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Sterility Survey. —A much reduced number of cows from the main A.I. groups with known breeding histories were available for post-mortem examination at the end of last dairying season. This was partly because a fair proportion of empty cows were highproducing daughters of merit sires and thus worth holding, and partly due to the success, of penicillin treatment for mastitis, resulting in fewer cows being culled for the combined reasons of infertility and mastitis. The data from those available this year did not materially alter the picture presented by the 177 cull cows described in the 1948-49' annual report. In these 70 per cent, had normal general organs and a further 10 percent. showed only endometritis. In consequence, it was suggested that a high proportion of such mated cows are probably fertile at the time of slaughter and could conceive if given the opportunity. Accordingly, the cows culled for infertility this season were artifically inseminated in March and April, six to eight weeks before slaughter. A single high dose rate of sperm was used to eliminate the male side as a limiting factor. Of 41 " sterile " cows inseminated,- 23, or 56 per cent., conceived to this single insemination. It seems quite-clear that a high proportion of "empty" cows normally culled each year are likely to be quite fertile at the time of culling. Whatever trouble has existed to prevent conception during the usual spring breeding-season has passed off and left the cow's breeding potential quite normal. This observation is supported by the results of the experiment conducted by the Herd Recording Department, in which a high proportion of cows similarly culled for sterility were held over until the following year to be successfully mated in the spring. The inescapable conclusion is that a large percentage of the temporary sterility in New Zealand dairy cattle is of economic importance mainly because of the seasonal mating system in the industry. The problem would create less interest among farmers if calving were spread more evenly throughout the year, but this is impracticable under grassland dairying conditions. Feeding Trials With Cupressus Macrocarpa.—lt has frequently been reported that, ingestion of C. macrocarpa by cows near calving produces abortion. Feeding tests were conducted this year with 8 pregnant cows which ate from 7 to 10 lb. each of macrocarpa foliage daily for five weeks. Only 2 cows aborted, and one of these was infected with Brucellosis abortus. The experiment is to be repeated using cows which are brucella-free. Johne's Disease in Cattle. —Observations have been continued on the field vaccination experiment which was initiated in selected infected herds in the Taranaki and Waikatodistricts in 1948. The fresh crop of calves born on the 7 farms in 1949 were vaccinated and intradermal sensitivity tests with avian and mammalian tuberculins were conducted regularly on the previous season's calves. Laboratory diagnostic procedures were the subject of study during the year. The evaluation of the efficiency of techniques for the isolation of Mycobacterium, paratuberculosisr from infected faeces, intestinal mucosa, and lymph nodes was of particular interest. Ketosis and Grass-staggers in Milking Cows. —Further experiments have been carried out to study the influence of negative energy balance on the incidence of metabolic diseases. Starting from the first week of lactation, 8 cows were underfed to the extent of about half their requirements, and 5 of these were dosed thyroprotein in addition. Two cows developed moderately severe symptoms of grass-staggers after six days'" underfeeding, for the final 3 days of which they received thyroprotein. They developed marked hypomagnessemia (0-1 to 0-3 mg. per cent.), slight ketosis, and, on the day clinical symptoms developed, hypocalcsemia also (5 to 6 mg. per cent.). Both cows had a second attack of staggers with a similar blood picture 2 days later, and both responded rapidly to glucose and calcium gluconate injection at the first attack and to calcium gluconate and magnesium sulphate injection at the second attack. Two other cows showed mild symptoms of grass-staggers not necessitating treatments Both had been underfed and dosed thyroprotein, one for 7 days and the other for 12 days.. Both showed hypomagnessemia and slight ketosis.

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