Contents lists available at ScienceDirect Livestock Science journal homepage: www.elsevier.com/locate/livsci Genetic correlations between scrotal circumference, heifer fertility and stayability in Charolais–Charbray cattle G. Martínez-Velázquez a , A. Ríos-Utrera b , S.I. Román-Ponce c , J.J. Baeza-Rodríguez d , M.E. Arechavaleta-Velasco c , M. Montaño-Bermúdez c , V.E. Vega-Murillo b, ⁎ a Sitio Experimental El Verdineño, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Nayarit CP 63570, México b Campo Experimental La Posta, INIFAP, Veracruz CP 94277, México c CENID Fisiología y Mejoramiento Animal, INIFAP, Querétaro CP 76280, México d Campo Experimental Mocochá, INIFAP, Yucatán CP 97454, México ARTICLE INFO Keywords: Beef cattle Fertility Genetic correlations ABSTRACT Records from Charolais, Charbray and Charolais-Zebu crosses provided by Charolais–Charbray Herd Book de México, were used to estimate heritabilities and genetic correlations between scrotal circumference (SC, n = 18,972), heifer fertility (HF, n = 91,250), and stayability (STAY, n = 17,696). Measurements of SC were adjusted to 365 days limiting the age range from 320 to 410 days of age. The trait HF was coded as 1 if the heifer calved before 1,281 d of age and 0 otherwise. The trait STAY was defined as the probability of whether or not a cow calved a second calf before the six years of age given that, at least, the cow had calved a calf at three years of age or before. A three trait animal model and a Bayesian linear-threshold-threshold analysis were used to es- timate (co)variance components. Heritability estimates were 0.18 ± 0.02, 0.11 ± 0.01, and 0.26 ± 0.03 for SC, HF and STAY, respectively. Strong genetic correlations were detected between SC and STAY (0.76 ± 0.04), and between HF and STAY (0.57 ± 0.07), suggesting that selection of sires based on SC, and HF could lead to an improvement of STAY of cows in the Charolais–Charbray population of Mexico. A weak genetic correlation was found between SC and HF (-0.08 ± 0.10). Overall, the heritabilities and genetic correlations estimated for the three traits evaluated in this study support the feasibility of improving by selection the reproductive performance of the Charolais–Charbray population of Mexico. 1. Introduction Fertility of the beef herd is an important component of the economic efficiency in commercial cow-calf systems (Dickerson, 1970; Melton, 1995; Pravia et al., 2014). The economic impact of improving fertility of beef cows can be up to four times higher than the impact of improving growth and carcass traits in the beef herd (Van Eenennaam, 2013). The reproductive efficiency of beef cows is the outcome of many components representing a complex of lowly to moderately heritable traits (Koots et al., 1994; Van Melis et al., 2010; Cavani et al., 2015) which are not difficult to measure. These disadvantages can be overcome through indirect selection based on indicator traits as scrotal circumference (SC) for economically relevant traits affecting fertility of beef cows (BIF, 2010), however, SC it is difficult and expensive trait to measure. Favorable genetic relationships between SC in sires and re- productive traits of females has been documented by several studies supporting the feasibility of improving beef cattle fertility by selecting to increase SC in sires (Vargas et al., 1998; Morris et al., 2000; Terakado et al., 2015). Because positive response to indirect selection is based on favorable additive genetic relationships between pairs of traits, estimates of genetic parameters involving SC and female traits, such heifer fertility (HF) and stayability (STAY), are needed to predict the expected correlated response in cow fertility from selection on SC of sires. To evaluate the possibility of using SC as a selection criterion to improve fertility of Charolais and Charbray cattle, the objective of this study was to estimate heritabilities and genetic correlations between SC, HF and STAY in the Charolais–Charbray population of Mexico. 2. Materials and methods 2.1. Data and traits Records from Charolais, Charbray and Charolais–Zebu crosses https://doi.org/10.1016/j.livsci.2019.103914 Received 11 September 2018; Received in revised form 28 December 2019; Accepted 30 December 2019 ⁎ Corresponding author. E-mail address: vega.vicente@inifap.gob.mx (V.E. Vega-Murillo). Livestock Science 232 (2020) 103914 Available online 31 December 2019 1871-1413/ © 2019 Published by Elsevier B.V. T ELSEVIER