Desempenho de vacas zebuínas suplementadas a pasto.

Abstract

Dairy cattle farming in Brazil is mostly on pasture, being the most economical way to produce milk. A grass in good nutritional condition has the capacity to meet the nutritional requirements of the animals, without the need for supplementation, depending on the size, breed, physiological condition and category of the animal. However, pasture supplementation, even in small amounts, can help to make better use of forage, either in the wet season or in the dry season. In this context, the objective was to evaluate the production and composition of milk from Sindi cows grazing supplemented with different protein sources. The work was carried out at the Experimental Station of Alagoinha, belonging to the Paraiba Company of Research, Rural Extension and Land Regularization (EMPAER-PB), located in the municipality of Alagoinha-PB, during the months of May to August 2018, totaling 68 experimental days, divided into four periods of 17 days. The pasture area was formed by Brachiaria brizantha, provided with drinking fountains. Eight Sindhi cows were used, distributed in two 4 x 4 Latin squares, balanced according to the number of calves and milk production, with an average weight of 312±20 kg and producing 9.0 kg of milk per day, with 3.5% of fat. The treatments consisted of concentrated supplementation, with variation of the protein source. T1: Mineral salt, T2: Soybean meal, T3: Cotton cake and T4: Urea, these were formulated to be isonitrogenated, and to meet the requirements of the animals. The quantities of each supplement were supplied using a ratio of 1 kg of natural matter for each 3.0 kg of milk produced and divided, in such a way that each animal received the same amount of supplement in the morning (5:00 am) and in the afternoon (15:00 h), during manual milking. The first 10 days of each experimental period were used to adapt the animals to treatments, and the other 7 days were for data collection. Milk production was measured every day, using individualized weighing on a digital scale and the average of the last five days of each period was used. To determine the physical-chemical composition of milk, three-day milk was collected in the morning and in the afternoon, homogenized and evaluated by ultrasound, using Master Mini equipment (AKSO - Produtos Eletrônicos Ltda., São Leopoldo - RS). The data were analyzed using means, and all analyzes were performed by Sisvar, using the Tukey test at a significance level of 5% probability. The results obtained for average milk production (PL) and milk production corrected for 4% fat (PLCG 4%), did not show significant difference in relation to the protein sources used, with an average of 5.05 and 5.90 kg of milk, respectively. These results are probably due to the quality of the pasture used, which in this work was Brachiaria brizantha. As with PL, the physical-chemical composition of milk, that is, fat, protein, lactose, total solids (ST) and non-fat solids (SNG), did not show any significant difference in relation to the protein sources used, being the values averages of 5.20; 3.83; 5.70; 15.57 and 10.36%, respectively. The use of supplementation with different protein sources (Soybean Meal, Cotton Pie and Urea) for Sindhi cows grazing Brachiaria brizantha grass does not influence milk production and composition during the water-dry transition period.