Biomedical subjects
Publications and source records attributed to P J Dziuk.
The influence of the order of the ejaculate on the sex ratio was determined by ejaculating 1 of 5 experimental males 20 times over a period of 2 to 8 h. The sex ratio was noted for the offspring of ejaculates 1, 5, 10, 15 and 20 in a total of 32 litters. The sex ratio of these offspring did not deviate signigicantly from 50:50 (P greater than 0.1) for any ejaculate in the sequence.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
When hens were inseminated with an equal number of spermatozoa from one of 3 Leghorn (L) and one of 3 Columbian (C) cocks in the 9 possible L and C combination, a hierarchy of fertility was established based on the proportion of chicks sired by each cock. A similar hierarchy was established for 3 Duroc (D) and 3 Yorkshire (Y) boars by mating gilts in rapid succession to one D and one Y boar. A second hierarchy of fertility was established by inseminating hens with 40 x 10(6) spermatozoa from only one cock or by mating gilts to only one of the boars. The hierarchies for the cocks and boars were essentially the same for each method. Minor discrepancies were observed for males which appeared to be nearly equally fertile when used alone or in combination with another male. After homospermic insemination, the hierarchy of cocks was identical whether the ranking was based on the percentage of eggs fertilized or on hatchability of fertilized eggs. Similarly, the boars ranked highest in fertility by double mating had higher conception rates, higher embryonic survival rates and larger litter sizes when used alone. Heterospermic insemination and double mating appear to be more efficient and sensitive than methods of estimating fertility which depend on homospermic insemination of high or low numbers of spermatozoa, single matings or the examination of various characteristics of semen. The method of heterospermic insemination or double mating offers a simple and effective method of assessing the relative fertility of males.
Explore the source record for details and available documents.
Pony mares were observed from January to August for incidence of oestrus, duration of oestrus, length of the oestrous cycle and for ovulation and fertility after injection of HCG. From January to 15 May most mares showed oestrus but the duration of oestrus was quite variable and few mares ovulated in response to HCG. From 15 May to 17 August oestrous cycles were more regular and ovulation was induced within 40-50 h by an intramuscular injection of 1500-5000 i.u. HCG. Pregnancy was established by one mating at a fixed time after HCG in 20 of 69 mares. Degenerate eggs were recovered from the oviducts of anoestrous recently ovulated, mated, unmated and pregnant mares. The first polar body was formed before ovulation in 2 eggs and had not formed in 2 recently ovulated eggs flushed from the oviduct. The second polar body formed after sperm penetration 10-12 h after ovulation. After formation of pronuclei, the first cleavage division occurred at 20 h and the second at 32 h after ovulation. Oestrus was inhibited by progesterone administered by vaginal devices but occurred within 1-3 days in 12 of the 20 mares after withdrawal of the devices.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Fifty-five embryos were transferred from 4 Duroc donor sows into 4 crossbred recipient gilts. The embryo survival rate was 66%; 53% of eggs ovulated by donors were represented by live pigs at term. Three of the litters were obtained by hysterectomy of the recipients and introduced into a primary specific-pathogen-free herd, thereby saving the donor sows for subsequent use. Embryo transfer provided a method for exploiting the genetic potential of superior females.
To examine a possible relationship between the release of LH and increasing testosterone levels, blood samples were collected at 2-hr intervals for 24 hr from six mature rams with indwelling jugular cannulae. Although high levels of LH often preceded increases of testosterone, a consistent time relationship between these two hormones was not observed, nor was a diurnal rhythm established for either hormone. The following day, two rams were each injected intravenously with saline, 500 i.u. HCG, or 100 mug synthetic gonadotrophin-releasing hormone (Gn-RH) respectively. Immediately after the injection, blood was collected every 15 min for approximately 4 hr. After Gn-RH, the plasma LH rose 25- to 50-fold within 12 min and was elevated for more than 3 hr. A twofold rise of plasma testosterone followed this increase of LH and testosterone remained high until the end of the experiment. After HCG treatment, the level of testosterone rose threefold within 30 min and did not decline during the experiment, but there was no effect on the LH level. Saline treatment did not influence levels of LH or testosterone. It was concluded that daily fluctuations of testosterone and LH may occur independently, and no pattern is common to all rams. Treatment with Gn-RH results in a rise in both the testosterone and LH levels, but only testosterone is affected by HCG.
Explore the source record for details and available documents.
Explore the source record for details and available documents.