RESUMO
The objective was to evaluate the effects of urea with post-ruminal absorption in the supplementation of growing Nellore cattle reared on pasture during a seasonal period. For the study, two experiments were conducted. In experiment 1, rumen and blood parameters were evaluated using eight rumen-cannulated Nellore bulls with initial body weight (BW) of 763 ± 44 kg, distributed in a double Latin square 4 × 4. In experiment 2, 120 Nellore steers with initial BW of 380 ± 35 kg were used for performance evaluation, distributed in a randomized block design (blocking factor or initial BW). The evaluated treatments were 1: (TP-U) (control) = supplement with 24% crude protein (CP) containing urea as a source of non-protein nitrogen (NPN; 3%) and soybean meal, 2: (TP-PRU) = 24% CP supplement containing post-ruminal urea (PRU; 3.6%) and soybean meal; 3: (NPN-U-PRU) = 24% CP supplement containing urea + post-ruminal urea (U = 3% and PRU = 3.9%), without soybean meal; 4: (NPN-PRU) = supplement with 24% CP containing post-ruminal urea (7.5%), without soybean meal. The supplement was offered at 3 g/kg BW per animal, daily, once a day. All animals were kept on Urochloa brizantha cv. Marandu pasture. Statistical analyses were performed using the SAS PROC MIXED, and the data were evaluated by the following contrasts: C1 = TP-U/TP-PRU vs. NPN-U-PRU/NPN-PRU (Soybean meal replacement by NPN); C2 = TP-U vs. TP-PRU (conventional urea vs. post-immune urea); C3 = NPN-U-PRU vs. NPN-PRU (low and high post-ruminal urea-PRU level). The digestibility of dry matter, organic matter, and NDF was lower when soybean meal was replaced by non-protein nitrogen, also being different between the levels of post-ruminal urea used in the supplement. Ruminal pH was different when soybean meal was replaced by NPN (p = 0.003). Total concentration of short-chain fatty acids, concentrations of isobutyrate (p = 0.003), valerate (p = 0.001), and isovalerate (p = 0.001) were different, and blood urea was different when soybean meal was replaced by NPN (p = 0.006). Simpson's diversity index was higher in the rumen of animals supplemented with TP-U than in those supplemented with TP-PRU (p = 0.05). A total of 27 phyla, 234 families, and 488 genera were identified. Nitrospirota and Gemmatimonadota phyla were detected just in the rumen of steers supplemented with TP-PRU. The performance (final BW, weight gain and gain per area) of the animals was different, being higher (p = 0.04) in animals supplemented with soybean meal, compared to NPN. The removal of soybean meal from the supplement and its replacement with either conventional urea plus post-ruminal urea or only post-ruminal urea compromises the performance of the animals. The lower the post-ruminal urea inclusion level, the lower the apparent digestibility of dry matter, organic matter, and NDF, when compared to animals supplemented with higher levels.
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This study aimed to evaluate the microbiological and physicochemical characteristics of the ruminal fluid and histological characteristics of the gastrointestinal tract (GIT) of sheep on a high-grain diet containing the probiotic fungi Aspergillus terreus and Rhizomucor spp. The study included four treatment groups (without probiotic, with Rhizomucor spp., with Aspergillus terreus, and with a mixture of both fungi), and two types of corn (ground/whole), in a Completely Randomized Design (CRD) arranged in 4 x 2 factorial design. Santa Inês x Dorper lambs were housed in eight pens with five lambs each for 75 days. Rumen fluid was collected to study the rumen microbiological profile, macroscopic characteristics, ammonia nitrogen concentration, and microbiological activity. In addition, GIT samples were taken for histological analysis. Fluid analyses showed that the animals presented a low acidosis index. The samples presented a predominantly aromatic odor and blackish-brown color, indicating a neutral pH and high microbial activity. The rumen pH differed (P < 0.05) according to the level of processed corn consumed, being higher for ground grain corn (GGC). There was no difference for any of the microbiological communities analyzed (P > 0.05) (Lac+ and Lac- bacteria, fungi, yeasts, and protozoa). Six genera of facultative anaerobic fungi were identified in 15 observations. Cladosporium spp. was the most prevalent genus (46.66%), followed by Aspergillus spp. (26,66%). The width of the base of rumen papillae showed significant correlation being greater for GCG (P < 0.05) with Rhizomucor and for the control (P < 0.05). The rumen fluid of sheep on a high-grain diet with added Aspergillus terreus and Rhizomucor spp. showed no microbiological and physicochemical changes.
