The effects of dietary lipids and roughage level on dairy goat performance, milk physicochemical composition, apparent transfer efficiency and biohydrogenation rate of milk fatty acids

Abstract

AbstractThe study was conducted to investigate the effects of fish or palm oil diets with different roughage levels on dairy performance, milk physicochemical composition and apparent transfer efficiency of fatty acids (FA) in goat milk. The experiment was conducted with 40 Aleppo goats with a mean parity of 2.53 ± 0.8 (multiparous), mean initial body weight of 47.23 kg and 25 ± 5 days in milk which were allocated to four (2 × 2) experimental diets with two oil sources (fish or palm oil) at 25.6 g/kg of dietary dry matter and forage levels (400 or 600 g/kg). The experimental data were analysed by repeated measures analysis, using the MIXED procedure. The concentrations of saturated FA decreased with high forage level and fish oil diets; however, the fish oil diets caused an increase in C14 saturated FA. Fish oil diets with high roughage levels more efficiently increased conjugated linoleic acid, n-6 (18 : 2), and n-3 (20 : 5). The apparent transfer efficiency of 18 : 1, 18 : 2, 18 : 3 and 20 : 5 decreased and the transfer efficiency of 22 : 6 increased with the use of fish oil in the diet. The roughage level did not affect the apparent transfer efficiency of 18 : 1 and 18 : 2, but the low roughage level increased the apparent transfer efficiency of 20 : 5. High roughage diets improved milk quality parameters through increasing eicosapentaenoic acid, polyunsaturated fatty acids (PUFA), PUFA/saturated FA and atherogenicity index, thus it was concluded that dietary roughage level could be considered as an important designator of milk quality when a supplement of fish oil and palm oil was supplied to goats.