Polymorphism at the αS1-casein locus (CSN1S1) ingoats influences several milk production traits. Milkfrom goats carrying strong alleles, which are associatedwith high αS1-casein (αS1-CN) synthesis, has higher fatand casein contents, longer coagulation time and highercurd firmness than milk from goats with weak alleleslinked to low αS1-CN content. Nutrition also affectsthese milk properties; therefore, it is important to betterunderstand the interaction between dietary characteristicsand the CSN1S1 genotype in goats. This studyaimed to investigate the effect of fresh forage baseddiet or energy supplement on feeding behavior, milkproduction, and metabolic and hormonal parameters ofGirgentana goats with different genotypes at CSN1S1loci. From a group of goats genotyped by PCR at theDNA level, 12 were selected because they had the samegenotype for αS2-CN, β-CN, and κ-CN but a differentgenotype for αS1-CN: 6 were homozygous for strong allelesat the CSN1S1 loci (AA) and 6 were heterozygousfor a weak allele (AF). Goats of each genotype wereallocated to 3 subgroups and fed 3 diets ad libitumin a 3 × 3 Latin square design. The diets were sulla(Hedysarum coronarium L.) fresh forage, sulla freshforage plus 800 g/d of barley meal (SFB), and mixedhay plus 800 g/d of barley meal (MHB). Diet had astronger effect than CSN1S1 genotype. The SFB dietled to the highest energy intake, dry matter (DM) digestibility,and milk yield. The fresh forage diets (SFFand SFB) increased DM and crude protein (CP) intake,CP digestibility, and milk CN compared with the MHBdiet. The diets supplemented with energy (SFB, MHB)reduced milk fat and urea, improved CP utilization forcasein synthesis, and limited body fat mobilization, in accordance with a lower level of nonesterified fatty acidsand higher levels of glucose and IGF-1. With regard toCSN1S1 genotype, AA goats showed higher CP digestibilityand lower free thyroxine hormone and cholesterollevels than AF goats. Significant diet × genotypeinteractions indicated how AA goats, compared withAF goats, showed higher DM digestibility and milkyield when fed the SFB diet, which had more energy.A reduction in free triiodothyronine hormone occurredin AF goats fed the MHB diet, whereas no differenceswere observed in AA goats. These results demonstratehow goats with a higher capacity for αS1-CN synthesisexhibit more efficient energy and protein utilization,evident at the digestive level, and better productiveresponses to high-nutrition diets.
|Numero di pagine||11|
|Rivista||Journal of Dairy Science|
|Stato di pubblicazione||Published - 2013|
All Science Journal Classification (ASJC) codes