Lactating Holstein cows averaging 193 d postpartum and fitted with rumen cannulae were used in two experiments to investigate the effects of supplementing Ca salts of fatty acids or prilled fatty acids to the diet on fermentation in the rumen, apparent total tract nutrient digestibility, milk production, and milk composition. Cows were fed ad libitum total mixed diets consisting of 45% concentrate and 55% forage. Treatments in Experiment 1 were: 1) control, 2) control plus 680 g/cow per d of Ca salts of fatty acids, 3) control plus 680 g/cow per d of prilled fatty acids, or 4) control plus 907 g/cow per d of prilled fatty acids. Treatments in Experiment 2 were: 1) control, 2) control plus 553 g/cow per d of Ca salts of fatty acids, or 3) control plus 454 g/cow per d of prilled fatty acids. Data suggest that Ca salts of fatty acids and prilled fatty acids are inert in the rumen and do not greatly alter fermentation in the rumen, apparent total tract digestibilities of DM, organic matter, ADF, NDF, and CP, or milk composition when fed at recommended amounts of 3 to 4% of the DM intake. The fact that milk production was not increased in these experiments by feeding Ca salts of fatty acids and prilled fatty acids may be attributed to the use of medium to low producing cows that were past the peak of milk production. Additional experiments are needed to obtain information about feeding these sources of supplemental fat to high producing cows during the early stages of lactation.

Four multiparous Holstein cows averaging 49 DIM and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design with 21-d periods to determine the effects of diets containing high oil corn grain and tallow. Cows were fed diets of alfalfa haylage and concentrate (37:63, DM basis) for ad libitum intake. Treatments were 1) control, no added fat; 2) high oil corn grain replacing regular corn grain; 3) high oil corn grain and 2.5% tallow; and 4) high oil corn grain and 5% tallow. Intake of DM, milk production, and yields of milk fat, milk protein, milk SNF, and 4% FCM were not affected by dietary fat, although DMI tended to be lower when cows were fed 5% tallow. Percentages of protein and SNF in milk were lower when cows were fed diets containing fat. Percentage of milk fat was lower when cows were fed diets containing tallow. Supplemental fat decreased total VFA concentrations in ruminal fluid. Cows fed high oil corn had a greater molar proportion of acetate and a larger acetate to propionate ratio in ruminal fluid than cows fed high oil corn and tallow. Digestibility of total fatty acids decreased when tallow was added to diets containing high oil corn. No differences were observed among treatments for total tract apparent digestibilities of DM and fiber or utilization of energy and N. Dietary high oil corn and 5% tallow tended to decrease DMI and to alter ruminal fermentation characteristics.

Four multiparous Holstein cows averaging 133 d postpartum and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding diets containing whole soybeans and tallow. Treatments were 1) control, no added fat; 2) control and 10% whole raw soybeans; 3) control, 10% whole raw soybeans, and 2.5% tallow; and 4) control, 10% whole raw soybeans, and 4.0% tallow. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (45:5:50, DM basis). Intakes of DM and production of milk, milk CP, milk SNF, and 4% FCM were not affected by feeding supplemental fat. Production of milk fat and weight percentages and yields of long-chain fatty acids in milk fat were increased, whereas weight percentages and yields of short- and medium-chain fatty acids were decreased by feeding supplemental fat. Digestibilities of DM, OM, energy, cellulose, and fatty acids were decreased slightly when fat was added to the diet, but utilization of energy and N for production of milk was not altered. Supplemental fats increased concentrations of NEFA and cholesterol in plasma. These data indicate that relatively large amounts of unprotected fat can be added to the diet of lactating dairy cows without deleterious effects on milk composition, ruminal fermentation, or nutrient digestibilities.

Four cows were utilized in a 4 x 4 Latin square design to investigate the effects of feeding Ca salts of long-chain fatty acids. Treatments were control diet with 1) no added fat, 2) 3% Ca salts of long-chain fatty acids, 3) 6% Ca salts of long-chain fatty acids, and 4) 9% Ca salts of long-chain fatty acids. Cows were fed chopped alfalfa hay, alfalfa haylage, corn silage, and concentrate (15:22:13:50) on a DM basis. Dry matter intake, energy intake, and ruminal fermentation were not altered greatly until Ca salts of long-chain fatty acids constituted 9% of DMI. Digestibilities of DM, OM, ADF, NDF, and hemicellulose were not affected by treatment. Digestibilities of cellulose, soluble residue, total C18 fatty acids, and total fatty acids followed quadratic patterns. Absorption of N was increased linearly when fat was fed, but digestibility of Ca was decreased linearly. Milk production, CP, and SNF were not altered greatly by inclusion of 3 or 6% Ca salts of long-chain fatty acids in the diet, but inclusion of 9% Ca salts of long-chain fatty acids decreased their production. Calcium salts of long-chain fatty acids increased milk fat percentage and production of fat and FCM when fed as 3 or 6% of the dietary DM but decreased yields of milk fat and FCM when fed as 9%. Calcium salts of fatty acids can be fed to provide up to 6% of the dietary DM without deleterious effects on ruminal fermentation and digestibilities of most nutrients.

