Holstein Cows In Early Lactation Research Articles

Effect of Canola Fat on Ruminal and Total Tract Digestion, Plasma Hormones, and Metabolites in Lactating Dairy Cows

The effects of canola fat on digestion and metabolism were investigated by incorporating 0, 4.5, 9, 13.2, or 17.4% Jet-Sploded® canola seed into a diet containing a 60:40 (DM) concentrate:forage ratio. The diets contained 16.5% CP, 30% alfalfa silage, and 10% whole-crop oat silage on a DM basis and were fed for ad libitum consumption as TMR to 10 ruminally cannulated Holstein cows in early lactation. Jet-Sploded® canola seed supplementation did not change ruminal pH or NH3 N concentrations, but VFA concentrations declined with increasing level of inclusion. Apparent digestibilities of DM, OM, CP, NDF, and ADF were unaffected by level of inclusion of Jet-Sploded® canola seed, but ether extract digestibility declined linearly, which resulted in similar ether extract absorption across the three diets supplemented with canola fat. Based on in sacco data, the percentages of ruminal digestion of OM and CP declined with increasing inclusion of Jet-Sploded® canola seed. Plasma glucose and FFA concentrations tended to respond in a quadratic fashion, plasma insulin concentration declined linearly, and plasma glucagon and somatotropin concentrations were unaffected by dietary treatment. The results indicate that a positive productive response may be expected from dietary inclusion of about 5% Jet-Sploded® canola seed, but the benefits of increased energy density associated with higher inclusion levels may be offset by reduced availability of energy in the rumen and decreased fat digestibility postruminally. The substantial effects of time postfeeding on ruminal fermentation and on concentrations of plasma hormone and metabolites in animals fed TMR demonstrate that infrequent sampling can result in misleading results and, thus, invalid interpretation of the influence of dietary fat on these parameters.

Effect of Season, Genetic Line, and Sire on Growth Concentrations of Somatotropin in Serum of Holstein Cows in Early Lactation

To determine the effect of selection for milk yield on somatotropin concentrations, blood samples were collected from 128 Holstein cows whose sires had either high or average predicted differences for milk. The phenotypic difference in milk yield between the high and average yielding groups was 1726kg on a 305-d mature equivalent basis. At 37±7 d postpartum, four blood samples were taken from each cow at 1-h intervals beginning at 0800h. The statistical model contained genetic line, sires within line, and season as whole-plot effects and time of sampling as a subplot effect. The concentration of growth hormone was significantly higher in the high yielding group (1.89) than in the average yielding group (1.49). Cows sampled in summer had the highest concentrations of growth hormone, whereas cows sampled in spring had the lowest concentrations. Sires did not significantly influence the somatotropin concentration of their progeny. In a second analysis with seven extreme outliers (peak values) deleted, the variation of somatotropin concentrations in the cows was significantly accounted for by their sires. Repeatability of somatotropin concentration was .49 within cows.

The Effect of Protein Degradability on Milk Composition and Production of Early Lactation, Somatotropin-Injected Cows

Twenty multiparous Holstein cows in early lactation that received 500mg bST injected every 2 wk were assigned to one of two treatments to examine the influence of diets that varied in degradability of protein. Effects of degradability were determined on milk production and components and on nutrient digestibility. Treatments consisted of a basal ration (control) containing soybean meal as its primary degradable protein source and a ration (treatment) containing corn gluten and meat and bone meals as the primary undegradable protein source, representing 33% undegradable protein in CP.The undegradability of protein sources did not influence DMI and BW. Milk yield, 3.5% FCM, and production efficiency of bST-treated cows were not affected by increased undegradable protein in the diet. Milk fat and SNF were not significantly increased by treatment. Lactose was significantly higher for the control diet (5.0 vs. 4.9%) but was not biologically significant. Increasing undegradability of protein significantly increased total protein in milk and casein percentage in milk protein (3.14 vs. 2.86% and 62.11 vs. 58.24%, respectively). Total tract digestibility of nutrients was unaffected by treatment; however, CP digestibility tended to be higher as undegradability increased (67.85 vs. 62.83%).

