Environmental factors and ram influence litter size, birth, and weaning weight in Saint Croix hair sheep under semi-arid conditions in Mexico Fernando Sánchez-Dávila, Hugo BernalBarragán, Gerardo Padilla-Rivas, Alejandro S. del Bosque-González, José F. Vázquez-Armijo, et al. Tropical Animal Health and Production ISSN 0049-4747 Trop Anim Health Prod DOI 10.1007/s11250-015-0795-6
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Author's personal copy Trop Anim Health Prod DOI 10.1007/s11250-015-0795-6
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Environmental factors and ram influence litter size, birth, and weaning weight in Saint Croix hair sheep under semi-arid conditions in Mexico Fernando Sánchez-Dávila 1 & Hugo Bernal-Barragán 1 & Gerardo Padilla-Rivas 3 & Alejandro S. del Bosque-González 1 & José F. Vázquez-Armijo 4 & Rogelio A. Ledezma-Torres 2
Received: 17 September 2014 / Accepted: 8 March 2015 # Springer Science+Business Media Dordrecht 2015
Abstract This study was conducted to evaluate the effects of season, year of lambing, parity, and the effect of ram on litter size, birth, and weaning weight through 8 years. Data of 4078 lambs sired by 21 rams and 1072 ewes were analyzed by a lineal model. There was a significant effect (P0.05). For litter size, the lowest numbers were obtained on the first lambing ewes (1.21±0.03) and the highest ones inewes starting from the fourth lambing (1.69± 0.04). Lowest body weights were found in lambs born from first lambing ewes (3.01±0.1 kg) and the highest ones in lambs born from the second (3.14±0.1) to the fifth (3.15± 0.2) lambing ewes. The lambing breeding season had a
* Fernando Sánchez-Dávila
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significant effect on weaning weight: the highest weaning weights were recorded in lambs born in spring (12.70 ± 0.20 kg) and the lowest ones in those born in summer (11.93 ± 0.20 kg). Lambing year had a significant effect (P0.05). With regard to weaning weight, there were differences over the years (between 11.3 and 13.8 kg) (Fig. 2).
1.7 1.6 1.5 lier size
The data of 4078 lambings were recorded from 2002 to 2010. The lambs were the progeny of 21 rams and 1072 ewes. Data were analyzed to determine the effect of year and season of lambing, parity number, and rams-sire effect on litter size, birth, and weaning weight, using a linear model in the SPSS (Statistical Package for Social Sciences Windows 2003). The comparison of means was carried out by Fisher’s least significant difference (LSD) with unequal numbers of observations. Interactions between the studied variables were carried out, but since there were not statistical effects, they were deleted from the model.
1.4 1.3 1.2 1.1 1 2002 2003 2004 2005 2006 2007 2008 2009 2010 lambing year
Fig. 1 Effect of lambing number, breeding season, and lambing year on litter size of Saint Croix sheep
Table 2 shows the results of the ram effect on the variables assessed in this study. With respect to litter size and birth weight, differences (P
