-The objective of this study was to evaluate the in situ degradation profiles of dry matter (DM) and neutral detergent fiber (NDF) of different forages using nylon (50 μm), F57 (Ankom ® ) and non-woven textile (NWT -100 g/m 2 ) bags. Eight forage samples were used: sugarcane, corn silage, elephant grass cut at 50 and 250 days of regrowth, corn straw, signal grass hay, coast cross hay, and fresh alfalfa. Samples were incubated for 0, 3, 6, 12, 18, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, and 312 hours. Two bags of each textile were used at each incubation time, totaling 768 bags, using two crossbred Holstein × Zebu steers fitted with ruminal canullae. There was difference in the common rate of lag and degradation (λ) of DM for all forages, except for sugarcane. In general, higher λ estimates were obtained using nylon, followed by NWT and F57.Concerning NDF degradation profiles, differences in λ were observed for all forages. Greater estimates were obtained using nylon. Degradation profiles of DM and NDF must not be evaluated using F57 and NWT. These textiles underestimate the degradation rate due to constraints regarding exchange between bags' content and rumen environment.

We compared the lignin contents of tropical forages by different analytical methods and evaluated their correlations with parameters related to the degradation of neutral detergent fiber (NDF). The lignin content was evaluated by five methods: cellulose solubilization in sulfuric acid [Lignin (sa)], oxidation with potassium permanganate [Lignin (pm)], the Klason lignin method (KL), solubilization in acetyl bromide from acid detergent fiber (ABLadf) and solubilization in acetyl bromide from the cell wall (ABLcw). Samples from ten grasses and ten legumes were used. The lignin content values obtained by gravimetric methods were also corrected for protein contamination, and the corrected values were referred to as Lignin (sa)p, Lignin (pm)p and KLp. The indigestible fraction of NDF (iNDF), the discrete lag (LAG) and the fractional rate of degradation (kd) of NDF were estimated using an in vitro assay. Correcting for protein resulted in reductions (P<0.05) in the lignin contents as measured by the Lignin (sa), Lignin (pm) and, especially, the KL methods. There was an interaction (P<0.05) of analytical method and forage group for lignin content. In general, LKp method provided the higher (P<0.05) lignin contents. The estimates of lignin content obtained by the Lignin (sa)p, Lignin (pm)p and LKp methods were associated (P>0.05) with all of the NDF degradation parameters. However, the strongest correlation coefficients for all methods evaluated were obtained with Lignin (pm)p and KLp. The lignin content estimated by the ABLcw method did not correlate (P>0.05) with any parameters of NDF degradation. There was a correlation (P<0.05) between the lignin content estimated by the ABLadf method and iNDF content. Nonetheless, this correlation was weaker than those found with gravimetric methods. From these results, we concluded that the gravimetric methods produce residues Abbreviations: ABLadf, lignin determined by solubilization with acetyl bromide from the acid detergent fiber; ABLcw, lignin determined by solubilization with acetyl bromide from the cell wall matrix; CP, crude protein; DM, dry matter; iNDF, indigestible fraction of neutral detergent fiber; kd, fractional degradation rate of potentially degradable neutral detergent fiber; KL, lignin determined by Klason method; KLp, lignin determined by Klason method and corrected for protein; LAG, discrete lag for fiber degradation; Lignin (sa), lignin determined by solubilization of cellulose with sulfuric acid; Lignin (sa)p, lignin determined by solubilization of cellulose with sulfuric acid and corrected for protein; Lignin (pm), lignin determined by oxidation with potassium permanganate; Lignin (pm)p, lignin determined by oxidation with potassium permanganate and corrected for protein; NDF, neutral detergent fiber; pdNDF, potentially degradable fraction of neutral detergent fiber.

-The objective of this study was to evaluate the effects of supplementation with different sources of energy and nitrogenous compounds on the in vitro growth and production of bacteriocin of lactic acid bacteria. Incubations were performed by using ruminal fluid from a rumen-fistulated Holstein-Zebu steer. The animal was kept on a Brachiaria decumbens pasture receiving 200 g/day of supplemental crude protein. Substrates and inoculum were placed in glass flasks considering eight treatments: cellulose, cellulose and casein, cellulose and soy peptone, cellulose and urea, starch, starch and casein, starch and soy peptone and starch and urea. Successive incubations were conducted to select microorganisms according to the energy sources and nitrogenous compounds. Starch favoured growth of lactic acid bacteria when compared to cellulose. Supplementation with true protein (soy peptone and casein) stimulated the growth of these bacteria when compared to the control (without supplementation with nitrogenous compounds). The addition of urea did not stimulate the growth of lactic acid bacteria. No antimicrobial activity was detected from colonies of isolated lactic acid bacteria. Sources of true protein increase the competition between non-structural and structural carbohydrates fermenting bacteria.

No abstract

BackgroundThere is little information in the tropics with regard the comparative understanding of how an increased nitrogen supply in the rumen or in the intestines affects efficiency of nitrogen utilization in cattle. This study evaluated the effects of supplementation with nitrogenous compounds in the rumen, abomasum, or both on intake, digestibility and the characteristics of nitrogen utilization in cattle fed tropical forage. Four rumen- and abomasum-fistulated Nellore bulls (227 ± 11 kg) were used. Four treatments were evaluated: control, ruminal supplementation (230 g/d of supplemental protein in the rumen), abomasal supplementation (230 g/d of supplemental protein in the abomasum), and ruminal and abomasal supplementation (115 g/d protein in both the rumen and the abomasum). The basal forage diet consisted of Tifton 85 hay with a crude protein (CP) level of 78.4 g/kg dry matter. Casein was used as a supplement. The experiment was conducted using a 4 × 4 Latin square.ResultsThere were no differences between the treatments (P > 0.10) with regard to forage intake. The intake and total digestibility of CP increased (P < 0.01) with supplementation. The nitrogen balance in the body increased (P < 0.01) and muscle protein mobilization decreased (P < 0.01) with supplementation, regardless of the supplementation site. The efficiency of nitrogen utilization did not differ among the treatments (P > 0.10).ConclusionsThe supplementation of cattle fed tropical forage with protein in the rumen, abomasum, or both similarly increased the nitrogen accretion in animal, which reflects improvements on nitrogen status in animal body.

