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Three breeds of Javanese sheep are described briefly and data suggesting the segregation of a gene with large effect on ovulation rate and litter size are presented. The three breeds are Javanese Thin Tail (JTT), Javanese Fat Tail (JFT) and Semarang (SEM), the last possibly a substrain of JTT. All three breeds have mean mature ewe weights under 30 kg. Ovulation rate and litter size did not differ significantly among the three; all had litter sizes of up to 4 or 5 with a mean for mature ewes of approximately 2. Ovulation rate ranged from 1 to 5 and had an average within-breed repeatability of .8 within season and .65 between seasons. Within-breed repeatability of litter size was .35 +/- .06. Prenatal survival in pregnant ewes with two, three and four or more ovulations averaged 93, 88 and 86% over two seasons. Dams that had at least one ovulation rate or litter size record greater than or equal to 3 produced two groups of daughters in approximately equal numbers: one group with many records greater than or equal to 3 and mean ovulation rate and litter size of 2.73 and 2.31, respectively, and one group with ovulation rates and litter sizes of 1 or 2 and corresponding means of 1.39 and 1.38. Dams with ovulation rate or litter size records of only 1 or 2 produced daughters in which over 90% had records of only 1 or 2. Estimated heritabilities for the mean of approximately three ovulation rate or litter size records from these daughter-dam comparisons exceeded .7. These results suggest segregation of a Booroola-type gene, one copy of which increases ovulation rate by about 1.3 and litter size by .9 to 1.0. Relationships between duration of estrus and ovulation rate, and between timing of release of luteinizing hormone and number of eggs shed, resemble the pattern in Booroola Merino more closely than that in Finnish Landrace or Romanov, supporting the hypothesis of a major gene.

The extent to which ewe reproduction could be improved by supplementary feeding around lambing time was investigated with four groups each of 16 ewes which were run continuously with fertile rams until they had lambed three times. One group was fed at a maintenance level throughout and the other three groups were given supplementary feed during the last four week of each pregnancy only, or during the last four weeks of pregnancy plus the first six weeks after each lambing, or during the last four weeks of pregnancy plus the first 12 weeks after each lambing. The average body weight of lambs weaned at 13 weeks of age increased (P less than 0.001) progressively from 6.0 to 9.1 kg with increasing duration of supplementary feeding. There were however no significant differences between treatment groups in mean interval between successive lambings (202 days), ovulation rate (2.26), litter size (1.58), lamb birth weight (1.8 kg), preweaning lamb mortality (37%) or number of lambs weaned per lambing (0.99).

Lamb production in relation to total feed consumption was recorded in Javanese thin tail (JTT) ewes and in first cross Suffolk x JTT (SX), Wiltshire Horn x JTT (WX) and Poll Dorset x JTT (DX) ewes over three successive lambings or for 21/2 years after joining with rams of the same genotypes in a continuous mating system. For the JTT, SX, WX and DX genotypes respectively, total numbers of lambs weaned per ewe joined were 3.77, 2.50, 2.08 and 1.33, mean lamb body weights at weaning were 12.8, 18.8, 18.6 and 20.9 kg, total weights of lamb weaned per ewe joined were 48.4, 46.9, 38.8 and 27.9 kg, and average weights of feed consumed by the whole production system per kg of lamb weaned were 16.4, 21.9, 23.5 and 32.8 kg. Thus cross-bred ewes required more feed to produce fewer though heavier lambs without any real increase in total productivity.

Recent developments in exogenous hormone therapy to control and facilitate breeding in domestic buffalo cows (B. bubalis) are reviewed. Oestrus in domestic animals was synchronized satisfactorily during the normal breeding season by both of the standard treatments with prostaglandins or progestagens initially developed for use in Bos taurus cattle. Anoestrous cyclic cows treated with prostaglandin showed synchronized oestrus and conception rates similar to those recorded in normal cyclic animals, though the responses may have depended to some extent on increased intensity of observation of oestrus. Seasonally acyclic animals treated with progestagens and pregnant mare serum gonadotrophin also showed synchronized oestrus and conception rates equivalent to those recorded in cyclic animals, but these observations did not include prepubertal heifers or cows in the early stages of post-partum anoestrus. Controlled breeding did not overcome a general problem of low conception rates at spontaneous oestrus. Further investigations of controlled breeding should incorporate other management strategies, such as better feeding and reduced heat stress, which are known also to improve buffalo reproduction.