The Influence of Forage Type on the Production Response of Lactating Dairy Cows Supplemented with Different Types of Dietary Fat

Effects of tallow in diets based on corn silage or alfalfa silage on digestion and nutrient use by lactating dairy cows

Six multiparous Holstein cows (average 31 days in milk; 36.3 kg/d of milk) fitted with ruminal cannulas were used in a 6 x 6 Latin square with 21-d periods to investigate the effects of diets that varied in forage source and amount of supplemental tallow. Isonitrogenous diets in a 2 x 3 factorial arrangement were based on either high corn silage (40:10 corn silage to alfalfa silage, % of dry matter) or high alfalfa silage (10:40 corn silage to alfalfa silage, % of dry matter) and contained 0, 2, or 4% tallow. Intakes of dry matter and total fatty acids were lower when cows were fed the high corn silage diet. Tallow supplementation linearly decreased dry matter intake. Milk yield was unaffected by diet; yields of milk fat and 3.5% fat-corrected milk were higher for the high alfalfa silage diet but were unaffected by tallow. Milk fat percentage was higher for the high alfalfa silage and tended to decrease when tallow was added to the high corn silage diet. Contents of trans-C18:1 isomers in milk fat were increased by high corn silage and tallow, and tended to be increased more when tallow was fed in the high corn silage diet. Ruminal pH and acetate:propionate were lower when high corn silage was fed. Ruminal acetate:propionate decreased linearly as tallow increased; the molar proportion of acetate was decreased more when tallow was added to the high corn silage diet. Ruminal liquid dilution rates were higher for the alfalfa silage diet; ruminal volume and solid passage rates were similar among diets. Total tract apparent digestibilities of dry matter, organic matter, crude protein, starch, energy, and total fatty acids were unaffected by diet. Digestibilities of neutral detergent fiber, acid detergent fiber, hemicellulose, and cellulose were lower when high corn silage was fed. The high alfalfa silage diet increased intakes of metabolizable energy and N, and increased milk energy and productive N. Tallow decreased the amount of N absorbed but had few other effects on utilization of energy or N. Tallow linearly increased concentrations of nonesterified fatty acids and cholesterol in plasma; cholesterol was increased by high alfalfa silage. Overall, forage source had more pronounced effects on production and metabolism than did tallow supplementation. Few interactions between forage source and tallow supplementation were detected except that ruminal fermentation and milk fat content were affected more negatively when tallow was fed in the high corn silage diet.

Effect of supplemental tallow on performance of dairy cows fed diets with different corn silage:alfalfa silage ratios

A study was conducted to investigate the response to supplemental tallow of lactating cows fed basal diets with different alfalfa silage:corn silage ratios. We postulated that supplemental tallow will have decreasing negative effects on rumen fermentation, dry matter intake (DMI), and milk fat percentage as the dietary ratio of alfalfa silage:corn silage is increased. Eighteen Holstein cows averaging 134 +/- 14 d in milk were used in a replicated 6 x 6 Latin square design with 21-d periods. Treatments were arranged as a 2 x 3 factorial with 0 or 2% tallow (DM basis) and three forage treatments: 1) 50% of diet DM as corn silage, 2) 37.5% corn silage and 12.5% alfalfa silage, and 3) 25% corn silage and 25% alfalfa silage. Cows were allowed ad libitum consumption of a total mixed ration. Diets were formulated to contain 18% crude protein and 32% neutral detergent fiber. No fat x forage treatment interactions were observed. Fat supplemented cows had lower DMI and produced more milk with less milk fat content relative to non-supplemented cows. Concentration of trans-octadecenoic acids was higher in milk fat of tallow-supplemented cows. Tallow supplementation had no effect on ruminal pH and acetate:propionate ratio, but tended to decrease total volatile fatty acid (VFA) concentration in the rumen. Increasing the proportion of alfalfa silage increased DMI, milk fat percentage, and milk fat yield regardless of the fat content of the diet. Total VFA concentration and acetate:propionate ratio in the rumen were increased in response to higher levels of alfalfa in the diets. These results suggest that replacing corn silage with alfalfa silage did not alleviate the negative response of dairy cows to tallow supplementation at 2% of diet DM.

