Abstract
Records of 354 Holstein Friesian (HF) and Brown Swiss (BS) cows born from 1986 to 2006 at Las Margaritas research station, under subtropical conditions of Mexico, were analyzed to estimate milk yield per lactation (MYL, n = 1229), milk yield per day (MYD, n = 1227), milk yield per calving interval (MYCI, n = 929), lactation length (LL, n = 1229), calving weight (CW, n = 1164) and efficiency of milk production (EMP, n = 890). The cows were daughters of 144 sires and 232 dams. Models included breed of cow (2 classes: HF and BS), calving year (22 classes: 1989-2010), calving season (3 classes: cold, from November to February; dry, from March to June; and rainy, from July to October), lactation number (4 classes: 1, 2, 3 and ≥4), linear (except for CW) and quadratic (except for MYD and CW) effect of lactation length and linear effect of calving weight (except for LL). The random effect, other than the error term, was sire of the cow nested within breed of cow. Holstein Friesian cows yielded 261, 0.8 and 0.7 kg more milk per lactation, per day and per calving interval, respectively, than BS cows. In addition, HF cows were more efficient (p 0.05). Cows that calved in the cold season had greater (p<0.05) MYD, MYCI and EMP than cows that calved in the dry and rainy seasons. Lactation length was similar among cold, dry and rainy seasons.
Highlights
There are constraints on livestock production that can be addressed by improving the genetic potential of the animal; examples include: feed conversion efficiency, female productivity and fertility, influencing sex ratios, resistance to parasites and pathogens and quality attributes such as nutritional content and meat texture (Crute and Muir, 2011)
The objective of the present study was to evaluate the effects of breed, calving season and lactation number on milk yield traits, efficiency of milk production and calving weight of Holstein Friesian and Brown Swiss cows kept under subtropical conditions of Mexico
Breed of cow and calving season were highly significant sources of variation for all traits studied, except for lactation length, while calving year was highly significant for all milk yield traits and cow weight
Summary
There are constraints on livestock production that can be addressed by improving the genetic potential of the animal; examples include: feed conversion efficiency, female productivity and fertility, influencing sex ratios, resistance to parasites and pathogens and quality attributes such as nutritional content and meat texture (Crute and Muir, 2011). One of the most common ways of increasing dairy production in the tropics and subtropics is through importation of breeds with superior genetic potential from other countries either for use in purebred breeding or in crossbreeding with local breeds (McDowell, 1985). In Mexico, some researchers have compared Holstein Friesian and Brown Swiss cows under tropical and subtropical conditions based on reproductive and milk yield traits (Becerril et al, 1981; Calderón-Robles et al, 2011). Comparison of these two dairy breeds based on efficiency of milk production and live weight, Corresponding Author: Ángel Ríos-Utrera, Researcher in Genetics and Animal Breeding. Paso del Toro, Veracruz, México, 94277, Tel.: +52(229)2622222
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