The sweat rates, skin and rectal temperatures and other components of the heat budgets of cattle were measured in Kenya and in England. Mean sweat rate (E c ) was more closely related to mean skin temperature (T t ) than to rectal temperature. The results were described by an exponential relationship between T, (°C) and E c (mg/m 2 . sec) of the form E e = E o exp (T, -T o )/B, where T o and B are parameters (both with units of °C) which describe the sweating response of the animal, and E o is 1 mg/m 2 .sec. JT 0 was 30-8 °C for a single Bos taurus in England and 33-8 °C for five animals in Kenya suggesting that chronic acclimatization to a hot environment resulted in the cattle being able to tolerate a higher mean skin temperature. The effect of species (Bos indicus cf. B. taurus) was small compared with the effect of acclimatization, although the mean value of B was significantly higher for B. indicus (1-58 cf. 0-94 °C) indicating that the physiological mechanism controlling sweat rate in B. indicus was less sensitive to skin temperature. INTRODUCTIONFor cattle in hot climates, chronic heat stress is ubiquitous, and if its causes and effects were better understood, productivity could be increased. The heat which an animal generates by metabolism is equal to the net rate of heat loss plus the rate of change in heat stored. Ignoring terms which are usually small, the heat budget of an animal can be written as M + R = C + XE + J.(1)

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A survey of 101 farmers with sows was conducted in the Koshi Hills of Nepal. Estimates of those reproductive traits which did not differ significantly between local and Pakhribas crossbred sows, are farrowing interval 7.4 months, litter size at birth 8.3, age of piglets at weaning 2.2 months and total number of farrowings 13.2. Local pigs reach sexual maturity sooner than Pakhribas crossbreds; age at first farrowing for the two genotypes is 10.7 and 12.0 months (P < 0.05), and age at first mating of boars is 6.5 and 7.4 months (P < 0.05). Sows farrow throughout the year and there is no clearly defined best season for farrowing. Pre-weaning mortality rates are estimated to be 22% for local piglets and 15% for Pakhribas crossbreds. Almost all farmers practise controlled mating in which either the sow is taken to the boar or the boar is brought to the sow. The proportion of farmers (with sows) who own a boar is only about 5 per cent.

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