LIVESTOCK MONITOR

Press, 19 April 1985, Page 23

LIVESTOCK MONITOR

Moisture has severely limited early autumn pasture growth in the Darfield district, so it has only been through the use of supplements that sheep have been able- to increase in weight. Ewe lambs and twotooths in the Darfield monitor flock have averaged a Ikg per week increase in bodyweight over the last four weeks while ewes have also done well to reach 64kg, just short of mating target of 65kg. Rams were put out with the ewes and two-tooths 10 days ago when both flocks averaged 65kg. The fact that these sheep had good initial bodyweights, plus the effect of flushing using silage, means that a lamb drop of over 140 per cent can be expected. Last season the ewes were 66kg at mating, reaching a low of 63kg in the winter and rising back to above mating weight at lambing. The ratio of lambs tailed to ewes mated was 130 per cent. Farmers planning postmating feeding of breeding flocks should aim to avoid excessive weight loss of more than 10 per cent of bodyweight. On the other hand maintaining or increasing mating weights over the early winter is expensive and unnecessary. Feed is better carried over to late winter or early spring. A drop in weight of around 5 per cent is generally compatible with normal

feeding practices during the next three months. At weighing, the ewe hoggets in the monitor flock were 39 kg and they will be mated at the end of next week. Until then they will continue to receive preference for any quality pastures available. Ryegrass staggers continued to be a problem until two weeks ago at which stage there had been 20 deaths, mainly from misadventure. The following information on animal health and disease was prepared at the Lincoln Animal Health Laboratory. SHEEP © Rams are out on most properties by now. Where Brucella ovis has been recently diagnosed it may be worth while having rams reexamined by a veterinarian after they f are removed from the ewe flock, because this disease can spread rapidly from ram to ram during tupping. On properties where ewes are being vaccinated against Campylobacter abortion any ewes which had their first dose pretupping this year should receive a booster 6 to 8 weeks after the first. This usually coincides with ram removal. © Nitrate/nitrite poisoning is common at this time of the year. High nitrate levels may be found in Brassica crops, such as turnips and rape, and green oats. Usually toxic crops are at an immature stage and maybe poorly grown because of dry weather conditions. Nitrate levels can rise and fall quickly in the plant depending on its stage of growth and weather. When hungry hoggets are put onto a crop which has • a high nitrate level a number of sudden deaths may occur. When nitrate levels are lower or the crop is eaten more slowly some animals may be found depressed and reluctant to move. They may be breathing rapidly and the membranes around the mouth and eyes may be a “muddy” colour rather than bright pink. It is important to consult a veterinarian when disease or death occurs in sheep on crops because there are also a number of other diseases which may be involved. • Silage is an excellent method of fodder conservation and its use is increas-

ing. Poorly made silage that has had contact with air due to inadequate cover or poor compacting has a neutral pH- compared with the low pH of good silage. This normal pH allows the bacterium Listeria to grow. Listeria can cause disease in animals — it infects the brain of sheep and occassionally other farm animals causing “circling disease” and death. Listeria may also cause abortion in sheep and other animals. However, these infections are rare compared to the amount of silage fed. Suspected outbreaks of this disease, as of all such serious diseases, should be investigated by a veterinarian. Losses are usually less than 1 per cent. DAIRY CATTLE • With the current drought conditions, drying-off of the herd will be in many farmers’ minds. Now is the time to consider dry-cow therapy for mastitis prevention next season. If bulk milk somatic cell counts have been consistently over 500,000 there is a good case for treating every cow in the herd. Cows that have had to be treated for mastitis during the season should always be treated at drying off. It is important to treat all four quarters of any cows that are treated. Where individual somatic cell counts are available for each cow, these can be used in deciding which cows to treat. A veterinarian can help farmers to make best use of this information, and can advise on the best preparation to use. It is very important to use an antibiotic that is effective against the particular strains of bacteria that are causing mastitis in each herd. DOGS ® Antifreeze is a particular hazard to dogs at this time of the year. Ethylene glycol, the active ingredient of antifreeze, is a palatable substance which aogs delight in lapping from puddles left after the draining of car radiators. It is also an extremely potent poison resulting in kidney failure and death: All dog owners need to be aware of this hazard as each year the Lincoln Animal Health Laboratory receives a number of cases from both farming and urban areas.