Out-of-season breeding of milk goats--the effect of light treatment, melatonin and breed.

The purpose of this study was to evaluate the effectivity of melatonin in addition to light treatment (exposure to 2 hours of light during the night = a long-day photoperiod) to modify the breeding season of Saanen and cross-bred milk goats and to compare the difference between the breeds. Twenty-two Saanen and 22 cross-bred does were randomly divided into 3 treatment groups. Group 1 (controls) received no treatment, Group 2 received light treatment for 37 days and Group 3 received light treatment plus melatonin implants after the light treatment. After a further 35 days the 3 groups were brought together and a billy goat that had also been exposed to the extra light at night, had received a melatonin implant and had been isolated from the does during the treatment period, was introduced to the does for natural mating. Ultrasound scanning was used to diagnose pregnancy and all the pregnant goats kidded. Significantly more Saanen does compared to cross-bred does (P = 0.018) became pregnant and kidded after natural mating, when the group that received melatonin as well as light treatment was compared to the group that received light treatment only. Compared to light treatment only, the addition of melatonin to light treatment improved (P = 0.0028) conception after natural mating, in both the Saanen and the cross-bred does.

The possible role of two common three-host ticks, Rhipicephalus appendiculatus and Amblyomma hebraeum, in the transmission of bovine leukosis virus.

The possible role of Rhipicephalus appendiculatus and Amblyomma hebraeum in the mechanical and transstadial transmission of bovine leukosis virus (BLV) was investigated. BLV-free laboratory strains of R. appendiculatus and A. hebraeum nymphal ticks (n = 400) were fed on a BLV-infected and a negative control bovine. At various intervals after engorgement the ticks were homogenised and injected subcutaneously into BLV-negative sheep. Adult R. appendiculatus and A. hebraeum, which had fed as nymphs on the BLV-infected bovine, were then allowed to feed on BLV-negative sheep. A control sheep was also injected intravenously with blood from the infected bovine. Only the control sheep that received blood from the BLV-positive bovine seroconverted 9 months later. All the other surviving sheep remained serologically negative during the 13 months observation period. It is suggested that the nymphal stages of these ticks probably do not play a role in the transstadial transmission of BLV in southern Africa. The significance of these results is discussed.

Aortic thromboembolism associated with traumatic reticuloperitonitis in a downer cow.

A large thrombus was found at the ileal bifurcation on post mortem examination of a 6-year-old Jersey cow which presented clinically with a history of acute onset recumbency, hind limb paresis and skin necrosis over the sacral area. Other significant findings on post mortem were traumatic reticuloperitonitis accompanied by mural thrombosis of the left ventricle associated with a purulent sinus tract through the ventricular wall, fibrous adhesions between the pericardium, diaphragm and liver, and multiple infarcts in both kidneys.