Genetic parameters estimation for preweaning traits and their relationship with reproductive, productive and morphological traits in alpaca

Abstract

The aim of this study was to estimate the genetic parameters for preweaning traits and their relationship with reproductive, productive and morphological traits in alpacas. The data were collected from 2001 to 2015 in the Pacomarca experimental farm. The data set contained data from 4330 females and 3788 males corresponding to 6396 and 1722 animals for Huacaya and Suri variants, respectively. The number of records for Huacaya and Suri variants were 5494 and 1461 for birth weight (BW), 5429 and 1431 for birth withers height (BH), 3320 and 896 for both weaning weight (WW) and average daily gain (DG) from birth to weaning, 3317 and 896 for weaning withers height (WH), and 5514 and 1474 for survival to weaning. The reproductive traits analyzed were age at first calving and calving interval. The fiber traits were fiber diameter (FD), standard deviation of FD (SD), comfort factor and coefficient of variation of FD and the morphological traits studied were density, crimp in Huacaya and lock structure in Suri, head, coverage and balance. Regarding preweaning traits, model of analysis included additive, maternal and residual random effects for all traits, with sex, coat color, number of calving, month-year and contemporary group as systematic effects, and age at weaning as linear covariate for WW and WH. The most relevant direct heritabilities for Huacaya and Suri were 0.50 and 0.34 for WW, 0.36 and 0.66 for WH, 0.45 and 0.20 for DG, respectively. Maternal heritabilities were 0.25 and 0.38 for BW, 0.18 and 0.32 for BH, 0.29 and 0.39 for WW, 0.19 and 0.26 for WH, 0.27 and 0.36 for DG, respectively. Direct genetic correlations within preweaning traits were high and favorable and lower between direct and maternal genetic effects. The genetic correlations of preweaning traits with fiber traits were moderate and unfavorable. With morphological traits they were high and positive for Suri but not for Huacaya and favorable for direct genetic effect but unfavorable for maternal genetic effect with reproductive traits. If the selection objective was meat production, the selection would have to be based on the direct genetic effect for WW but not on the maternal genetic effect that has been shown to have less relevance. Other weaning traits such as WH or DG would be indirectly selected.

Genetic parameters for medullated fiber and its relationship with other productive traits in alpacas

“…The traits analyzed were PM, MFD, FD, standard deviation (SD) of FD, greasy fleece weight (GFW) as fiber traits as described by Gutiérrez et al (2009); density (DE), crimp (CR) in Huacaya and lock structure (LS) in Suri, head conformation (HE), leg coverage (CO) as morphological traits as described by Cervantes et al (2010); weaning weight (WW) as described by Cruz et al (2017); age at first calving (AFC) for reproductive traits as described by Cruz et al (2015). Data were separately analyzed for the Huacaya and Suri genetic types.…”

“…Genetic parameters were estimated via a multitrait restricted maximum likelihood procedure applied to mixed linear models. Fiber traits were analyzed together with those morphological, preweaning and reproductive traits previously analyzed (Cruz et al, 2017) all together. The model fitted for DE, CR, LS, HE, CO and AFC was:…”

“…where y is the vector of observations, b is the vector of fixed effects, u is the vector representing the additive genetic effects, m is the vector representing the maternal genetic effects, p corresponds to the vector of permanent environments of individuals for fiber traits, e is the vector of residuals; X, Z, P and W are the incidence matrices for fixed, direct genetic, permanent and maternal genetic effects, respectively, I e is the identity matrix of equal order to the number of records, I p is the identity matrix of equal order to the number of permanent environmental subclasses, A is the numerator relationship matrix, R 0 is the residual covariance matrix among measurements on the same animal, G 0 is the covariance matrix for additive genetic effects, M 0 is the covariance matrix for maternal genetic effect for WW, C 0 is the matrix for covariance between direct and maternal genetic effects, P 0 is the covariance matrix for permanent environmental effects and ⊗ the Kronecker product (Cruz et al, 2017). The fixed effects for fiber traits were color with three levels (white, cream and black), month-year of recording as contemporary group with 50 levels, sex with two levels and age as linear and quadratic covariate (Cruz et al, 2017). For the morphological traits the fixed effects were color with three levels, sex with two levels and year of recording as contemporary group with 13 levels.…”

“…For the morphological traits the fixed effects were color with three levels, sex with two levels and year of recording as contemporary group with 13 levels. The fixed effects included in the models for WW were sex with two levels, color with three levels, year of calving as contemporary group with 14 levels, age at weaning as linear covariate and age of the mother as linear and quadratic covariate (Cruz et al, 2017). The fixed effects for reproductive trait were color with three levels, year of recording as contemporary group with 12 levels and age as linear and quadratic covariate (Cruz et al, 2017).…”

“…The selection for decreasing the alpaca FD has been extremely successful with an important genetic progress (Gutiérrez et al, 2009;Cervantes et al, 2010;Gutiérrez et al, 2011;Gutiérrez et al, 2014;Cruz et al, 2015 and2017) without worsening other traits. Therefore, selection against medullation is expected to also have success depending on the magnitude of the concerned genetic parameters.…”