Effects of diet on casein and fatty acidudprofiles of milk from goats differing inudgenotype for αS1-casein synthesis

摘要

This study investigated the interactions betweenudnutrition and the genotype at αS1-CN loci (CSN1S1) inudgoats, evaluating the impact of fresh forage-based dietsudand an energy supplement on the casein and fatty acid (FA)udprofiles of milk from Girgentana goats. Twelve goats wereudselected for having the same genotype at the αS2-CN, β-udCN, and κ-CN loci and differing in the CSN1S1 genotype:udhomozygous for strong alleles (AA) or heterozygous forudstrong and weak alleles (AF). Goats of each genotype wereuddivided into three groups and, according to a 3 × 3 Latinudsquare design, fed ad libitum three diets: sulla fresh forageud(SFF), SFF plus 800 g/day of barley (SFB), and mixedudhay plus 800 g/day of barley (MHB). The SFB diet led toudhigher-energy intake and milk yield. The energy-supplementeduddiets (SFB, MHB) reduced milk fat and urea andudincreased coagulation time. The fresh forage diets (SFF,udSFB) increased dry matter (DM) and crude protein (CP)udintake and milk β-CN. Diet had a more pronounced effectudthan CSN1S1 genotype on milk FA profile, which wasudhealthier from goats fed the SFF diet, due to the higher contentudof rumenic acid, polyunsaturated, and omega-3 FAs.udThe AA milk had longer coagulation time and higher curdudfirmness, higher short- and medium-chain FAs (SMFA),udand lower oleic acid than AF milk. Significant diet by genotypeudinteractions indicated the higher milk yield of AAudgoats than AF goats with the higher-energy SFB diet andudthe lower synthesis of SMFA in AF than in AA goats withudthe SFF diet.