Plasma growth hormone and insulin concentrations in, and free fatty acid release from adipose tissue cultured in vitro from Holstein cows of differing cow index during early and late lactation

Early (EL) and late (LL) lactation Holstein cows were segregated into three Cow Index (CI) groups (high, HG; medium, MG; low, LG; n=47). Feed intake by lactation group, individual milk yield data and blood samples, obtained by puncture of the coccygeal vein or artery at 12-hr intervals, were collected for 7 d. Cows were fed alfalfa hay top dressed with grain mixture. On day 7, 5 g of subcutaneous adipose tissue were removed from the tail-head region. Tissue was minced into 10–15 mg pieces in Krebs-Ringer bicarbonate buffer with 5 ng/ml insulin added (KRB). Triplicate 100-mg aliquots were incubated in KRB + 3% essentially fatty-acid-free bovine serum albumin with either 50 ng/ml growth hormone (G), 5 μg/ml epinephrine (EPI), both (G+E) or neither (CON) at 37 C for 2 hr. Early lactation cows averaged greater (P<.05) daily milk production (33.4 vs 22.1 kg), greater (P<.05) plasma growth hormone (GH) concentrations (3.9 vs 3.0 ng/ml) but lesser (P<.01) insulin (INS) concentrations (.49 vs .73 ng/ml) than LL cows. Adipose tissue FFA release in vitro was greater (P<.01) when media contained EPI (EPI: 8.10; G+E: 8.05 μE/l/g tissue) than when EPI was not present (CON: 1.33; G: 1.39 μE/l/g tissue), but was not affected by stage of lactation. Including hormonal data in the model as covariates indicated that increased plasma INS concentrations before biopsy reduced subsequent FFA release in vitro when tissue was incubated with added EPI, but not when incubation media lacked EPI. Increased GH concentrations had the opposite effect. Further, FFA release was greatest from HG cow adipose when incubated in media lacking EPI, but greatest from LG cow adipose when incubated in media containing EPI.

Effects of Feeding α-Tocopherol and Calcium Salts of Fatty Acids on Vitamin E and Fatty Acid Composition of Cow's Milk

Four experiments were carried out with Holstein cows in early lactation to assess the effect of feeding, 0, 50, and 400 IU of vitamin E/kg of DM on transfer of vitamin E to milk fat. The effects of adding 50g of calcium salts of fatty acids/kg of DM on DM intake, milk production, and milk quality also were studied. Feeding of 10g of vitamin E (dl-α-tocopheryl acetate) per cow daily for 4 wk prepartum and about 8g daily (400 IU/kg of dietary DM) for wk 1 to 8 of lactation maintained 40 to 54μg of vitamin E/g of milk fat. Transfer of vitamin E to milk in early lactation was impaired, and the causes for this are discussed. Feeding calcium salts of fatty acids had a tendency to reduce DM intake and decreased protein and lactose content of milk in one experiment. This treatment had little effect on fatty acid composition and vitamin E content of milk fat in early lactation, but after peak production it increased oleic and linoleic acids in milk fat.

Effect of dietary crude-protein type on fertilization and embryo quality in dairy cattle

Summary An experiment was conducted to determine whether balancing dietary crude protein for optimal rumen degradability would improve fertilization rate and quality of ova in lactating dairy cows. Thirty-eight Holstein cows in early lactation were fed 1 of 2 diets formulated to be isocaloric and isonitrogenous, containing 16% crude protein, Diet 1 contained 73% rumen degradable intake protein, whereas diet 2 contained 64% rumen degradable intake protein. The cows were induced to superovulate and were inseminated, and ova were recovered nonsurgically on postbreeding day 7. Ova were counted and classified as fertilized or unfertilized. Fertilized ova were scored as excellent, good, fair, poor, or degenerate. Unfertilized ova and poor and degenerate embryos were considered to be nontransferable ova and excellent, good, and fair embryos were considered to be transferable ova. There were no differences for mean number of fertilized, unfertilized, transferable, or nontransferable ova recovered from cows fed the 2 diets (P &gt; 0.10). Mean percentage of fertilized ova recovered from cows was greater (P &lt; 0.05) in those fed diet 2, compared with diet 1. Mean percentage of transferable ova recovered from cows tended to be greater (P = 0.06) in those fed diet 2, compared with diet 1. More cows failed to yield transferable ova (P &lt; 0.05) when fed diet 1, compared with diet 2. Fertilization failure or early degeneration of embryos may occur in cows fed excess rumen degradable protein.

