Effect of CSN1S1 genotype and its interaction with diet energy level on milk production and quality in Girgentana goats fed ad libitum

Abstract

A study was carried out to evaluate how the energy level of the diet can affect milk production and quality in Girgentana lactating goats in relation to polymorphism at the alphas1-casein (CSN1S1) genotype locus. Twenty-seven goats, homogeneous for milk production (1.5+/-0.3 kg/d), days of lactation (90+/-10 d) and body weight (35.8+/-5.5 kg) were selected on the basis of their CSN1S1 genotype, as follows: nine goats homozygous for strong (AA) alleles, nine goats homozygous for weak alleles (FF) and nine goats heterozygous (AF). The goats were used in a 3x3 factorial arrangement of treatments, with three genotypes (AA, FF, AF) and three diets at different energy levels (100%, 65% and 30% of hay inclusion). The experiment consisted of three simultaneous 3x3 Latin squares for the three genotypes, with one square for each level of hay inclusion in the diet. All the animals were housed in individual pens. Each experimental period lasted 23 d and consisted of 15 d for adaptation and 8 d for data and sample collection, during which the goats received the scheduled diet ad libitum. The animals were fed three different diets designed to have the same crude protein content (about 15%) but different energy levels: a pelleted alfalfa hay (H100) and two feeds including 65% (H65) and 30% (H30) of alfalfa hay (respectively 1099, 1386 and 1590 kcal NE for lactation/kg DM). All the diets were ground and pelleted (6 mm diameter). AA goats were more productive than AF and FF goats (respectively: 1419 v. 1145 and 1014 g/d; P=0.002). Indeed the interaction energy levelxgenotype was significant (P=0.018): in fact AA goats showed their milk increase only when fed with concentrates. Differences in protein and in casein levels between the three genotypes were in line with results expected from the different allele contribution to alphas1-casein synthesis. Milk urea levels were significantly lower in AA goats compared with AF and FF genotypes (respectively 32.7 v. 40.4 and 40.4 mg/dl; P=0.049) and significantly lower when goats were fed with 65H and 30H diets than with 100H diet (respectively 37.4 and 34.3 v. 41.7 mg/dl; P<0.001). Indeed, a significant interaction genotypexdiet (P=0.043) occurred for milk urea, which was significantly lower in AA goats but only when fed with concentrates (65H and 30H). Blood concentrations of energy indicators (glucose, non-esterified fatty acids and beta-hydroxybutyric acid) were not influenced by genotype. The results confirm that strong alleles are associated with a greater efficiency of feed utilization and seem to show that a high energy level of the diet can further improve this efficiency.

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

“…The DM and main nutrients intake were strongly influenced by diet, while it did not reveal a significant effect of CSN1S1 genotype and diet by genotype interaction ( Table 1). Similar results were found by Bonanno et al [29] and Pagano et al [10]. In particular, Bonanno et al [29] reported no difference in DM intake between goats with strong (aa) and heterozygous (aF) genotypes, like in the present study, although they observed a lower feed intake in goats with a weak (FF) genotype.…”

“…Because feed also exerts a great influence on the yield and properties of goat milk, there is interest in how nutrition might interact with the genetic polymorphism at α S1 -Cn. Recent researches showed how aa goats, compared with FF goats, more efficiently utilize dietary protein [7][8][9] and respond to high-energy diets by utilizing nutrients more efficiently and achieving a higher milk yield [10].…”

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

“…In this report, milk fat was not influenced by CSN1S1 genotype, in contrast with Pagano et al (2010) where high genotype goats showed a higher milk fat content than low genotype goats.…”

Poster Presentations

“…As these milk properties are also affected by nutrition, it is of some interest to consider the interaction of the CSN1S1 genotype and dietary characteristics. Few studies focusing on this aspect, demonstrated that strong alleles are related to a greater efficiency of protein utilization (De la Torre et al 2009), and to a better response to high dietary energy level compared to weak alleles (Pagano et al 2010). In order to contribute to the knowledge of the relationships between nutrition and CSN1S1 genotype in goats, this study was aimed to investigate the impact of fresh forage based diet and/or energy supplement on feeding behaviour, milk production, metabolic and hormonal parameters and oxidative stress of Girgentana goats with different genotype at CSN1S1 locus.…”