Objetivou-se avaliar as características microbiológicas e físico-químicas do fluido ruminal e histológicas do trato gástrico intestinal (TGI) de ovinos sob dieta de alto grão com probiótico fungos Aspergillus terreus e/ou Rhizomucor spp. Analisou-se quatro probióticos (sem inóculos, com Rhizomucor spp., com Aspergillus terreus e com mistura dos dois fungos) e dois processamentos de milho (moído/inteiro), em fatorial 4x2 em em Delineamento Inteiramente Casualizados (DIC). Borregos Santa Inês/Dorper foram alojados em oito baias com cinco borregos em cada, durante 75 dias. Coletou-se fluido ruminal para o estudo do perfil microbiológico do rúmen, da característica macroscópica, da concentração de nitrogênio amoniacal e da atividade microbiológica, além dos fragmentos do TGI para análises histológicas. Pelas análises dos fluidos, os animais apresentaram baixo índice de acidose. O odor aromático e a cor castanho-enegrecido predominaram, o que caracteriza ambiente com pH neutro. As amostras do fluido apresentaram alta atividade microbiana. O pH ruminal diferenciou-se (P<0,05) quanto ao tipo de processamento, sendo maior para milho grão moído (MGM). Não houve diferença para nenhuma das comunidades microbiológicas analisadas (P>0,05) (bactérias Lac+ e Lac-, fungos, leveduras e protozoários). Seis gêneros de fungos anaeróbicos facultativos foram identificados num total de 15 observações. O Cladosporium spp. foi o gênero mais prevalente (46,66%), seguido do Aspergillus spp. (26,66%). A largura da base das papilas ruminais apresentou interação significativa, sendo maior para MGM (P<0,05) com Rhizomucor e o controle (P<0,05). O fluido ruminal de ovinos sob dieta de alto concentrado de grão com adição dos fungos Aspergillus terreus e Rhizomucor spp. não tiveram afetadas as características microbiológicas e físico-químicas.
Assuntos
Animais , Aspergillus/patogenicidade , Rúmen/microbiologia , Ruminantes/crescimento & desenvolvimento , Cladosporium/patogenicidade , Probióticos/efeitos adversos , Rhizomucor/patogenicidade , Trato Gastrointestinal/anatomia & histologiaRESUMO
The continuous trend for a narrowing margin between feed cost and milk prices across dairy farms in the United States highlights the need to improve and maintain feed efficiency. Yeast culture products are alternative supplements that have been evaluated in terms of milk performance and feed efficiency; however, less is known about their potential effects on altering rumen microbial populations and consequently rumen fermentation. Therefore, the objective of this study was to evaluate the effect of yeast culture supplementation on lactation performance, rumen fermentation profile, and abundance of major species of ruminal bacteria in lactating dairy cows. Forty mid-lactation Holstein dairy cows (121 ± 43 days in milk; mean ± standard deviation; 32 multiparous and 8 primiparous) were used in a randomized complete block design with a 7-d adaptation period followed by a 60-d treatment period. Cows were blocked by parity, days in milk, and previous lactation milk yield and assigned to a basal total mixed ration (TMR; 1.6 Mcal/kg of dry matter, 14.6% crude protein, 21.5% starch, and 38.4% neutral detergent fiber) plus 114 g/d of ground corn (CON; n = 20) or basal TMR plus 100 g/d of ground corn and 14 g/d of yeast culture (YC; n = 20; Culture Classic HD, Cellerate Yeast Solutions, Phibro Animal Health Corp.). Treatments were top-dressed over the TMR once a day. Cows were individually fed 1 × /d throughout the trial. Blood and rumen fluid samples were collected in a subset of cows (n = 10/treatment) at 0, 30, and 60 d of the treatment period. Rumen fluid sampled via esophageal tubing was analyzed for ammonia-N, volatile fatty acids (VFA), and ruminal bacteria populations via quantitative PCR amplification of 16S ribosomal DNA genes. Milk yield was not affected by treatment effects. Energy balance was lower in YC cows than CON, which was partially explain by the trend for lower dry matter intake as % body weight in YC cows than CON. Cows fed YC had greater overall ruminal pH and greater total VFA (mM) at 60 d of treatment period. There was a contrasting greater molar proportion of isovalerate and lower acetate proportion in YC-fed cows compared with CON cows. Although the ruminal abundance of specific fiber-digesting bacteria, including Eubacterium ruminantium and Ruminococcus flavefaciens, was increased in YC cows, others such as Fibrobacter succinogenes were decreased. The abundance of amylolytic bacteria such as Ruminobacter amylophilus and Succinimonas amylolytica were decreased in YC cows than CON. Our results indicate that the yeast culture supplementation seems to promote some specific fiber-digesting bacteria while decreasing amylolytic bacteria, which might have partially promoted more neutral rumen pH, greater total VFA, and isovalerate.
