Utilização de óleo de soja em rações para vacas leiteiras no período de transição: consumo, produção e composição do leite Use of soybean oil for dairy cows during transition period: Intake, milk yield and composition

O objetivo neste estudo foi avaliar o desempenho produtivo de vacas leiteiras sob suplementação com óleo de soja durante o período de transição. Foram utilizadas 20 vacas da raça Holandesa, multíparas e gestantes, distribuídas aleatoriamente em duas rações: controle, com 2,5% de extrato etéreo (EE) na matéria seca (MS); e gordura, com adição de 3,0% de óleo de soja e 5,5% de EE na MS. Os valores médios de consumo de MS e nutrientes não diferiram no período pré e pós-parto nas vacas das dietas controle e com óleo de soja, exceto no maior consumo de EE, em decorrência da maior concentração desse nutriente na dieta com óleo. Em virtude da maior densidade energética da ração com óleo de soja, as vacas apresentaram maior consumo de nutrientes digestíveis totais e energia líquida no pós-parto. Não foi observada alteração nas produções de leite e gordura, no entanto, observou-se redução do teor de gordura do leite nas vacas da ração com óleo de soja em relação àquelas da ração controle. As rações utilizadas não influenciaram o consumo, mas a dieta com óleo de soja aumentou a ingestão de energia líquida e melhorou o balanço de nutrientes no início da lactação. Foi observado aumento não-significativo (+ 2,53 kg/dia) na produção de leite das vacas da dieta com óleo de soja.<br>The objective of this study was to evaluate the productivity of dairy cows supplemented with soybean oil during the transition period. Twenty multiparous and pregnant Holstein cows were randomly allocated to two diets: control (C), 2.5% ether extract (EE) in the dry matter (DM); and fat (G), with the addition of 3% soybean oil, and 5.5% EE in the dry matter. The average values for intake were not different in the pre- and post-partum for cows on the control and fat diets except for an increase in EE intake due to great concentration of this nutrient in the soybean oil diet. Due to the higher energy density of the fat diet, cows had higher intake of total digestible nutrients and net lactation energy during the post-partum. There was no alteration in milk and fat yield, but a reduction in the milk fat content was observed for cows fed fat diet compared with the control diet. The diets used had no influence on the intake, and the fat diet resulted in an increased net energy intake and improvement in the nutrient balance during the initial phase of lactation. A non-significant increase in milk yield (+ 2.53 kg/d) was observed when using the fat diet

Rumen fermentation and rumen microbes in Nellore steers receiving diets with different lipid contents

The objective of the present study was to evaluate the effects of dietary lipid content (20, 40 and 60 g/kg dry matter) on intake, total and ruminal apparent digestibility of dry matter (DM), nutrient digestibility, rumen fermentation parameters, microbial synthesis efficiency and rumen microbial content of beef cattle. Nine cannulated steers at 6 months of age with initial body weight of 232±35 kg were used in a triplicate 3 × 3 Latin square design. The results indicated that the total intake and digestibility of DM, organic matter (OM), gross energy (GE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were not affected by the lipid content of the diet. However, the lowest lipid content diet reduced the total digestibility of crude protein (CP) and total carbohydrate linearly compared with the highest lipid diet. In contrast, when steers were fed a diet containing 20 g lipids/kg of DM, the concentration of ammonia in the rumen decreased quadratically relative to the other diets. Ruminal pH was not affected by the interaction of treatment and sampling time; however, the rumen pH decreased quadratically in animals that received the highest dietary lipid content (60 g/kg) compared with animals that received 20 and 40 g lipids/kg of DM. The rumen concentrations of volatile fatty acids, propionate, and butyrate and the acetate/propionate ratio were affected by the dietary lipid content. However, the microbial population, microbial N flow, and efficiency of synthesis were not affected by dietary lipid content. Overall, an increase in the lipid content of the diet of Nellore steers resulted in similar digestive profiles and fermentation conditions