On the modelling of weights of kids to enhance growth in a local goat population under Tunisian arid conditions: the maternal effects

Abstract

To provide the local goat population with an adequate breeding scheme under an arid environment, this study aimed to evaluate the use of alternative models attempting to dissect the additive genetic (AG) and permanent environmental (PE) components of direct and maternal effects on weights of kids up to weaning. Records of 903 local kids over a period of 16 years were used in this study. Data were split into four groups corresponding to four periods along weight recording. Periods 1/2/3/4 contained weights in an interval with upper-lower limits of 1-20/25-60/65-120/125-150 days of age. Models including or ignoring maternal genetic or permanent environmental effects were fitted for all traits. For all periods, the best models were those including the AG component for both direct and maternal effects and the direct PE effect. Heritability estimates of both the direct and maternal effects ranged from low (0.02 for maternal heritability in P1) to moderate (0.17 for direct and maternal heritability in P2 and P3). Period 1 showed the lowest values for heritability of both direct and maternal effects, with also the largest estimate of the ratio of residual to total variance (around 0.2) compared with the other periods, with decreasing ratios as age increased (from 0.13 for P2 to 0.07 for P4). Both direct and maternal estimated breeding values (EBVs) showed high correlations for models fitting direct AG and PE (DGP) effects. For direct EBVs (DEBVs), correlations were above 0.99, indicating that the same animals are expected to be selected under any model that includes those components, regardless of the maternal effects included. For maternal EBVs, correlations were also high, but slightly lower than for the DEBVs between models including DGP effects and maternal genetic effects. Overall, our recommendation for genetic evaluations of direct and maternal effects in this population raised in extensive and harsh conditions is to use weight records preferably collected during the period of high milk production of dams, for which direct and maternal effects are expected to show full expression. Complete pedigrees and several generations of dam-progeny recording are needed to obtain a proper separation of environmental and genetic components.

Reproductive Efficiencies and Productive Potentials of Female Nigerian Indigenous Goat Breeds

“…Tesema et al, (2020) also observed that litter size is a source of variation for birth and weaning weights. Atoui et al (2022) noted in another study that the kid birth type had an effect on the body weights of Tunisian local goats' kids at all ages. Therefore, birth weight of a kid is a reproductive trait that can be affected by factors such as litter size (Yilgwan et al, 2012).…”

Assessing Environmental Effects upon Modeling the Individual Lactation Curve of a Local Goat Population in a Pastoral System

“…In the majority of agropastoral systems, milk represents only secondary production [ 1 ]; the main livestock product is the meat of lambs and kids. Milk is rarely obtained due to the nomadic management of herds and the insufficient infrastructure of rangelands, which hinders the collection and commercialization of milk [ 2 ].…”

“…Dairy farmers can optimize their management decisions and selection processes by using lactation curves as useful tools for informed planning and strategy implementation. Lactation curve knowledge makes it possible to estimate the total production of milk from several test days early in the lactation process [ 1 , 9 ] or from a single test day [ 10 ]. Such information helps to make decisions about specific milk production early in the lactation process [ 11 , 12 ].…”