Effects of synchronizing the rate of dietary energy and nitrogen release in diets with a similar carbohydrate composition on rumen fermentation and microbial protein synthesis in sheep

Abstract

S U M M A R YThe effects of synchronizing dietary energy and nitrogen supply in diets with a similar carbohydrate composition on microbial protein synthesis and rumen fermentation were examined in sheep. Two diets were formulated to be either synchronous (diet S) or asynchronous (diet A) for the hourly release of nitrogen (N) and energy to the rumen. Diet S contained (g/kg) 425 g wheat straw, 400 g winter barley, 150 g rapeseed meal and 25 g minerals/vitamins and diet A contained 505 g wheat straw, 458-5 g winter barley, 11-5 g urea and 25 g minerals/vitamins. Both diets were fed at the rate of 1 kg/day in four equal portions, to four cannulated sheep, in two periods in a change-over design.Rumen ammonia concentrations followed the predicted hourly trend in N degradation with a peak 1 h after feeding of 10 mM for diet S and 16 mM for diet A before falling within 3 h of feeding to 4 ITIM in animals fed either diet. Rumen volatile fatty acid (VFA) concentrations followed the cyclical trend predicted by stoichiometric equations, whilst rumen VFA ratios were more stable than predicted in animals fed either diet. The observed content of rumen degradable protein and organic matter truly degraded in the rumen was similar for both diets. The increase in total CHO digested in the rumen observed with diet A (427 g/kg DM) compared with diet S (364 g/kg DM) can be attributed to the greater content of starch in the asynchronous diet, which had a high degradability. The efficiency of microbial protein synthesis (g N/kg OM truly degraded in the rumen) was 11-20% greater in animals fed the synchronous diet (S) than the asynchronous diet (A). It is concluded that microbial N production was more efficient when dietary energy and N supply were synchronized.

Production responses from lambs grazed on Lolium perenne selected for an elevated water-soluble carbohydrate concentration

“…Carruthers and Neil [4] supplemented Friesian cows on high or low nitrogen pasture diet with non-structural carbohydrate and in both cases observed significant reductions in rumen ammonia concentrations. Formulation of diets that improve the balance in nitrogen and energy release into the rumen on an hourly basis increased the efficiency of microbial protein synthesis [22] and the growth rate of lambs [30]. In ewes fed an asynchronous diet the levels of plasma urea were increased, suggesting a reduction in nitrogen efficiency [29].…”

“…It has been suggested that efficient microbial protein synthesis relies upon the synchronous provision of energy and protein nitrogen to the rumen microbial population [22]. In ruminant diets, characterised by an insufficient supply of readily available energy for balanced rumen fermentation to occur, acetate production dominates with a resultant reduction in the efficiency of utilisation of both nitrogen and energy [3].…”

Milk Production and Composition, Rumen Fermentation Parameters, and Grazing Behavior of Dairy Cows Supplemented with Different Forms and Amounts of Corn Grain

“…Some workers suggest that the supplemented carbohydrate should have a similar rate and extent of degradation in the rumen to that of CP (19) to maximize N assimilation. However, this has been difficult to accomplish in grazing cows.…”

Influence of diet on growth yields of rumen micro-organisms in vitro andin vivo: influence on growth yield of variable carbon fluxes to fermentation products

“…a high efficiency of microbial production (EMP), is desired in ruminant animal nutrition because it leads to efficient feed N and C utilization (Beever, 1993;Leng, 1993;Van Soest, 1994). It was, for example, demonstrated that the nature and fermentation characteristics of feed protein (N) and carbohydrates can affect EMP (Brown & Pittman, 1991;Clark et al 1992;Sinclair et al 1995), thus rejecting the assumption of a constant EMP still prevalent in some feeding systems (Ausschuss für Bedarfsnormen der Gesellschaft für Ernährungsphysiologie der Haustiere, 1986;Agriculture and Food Research Committee, 1993). As an exception, the Cornell net carbohydrate and protein system Sniffen et al 1992) considers feed-or diet-specific differences in EMP, suggesting their prediction by the analysis of numerous feed carbohydrate and N fractions with associated degradation rates (National Research Council, 1996).…”