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C. O. WOODY and L. C. ULBERG

Summary.

No difference was found in the viability of unfertilized sheep ova transferred from donors maintained at 70 or 90° F to mated recipients maintained in constant 70° F. However, reciprocal transfers of fertilized ova indicated that the reproductive tract of ewes maintained at 90° F did not provide as favourable an environment for embryo development as did the tract of ewes maintained at 70° F. Control ewes maintained in constant 70° F had a significantly higher level of fertility than ewes maintained in a room with constant 90° F. Data obtained from ewes shifted from one air temperature to another indicated that most of the decrease in fertility due to the high air temperature had occurred by the end of oestrus in these ewes. Differences were noted in the fertility of two age groups of ewes, but this difference did not affect the ova before fertilization as indicated by transfer of ova between groups.

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C. O. WOODY and L. C. ULBERG

Summary.

Attempts to obtain fertilization of sheep ova recovered from follicles and deposited in the oviducts of the same ewes were unsuccessful. The recovery and transfer of postovulatory one-cell ova was successful if the paired ewes were closely synchronized as to the end of oestrus. Fertilization apparently was completed soon after the end of oestrus in mated ewes and ova from non-mated ewes were apparently still capable of normal fertilization and development at this time. Ova from non-mated ewes usually do not have corona cells present when recovered from the oviduct. Both fertilized and unfertilized ova appear to be able to withstand stress associated with a single transfer, but a second transfer greatly reduces the chances of a successful pregnancy.

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O. J. GINTHER, C. O. WOODY, S. MAHAJAN, K. JANAKIRAMAN and L. E. CASIDA

Summary.

The effect of oxytocin administration on the oestrous cycle was studied in sixteen uterine-intact and thirty-two surgically prepared unicornual heifers. Unilateral hysterectomy was performed on Day 3 of the oestrous cycle and oxytocin or an equivalent volume of physiological saline was administered daily from Day 3 to Day 7 or 8. Oxytocin produced significantly shorter oestrous cycles in the intact heifers and in the unicornual heifers with the retained uterine horn adjacent to the cl, but not in the unicornual heifers with the retained horn opposite to the cl. These results strongly suggest that at least part of the effect of oxytocin is exerted through local, utero-ovarian channels. A unilateral effect of the uterus on the cl was demonstrated in unicornual heifers that did not receive oxytocin. The oestrous cycles were extended and the cl persisted when the retained horn was opposite to the cl, but not when the retained horn was adjacent to the cl.

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O. J. GINTHER, C. O. WOODY, K. JANAKIRAMAN and L. E. CASIDA

Summary.

A plastic coil was inserted surgically on Day 3 of an oestrous cycle into one uterine horn of each of ten heifers. Sham-operations were performed on five additional heifers. The oestrous cycles in which the cl was on the operative side were significantly shorter than the cycles in which the cl was on the non-operative side or the cycles of the sham-operated controls. The average cycle length when the cl was on the non-operative side was not significantly different from the cycle length of the sham-operated controls. These results indicate that a plastic coil in the cranial portion of one uterine horn of the heifer results in a unilateral `inhibitory' influence on the cl.

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K. JANAKIRAMAN, C. O. WOODY, S. P. AGARWAL, R. C. BHALLA, K. P. SHUKLA, B. A. GADGIL, N. C. BUCH and L. E. CASIDA

Summary.

The effects of IUDs on the occurrence of ovulation and the pituitary gonadotrophin content was studied in water buffalo heifers of the Surti breed. Thirty-six of these heifers were divided into four equal groups. Group 1 received sham operations, while Groups 2, 3 and 4 were fitted with plastic IUDs in the cranial region of the uterus either ipsilaterally or contralaterally (in relation to the side on which ovulation occurred) or bilaterally, 72 hr after the exhibition of heat. Treated heifers showed significantly shorter cycles than the controls (P<0·01). There was no difference between Groups 2, 3 and 4. Heifers were slaughtered after the onset of heat in post-IUD-insertion cycles. Eight of the nine heifers ovulated in the control group, but only three in the group fitted with bilateral IUDs and one each in the groups fitted with ipsilateral and contralateral IUDs. The other ovarian characters studied did not show any significant differences among the four groups.

The anterior pituitaries from these heifers in different groups were freeze-dried and assayed for lh and fsh. Neither lh nor fsh activity was statistically different among treatment groups.

The results of this experiment suggested that an IUD, when present in one horn, also affects the adjacent ovary of the opposite horn to induce shorter cycles. This contralateral effect may be mediated systemically either at the level of the pituitary, the hypothalamus, or both. It is not possible to rule out transmission of a uterine factor from the IUD-horn to the non-IUD horn.