Assuntos
Lactação , Rúmen , Ração Animal/análise , Animais , Bovinos , Dieta/veterinária , Suplementos Nutricionais , Digestão , Eubacterium , Feminino , Fermentação , Fibrobacter , Leite , Gravidez , Rúmen/metabolismo , Ruminococcus , Saccharomyces cerevisiae , SuccinivibrionaceaeRESUMO
Rumen development depends on the intake of solid food that is fermented into volatile fatty acids that stimulate the development of the rumen papillae in calves. The starter feeding can promote the growth of papillae in the rumen and as a consequence an earlier weaning. We evaluated the effects of calf starter on ruminal development, and productive response of lactating bull calves raised for meat in the tropics. Twelve male Brahman × Swiss American cross beef calves from a dual-purpose system were randomly assigned two treatments with six animals per treatment: milk-fed calves + Taiwan grass (Pennisetum purpureum, MT) and MT + calf starter, (MTS). Feed intake and growth were measured at 7-day intervals throughout until 210 d of age. At 90 days old, three calves from each treatment were harvested, and fluid and ruminal tissues were collected from the cranial, ventral, dorsal, and dorsal blind ruminal sacs for measurements of many papillaes per cm2 (NP), papillae length (LP) and papillae width (WP). Ruminal bacterial genotype identification was determined by amplicon generation with the Illumina platform. Calf starter-improved weight (Live weight, LW) and average weight gain (ADG) and NP, but, LP and WP was similar in both treatments (p 0.05). In calves with starter feed treatment, we observed the bacteria Desulfonauticus autotrophicus sp. nov.that was not previously reported in ruminants. Use of calf starter showed benefit for calves with improved feed intake and rumen development because promoted a greater number of rumen papillae.(AU)
O desenvolvimento do rumen depende da ingestão de alimentos sólidos fermentados em ácidos graxos voláteis que estimulam o desenvolvimento das papilas de rúmen em bezerros. A alimentação inicial pode promover o crescimento das papilas no rúmen e, como consequência, um desmame mais cedo. Avaliamos os efeitos da concentrado de bezerros no desenvolvimento ruminal, e a resposta produtiva dos bezerros lactantes criados para carne nos trópicos. Doze bezerros de carne bovina cruza Brahman × suíço-americano machos de de um sistema de dupla finalidade foram aleatoriamente atribuídos a dois tratamentos, com seis animais por tratamento: bezerros alimentados com leite + grama taiwanesa (Pennisetumpurpureum, MT) e MT+ concentrado de bezerro, (MTS). A ingestão de ração e o crescimento foram medidos. Aos 90 dias de idade, três bezerros de cada tratamento foi amostrado, e foram coletados tecidos fluidos dos sacos ruminais cranianos, ventral, dorsal e dorsal cegos para medições do número de papilas por cm2 (NP), comprimento das papilas (LP) e largura da papila (PM). A identificação do genótipo das bactérias ruminais foi determinada pela geração de amplicon com a plataforma de ilumine. O concentrado de bezerro melhorou o peso (LW) e o ganho diário médio (AGD) e NP, mas, LP e WP foram semelhantes nos dois tratamentos. Bezerros em MTS uma bactéria não encontrada anteriormente em ruminantes Desulfonauticus autotrophicus sp. nov. foi detectado. O uso de concentrado de bezerro mostrou benefício para bezerros com melhor ingestão de ração e desenvolvimento de rúmen, pois promove um maior número de papilas de rúmen.(AU)
Assuntos
Animais , Masculino , Bovinos , Rúmen/crescimento & desenvolvimento , Dieta/veterináriaRESUMO
ABSTRACT: Rumen development depends on the intake of solid food that is fermented into volatile fatty acids that stimulate the development of the rumen papillae in calves. The starter feeding can promote the growth of papillae in the rumen and as a consequence an earlier weaning. We evaluated the effects of calf starter on ruminal development, and productive response of lactating bull calves raised for meat in the tropics. Twelve male Brahman × Swiss American cross beef calves from a dual-purpose system were randomly assigned two treatments with six animals per treatment: milk-fed calves + Taiwan grass (Pennisetum purpureum, MT) and MT + calf starter, (MTS). Feed intake and growth were measured at 7-day intervals throughout until 210 d of age. At 90 days old, three calves from each treatment were harvested, and fluid and ruminal tissues were collected from the cranial, ventral, dorsal, and dorsal blind ruminal sacs for measurements of many papillaes per cm2 (NP), papillae length (LP) and papillae width (WP). Ruminal bacterial genotype identification was determined by amplicon generation with the Illumina platform. Calf starter-improved weight (Live weight, LW) and average weight gain (ADG) and NP, but, LP and WP was similar in both treatments (p < 0.05). In calves with starter feed treatment, we observed the bacteria Desulfonauticus autotrophicus sp. nov.that was not previously reported in ruminants. Use of calf starter showed benefit for calves with improved feed intake and rumen development because promoted a greater number of rumen papillae.
