In situ ruminal degradability of protein feeds with distinct physical forms: a meta-analysis

In ruminant livestock, rumen undegradable protein (RUP) derived from the diet and microbial protein synthesized in the rumen are essential for animal survival, maintenance, growth, production, and reproduction. RUP is influenced by diet composition, physical form, and ruminal metabolism. Here, we aimed to evaluate the ruminal degradability of protein feeds with different physical forms (meal versus grain) through a meta-analysis study. A database, composed of 45 treatments from 12 studies carried out in Brazil, was evaluated to compare the degradability of soybean, sunflower, canola, and flaxseed grains with the meal forms of soybean, peanut, sunflower, cottonseed, and corn gluten. The degradation parameters of dry matter did not differ significantly between meals and grains. However, the effective degradability of crude protein at a passage rate of 2% per hour was higher in meals than in grains. Overall, it was concluded that meal protein might be more degradable in the rumen of animals on an energy intake lower than the maintenance.Keywords: Concentrated feed, metabolism, passage rate, processing, ruminant

Suplementos energéticos para recria de novilhas de corte em pastagens anuais: desempenho animal Energy supplements for beef heifers rearing at annual pastures: animal performance

Foi avaliado o desempenho de novilhas de corte dos três aos doze meses de idade, mantidas em pastagem cultivada logo após o desmame (experimento 1) e no primeiro inverno pós-desmame (experimento 2), com ou sem o fornecimento de suplementos energéticos. No período de 16/02 a 21/04/2001, as novilhas permaneceram em pastagem de milheto, exclusivamente sob pastejo (PAST1), suplementadas com grão de milho moído (PAST1/M) ou com polpa cítrica peletizada e moída (PAST1/P). No período de 13/07 a 09/10/2001, as novilhas foram mantidas em pastagem de aveia preta e azevém, sem suplementação (PAST2), suplementadas com grão de milho moído (PAST2/M) ou suplementadas com casca de soja (PAST2/C). Peso vivo (PV), ganho de peso diário médio (GDM) e escore de condição corporal (ECC) foram avaliados. No experimento 1, os animais suplementados apresentaram maior PV final, GDM e ECC que os não-suplementados, não diferindo entre si. No experimento 2, as novilhas suplementadas com casca de soja apresentaram maior GDM e PV final que as não-suplementadas, enquanto as suplementadas com grão de milho ficaram em posição intermediária. O maior ECC foi obtido pelos animais de PAST2/C, seguidos de PAST2/M e, por último, de PAST2. Novilhas de corte desmamadas aos 60-90 dias devem ser suplementadas no período inicial pós-desmama, para que atinjam desenvolvimento satisfatório nesta fase do crescimento. Os subprodutos polpa cítrica e casca de soja podem substituir o grão de milho como suplementos energéticos para recria de novilhas de corte.<br>It was evaluated beef heifers performance from three until twelve months of age, when they were reared in cultivated pasture soon after their weaning (experiment 1) and in the first winter post-weaning (experiment 2), with or without the supply of energy supplements to the animals. From 02/16 to 04/21/2001, the heifers stayed in Pearl Millet pasture, exclusively under grazing (PAST1); supplemented with milled corn grain (PAST1/C) or supplemented with pellet citric pulp (PAST1/P). From 07/13 to 10/09/2001, the heifers were maintained in oat plus italian ryegrass pasture without supplementation to the animals (PAST2); supplemented with milled corn grain (PAST2/C) or supplemented with soy hull (PAST2/H). The evaluated variables of animal performance were live weight (LW), average daily gain (ADG) and body condition score (BCS). In the experiment 1, supplemented animals presented larger values of final LW, ADG and BCS in relation to the non supplemented, ones the supplemented treatments not differing to each other. In experiment 2, the soy hull supplemented heifers showed greater ADG and final LW than non supplemented heifers, with the corn grain supplemented group in an intermediary position. The highest BCS was obtained by the animals of PAST2/H, followed by PAST2/C and, at last, of PAST2. Beef heifers weaned at 60-90 days should be supplemented in the initial post-weaning period, enabling them to reach satisfactory development in this phase of growth. The by-products citric pulp and soy hull can substitute the corn grain as energy supplements for rearing of beef heifers