Responses of Dairy Cows in Early Lactation to Bovine Somatotropin and Ruminally Inert Fat

Bovine somatotropin (0 or 41.2 mg/d bST) and calcium salts of long-chain fatty acids (0 or .77 kg/d Ca-LCFA) were administered to 16 Holstein cows in early lactation. Cows remained on 0 or 41.2 mg/d bST for the entire 10 wk and received 0 or .77 kg/d Ca-LCFA in one of two 5-wk periods. Production data were recorded daily, milk fatty acids, and blood metabolites were determined once each period. Treatments did not affect feed intake. Fat-corrected milk (kg/d) and percentage of milk fat for cows receiving no supplementation, fatty acids alone, bST alone, and fatty acids and bST together were 33.8, 3.2; 33.5, 3.1; 37.4, 3.4; and 40.8, 3.5. Milk fatty acids below C16 were reduced with either bST or dietary fatty acids; C16 fatty acids were lower with bST but higher with dietary fatty acids; C18:0 fatty acids were reduced with dietary fatty acids; and C18:1 fatty acids were higher with either bST or dietary fatty acids. Blood acetoacetate concentrations were higher with both bST and dietary fatty acids, β-hydroxybutyrate was not different, and FFA and insulin concentrations increased with bST. In this experiment, the energy supplied by Ca-LCFA acids enhanced the lactogenic effect of bST.

Effect of Rumen-Protected Methionine and Lysine on Casein in Milk When Diets High in Fat or Concentrate are Fed

To examine the effect of supplying methionine and lysine on milk N composition, isoenergetic, isonitrogenous diets containing 50:50 with 3,9% added fat or 25:75 forage to concentrate with no added fat were fed with or without rumen-protected methionine and lysine to four primiparous and four multiparous early lactation (36 d in milk) Holstein cows in two 4 x 4 Latin squares. Diets contained 1.7 Mcal NE1 and were fed for ad libitum intake. Periods were 21 d. Rumen-protected methionine and lysine increased total N and casein N percentage with the 3.9% fat, but did not increase total N and casein N percentage with the diet without fat. Whey N percentage was greater with the no fat than with the 3.9% fat diet. Whey N percentage was not affected by adding amino acids. Nonprotein N percentage was greater for the diet with the 3.9% fat than with no fat. Proportions of casein N or whey N to total N were unaffected by treatments. Adding methionine and lysine to diets did not increase yields of total N and casein N. The 3.9% fat diet increased proportions of long-chain (C18:0 and C18:0) and decreased proportions of short- to medium-chain fatty acids (C8 to C16) in milk fat. Plasma nonesterified fatty acids and triglyceride concentrations were greater with the 3.9% fat as compared to the no fat diet. Methionine and lysine decreased plasma triglyceride concentrations with the 3.9% fat diet. Milk yields, DM intakes, and plasma glucose concentrations were unaffected by treatment.

Sorghum grain for lactating dairy cows (1990)

Forty-seven Holstein cows in early lactation were utilized to evaluate the effects of supplementing concentrate diets of sorghum grain on milk production, milk composition, somatic cell count, and body condition. At 21 d postpartum, cows were randomly assigned to receive four concentrate diets consisting of 1) corn, 2) sorghum, 3) sorghum plus 1 lb tallow, and 4) sorghum plus wheat in a 70:30 ratio. All concentrates were combined with chopped alfalfa hay in a total mixed diet and fed twice daily. Treatments included a 7-day preliminary period and a 16-week experimental period.

