Efficiency of Amino Acid Utilization in Nellore Cattle Grazing Low-Quality Forage Supplemented with Different Sources of Nitrogen.

This study aimed to evaluate the effects of supplementation with non-protein nitrogen (NPN) or ruminal undegradable protein (RUP) on intake, digestibility, and amino acid (AA) use efficiency of Nellore cattle grazing during the dry season. Eight Nellore steers (12 ± 2 months old) were used in quadruplicate Latin squares (2 × 2). The animals were placed on Urochloa brizantha cv. Xaraés under continuous grazing. The treatments included the following: (1) urea supplementation (NPN) and (2) supplementation of corn gluten meal 60 (CGM, RUP). Animals supplemented with CGM showed higher intakes of dry matter (DM) supplement, total AA, essential AA, and individual AA. The supplementation did not affect the total AA digestibility, total AA flux, and the AA fluxes of microbial origin and RUP from the diet (p > 0.05). The ruminal microorganism origin flux of total AA to the duodenum was 44.5% and 52.7% for animals supplemented with NPN and CGM, respectively. Animals supplemented with CGM showed an increase in blood concentrations of isoleucine (+19.09 µmol/L), cystine (+27.29 µmol/L), and albumin (+0.11 g/dL) (p < 0.05), but this increase was not accompanied by an improvement in N use efficiency of steers (p > 0.05). RUP supplementation via CGM can be an efficient nutritional strategy to enhance the intake and absorption of AA by Nellore cattle grazing low-quality forage during the dry season.

Red clover silage: an alternative for mitigating the impact of nitrogen excretion in ovine production systems

The objective was to quantify the flow of intestinal nutrients and nitrogen excretion and retention in sheep receiving isoproteic diets. Eight Texel x Lacaune wethers (average body weight = 25±2.5 kg) were fitted with duodenal cannula and housed in metabolic cages. Wethers were assigned to the treatments in a crossover design with two periods of 20 days each, and all feces and urine produced by the wethers were collected. The treatments consisted of two isoproteic (160 g kg−1 of crude protein on dry matter basis) diets composed of red clover (RC) or lucerne (LU; Medicago sativa) silages plus corn silage and concentrate feed. The digestible organic matter and metabolizable energy intake did not differ between treatments. The intestinal non-ammonia N (NAN) flow was 5.9 g day−1 (37%) higher in RC wethers than in those of the LU treatment. This result was a consequence of both an increase in the efficiency of microbial protein synthesis (12.7% higher) and a decrease in ruminal degradable protein (RDP) content (20% lower) of the diet. However, the increase in the intestinal NAN flow was accompanied by a reduction in intestinal digestibility of N, resulting in similar daily N retention between treatments. The reduction of RDP content was probably the main reason for reductions in N urinary excretion in RC wethers compared with those in the LU treatment, showing that RC silage may be a tool for mitigating the impact of N excretion in ovine production systems, without changes in N retention.(AU)

Role of rumen ciliated protozoa in the synthesis of conjugated linoleic acid: A review / Papel de los protozoos ciliados ruminales en la síntesis de ácido linoleico conjugado: Revisión / Papel dos protozoários ciliados no rúmem para a síntese de ácido linoléico conjugado: Uma Revisão

Traditionally, ruminal ciliate protozoa have been studied with respect to the metabolism of dietary nutrients. Their role has focused on their predatory behavior, the paradigm of its retention in the rumen, and its apparent limited flow to the duodenum. On the other hand, Conjugated Linoleic Acid (CLA) and Vaccenic Acid (VA) are important because of their nutritional value. This review aims to characterize the biological alternatives used by rumen ciliate protozoa for the production of CLA, highlighting three aspects: 1) rumen protozoa are involved only in the initial stage of biohydrogenation to produce CLA isomers, 2) desaturation by protozoa has not been reported, while endogen synthesis by desaturation of VA in mammary glands and fatty tissues has been demonstrated as the main route of CLA in ruminants, 3) even though incorporation of VA and cis9, trans11-CLA in protozoa structure is related with CLA production, this is only important when protozoa flow from rumen to duodenum, producing 30 to 43% of CLA and a 40% of VA, respectively. It is concluded that rumen protozoa are fundamental in the lipid metabolism of ruminants.

Tradicionalmente, los protozoos ciliados ruminales han sido estudiados en relación con el metabolismo de nutrientes de la dieta suministrada al rumiante. Particularmente, su papel ha sido cuestionado debido a sus características predadoras, aunado al paradigma de la retención de los protozoos en el rumen y el aparente limitado flujo al duodeno por reciclaje de la proteína microbiana. De otro lado, los ácidos linoleico conjugado (CLA) y vacénico (VA) son dos productos de gran interés nutricional. Estas dos situaciones han generado interés en la investigación de esta representativa población de la microbiota ruminal. El objetivo de este trabajo fue caracterizar, a partir de la literatura científica, las alternativas biológicas utilizadas por los protozoos ciliados del rumen para la producción de CLA. Nosotros encontramos que: 1) los protozoos ruminales sólo participan en la parte inicial de la biohidrogenación, la “isomerización de ácidos grasos insaturados”, generando isómeros de CLA, 2) la desaturación en protozoos, no se demostró en estudios, y queda claro que la síntesis endógena por desaturación de VA, en glándula mamaria y tejidos grasos se establece como el mayor recurso de CLA en el rumiante, 3) aun cuando la incorporación de VA y cis9, trans11-CLA en la estructura de los protozoos está relacionada con la producción de CLA, esta sólo es importante hasta cuando se da el flujo de protozoos del rumen a duodeno donde son responsables del 30 al 43% del CLA y 40% del VA. Se concluye, que los protozoos ruminales son trascendentales en el metabolismo lipídico de rumiantes.

Tradicionalmente, os protozoários ciliados no rúmen têm sido estudados em relação ao metabolismo dos nutrientes na dieta fornecida ao ruminante. Em particular, o seu papel tem sido questionado devido às suas características predatórias, combinado com o paradigma da retenção de protozoários no rúmem e ao aparente fluxo limitado para o duodeno através da reciclagem da proteína microbiana. Por outro lado, o ácido linoléico conjugado (CLA) e o vacenico (VA) são dois produtos de grande interesse nutricional. Estas duas situações têm gerado interesse na investigação dessa representativa população da microbiota ruminal. O objetivo deste estudo foi caracterizar as alternativas biológicas utilizadas pelos protozoários ciliados do rúmem para a produção de CLA a partir da literatura científica. Nós encontramos que: 1) os protozoários ruminais só participam na parte inicial da biohidrogenação: a isomerização “de ácidos graxos insaturados”, gerando isômeros do CLA. 2) até hoje, não tem sido demonstrado a desaturação em protozoários e fica claro que a síntese endógena por desaturação do VA na glândula mamária e tecido adiposo se estabelece como a maior fonte de CLA no ruminante. 3) embora a incorporação de VA e cis9, trans11-CLA na estrutura do protozoário está relacionada com a produção de CLA, ésta só é importante ate quando há fluxo de protozoários do rúmem para o duodeno onde são responsáveis do 30 ate 43% do CLA e 40% do VA. A conclusão é que os protozoários ruminais são transcendentais no metabolismo lipídico dos ruminantes.