Eighteen Girgentana lactating goats, nine homozygous for strong alleles (AA) and nine homozygous for weak alleles (FF) at α s1-casein (CSN1S1) locus, were used to evaluate the effect of genotype, diet and genotype×diet (G×D) interaction on the composition of goat milk caseins. Goats were used in a 2×2 factorial arrangement of treatments, with two genotypes (AA, FF) and two diets at different energy levels (high-energy diet (D65) and low-energy diet (D100)). The experiment consisted of two simultaneous 2×2 Latin squares for the two genotypes, with one square for each level of energy. Capillary electrophoresis was used for the determination of relative casein (CN) composition α s1-CN, κ-CN and β-CN yield was significantly higher with D65 than D100 (10.2 vs 7.2; 3.8 vs 2.6; 18.6 vs 13.6g/d, respectively). Genotype significantly affected (P<0.05) α s2-CN and α s1-CN yield: α s1-CN was higher in AA than FF goat milk (15.5 vs 2.4g/d), while α s2-CN was higher in FF than AA goat milk (4.7 vs 2.8g/d); no genotype effect (P>0.05) was reported for κ-CN and β-CN yield. As concerning individual casein concentration, α s1-CN was higher for AA than FF goat (12.4 vs 1.5g/kg milk), whereas α s2-CN and β-CN were higher in FF than AA milk (4.3 vs 1.4; 15.6 vs 12.9g/kg, respectively); also κ-CN tended to be higher in FF goats. Diet did not significantly influence concentration of individual caseins. A significant G×D interaction was found only for α s1-CN concentration, which decreased (-10%) when AA goats shifted from D100 to D65. In conclusion, high energy input consistently improved total casein yield beside genotype. The higher casein yield of AA goats mainly depends on α s1-CN biosynthesis; moreover, the lower presence of α s1-CN in FF goat milk may be partially counterbalanced by the other caseins.
Effect of diet at different energy levels on milk casein composition of Girgentana goats differing in CSN1S1 genotype
Valenti, B.
;
2012
Abstract
Eighteen Girgentana lactating goats, nine homozygous for strong alleles (AA) and nine homozygous for weak alleles (FF) at α s1-casein (CSN1S1) locus, were used to evaluate the effect of genotype, diet and genotype×diet (G×D) interaction on the composition of goat milk caseins. Goats were used in a 2×2 factorial arrangement of treatments, with two genotypes (AA, FF) and two diets at different energy levels (high-energy diet (D65) and low-energy diet (D100)). The experiment consisted of two simultaneous 2×2 Latin squares for the two genotypes, with one square for each level of energy. Capillary electrophoresis was used for the determination of relative casein (CN) composition α s1-CN, κ-CN and β-CN yield was significantly higher with D65 than D100 (10.2 vs 7.2; 3.8 vs 2.6; 18.6 vs 13.6g/d, respectively). Genotype significantly affected (P<0.05) α s2-CN and α s1-CN yield: α s1-CN was higher in AA than FF goat milk (15.5 vs 2.4g/d), while α s2-CN was higher in FF than AA goat milk (4.7 vs 2.8g/d); no genotype effect (P>0.05) was reported for κ-CN and β-CN yield. As concerning individual casein concentration, α s1-CN was higher for AA than FF goat (12.4 vs 1.5g/kg milk), whereas α s2-CN and β-CN were higher in FF than AA milk (4.3 vs 1.4; 15.6 vs 12.9g/kg, respectively); also κ-CN tended to be higher in FF goats. Diet did not significantly influence concentration of individual caseins. A significant G×D interaction was found only for α s1-CN concentration, which decreased (-10%) when AA goats shifted from D100 to D65. In conclusion, high energy input consistently improved total casein yield beside genotype. The higher casein yield of AA goats mainly depends on α s1-CN biosynthesis; moreover, the lower presence of α s1-CN in FF goat milk may be partially counterbalanced by the other caseins.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
