Sites of Digestion and Bacterial Protein Synthesis in Dairy Heifers Fed Fresh Oats with or Without Corn or Barley Grain

Abstract

Six Holstein-Friesian heifers fitted with ruminal, duodenal, and ileal cannulas were used in a replicated 3x3 Latin square to study the effects of partial replacement [1:1 dry matter (DM) basis] of fresh winter oats (WO) by ground corn (C) or barley (B) on digestion and bacterial protein synthesis. Supplemented diets contained 24% starch, and all diets were fed indoors at 2.5% of body weight (DM basis). Ruminal and total tract digestibilities of organic matter and neutral detergent fiber were similar for all treatments. Ruminal and total tract starch digestibility was similar for C and B diets. Nitrogen intake was greater for WO than for supplemented diets. However, duodenal flows of nonammonia N and bacterial N did not differ among treatments. The efficiency of bacterial protein synthesis was similar for the three diets, suggesting that the fermentation of high quality fresh forage DM provided sufficient energy for the microorganisms in the rumen. Ruminal ammonia-N concentration was greater for WO than for supplemented diets, and for C than for B diet. Ruminal fluid pH and concentrations of total volatile fatty acid were not different among diets, but concentration of acetate was higher and that of propionate was lower for WO than for supplemented diets and for C than for B diet. Supplementation of WO with barley rather than with corn decreased C2:C3 ratio without affecting fiber digestion. Supplements increased N utilization relative to N intake but did not increase duodenal nonammonia N flow.

Rumen pH, NH3-N concentration and forage degradation kinetics of cows grazing temperate pastures and supplemented with different sources of grain

“…Rumen pH of animals grazing pasture as sole feed was always near the optimum for cellulolytic activity (6.7 ± 0.5 according to Van Soest [17]) and was higher than values observed by other authors in similar conditions [5,13]. Supplementation led to significant lower pH values (Tab.…”

Supplementation with non-fibrous carbohydrates reduced fiber digestibility and did not improve microbial protein synthesis in sheep fed fresh forage of two nutritive values

“…Amaral et al (2011), supplementing ryegrass with cassava meal and corn gluten feed at a level of 7 g/kg in lambs, did not find changes in microbial protein synthesis but observed a decrease in the efficiency of the synthesis. García et al (2000), in dairy heifers grazing oats supplemented with corn or barley grain at 1% of their BW, reported reduced ruminal NH 3 concentration without changes in the production of microbial protein or the efficiency of its synthesis. These different results concerning microbial protein synthesis and its efficiency could be related to the vegetative stage (early or late) of the pasture, the level or the type of supplementation and the intake level.…”

The Effect of Carbohydrate Source on Nitrogen Capture in Dairy Cows on Pasture

“…García et al (2000) reported that ruminal ammonia concentration was significantly reduced when heifers fed fresh forage were supplemented with barley compared with corn (19.4 vs. 26.9 mg/dL). Khalili and Sairanen (2000) found that barley supplementation did not reduce rumen ammonia levels in cows grazing pasture that was 20.9% CP compared with corn supplementation; however, it was reduced by feeding a combination of barley, oats, and beet pulp (28.7, 32.1, and 21.8 mg/dL for corn, barley, and barley/oats/beet pulp mix, respectively.)…”