Effect ofCSN1S1gene polymorphism and stage of lactation on milk yield and composition of extensively reared goats

Abstract

The effect of CSN1S1 genotype and lactation stage on milk yield and composition were investigated in 80 extensively reared goats. Milk yield was recorded in early, mid and late lactation and individual milk samples were collected to determine: fat, protein, lactose and casein content, pH, freezing point, somatic cell count (SCC) and total microbic mesophilic count (TMC). Relative casein composition and amino acid profile were quantified by HPLC. Fatty acid profile was measured by gas-chromatography. Genotype did not affect milk yield, while this trait was significantly affected by lactation stage (P < 0.01). CSN1S1 BB goats produced significantly higher protein and casein percentages (P < 0.05). αs1-casein (CN) was significantly higher in BB and AB goats than AF and BF, showing intermediate values in AA goats (P < 0.01). The protein percentage and the αs1 and αs2-CN fractions were not affected by lactation stage, while the casein content and the β and κ-CN significantly increased throughout lactation (P < 0.01). C4 : 0 and C6 : 0 were not affected by genotype, while C8 : 0 and C10 : 0 were higher in the AA goats than BB; most of the long chain FA were higher in BB than AA goats. MUFA and PUFA increased in late lactation. In addition, BB goats showed higher essential amino acids, resulting in an optimal composition from the nutritional point of view, when compared with AA goats. The increase of MUFA, PUFA, essential and cis-FA in late lactation indicate that the lipid composition of goat's milk, with the progress of lactation, tends to improve its nutritional value.

Determining the frequencies of B1, B2, B3 and E alleles of the <i>CSN1S1</i> gene and their effects on milk yield and composition in Saanen goats

“…For milk yield and composition, an investigation of the Sarda breed showed that CSN1S1 BB goats produced significantly higher protein and casein percentages. In addition, αs1-CN was significantly higher in BB and AB Sarda goats than in AF and BF Sarda goats (Balia, 2013). Dominant effects were found for some genotypes for milk yield (AN and BN), fat yield (AN and BE), protein yield (AN and BE), lactose yield (AN), and TS yield (AN).…”

“…The effects of age and lactation length on milk composition should depend on negative correlation with yield and contents of milk. Balia et al (2013) pointed out that goats with BB genotypes of the CSN1S1 gene produced higher protein and casein percentages. Unlike the findings of Balia et al (2013), B1 and B2 alleles of the CSN1S1 gene did not affect milk yield and composition in the present study.…”

“…Balia et al (2013) pointed out that goats with BB genotypes of the CSN1S1 gene produced higher protein and casein percentages. Unlike the findings of Balia et al (2013), B1 and B2 alleles of the CSN1S1 gene did not affect milk yield and composition in the present study. On the other hand, significant effects on protein, fat, TS, SNF, casein and lactose percentage were found by B3 allele (P <0.05).…”

“…After parturition, milk samples were collected in 100 mL sterile sample containers bimonthly during lactation. Samples were transported at +4 ºC to the laboratory within two hours (Balia et al, 2013). Total milk yield per lactation was calculated by the Fleischmann method (Trapez II), which was described in International Committee for Animal Recording (ICAR) Guidelines 2014 (Berger & Thomas, 2005).…”

The Application of Genomic Technologies to Investigate the Inheritance of Economically Important Traits in Goats

“…Similarly, Zullo et al [25] reported effects of the CSN1S1 genotype on milk composition in Cilentana goats. Chilliard et al [26] and Balia et al [27] have also proposed that milk fat composition is modulated by the CSN1S1 genotype. A global effect of CSN1S1 variation on protein content might be explained by the fact that CSN1S1 plays a pivotal role in casein transportation from the endoplasmic reticulum to the Golgi complex in mammary epithelial cells [28].…”