Analysis of the Non-Genetic Factors Affecting the Growth of Segureño Sheep

Abstract

A study was conducted to evaluate the effects of non-genetic factors on the growth behaviour of Segureña sheep breed. Growth related data (early weaning weight, late weaning weight and weight at 80 days of age) were taken from 59,704 lambs belonging to historical data from National Association of Segureño Sheep Breeders (ANCOS) during a period of 11 years. Statistical analyses were performed by using the multifactorial analysis of variance of IBM SPSS Statistics v.19 software. The model included non-genetic factors – lamb sex (S), birth season (N), herd (H), birth year (A) and birth type (P) – as main effects, the dam’s age at lambing and the lamb’s age when weighed as covariables, and the interactions between these factors. Results showed that all weights at developmental stages were significantly (P<0.001) affected by all factors, except for A and the covariable age of dams at lambing on lambs aged 80 days. Double interactions H×A, H×P and H×N were significant (P<0.001) for all variables, as well as the triple interaction H×A×P. Non-genetic factors have a very important role in the development and growth of the Segureña sheep breed, at different ages or growth stages, therefore a correction is necessary to increase the accuracy of direct selection on lamb weight at early weaning, late weaning and at slaughtering (80 days of age).

Key Words:

• Growth
• Interactions
• Multifactorial analysis
• Sex

Acknowledgements

The authors thank the National Association of Segureño Sheep Breeders (ANCOS). Special thanks go to Mr. José Puntas and Mr. Miguel Serrano for all their support in the field work.