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The aim of this study was to examine whether the combination of dietary soluble fiber and cellobiose exerts a synergistic effect on growth performance, health status, fermentation traits, and immune response in rabbits. Six treatments in a 3 × 2 factorial arrangement were used: 3 cellobiose concentrations in drinking water (0.0, 7.5, and 15.0 g/L) × 2 dietary levels of soluble fiber (84.0 and 130 g/kg DM, for the low soluble fiber [LSF] and high soluble fiber [HSF] diets, respectively). A total of 318 young rabbits (53/treatment) were weaned at 34 d of age and had ad libitum access to feed and water. At 46 d of age, 9 rabbits/treatment were slaughtered and ileal and cecal digesta were collected to analyze VFA profile and the immune response in the cecal appendix mucosa. At 48 d of age, the cellobiose supplementation was withdrawn and the experimental diets were replaced by a standard commercial diet until 61 d of age. From 34 to 48 d of age, there was a linear increase of mortality with the level of cellobiose in the HSF group (0% vs. 17.1%; P = 0.017). In contrast, a quadratic effect of cellobiose level on mortality was observed in the LSF group, the rabbits offered 7.5-cellobiose showing the lowest mortality (5.7% vs. 21.4%; P = 0.030). Cellobiose level had a quadratic effect on ADFI, ADG, and G:F in this period (P ≤ 0.047), with the 7.5-cellobiose groups having the best growth performance. In contrast, only minor changes on these traits were observed from 48 d of age onwards. Cellobiose level influenced quadratically the ileal VFA concentrations (P = 0.014), showing the maximal value in the 7.5-cellobiose groups. In rabbits fed 7.5-cellobiose-LSF, a change of acetate to propionate, butyrate, and valerate was observed in the ileum. Increasing cellobiose levels reduced linearly cecal VFA concentrations in HSF fed rabbits, but no effect was detected in LSF groups (P = 0.046). The level of soluble fiber increased VFA concentrations in both the ileum (by 22%; P < 0.001), and the cecum (by 11%; P = 0.005). The relative gene expression of IL-6, IL-10, TNF-α, iNOS, MUC-1, and toll-like receptors (TLR-2 and TLR-4) in the cecal appendix increased linear and quadratically with increasing levels of cellobiose (P ≤ 0.063). In conclusion, in rabbits fed LSF diets, a dose of 7.5 g cellobiose/L drinking water would be recommended, whereas these levels of cellobiose supplementation should be avoided in rabbits fed HSF diets.

The objective of this study was to investigate the effect of dietary supplementation with fish oil on growth performance (during all fatening period), carcass characteristics and fatty acid (FA) profile of muscle and fat tissues (at slaughter), as well as cecal fermentation and ileal mucosa morphology of growing rabbits (at 30, 45, and 60 d of age). Two isonitrogenous and isoenergetic diets, only differing in their fat source, were formulated and provided each to 24 does (12 per diet) and their offspring during pregnancy and lactation. The control diet contained 4.59 g of n-3 per 100 g of total FA, and the enriched diet contained 14.9 g of n-3 per 100 g of total FA. From weaning (30 d of age) to slaughter (60 d), the litters (12 per diet; 8 kits each) continued fed the corresponding experimental diet. There were no differences (P > 0.05) between groups in ADFI, ADG and G:F ratio during the growing period. At slaughter, BW, full gastrointestinal tract weight, carcass yield, meat color and pH, drip loss percentage, content of scapular fat and tissue composition of the left hind leg were similar between groups (P > 0.05), but perirenal fat was lower (P = 0.020) and skin weight and abdominal fat tended to be lower (P = 0.055 and P = 0.063, respectively) in enriched rabbits than in control ones. Total PUFA content in both LM and perirenal fat was greater (P = 0.021 and 0.255) either pH and NH3-N concentrations in the cecum or ileal morphology (crypt depth and villi length). The results showed that dietary fish oil supplementation enhanced beneficial long-chain n-3 FA and decreased n-6/n-3 ratio in rabbit meat and fat, being healthier for human consumption, without having negative effects on growth performance, cecal fermentation, and ileal morphology or carcass characteristics.

