The feeding of 2.5 mgm. of diethylstilbestrol (DES) per head per day to growing wethers fed a dehydrated grass meal ration increased dry matter intake by 6 per cent and decreased dry matter digestibility by 2.4 per cent. The DES-treated lambs digested 5.4 cent (P<.05) more crude protein, 9.2 per cent (P<.20) more ether extract, 15 per cent (P< .01) less crude fibre, and 3.5 per cent (P<.01) less nitrogen-free extract. The use of a two stage in vitro digestion technique did not reveal any influence of a wide range of DES levels upon dry matter digestibility. The implantation of 12 mgm. DES in growing ewes and wethers increased pituitary and adrenal gland weights by 46 per cent (P<.005) and by 23 per cent respectively. The thyroid gland weights were decreased 21 per cent (P<.005). The gross histology of the pituitary gland was not found to be changed by DES treatment The use of I¹³¹ did not reveal changes in the activity of the thyroid gland following the feeding of 1.0, 2.0, and 2.5 mgm. DES per day to growing wethers. Lambs fed an all-concentrate ration and implanted with 12 mgm. DES gained more rapidly and efficiently than their controls The DES-treated lambs had a lower dressing percentage, and required less time to reach market weight. These results indicate that the action of DES in enhancing growth rate and efficiency of gain in the ruminant appears to be mediated by one or more mechanisms. First, DES may alter the digestive activities of the rumen microflora by selectively promoting their proteolytic activity and inhibiting their cellulolytic activity. It may, nevertheless, allow for an increased absorption of the degradation products of protein metabolism. These products may be present in a more readily digested form or may be more readily passed through the intestinal tract wall. Secondly, DES may stimulate growth of the anterior pituitary, resulting in an altered production of a number of the tropic hormones arising from this gland. With an increased growth of the anterior pituitary, an increased level of STH could account for a more efficient feed utilization. Control and DES-treated lambs utilize approximately the same amount of apparent digestible energy, however DES-treatment resulted in an increased growth rate. This must be due to an increased utilization of net energy, possibly associated with an alteration in tropic hormone production. / Land and Food Systems, Faculty of / Graduate

In order to investigate the nutritional requirements of ewes during late pregnancy and early lactation, two groups of ewes were given 90 gms. Digestible Crude Protein (D.C.P.) during pregnancy and 225 gms. D.C.P./head/day during early lactation. During the last six weeks of pregnancy ewes in Group II, provided with maintenance + 100%, requirement of Digestible Energy (D.E.) made significantly greater liveweight gains (P<0.01) than those in Group I and fed maintenance + 50%, D.E. During early lactation ewes in Group I, provided with maintenance + 150%, D.E. lost significantly less weight (P<0.05) than those in Group II which were given maintenance + 100%, D.E. There were no significant differences in milk yield and milk composition between the two groups, however pre-weaning lamb growth in Group I was significantly greater (P<0.05) than that in Group II. Average daily gain of weaned lambs (weaned at 8 to 10 weeks of age) given pelleted rations containing 20%, protein was significantly greater (P<0.05) than those given 16%, protein but there were no significant differences between lambs fed 20% or 13% and between 16%, or 13%, crude protein. A higher proportion of single lambs in the group given 13% protein may have accounted in part for the better gain of this group. Results of the digestion trial with these lambs indicated that there were no significant differences (P<0.05) in the dry matter digestibility and the protein digestion coefficient of the three types of pellets but the nitrogen retention was greatest in the lambs fed the 20%, protein. The results of the second experiment conducted, to study the effect of non-protein nitrogen in the form of urea on milk yield and milk composition of ewes indicated that there were no significant differences in milk yield, milk composition and milk urea N level of the three groups of ewes fed equal amounts of supplemental nitrogen, during early lactation, as soybean, soybean + urea and urea alone. Ewes fed soybean or soybean + urea had significantly lower plasma urea nitrogen levels (P<0.05) than those supplemented with urea alone. There was no significant difference between the plasma urea nitrogen level of the former two groups of ewes. There were no significant differences in the pre-weaning growth of lambs nursing ewes fed on pellets containing soybean + urea and urea alone but the lambs from ewes fed soybean made significantly slower (P<0.05) gain than those from the other two groups. .The reason for this slower rate of gain is difficult to explain. Results of the trial conducted to investigate the use of urea nitrogen in early weaned lambs indicated that the lambs fed on pellets containing soybean made significantly greater gains (P<0.05) than those on pellets containing urea as the sole source of supplemental nitrogen. There were however, no significant differences in weight gain of lambs fed on pellets containing soybean or soybean + urea and between soybean + urea or urea alone. There were no significant differences between plasma urea nitrogen level of lambs fed on soybean or soybean + urea containing pellets and these lambs had significantly higher (P<0.05) levels of plasma urea nitrogen than those fed on pellets containing urea alone. The variation in the blood urea level of the lambs was thought to be due to variation in protein intake. Results of the digestion trial with lambs showed that there were no significant differences in the protein digestion coefficients and dry matter digestibilities of these types of rations. Pellets providing nitrogen from soybean resulted in greatest nitrogen retention. Results show that urea did not influence the milk yield or milk composition of the ewes but it was a poor source of nitrogen for early weaned lambs. / Land and Food Systems, Faculty of / Graduate

