Efeitos da inclusão de gordura protegida nas rações de cabras saanen em lactação

Abstract

Saanen goats on dry matter and nutrients intake, nutrient utilization efficiency, bloodparameters and milk production and composition. Five Saanen goats (63.23 ± 9.08 kg ofbody weight and ± 105 days of lactation) were distributed in Latin square designs (5x5)with five rations: control (without protected fat) and others, with 6.25; 12.5; 18.75 and25 g of protected fat per kg of dry matter (g/kg of DM), respectively. Intake wasdetermined by daily difference between the food supplied and leftovers and to estimatethe digestibility, indigestible neutral detergent fiber (iNDF) was used as internal marker.Daily milk production was recorded and milk samples were collected to determine thecontent of total solids, protein, fat, lactose and to analyze fatty acids concentration.Blood samples were collected to determine urea, triglycerides and cholesterol in theserum and glucose in the plasma. The simplified economic analysis was performed todetermine the best cost-benefit. Rations did not influence body weight and the intakesof dry matter, organic matter, neutral detergent fiber, total carbohydrates, totaldigestible nutrients and digestible energy. There was a linear increase on the intake anddigestibility of the ether extract and a linear decrease on the intake of the crude proteinand non-fiber carbohydrates, however, without effects on the digestibility of thesenutrients. Blood cholesterol content increased with the inclusion of protected fat in therations, however, urea, triglycerides and glucose concentrations were not changed. Theobserved values for blood parameters indicated nutritional balance between energy andprotein. There was not influence on milk production and fat corrected milk, feedefficiency and milk energetic value. Milk composition and its components productionwere not influenced however there was a linear decrease of 0.87 g of protein per kg ofmilk in each unit including protected fat in the ration. Supplementation with protectedfat improved linolenic acid production (18:3n-3) with the point of maximum at 24 g ofprotected fat per kg of dry matter. Protected fat can be included in rations of lactatingSaanen goats up to 25 g/kg of DM without changing intake and improving nutrientsdigestibility from the point of minimum 9.8 g/kg of DM, however, the best economicresponse is observed when fat inclusion was 6.25 g/kg of DM.