The objective of this experiment was to assess the effects of a partial replacement of ryegrass (Lolium perenne) by red clover (Trifolium pratense) or alfalfa (Medicago sativa) supplemented with 0 or 41 g Acacia mearnsii extract (containing 0.615 g/g condensed tannins)/kg dietary dry matter on nitrogen turnover and methane release by sheep, using the respiration chamber technique. Across all variables, there was no significant interaction between basal diet and tannin supplementation. The partial replacement of the grass by the legumes remained without effect on the amounts of nitrogen excreted through faeces or urine. Nitrogen and energy utilisation was lower (P < 0.05) with ryegrass–alfalfa than with ryegrass alone, and methane release (kJ/MJ gross energy intake) was higher (P < 0.05) with ryegrass–red clover than with ryegrass alone. Tannin supplementation decreased (P < 0.05) ruminal ammonia concentration and urinary nitrogen excretion without affecting body nitrogen and energy retention, and reduced (P < 0.001) methane release by 13% on average. The results suggest that supplemented Acacia mearnsii tannins can be useful in mitigating methane and potential gaseous nitrogen emissions, whereas a replacement of grass by legumes obviously shows no advantage in this respect.

No abstract

In two in vitro experiments with the RUSITEC-apparatus, Brachiaria dictyoneura was tested alone and with legumes at dietary proportions of 1/3, 2/3, or 3/3 of Arachis pintoi (Expt 1) and 1/3 of Arachis pintoi, Cratylia argentea, or Calliandra calothyrsus (Expt 2). In Expt 2, all diets were evaluated with and without 80 mg/g diet of Sapindus saponaria fruits. In Expt 1, the stepwise replacement of the grass by A. pintoi curvi-linearly increased rumen fluid concentrations of ammonia, volatile fatty acids, bacteria, and protozoa. Methane release rates were 1.7, 7.3, 8.8, and 9.0�mmol/day. With increasing legume proportion, more organic matter and protein were degraded, the latter being only partially recovered as ammonia. In Expt 2, 1/3 of A. pintoi basically had the same effects as in Expt 1. Cratylia argentea was less effective in modifying the fermentation pattern. In association with a higher nutrient degradation and rumen ammonia concentration, C. argentea and A. pintoi increased methane release to about 3- and 4-fold levels. Calliandra calothyrsus reduced nutrient degradation and methane release per gram of organic matter degraded. Tannins, predominant in C. calothyrsus, might have affected methanogenesis. Sapindus saponaria reduced methanogenesis by 11% on average in grass-alone and legume-supplemented diets.

Two experiments were conducted to evaluate the effects of feeding wet corn gluten feed (WCGF) on subacute acidosis in cattle. In Exp. 1, 60 individually fed yearling steers (270 +/- 22 kg BW) were used in a 5 x 2 factorial arrangement of treatments. Steers were assigned to one of five dietary treatments: 1) dry-rolled corn (DRC), 2) 35% WCGF fed d 1 to 132, 3) 86.5% WCGF fed d 1 reduced to 35% WCGF by d 19 and increasing the proportion of DRC, 4) 86.5% WCGF fed d 1 to 132, or 5) 94.5% WCGF fed d 1 to 132. Final diets for Treatments 1 through 4 contained 92% concentrate and 8% alfalfa hay (DM basis). Treatment 5 was a 100% concentrate diet. All diets were fed with or without the addition of escape protein. During d 19 to 24, steers fed WCGF had less (P < .05) DMI variation than steers fed the control diet. Steers fed 86.5 and 94.5% WCGF had lower (P < .05) DMI and ADG than steers fed TReatments 1 through 3, although gain/feed was mot different (P > .10) In Exp. 2, three ruminally fistulated steers (615 +/- 36 kg BW) were used in a repeated 3 x 3 Latin square design. On d 14 of each period, 7.9 kg (DM) of 100% DRC, 50% DRC:50% WCGF, of 100% WCGF was intraruminally dosed as an acidosis challenge. Area within the curve below ruminal pH 6.0 was greater (P < .05) over a 24-h period for steers dosed with 100% DRC than for steers dosed with 50% DRC: 50% WCGF or 100% WCGF. In addition, more (P < .05) ruminal VFA accumulated over 24 h for steers dosed with 100% DRC. These data suggest that feeding WCGF does nor eliminate ruminal acidosis but may reduce the length of time cattle are exposed to the insult.

Six adult African-type hair sheep (BW = 40.3 +/- 6.3 kg) fitted with ruminal and duodenal cannulas were subjected to four treatments. Sheep were offered basal diets at a rate of 80 g of DM/kg of metabolic BW (equivalent to ad libitum access) consisting either of a low-quality grass hay (Brachiaria dictyoneura, 3.7% CP, DM basis) alone or in combination with a forage legume (Cratylia argentea, 18.6% CP, DM basis) in a 3:1 ratio (DM basis). In addition, 0 or 8 g of DM of Sapindus saponaria fruits (12.0% crude saponins, DM basis) per kilogram of metabolic BW was administered intraruminally. Supplementation of C. argentea increased intakes of OM (+21%; P < 0.01) and CP (+130%; P < 0.001), as well as ruminal fluid ammonia N concentrations (from 2.40 to 8.43 mg/dL; P < 0.001). Apparent OM and N digestibilities were not affected by legume addition, but ADF digestibility decreased by 10% (P < 0.01). Total ruminal VFA concentration was unchanged, but acetate:propionate was lower (P < 0.01) and isobutyrate proportion was greater (P < 0.001) with the legume addition. Legume supplementation increased duodenal flows of total N (+56%; P < 0.001), nonammonia N (+52%; P < 0.001), ruminal escape N (+80%; P < 0.001), and microbial N (+28%; P < 0.05). Microbial efficiency was not affected by legume addition. Supplementation of S. saponaria increased (P < 0.05) dietary OM intake by 14%, but had no effect on CP intake and ruminal fluid ammonia concentration or on OM and N digestion. Digestibility of ADF was decreased (P < 0.01) by 10% with S. saponaria as was acetate:propionate (P < 0.001) and the isobutyrate proportion (P < 0.001). Ruminal protozoa counts increased (P < 0.01) by 67% with S. saponaria. Duodenal N flows were not significantly affected by S. saponaria supplementation, except for microbial N flow (+34%; P < 0.01). Microbial efficiency was greater (P < 0.05) by 63% with the addition of S. saponaria. Few interactions between legume and S. saponaria supplementation were observed. The NDF digestibility was decreased with S. saponaria in the grass-alone diet, but not in the legume-supplemented diet (interaction; P < 0.05). Interactions were absent in ruminal fermentation measures and duodenal N flow, indicating that effects were additive. Results suggest that, even when not decreasing ruminal protozoa count, supplementation of S. saponaria fruits is a beneficial way to improve ruminal VFA profile, microbial efficiency, and duodenal flow of microbial protein in sheep fed tropical grass-alone or grass-legume diets.