Repeatability and effect of age on reproductive characteristics in Santa Ines rams

Due to the importance of the early selection of Santa Ines rams in Brazil, we have estimated the repeatability and verified the effects of age on seminal characteristics, scrotal circumference and body weight in 51 Santa Ines rams aged 6 to 26 months during one year. Animals were divided by age: group 1 (6 to 12 months) and group 2 (12 to 26 months) and they were kept in semifeedlots, receiving hay, concentrate and mineral supplement. Body weight, scrotal circumference and semen characteristics were evaluated once a month. The age groups did not influence sperm volume, sperm mass movements, sperm motility and sperm vigor. There were differences between age groups for sperm concentration, body weight and scrotal circumference which were higher in adult sheep (group 2). The major defects average also was different between groups, as the presence of sperm defects related inversely to age. Correlations between mass movement, motility and vigor were high and significant (P<0.01). The repeatability ranged from 0.39 (volume) to 0.09 (major defects), generally, low to those seminal characteristics. We conclude that multiple reviews of the seminal characteristics are necessaries to verify the reproductive efficiency of Santa Ines rams.

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