The aim of this study was to assess the effects of malate salts and culture on growth performance, carcass quality, ruminal fermentation products, and blood metabolites in heifers raised under southern Europe practical farm conditions. A total of 108 Charolaise cross heifers (214 ± 27.3 kg BW and 6.4 ± 1.1 mo of age) were housed in 18 pens of 6 animals each and used in a 114-d feedlot study. There was a totally randomized experimental design, and 6 pens were assigned to each of the following experimental diets: a control (no supplementation), the control plus 4 g of disodium/calcium malate mixture per kilogram of concentrate (2.12 g malate/kg), and the control plus 0.15 g of CBS 493.94 per kilogram of concentrate (1.5 × 10 cfu/kg). The control diet consisted of wheat-barley-based pelleted concentrate (32% starch, DM basis) and full-length barley straw. Concentrate and straw were fed separately ad libitum (5% orts) in an 88:12 ratio. On Days 0, 56, and 114, ruminal fluid and blood samples were obtained from each heifer between 2 and 2.5 h after the morning feeding by ruminocentesis and tail venipuncture, respectively. Body weight, concentrate ADFI, and G:F were recorded at 28, 56, 84, and 114 d. At slaughter, hot carcass weight and yield and carcass classification were determined in 2 representative heifers per pen (12 animals per dietary treatment). Supplementation with malate salts or did not affect concentrate ADFI ( = 0.98), ADG ( = 0.74), or G:F ( = 0.50) at any time during the experiment. At slaughter, there were no differences in carcass weight ( = 0.86), classification ( = 0.18), or carcass yield ( = 0.84) among experimental groups. Also, there were no differences treatments on ruminal pH ( = 0.24), ruminal fermentation products ( = 0.69, = 0.88, and = 0.93 for total VFA, NH-N, and lactate, respectively), and blood metabolites ( = 0.96, = 0.82, and = 0.15 for glucose, urea N, and lactate, respectively). In conclusion, under the feeding and management conditions of this study, diet supplementation with malate salts or did not have any significant effects on growth performance, carcass quality, ruminal fermentation products, and blood metabolites.

The objective of this study was to investigate the effect of dietary supplementation with fish oil on growth performance (during all fatening period), carcass characteristics and fatty acid (FA) profile of muscle and fat tissues (at slaughter), as well as cecal fermentation and ileal mucosa morphology of growing rabbits (at 30, 45, and 60 d of age). Two isonitrogenous and isoenergetic diets, only differing in their fat source, were formulated and provided each to 24 does (12 per diet) and their offspring during pregnancy and lactation. The control diet contained 4.59 g of n-3 per 100 g of total FA, and the enriched diet contained 14.9 g of n-3 per 100 g of total FA. From weaning (30 d of age) to slaughter (60 d), the litters (12 per diet; 8 kits each) continued fed the corresponding experimental diet. There were no differences (0.05) between groups in ADFI, ADG and G:F ratio during the growing period. At slaughter, BW, full gastrointestinal tract weight, carcass yield, meat color and pH, drip loss percentage, content of scapular fat and tissue composition of the left hind leg were similar between groups (0.05), but perirenal fat was lower ( = 0.020) and skin weight and abdominal fat tended to be lower ( = 0.055 and = 0.063, respectively) in enriched rabbits than in control ones. Total PUFA content in both LM and perirenal fat was greater ( = 0.021 and0.001, respectively) in enriched rabbits, that also showed lower n-6/n-3 ratios in LM (1.61 vs. 5.80;0.001) and perirenal fat (4.71 vs. 12.0;0.001) than those fed the control diet. Cecal concentrations of total VFA were greater (0.001) in enriched than in control group at 30, 45 and 60 d of age, but diet did not affect ( ≥ 0.332) VFA profile, with the exception of a lower ( = 0.013) proportion of minor VFA (sum of isobutyrate, isovalerate, and valerate) in control group. Diet did not affect (0.255) either pH and NH-N concentrations in the cecum or ileal morphology (crypt depth and villi length). The results showed that dietary fish oil supplementation enhanced beneficial long-chain n-3 FA and decreased n-6/n-3 ratio in rabbit meat and fat, being healthier for human consumption, without having negative effects on growth performance, cecal fermentation, and ileal morphology or carcass characteristics.

