Effects of crossbreeding on milk production and growth characteristics in dual-purpose cattle in the humid tropics

Crossbreeding effects were evaluated in three dual purpose bovine sub-populations in the tropics, and 5,040 lactations, 4,429 birth weights and adjusted weights at 205 [ 3,878], 365 [ 3,017] and 540 [ 2,276] days (PN, P205, P365 y P540, respectively) from Zebu cattle (CE) and its crosses with Holstein (HS), Brown Swiss (SP) and Simmental (SM). Additive direct breed effects (PG), heterozygosity (HT) and recombination loss (RC) were estimated by a regression analysis within breed group with mixed models. Evaluated fixed effects were herd and year of freshening, season, lactation number and offspring gender for milk yield (PL) and herd, birth year and season for growth traits. Random effects for PL were direct (animal) and permanent environment and for growth traits were genetic direct and maternal and permanent maternal environmental effects. PG/HS, PG/SP y HT/SM had effects (P<0.10) on PL while PG/SP, PG/SM, HT/SM and RC/HS on PN. PG/HS y PG/SP presented effects (P<0.10) on P205, P365 and P540 while PG/SM only on P205. HT and RC had effects (P<0.10) on P205, P365 y P540 for all crosses. Results hereby presented will allow the formulation of strategies for the use of additive and non-additive genetic effects of the crossbred populations present in the Mexican humid tropical regions.