Performance of High Producing Cows in Early Lactation Fed Protein of Varying Amounts, Sources, and Degradability

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Abstract
Multiparous Holstein cows (84) were fed a standard ration from 0-21 days postpartum and treatment rations from 22-91 days. Treatments varied in amount and source of protein, and only cows averaging at least 26 kg milk daily from 8-21 days postpartum were used. Experimental variables included protein percent (11.3, 14.5 and 17.5), ammoniated vs. untreated corn silage and heated (2.5 h at 140.degree. C in forced draft oven) vs. normal soybean meal [soy]. Treatments by protein percent and supplement types were: 11%, untreated silage, normal soy; 14%, ammonia silage, heated soy; 14%, untreated silage, heated soy; 14%, untreated silage, normal soy; 17%, ammonia silage, heated soy; 17%, untreated silage, heated soy; and 17%, untreated silage, normal soy. Milk production and dry matter intakes increased with increased protein. Differences were greater between 11 and 14% than between 14 and 17%. At 14 and 17% protein, cows fed normal soy produced less than those fed heated soy, but silage treatments were not different. The 17% ration containing ammonia silage and heated soy resulted in greatest milk production and highest income over feed costs. A combination of heated soybean meal to limit rumen degradability and ammonia in corn silage to furnish nonprotein N was the most productive and profitable of several rations compared for cows early in lactation.