Características produtivas, fisiológicas e metabólicas de vacas F1 Holandês x Zebu sob diferentes planos nutricionais

Abstract

The objective of this study was to evaluate the impact of different levels of food supply on the productive, physiological and metabolic characteristics of F1 Holstein x Zebu cows. The experiment was conducted at the Experimental Field of the Agricultural Research Company of Minas Gerais, located in the municipality of Felixlândia. Sixty HZ F1 cows were divided into three lactation periods (42.6 ± 12.77, 108.2 ± 12.07 and 173.6 ± 16.64 days of lactation), totaling 20 animals per experimental period and four cows by treatment. Each group received different nutritional plans calculated with respect to the percentage of body weight (2.00, 2.25, 2.50, 2.75% of animal body weight). One control group had unrestricted food supply, allowing 5% of leftover matter dry at will. The experimental design was completely randomized, in a 5 x 3 factorial scheme, with five nutritional plans and three lactation periods. The results were submitted to analysis of variance, tested at 5% probability. The nutritional plans were assessed through Dunnett and regression tests. The lactation periods were compared by the SNK test. The animals with unrestricted food supply showed higher intake of dry matter (16.97 kg.day-1 ). Milk yields in the first and second lactation periods were similar for the different levels of food supply. In the third lactation period only the 2.75% body weight food supply did not differ from the unrestricted food supply. In cows belonging to the second lactation period, the morning rectal temperature for the 2.00% body weight food supply plan and the morning heart rate for the 2.75, 2.25 and 2.00% body weight food supplies were lower when compared to the unrestricted food supply. In the first lactation period, the afternoon heart rate for the 2.50, 2.25 and 2.00% body weight food supplies was lower when compared to the unrestricted food supply. Only for urea concentration, in the second lactation period, there was difference between the 2.25 and 2.0% body weight food supplies when compared to the unrestricted food supply. The maximum reduction in the levels of food supply offered to animals was 46.02%, and only 25.98% in milk yield. The supply of different nutritional plans to F1 Holstein x Zebu cows did not significantly influence the physiological parameters and concentrations of blood metabolites related to nutritional metabolism. It also did not change milk yield until the middle third of lactation, affecting milk yield only in the final third, possibly due to the need to accumulate reserve for the next lactation.