Substituição do milho por palma forrageira na dieta de vacas Guzerá lactantes

Abstract

The objective of this work was to indicate the adequate level of substitution of ground corn by forage palm in diets of Guzerá during the lactation period. Were used five multiparous Guzerá cows housed in individual stalls, with experimentation divided into 5 periods of 15 days each. The experimental design used was the Latin square 5 x 5. The five treatments consisted of increasing proportions of forage palm energy content in total digestible nutrients (TDN) replacing the TDN content of corn in the dry matter of the feed (0, 25, 50, 75 and 100%). The variables analyzed were nutrient intake and water intake, milk production and composition. The data were submitted to analysis of variance and the means compared by the regression analysis to 5% probability by the SISVAR program. No differences were found regarding nutrient intake in general, due to the substitution levels adopted. These results occurred because the diets presented similarities in their chemical compositions, in addition to the fact that no filling implications were observed, which usually happen when the palm makes up a large part of the diet, which did not occur in the present study. The high desirability of the palm contributed to avoid reductions in consumption. For voluntary water intake and water contained in food, substitution levels presented linear decreasing and increasing effects respectively, with no effect on the total consumption of water / day, resulting from the sum of both. This shows the important role of forage palm as a source of water, reducing voluntary intake and consequently water costs for the farmer, an important nutrient for dairy cows and generally limiting the semi-arid cattle ranching. For milk production, milk corrected to 4% of fat as well as the chemical composition of milk, no effects of substitution levels were observed for these variables, which is justified by the lack of nutrient intake as well as the experimental diets, which have excellent balance for fibrous carbohydrate, non-fibrous and crude protein, thus favoring conditions in the ruminal environment for adequate production of short chain fatty acids and microbial protein, affecting milk yields similar to the levels adopted and with high and similar levels of nutrients, mainly fat that resulted in an increase in milk production when corrected to 4% fat, and this nutrient has an important role for valorizing milk quality and the Guzerá breed having a proven reputation for producing milk with high fat contents. Although the results were favorable, it is suggested that this substitution be more studied, mainly in the complementation with an economic analysis to prove the reduction of production costs. It is possible to substitute the energy of the corn by the palm in 100% in the diets with sorghum silage, resulting in reduction of water intake through the drinking fountain and without affecting the productive performance and physical-chemical of the milk of Guzerá cows with medium production.