In vitro gas production kinetics are influenced by grain processing, flake density, starch retrogradation, and Aspergillus oryzae fermentation extract containing α-amylase activity.

Grain processing such as particle size, flake density, or starch retrogradation can influence ruminal degradability characteristics; however, it is unclear how exogenous α-amylase supplementation interacts with different processed grains. Four experiments were conducted to compare the effects of Aspergillus oryzae fermentation extract (Amaize; Alltech Biotechnology Inc., Nicholasville, KY) supplementation on in vitro gas production kinetics of grain substrates with different processing methods that are common in the feedlot industry. In experiment 1, corn processing (dry-rolled, high-moisture, steam-flaked) and Amaize supplementation (0 or 15 U α-amylase activity/100 mL) were evaluated in a 3 × 2 factorial arrangement of treatments. The rate of gas production for dry-rolled corn was higher (P < 0.001) with Amaize supplementation. In experiment 2, flake density (296, 322, 348, 373, and 399 g/L) and starch retrogradation (storage in heat-sealed foil bags for 3 d at 23 or 55°C) were evaluated in a 5 × 2 factorial arrangement of treatments. There was a flake density × starch retrogradation interaction (P < 0.01) for the rate of gas production because the decrease in the rate of gas production with starch retrogradation was greater at lighter flake densities compared with heavier flake densities. In experiment 3, Amaize supplementation was evaluated across flake densities of nonretrograded steam-flaked corn (stored at 23°C) used in experiment 2. There was a flake density × Amaize interaction (P < 0.01) for the rate of gas production where Amaize supplementation resulted in a lower rate of gas production at lighter flake densities (296, 322, and 348 g/L) but a higher rate of gas production at heavier flake densities (373 and 399 g/L). In experiment 4, Amaize supplementation was evaluated across flake densities of retrograded steam-flaked corn (stored at 55°C) used in experiment 2. Gas production was lower after 24 h with Amaize supplementation for retrograded flakes produced to a density of 322 and 399 g/L while Amaize supplementation did not influence gas production at 24 h at other flake densities. There was a flake density × Amaize interaction for the rate of gas production because Amaize supplementation resulted in a faster (P < 0.01) rate of gas production for all flake densities except retrograded flakes produced to a density of 296 g/L. Enzymatic starch availability was positively correlated with the rate of gas production. These data demonstrate that supplementation of 15 U/100 mL of Amaize resulted in greater rates of gas production for dry-rolled corn, corn steam-flaked to heavier densities, and retrograded steam-flaked corn.

Grain processing has been used for decades to improve digestibility of finishing cattle diets, leading to improved growth and feed efficiency. Grain processing methods that result in changes in particle size, flake density, or starch retrogradation have all been shown to affect the degradability characteristics of nutrients in the rumen. Supplementation of feed additives containing exogenous enzyme activity could have the potential to improve digestibility, growth performance, and feed efficiency of livestock. However, it is unknown how supplementation of exogenous α-amylase activity influences degradability characteristics of different processed grains. The objectives of this study were to compare the effects of Aspergillus oryzae fermentation extract supplementation on in vitro gas production kinetics of grain substrates with different processing methods that are common in the feedlot industry. Enzymatic starch availability of steam-flaked corn, but not dry-rolled or high-moisture corn, was reflective of the rate of in vitro gas production. Increasing flake density and increasing starch retrogradation decreased the rate of in vitro gas production. Supplementation of A. oryzae fermentation extract resulted in increased rates of gas production for dry-rolled corn, corn steam-flaked at heavier densities, and retrograded steam-flaked corn.

Relationship between different sources of non-protein nitrogen and supplementation times on performance and metabolism of grazing Nellore cattle during the dry season.