Pressure changes and myoelectrical activity in the ovine rumen were investigated following the surgical implantation of fluid filled balloon-tipped tygon tubes and paired fine needle platinum electrodes. The correlations among rumen pressure change and myoelectrical spike burst duration, frequency and magnitude data from 447 7 one minute periods were determined in order to select a single reliable quantitative measurement of rumen motility. The results showed that all these parameters accurately reflect activity changes in the rumen. Myoelectrical spike burst duration was shown to be the most sensitive indicator and was used as the criterion for examination of lactic acid induced motility changes. Rumen motility was not affected by intraruminal introduction of 1000 ml of 0.15 or 0.7 M lactic acid at pH 2.0 via permanently implanted cannulae. Intravenous infusion of 2 concentrations of sodium lactate which increased blood lactate levels by approximately 20 mg% and 180 mg% respectively, also had no effect on rumen motility. Infusion of lactic acid solutions (250 ml) 0.15 or 0.7 M (pH 2.0, 4.0 and 6.0) intraduodenally via polyethylene cannulae exerted profound effects on rumen motility. Immediately following ( 1 min) the commencement of the infusion of lactic acid (pH 2.0), a short period of total inhibition of motility occurred which was followed by a rapid recovery of motility to near normal levels despite the continuation of the infusion. These initial short periods of inhibition and recovery continued for up to one hour following termination of infusion. Similar yet somewhat reduced responses were observed upon intraduodenal infusion of the lactic acid solutions at pH 4.0 and 6.0. These results suggest that inhibition of rumen motility in lactic acidosis may be caused primarily by lactic acid produced in the rumen entering the intestine and causing a stimulation of the enterogastric reflexes. / Land and Food Systems, Faculty of / Graduate

Reproductive physiology in production animals is a key economic component of longevity and profitability of animal farming. There are several components that can benefit or compromise adequate pregnancy periods. Sheep production is not only a very important economic activity for farmers around the United States, but sheep are also an important medical and surgical model to study human diseases. Our findings suggest that estradiol-17 beta could be involved in acute increased plasma volume early in gestation which can benefit overall gestation. We report that umbilical blood flow decreases upon nutrient restriction in adolescent ewes and does not recover upon realimentation. Finally, we suggest that a similar umbilical blood flow, placental development and plasma volume expansion in twins and singleton pregnancies could be enough to obtain similar birthweights in singletons and twins.

No abstract / Thesis (PhD)--University of Pretoria, 1942 / Includes bibliographical references (leaves 127-132). / Original document: Typescript / Production Animal Studies / PhD / Unrestricted

