Izvorni znanstveni članak
The effect of lactation stage and parity, lambing season, and herd on fat and protein content in Pag sheep
The objective of this study was to evaluate the effect of lactation stage, parity, lambing season, and herd on fat and protein content in Pag sheep. Data included 21.033 test-day records of 2.332 ewes lambed between November 2003 and May 2008. Research was conducted in 32 herds (23 of them were reared in the south-western and 9 in the northeastern part of the Pag Island). Daily milk yield and milk components were recorded using AT4 method in the routine milk recording scheme. The stage of lactation, described by Ali and Schaeffer lactation curve nested within rearing area, had significant effect (P<0.0001) on fat and protein content. The lowest fat and protein content was between the 20th (north-eastern part) and 30th day of lactation (southwestern part) and increased towards the end of lactation. Parity also affected differences (P<0.0001) in milk components. The lowest estimated value was observed in the first and the highest in the eighth parity for both traits. Differences in fat and protein content as a result of lambing season were also observed (P<0.0001). Pag ewes lambed in December 2003 had the highest milk fat content, while the lowest value was observed in milk from ewes lambed in February 2004. Winter lambing ewes (December 2004) had the highest, while ewes lambed in December 2005 had the lowest estimated protein content. Flock nested within rearing area affected fat and protein content ignificantly (P<0.0001). Ewes reared in herds from north-eastern part of Pag Island had wider range of fat and protein content compared to ewes reared in herds from south-western part of Pag Island. The knowledge about effects that have influence on milk components in Pag sheep provides useful information to breeders in production organisation on their farms.
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