Dietary Fat and Ruminally Protected Amino Acids for High Producing Dairy Cows

Eight early lactation Holstein cows, used in a replicated 4 × 4 Latin square design, were fed the following diets: control; control plus ruminally protected amino acids (15g methionine and 20g lysine); control plus added fat (.32kg 60: 40 animal and vegetable blend and .36kg of Ca salts of fatty acids); control plus ruminally protected amino acids plus added fat. The objective was to examine the effect of ruminally protected forms of lysine and methionine and dietary fat on milk yield and composition. Cows were fed for ad libitum consumption of total mixed diets consisting of 50% forage and 50% concentrate on a DM basis. Added fat increased milk, fat, and 4% FCM yield but decreased milk protein percentage. Ruminally protected amino acids increased milk protein percentage. The combined effect of fat and ruminally protected acids increased milk fat percentage and yield more than the sole addition of either supplement. Added fat increased the percentage and yield of long-chain fatty acids in milk. Plasma free fatty acids were also increased by fat addition. Adding ruminally protected amino acids to fat-supplemented diets may help alleviate the milk protein depression found with added fat.

Evaluation of High Oil Corn and Corn Silage for Lactating Cows

Forty multiparous Holstein cows in early lactation were used to compare their responses to high oil corn and corn silage with responses to control corn and corn silage. Treatments were total mixed diets containing: 1) 50% control concentrate, 50% control corn silage; 2) 50% high oil concentrate; 50% control corn silage; 3) 50% control concentrate, 50% high oil corn silage; and 4) 50% high oil concentrate, 50% high oil corn silage on a DM basis. Cows fed high oil corn had greater DM intake (21.9 vs. 19.6 kg/d) and ruminal acetate:propionate ratio (2.3 vs. 2.0) than animals fed control corn. Fiber digestibility and yield and composition of milk were similar among grain and silage types. Apparent digestibility of DM was lower for animals on high oil corn than for those fed control corn (69.7 vs. 73.3%). Apparent digestibility of ether extract was lower for animals consuming high oil corn silage than for those fed control corn silage (82.2 vs. 85.9%). De novo synthesized fatty acids in milk fat were reduced, but preformed fatty acids of dietary origin were increased on all diets. Efficiency of milk production was lower for diets containing high oil corn or corn silage. Postpartum body weight recovery was greater for cows fed high oil corn than cows fed control corn, indicating a more favorable energy status for these animals. High oil corn and corn silage allowed both high milk production and the deposition of body tissue.

Alkali-Treated Forage for Early Lactation Dairy Cows: Effect on Lactation Performance and Nutrient Digestibility

Our objective was to determine the effect of sodium hydroxide treatment (4g NaOH/100g forage DM) of an alfalfa-orchardgrass forage and its subsequent utilization by early lactation dairy cows. Forage was harvested as hay. Complete mixed diets consisted of 55% control or treated hay and 45% concentrate (DM basis) and were fed to eight early lactation Holstein cows in a crossover design. Chemical composition of hays and complete diets were similar. Intake of dry matter was greater when cows were fed treated hay (23.4 vs. 22.2 kg/d), as was milk yield (32.3 vs. 30.9 kg/d). Yield of 4% FCM, however, did not differ between diets (27.8 vs. 27.4 kg/d). Cows fed the treated hay diet had increased concentrations of total rumen volatile fatty acids and ruminal acetate, decreased ruminal isobutyrate concentration and pH, and increased apparent digestibility of NDF, ADF, hemicellulose, and lignin. Sodium hydroxide treatment also increased the proportion of potentially digestible DM and NDF compared with that of untreated forage. Alkali treatment improved the utilization of medium quality forage in the early lactation dairy cow.

