Effect of genotype at CSN1S1 per diet interaction on milk fatty acid profile in Derivata di Siria lactating goats

A study was carried out to evaluate how the dietary levels of energy and protein requirements and its interaction with polymorphism at the CSN1S1 genotype locus can affect fatty acid (FA) profile in Derivata di Siria lactating goats. Twenty-seven goats, homogeneous for days of lactation (50 ± 5d), milk production (1.3 ± 0.3 kg/d), and body weight (42.1 ± 1.2kg), were selected on the basis of their CSN1S1 genotype, as follows: nine homozygous for strong (AA) allele, nine heterozygous (AF) and nine homozygous for weak allele (FF). The goats were used in a 3x3 factorial arrangement of treatments, with three genotypes (AA, AF, FF) and three feeding treatments. In the course of the trial, the goats received the same pelleted diet (5.8 MJ NE l/kg DM; 15.2% CP) but in variable amounts according to the treatment. The three experimental treatments supplied 70 and 75 % (L), 100 and 110% (M) and ad libitum (H) of the goat’s energy and protein requirements, respectively. The experiment consisted of three simultaneous 3 x 3 Latin squares for the three genotypes, with one square for each level of energy and protein requirements. Each experimental period lasted 23d of which 15d for adaptation and 8d for milk samples collection. The genotype×diet interaction was significant (P<0.05) for SFA, omega-3, SCFA, Medium Chain Fatty Acids (MCFA) and Thrombogenic Index (TI). A slight (P < 0.06) effect of genotype×diet interaction was detected for PUFA and C18:1/C18:0 ratio. In the H group a larger number of parameters were affected by genotypes than in L and M groups. SFA and SCFA were lower in AA and FF than AF when H diet was consumed. In M and L, PUFA decreased from AA (6.73, 6.22), AF (6.80, 6.02) to FF (6.25, 5.39) genotype, respectively. For the AA goats, higher value was obtained for PUFA when H diet was consumed. AF goats showed a higher value for omega-3 when M and L diets were ingested. In M group, MCFA increased (P < 0.05) from AA, AF genotypes to FF one. Also, TI worsened in FF genotype than AA and AF when M was consumed. Shifting from L to H diet, C18:1/C18:0 ratio significantly increased in AA and AF slightly in FF. MCFA increased (P < 0.05) in AA, AF and FF when the diet shifted from L to H. TI decreased (P < 0.05) in AA and AF, slightly in FF when the diet changed from H, M to L. FA profile of CSN1S1 genotypes seems to depend on the diet consumed. Similarly, the advantage of changing diet in order to optimize FA profile depends on the genotype of goats.