The physiological responses of anovulatory ewes to the introduction of rams — A review

If pre-conditioned by a period of isolation from rams, prepubertally, seasonally or lactationally anovulatory ewes of many breeds can be stimulated to ovulate by the reintroduction of rams. The signal from the rams is partly pheromonal and activates neural connections between the main olfactory tract and the anterior hypothalamus. This leads to an increase in the frequency of pulses of luteinizing hormone (LH), a process which is essential for the induction of ovulation and is usually completed within a few minutes. The high pulse frequency stimulates follicular growth and oestradiol secretion by the ovaries. The subsequent build-up of oestradiol in the blood has two effects: in the short term (the first 2–12 h) it reduces the levels of follicle-stimulating hormone (FSH) and the amplitude of the LH pulses; in the long term (12–48 h) it induces preovulatory surges of both LH and FSH. The LH surge induces ovulation and the formation of a corpus luteum.In some ewes, the corpus luteum is normal and a normal luteal phase follows the first ovulation. In other ewes, the first corpus luteum secretes little progesterone and regresses within 6 days. A second LH surge is then released, inducing a second ovulation and the formation of an apparently normal corpus luteum. If the ewes are treated with progestagen before the rams are introduced, all the corpora lutea formed after the first ovulation appear to be normal. This appears to be effected both through a delay in the onset of the LH surge and through a direct action of progesterone on the ovary.     

Physiopathological Effects of the Administration of Chronic Cyanide to Growing Goats – A Model for Ingestion of Cyanogenic Plants

Ingestion of cyanogenic plants, such as cassava and sorghum, has been associated with goitre and tropical pancreatic diabetes in both humans and animals. Thus, the objective of the present study was to determine the toxic effects on the thyroid and pancreas in growing goats of prolonged exposure to potassium cyanide (KCN). Thirty-four male goats were divided into five groups dosed with KCN at 0 (control), 0.3, 0.6, 1.2 or 3.0 mg/kg daily for 5 months. Blood samples were obtained in order to determine the glucose, cholesterol, thyroxine (T₄), triiodothyronine (T₃) and thiocyanate concentrations and for haematological studies; pancreas and thyroid gland were collected for histopathological study. The group receiving the highest dose of cyanide showed lower body weight gains and carcase weights and a decrease in plasma T₃ concentrations compared to the control group. Reabsorption vacuoles in follicular colloid and normocytic normochromic anaemia were observed in the experimental animals. Inhibition of peripheral conversion of T₄ to T₃ is suggested. However, no diabetogenic effects were observed.     

The effect of tebuthiuron on the vegetation of the thorn Bushveld of the Northern Cape – a preliminary report

Abstract

Two formulations of tebuthiuron i.e. Graslan 20P and Graslan 40P are currently being evaluated in the Molopo area. Tebuthiuron was applied aerially at ten application rates, in combination with two application dates.

After only two seasons, the chemical has already shown a reasonable selectivity for the woody species. Of these, Acacia mellifera, A. reficiens and Grewia flava are very sensitive while A. erioloba and Dichrostachys cinérea are less sensitive and Boscia albitrunca seems almost resistant to the lower application rates (<1,0 kg a.i./ha).

The standing crop of grass on the treated plots increased by between 220 and 740 per cent. Changes in the total grass density and botanical composition can be ascribed to an increased density of Eragrostis lehmanniana.

At this stage of the trial, its selectivity in favour of the more desirable woody species, suggests that tebuthiuron shows great promise for controlling bush encroachment in the Northern Cape, although a final conclusion would only be possible 5 years after its application.     

The Ontario Veterinary College Hip Certification Program — Assessing inter- and intra-observer repeatability and comparison of findings to those of the Orthopedic Foundation for Animals

In Canada, the Ontario Veterinary College (OVC) has offered radiographic screening for hip dysplasia for many years, but there are other options for this service including the Orthopedic Foundation for Animals (OFA). There are some differences between the OFA and the OVC methods, and this study compares the OVC and OFA hip certification results in 37 dogs. There was good agreement between the two programs but in some instances there was a difference in the pass/fail status of a dog. Neither the OFA nor the OVC was more likely to fail or pass a given dog. The repeatability of the OVC results was assessed by both inter- and intra-observer comparisons in 100 dogs. There was at least 86% agreement among and within radiologists, but in 5 cases the disagreement resulted in a difference in the pass/fail status of the dog. These results illustrate the inherent variation in radiographic hip evaluation and highlight the importance of consensus grading practices to improve the accuracy of hip evaluation.