Effects of diet on casein and fatty acid profiles of milk from goats differing in genotype for αS1-casein synthesis

Abstract

This study investigated the interactions between nutrition and the genotype at α S1-Cn loci (CSN1S1) in goats, evaluating the impact of fresh forage-based diets and an energy supplement on the casein and fatty acid (Fa) profiles of milk from girgentana goats. Twelve goats were selected for having the same genotype at the α S2-Cn, β-Cn, and κ-Cn loci and differing in the CSN1S1 genotype: homozygous for strong alleles (aa) or heterozygous for strong and weak alleles (aF). goats of each genotype were divided into three groups and, according to a 3 × 3 latin square design, fed ad libitum three diets: sulla fresh forage (SFF), SFF plus 800 g/day of barley (SFB), and mixed hay plus 800 g/day of barley (MHB). The SFB diet led to higher-energy intake and milk yield. The energy-supplemented diets (SFB, MHB) reduced milk fat and urea and increased coagulation time. The fresh forage diets (SFF, SFB) increased dry matter (DM) and crude protein (CP) intake and milk β-Cn. Diet had a more pronounced effect than CSN1S1 genotype on milk Fa profile, which was healthier from goats fed the SFF diet, due to the higher content of rumenic acid, polyunsaturated, and omega-3 Fas. The aa milk had longer coagulation time and higher curd firmness, higher short-and medium-chain Fas (SMFa), and lower oleic acid than aF milk. Significant diet by genotype interactions indicated the higher milk yield of aa goats than aF goats with the higher-energy SFB diet and the lower synthesis of SMFa in aF than in aa goats with the SFF diet. a. Bonanno (*) • a

Quantitative determination of casein genetic variants in goat milk: Application in Girgentana dairy goat breed

“…However, the casein genetic variants quantified in our study were the most frequent in Girgentana goat breed; in fact, at CSN1S2, the most frequent alleles were A and F (Palmeri, Mastrangelo, Sardina, & Portolano, 2014), at CSN2 were C and C1 (Tortorici, Di Gerlando, Mastrangelo, Sardina, & Portolano, 2014), and at CSN3 gene were A and B (Di Gerlando et al, 2015). Comparing our data with those reported by Bonanno et al (2013), which used a different chromatographic method, it can be possible to state that our applied chromatographic conditions allowed in less time running, run was 5 min shorter, a greater separation and resolution of caseins as higher distance between caseins peaks.…”

Effects of ewes grazing sulla or ryegrass pasture for different daily durations on forage intake, milk production and fatty acid composition of cheese

“…The sulla cheese, compared with ryegrass cheese, was lower in MUFA, with the exception of VA, and was markedly higher in PUFA, especially LA, ALA and EPA, in accordance with Cabiddu et al (2005) who similarly compared the milk from ewes grazing sulla or ryegrass for the entire day, and Bonanno et al (2013b), who compared the milk from goats fed sulla or a hay-based diet.…”

“…Thus, there were positive effects of both sulla and ryegrass in maintaining and increasing milk protein and casein composition, respectively, when grazing was prolonged, consequently leading to an increase in milk yield. The favourable effect of feeding sulla on milk protein and casein was also observed by Bonanno et al (2013a and2013b), and attributed to the intake of CT. This was able to reduce protein degradability in the rumen, and consequently increase the amount of amino acids to be absorbed in the intestinal tract (Min et al, 2003), thereby contributing to the improved efficiency of dietary protein utilisation for milk casein synthesis in the udder tissue.…”

“…In previous research, the intake of sulla forage containing CT increased casein levels in milk (Bonanno et al, 2013a and2013b). Furthermore, exposure of ewes (Cabiddu et al, 2005 and2009) and goats (Bonanno et al, 2013b) to the CT contained in sulla forage increased the polyunsaturated fatty acid (PUFA) content in milk, which has beneficial effects on human health as CT inhibits the complete ruminal biohydrogenation of dietary PUFA.…”

“…Furthermore, exposure of ewes (Cabiddu et al, 2005 and2009) and goats (Bonanno et al, 2013b) to the CT contained in sulla forage increased the polyunsaturated fatty acid (PUFA) content in milk, which has beneficial effects on human health as CT inhibits the complete ruminal biohydrogenation of dietary PUFA. In addition, due to its CT content, sulla fresh forage-based diets were able to improve the plasma oxidative status and increase the polyphenol content and total antioxidant capacity of milk in goats (Di Trana et al, 2015).…”