Fifty-seven Holstein cows (19 primiparous) were assigned to one of four dietary treatments arranged as a 2 × 2 factorial during d 22 to 150 of lactation to examine the effects of raw or extruded (149°C) soybeans and of rumen-protected methionine and lysine supplements on lactation performance. Dietary DM contained 16.5% CP and consisted of 32.2% alfalfa silage, 5.4% alfalfa pellets, 10.4% corn silage, 38.5% high moisture shelled corn, 11.4% nitrogenous supplements, and 2.1% minerals and vitamins. From d 15 prepartum to d 21 of lactation, all cows were fed a protein supplement of raw and extruded soybeans in a 1:1 ratio. During the experimental period, an average of 18.9 kg of DM were consumed. This contained, for the amino acid-supplemented treatments, 14.2 g each of rumen-protected DL-methionine and L-lysine. Experimental data were adjusted by covariance for means measured during d 4 to 21. Dietary treatments did not affect yield of milk, milk protein or milk casein, DMI, BW and condition, or plasma urea N. Extruded soybeans depressed milk fat percentage. Evaluation of diets in continuous culture fermenters indicated no differences in digestibility of DM and carbohydrates. Ammonia N concentration in the effluent and CP degradation were lower for extruded than for raw soybean diets. Flows of NAN and total amino acids from fermenters did not differ among diets.
Bibliographical noteFunding Information:
Received July 20, 1990. Accepted January 7, 1991. lhblished as Paper Number I8305 of the Scientific Joamal Series of the Mimwota Agricultural Expesiment Station on research conducted unda Mirmesota Agricul- haal Expcrimnt Station Rojcct Number 1647, sapportcd by the College of Agriculture and by a grant froin the Minnesota Soybean Research and Promotion Council.
The authors are grateful to Triple "F", Inc. for providing the extruded soybeans used in this study, to Eastman Chemicals Division Research Laboratories, and to the University of Minnesota Computer Center for support of computing costs.
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- rumen-protected DL-methionine
- rumen-protected L-lysine
- total nonstructural carbohydrates