Effects of concentrates with different contents of protected fat rich in PUFAs on the performance of lactating Granadina goats 1.: Feed intake, nutrient digestibility, N and energy utilisation for milk production

The purpose of this study was to determine whether the use of different levels of a protected fat rich in polyunsaturated fatty acids (PUFAs) in the concentrate fraction of diets for lactating goats has any effects on feed intake, nutrient digestibility, N and energy utilisation for milk production. Three groups of six Granadina goats in the middle of their second lactation were used. They were fed diets of forage (50%) and concentrate (50%). The concentrate fraction contained either 0, 9 or 12% added fat. The added fat was protected against rumen metabolism and was particularly rich in PUFAs. The total feed intakes and the forage and concentrate intakes were determined for each case as were the digestibility of nutrients and the N and energy utilisation for milk production. A tendency to decrease total feed intake as the fat level increased was observed. The concentrate fraction intake and the DM digestibility for fat addition in the concentrate at 12% was lower (p < 0.05) than that for the basal diet. Organic matter and energy digestibilities were lower (p < 0.05) for fat addition in the concentrate at 12% than those for fat addition at 9% and for the basal diet. However, fat addition in the concentrate at 9 and 12% or only at 12%, brought about an increase (p < 0.05) in fat digestibility or ADF digestibility, respectively. The ratio between N output in the milk and N ingested or N available for production for fat addition in the concentrate at 9% was higher (p < 0.05) than that for the basal diet. Finally, the ratio between energy output in the milk and metabolisable energy available for production for fat addition in the concentrate at 12%, tended to be higher than those for fat addition in the concentrate at 9% and for the basal diet. From these results, it is concluded that the use in the concentrate fraction of diets for lactating goats of the protected fat here considered, gives rise to a good digestive utilisation of the diet together with improved N and metabolisable energy utilisation for milk production. (C) 2002 Elsevier Science B.V. All rights reserved.