Effects of differing proportions of ruminal and abomasal protein infusion on intake, digestion, ruminal dynamics and the metabolic parameters of nitrogen (N) compounds were evaluated in beef bulls fed high-quality tropical forage (98.6 g crude protein, CP/kg dry matter) for ad libitum intake. Four Nelore bulls (280 ± 10 kg bodyweight) fitted with ruminal and abomasal cannulas were studied in a 4 × 4 Latin square. Treatments included: Control (no supplement) or 230 g/day of supplemental CP (as casein), with ratios of abomasal : ruminal infusion of 0 : 100, 50 : 50 or 100 : 0. Organic matter intake was not affected by treatments (P ≥ 0.30), though N intake increased by supplementation (P < 0.001). Total CP and organic matter digestibility were increased (P < 0.02) by protein supplementation. Nitrogen balance was 43% greater (P < 0.02) in the treatments with supplementation. Although supplementation did not affect (P = 0.98) the efficiency of absorbed N, a tendency towards a positive linear effect (P = 0.08) was observed when modifying the site of supplementation from the rumen to the abomasum. Supplementation increased (P < 0.01) ruminal ammonia-N, serum urea-N, urinary N and urea-N excretion, which subsequently decreased linearly (P < 0.01) by the displacement of supplementation from the rumen to the abomasum. The results indicate that protein supplementation, either in the rumen or abomasum produces similar effects on N retention. However, the metabolic mechanisms responsible for the improved N retention appear to differ between supplementation sites. Additionally, the efficiency of N utilisation increases with infusion of protein into the abomasum.

We aimed to evaluate the effects of diets, based on elephant grass or sugarcane as roughage and corn meal or rice bran as energy concentrate, on performance and body composition in terms of diet intake and digestibility. A total of 30 Santa Ines crossbreds (SIC), castrated male sheep with 19.8 ± 2.0 kg initial body weight (BW) were used. Six animals were slaughtered at the onset of the experiment to estimate the initial body composition for the other animals. The remaining 24 animals were distributed in a completely randomized 2 × 2 factorial design, with four treatments (two roughages and two concentrates) and six replicates. The sheep were slaughtered when they reached 30.0 kg BW. Elephant grass diets provided higher intake and digestibility than sugarcane diets for the following contents: dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre, minerals, total carbohydrates (TC), and total digestible nutrients (TDN). Among the concentrates, corn meal diets were associated with higher intakes than rice bran diets for the following contents: DM, OM, CP, TC, and TDN. Animals from all of the treatments exhibited low average daily weight gain and low protein and high fat and energy body levels. Sugarcane and rice bran can be used as ingredients in diets for sheep with low weight gain potential. Regardless of roughage or concentrate types used in diets for confined SIC sheep, performance and body composition remained unaltered.

In tropical regions, protein supplementation is a common practice in dairy and beef farming. However, the effect of highly degradable protein in ruminal fermentation and microbial community composition has not yet been investigated in a systematic manner. In this work, we aimed to investigate the impact of casein supplementation on volatile fatty acids (VFA) production, specific activity of deamination (SAD), ammonia concentration and bacterial and archaeal community composition. The experimental design was a 4 × 4 Latin square balanced for residual effects, with four animals (average initial weight of 280 ± 10 kg) and four experimental periods, each with duration of 29 days. The diet comprised Tifton 85 (Cynodon sp.) hay with an average CP content of 9.8%, on a dry matter basis. Animals received basal forage (control) or infusions of pure casein (230 g) administered direct into the rumen, abomasum or divided (50 : 50 ratio) in the rumen/abomasum. There was no differences ( P > 0.05) in ruminal pH and microbial protein concentration between supplemented v. non-supplemented animals. However, in steers receiving ruminal infusion of casein the SAD and ruminal ammonia concentration increased 33% and 76%, respectively, compared with the control. The total concentration of VFA increased ( P < 0.05) in steers receiving rumen infusion of casein. SAD and the microbial protein concentration did not vary significantly among treatments during the feeding cycle, but mean SAD values were greater in steers supplemented in the rumen and rumen/abomasum. Ruminal ammonia concentration was positively correlated with SAD in animals receiving ruminal infusion of casein. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed low similarity between treatments, animals and time of sample collection. Richness analysis and determination of the Shannon-Wiener index indicated no differences ( P > 0.05) in species richness and diversity of γ-proteobacteria, firmicutes and archaea between non-supplemented Nellore steers and steers receiving casein supplementation in the rumen. However, species richness and the Shannon-Wiener index were lower ( P < 0.05) for the phylum bacteroidetes in steers supplemented with casein in the rumen compared with non-supplemented animals. Venn diagrams indicated that the number of unique bands varied considerably among individual animals and was usually higher in number for non-supplemented steers compared with supplemented animals. These results add new knowledge about the effects of ruminal and postruminal protein supplementation on metabolic activities of rumen microbes and the composition of bacterial and archaeal communities in the rumen of steers.Keywords: beef cattle, casein, rumen degradable protein, deamination, microbial fingerprint ImplicationsFormulation of cattle diets requires balancing the availability of carbohydrates and protein in order to maximize microbial growth in the rumen. Increasing the availability of rumen degradable protein (RDP) is useful to red...