ESTIMATES OF ADDITIVE AND HETEROTIC GENETIC EFFECTS FOR THE FARROWING INTERVAL OF SOWS IN A TROPICAL ENVIRONMENT

Abstract

Information from 1259 first farrowing intervals (FI) from Duroc (D), Hampshire (H), Landrace (L) and Yorkshire (Y) sows and their crosses were obtained from the records of a commercial farm in the State of Yucatán, México, from 1981 to 1989. The climate of the region is dry-hot with rains in summer. Sows feeding during pregnancy and lactation was based on commercial diets with 12 and 14% of crude protein, respectively. Data on FI were analized using general linear models. The statistical model which described the data included the effects of year and season of the first farrowing, the additive direct and maternal genetic effects, the direct specific and the average maternal heterosis effects. Direct and maternal additive genetic effects had no significant influences on FI. The direct specific and average maternal heterosis effects were negative but nonsignificant (p>0.05). The average direct and maternal heterosis values were -4.35 and -1.77 days, respectively. In conclusion, the negative constants for the heterosis effects, although non significant (p>0.05), suggest a better reproductive performance for the crossbred sows as compared with the purebreds.