RESUMO: O desenvolvimento dorumen depende da ingestão de alimentos sólidos fermentados em ácidos graxos voláteis que estimulam o desenvolvimento das papilas de rúmen em bezerros. A alimentação inicial pode promover o crescimento das papilas no rúmen e, como consequência, um desmame mais cedo. Avaliamos os efeitos da concentrado de bezerros no desenvolvimento ruminal, e a resposta produtiva dos bezerros lactantes criados para carne nos trópicos. Doze bezerros de carne bovina cruza Brahman × suíço-americano machos de de um sistema de dupla finalidade foram aleatoriamente atribuídos adois tratamentos, com seis animais por tratamento: bezerros alimentados com leite + grama taiwanesa (Pennisetumpurpureum, MT) e MT+ concentrado de bezerro, (MTS). A ingestão de ração e o crescimento foram medidos. Aos 90 dias de idade, três bezerros de cada tratamento foi amostrado, e foram coletados tecidos fluidos dos sacos ruminais cranianos, ventral, dorsal e dorsal cegos para medições do número de papilas por cm2 (NP), comprimento das papilas (LP) e largura da papila (PM). A identificação do genótipo das bactérias ruminais foi determinada pela geração de amplicon com a plataforma de ilumine. Oconcentrado de bezerro melhorou o peso (LW) e o ganho diário médio (AGD) e NP, mas, LP e WP foram semelhantes nos dois tratamentos. Bezerros em MTS uma bactéria não encontrada anteriormente em ruminantes Desulfonauticus autotrophicus sp. nov. foi detectado. O uso de concentrado de bezerro mostrou benefício para bezerros com melhor ingestão de ração e desenvolvimento de rúmen, pois promove um maior número de papilas de rúmen.
RESUMO
[This corrects the article DOI: 10.3389/fmicb.2019.00614.].
RESUMO
This study investigated the long-term effects (13 months) of encapsulated nitrate supplementation (ENS) on enteric methane emissions, rumen fermentation parameters, ruminal bacteria, and diversity of archaea in grazing beef cattle. We used a total of thirty-two Nellore steers (initial BW of 197 ± 15.3 kg), 12 of which were fitted with rumen cannulas. For 13 months, the animals were maintained in 12 paddocks and fed a concentrate of ground corn, soybean meals, mineral supplements, and urea (URS) or encapsulated nitrate (EN) containing 70 g of EN/100 kg of BW (corresponding to 47 g NO3 -/100 kg BW). Encapsulated nitrate supplementation resulted in similar forage, supplement and total DMI values as URS (P > 0.05), but ENS tended to increase (+48 g/d; P = 0.055) average daily weight gain. Daily reductions in methane emissions (-9.54 g or 18.5%) were observed with ENS when expressed as g of CH4/kg of forage dry matter intake (fDMI) (P = 0.037). Lower concentrations of NH3-N and a higher ruminal pH were observed in ENS groups 6 h after supplementation (P < 0.05). Total VFA rumen concentration 6 h (P = 0.009) and 12 h after supplementation with EN resulted in lower acetate concentrations in the rumen (P = 0.041). Steers supplemented with EN had a greater ruminal abundance of Bacteroides, Barnesiella, Lactobacillus, Selenomonas, Veillonella, Succinimonas, Succinivibrio, and Duganella sp. (P < 0.05), but a lower abundance of Methanobrevibacter sp. (P = 0.007). Strong negative correlations were found between daily methane emissions and Proteobacteria, Erysipelotrichaceae, Prevotellaceae, and Roseburia, Kandleria, Selenomonas, Veillonella, and Succinivibrio sp. (P < 0.05) in the rumen of ENS steers. Encapsulated nitrate is a feed additive that persistently affects enteric methane emission in grazing steers, thereby decreasing Methanobrevibacter abundance in the rumen. In addition, ENS can promote fumarate-reducer and lactate-producer bacteria, thereby reducing acetate production during rumen fermentation.