Effect of Added Dietary Fat and Bovine Somatotropin on the Performance and Metabolism of Lactating Dairy Cows

Four early lactation Holstein cows (44 to 105 d postpartum) were used in a 4×4 Latin square experiment in a 2×2 factorial arrangement of treatments to study effects of added dietary fat and/or bovine somatotropin on performance and metabolism. Treatments were: 1) control diet plus placebo injection; 2) 5% added dietary fat (hydrolyzed blend of animal and vegetable fat) + placebo injection; 3) control diet + 50 IU bovine somatotropin/d; and 4) 5% added dietary fat + 50 IU bovine somatotropin/d. Dietary fat reduced dry matter intake (21.6 vs. 22.7 kg/d) and elevated plasma triglycerides (34.7 vs. 29.2 mg/100ml). Injection of somatotropin lowered blood urea nitrogen, increased plasma free fatty acids, and increased plasma somatotropin. Milk production, milk fat percent, and 4% FCM production were increased by the injection of somatotropin. Milk protein percent was decreased (3.30 vs. 3.44%) with added fat and tended to be lower with somatotropin. The percentage of short-chain fatty acids (C6 to C14) in milk fat decreased with added fat while the percentage of stearic and oleic acids in milk fat increased. Production responses for fat plus somatotropin and somatotropin treatments were similar. Under the conditions of this study, the addition of dietary fat with injection of somatotropin had little effect on production parameters compared with that found with somatotropin alone.

Sodium Sesquicarbonate for Early Lactation Dairy Cows Fed Corn Silage-Based Diets

An experiment was conducted to evaluate the effects of dietary sodium sesquicarbonate on milk production and composition, feed intake, ruminal fermentation, and urine pH and composition in 32 multiparous Holstein cows in early lactation. Cows were fed high energy diets of 50% corn silage:50% concentrate containing 0 or .75% sodium sesquicarbonate (total ration DM basis) for 84 d postpartum. Sodium sesquicarbonate increased milk fat percentage (3.46 vs. 3.27%), milk fat yield (1.39 vs. 1.26kg), and 4% FCM yield (37.1 vs. 34.7kg) but did not affect milk yield, milk protein percentage or yield, feed intake, ruminal fluid pH, or ruminal VFA profile. Urine composition was not affected by sodium sesquicarbonate, but urine pH (8.14 vs. 8.04) and total urine output as estimated by creatinine concentration were higher than that of controls. In summary, sodium sesquicarbonate, added as .75% of the ration DM, was effective in improving milk fat percentage, milk fat yield, and 4% FCM yield in early lactation dairy cows fed corn silage-based diets.

Effect of Prepartum Energy, Body Condition, and Sodium Bicarbonate on Health and Blood Metabolites of Holstein Cows in Early Lactation

Effects of prepartum energy and of postpartum sodium bicarbonate (0, .75% DM) on health were studied in two trials. In trial 1, 36 cows consumed either 102, 131, or 162% of their energy requirement in the dry period. Postpartum glucose and D(–)-3-hydroxybutyrate levels indicated that 131% group (between wk 1 and 2) and 162% group (over the first 4 wk) were closer to a ketotic state than treatment groups at other times. Displaced abomasums occurred more frequently in the 162% group than either the 102 or 131 group. Sodium bicarbonate did not alter the health. In trial 2, 40 cows were used to evaluate the effects of prepartum energy for a longer period. Energy treatments imposed in late lactation and in the dry period were 1) cows fed to requirement in both periods; 2) cows overfed in the first and underfed in the second period; 3) cows fed to requirement in the first and overfed in the second; 4) cows overfed in both periods. Blood metabolites and health measures were not affected by energy or sodium bicarbonate treatments. Overconsumption of energy by prepartum cows should be avoided; however, for a short period, overconsumption did not produce major health problems.

