Effects of supplementation of molassed natural pasture hay with urea, and of water intake restriction on feed intakes by zebu cattle in the semi-arid zone of Mali

Abstract

Dry-season cattle feeding in the semi-arid zone of Mali is based on natural pasture hay or millet or sorghum crop residues. Some use is made of cowpea haulms, but supplies of these are limited. Diets are generally deficient in nitrogen, of low digestibility and consequently intake is restricted, contributing to observed dry-season weight losses in mature cattle of up to 20% of liveweight (Wilson et al., 1983). There is concern that the problem of restricted feed intake may be aggravated by limited availability of drinking water during the dry season (BECIS, 198 I).The effects on intake of water availability and urea addition to rations based on molassed natural pasture hay and dry cowpea haulm were measured using 6 mature castrated male zebu cattle of 343 kg mean liveweight, in an experiment carried out during the dry season (November to May) in the semi-arid zone of central Mali. The trial was executed and analysed in latin square format, in which each animal was subject to each of 6 treatments, successively over 6 feeding periods, each of 10 days' duration, throughout which the animals were tied in stalls under shade and fed and watered individually. Natural pasture hay comprising predominantly Pennisetum pedicellatum was fed ad libitum in mixture with 40% molasses, with and without addition of urea at 10g.kg -l of the mixture. Cowpea haulm was fed as a supplement to both diets at 1 kg.d -1. Feeding treatments were combined factorially with levels of water allowance of 100%, 80% and 60% of an ad libitum intake estimated for each animal over the first 4 days of each feeding period. The average daily intake of air-dried feed was estimated from measurements on each of the final 6 days of each feeding period. Average daily temperature at the time of the trial was 30"7°C and daily o~en-water evaporation, under shade adjacent to the animals, averaged 8"7 mm d-.Mean adlibitum water intake was 27-7 kg.d -1 . Restriction of water intake resulted in no significant (P > 0.05) reduction in total feed intake, but a restriction of water of 60% ad libitum did significantly (P < 0-05) reduce hay intake. Addition of urea to the molasses-hay mixture significantly (P < 0-001) increased hay and total DM intake by 33 % and 26% respectively (Table I). Urea feeding was also associated with a 16% increase in water intake t but water intake per unit feed intake was reduced from a mean 4.29 kg water.kg-feed without urea to 3"93 kg water.kg -l feed with urea.Ad libitum water intake levels were comparable with other estimates for nonlactating zebu cattle (Wilson, 1961;Ahmed, 1972), although they should probably 3 Present address;