LIVESTOCK MONITOR

Press, 23 September 1983, Page 25

LIVESTOCK MONITOR

Reasonable conditions for pasture growth over the past month have maintained sheep liveweight gains on the Canterbury Plains, according to the Ministry of Agriculture and Fisheries. The mixed-age ewes in the monitor flock have averaged a weight gain of up to 2kg a week during this time.

At the start of lambing earlier in the month the average weight of the flock was 54kg. In the three weeks since, the 30 per cent of ewes yet to lamb have added skg to this. However they have had unlimited access to increasing pasture because the lambed ewes have been shedded off. Ewes which have lambed dropped 9kg, the expected weight loss after lambing. The hoggets now weigh 38kg — a rise of 3kg over the month. Most of this weight gain occurred during the last one and a half weeks while feeding on surplus turnips. Animal health Information is supplied by the Lincoln Animal Health Laboratory. • Lamb death survey: The survey of lamb deaths on 22 farms in the OxfordRangiora area continues in its fifth and final year. It is being carried out with the assistance of the Slink Lamb plant at Belfast. Losses on these farms before the storm were low, but deaths rose rapidly during the storm with over 80 per cent dying of exposure and/or starvation. Farmers and others interested are invited to visit the lamb death survey shed at Belfast and view the autopsy work being carried out by livestock officers from the M.A.F. The lambs are collected and skinned by Slink Lambs (Canterbury), Ltd, and passed on to the livestock officers. The shed is behind the Slink Lamb factory, between the two freezing works at Belfast. The work is done between 9 a.m. and 11 a.m. each morning while the factory is in operation. • Magnesium: Cases of hypomagnesaemia in both sheep and cattle continue to trickle in. While the serum magnesium levels of some cattle are quite low (O.5mM/l) and have caused clinical disease, many are in the marginal range (0.6-0.7).

Work at Ruakura has shown that a milk production response can oe expected to Mg supplementation in the first 3 months of lactation, where mean herd Mg levels are less than 0.62mM/l. Farmers should get their herd magnesium levels checked by a vet a fortnight after calving and again six weeks later if they have any doubts about the status of their herd. Little work has been done on the effect of magnesium status of ewes on lamb growth to weaning but a similar sjtua-

tion with milk production is possible. We hope to look into this soon. © Bacterial scours in sheep: The lab has seen a number of cases of bacterial scours in sheep this year, although the main outbreak occurred earlier in the winter. Typically a few deaths were reported but most animals recovered quickly. Two types of bacteria have been isolated - Campylobacter jejuni and Yersinia pseudotuberculosis. The Campylobacter is a different species to that which causes abortion. It has been isolated from one-third of scouring cases but a brief survey of all sheep specimens coming into the lab showed that at least onethird of normal, non-scour-ing sheep carry this organism in their gut. Yersinia commonly causes scouring and deaths in deer each winter. Cases of it appearing in sheep have been reported for the first time this year. This organism was isolated from two-thirds of the scours cases brought to the lab. The common factor in the outbreaks seems to be stress. Both of these organisms are probably present in the gut of normal sheep and only cause disease when the animal’s immune system is stressed by other problems such as parasitism, bad weather or poor feed. Avoiding this sort of stress where possible is probably the best way to prevent this disease. © Mineral mix problems: We have had a number of cases of sheep deaths occurring a few weeks after the use of mineral mixes. Liver analyses of the affected animals eliminated the possibility of toxic doses. The problem is one of high acidity causing severe damage to the sheep’s throat following drenching. The ulcers become infected and the infection spreads throughout the animal resulting in its death. The drench is supplied in a powder form to the farmer to be mixed and administered. Farmers should make sure they actually need a mineral supplement before using one. There are many brands available and we suggest you contact your vet for advice on the best one for your needs.

• Brucellosis in rams: This disease causes infertility in rams and is often first suspected when an excessive number of barren ewes are noticed.

Unless you buy your rams from an accredited brucella free flock, now is the time to have your vet check your rams. A brief physical examination and a lab blood test is a good investment against brucellosis. It is wise to complete the tests and decide on the number of replacement rams needed before the ram sales begin.

If the tests are left too late in the year you may have a limited choice of replacements. Although vaccine is available, testing and culling of affected rams is preferable in most circumstances.