Postpubertal sexual development in merino rams after differential feeding through puberty

Area of Science:

• Animal Science
• Reproductive Biology
• Nutritional Physiology

Background:

• Nutritional programming during early development significantly influences livestock growth and reproductive capacity.
• Understanding the long-term effects of early nutrition on Merino ram lambs is crucial for optimizing breeding programs.

Purpose of the Study:

• To investigate the impact of differential early-life nutrition on the growth, scrotal characteristics, and semen quality of Merino ram lambs.
• To determine the persistence of these nutritional effects when rams are subsequently provided with a common plane of nutrition.

Main Methods:

• Merino ram lambs were assigned to low, medium, or high energy intake levels from 7 to 12 months of age.
• Following the initial rearing period, all rams were maintained on a common diet from 12 to 25 months of age.
• Live weight, scrotal circumference, semen characteristics, and sexual activity were monitored throughout the study.

Main Results:

• Initial differences in live weight and scrotal circumference between nutritional groups were significant but diminished over time under common feeding.
• Most ejaculate characteristics showed no significant differences between groups, with the exception of sperm density.
• Sperm density was significantly higher in the medium nutrition group compared to the low nutrition group at the end of semen collection.

Conclusions:

• Differential nutrition in early life affects some reproductive traits in Merino ram lambs, but these effects are largely reversible with adequate nutrition.
• While live weight and scrotal circumference differences resolve relatively quickly, some semen parameters like sperm density may show more persistent effects.
• The study highlights the complex interplay between early nutrition, growth, and reproductive development in rams, even amidst seasonal influences.