Experiments were initiated to determine whether exogenous estradiol-17beta (E2) and oxytocin (OT) can be used to dilate the cervix and improve transcervical embryo transfer (ET) procedures for sheep. However, there was concern that the E2-OT treatment may alter luteal function and that embryo quality would decrease as the superovulatory response to FSH increased. In Exp. 1, 32 ewes were assigned to a 2 x 2 factorial array of treatments. On d 7, ewes received an i.v. injection of either 100 micrograms of E2 in 5 mL of 1:1 ethanol:saline or 5 mL of 1:1 ethanol:saline; 12 h later, ewes received i.v. injection of either 400 USP units of OT or saline. Jugular blood was collected on d 7, 8, 9, 10, 12, 14, 16, and 18. Progesterone concentrations were unaffected by the treatments. Experiment 2 was conducted to determine the dose of pFSH needed to induce approximately six corpora lutea (CL). Ten-day Norgestomet implants inserted between d 8-12 of the estrous cycle were used to synchronize estrus in Hampshire and Hampshire x Dorset ewes (n = 23). Ewes received a total of either 0, 18, 27, or 36 mg of pFSH, which was injected i.m. at -24, -12, 0, 12, 24, and 36 h relative to implant removal. The dose at each respective time was 19.4, 19.4, 16.7, 16.7, 13.9, and 13.9% of the total. Ewes received 400 IU of PMSG i.m. at -24 h. The CL were counted laparoscopically on d 6 (d 0 = estrus). Number of CL increased linearly (P &amp;lt; .01) with dose of pFSH; there were 1.8, 3.6, 6.3, and 11.2 CL/ewe, respectively. Experiment 3 was conducted to determine the effect of the E2-OT treatment, mode of transfer or the interaction of E2-OT treatment x mode of transfer on embryo survival and development. Experiment 3 was conducted over two breeding seasons and across two trials. In the first trial ewes were assigned to one of three randomized treatments. Procedural limitations that were later overcome prevented a true 2 x 2 factorial design; therefore, transcervical transfer without hormonal treatment was excluded in the first trial. In the second trial, ewes were assigned to a 2 x 2 factorial array of treatments. On d 6 of pregnancy, embryos rating a fair or better were transferred into recipients either transcervically or laparoscopically. Recipients were administered either an E2 (d 6) - OT (d 7) treatment or an ethanol:saline-saline treatment following the same protocol as in Exp. 1. Embryos were recovered on d 12 in Trial 1 and d 14 in Trial 2. Embryos were evaluated morphologically for development and ranked on a scale of one to four; one represented no development and four represented development to the morphological stages associated with the day of collection. The treatments did not affect the percentage of embryos recovered after transfer or the percentage of embryos that showed some developed. However, there was an effect of mode of transfer on mean rank of embryo development; embryos transferred laporscopically developed further than embryos transferred transcervically (P &amp;lt; .01). This may have been an artifact of a technician effect between trials. There was an effect of E2-OT treatment on transcervical transfer (P &amp;lt; .01), indicating that it may be detrimental to transfer embryos transcervically without dilating the cervix. In conclusion, the E2-OT treatment did not affect luteal function, and the E2-OT treatment can be used to dilate the cervix and enhance success of transcervical transfer of embryos. A 400 IU priming dose of PMSG and a total dose of 27 mg of pFSH can be used to induce the target number of six CL. / Master of Science

Experiments were conducted to determine the effects of a treatment used to dilate the cervix for transcervical AI and embryo transfer on pregnancy or fertilization rates in sheep. Experiment 1 was conducted as a 2 × 2 factorial, with the main effects of estradiol-17β (E2) and oxytocin (OT). On d 6 of pregnancy, ewes received (i.v.) 100 μg of estradiol-17β, or saline; 10 h later, ewes received (i.v.) 400 USP units (20 mL) or saline. Blood samples were collected for progesterone analysis. Transrectal ultrasonography was used to determine pregnancy on d 25. Treatment did not affect (χ² , P > .05) pregnancy rates. For nonpregnant ewes, the period × E2 × OT interaction (P < .01) was significant. Experiments were conducted to evaluate the effects of oxytocin and(or) cervical manipulation on fertilization rates. In Exp. 2, nulliparous ewes were assigned to one of two randomized treatment groups: 1) saline or 2) oxytocin. In Exp. 3, multiparous ewes were assigned to one of two randomized treatment groups: 1) saline-cervical manipulation or 2) oxytocin-cervical manipulation. Ewes in Exp. 2 and 3 were laparoscopically inseminated. In Exp. 2 and 3, ewes received (i.v.) either 400 USP units of oxytocin or 20 mL of saline. In Exp. 2 and 3, oocytes and(or) embryos were collected. Treatment did not affect recovery, fertilization, or pregnancy rates in Exp.2 and 3. In conclusion, the treatment used to dilate the cervix in ewes to facilitate the transcervical AI or ET does not seem to affect fertilization or pregnancy rates. / Master of Science

No description available.

No description available.

No description available.