Extruded Soybeans and Corn Gluten Meal as Supplemental Protein Sources for Lactating Dairy Cattle

Holstein cows in early lactation were used to compare three combinations of extruded whole soybeans and corn gluten meal to soybean meal. Treatments were (as a percentage of supplemental crude protein) 100% soybean meal; 75% whole soybeans extruded at 149°C, 25% corn gluten meal; 50% extruded soybeans, 50% corn gluten meal; and 25% extruded soybeans, 75% corn gluten meal. Diets were formulated to be 37.5% corn silage, 12.5% alfalfa cubes, and 50% concentrate (dry matter). Dietary crude protein was 15.7% of dry matter, and supplemental protein sources supplied 27% of total dietary protein. Diets were fed as total mixed rations and data were collected from 4 to 116 d postpartum.Milk and fat-corrected milk yields ranged from 31.0 to 34.3 and from 29.3 to 33.3 kg/d, respectively, and were greater for cows fed soybean meal than those cows fed 75 or 50% of their supplemental protein as extruded soybeans. Milk yield of cows consuming 75% of their supplemental protein from corn gluten meal was similar to all other treatments. Ruminal ammonia concentrations were lower in cows fed extruded soybeans and corn gluten meal compared with those fed soybean meal and ranged from 9.1 to 12.4mg/100ml. Total volatile fatty acid concentration and pH did not differ among treatments. Combinations of extruded soybeans and corn gluten meal were not advantageous compared with soybean meal as a supplemental protein source for lactating cows in this experiment.

Simultaneous measures of rates of ruminal digestion and passage of feeds for prediction of ruminal nitrogen and dry matter digestion in lactating dairy cows.

Three ruminal-cannulated Holstein cows in early lactation were fed three diets, each containing different energy and protein supplements in two consecutive 3 X 3 Latin squares. Each supplement contained a combination of three different feedstuffs (ground corn, soybean meal and wheat mids; corn gluten feed, rolled oats and distiller's dried grains; ground barley, brewer's grains and cottonseed meal). Diets consisted of 30% corn silage, 10% alfalfa hay, 10% alfalfa haylage, 17.7% ground corn plus minerals and vitamins, with the remainder as supplemental feedstuffs individually marked for measurement of ruminal turnover and in situ digestion rates. An extra period at the end of each Latin square was used to measure ruminal turnover and in situ digestion of individual forages. Diet had no effect on dry matter intake or milk yield. Mean fractional turnover (per hour) rate, measured by labeling feedstuffs with cerium, samarium or lanthanum was .044, .048, .049, .043, .047, .046, .050, .047, .049, .037, .046 and .045 for corn, soybean meal, wheat mids, corn gluten feed, oats, distiller's dried grains with solubles, barley, brewer's dried grains, cottonseed meal, alfalfa hay, corn silage and alfalfa haylage (P greater than .1), respectively. In situ-predicted ruminal degradation of N weighted for rate of passage was 61.4, 67.0, 81.5, 74.8, 86.3, 71.0, 75.7, 52.1, 54.2, 60.8, 71.7 and 70.9% for respective feedstuffs (P less than .05). In comparison with mean literature values for in vivo-measured N degradability, mean literature value = 1.172 (in situ predicted) -9.73 (P less than .05, R2 = .51). Results are interpreted to indicate a tendency for overestimating ruminal N degradability by in situ methods in feedstuffs of low degradability, while underestimating degradability in more highly degraded feedstuffs. Estimates were 11 to 17 percentage units lower than literature values for alfalfa hay and haylage and 17 units lower than literature values for distiller's dried grains.

Effects of Sodium Bicarbonate, Magnesium Oxide, and a Commercial Buffer Mixture in Early Lactation Cows Fed Hay Crop Silage

