Performance of high producing cows in early lactation fed protein of varying amounts, sources, and degradability

Eighty-four multiparous Holstein cows were fed a standard ration from 0 to 21 days postpartum and treatment rations from 22 to 91 days. Treatments varied in amount and source of protein, and only cows averaging at least 26 kg milk daily from 8 to 21 days postpartum were used. Experimental variables included protein percent (11.3, 14.5, 17.5), ammoniated versus untreated corn silage, and heated (2.5 h at 140 degrees C in forced draft oven) versus normal soybean meal. Treatments by protein percent and supplement types were: 1) 11%, untreated silage, normal soy; 2) 14%, ammonia silage, heated soy; 3) 14%, untreated silage, heated soy; 4) 14%, untreated silage, normal soy; 5) 17%, ammonia silage, heated soy; 6) 17%, untreated silage, heated soy; and 7) 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 nitrogen was the most productive and profitable of several rations compared for cows early in lactation.