The effect on lamb production of adding protein and mineral supplements to whole cereal grains compared to incorporation of the supplements in hammer milled mixtures or pellets.

Abstract

Animal Production in Australia THE EFFECT ON LAMB PRODUCTION OF ADDING PROTEIN AND MINERAL SUPPLEMENTS TO WHOLE CEREAL GRAINS COMPARED TO INCORPORATION OF THE SUPPLEMENTS IN HAMMERMILLED MIXTURES OR PELLETS R.W. HODGE*, B. BOGDANOVIC* and A. MAKIN* SUMMARY Adding protein (lupin or meatmeal) and mineral supplements to whole barley or whole wheat grains was as effective in promoting intake and liveweight gain of lambs as was incorporation of the supplements in hammermilled mixtures. However, hammermilling an oat ration containing a high proportion of lupins (40%) depressed (P < 0.05) the liveweight gain of young lambs compared to those fed a pelletted mixture and hammermilling an oat ration containing meatmeal (7%) increased the liveweight gain of lambs compared to those offered whole oats supplemented with meatmeal. INTRODUCTION Feeding of cereal grains to young lambs in Australia can occur during drought, in 'opportunity' feedlots and strategic feeding of high quality rations may have a place in spring lambing systems where it is important for ewe lambs to attain a minimum liveweight before grazing dry, summer pastures (McLaughlin 1966). In these situations food conversion efficiency (kgs of feed/kg of liveweight gain) is critical to the success of the operation and it is well known that supplements of protein and minerals must be added to cereal grains given to young lambs if optimum feed conversion efficiencies are to be obtained. To ensure that the lambs obtain these essential supplements it may be necessary to pellet the entire ration but this would substantially increase costs. The question arises as to the relative merits of incorporating the supplements in pellets, in hammermilled mixtures or simply mixing with the whole cereal grains. MATERIALS AND METHODS Two experiments were carried out with two (Poll Dorset o*X (Border Leicester X Merino)?). of barley or oats supplemented with lupin grain wheat or oats supplemented with lupin grain and in experiment 2. month old ewe and wether lambs The animals were offered rations and minerals in experiment 1 and minerals or meatmeal and minerals The lambs were all born and raised within a feedlot until six weeks of age. The ewes were offered rations based on whole oats and the lambs had access to these rations. When the lambs were six to eight weeks of age the ewes were removed from the feedlot and the lambs allotted by stratified randomization on the basis of live weight and sex to their respective groups and, in the case of experiment 2, to one of four replications within each group. A total of 72 lambs (36 @and 36 y) wereavailable for experiment 1 and 120 lambs (64 drand 56 9) for experiment 2. The lambs were offered their respective diets for a period of 75 days in experiment 1 and 60 days in experiment 2. Diets The animals in experiment 1 were given oats + lupins or barley + lupins either as whole grains, as hammermilled and gristed mixtures or as a pellet. The lupin grain was gristed and the oats and barley hammermilled through a 6.35 mm * Animal Research Institute, Department of Agriculture, Werribee, Vic. 3030. 495 Animal Production in Australia screen and all mixed in 900 kg lots. The barley mix was used to prepare the pelletted diet (4.76 mm die) but the oats were hammermilled through a 3.2 mm screen before pelletting in order to mill the husk more thoroughly. The barley was supplemented with 35% lupins and the oats with 40% lupins to provide rations calculated to contain 17% protein. Each ration was also supplemented with 1.4% limestone, 0.5% salt and 0.1% trace element and vitamin pre-mix. The minerals were included in the pelletted and hammermilled rations but were added each day to the whole grain ration. In experiment 2 the lambs were given wheat or oats supplemented with ei ther lupins (14%) or meatmeal (7%) and offered the rations as either whole grains or hammermilled and gristed mixtures. The oats were sprayed with 2% urea so tha.t each of the oat and wheat ration was calculated to contain 17% crude protein. The wheat/lupin or oat/lupin rations were supplemented with 2.0% of the same mineral mix used in experiment 1 and the meatmeal supplemented ration with 0. of the mineral mix. The rations in both experiments were offered daily and were supplemented with 10% lucerne chaff which was offered in separate troughs. The rations were adjusted daily so that the residues remained below 5% of the feed offered. Measurements The live weight and group intake of the