Effect of type and level of dietary fat on rumen fermentation and performance of dairy cows fed corn silage-based diets

The objective of this study was to investigate the effects of tallow and choice white grease (CWG) fed at 0, 2, and 4% of the diet dry matter (DM) on rumen fermentation and performance of dairy cows when corn silage is the sole forage source. Fifteen midlactation Holstein cows were used in a replicated 5 x 5 Latin square design with 21-d periods. Treatments were 0% fat (control), 2% tallow, 2% CWG, 4% tallow, and 4% CWG (DM basis). The forage:concentrate ratio was 50:50, and diets were formulated to contain 18% crude protein and 32% neutral detergent fiber (DM basis). Cows were allowed ad libitum consumption of diets fed twice daily as total mixed rations. Cows fed supplemental fat had lower DM intake and produced less milk and milk fat than cows fed the control diet. Feeding 4% fat reduced milk production and milk fat yield relative to feeding 2% fat. Treatments had little effect on the concentration of trans-octadecenoic acids in milk fat. Total trans fatty acids were poorly related to changes in milk fat percentage. Ruminal pH and total volatile fatty acids concentration were not affected by supplemental fat. The acetate:propionate ratio, NH3-N, and numbers of protozoa in the rumen were significantly decreased when fat was added to the diets. Source of dietary fat did not affect rumen parameters. There was no treatment effect on in situ corn silage DM and neutral detergent fiber disappearance. Including fat in corn silage-based diets had negative effects on milk production and rumen fermentation regardless of the source or level of supplemental fat.

Interaction of dietary fat and acid detergent fiber diets of lactating dairy cows

Twenty multiparous and 4 primiparous cows averaging 32 DIM were used in an experiment with a 2 x 2 factorial design for 12 wk to determine whether the response to supplemental choice white grease in the diet was augmented with higher fiber. Treatments were 1) 21% ADF with no added fat; 2) 21% ADF plus 6% added fat; 3) 28% ADF with no added fat; and 4) 28% ADF plus 6% added fat. Addition of fat decreased milk fat percentage and tended to decrease milk protein percentage. An interaction of fat by fiber by week for milk fat percentage suggested that ruminal fermentation was disrupted as the trial progressed when fat was included in the lower fiber diet. This disruption did not occur with the higher fiber diets. Yields of milk and FCM were not affected by treatment. There was no fat by fiber interaction for milk yield, which suggested that the yield response to fat was unaffected by fiber concentration. There were no treatment interactions for results of ruminal fermentation. Fiber increased ruminal acetate and the ratio of acetate to propionate but lowered molar percentages of propionate. Supplemental fat decreased acetate and increased propionate. The ratio of acetate to propionate was significantly decreased when fat was fed.

Effects of varying forage types on milk production responses to whole cottonseed, tallow, and yeast

Four forage treatments (45% corn silage, 33.75% corn silage plus 11.25% alfalfa hay, 11.25% bermudagrass hay, or 11.25% cottonseed hulls on a DM basis) were arranged factorially with no added fat, 12.5% whole cottonseed, or 2.5% tallow. Different diets were fed during three 28-d periods to 20 control Holstein cows and to 20 cows receiving yeast continuously in a split-plot design. Milk yield of cows fed cottonseed hulls with corn silage was 2.4 kg/d higher than with corn silage plus bermudagrass hay and .7 kg/d higher than with corn silage only or corn silage plus alfalfa hay. Whole cottonseed depressed milk yield by 1 kg/d. Cows fed yeast had increased DMI, and yeast interacted with forage so that more milk was produced by cows fed alfalfa diets. Yeast depressed milk protein percentage. Holstein cows in a commercial Florida dairy were fed no yeast or 10 g/d continuously for 60 d; milk fat percentage was greater (3.51 vs. 3.37%) with yeast. In summary, effects on milk and SCM were positive when cottonseed hulls were utilized with corn silage, negative with whole cottonseed, and neutral with supplemental tallow. Yeast effects on SCM, although not significant for either experiment, tended to be positive for both (mean +1.2 kg/d per cow).