The aim of this study was to compare automated ribosomal intergenic spacer analysis (ARISA) and denaturing gradient gel electrophoresis (DGGE) techniques to assess bacterial diversity in the rumen of sheep. Sheep were fed 2 diets with 70% of either alfalfa hay or grass hay, and the solid (SOL) and liquid (LIQ) phases of the rumen were sampled immediately before feeding (0 h) and at 4 and 8 h postfeeding. Both techniques detected similar differences between forages, with alfalfa hay promoting greater (P 0.05) over the postfeeding period were detected by DGGE. The ARISA technique showed lower (P 0.05) in bacterial diversity between both rumen phases were detected by DGGE. Under the conditions of this study, the DGGE was not sensitive enough to detect some changes in ruminal bacterial communities, and therefore ARISA was considered more accurate for assessing bacterial diversity of ruminal samples. The results highlight the influence of the fingerprinting technique used to draw conclusions on factors affecting ruminal bacterial diversity.

The aim of this study was to assess the effects of malate salts and culture on growth performance, carcass quality, ruminal fermentation products, and blood metabolites in heifers raised under southern Europe practical farm conditions. A total of 108 Charolaise cross heifers (214 ± 27.3 kg BW and 6.4 ± 1.1 mo of age) were housed in 18 pens of 6 animals each and used in a 114-d feedlot study. There was a totally randomized experimental design, and 6 pens were assigned to each of the following experimental diets: a control (no supplementation), the control plus 4 g of disodium/calcium malate mixture per kilogram of concentrate (2.12 g malate/kg), and the control plus 0.15 g of CBS 493.94 per kilogram of concentrate (1.5 × 10 cfu/kg). The control diet consisted of wheat-barley-based pelleted concentrate (32% starch, DM basis) and full-length barley straw. Concentrate and straw were fed separately ad libitum (5% orts) in an 88:12 ratio. On Days 0, 56, and 114, ruminal fluid and blood samples were obtained from each heifer between 2 and 2.5 h after the morning feeding by ruminocentesis and tail venipuncture, respectively. Body weight, concentrate ADFI, and G:F were recorded at 28, 56, 84, and 114 d. At slaughter, hot carcass weight and yield and carcass classification were determined in 2 representative heifers per pen (12 animals per dietary treatment). Supplementation with malate salts or did not affect concentrate ADFI ( = 0.98), ADG ( = 0.74), or G:F ( = 0.50) at any time during the experiment. At slaughter, there were no differences in carcass weight ( = 0.86), classification ( = 0.18), or carcass yield ( = 0.84) among experimental groups. Also, there were no differences treatments on ruminal pH ( = 0.24), ruminal fermentation products ( = 0.69, = 0.88, and = 0.93 for total VFA, NH-N, and lactate, respectively), and blood metabolites ( = 0.96, = 0.82, and = 0.15 for glucose, urea N, and lactate, respectively). In conclusion, under the feeding and management conditions of this study, diet supplementation with malate salts or did not have any significant effects on growth performance, carcass quality, ruminal fermentation products, and blood metabolites.

Four ruminally cannulated sheep were used in a crossover design to assess the postprandial changes of fiber-degrading microbes in the solid phase of the rumen of sheep fed 2 high-forage diets. The diets had forage:concentrate ratio of 70:30 (DM basis) and either alfalfa (Medicago sativa) hay (AL) or grass hay (GR) as forage (FOR). Sheep were fed twice daily, and samples from solid rumen digesta were taken at 0, 4, and 8 h after the morning feeding. Postprandial changes of DNA concentrations of all determined microbial populations were similar for the 2 diets. Samples taken at 4 h after feeding had lesser (P < 0.05) concentrations of total bacterial DNA determined with real-time PCR and bacterial diversity and greater (P < 0.05) protozoal DNA concentrations, relative abundance of fungal, Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus DNA compared with those taken at 0 and 8 h. No effect (P = 0.41 to 0.76) of FOR was detected either on concentrations of bacterial and protozoal DNA or the relative abundance of the 2 Ruminococcus DNA, but GR diet promoted greater (P < 0.001) relative abundance of F. succinogenes and fungal DNA compared with AL diet. Fibrobacter succinogenes was the most abundant (P < 0.05) of the 3 cellulolytic bacteria for both diets, with no differences (P < 0.05) between the 2 Ruminococcus species. Rumen pH and carboxymethylcellulase, Avicelase, and amylase activities were not affected (P = 0.15 to 0.69) by FOR, but xylanase activity was greater (P = 0.01) for GR diet. The influence of FOR on microbial communities in ruminal solid digesta was more evident in the first hours after feeding than at later times after feeding, which highlights the influence of sampling time when investigating dietary effects on rumen function and microbial populations.