animals were recorded at weekly intervals. The digestibility of the diets in experiment 1 and the whole grain diets of experiment 2 was determined with 4 lambs/diet offered 720 g dm of concentrate and 90 g dm of lucerne chaff/day. The live weight, digestibility and intake (experiment 2) data was examined by analysis of variance. RESULTS Although feed residues were kept low some evidence of selection by the lambs was observed. Thus the feed residues of the lambs fed whole oats + lupins (experiment 2) contained no lupins and the residues of the hammermilled oat ration in experiment 2 contained a high percentage of oat husks which had not been broken up by processing. One of the four replications of lambs fed whole oats and two of the replications fed whole wheat rejected a proportion of the meatmeal supplement (experiment 2). It was clear too that the mineral supplement was not always completely consumed when fed with the whole grain rations. The liveweight gain of the lambs offered the hammermilled oat/lupin ration in experiment 1 was significantly less (P < 0.05) than those given the pelletted oat/lupin ration and those given the barley diets (Table 1). In experiment 2 the liveweight gain of the lambs given the oat diet was less (P < 0.05) than those given the wheat rations and although the mean liveweight gain of the lambs given the hammermilled oat ration was higher than those offered the whole oat diets the difference was not significant. Pelletting significantly (P < 0.05) depressed apparent dry matter digestibility in experiment 1 and the digestibility of the wheat diets in experiment 2 were significantly higher (P < 0.05) than the oat based rations. Animal Production in Australia TABLE 1 Mean intake (kg dm/d) and liveweight gain (g/d) of the lambs DISCUSSION The problem of providing protein and mineral supplements to whole grain diets without excessive selection or rejection of individual components has been studied by plrskov, Fraser and McHattie (1974). These workers found that adding the protein and mineral supplement as a pellet approximately the size of cereal grains and ensuring that there was no excessive accumulation of feed residues provided the same animal response as a complete pelletted ration. In the present work care was also taken to avoid build up of feed residues and the results show that simple whole grain mixtures of barley supplemented with lupins and minerals were just as effective as hammermilling or pelletting the diets in maintaining intake and growth rate of young lambs. The results also show clearly that there is no advantage to be gained by hammermilling wheat/lupin or wheat/meatmeal diets compared to whole grain mixtures of these rations. No information is presented on the effects of pelletting these rations but the significantly lower liveweight gain of the lambs given whole wheat + meatmeal compared to whole wheat + lupins (Table 1) suggests that pelletting a diet containing meatmeal would reduce selection and improve animal performance. When oats were supplemented with a high proportion (40%) of lupin grain, hammermilling the mixture reduced and pelletting tended to increase liveweight gain of the lambs (Table 1 - experiment 1). This result was probably associated with physical aspects of the ration in that the hammermilled ration may have been more difficult to eat because of dust and caking of the mixture on the mouth of the lamb (Romberg et al. 1970). On the other hand, hammermilling an oat diet containing a low proportion of lupins (14%) or meatmeal (7%) tended to 497 Animal Production in Australia increase intake and liveweight gain. We consider that this effect was associated with the ability of the lambs to reject oat husks in the hammermilled diets and thus select a more digestible diet. We conclude that processing of wheat or barley supplemented with minerals and high protein legume grains is not necessary in order to maintain high liveweight gains in young lambs but pelletting of cereal grains supplemented with meatmeal may be required to obtain maximum animal performance. Processing of rations containing a high percentage of oats is also likely to improve lamb growth rates but the benefits obtained are marginal and unlikely to repay the costs of processing. ACKNOWLEDGEMENTS This work was supported in part by funds provided by the Australian Wool Corporation. We thank Mr. R. Jardine, Biometrici .an, for the statistical analyses. REFERENCES MCLAUGHLIN, J.W. (1966). Proc. Aust. Soc. Anim. Prod. 6: 246. &KSOV, E.R., FRASER, C. and McHATTIE, I. (1974). Anim.=Prod. 18: 85. ROMBERG, B., PEARCE, G.R. and TRIBE, P.E. (1970). Aust. J. Exp.= Agric. Anim. Hush-. 10: 145. - 498