Response to selection for fertility in a fall-lambing sheep flock

Area of Science:

• Animal Breeding and Genetics
• Reproductive Biology
• Sheep Production Systems

Background:

• Improving reproductive efficiency is crucial for sheep farming profitability.
• Fall lambing systems present unique challenges for fertility management.
• Genetic selection offers a sustainable method to enhance livestock traits.

Purpose of the Study:

• To evaluate the effectiveness of selective breeding for fertility in a fall-lambing sheep population.
• To quantify the genetic gain in fertility over 1.45 generations.
• To assess correlated responses in other production traits.

Main Methods:

• Utilized three flocks: selected (S), environmental control (EC), and genetic control.
• Calculated estimated breeding values (EBVs) for fertility using a single-trait animal model.
• Applied selection pressure on fertility in the S flock for five years.
• Analyzed correlated responses in body weights and litter size.

Main Results:

• Fertility EBVs increased more rapidly in the selected (S) flock (.0138/yr) than the environmental control (EC) flock (.0067/yr).
• A positive correlated response in fall litter size was observed in the S flock (.0087 lambs/yr).
• Selected flock showed improvements in 90-day weight and scrotal circumference, but declines in direct birth and weaning weights.

Conclusions:

• Selective breeding is an effective strategy to improve fertility in fall-lambing sheep.
• Genetic gains in fertility can be achieved without significant detrimental effects on other traits.
• EBVs accurately predict selection response in sheep fertility.