Two experiments were conducted to evaluate the effect of supplementation with two sources of non-protein nitrogen at different feeding times on the performance, ingestive behavior, and rumen metabolism of growing Nellore bulls during the dry season. Exp. 1: One hundred and twenty Nellore bulls, weighing 206 ± 39 kg of initial body weight (BW) and 12 months of age, were divided into 20 paddocks, and they were used in randomized block design in a 2 × 2 factorial arrangement to evaluate performance and ingestive behavior. Exp. 2: 12 rumen cannulated animals with 509 ± 59 BW, divided into 4 paddocks, were used in a triple Latin square 4 × 4 in a 2 × 2 factorial arrangement to evaluate metabolism. The factors were 2 non-protein nitrogen sources (urea or slow-release urea) and 2 feeding times (07:00 or 13:00 at 4 g/kg BW of supplement). There was no influence of non-protein sources, supplementation time, or their interaction on the grazing time or the trough time during daytime, nighttime, or total (P ≥ 0.16). There were no interactions or factor effects on ADG (P ≥ 0.45) or final body weight (P ≥ 0.39). There was an interaction between supplementation time and collection time (P < 0.01) on ruminal pH. Animals supplemented in the morning had greater total SCFA at 18 h after supplementation (P = 0.03). The supplementation time and the non-protein nitrogen sources did not alter the ingestive behavior or animal performance of young Nellore cattle.

Conversion of Branched-Chain Amino Acids to Corresponding Isoacids - An in vitro Tool for Estimating Ruminal Protein Degradability.

In this paper we describe a study that evaluates the applicability of an in vitro fermentation model to assess the resistance of protein supplements to rumen degradation. The protein sources used were: soybean meal (SBM); whey protein (WHEY), which was expected to be rapidly degraded, and yeast-derived microbial protein (YMP), which was proposed to be resistant to rumen degradation. The basal diet was composed of grass silage and a commercial compound feed. The protein supplements were added at three isonitrogenous doses. Fermentation was monitored for 24 h and gas production, volatile fatty acids, lactic acid, and ammonia were analyzed at three timepoints. Protein degradation was estimated by determining the extent to which branched-chain amino acids (BCAA) introduced with the protein supplement were converted to corresponding branched-chain volatile fatty acids (BCVFA). At the highest dose of WHEY, 60% of introduced valine, leucine, and isoleucine was recovered as isobutyric, 2-methylbutyric, and isovaleric acid (products of BCAA decarboxylation and deamination), respectively. The BCVFA detected represented 50% of added BCAA with SBM, but <15% with YMP. Further indications that YMP protein is resistant to degradation were provided by analysis of ammonia. With YMP, the residual ammonia concentration only marginally exceeded that of the cultures with no protein supplementation, while it increased dose-dependently when the vessels were supplemented with WHEY or SBM. This suggests that with WHEY and SBM, the rate of deamination exceeded the rate of ammonia assimilation by bacteria. Residual ammonia and BCVFA, the two indicators of protein fermentation, were strongly correlated. Overall bacterial activity was monitored as yield of gas, volatile fatty acids, and bacteria. These three correlating parameters showed that WHEY only modestly stimulated fermentation, whereas SBM and YMP stimulated fermentation extensively, possibly owing to their higher carbohydrate content. The results presented suggest that the in vitro fermentation method was suitable for detecting differences in resistance of protein supplements to rumen degradation and following a full method validation could be a useful tool for diet formulation. The data obtained suggested that YMP was the most resistant and WHEY the most susceptible to degradation.

The effects of crude protein concentration and slow release urea on nitrogen metabolism in Holstein steers.

This experiment was conducted to determine the effects of slow release urea (SRU) and its interaction with crude protein (CP) level in the diet on N metabolism in Holstein steers. Eight rumen-cannulated Holstein steers (body weight 265 ± 18 kg) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial treatment structure. Treatment factors were the CP level in the diet, 10.9% versus 12.1% CP, and the non-protein nitrogen source used, urea versus SRU. Total collection of urine and faeces for 7 days allowed the estimation of N retention and diet digestibility. In addition, blood and rumen sampling allowed estimation of rumen fermentation and blood N profiles. Decreasing CP intake from 12.1% to 10.9% reduced urinary N output, but also reduced diet digestibility and N retention. When compared to urea, SRU did not alter N retention, but reduced ruminal ammonia and plasma urea concentrations. Although SRU did not improve N retention at either CP level, rumen ammonia and plasma urea concentrations were reduced, which may indicate that SRU may carry a lower risk for toxicity when compared to urea when fed at higher dietary concentrations.