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Biomedical subjects

H R Tervit

Publications and source records attributed to H R Tervit.

51 records · Page 3Linked to original sources
PubMed1981

The effect of suckling upon the endocrine changes associated with anoestrus in identical twin dairy cows.

Identical twin pairs of dairy cows (one twin being placed with 4 calves for multiple suckling while the other was machine milked) were used to study the hormonal changes associated with anoestrus. Experiments were conducted to examine the effect of multiple suckling on the interval to first oestrus post partum, concentrations of LH and progesterone post partum, and the LH response to LH-RH or oestradiol-17 beta. The effects of hormone therapy on anoestrus were also examined. Multiple suckled cows had a 5-9-week longer interval to first oestrus post partum than did their non-suckling twins in all trials. There were no significant differences between the suckling and non-suckling cows in basal plasma levels of LH. The suckling cows showed a delay of 2 and 6 weeks post partum in their response to LH-RH and oestradiol-17 beta respectively when compared with their non-suckling twins. Treatment with a progesterone-releasing intravaginal device and bromocriptine to lower prolactin levels did not reduce the interval to the first post-partum oestrus while treatment with the progesterone device and PMSG reduced the interval to both first oestrus and conception. These findings suggest that suckling affects the response of the hypothalamic-pituitary axis to both LH-RH and oestradiol in the post-partum cow.

Anestrus↗
PubMed1980

Non-surgical embryo transfer in cattle.

Embryos collected surgically from donors superovulated with PMSG and synchronized with either prostaglandin F(2)alpha or progestagen impregnated sponges were transferred non-surgically to prostaglandin or progestagen synchronized recipients. One embryo was transferred to the uterine horn ipsilateral to the corpus luteum either through a flexible catheter introduced through a steel tube and passed to the uterine tip, or through a Cassou inseminating gun passed approximately 6 cm into the horn. Of 16 recipients receiving 5 or 6 day old embryos through the catheter (1976), 6 (38%) were palpated pregnant at 42 days and 4 (25%) subsequently calved. Of 16 recipients receiving 7 or 8 day old embryos through the straw and 16 through the catheter (1977), 10 (63%) and 3 (19%), respectively, were palpated pregnant (P<0.05) and 8 (50%) and 3 (19%), respectively, had normal embryos at slaughter 4 to 29 days after palpation (P reverse similar0.10 ). Forty 7 to 9 day old embryos were transferred through the straw in 1978. Eighteen (45%) of the recipients were palpated pregnant and 16 (40%) had normal embryos at slaughter 98 to 168 days after palpation. The success of the transfers in 1978 was affected by embryo quality [good vs poor embryos; 64% vs 22% recipients pregnant (P<0.01) and 59% vs 17% embryos surviving to slaughter (P<0.05)]. Also, in 1978, pregnancy rate was affected by the time taken to transfer the embryo with the highest rate achieved with the fastest transfers (P<0.10, b = -0.47). Injection of Indomethacin near the time of transfer, synchronization between donor and recipient onset of estrus and embryo age did not affect pregnancy rates. The pregnancy rate achieved after the transfer of good quality embryos by the straw technique was equal to that expected from surgical techniques.

Journal Article↗
PubMed1980

Temporal relationship between plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F and neurophysin I/II around luteolysis in sheep.

Plasma concentrations of neurophysin I/II (N-I/II), 13,14-dihydro-15-keto-prostaglandin F (PGFM) and progesterone were measured by radioimmunoassay in plasma samples collected from four sheep at hourly intervals between 0700 and 1900 h from Days 12-17 of the estrous cycle. Plasma samples were also collected from a fifth sheep at 2-hourly intervals during Days 12-16 of the cycle. In all sheep, intermittent surges in the plasma concentrations of PGFM and N-I/II occurred during the period of luteal regression. On at least one occasion in each sheep a surge in the plasma concentration of N-I/II was observed coincident with a rise in PGFM concentrations. In general, the highest levels of N-I/II were observed early in luteolysis (Days 13-14 of the cycle) while the corresponding levels of PGFM in plasma were maximal around Day 15 when luteolysis was well advanced. It is suggested from this temporal data that oxytocin, which is considered to be released in association with N-I/II, may play an important role in ovine luteolysis by stimulating the secretion of prostaglandin F from the uterus during days 13-15 of the estrous cycle.

Animals↗
PubMed1976

Jugular levels of 13, 14-dihydro-15-keto-prostaglandin F and progesterone around luteolysis and early pregnancy in the ewe.

Six non-pregnant ewes at day 12 of the estrous cycle each had a day-12 embryo transferred into the uterine horn ipsilateral to the corpus luteum, and 4 non-pregnant ewes at day 13 each had a day-13 embryo similarly transferred. Four control ewes, 2 at day 12 and 2 at day 13 received sheep serum into the uterine horn ipsilateral to the corpus luteum. Jugular blood samples were taken at 2-hourly intervals for 3 days post-surgery, then twice-daily for a further 4 days, and the plasma radioimmunoassayed for progesterone and 13, 14-dihydro-15-keto-prostaglandin F. All control ewes exhibited estrus within the expected time range and pulsatile peaks of 13, 14-dihydro-15-keto-prostaglandin F occurred coincident with declining progesterone levels. With one exception, the recipient owes had prolonged cycles and those ewes found pregnant at necropsy, 30 days after transfer, showed no progesterone decline and no pulsatile peaks of prostaglandin during days 12 to 16 after estrus. These observations suggest that the presence of the embryo at a critical stage after mating suppresses the release of uterine prostaglandin F2alpha.

Animals↗
PubMed1975

Experiments on egg transfer in the cow and ewe: dependence of conception rate on the transfer procedure and stage of the oestrous cycle.

The effects on embryo survival of procedures used in transferring eggs non-surgically were investigated in three experiments in ewes and heifers. In Exp. 1, two techniques for introducing eggs into the uterus through the cervix in heifers were compared; namely (i) deposition of the eggs high into the uterine horn or (ii) into the body of the uterus. Both methods were followed by inflation of the uterus with carbon dioxide. Out of a total of 34 heifers, only one became pregnant by the use of Method (i). Non-surgical egg tansfers early (Days 3 to 5) or later (Days 6 to 9) in the oestrous cycles of heifers were carried out in Exp. 2. Three transfer procedures were compared: (i) pipette transfer of an egg into the body of the uterus through the cervix (control), (ii) the control procedure performed under Fluothane anaesthesia, or (iii) followed by inflation of the uterus with carbon dioxide. Wide transfers carried out early in the cycle, pregnancies resulted in 1/10, 0/10 and 1/10 of the heifers in the control, carbon dioxide and Fluothane groups, respectively. With late transfers, 7/20, 1/10 and 8/20 heifers became pregnant in the respective treatment groups. This trend for pregnancy rate to be improved when late transfers were done in the control and Fluothane groups was significant only at the 10% level of probability when both groups were pooled. It was tentatively concluded, however, that non-surgical transfers of fertilized eggs to heifers may be best done during mid-cycle, after Day 6. Fluothane anaesthesia did not improve conception rate. Inflation of the uterus with carbon dioxide appeared to be deleterious when used at the mid-cycle stage in heifers. In Exp. 3, it was found that inflation of the ewe's uterus with carbon dioxide or nitrogen following the surgical thansfer of an egg did not affect the incidence of pregnancy. The introduction of 50 mul liquid Fluothane into the lumen of the uterus was embryotoxic.

Animals↗