Evaluation of morphometric traits and productive and reproductive performance of Sipli sheep in Punjab, Pakistan.

Abstract

The study evaluated the morphometric traits, productive, and reproductive performance of Sipli sheep in Punjab, Pakistan, aiming to provide a baseline for breed characterization, management, and breeding strategies. The study was conducted at the Sheep Breeding Centre, involving the collection of morphometric data, productive traits (wool and milk), and reproductive parameters. Morphometric measurements, including body length, height at withers, and heart girth, were taken on 35 rams and 47 ewes. Wool samples (n = 33) were collected bi-annually from the same sheep during autumn and spring to assess fiber diameter, length, staple length, and wool yield. Milk yield and composition were analyzed from 14 ewes. Reproductive data, including pregnancy rates, birth type, and lambing rates, were collected during the spring and autumn seasons of 2021 and 2022. The data were analyzed using descriptive statistics, Pearson's correlation, and ANOVA with Duncan's multiple range test, in addition to evaluating four non-linear growth models (Brody, Von Bertalanffy, Gompertz, and Logistic) for growth curve analysis. Results revealed that rams had significantly larger body dimensions than ewes. The study showed a highly significant (p < 0.001) positive correlation between body length and diagonal body length (r = 0.814) and height at withers (r = 0.774) in rams. In lambs, body length increased with age, with a substantial reduction in the coefficient of variation, from 12.22% at 1-3 months to 8.81% at 10-12 months. The Brody model provided the best fit (R²adj = 0.6267; RMSE = 14.941) for growth curve analysis. Male lambs showed consistently higher weights than female lambs (p < 0.005) across all ages. Rams had a significantly higher medullated fiber content (19.27%) compared to ewes (12.56%), with autumn-sheared wool exhibiting thicker fiber diameters (34.94 µm). The pregnancy rate was 78% in the spring of 2021 and significantly reduced to 53.06% in the autumn of the same year. The highest lambing rate of 143.48% was observed in spring 2022. The study concluded that Sipli sheep demonstrate significant sexual dimorphism and the Brody model effectively described the growth dynamics in this breed. Environmental factors like the year of birth and seasons significantly impacted growth and reproduction. Male lambs and single births showed improved growth, with seasonal effects on wool production and significant variations in reproductive traits. These findings provide a basis for breeding practices by considering key phenotypic characters and their association with body weight. In the future, it is recommended that environmental effects should be included in selection programs to optimize growth performance, alongside further genetic studies.