Six ruminally and duodenally cannulated sheep were used in a partially replicated 4 x 4 Latin square to evaluate the effects of 4 diets on microbial synthesis, microbial populations, and ruminal digestion. The experimental diets had forage to concentrate ratios (F:C; DM basis) of 70:30 (HF) or 30:70 (HC) with alfalfa hay (A) or grass hay (G) as forage and were designated as HFA, HCA, HFG, and HCG. The concentrate was based on barley, gluten feed, wheat middlings, soybean meal, palmkern meal, wheat, corn, and mineral-vitamin premix in the proportions of 22, 20, 20, 13, 12, 5, 5, and 3%, respectively (as-is basis). Sheep were fed the diets at a daily rate of 56 g/kg of BW(0.75) to minimize feed selection. High-concentrate diets resulted in greater (P < 0.001) total tract apparent OM digestibility compared with HF diets, but no differences were detected in NDF digestibility. Ruminal digestibility of OM, NDF, and ADF was decreased by increasing the proportion of concentrate, but no differences between forages were detected. Compared with sheep fed HF diets, sheep receiving HC diets had less ruminal pH values and acetate proportions, but greater butyrate proportions. No differences among diets were detected in numbers of cellulolytic bacteria, but protozoa numbers were less (P = 0.004) and total bacteria numbers tended (P = 0.08) to be less for HC diets. Carboxymethylcellulase, xylanase, and amylase activities were greater for HC compared with HF diets, with A diets showing greater (P = 0.008) carboxymethylcellulase activities than G diets. Retained N ranged from 28.7 to 37.9% of N intake and was not affected by F:C (P = 0.62) or the type of forage (P = 0.31). Microbial N synthesis and its efficiency was greater (P < 0.001) for HC diets compared with HF diets. The results indicate that concentrates with low cereal content can be included in the diet of sheep up to 70% of the diet without detrimental effects on ruminal activity, microbial synthesis efficiency, and N losses.

Three detachment procedures (DP) were evaluated for their ability to remove particle-associated microbes from digesta in Rusitec fermenters fed a 30:70 alfalfa hay:concentrate diet. Forage and concentrate were incubated in separate nylon bags, and incubation residues were treated independently. Microbial biomass was labeled with (15)NH(4)Cl. Treatments were 1) MET: residues were incubated at 38 degrees C for 15 min with saline solution (0.9% NaCl) containing 0.1% methylcellulose with continuous shaking; 2) STO: residues were mixed with cold saline solution and homogenized with a stomacher for 5 min at 230 revolutions per min; and 3) FRE: residues were immediately frozen at -20 degrees C for 72 h, thawed at 4 degrees C, mixed with saline solution, and subjected to STO procedure. Common to all treatments was storing at 4 degrees C for 24 h after the treatment, homogenization, filtration, and resuspension of residues 2 times in the treatment solutions. Microbial pellets were obtained by centrifugation, and microbial removal was estimated indirectly by measuring removal of (15)N. The PCR-single-stranded conformation polymorphism analysis of the 16S ribosomal DNA was used to analyze the similarity between microbial communities attached to the substrate and those in the pellet obtained after each DP. There were no feed x DP interactions (P = 0.16 to 0.96) for any variable, except for N content in microbial pellets (P = 0.02). Detaching efficiency (P = 0.004) and total recovery (P = 0.01) were affected by DP, with STO showing the greatest values (mean values across substrates of 64.1% for detaching efficiency and 58.3% for total recovery) and MET the least values (57.0 and 51.8%). Similarity index between the microbes attached to substrates and those in the pellets were affected (P = 0.02) by DP, with MET showing greater (P < 0.02) values (84.0 and 86.4% for forage and concentrate, respectively) than FRE (72.5 and 67.8%) and STO having intermediate values (77.1 and 82.4%). There were no differences (P = 0.70) among particle-associated microbe pellets in their N content, but MET pellets had greater (P < 0.05) (15)N enrichments than those obtained by STO and FRE. Although STO was the most effective method to detach ruminal microbes from concentrate and forage, MET produced pellets with the greatest similarity to the microbial communities attached to the substrates and therefore could be considered the most appropriate DP method for treating digesta from Rusitec fermenters.

