Sheep & Goats

Genetic and non-genetic factors associated with growth curve parameters in lowland sheep

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Abstract

Growth functions provide a useful framework for describing animal growth trajectories and estimating biologically relevant parameters, such as mature weight (A) and maturity rate (K). This study aimed to investigate non-genetic factors associated with 3 growth curve parameters (A, B and K; with B representing integrated constant related to initial weight), estimate their (co)variance components and evaluate the effect of the number of weight records available after 730 days of age on these parameters in a lowland female sheep population. Data included 40,403 weight records from 3,757 female sheep. Each animal had ≥1 record within 7 days of birth, ≥2 records between 7 and 240 days, ≥1 record between 365 and 730 days, and 4 consecutive records after 730 days of age; for these latter records, the interval between any 2 records was ≥60 days. The Gompertz parameters (A, B and K) were estimated for each animal using all records up to 730 days of age, while varying the number of mature weight records (i.e., weights post-730 days) from the first to the first four. Outliers for each parameter were defined as values lying more than 1.5 à— IQR below Q1 or above Q3. A repeated measures analysis with animals treated as the repeated subject was then used to examine the association between function parameters and non-genetic factors, including birth and rearing type, number of records after 730 days, dam parity, animal and dam age at first lambing, contemporary group, and animal and dam heterosis and recombination loss coefficients. (Co)variance components for 3 growth curve parameters, across different numbers of post-730 day weight records were estimated. The estimates for parameters A, B and K ranged from 63.95 to 69.90 kg, 1.99 to 2.12 and 0.0081 to 0.0104 kg/day per kg mature weight, respectively. Dam parity and number of weights post-730 day were associated with all 3 parameters. Heritability (SE) estimates for parameters A and K increased slightly from 0.31 (0.05) and 0.18 (0.04) where one post-730 day weight was available to 0.37 (0.05) and 0.25 (0.04) where four such weights were used. Heritability (SE) estimates for parameter B declined slightly from 0.37 (0.04) when one post-730 day weight was considered to 0.34 (0.04) when two or more such weights were used. Increasing the number of post-730 day weight records from one to four strengthened genetic correlations between parameters A and B (-0.01 to -0.37), A and K (-0.50 to -0.66), and B and K (0.36 to 0.77). Results revealed genetic variability in growth curve parameters, supporting their use in genetic evaluations of lowland sheep, and indicated that including mature weight records (after 730 days) slightly increased the genetic variation in the A and K parameters.

Keywords: 2026

How to Cite:

Sharif, N., McHugh, N., McGovern, F., Boland, T., Pabiou, T. & Berry, D., (2026) “Genetic and non-genetic factors associated with growth curve parameters in lowland sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285521. doi: https://doi.org/10.31274/wcgalp.23730

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