Avaliação de duas rações ensiladas para vacas de corte gestantes: parâmetros químicos, nutricionais e respostas produtivas nas vacas e suas progênies

Abstract

Preservation feed in the form of ration exposes dietary protein to degradation during the storage period, which increases the concentration of soluble protein. The objective of this study was to evaluate whether the conservation process could impact the chemical, nutritional parameters and productive responses of cows and their progeny. For this, two experiments were carried out (exp. 1 and 2). In exp. 1 the experimental treatments were two partial ensiled rations, composed of: 1) Marandu grass (87.6% DM) and dry distillers grains (12.8% DM) and 2) Marandu grass (87.6% DM), soybean hulls (11.7% DM) and urea (1.1% DM), in addition, the two ration were ensiled with and without the application of an acid additive (Fylax® Forte Liquid), at a dose of 1 mL per kg of ensiled food. The variables evaluated were pH, aerobic stability, dry matter losses (DM), fermentation profile, microorganism count and chemical composition. The experimental design was completely randomized, in a 2 x 2 factorial arrangement, with five replications each. Values of P≤0.05 were considered significant. In exp. 2, thirty-three Tabapuã beef cows were used in the middle third of gestation (±130 days of gestation), which were randomly distributed to the treatments: 1) ensiled ration containing Marandu grass (86.3% DM), DDG (12 .7% DM) and mineral mixture (1.0% DM; n = 17) or 2) ensiled ration containing Marandu grass (86.3% DM), soybean hulls (11.6% DM), urea (1. 1% DM) and mineral mixture (1.0% DM; n = 16). The acid additive was applied to both feeds at the time of ensiling, at a dose of 1 L per ton of feed. The storage structure used was bag silos and stored for 47 days. Cows were housed in individual stalls for 100 days. The collection period for digestibility was four days, where fecal and urine samples were collected. Blood parameter samples were collected on the last day of confinement. In the statistical analysis, a completely randomized design was used with a 2 × 2 factorial arrangement, referring to maternal nutrition and the sex of the progeny, using the lm function of R. In exp. 1 the presence of the additive reduced DM losses in the diets (P<0.01) and provided a lower participation of the C fraction in total protein (P<0.01). In exp. 2 cows fed with silage containing DDG had higher dry matter intake (P<0.01), weight at the end of confinement (P<0.01), higher ADG (P<0.01) and gained 50 g/day. While cows fed the CS diet lost 445 g/day and had higher plasma concentrations of urea before feeding (P<0.01), nonesterified fatty acids (P=0.02) and beta-hydroxybutyrate (P<0.01). The rations were well preserved, and the use of the additive reduced dry matter losses and the participation of fraction C of CP. The DDG diet provided greater intake and performance of cows during pregnancy, however this superior performance had no effect on the performance of the progeny.