Sixteen early lactation Holstein cows fed 70% concentrate: 30% hay crop silage were used to determine effects of .7% sodium bicarbonate, .7% sodium bicarbonate plus .28% magnesium oxide, or 1.8% commercial buffer mixture (total ration dry basis). This mixture contained a variety of buffers, alkalis, and other compounds known to affect milk production or composition in some circumstances. Buffers did not affect dry matter intake, milk yield, or milk composition but decreased efficiency of milk production. Ruminal fluid pH was not affected, but fecal pH and digestibilities of dry matter, organic matter, energy, acid detergent fiber, and cellulose were increased by the mixed buffers compared with sodium bicarbonate alone. Total ruminal volatile fatty acid concentration was reduced by buffers. Compared with sodium bicarbonate alone, mixed buffers increased ruminal ammonia concentration, acetate proportion, and acetate:propionate ratio and decreased proportions of propionate and butyrate. Valerate was reduced by all three buffers. Ruminal volume and liquid dilution rate were unaffected, but buffers increased total fluid outflow from the rumen. Higher amounts of buffers or alkalis may be necessary to offset low rumen pH and affect production with hay crop silage-based diets.

Interaction of Protein Percent with Caloric Density and Protein Source for Lactating Cows

Experiment 1 was to test effect of three ratios of energy to protein in complete mixed diets for 36 lactating cows in three, 28-d periods. Energy was varied with cottonseed hulls, pelleted ground corrugated boxes, and a mixture of the two. Crude protein was varied with soybean meal to give energy:crude protein of 5.7, 5.0, and 4.6 for each energy amount. Cottonseed meal was compared with soybean meal in corrugated box diets. Feed intake was much higher with cottonseed hulls, and appreciable feedlot bloat resulted from pelleted ground corrugated box diets. Data adjusted to equal feed intake showed significant effect of energy to crude protein ratio on milk yield and improved digestion of organic matter with soybean meal vs. cottonseed meal.Experiment 2 tested the hypothesis that lactating cows consuming high-protein alfalfa may benefit from supplemental protein. Diets were 50% forage. Six diets were 14 or 18% crude protein in three ratios of alfalfa hay to corn silage (0:100, 50:50, 100:0). Additional corn silage diets were to compare: 14 versus 18% protein from distiller's dried grains with solubles only and with .5 or .9% urea (four diets); two 14% protein diets compared .6% added potassium chloride with or without .5% urea. Thirty-six Holstein cows in early lactation received one of the 12 diets in each of three 28-d periods. Distiller's grains with solubles markedly depressed milk yield (2.2 kg/d) and milk protein (.22%); heat damage of distiller's grains was evident. Protein interacted with alfalfa so gain in milk from 18 versus 14% increased from .55 to 1.36 to 2.66 kg/d as alfalfa changed from 0 to 50 to 100%. Thus, crude protein of alfalfa was not as effective as that from soybean meal in supporting milk yield.

Effect of Feeding IsoC-4 and C-5 Volatile Fatty Acids as Ammonium Salts on Concentration of Free Volatile Fatty Acids in Milk

We developed and validated an analytical procedure for measuring low concentrations of isobutyric, isovaleric, 2-methylbutyric, and valeric acids in milk and to determine whether feeding of these compounds as ammonium salts would increase their concentrations in milk. Acids were supplied as an aqueous blend (73.5% solids) composed of 67.5% ammonium salts of isovaleric, 2-methyl-butyric, and valeric acids and 32.5% ammonium isobutyrate. Fifteen Holstein cows in early lactation were assigned to the following treatments of isoC-4 and C-5 ammonium salts (g/cow per day anhydrous basis) added to a completely mixed basal diet: 0, 94, and 376. Milk samples were collected on days 32, 35, and 38 after feeding of ammonium salts commenced. Concentrations of isobutyric, isovaleric plus 2-methylbutyric, and valeric acids in milk were measured by the procedure, detailed in this paper, which enabled quantitation of low concentrations of these acids in milk. The procedure was validated by measured recovery of 100 ppb of each acid added to milk. Recoveries of acids (%) were isobutyric 82±10.3, isovaleric plus 2-methylbutyric 93±9.0, and valeric 105±12.0. Feeding acids did not increase their concentration in milk. Overall mean concentrations and ranges (ppb) in milk were isobutyric 37±15, 0 to 242; isovaleric plus 2-methylbutyric 58±8, 22 to 165; and valeric 39±6, 8 to 86.