Six rumen-fistulated Merino sheep were used in a crossover design experiment to evaluate the effects of an exogenous fibrolytic enzyme preparation (12 g/d; ENZ), delivered directly into the rumen, on diet digestibility, ruminal fermentation, and microbial protein synthesis. The enzyme contained endoglucanase and xylanase activities. Sheep were fed a mixed grass hay:concentrate (70:30; DM basis) diet at a daily rate of 46.1 g/kg of BW 0.75 . Samples of grass hay were incubated in situ in the rumen of each sheep to measure DM and NDF degradation. The supplementation with ENZ did not affect diet digestibility (P = 0.30 to 0.66), urinary excretion of purine derivatives (P = 0.34), ruminal pH (P = 0.46), or concentrations of NH 3 -N (P = 0.69) and total VFA (P = 0.97). In contrast, molar proportion of propionate were greater (P = 0.001) and acetate:propionate ratio was lower (P < 0.001) in ENZ-supplemented sheep. In addition, ENZ supplementation tended to increase (P = 0.06) numbers of cellulolytic bacteria at 4 h after feeding. Both the ruminally insoluble potentially degradable fraction of grass hay DM and its fractional rate of degradation were increased (P = 0.002 and 0.05, respectively) by ENZ treatment. Supplementation with ENZ also increased (P = 0.01 to 0.02) effective and potential degradability of grass hay DM and NDF. Ruminal fluid endoglucanase and xylanase activities were greater (P < 0.001 and 0.03, respectively) in ENZ-supplemented sheep than in control animals. It was found that ENZ supplementation did not affect either exoglucanase (P = 0.12) or amylase (P = 0.83) activity. The results indicate that supplementing ENZ directly into the rumen increased the fibrolytic activity and stimulated the growth of cellulolytic bacteria without a prefeeding feed-enzyme interaction.

Two incubation runs were carried out with a Rusitec system to investigate the effects of 2 exogenous pure cellulases on ruminal microbial growth and fermentation of a 70:30 grass hay:concentrate (DM basis) substrate. The substrate was sprayed with buffer (control; pH = 6.5), a cellulase from Trichoderma longibrachiatum (TRI), a cellulase from Aspergillus niger (ASP), or a 1:1 mixture of both cellulases (MIX) 24 h before being placed in the fermenters. Enzymes were applied at a rate of 30 endoglucanase units/g of substrate DM. Treating the substrate with enzymes reduced substrate NDF and ADF content (P < 0.001 to P = 0.002) and increased DM, NDF, and ADF disappearance after 6 and 24 h of incubation (P < 0.001 to P = 0.004) but not after 48 h of incubation. Daily VFA production was increased (P = 0.004) by 15, 9, and 15% for TRI, ASP, and MIX, respectively, with half of the increase being due to production of acetate. All enzyme treatments augmented (P = 0.009) methane production, but none of them altered the methane:VFA ratio (P = 0.70). There were no differences (P = 0.80) among treatments in the daily flow of solid-associated microorganisms, as measured using 15 N as a microbial marker. Although the TRI and MIX treatments increased (P < 0.05) the daily flow of liquid-associated microorganisms and the proportion of microbial N in the solid residue after 48 h of incubation, no effects were observed (P = 0.92 and P = 0.95, respectively) for the ASP treatment. The results show that the TRI and MIX treatments enhanced in vitro fermentation by increasing substrate fiber degradation, VFA production, and ruminal microbial growth. The lack of differences between TRI and MIX in most of the measured variables indicates that treating the substrate with a mixture of both cellulases did not further improve the effects of the TRI treatment.

The objective of this study was to evaluate the effects of malate supplementation on growth rate, feed efficiency, and diet digestibility in growing lambs. Twenty-four Merino lambs with a mean BW of 15.3 +/- 0.22 kg were divided into 3 homogenous groups. Each group was randomly allocated to 1 of 3 malate (16% disodium malate:84% calcium malate) levels: 0 (control), 4 (MAL-4), or 8 (MAL-8) g/kg of concentrate. Lambs were fed concentrate and barley straw ad libitum for 35 d. After a 20-d period, diet digestibility was determined, and microbial N flow at the duodenum was estimated from the urinary excretion of purine derivatives. Blood samples were taken on d 0, 20, and 35. On d 35, lambs were slaughtered and ruminal fluid samples were collected. There were no effects (P = 0.18 to P = 0.95) of malate on concentrate or straw intake, ADG, carcass yield, and apparent digestibility of OM, CP, NDF, or ADF. Malate supplementation did not influence (P = 0.80) the daily urinary excretion of total purine derivatives, and therefore there were no treatment effects (P = 0.77) on estimated microbial N flow at the duodenum. No differences (P > 0.05) among treatments were observed for plasma concentrations of glucose, cholesterol, triglycerides, urea-N, lactate, or VFA, but malate addition increased (P = 0.003) the molar proportion of butyrate in ruminal fluid (4.29, 6.14, and 5.45% of total VFA for control, MAL-4 and MAL-8, respectively). The use of malate as a feed additive under the conditions of the current study did not influence diet intake or digestion, and consequently did not improve lamb performance.

