinix, and T. G. Sandifer Dietary cation-anion alance and cation source effects on production and acid-ase status of heat-stressed cows. J. Dairy Sci. 75:2776. Wildman, C. D., J. W. West, and J. K. Bernard Dietary cation-anion difference and K:Na Wilman, D., G. H. Acuna P, and P. J. Michaud Concentrations of N, P, K, Ca, Mg, and Na in perennial ryegrass and white clover leaves of different ages. Grass Forage Sci. 49: Penn State Dairy Cattle Nutrition Workshop 21

6 Tale 1. Changes in dairy farm numers, cow numers, and the concentrate consumed for three US dairy states from 1954 to Source: Lanyon (1992). California No. dairy farms 34,031 3,631 Milk cows 790,730 1,070,366 Concentrate use l/yr per cow 1,899 7,542 l/100 l milk l/yr per farm 43,747 2,223,069 Florida No. dairy farms 16,738 1,073 Milk cows 158, ,993 Concentrate use l/yr per cow 3,216 9,469 l/100 l milk l/yr per farm 30,523 1,562,323 Pennsylvania No. dairy farms 82,708 15,096 Milk cows 875, ,054 Concentrate use l/yr per cow 2,248 5,643 l/100 l milk l/yr per farm 23, ,123 Tale 2. Descriptive statistics for cows (including potassium intake, retention, and excretion) from the 8 feeding trials included in the caliration dataset. Item n Mean Std Dev Minimum Maximum DIM BW, kg DMI, kg Milk, kg Diet K, % DCAD, meq/100 g CAD, meq/100 g K intake, g K retention, g K excretion, g DCAD = [(Na + K) (Cl + S)] 2 CAD = [(Na + K) (Cl)] Penn State Dairy Cattle Nutrition Workshop

7 Tale 3. Summary of the effect of DCAD on milk production, feed intake and lood icaronate (HCO - 3 ) responses in studies using the [(Na + K) (Cl + S)] DCAD expression. DCAD Study Meq [(Na + K) - (Cl + Parameter Response S)]/ 100g diet DM Sanchez et al., Treatments 0 to + 50 Intake Milk Blood HCO 3 - Mid lactation + 25 Max + 31 Max + 38 Max Delaquis and Block, 1995 Delaquis and Block, 1995 Delaquis and Block, 1995 Block, Unpulished to Milk, Intake, - Blood HCO 3 Early lactation +14 to Milk, Intake Mid lactation +20 to Milk, Intake Late lactation +18 to +52 Milk, Intake, - Blood HCO 3 Early Lactation Positive Positive Not Significant Positive; Dependent on Source of DCAD Tale 4. Mass alance of K on the Cornell University Dairy Farm etween 1979 and 1999 (from Wang et al., 1999). Potassium (metric tonnes) Imports Feed Fertilizer Total Imports Exports Milk Animals Feed Refused Total Exports Balance Milk production increased from 6802 to 10,254 kg/cow/year and cow numers increased from 369 to 400 etween 1979 and Penn State Dairy Cattle Nutrition Workshop 23

8 Figure 1. Schematic depicting the concept of whole farm nutrient management. Ideally, inputs = outputs. Source: Nelson (1999). Figure 2. Fate of nutrients in feed. Source: Hart et al. (1996) Penn State Dairy Cattle Nutrition Workshop

9 3 Figure 3. The yield (16% moisture) and K content of uninterrupted orchardgrass growth as influenced y K fertilization. Data from Blaser et al. (1958). Source: Blaser and Kimrough (1968). Figure 4. Trends in soil test K values with time when orchardgrass and alfalfa were grown in soils with different initial values. Source: James et al. (1975) Penn State Dairy Cattle Nutrition Workshop 25

10 Concentration of potassium in orchardgrass, gm kg kg Ha -1 K 112 kg Ha -1 K 56 kg Ha -1 K Rate of nitrogen applied, kg Ha -1 0 K Figure 5. Effect of application of nitrogen and potassium on the concentration of potassium in orchardgrass. Rates of nitrogen application were 0, 28, 56, 112, and 224 kg Ha -1 (adapted from MacLeod, 1965) Apparent K retention, g/d <75 76 to to 225 > Days in milk Figure 6. Apparent potassium retention of lactating cows at various days in milk Penn State Dairy Cattle Nutrition Workshop

