Effect of synchronizing the rate of dietary energy and nitrogen release on rumen fermentation and microbial protein synthesis in sheep

Abstract

S U M M A R YThe effects of two diets, formulated to be either synchronous or asynchronous with respect to the hourly supply of energy and nitrogen, on rumen fermentation and microbial protein synthesis were studied in sheep.In Expt 1, the in situ degradation characteristics of nitrogen (N), organic matter (OM) and carbohydrate (CHO) fractions were determined in winter wheat straw, winter barley, malt distillers dark grains, rapeseed meal and fishmeal. The feeds exhibited a large range in degradability characteristics of the nitrogen and energy-yielding fractions.A computer program was developed, based upon the raw material degradation characteristics obtained from the above studies. The program was used to formulate two diets with similar metabolizable energy (9-5 MJ/kg DM) and rumen degradable protein contents (96 g/kg DM) but to be either synchronous (diet A) or asynchronous (diet B) with respect to the hourly rate of release of N and energy. The program was used to predict the hourly release of N, OM and CHO and the molar production of volatile fatty acids (VFA).In Expt 2, the two diets were fed to four cannulated sheep at the rate of 1 kg/day in four equal portions, in two periods, using a change-over design. Rumen ammonia concentrations followed the predicted rate of N degradation. A maximum concentration of 105 and 7 mM for diets A and B respectively was achieved within the first hour of feeding which then fell to 7 and 3 mM respectively. Rumen VFA proportions were more stable for the synchronous diet (A) than the asynchronous diet (B) and were more stable than predicted for both diets. True ruminal degradation of OM and CHO was similar for both diets and close to that predicted, although fibre degradability in diet A was 30% lower than predicted due to a reduction in both cellulose and hemicellulose digested. Microbial protein production was estimated simultaneously with L-[4,5-3 H]leucine and a technique based on cytosine. Estimates varied with marker but mean values indicated a 27% greater production of microbial N (g N/kg DM I) with the synchronous diet (A) and an average improvement in microbial protein efficiency (gN/kg OM truly degraded or CHO apparently degraded) of 13%, although neither difference was significant. There was evidence of a greater recycling of N in the animals and a significantly lower content of rumen degradable protein when the sheep were fed the asynchronous diet (B).The results are consistent with the view that synchronizing the rate of supply of N and energyyielding substrates to the rumen micro-organisms based upon ingredient in situ degradation data can improve microbial protein flow at the duodenum and the efficiency of microbial protein synthesis.

Substituição do farelo de soja pela farinha de glúten de milho na alimentação de cabras leiteiras

“…Estas observações têm sido obtidas em trabalhos que avaliaram o desempenho de animais recebendo dietas com diferentes proporções entre proteína degradável e não degradável no rúmen. Recentemente, a sincronização entre a disponibilidade de energia fermentável e a degradabilidade de nitrogênio no rúmen tem recebido considerável atenção (Sinclair et al, 1993;Sinclair et al, 1995).…”

Substitution of rumen degradable nitrogen with urea in sheep fed low quality Eragrostis curvula hay

“…These daily rumen pH patterns correspond with the eating and supplementation patterns of the wethers as they were fed and supplemented at 08h00 and at 16h00. Results from in sacco degradation studies conducted by Sinclair et al (1993) suggested that starch disappearance from maize in the rumen might take as long as 5 h to complete compared to the instantaneous in sacco disappearance of urea. While the rate of degradation of the pure starch was not determined in the present study, the decrease in rumen pH during the night hours (between 18h00 and 06h00) could be indicative of increased starch fermentation during those hours.…”

Digestion in Ruminants

“…Synchronous nutrient availability should allow more efficient use of nutrients, thus enhancing production of microbial products, increasing nutrient supply to the animal, and potentially improving animal production performance (Sinclair et al, 1993;Hall and Huntington, 2008).…”