Selection Criteria for Improving Fertility in Spanish Goat Breeds: Estimation of Genetic Parameters and Designing Selection Indices for Optimal Genetic Responses

Abstract

The aim of this study was to estimate genetic parameters for several female fertility criteria and to choose the most suitable selection index in Spanish Florida and Payoya goat breeds. In this study, we analyzed as fertility traits, the age at first kidding (AgFiKid), and the interval between the first and second kiddings (Int12Kid), between the second, third, and remaining kiddings (Int3toKid), and between all kiddings (IntAllKid) in 51,123 and 22,049 Florida and Payoya females, respectively. Genetic parameters were estimated by fitting animal models using restricted maximum likelihood (REML) methodology. We proposed six selection indices to compare the genetic responses for all traits included, based on a new selection index theory. The heritability and repeatability estimates of the traits were low, as expected. The genetic correlations among fertility traits covered a wide range of values from 0.07 (AgFiKid-Int12Kid) to 0.71 (Int3toKid-IntAllKid) in Florida and from −0.02 (AgFiKid-Int12Kid) to 0.82 (Int3toKid-IntAllKid) in Payoya. Overall, the results of this study indicate that IntAllKid gives the highest genetic responses in both breeds but is expressed late in a female’s life. However, AgFiKid and Int12Kid could be recommended as early selection criteria for female fertility in both breeds.

Genetic analysis of reproductive efficiency in Spanish goat breeds using a random regression model as a strategy for improving female fertility

“…For example, Jembere et al (2017) in their meta-analysis of several studies on dairy goat breeds reported h 2 values of 0.17 ± 0.012 for the age at first kidding, 0.002 ± 0.018 for the first kidding interval, and 0.09 ± 0.01 for the interval between all kidding. Similarly, in our previous study on estimating genetic parameters for the classical fertility traits in the Florida and Payoya breeds, we obtained very low h 2 estimates, varying from 0.01 for the interval between second, third, and remaining kiddings in Florida to 0.11 for the age at first kidding in Payoya (Ziadi et al 2021a). Besides, the higher expected genetic responses calculated using selection indices occurred when the interval between all kiddings was combined with the age at first kidding.…”

“…Genetic parameters of fertility in Spanish dairy goats were estimated only in one study for the age at first kidding and the different intervals between kidding in the Florida and Payoya populations (Ziadi et al 2021a) and, as expected for this kind of traits, the magnitude of estimates was relatively low. However, this study used a repeatability model and did not deal with fertility over a time trajectory.…”

“…The reasons for the apparent observed discrepancy between the Florida and Payoya breeds may be attributable to the differences in management practices and production systems, with Florida being raised under more intensive management, in addition to the genetic structure of the populations. For instance, for the process of culling females, 24.7% of Florida females are removed between the first and second parities compared with 14.8% in the Payoya breed, and then 52.7% of Florida females have more than six parities (78.6% in Payoya) (Ziadi et al 2021a).…”

“…To date, despite the economic importance of reproductive traits in dairy goats, there are very few studies to estimate their genetic parameters and none have carried out a longitudinal analysis with a random regression model. The most commonly used traits in the international genetic evaluation of female fertility are (1) age at first kidding (Garc ıa- Peniche et al 2012;Castañeda-Bustos et al 2014;Ziadi et al 2021a) and (2) different kidding intervals (Bagnicka et al 2007;Garc ıa-Peniche et al 2012;Castañeda-Bustos et al 2014;Atoui et al 2018;Ziadi et al 2021a). Nevertheless, their very low heritability estimates make it difficult to determine which traits must be used as a selection criterion to improve female fertility.…”

Effect of the rob(1;29) translocation on the fertility of beef cattle reared under extensive conditions: A 30‐year retrospective study

“…The fertility of the individuals was assessed using the reproductive efficiency (Re) parameter (Ziadi et al., 2021), estimated as the deviation in percentage of the number of calvings that an animal has at each age, from the number of calvings that it could have had in optimal conditions. In the Retinta breed, the optimum age at first calving was considered 2 years and one year for the optimal calving interval, as in the majority beef cattle breed.…”