Four multiparous Holstein cows averaging 36 DIM and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding extruded whole soybeans and Ca salts of long-chain fatty acids. Treatments were diets containing 1) no added fat, 2) 16% extruded whole soybeans, 3) 16% extruded whole soybeans and 3% Ca salts of long-chain fatty acids, and 4) 16% extruded whole soybeans and 6% Ca salts of long-chain fatty acids. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (35:15:50, DM basis). Intakes of DM and energy and production of milk, 4% FCM, fat, CP, and SNF were decreased by feeding extruded whole soybeans and 6% Ca salts of long-chain fatty acids, but differences were small among the other treatments. The weight percentages and yields of C18:0, C18:1, and C18:2 in milk were increased, and most shorter chain fatty acids were decreased, by feeding supplemental fat. Digestibilities of DM, OM, ADF, soluble residue, total C18 fatty acids, and total fatty acids were decreased, but digestibility of hemicellulose was increased by feeding supplemental fat. The largest decrease in digestibilities of most dietary constituents and in energy and N utilization occurred when 16% extruded whole soybeans plus 6% Ca salts of long-chain fatty acids were fed to the cows. Calcium salts of long-chain fatty acids can supply up to 3% of the dietary DM in diets containing 16% extruded whole soybeans without having deleterious effects on most variables measured in this experiment.

Three experiments were conducted to determine the effects of acidification of milk replacers containing soy protein concentrate on diet digestibility and growth of Holstein bull calves. In Experiment 1, six calves (6 wk old) were fed at 10% of BW/d either acidified milk replacer containing soy protein concentrate or untreated milk replacer containing soy protein concentrate. Replacers were reconstituted to 12.5% DM for 10-d adjustment and 4-d collection periods to determine digestibility and N balance. Digestibilities of DM, ether extract, and N were similar between treatments. Nitrogen retention and N retention as a percentage of that absorbed were higher for calves fed the acidified diet. In Experiment 2, 20 calves (1 wk old) were fed diets identical to those diets fed in Experiment 1 at 20% of BW/d for 4 wk. Calves were allowed to adjust to the diet for 5 d. Growth parameters were measured and amount of feed offered was adjusted weekly. Calves fed the untreated diet had higher daily weight gains, girth gains, height gains, and better feed utilization. In Experiment 3, 21 calves were fed either the aforementioned diets or a replacer based on milk proteins at 10% of BW/d (12.5% DM) for 4 wk. Growth parameters were measured and DM intakes were adjusted weekly. Growth and feed conversion were similar across diets. Replacers containing soy protein concentrate or large amounts of whey may need to be supplemented with additional methionine to maximize rate of gain.

Thirty-six cows were blocked by calving date and randomly assigned to one of three treatments. Cows were on treatments 3 weeks prepartum through 8 weeks post-partum. Treatments were as follows: (i) no direct-fed microbial (DFM) or cellulase and amylase enzymes (C), (ii) 45.4 g/day of DFM (D) or (iii) 45.4 g/day of DFM and 18.2 g/day of enzyme (DE). Total mixed ration fed and refused were measured daily to determine dry matter intake (DMI). Blood samples were taken three times weekly and analysed for β-hydroxybutyrate, glucose and non-esterified fatty acids. Body weight (BW) was measured weekly. Colostrum was weighed and analysed for IgA and IgG concentration. Calves were fed 4 L of colostrum within 2 hr of birth. Calf blood samples were taken at 0 and 24 hr for analysis of IgA and IgG concentrations and apparent efficiency of absorption. Milk yield was measured daily and samples collected weekly. Initial BW was different among treatments with D being lesser than C or DE treatments. Body weight, weight gain, efficiency of gain, DMI and blood parameters were unaffected. Treatment did not affect colostrum yield. Ash percentage of colostrum tended to increase with D and DE, while IgA and total solids yield decreased with D. Colostrum fat yield was decreased in D and DE. Treatments did not impact BW, serum IgA and IgG concentrations or apparent efficiency of absorption of calves. Post-partum BW, DMI, blood parameters, milk production and composition were unaffected by treatment. However, cows on D gained more BW and tended to have greater efficiency of gain compared to those on DE, but were similar to C. Somatic cell scores were greatest for D. Results indicate that DFM and enzyme supplementation did not improve health and performance of dairy cattle during the pre- and post-partum periods under conditions of this study.