In two trials, 47 and 54 Holstein cows were fed diets containing ensiled forages, ensiled and dry forages, or diets of different moisture contents. In trial 1, diets were fed during a preliminary dry period, early lactation, late lactation, a second dry period, and a second early lactation. In trial 2, four diets identical except for moisture content (78, 64, 52, and 40% dry matter) were fed for the first 200 days of lactation. Substitution of dry hay for alfalfa silage increased dry matter intake during the first early lactation, whereas partial substitution of corn silage with straw did not affect intake during dry periods. Dry matter intake increased linearly as dry matter content of diet increased in trial 2. Neither milk production nor body weight were affected by treatment in either trial. Percentage total solids increased linearly as dry matter content of diet decreased in trial 2. Volatile fatty acids differed slightly, but no trends were consistent. No differences of daily chewing time were observed. From these trials, diets of less than 60 to 65% dry matter may reduce intake by lactating dairy cows.
In three trials in consecutive years, 45, 59, and 63 lactating Holstein cows were fed grain mixtures containing either 0 or .25% methionine hydroxy analog with or without protein supplement. In Trial 1, diets were approximately 40% concentrate, and dietary protein averaged 13.2 and 15.8% (dry). Ration dry matter consisted of either 40 or 60% concentrate, and dietary protein averaged 13.5 or 17.3% in Trial 2 whereas concentrate was maintained at 60% of dry matter in Trial 3 with dietary protein at either 13.0, 15.0, or 17.5%. In Trial 1, milk yield or composition did not differ with methionine analog or protein supplementation. Protein supplementation increased milk yield on the 60% concentrate diets in Trial 2, and methionine analog increased milk fat percentage on the 60% concentrate diets. Cows fed 17.5% crude protein in Trial 3 produced more milk than those fed the two lower protein diets. Methionine analog increased milk fat percentage, and this increase was consistent at each percentage of dietary protein. Data from 179 lactations were combined and analyzed for response milk yield and composition to methionine analog included at either 0 or .25 to .30% of grain mixtures in 60% concentrate diets. Cows fed methionine analog produced milk higher in fat content and yielded more total fat and fat-corrected milk than controls.
Sixty-eight Holstein cows were fed diets consisting of 60% concentrate and 40% forage, dry basis. Diets were supplemented with DL-methionine or methionine hydroxy analog at either 0, .1, .2, or .3% of the concentrate. Dietary protein averaged 14% of total dry matter on all diets except for a positive control diet, which was 19% crude protein. Data were collected beginning 4 d postpartum and continued through 116 d postpartum. Milk yield was not influenced by either DL-methionine or methionine hydroxy analog. Supplementation with DL-methionine resulted in a quadratic response in milk fat percentage (3.34, 3.58, 3.72, 3.42) at 0, .1, .2, and .3% of the concentrate, respectively. Milk fat percentage increased linearly (3.34, 3.64, 3.60, 3.73) with supplementation of methionine hydroxy analog at 0, .1, .2, and .3%, respectively.
Three lactating Holstein cows with rumen cannulae were used in a 3 X 3 Latin square arrangement of treatments to study effects of methionine source on ciliated protozoa numbers and volatile fatty acid concentrations in the rumen. Cows were fed total mixed diets twice daily of 60% grain mix, 21% corn silage, and 19% alfalfa hay (dry basis). Methionine hydroxy analog, DL-methione, and sodium sulfate were added on an equal sulfur basis. Experimental periods were 14 d with four rumen samples taken daily on d 13 and 14. Total ciliated protozoa were higher when cows were fed DL-methionine than when fed methionine hydroxy analog or sodium sulfate. Ruminal concentrations of butyric acid and isobutyric acid were higher for the DL-methionine treatment than for analog or sodium sulfate treatments. Isovaleric acid concentrations were also higher in fluid from cows fed methionine compared with cows fed the analog.
Forty-eight Holstein cows were fed one of four diets containing 12.5% crude protein (negative control); 15.5% crude protein with untreated soybean meal; 15.5% crude protein with formaldehyde (.3%)-treated soybean meal; or 18% crude protein (positive control). Diets were 60% concentrate, 22% corn silage, 14% alfalfa hay, and 4% beet pulp (dry matter). Data were collected during the first 200 d of lactation. Dry matter intake, milk, and milk component yields did not differ among cows fed the untreated soybean meal, treated soybean meal, and positive control diets. Cows fed negative control diet consumed less dry matter and produced less milk than cows fed the other diets. Milk protein yield was lower for cows fed the negative control diet compared with the other diets. Nonprotein nitrogen content of milk increased as dietary protein increased.
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