RESUMO
Two experiments were conducted to evaluate the effects of inclusion of crude glycerin (CG) in the supplement (0, 70, 140, 210, and 280 g kg-¹ dry matter (DM) of supplement) of Nellore cattle grazing tropical grasses during dry season. In Experiment 1, intake, digestibility, ruminal fermentation, and the rumen microbial profile were evaluated in two simultaneous 5 × 5 Latin squares, using 10 ruminally cannulated Nellore steers (408.8 ± 38.5 kg of body weight (BW)). In Experiment 2, cattle growth performance was evaluated in 50 young Nellore bulls (279.52 ± 16.3 kg of BW) distributed in a randomized complete block design. The increasing inclusion of CG did not affect intake (P= 0.813), diet digestibility (P = 0.895), however linearly increased pH (P=0.001), butyrate concentration (P < 0.001) and Fibrobacter succinogenes (P=0.003) population. CG inclusion linearly decreased total ruminal volatile fatty acids (VFA) (P < 0.001), acetate concentration (P < 0.001) and quadratically affected (P=0.009) acetate: propionate ratio. In experiment 2, the inclusion of CG quadratically affected DM intake (DMI) (P=0.005), DM total-tract apparent digestibility (P < 0.001), linearly increased additional gain (P > 0.001), average daily gain (P > 0.001) and feed efficiency (P > 0.001). CG in the supplement of Nellore steers grazing tropical grass during dry season doesnt affect intake and digestibility but alters ruminal fermentation, without negative effect on relative proportion of cellulolytic bacteria population. The increasing replacement of corn grain by CG in the supplement of pasture-raised growing Nellore bulls (up to 280g/kg DM) improved BW gain and consequently feed efficiency.(AU)
Foram realizados dois experimentos para avaliar os efeitos da inclusão de glicerina bruta (GB) no suplemento (0, 70, 140, 210 e 280 g kg-¹ de suplemento) de bovinos Nelore pastejando gramíneas tropicais durante a estação seca. No experimento 1, o consumo, digestibilidade, fermentação ruminal e o perfil microbiano do rúmen foram avaliados em dois quadrados latinos 5x5 simultâneos, usando 10 novilhos Nelore canulados no rúmen (408,8 ± 38,5 kg de PC). No Experimento 2, o desempenho do crescimento do gado foi avaliado em 50 novilhos Nelore (279,52 ± 16,3 kg de PC) distribuídos em delineamento em blocos casualizados. A inclusão crescente de GB não afetou o consumo (P = 0,813), a digestibilidade da dieta (P = 0,895), mas aumentou linearmente o pH (P=0,001), a concentração de butirato (P < 0,001) e a população de Fibrobacter succinogenes (P = 0,003). A inclusão de GB diminuiu linearmente os ácidos graxos voláteis totais (AGVs) no rúmen (P < 0,001), a concentração de acetato (P < 0,001) e afetou quadraticamente a relação acetato: propionato (p = 0,009). No experimento 2, a inclusão de GB modificou quadraticamente o consumo de matéria seca (CMS) (P = 0,005), a digestibilidade aparente total (P < 0,001), aumentou linearmente o ganho adicional (P > 0,001), o ganho médio diário (P > 0,001) e a eficiência alimentar (P > 0,001). GB no suplemento de novilhos Nelore pastejando gramíneas tropicais durante a estação seca não afeta a ingestão e digestibilidade, mas altera a fermentação ruminal, sem efeito negativo sobre a proporção relativa de bactérias celulolíticas. A crescente substituição do grão de milho por GB no suplemento touros Nelore em crescimento criados em pastagem (até 280g / kg de DM) melhorou o ganho de peso e consequentemente a eficiência alimentar.(AU)
Assuntos
Animais , Bovinos , Glicerol , Suplementos Nutricionais , Bovinos , Ruminação Digestiva , Fermentação , Rúmen/microbiologia , Aumento de PesoRESUMO