The aim of this study was to compare automated ribosomal intergenic spacer analysis (ARISA) and denaturing gradient gel electrophoresis (DGGE) techniques to assess bacterial diversity in the rumen of sheep. Sheep were fed 2 diets with 70% of either alfalfa hay or grass hay, and the solid (SOL) and liquid (LIQ) phases of the rumen were sampled immediately before feeding (0 h) and at 4 and 8 h postfeeding. Both techniques detected similar differences between forages, with alfalfa hay promoting greater (P0.05) bacterial diversity than grass hay. In contrast, whereas ARISA analysis showed a decrease (P0.05) of bacterial diversity in SOL at 4 h postfeeding compared with 0 and 8 h samplings, no variations (P0.05) over the postfeeding period were detected by DGGE. The ARISA technique showed lower (P0.05) bacterial diversity in SOL than in LIQ samples at 4 h postfeeding, but no differences (P0.05) in bacterial diversity between both rumen phases were detected by DGGE. Under the conditions of this study, the DGGE was not sensitive enough to detect some changes in ruminal bacterial communities, and therefore ARISA was considered more accurate for assessing bacterial diversity of ruminal samples. The results highlight the influence of the fingerprinting technique used to draw conclusions on factors affecting ruminal bacterial diversity.

Four ruminally cannulated sheep were used in a crossover design to assess the postprandial changes of fiber-degrading microbes in the solid phase of the rumen of sheep fed 2 high-forage diets. The diets had forage:concentrate ratio of 70:30 (DM basis) and either alfalfa (Medicago sativa) hay (AL) or grass hay (GR) as forage (FOR). Sheep were fed twice daily, and samples from solid rumen digesta were taken at 0, 4, and 8 h after the morning feeding. Postprandial changes of DNA concentrations of all determined microbial populations were similar for the 2 diets. Samples taken at 4 h after feeding had lesser (P0.05) concentrations of total bacterial DNA determined with real-time PCR and bacterial diversity and greater (P0.05) protozoal DNA concentrations, relative abundance of fungal, Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus DNA compared with those taken at 0 and 8 h. No effect (P = 0.41 to 0.76) of FOR was detected either on concentrations of bacterial and protozoal DNA or the relative abundance of the 2 Ruminococcus DNA, but GR diet promoted greater (P0.001) relative abundance of F. succinogenes and fungal DNA compared with AL diet. Fibrobacter succinogenes was the most abundant (P0.05) of the 3 cellulolytic bacteria for both diets, with no differences (P0.05) between the 2 Ruminococcus species. Rumen pH and carboxymethylcellulase, Avicelase, and amylase activities were not affected (P = 0.15 to 0.69) by FOR, but xylanase activity was greater (P = 0.01) for GR diet. The influence of FOR on microbial communities in ruminal solid digesta was more evident in the first hours after feeding than at later times after feeding, which highlights the influence of sampling time when investigating dietary effects on rumen function and microbial populations.

