Nitrogen utilization in growing lambs: effects of grain (starch) and protein sources with various rates of ruminal degradation.

Abstract

The potential interaction between grain (starch) and protein sources with varying ruminal degradation rates on N utilization in growing lambs was evaluated. Three grain sources with varying ruminal degradation rates, (barley greater than steam-flaked sorghum [SFSG] greater than dry-rolled sorghum [DRSG]) and three protein sources (urea greater than a 50:25:25 mixture of urea: blood meal:corn gluten meal [N basis, U/BC] greater than 50:50 mixture of meal:corn gluten meal [N basis, BC]), were evaluated in a 3 x 3 factorial arrangement. Supplemental protein sources provided 33% of dietary N (CP = 11.0%). For each grain-protein combination, a 3 x 3 Latin square metabolism trial was conducted using two sets of three lambs and three periods. Within-square treatments were 1.4, 1.7 and 2.0 times maintenance intake levels. No interactions were observed (P greater than .2) between dietary treatments and intake level. Grain sources did not differ (P greater than .2) in N balance or the proportion of N retained. Lambs fed urea diets retained less N (3.6 vs 4.2 and 4.1 g/d for urea vs U/BC and BC, respectively; linear, P = .07; quadratic, P = .12) and utilized N less efficiently (43.1 vs 51.9 and 52.5%, respectively; linear, P less than .001; quadratic, P = .10) than lambs fed BC diets. The grain x protein interaction was significant for most variables. Nitrogen utilization was most efficient (24 to 27% of N intake retained) when rapidly degraded sources (barley and urea) and slowly degraded sources (sorghum and BC) were fed together or when U/BC was the supplemental protein source (interaction P less than .08). An advantage was found for selection of starch and protein sources with similar ruminal degradation rates.

Impact of glucogenic additive in transition dairy cow diets of varying ruminal starch degradability on yield and composition of milk and reproductive parameters

“…The grain type influenced the digestibility coefficients of dietary crude protein as well as NFE being significantly lower (by about 2 percentage points) in the treatments with maize-based concentrate in comparison with the treatment based on barley-wheat. Similar results regarding dry matter digestibility were obtained by Khorosani et al (2001) who studied the effect of barley grain substitution by corn on total tract digestibility of nutrients on cows, as well as the results obtained by Matras et al (1991) in the trial on sheep fed the diets based on barley vs. sorghum.…”

Effects of barley cultivar on energy and nitrogen metabolism of lambs

“…The N in 1990 Cougbar appeared to be poorly metabolized, as suggested by a low quantity of N retained as a percentage of absorbed N. Even though not significant, N balance as a percentage of absorbed N suggests that the metabolizability of 1991 Boyer and 1990 Steptoe was superior to that of 1990 Cougbar. Similarly, in a study with growing lambs, Matras et al (1991) determined that greater quantities of absorbed N does not always equate with greater N retention. The effi- …”

Efeito das fontes de amido e nitrogênio de diferentes degradabilidades ruminais.1. Digestibilidades parcial e total

“…Segundo NOCEK e TAMINGA (1991) e SAUVANT et al (1994), os glicídios de velocidade de degradação lenta teriam vantagem quando comparados aos glicídios de velocidade de degradação rápida, que perturbariam o ecossistema ruminal. Todavia, a sincronização entre os ritmos de degradação de nitrogênio e glicídios no rúmen é mais favorável ao desenvolvimento da flora microbiana e da utilização dos alimentos (HERRERA-SALDANA et al, 1990;NOCEK e TAMINGA, 1991;CAMERON et al, 1991;MATRAS et al 1991, SINCLAIR et al, 1993SINCLAIR et al, 1995).…”