Two experiments were conducted to evaluate the effects of inclusion of crude glycerin (CG) in the supplement (0, 70, 140, 210, and 280 g kg-¹ dry matter (DM) of supplement) of Nellore cattle grazing tropical grasses during dry season. In Experiment 1, intake, digestibility, ruminal fermentation, and the rumen microbial profile were evaluated in two simultaneous 5 × 5 Latin squares, using 10 ruminally cannulated Nellore steers (408.8 ± 38.5 kg of body weight (BW)). In Experiment 2, cattle growth performance was evaluated in 50 young Nellore bulls (279.52 ± 16.3 kg of BW) distributed in a randomized complete block design. The increasing inclusion of CG did not affect intake (P= 0.813), diet digestibility (P = 0.895), however linearly increased pH (P=0.001), butyrate concentration (P 0.001), average daily gain (P > 0.001) and feed efficiency (P > 0.001). CG in the supplement of Nellore steers grazing tropical grass during dry season doesnt affect intake and digestibility but alters ruminal fermentation, without negative effect on relative proportion of cellulolytic bacteria population. The increasing replacement of corn grain by CG in the supplement of pasture-raised growing Nellore bulls (up to 280g/kg DM) improved BW gain and consequently feed efficiency.
Foram realizados dois experimentos para avaliar os efeitos da inclusão de glicerina bruta (GB) no suplemento (0, 70, 140, 210 e 280 g kg-¹ de suplemento) de bovinos Nelore pastejando gramíneas tropicais durante a estação seca. No experimento 1, o consumo, digestibilidade, fermentação ruminal e o perfil microbiano do rúmen foram avaliados em dois quadrados latinos 5x5 simultâneos, usando 10 novilhos Nelore canulados no rúmen (408,8 ± 38,5 kg de PC). No Experimento 2, o desempenho do crescimento do gado foi avaliado em 50 novilhos Nelore (279,52 ± 16,3 kg de PC) distribuídos em delineamento em blocos casualizados. A inclusão crescente de GB não afetou o consumo (P = 0,813), a digestibilidade da dieta (P = 0,895), mas aumentou linearmente o pH (P=0,001), a concentração de butirato (P 0,001), o ganho médio diário (P > 0,001) e a eficiência alimentar (P > 0,001). GB no suplemento de novilhos Nelore pastejando gramíneas tropicais durante a estação seca não afeta a ingestão e digestibilidade, mas altera a fermentação ruminal, sem efeito negativo sobre a proporção relativa de bactérias celulolíticas. A crescente substituição do grão de milho por GB no suplemento touros Nelore em crescimento criados em pastagem (até 280g / kg de DM) melhorou o ganho de peso e consequentemente a eficiência alimentar.
Assuntos
Animais , Bovinos , Bovinos , Glicerol , Suplementos Nutricionais , Aumento de Peso , Fermentação , Ruminação Digestiva , Rúmen/microbiologiaRESUMO
The objective of this study was to determine whether a combination of crude glycerin (CG) and soyabean oil (SO) could be used to partially replace maize in the diet of Nellore steers while maintaining optimum feed utilisation. Eight castrated Nellore steers fitted with ruminal and duodenal cannulas were used in a double 4×4 Latin square design balanced for residual effects, in a factorial arrangement (A×B), when factor A corresponded to the provision of SO, and factor B to the provision of CG. Steers feed SO and CG showed similar DM intake, DM, organic matter and neutral-detergent fibre digestibility to that of steers fed diets without oil and without glycerine (P>0·05). Both diets with CG additions reduced the acetate:propionate ratio and increased the proportion of iso-butyrate, butyrate, iso-valerate and valerate (P<0·05). Steers fed diets containing SO had less total N excretion (P<0·001) and showed greater retained N expressed as % N intake (P=0·022). SO and CG diet generated a greater ruminal abundance of Prevotella, Succinivibrio, Ruminococcus, Syntrophococcus and Succiniclasticum. Archaea abundance (P=0·002) and total ciliate protozoa were less in steers fed diets containing SO (P=0·011). CG associated with lipids could be an energy source, which is a useful strategy for the partial replacement of maize in cattle diets, could result in reduced total N excretion and ruminal methanogens without affecting intake and digestibility.