This study uses heteroskedastic Tobit and Censored Least Absolute Deviations models to

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Link to this article: http://journals.cambridge.org/abstract_S0003356100021024How to cite this article: R. W. Muinga, W. Thorpe and J. H. Topps (1992). Voluntary food intake, live-weight change and lactation performance of crossbred dairy cows given ad libitum Pennisetum purpureum (napier grass var. Bana) supplemented with leucaena forage in the lowland semi-humid tropics. AbstractScarce and poor-quality food resources limit smallholder dairy production in the tropics. Food resources for zerograzing may be improved by intercropping Pennisetum purpureum (napier grass) with Leucaena leucocephala leguminous hedgerows. To evaluate dairy cow performance from this alley cropping system, 36 Ayrshire /Brown Swiss X Sahiwal cows in a 2X3 factorial design were individually fed from the 3rd week of lactation for 14 weeks on diets of napier fodder harvested at 1-0 m or 1-5 m and offered ad libitum, supplemented with 0, 4 or 8 kg fresh weight leucaena fodder. Average daily milk yield during the 2nd week of lactation was a covariate in the analyses of milk yield, and post-partum live weight a covariate in the analyses of dry matter (DM) intake and live-weight change. Napier harvesting height and leucaena level had independent effects on performance. Napier height (1-0 m or 1-5 m) significantly (P < 0-01) affected daily napier DM intake (9-3 and 6-8 kg), total daily DM intake (10-5 and 7-9 kg), daily live-weight losses (165 and 490 g) and daily milk yield (8-6 and 6-9 kg respectively). Leucaena supplementation (0, 4 or 8 kg) significantly (P<0-01) increased total daily DM intake (7-8, 9-3 and 10-4 kg), reduced daily live-weight loss (560,235 and 175 g), and increased daily milk yield (7-3, 7-7 and 8-3 kg respectively). The results show that reasonable dairy performance can be achieved in the tropics by supplementing a napier fodder basal diet with leucaena forage, and highlight the importance of the stage of harvesting of the napier fodder. The results are discussed in relation to the nutrient requirements for milk production given by the Agricultural Research Council (1980 and 1984).

An experiment was carried out to evaluate dairy performance and rumen fermentation from a forage-based diet supplemented with Lucaena leococephala (leucaena) and maize bran. Bos indicus (Ayrshire/Brown Swiss) х Bos taurus (Sahiwal) cattle were offered Pennisetum purpureum (napier grass) ad libitum either unsupplemented (N) or supplemented on a dry-matter (DM) basis with 1 kg (LL) or 2 kg leucaena (LH) or 2 kg leucaena together with 1 kg DM maize bran (LHM). Food intake, milk yield, diet apparent digestibility and nitrogen balance were measured using eight cows (mean live weight 384 (s.d. 41) kg in two 4х4 Latin squares. Rumen fermentation was measured using four rumen fistulated steers (mean live weight 352 (s.d. 12) kg in a 4 х 4 Latin square. Performance was recorded during the last 7 days of each 21-day experimental period. Supplementation increased food intake (6·3, 7·6, 7·9 and 8·7 kg DM per day; P < 0·01; s.e.d. 0·24) and milk yield (5·1, 5·4, 5·5 and 6·5 kg/day; P < 0·01; s.e.d. 0·28) for N, LL, LH and LHM respectively. Supplemented diets tended to be more digestible compared with napier grass as the sole food (organic matter apparent digestibility coefficients 0·54, 0·55, 0·57 and 0·57; s.e.d. 0·020; N, LL, LH and LHM, respectively) and N balance increased progressively with supplementation.Supplementation progressively increased rumen ammonia-nitrogen concentrations in steers and the rate of rumen degradation of napier grass increased when leucaena (diets LL and LH) was offered. The results suggest that supplementation of napier grass with leucaena increased DM intake owing to increased ammonia concentrations and rates of napier degradation in the rumen. Supplementation of the forage diet with 1 kg DM maize bran did not significantly reduce the rumen degradation of napier grass and increased the molar proportions of propionate which may have increased the efficiency of utilization of metabolizable energy and therefore milk production.