The objective of this study was to compare N balance, microbial N flow (MNF) estimated from purine derivatives (PD) urinary excretion, and its variation when estimated using purine bases:N ratios in liquid associated bacteria (LAB) from models reported in the literature (MNF - response models) or measured ratios in liquid and solid-associated bacterial (SAB) pellets (MNF-LAB+SAB), diet digestibility, and rumen fermentation variables in sheep and goats fed 3 different practical, quality diets to study interspecies differences concerning N use as accurately as possible. Four mature female Merino sheep and 4 mature female Granadina goats, each fitted with a ruminal cannula, were used in 3 × 3 Latin square design with an extra animal. Two experimental diets had a forage-to-concentrate ratio of 70:30 (DM basis) with alfalfa hay (ALC) or grass hay (GRC) as forage, and the third diet contained 70% concentrate and 30% alfalfa hay (CAL). All animals were fed the diets at a daily rate of 56 g/kg BW(0.75) to minimize feed selection. Digestibility of nutrients was similar (P = 0.16 to 0.88) in the 2 species, but some animal species × diet interactions (P = 0.01 to 0.04) were detected. There were small differences between the fermentation patterns of both animal species. Goats showed decreased VFA concentrations (P = 0.005) and butyrate proportions (P = 0.04), and greater acetate proportions (P = 0.02) compared with sheep, whereas N intake and percentage of N intake excreted in feces were similar in both species (P = 0.58 and 0.15, respectively), the percentage excreted via the urine was greater in goats compared with sheep (P0.001). As a consequence, sheep had greater (P0.001) N retention than goats (averaged across diets, 32.6% and 16.1% of N intake, respectively). There were no differences (P = 0.95) between animal species in total PD excretion, but goats showed a greater excretion of allantoin (P = 0.01) and decreased excretion of xanthine (P = 0.008) and hypoxanthine (P = 0.007) compared with sheep. In general, differences between sheep and goats were more pronounced for the medium-quality diet (GRC) compared with those of high-quality diet (ALC and CAL). The greater urinary losses in goats would indicate a greater contribution of goats to N environmental contamination compared with sheep.

Six rumen-fistulated Merino sheep were used in a crossover design experiment to evaluate the effects of an exogenous fibrolytic enzyme preparation (12 g/d; ENZ), delivered directly into the rumen, on diet digestibility, ruminal fermentation, and microbial protein synthesis. The enzyme contained endoglucanase and xylanase activities. Sheep were fed a mixed grass hay:concentrate (70:30; DM basis) diet at a daily rate of 46.1 g/kg of BW(0.75). Samples of grass hay were incubated in situ in the rumen of each sheep to measure DM and NDF degradation. The supplementation with ENZ did not affect diet digestibility (P = 0.30 to 0.66), urinary excretion of purine derivatives (P = 0.34), ruminal pH (P = 0.46), or concentrations of NH(3)-N (P = 0.69) and total VFA (P = 0.97). In contrast, molar proportion of propionate were greater (P = 0.001) and acetate:propionate ratio was lower (P0.001) in ENZ-supplemented sheep. In addition, ENZ supplementation tended to increase (P = 0.06) numbers of cellulolytic bacteria at 4 h after feeding. Both the ruminally insoluble potentially degradable fraction of grass hay DM and its fractional rate of degradation were increased (P = 0.002 and 0.05, respectively) by ENZ treatment. Supplementation with ENZ also increased (P = 0.01 to 0.02) effective and potential degradability of grass hay DM and NDF. Ruminal fluid endoglucanase and xylanase activities were greater (P0.001 and 0.03, respectively) in ENZ-supplemented sheep than in control animals. It was found that ENZ supplementation did not affect either exoglucanase (P = 0.12) or amylase (P = 0.83) activity. The results indicate that supplementing ENZ directly into the rumen increased the fibrolytic activity and stimulated the growth of cellulolytic bacteria without a prefeeding feed-enzyme interaction.

Two incubation runs were carried out with a Rusitec system to investigate the effects of 2 exogenous pure cellulases on ruminal microbial growth and fermentation of a 70:30 grass hay:concentrate (DM basis) substrate. The substrate was sprayed with buffer (control; pH = 6.5), a cellulase from Trichoderma longibrachiatum (TRI), a cellulase from Aspergillus niger (ASP), or a 1:1 mixture of both cellulases (MIX) 24 h before being placed in the fermenters. Enzymes were applied at a rate of 30 endoglucanase units/g of substrate DM. Treating the substrate with enzymes reduced substrate NDF and ADF content (P0.001 to P = 0.002) and increased DM, NDF, and ADF disappearance after 6 and 24 h of incubation (P0.001 to P = 0.004) but not after 48 h of incubation. Daily VFA production was increased (P = 0.004) by 15, 9, and 15% for TRI, ASP, and MIX, respectively, with half of the increase being due to production of acetate. All enzyme treatments augmented (P = 0.009) methane production, but none of them altered the methane:VFA ratio (P = 0.70). There were no differences (P = 0.80) among treatments in the daily flow of solid-associated microorganisms, as measured using 15N as a microbial marker. Although the TRI and MIX treatments increased (P0.05) the daily flow of liquid-associated microorganisms and the proportion of microbial N in the solid residue after 48 h of incubation, no effects were observed (P = 0.92 and P = 0.95, respectively) for the ASP treatment. The results show that the TRI and MIX treatments enhanced in vitro fermentation by increasing substrate fiber degradation, VFA production, and ruminal microbial growth. The lack of differences between TRI and MIX in most of the measured variables indicates that treating the substrate with a mixture of both cellulases did not further improve the effects of the TRI treatment.

