Increasing Sperm Production in Mature Boars via Manipulation of Their Neonatal Environment

Abstract

The objective of this study was to determine if litter size during lactation (neonatal environment) influenced semen quality of mature boars. Boars born in October 2003 (n = 18) and in March 2004 (n = 18) were allocated into two treatments by crossfostering piglets one day after birth. Boars were nursed in litters of either six (small litter size) or litters of ten and greater (large litter size) through weaning. Following weaning, boars were raised under identical conditions comparable to those used in commercial production environments.

At 24 weeks of age, boars were trained to mount and collect. Boars were then put on a once per week collection regimen. Data collected and analyzed included body weight, testicular measurements, semen characteristics, and seminal plasma protein profiles. All data was analyzed using SAS and the proc GLM procedure.

While the boars continue to undergo weekly collections, analysis showed that litter size during lactation affected body weight. For boars born in the fall, boars reared in small litters were not significantly different (p<.05) than their counterparts reared in large litters except at weaning. In contrast, boars born in the spring and reared in small litters were significantly different (p<.05) than their counterparts reared in large litters at all ages except from 20 to 28 weeks of age. Beginning at 13 weeks of age, boars born in the fall also consistently weighed more and maintained larger testicular parameters than boars born in the spring.

There were no significant effects of litter size on semen quality although litter size did have an effect on the amount of seminal plasma proteins. However, results indicated that those boars reared in large litters had higher protein levels than those reared in small litters. At 35 weeks of age, the boars that nursed in large litters had 124.0 &#177; 7.3 relative units of the two seminal plasma proteins of interest while the boars that nursed in small litters had only 106.9 &#177; 4.3 relative units. It was also observed that all boars experienced a decrease in the amount of seminal plasma proteins between 35 and 45 weeks of age.

Although the initial results do not strongly support the idea of rearing boars in smaller litters, the possibility that this theory may provide producers with an economical method for increasing on farm production validates continued research. While these results only reflect the performance of the fall replicate through 60 weeks of age and the spring replicate through 38 weeks of age, further analysis of data collected over time will be necessary to make final conclusions on whether the neonatal environment influences the quality and quantity of semen in mature boars.