Download e-book for iPad: Animal Science. Reproduction, Climate, Meat, Wool by N. T. M. Yeates

By N. T. M. Yeates

ISBN-10: 0080182097

ISBN-13: 9780080182094

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Extra resources for Animal Science. Reproduction, Climate, Meat, Wool

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For instance, it has been claimed that the oestrous cat, watching the males fight, is thereby appropriately conditioned for fertile service; whereas man-arranged matings, in which the female is placed with a selected male, are lowly fertile in comparison. By analogy with this, Van Demark and Hays ( 1 9 5 2 ) found that cows have enhanced motility of the reproductive tract if they spend some time, prior to actual service, with the bull. On approach of the bull, the oestrous cow apparently experiences successive waves of increasing uterine contractions, culminating at the time of ejaculation in a tetanic spasm of the uterus.

In general however, volume and density are inversely related, so that ram semen, although low in volume, has 3 a higher density of spermatozoa (average 3 m i l l i o n / m m ) than bull semen 3 (average 1 m i l l i o n / m m ) and both of these are much denser than boar semen 3 (average 1 0 0 , 0 0 0 / m m ) (Anderson, 1 9 4 5 ) . A broadly similar inverse relationship between the volume of semen and its concentration of metabolizable carbohydrate is also found. Thus, although the volume of semen ejaculated by the boar may be 100 times that of the bull, boar semen contains only about 9 mg fructose/100 ml semen or 1 / 1 0 0 the concentration of this sugar in bull semen (Mann, 1 9 4 6 ) .

N o deleterious changes of any kind appeared in semen volume, sperm density, sperm motility or sperm morphology. Libido, as judged by speed of mounting and ejaculating, was also completely unaffected, however, the secretory function of the male accessory glands was noticeably REDUCED FERTILITY 51 affected by the underfeeding, and the concentration of fructose and citric acid in the semen decreased to about 30 per cent and 6 0 per cent respectively of the original levels. The experiment showed clearly, therefore, that the accessory glands respond more quickly to nutritive deficiency than do the testes.

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Animal Science. Reproduction, Climate, Meat, Wool by N. T. M. Yeates


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