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ARS Home » Pacific West Area » Dubois, Idaho » Range Sheep Production Efficiency Research » Research » Publications at this Location » Publication #125599
Title: ESTROGEN SYNTHESIS IN FETAL SHEEP BRAIN: EFFECT OF MATERNAL TREATMENT WITH AN AROMATASE INHIBITOR.

Author
item ROSELLI, CHARLES - OREGON HEALTH SCIENCES
item RESKO, JOHN - OREGON HEALTH SCIENCES
item Stellflug, John
item STORMSHAK, FRED - OREGON STATE UNIVERSITY

Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2001
Publication Date: 7/1/2001
Citation: Biology of Reproduction. 2001. Suppl. 1. v. 64. p. 114.

Interpretive Summary: Selection for mating behavior is known to be heritable in several species, but it is not well known if selection for ewe reproductive traits affect mating behavior of rams. Thus, our objective was to determine if divergent (high vs low index)selection for a female trait (lambs born divided by age of ewe minus one)affects mating behavior of male offspring observed in close to natural conditions or during training to service an artificial vagina (AV) in a less than natural setting. Standard method of evaluating male mating behavior is a series of serving capacity tests (SCT) to estimate libido. In Exp. 1, ram classification consisted of exposing each ram (n=48) to three estrus ewes for 18,30-min periods. Thereafter, each ram that had not mounted or ejaculated during SCT was observed for sexual orientation in a 30-min preference test with access to restrained rams and estrus ewes. There was no difference (P > 0.2) in classed rams mounting (92 vs 78%) and ejaculating (88 vs 74%) between high line and low line, respectively. For Exp. 2,five, 30-min libido tests were conducted to assess mating behavior on 29 additional rams being trained to service an AV. In this study, rams mounting (73 vs 36%) and ejaculating (67 vs 29%) differed (P < 0.05) between high and low line, respectively. Our results indicate that long-term selection for litter size did not alter ram performance classed in close to natural conditions or affect incidence of male-oriented rams. Mating behavior observed at time of training to service an AV was decreased in low line compared to high line rams. We concluded that selection for female reproductive traits in sheep did not alter mating behavior patterns of male offspring, but test conditions such as retrained and unrestrained ewes and number of SCT can affect the outcome.

Technical Abstract: Selection for mating behavior is known to be heritable in several species, but it is not well known if selection for ewe reproductive traits affect mating behavior of rams. Thus, our objective was to determine if divergent (high vs low index)selection for a female trait (lambs born divided by age of ewe minus one)affects mating behavior of male offspring observed in close to natural conditions or during training to service an artificial vagina (AV) in a less than natural setting. Standard method of evaluating male mating behavior is a series of serving capacity tests (SCT) to estimate libido. In Exp. 1, ram classification consisted of exposing each ram (n=48) to three estrus ewes for 18,30-min periods. Thereafter, each ram that had not mounted or ejaculated during SCT was observed for sexual orientation in a 30-min preference test with access to restrained rams and estrus ewes. There was no difference (P > 0.2) in classed rams mounting (92 vs 78%) and ejaculating (88 vs 74%) between high line and low line, respectively. For Exp. 2,five, 30-min libido tests were conducted to assess mating behavior on 29 additional rams being trained to service an AV. In this study, rams mounting (73 vs 36%) and ejaculating (67 vs 29%) differed (P < 0.05) between high and low line, respectively. Our results indicate that long-term selection for litter size did not alter ram performance classed in close to natural conditions or affect incidence of male-oriented rams. Mating behavior observed at time of training to service an AV was decreased in low line compared to high line rams. We concluded that selection for female reproductive traits in sheep did not alter mating behavior patterns of male offspring, but test conditions such as retrained and unrestrained ewes and number of SCT can affect the outcome.