Sexual performance of rams in serving capacity tests predicts success in pen breeding.
TL;DR: It was concluded that serving capacity tests, properly conducted, can be used to predict ram mating performance and thus aid in establishing more efficient ram-to-ewe stocking rates.
Abstract: The purpose of this study was to determine the extent to which sexual performance (serving capacity) tests can be used to predict the sexual behavior and reproductive success of rams in the context of pen mating. Standard serving capacity tests were used to select four low (LP) and four high-performing (HP) rams from a population of 94 yearling males. Each selected ram was then exposed to approximately 30 estrus-synchronized ewes for a 9-d period. Ejaculations observed and mounting marks left on ewes confirmed the greater (P less than .001) sexual activity of the HP rams in the field. In addition, ewes exposed to HP rams had a higher lambing percentage, more lambs born, and more live lambs born per ewe. Ram classification was not related (P greater than .60) to the number of lambs born per ewe lambing (prolificacy). It was concluded that serving capacity tests, properly conducted, can be used to predict ram mating performance and thus aid in establishing more efficient ram-to-ewe stocking rates.
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TL;DR: Major areas controlling sexual motivation and performance in males include the mesolimbic dopamine (DA) system, the medial preoptic area (MPOA), the amygdala, and the bed nucleus of the stria terminalis (BST).
Abstract: Male sexual behavior comprises a complex pattern of genital and somatomotor responses. Hormones act via receptors in brain, spinal, and peripheral sites to bias sensory inputs and motor outputs to favor sexual responsiveness. Copulation includes mounts, intromissions, and ejaculations, followed by sexual quiescence. After 6–12 ejaculations, male rats become sexually satiated. Neural controls include chemosensory inputs via the main and accessory olfactory systems to the medial amygdala, which transmits information directly and indirectly to the medial preoptic area (mPOA), which integrates sensory and hormonal information and elicits genital reflexes and copulatory patterns and contributes to sexual motivation. Genital sensory input arrives via the central tegmental field/dorsolateral tegmentum (including the subparafasicular nucleus) directly or indirectly into the mPOA. Output from the mPOA is via the paraventricular nucleus and midbrain and brainstem sites. The mesocorticolimbic dopamine pathway contributes motivational fervor, and neural programs for erection and ejaculation reside in the lumbosacral spinal cord. Dopamine facilitates male sexual behavior, whereas serotonin (5HT) is largely inhibitory, although stimulation of 5-HT1A receptors facilitates ejaculation. Norepinephrine has both stimulatory and inhibitory effects on copulation, via α1- and α2-adrenoceptors, respectively. Endogenous opioids play a complex modulatory role in all aspects of copulation. The brain areas that regulate male sexual behavior also influence other social behaviors.
372 citations
TL;DR: The sheep offers a unique model to study male sexual behavior and sexual partner preference and neurochemical and neuroanatomical studies suggest that male-oriented ram behavior may be a consequence of individual variations in brain sexual differentiation.
60 citations
Cites background from "Sexual performance of rams in servi..."
...…circulating levels of testosterone or other androgens and the level of sexual activity (Knight, 1973; Schanbacher and Lunstra, 1976; Howles et al., 1980); nor are there differences in the concentrations of testosterone between high and low libido rams (Perkins et al., 1992a; Stellflug, 2006)....
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...These rams are typically called low sexual performers because they inseminate fewer females (Perkins et al., 1992b)....
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...The majority of rams are female-oriented, estimated between 60% and 70% (Price et al., 1988; Perkins et al., 1992a; Roselli et al., 2004b)....
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TL;DR: It is suggested that the testicular volume and number of mounts exhibit seasonal variation in the Chios and Serres rams.
60 citations
Cites background from "Sexual performance of rams in servi..."
...Studies on the sexual behavior of males of different breeds suggest that rams of highly prolific breeds perform better than those of low prolificacy breeds [17,22] but the role of photoperiod and season in this phenomenon is not clear....
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TL;DR: Improved reproductive performance of Columbia, Rambouillet, and Targhee ewe lambs may be achieved by increasing age and weight at breeding and postweaning gain, according to a logit model analysis.
Abstract: Breeding ewes to lamb at 1 yr of age can improve profitability for some production systems. The first objective of this study was to evaluate the effect of age and weight at breeding and total postweaning weight gain on reproductive performance of ewe lambs. The second objective was to compare the effects of weight and age variables in four major sheep breeds (Columbia, Polypay, Rambouillet, and Targhee). Weights, ages, and the binary traits of fertility (pregnant or nonpregnant) and prolificacy (one lamb born vs. two or more) were collected on 2,055 ewe lambs at the U.S. Sheep Experiment Station, Dubois, ID, from 1984 through 1988. The effects of age and weight at breeding and total weight gain from weaning to breeding on fertility and prolificacy were analyzed with a logit model in a maximum likelihood analyses. Differences (P < 0.001) among breeds for fertility were identified, with a 93% fertility rate for Polypay ewe lambs compared with lower fertility rates in Columbia, Targhee, and Rambouillet ewe lambs (50, 60, and 75%, respectively). The percentage of multiple births (prolificacy rate) also was higher (P < 0.001) in the Polypay (47%) than in Columbia, Targhee, and Rambouillet breeds (1, 13, and 14%, respectively). Averaged across breeds, weight at breeding had a positive effect on fertility and prolificacy (P < 0.001), whereas total weight gain from weaning to breeding had a positive effect only on fertility (P < 0.027). In separate analyses for each breed, increasing age (P < 0.001) and weight at breeding (P < 0.001) increased the probability of pregnancy in Rambouillet ewe lambs. The probability of pregnancy for Targhee ewe lambs increased (P < 0.005) with weight at breeding. Increasing weight at breeding increased (P < 0.004) the probability of multiple births in all breeds. Increasing total postweaning weight gain increased (P < 0.007) the probabilities of multiple births in Rambouillet and Targhee ewe lambs. In conclusion, Polypay ewe lambs were superior in fertility and prolificacy to Columbia, Rambouillet, and Targhee under Western range conditions. Improved reproductive performance of Columbia, Rambouillet, and Targhee ewe lambs may be achieved by increasing age and weight at breeding and postweaning gain.
53 citations
Cites methods from "Sexual performance of rams in servi..."
...Only rams with acceptable semen tests were used (Perkins et al., 1992)....
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