Methods for the indirect estimation of testes weight and sperm numbers in Merino and Romney rams

Knight, T. W.

doi:10.1080/00288233.1977.10427337

Cited by 43 publications

(16 citation statements)

References 14 publications

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“…These values are somewhat less than the lower plateaus of number of sperm in the semen ( Figure 5). High correlations of testicular size with sperm output have been found in swine (Wilson et al, 1977;Egbunike and Elemo, 1978;Neely et al, 1980;Fent et al, 1983), sheep (Knight 1977(Knight , 1984, and cattle (Hahn et al, 1969;Almquist et al, 1976;Coulter et al, 1976;Neely et al, 1982). None of the studies compared lines that differed in testis size due to selection.…”

Section: Discussionmentioning

confidence: 97%

Effect of selection for size of testes in boars on semen and testis traits.

Huang

Johnson

1996

Journal of Animal Science

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ABSTRACT:The objective of this study was to evaluate the effects of selection for increased size of testes on semen and testis characteristics. Boars from a line selected for increased size of testes at 150 d of age (TS, n = 25) and a randomly selected control line (C, n = 18) were used. Semen was collected three times per week for 3 wk (TRT1) then daily for 3 wk (TRT2) beginning when boar age averaged 276 d. It was followed by a 4-wk period of one collection per week and then the TRT1-TRT2 sequence was repeated. After 64 collections, boars were castrated and testes were evaluated for sperm numbers. Volume of semen, percentage of motile sperm cells, and percentage of abnormal cells in the semen did not differ ( P > .05) between lines. Concentration of sperm cells in the semen was greater for TS boars at TRT 1 (35.0 million cells/mL, P < .10) and TRT 2 (29.5 million cells/mL, P < .01). Number of sperm cells per ejaculate was greater for TS boars (6.1 and 4.3 billion cells for TRT 1 and TRT 2, respectively; P < .05). Percentage of abnormal cells was less ( P < .05) for boars at the younger ages. Concentration of sperm cells was 16 to 18 million cells/mL semen greater ( P < .05) at the older ages. Significant differences in the shapes of the response curves with increasing collection number across lines and ages were found. These differences were small and not considered to be important. Line differences in testicular and epididymal sperm numbers and in daily sperm production were consistent with differences in semen traits. Repeatabilities of semen traits were between .16 and .74. Selection for increased size of testes can be used to improve the reproductive capacity of boars used for artificial insemination.

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Section: Discussionmentioning

confidence: 97%

Effect of selection for size of testes in boars on semen and testis traits.

Huang

Johnson

1996

Journal of Animal Science

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“…Horn length was measured from the base, along the outer curvature of the spiral, to the tip. Testicular circumference was taken at the widest point of the scrotum, and is a reliable proxy for testes mass in domestic sheep (Knight 1977). August measurements of testicular circumference are highly correlated with measurements of the same males during the rut (r = 0.84, d.f.…”

Section: Methods (A) Study Site and Populationmentioning

confidence: 99%

Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success

Preston

Stevenson

Pemberton

et al. 2003

Proc. R. Soc. Lond. B

295

240

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Male contests for access to receptive females are thought to have selected for the larger male body size and conspicuous weaponry frequently observed in mammalian species. However, when females copulate with multiple males within an oestrus, male reproductive success is a function of both pre-and postcopulatory strategies. The relative importance of these overt and covert forms of sexual competition has rarely been assessed in wild populations. The Soay sheep mating system is characterized by male contests for mating opportunities and high female promiscuity. We find that greater horn length, body size and good condition each independently influence a male's ability to monopolize receptive females. For males with large horns at least, this behavioural success translates into greater siring success. Consistent with sperm-competition theory, we also find that larger testes are independently associated with both higher copulation rates and increased siring success. This advantage of larger testes emerges, and strengthens, as the number of oestrous females increases, as dominant males can no longer control access to them all. Our results thus provide direct quantitative evidence that male reproductive success in wild populations of mammals is dependent upon the relative magnitude of both overt contest competition and covert sperm competition.

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“…Paired-testes mass was estimated from scrotal circumference at specific time points with a regression equation reported by Knight (1977) for Romney rams. Estimates of testes mass were used in defining the stages of the testicular cycle and in determining testicular growth rates and the total number of LH and FSH receptors in the testis.…”

Section: Testicular Size Measurementsmentioning

confidence: 99%

Prolactin regulation of testosterone secretion and testes growth in DLS rams at the onset of seasonal testicular recrudescence

Sanford

Baker²

2010

Reproduction

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Our objective was to test the hypothesis that prolactin (PRL) acts at both the pituitary and testis levels to regulate testosterone secretion in the adult ram. The focus was on the mid-regression to mid-redevelopment stages of a photoperiod-condensed 'seasonal' testicular cycle. DLS rams (six per group) were given daily s.c. injections of bromocriptine (4 mg) or vehicle during the entire period. Serum PRL concentration in control rams peaked at 103.4G22.1 ng/ml in late regression and then steadily declined (P!0.01) to 19.5G4.3 ng/ml, whereas PRL in treated rams was always %4.0 ng/ml. Suppression of PRL tended (P!0.10) to increase the amplitude of natural LH pulses (transition stages) or reduce the number of LH receptors in the testis (regressed stage), although neither change disturbed testosterone levels in peripheral blood. These subtle changes were accompanied by significant (P!0.05) alterations in the capability of the pituitary to release LH (85% more) and of the testes to secrete testosterone (20% less). These effects of PRL were unmasked when rams were given highly stimulative i.v. injections of GNRH (single 3 mg dose) and NIH-oLH-S24 (three 5 mg doses given 20 min apart) respectively. PRL insufficiency also appeared to slow down the 'seasonal' rise in FSH secretion and slightly delayed (2 weeks) the times when the testes began to grow and were first significantly (P!0.05) enlarged from the regressed state. We conclude that PRL is an important part of the intricate regulation of the pituitary-gonadal system in moderately seasonal DLS rams.

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Methods for the indirect estimation of testes weight and sperm numbers in Merino and Romney rams

Cited by 43 publications

References 14 publications

Effect of selection for size of testes in boars on semen and testis traits.

Effect of selection for size of testes in boars on semen and testis traits.

Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success

Prolactin regulation of testosterone secretion and testes growth in DLS rams at the onset of seasonal testicular recrudescence

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