11 Trial adjusted K excretion, g/d y = x R 2 = y = x R 2 = Caliration dataset Early lactation dataset K intake, g/d Figure 7. The relationship of potassium intake and potassium excretion for cows in the caliration and early lactation datasets y = x R 2 = Milk, kg/d K intake, g/d Figure 8. Potassium intake compared to milk production for early lactation cows in the AjWP2 study Penn State Dairy Cattle Nutrition Workshop 27

12 kg/day Effect of Na + K - Cl (DCAD) on Dry Matter Intake (Midlactation Cows) DCAD [meq (Na + K - Cl)/100 g DM] Tucker, 88 West, 91 West, 92 Comined kg/day Effect of Na + K - Cl (DCAD) on Blood Bicaronate (Midlactation Cows) DCAD [meq (Na + K - Cl)/100 g DM] Tucker, 88 West, 91 West, 92 Comined kg/day Effect of Na + K - Cl (DCAD) on Milk Yield (Midlactation Cows) DCAD [meq (Na + K - Cl)/100 g DM] Tucker, 88 West, 91 West, 92 Comined Figure 9. Summary of the effect of DCAD on dry matter intake, lood icaronate, and milk yield using the (Na + K Cl) DCAD expression (data are from Tucker et al., 1988; West et al., 1991; and West et al.,1992) Penn State Dairy Cattle Nutrition Workshop

13 DMI, kg/d DCAD, meq(na+k-cl-s)/100g DM Milk Yield, kg/d DCAD, meq(na+k-cl-s)/100g DM Blood HCO 3, meq/l DCAD, meq(na+k-cl-s)/100g DM Figure 10. Dry matter intake, milk yield, and lood icaronate response to (DCAD [(Na + K) (Cl + S)]/100g DM) in mid lactation cows. Data are from Sanchez et al., 1994 (treatments circled are from a low Cl, high K, and high Na treatment comination that may have caused a Cl deficiency) Penn State Dairy Cattle Nutrition Workshop 29

14 DMI, kg/d Dry Matter Intake vs. DCAD in Early Lactation a 20.5 a 22.7 a a 21.9 a Control 25.2 Na 25.2 K 25.2 Na+K 52 Na 52 K 52 Na+K DCAD, (meq(na+k-cl-s)/100g) and Source Milk Yield, kg/d Milk Yield vs.dcad in Early Lactation a Control 25.2 Na 25.2 K 25.2 Na+K 52 Na 52 K 52 Na+K DCAD, (meq(na+k-cl-s)/100g) and Source meq/l DCAD vs. Blood Bicaronate in Early Lactation a a a a a Control 25.2 Na 25.2 K 25.2 Na+K 52 Na 52 K 52 Na+K DCAD, (meq(na+k-cl-s)/100g) and Source Figure 11. Dry matter intake, milk yield, and lood icaronate responses to (DCAD [(Na + K) (Cl + S)]/100g DM) in early lactation cows. Data are from Elliot Block, McGill University (1999, unpulished data). Block evaluated oth DCAD concentration and source (Na, K or a comination of oth) in ten early lactation cows (weeks 1 to 10 in milk) per treatment. Different superscripts indicate a statistical difference (a = P < 0.05; = P < 0.01) etween treatment and control Penn State Dairy Cattle Nutrition Workshop

15 3.5% FCM Response to Potassium Caronate in Early and Midlactation l/day y = 5.8x y = 8.8x y = 4.0x y = x x Dietary Potassium, % DM West et al., Midlactation Griffel et al., Early Lactation Block et al., Early Lactation Fisher et al., Early Lactation Figure 12. Fat-corrected milk (3.5% FCM) response to feeding various potassium concentrations (as potassium caronate) to heat stressed, mid lactation dairy cows (West et al., 1986; West et al., 1987a, ), heat stressed, early lactation cows (Griffel et al., 1997), and non-heat stressed, early lactation cows (Block et al., 1999; Fisher et al., 1994) Penn State Dairy Cattle Nutrition Workshop 31