The objective of this study was to evaluate the effects of malate supplementation on growth rate, feed efficiency, and diet digestibility in growing lambs. Twenty-four Merino lambs with a mean BW of 15.3 +/- 0.22 kg were divided into 3 homogenous groups. Each group was randomly allocated to 1 of 3 malate (16% disodium malate:84% calcium malate) levels: 0 (control), 4 (MAL-4), or 8 (MAL-8) g/kg of concentrate. Lambs were fed concentrate and barley straw ad libitum for 35 d. After a 20-d period, diet digestibility was determined, and microbial N flow at the duodenum was estimated from the urinary excretion of purine derivatives. Blood samples were taken on d 0, 20, and 35. On d 35, lambs were slaughtered and ruminal fluid samples were collected. There were no effects (P = 0.18 to P = 0.95) of malate on concentrate or straw intake, ADG, carcass yield, and apparent digestibility of OM, CP, NDF, or ADF. Malate supplementation did not influence (P = 0.80) the daily urinary excretion of total purine derivatives, and therefore there were no treatment effects (P = 0.77) on estimated microbial N flow at the duodenum. No differences (P0.05) among treatments were observed for plasma concentrations of glucose, cholesterol, triglycerides, urea-N, lactate, or VFA, but malate addition increased (P = 0.003) the molar proportion of butyrate in ruminal fluid (4.29, 6.14, and 5.45% of total VFA for control, MAL-4 and MAL-8, respectively). The use of malate as a feed additive under the conditions of the current study did not influence diet intake or digestion, and consequently did not improve lamb performance.

Four different detachment methods were evaluated for their ability to remove particle-associated microorganisms (PAM) from ruminal digesta in semicontinuous fermenters fed two diets differing in their forage:concentrate ratio (80:20 [C20] and 20:80 [C80]). In the methylcellulose method, ruminal digesta was incubated at 38 degrees C for 15 min with saline solution containing 0.1% methylcellulose before being stored at 4 degrees C for 24 h. In the other procedures, samples were incubated with 0.1% methylcellulose before storage for 24 h at 4 degrees C in different solutions (pH = 2): 1) saline solution with 0.1% Tween 80; 2) saline solution with 0.1% Tween 80 and 1% tertiary butanol; and 3) saline solution with 0.1% Tween 80, 1% methanol, and 1% tertiary butanol. Common to all treatments was subsequent homogenization, followed by filtration and resuspension of the residue five times in the treatment solutions. Microbial removal was estimated indirectly by measuring removal of 15N. There were no differences (P0.05) among detachment procedures, neither in the detaching efficiency (mean values of 79.7 and 88.1% for C20 and C80 diets, respectively) nor in the total recovery of PAM (54.9 and 34.9% for C20 and C80, respectively). There were no differences (P0.05) among PAM pellets obtained by the different detachment procedures in their N content, purine bases (PB) concentration, or PB:N ratio. For the C80 diet, 15N enrichment was greater (P0.05) in PAM pellets obtained with methylcellulose than in those obtained by the other methods. However, there were no differences (P0.05) due to the detachment procedure in the values of daily microbial growth estimated using as reference the different PAM pellets. The PAM pellets for diet C20 presented greater (P0.01) N content and lower (P0.01) PB concentration than those for diet C80 (mean values of 74.3 vs 49.1 mg of N/g of dry matter, and 22.8 vs 26.0 micromol PB/mg of dry matter, respectively). Daily microbial growth was greater (P0.05) for the C80 diet than for the C20 diet (121 vs 114 mg of microbial N, respectively). Results suggest that the treatment of ruminal digesta with a saline solution with 0.1% methylcellulose at 38 degrees C for 15 min combined with homogenizing and chilling at 4 degrees C for 24 h removed a major proportion of PAM, although further research is needed to decrease microbial losses during the isolation process.