Factors affecting adjusted milk yield for lactation length in Egyptian buffaloes and their pattern of inheritance

A total of 3 623 lactation records of Egyptian buffalo cows were used to develop additive and multiplicative correction factors for lactation length and to study the effects of some genetic and nongenetic factors on the productive traits. Various criteria used to compare the effectiveness of the correction factors confirmed that both the types of correction factors were equally accurate. Sire of the cow significantly affected all traits studied. Lactation length increased up to the third parity, and dry period and calving intervals decreased (P<0.001) with advancement of parity. Spring calvers had higher (P<0.001) actual milk yield and longer lactation length as compared to those calving in other seasons. Genetic and phenotypic correlations among production traits were highly significant. Heritability estimates for production traits, based on paternal halfsibs ranged between 0.055 and 0.132.