Results are reported from a 10-monlli trial, using 50 oxen, in which growth rates ofgroups receiving restricted and ncrmai night grazing were compared. The resiriction of night grazing was found to lead to a significant decline of 30°,, in hve-weight gain. This difference was largely attributed to periods of moderate grass shortage (i.e. marginal day grazing) when those animals with the longer grazing period were able to select a diet of superior quality and quantity. Under good, or very bad, grazing conditions the availability of night grazing did not appear to be critical.

An experiment is described in which the liveweight gains of cattle, grazing different pasture species, were measured when grazing sequences were arranged in the form of a Latin Square. The average coefficient of variation for the 6 "animal" Latin squares used was 28-5%, with a range of 15-1 to 42-6%. Significant improvements in liveweight gain were demonstrated arising from the inclusion of Stylosanthes gracilis in swards of Chloris gayana and Panicum maximum.The problems of conducting and interpreting trials of this type are discussed in relation to the need for data on the economic value of pasture species in the tropics. Latin square grazing designs offer a useful means of measuring animal production from pasture, with the advantage of requiring relatively small numbers of animals in each trial, but trials should be repeated at different sites.

An observational technique for measuring pasture palatability is described in which a palatability index is constructed to indicate the species selected by stock under specified conditions of choice. The index differentiates these species from others that stock are prepared to eat when opportunities for selection are more limited. The potential usefulness of this index in the initial testing of tropical pasture species is discussed.Results are reported from two 3-year experiments where the method was used. Coefficients of variationin individualgrazingsranged from 13-5 to22-2% with experimental meansof 19-2 and 18-3%. Hyparrhenia rufa and Cenchrus ciliaris were found to be the m6st consistently palatable of the grasses offered.

Two methods of measuring the liveweight gain of cattle on sown pastures are described in a 15 ac grazing trial. During the first 12 months of grazing, stocking rate was varied within and between pasture species. In the remaining 21 months, stocking rate was maintained at the same level between all pastures, but varied with the overall seasonal changes in grass availability. The relative merits of the two methods are discussed, and it is concluded that the trial using the same stocking rate on all species offered the more effective and practicable method of comparing pasture production differences of the order 30-50%.The results showed significant improvements in liveweight gain in the latter 21 months of the experiment, resulting from the inclusion of a legume, Centrosema pubescens in a Hyparrhenia rufa sward, and from the use of Hyparrhenia rufa rather than Panicum maximum in association with Centrosema pubescens. The ability of unfertilized ley pastures to produce over 300 lb/ac of liveweight gain in favourable years was clearly demonstrated.

The relationships of live animal ultrasonic measurements and carcass measurements to carcass composition were examined using data from two fattening trials. In one trial 42 pigs were fully dissected, and in the other 64 pigs were chemically analysed.Live animal ultrasonic measurements were significantly correlated (r ~ 0.58*** to 0.84"**) with carcass composition, and their use in the selection of breeding stock is recommended.Midline carcass measurements were poorer indicators of carcass composition than measurements taken over the eye muscle. On their own. measurements on the cut surface of the eye muscle were relatively inefficient indicators of lean meat content, but were useful when used with fat measurements in multiple regression equations . .Carcass length and depth measurements were poorly correlated with carcass composition.