Treatment with Gonadotropin Releasing-Hormone in Prepubertal Gilts at Two Different Ages

To study the effect of GnRH in prepubertal gilts, seven crossbred gilts were treated with saline solution and 250 fig GnRH. In connection with saline and GnRH treatments blood was sampled every 15 min for 4 h, thereafter every 30 min for 2 h and every 60 min for 3 h, and finally every 3 h for 6 days. The ovaries were inspected by laparo-scopy just before and 6 days after GnRH treatment. The first GnRH treatment was undertaken when the gilts had a mean age of 141 days and mean body weight of 66 kg. One gilt was in prooestrus at this treatment. In the other 6 gilts the mean LH level was around 0.5 μg/l during a 4 h period after the saline injection. After the GnRH treatment a LH peak was seen with a mean duration of 4 h and a mean maximum level of 9.2 ± 2.07 μg/1. None of the gilts ovulated or showed oestrus within a week after GnRH treatment, which was confirmed by laparoscopy. The seventh gilt which was in prooestrus had high levels of oestradiol-17β (> 40 pmol/1) at GnRH treatment and no LH peak was seen during a 4 h period after treatment.Two gilts which had not shown oestrus at an age of 173 days and a mean body weight of 93 kg were treated a second time with 250 μg GnRH. The LH peak had a duration of 4 h and a mean maximum level of 5.3 ± 3.04 μg/l. Neither of these 2 gilts showed oestrus or ovulated within a week after GnRH injection. It was concluded that a single injection of GnRH results in a LH peak but is not enough to stimulate ovulation or oestrus in prepubertal gilts at a mean age either of 141 or 173 days.Key words: GnRH-treatment, prepubertal gilts, LH, oestradiol-17β     

Endocrine Changes after Mating in Pregnant and Non-Pregnant Llamas and Alpacas

Plasma concentrations of oestradiol-17ß, progesterone, 15-keto–dihydro–PGF_2α and luteinizing hormone (LH) were monitored in llamas and alpacas after mating with an intact male. Concentrations of LH and PGF_2α metabolite were high immediately after copulation. Ovulation occurred in 92% of the animals. The first significant increases in progesterone were recorded on day 4 after mating. In non-pregnant animals the lifespan of the corpus luteum was estimated to be 8–9 days. Luteolysis occurred in association with the release of PGF_2α. In pregnant animals, a transient decrease in progesterone concentrations was observed between days 8 and 18 in both species. No significant changes in PGF_2α secretion were registered during this period. Oes– tradiol–17ß concentrations were high on the day of mating, declined to low values on day 4, and started to increase again on day 8. Peak values after luteolysis in non-pregnant animals were significantly higher than those registered in pregnant ones. Furthermore, concentrations of oestradiol-17ß were elevated for a longer period in non–pregnant than in pregnant animals. The results suggest that progesterone from the corpus luteum exerts a negative influence on follicular activity in pregnant animals by reducing oes– tradiol-17ß secretion.     

Estrone and Progesterone Plasma Levels of Normal Cows and Cows with Parturient Paresis

Blood plasma concentrations of estrone and progesterone, calcium and inorganic phosphorus were measured in 22 cows (Swedish Red and White Breed) from 4 weeks prepartum up to 6 days post partum. Ten cows with parturient paresis had Ca levels below 6 mg/100 ml. Data from plasma analyses in individual cows were grouped in the following periods: 28–22, 21–15, 14–8, 7–6, 5–4, 3, 2, 1 day(s) before parturition and 1, 2, 3–6 days after parturition. Statistical comparisons of the levels of the hormones and the ratio progesterone/estrone did not reveal any significant differences between the paretic and normal cows at any time period. The results do not support the theories that high systemic levels of estrogens or an imbalance between estrogen and progesterone predispose towards parturient paresis.     

Peripheral plasma levels of estrone and progesterone in pregnant pigs treated with dexamethasone

Five pregnant pigs of the Swedish Landrace Breed were treated with dexamethasone i.m. injections during early and late pregnancy. The daily dose of dexamethasone was never more than 100 mg. There were no significant changes in the maternal plasma levels of estrone and progesterone during dexamethasone injections. The dexamethasone initiated neither abortion nor parturition.     

Equal calcitonin response in paretic and non-paretic cows after intravenous calcium infusion

Seventeen cows divided into 3 groups were studied: Group 1 consisting of newly delivered cows (1–3 days post partum) suffering from parturient paresis; Group 2 comprising newly delivered (1–4 days post parturn) healthy cows and Group 3 consisting of non-pregnant, non-lactating cattle. All animals were given an intravenous standard Ca infusion, and blood samples were obtained before treatment and at intervals during a 3-hour period thereafter. Plasma levels of calcitonin (CT), calcium (Ca) and inorg. phosphate (P) were determined. No significant difference for the mean CT response existed between animals in Groups 1 and 2. Blood levels of inorg. P increased significantly with time in animals of Groups 1 and 2 but not in animals of Group 3.The finding here of a similar CT response after Ca stimulation in both paretic and non-paretic cows demonstrates that the C-cells in both groups of animals have the same capacity to secrete CT.     

Diurnal variation of peripheral plasma levels of testosterone in bulls measured by a rapid radioimmunoassay procedure

A radioimmunoassay technique, using antibodies to testosterone-3-(O-carboxymethyl) oxime-bovine serum albumin, has been applied for the measurement of peripheral plasma levels of testosterone in bulls. The individual as well as the mean 24-hr. pattern of peripheral plasma levels of testosterone in the four bulls investigated showed three distinct peaks. The mean peripheral plasma level of testosterone peaked around 10 p.m., around 6 a.m. and around noon, the mean levels obtained at these times being 6.2, 6.1 and 4.2 ng/ml, respectively. In one bull an additional peak occurred around 2 a.m. (8.2 ng/ml). Significantly lower peripheral plasma levels of testosterone were observed between the peak values.     

Blood Levels of Calcitonin in Bulls of Varying Ages

Blood levels of calcitonin (CT), calcium (Ca), inorg. phosphate (P) and alkaline phosphatase (ALP) in 27 bulls of Swedish Red and White Breed (SRB) and 21 Swedish Friesian Breed (SLB) were studied. There was a significant lowering of Ca, P, ALP and CT with increasing age. The fact that the osteopetrotic syndrome is increasing with age in bulls and that the CT level in blood is decreasing with age does not support the idea that an increased CT discharge could be responsible for the osteopetrotic syndrome in bulls.