Abstract 4

Alagon-H,-G

Laboratorio de Nutricion Animal, Centro Agronomico Tropical de Investigacion y Ensenanza, Turrialba, Costa Rica.

1990, 145 pp.; 16 pp. ref. Thesis, Centro Agronomico Tropical de Investigacion y Ensenanza, Turrialba, Costa Rica.

In experiment 1, 3 rumen fistulated steers, 700 kg, were used to estimate in situ DM and crude protein (CP) degradability in the rumen of 6 nitrogen sources, poro (Erythrina poeppigiana) leaves, fish meal, soyabean meal, meat meal, cottonseed meal and blood meal in a complete randomized block design. In experiment 2, 12 pure and crossbred multiparous Criollo X Jersey cows were used 60 days post partum in a replicated changeover 4 X 4 Latin square design. All cows received chopped whole sugarcane, molasses and rice polishings as basic ration, plus urea, poro foliage, fish meal or soyabean meal. Diets were isoenergetic and isonitrogenous. Each period had 14 days' adaptation and 7 days measurement, where milk production and quality were evaluated. At the end of each period, rumen liquor and blood samples were taken and volatile fatty acid, ammonia and urea were estimated. In experiment 1, there were significant differences among treatments. Rumen degradability of DM and CP of the protein sources was: low (fish meal and blood meal), intermediate (meat meal) and high (poro foliage, cottonseed meal and soyabean meal); 12% of poro CP was linked to acid detergent fibre. In experiment 2, daily milk yield was higher (P < 0.05) when cows were supplemented with fish meal or soyabean meal than with poro foliage or urea (11.0, 10.5, 9.6 and 9.3 kg/cow, respectively). Soyabean meal and fish meal resulted in the highest milk protein content, poro foliage in the highest milk fat and total solids; urea showed the lowest total milk and milk constituent yields. Rumen fermentation patterns were modified by the rate and extent of protein degradation. Molar proportion of butyric acid increased with molasses and sugarcane. There was a positive relation between ammonia concentration in rumen fluid and blood urea levels. Ammonia production was related to rate and extent of protein degradation in the rumen. Sugarcane intake was the same for all treatments, and was not decreased by poro. The cows gained weight in all but the urea treatment.