Genetic and environmental factors affecting perinatal losses of calves in Holstein breed in Cuba

The frequencies of abortion (AB) and total perinatal losses (TL = AB + stillbirth) of 184 871 records of Holstein cows calving from 1980 to 1988 were studied with the objective of estimating the principal environmental and genetic factors affecting AB and TL. The results of the first linear model showed highly significant effects (P < 0.001) for year and month of calving, whereas age at calving was significant (P < 0.001) only in nulliparous and primiparous females. According to this analysis, 13.8% of pregnant heifers did not produce a live calf, whereas these levels were 10.4, 9.3 and 9.5% for cows of second, third and fourth calving, respectively. In all the cases, it was evident that AB was the principal component of TL. The number of services per gestation (SG) had a significant (P < 0.001) effect on AB and TL, showing that for each two additional SG the level of AB and TL increased in 1%. From a genetic point of view, the sire of the fetus and the sire of the cow had significant effects (P < 0.001) in all the calvings, except the fourth. The heritability for direct effect (h_D²%) on AB and TL was 3.1, 2.2 and 3.7% for heifers, primiparous females and females at second calving, respectively; while (h_M²%) was 3.6, 2.3 and 1.5% for TL in such females. For the maternal effects (h_M²%) of the same traits, the results were 2.1 and 2.2, 1.7 and 1.8 and 1.6 and 1.7%. Genetic standard deviations were 3.4 to 5.6% for TL and direct effects (DE) and from 3.6 to 4.9% for maternal effects (ME), whereas the variability between breeding values of Holstein sires were from -6.9 to 11.5% for DE and from -8.5 to 6.5% for ME (in all the cases 100 was assigned for live calves and 0 for stillbirths). The genetic correlation between DE and ME was from -0.480 to -0.715 for AB and from 0.355 to -0.544 for TL. The results show the poor adaptability, but there are possibilities for selection and improvement.