Effects of diet and genotype at CSN1S1 locus on the oxidative stress in lactating goats

Twenty-eight Girgentana goats were selected on the basis of their CSN1S1 genotype as follows: 14 goats homozygous for strong (AA) alleles and 14 goats heterozygous (AF). The goats were used in a 2 x 4 factorial arrangement of treatments, with the two genotypes (G) and four diets (D). The diets were: a pelleted alfalfa hay (100H), a complete feed including alfalfa hay at 65% (65H), fresh sulla (Hedysarum coronarium L.) forage (100S) and fresh sulla plus barley (65S). Each trial consisted of 15d for adaptation and 8d for sample collection, during which the goats received the scheduled diet ad libitum. Blood samples were collected at the end of pre-experimental and experimental period. Plasma content of Reactive Oxygen Metabolites (ROMs), biological antioxidant potential (BAP) and -tocopherol were measured by colorimetric assay and HPLC, respectively. Data were analysed by ANOVA including effect of G, D and interaction G x D. There was no significant effect of G and interaction G x D on all parameters. Diet significantly influenced ROMs, BAP and -tocopherol. The ROMs concentration was significantly lower (P<0.05) in goats that received fresh forage 100S and 65S (4.20 and 4.53 lnUCarr) compared to goat groups that received hay 100H and 65H (5.24 and 5.20 lnUCarr). The BAP was higher (P<0.05) in 100S, 65S and 65H (respectively 8.01, 7.99 and 7.95 lnEq/L) than in 100H (7.66 lnEq/L). Plasma -tocopherol was significantly higher in 100S and 65S diets compared with 100H and 65H diets (respectively 2.36 and 2.17 vs 1.79 and 1.81 ln mol/L; P<0.03). A negative correlation between ROMs and -tocopherol concentration was observed (r=-0.80; P<0.05). On the contrary, positive correlations between -tocopherol and BAP plasma content (r=0.31; P<0.02) and milk production (r=0.28; P<0.03) were found. This study has identified that diet (fresh forage vs dry diet) rather than genotype has a more pronounced effect on oxidative stress.