Index selection in terminal sires improves early lamb growth

Area of Science:

• Animal Science
• Genetics
• Sheep Production

Background:

• Terminal sires (TS) are crucial in UK sheep crossbreeding, influencing approximately 71% of market lambs.
• Early growth of crossbred lambs significantly impacts farm profitability.

Purpose of the Study:

• To assess the effectiveness of index selection in terminal sires (TS) for improving birth weight (BW) and average daily gain (ADG) in crossbred offspring.
• To compare the efficacy of this selection strategy across different TS breeds (Charollais, Suffolk, Texel).

Main Methods:

• Selected high and low lean growth index rams from Charollais, Suffolk, and Texel breeds.
• Mated selected rams to Welsh and Scottish Mule ewes, rearing 6,515 crossbred lambs commercially.
• Recorded lamb weights at birth, 5 weeks, and 10 weeks, calculating ADG from birth to 10 weeks.

Main Results:

• Lambs sired by high index rams showed significantly greater BW, 5-week weight, 10-week weight, and ADG across all breeds.
• Suffolk-sired lambs exhibited the heaviest weights and highest ADG, while Charollais-sired lambs were the lightest with the lowest ADG.
• Significant differences in growth traits were observed between high and low index sires within Charollais and Texel breeds, but not Suffolk.

Conclusions:

• Index selection in terminal sires effectively enhances the growth performance of commercial crossbred lambs.
• Breed-specific responses to index selection were noted, with Texel and Charollais showing more pronounced effects than Suffolk.
• The findings support the use of index selection in terminal sires to improve lamb growth in extensive production systems.