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Publication Date

1981

Description

The low quality of standing pasture grasses in the dry seasons presents a major problem in the intensification of beef produc­tion in the tropics. The objective of this research was to examine the role of maize and grass silage or standing napiergrass (Pen­nisetum purpureum) as sources of forage when given alone or with supplements to beef cattle. In the first of three trials conducted at the National Agricultural Research Station, Kitale, Kenya, 36 Friesian castrates, initially 249 kg live weight (LW), were given silage of whole-crop maize either alone or supplemented with corn-and-cob meal. Each of these two basal diets was given ad libitum either without a nitrogen (N) supplement or with urea or cottonseed cake. In the second trial 17 Friesian steers, intially 158 kg L W, and 17 Hereford steers, initially 177 kg L W, grazed a napiergrass (P. pur

_pureum cv. French Cameroons) pasture throughout the dry season. The steers either received no supplement or were given con­centrate at either 5 or 10 g/kg LW/day. In the third trial 25 Friesian steers, initially 161 kg LW, were given silage of rhodesgrass ( Chloris gayana cv. Mbarara) ad libitum either alone or with concentrate at 0 % , 20 % , 40 % , 60 % , or 80 % of total dry-matter (DM) intake. In the final two trials the subsequent performance of steers during the wet sea;on was examined. In the first trial the level of performance of steers given maize silage alone was not significantly different from maintenance. Supplementation with both corn-and-cob meal and N significantly (P < 0.001) increased LW gain to a mean of 1.25 kg/day. In the second trial the LW gain of steers grazing napiergrass was 0 . .'35 kg/day, and this gain was increased to 0.70 kg/day (P < 0.001) when the animals were given concentrate at 10 g/kg LW. In the third trial steers given grass silage alone grew at only 0.10 kg/day. Supplementation of the silage increased LW gain up to a maximum of 1.40 kg/day when the concentrate was 80 % of total DM intake. Examination of subsequent performance at grass in trials 2 and .'3 showed that cattle given forage alone during the dry season grew significantly faster than those that had received concentrate. Further, the results of trial 3 showed that the marked differences in LW apparent at turnout were considerably narrowed by the end of the grazing season and also that there was no significant effect of previous dry-season treatment on LW at slaughter or carcass weight. These results show that supplementation of forage with energy and/or N is required for high levels of LW gain during the dry season. However, in pasture-based systems in the tropics the need fo,: such high levels of performance is questionable when com­pensatory growth can be exploited in a subsequent grazing season.

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Effect of Supplements on the Live-Weight Gain of Beef Cattle Given Forage During the Dry Season

The low quality of standing pasture grasses in the dry seasons presents a major problem in the intensification of beef produc­tion in the tropics. The objective of this research was to examine the role of maize and grass silage or standing napiergrass (Pen­nisetum purpureum) as sources of forage when given alone or with supplements to beef cattle. In the first of three trials conducted at the National Agricultural Research Station, Kitale, Kenya, 36 Friesian castrates, initially 249 kg live weight (LW), were given silage of whole-crop maize either alone or supplemented with corn-and-cob meal. Each of these two basal diets was given ad libitum either without a nitrogen (N) supplement or with urea or cottonseed cake. In the second trial 17 Friesian steers, intially 158 kg L W, and 17 Hereford steers, initially 177 kg L W, grazed a napiergrass (P. pur

_pureum cv. French Cameroons) pasture throughout the dry season. The steers either received no supplement or were given con­centrate at either 5 or 10 g/kg LW/day. In the third trial 25 Friesian steers, initially 161 kg LW, were given silage of rhodesgrass ( Chloris gayana cv. Mbarara) ad libitum either alone or with concentrate at 0 % , 20 % , 40 % , 60 % , or 80 % of total dry-matter (DM) intake. In the final two trials the subsequent performance of steers during the wet sea;on was examined. In the first trial the level of performance of steers given maize silage alone was not significantly different from maintenance. Supplementation with both corn-and-cob meal and N significantly (P < 0.001) increased LW gain to a mean of 1.25 kg/day. In the second trial the LW gain of steers grazing napiergrass was 0 . .'35 kg/day, and this gain was increased to 0.70 kg/day (P < 0.001) when the animals were given concentrate at 10 g/kg LW. In the third trial steers given grass silage alone grew at only 0.10 kg/day. Supplementation of the silage increased LW gain up to a maximum of 1.40 kg/day when the concentrate was 80 % of total DM intake. Examination of subsequent performance at grass in trials 2 and .'3 showed that cattle given forage alone during the dry season grew significantly faster than those that had received concentrate. Further, the results of trial 3 showed that the marked differences in LW apparent at turnout were considerably narrowed by the end of the grazing season and also that there was no significant effect of previous dry-season treatment on LW at slaughter or carcass weight. These results show that supplementation of forage with energy and/or N is required for high levels of LW gain during the dry season. However, in pasture-based systems in the tropics the need fo,: such high levels of performance is questionable when com­pensatory growth can be exploited in a subsequent grazing season.