The total replacement of protein supplements by synthetic lysine in rations based on sorghum grain for pigs over 45 kg liveweight.

Abstract

THE TOTAL REPLACEMENT OF PROTEIN SUPPLEMENTS BY SYNTHETIC LYSINE IN RATIONS BASED ON SORGHUM GRAIN FOR PIGS OVER 45 kg LIVEWEIGHT R. M. BEAMES*, L. J. DANIELS and J. O. SEWELL Summary In three experiments, various levels of lysine, yeast and soybean meal were used independently as supplements in diets based on sorghum grain plus minerals and vitamins. These diets were given to pigs during growth from 45-90 kg. Growth, feed efficien cy and carcass characteristics were im proved by supplementation with lysine. and to a si milar extent by soybean diets that provided equal or slightly lower calculated amounts of lysine. I. INTRODUCTION It is probable that the price of synthetic amino acids will continue to fall and that they will be used increasingly as replacements for conventional protein supplements. Three experiments were made to investigate various levels of lysine as a sole nitrogenous supplement to sorghum grain. Their main purpose was to test the findings of Jensen, Becker and Harmon ( 1965) who found that the growth of pigs over 45 kg liveweight on a ration of sorghum plus 0.25% lysine was as good as the growth on maize plus 8% soybean meal. II. MATERIALS AND METHODS (a) General In Experiment 1, twenty-four Large White male castrate pigs with a mean liveweight of 44 kg were divided into three groups of eight on the basis of liveweight. Within groups, eight diets (Table 1) were allocated at random. Pigs were housed in concrete pens and fed individually in stalls once daily with a maximum air-dry allowance of 2.10 kg. Feed was moistened (approximately one part water to two parts feed). Pigs were weighed weekly, and were sent for slaughter when their Iiveweight was 89.8 kg or more. They were fed immediately after the last weighing and slaughtered approximately 26 h later. In Experiment 2, three groups of six Large White pigs, initially of 45 kg liveweight were used; one group consisted of gilts and two of male castrates. Within groups, six diets (Table 1) were allocated at random. The pigs were kept in bare earthern yards, each provided with a shelter, and were given their rations dry, twice daily, in individual stalls. The air-dry allowance of feed was 1.85 *Animal Research Institute, Queensland Department of Primary Industries, Yeerongpilly. +Research Station, Queensland Department of Primary Industries, Biloela. *Research Station, Queensland Department of Primary Industries, Hermitage. 391 TABLE 1 Composition of diets in Experiments 1, 2 and 3 by weight on air-dry basis kg for a 45 kg pig rising by 0.03 kg/kg liveweight to a maximum of 2.27 kg. Pigs were withdrawn from trial at approximately 86 kg liveweight. They were fed just prior to final weighing and slaughtered 50 h later. In Experiment 3, five groups of five Berkshire pigs were used, three groups consisting of gilts and two of male castrates. Within groups, five diets (Table 1) 392 were allocated at random. Pigs were kept in concrete yards provided with shelters and were given rations moistened as in Experiment 1. Pigs were slaughtered 48 h after the ha1 weighing which was made 24 h after the last feed. Other experimental procedures were as for Experiment 2. (b) Cawass measurements Carcasses were held at a temperature of approximately +2'C for 24-82 h and then appraised by the Bostock (1964) system. Dressing percentage was calculated as 97% of the hot dressed weight including the head, divided by the final weight on experiment multiplied by 100. In Experiment 1, carcass density and chemical composition were measured. As the percentage of internal fat remaining after dressing varied between pigs, this fat and the kidneys were first removed. Carcasses were then split down the midline by handsaw. After removal of the limbs distal to the tarso-metatarsal and carpo-metacarpal joints and the head at the atlanto-occipital joint, the density of the right side was measured by submersion in water at 17�C. The side was then separated into bone, separable lean and separable fat (including skin). The separable lean and fat were analysed by the method for oven-dried sample cuts described by Morris and Moir ( 1963) and the data bulked to determine total amounts of ether extract, crude protein, water and ash. III. RESULTS Results of Experiment 1, and of Experiments 2 and 3 are presented in Tables 2 and 3 respectively. In all experiments, the mean daily feed intake of pigs receiving no nitrogenous supplement was lower than that of pigs on other treatments; refusals increased as time progressed and feed was frequently regurgitated. (a) Experiment 1 In Experiment 1 daily liveweight gain was significantly (P < 0.05) increased by all supplements except 0.1% L-lysine HCl.2HzO. Efficiency of feed conversion was improved (P < 0.05) by the addition of 0.1% L-lysine HC1.2Hz0, and further improved, although not significantly so, by the higher levels of lysine, and by yeast and soybean meal. There were significant (P < 0.05) treatment effects on density measurements Bostock appraisal and chemical analyses but not on carcass backfat thickness and s eye muscle index. (b) Experiment 2 Mean daily liveweight gain was significantly (P < 0.05) increased by supplementation with lysine, but only at the 0.36% level of L-lysine HC1.2H20 was the daily gain at a level similar to that achieved with the 11.9% soybean meal supplement. Increased gains were accompanied by improvements in feed efficiency. The mean eye muscle index was increased significantly (P < 0.05) by soybean supplementation but not by lysine. (c) Experiment 3 Mean daily liveweight gain of 391 g in the control group was increased significantly (P < 0.05) to 497 g with 0.24% L-lysine HC1.2HzO and to 516 g 393 TABLE 2 The effect of treatments in Experiment 1 on feed intake, liveweight change, feed eflciency and carcass composition TABLE 3 The effect of treatments in Experiments 2 and 3 on feed intake, liveweight change, feed efficiency and linear body measurements with 0.3 6% L-lysine HC1.2H20. Mean daily liveweight gain rose to 545 g with a 7.9% soybean meal supplement and significantly (P < 0.05) further to 590 g with the 11.9% level of soybean meal. Feed efficiency showed a response similar to that of bodyweight gains. IV.DISCUSSION In these experiments, increasing levels of lysine supplementation improved growth rate and feed efficiency, but in Experiment 3 the maximum growth and efficiency were significantly less (P < 0.05) than values obtained with the highest level (11.9 %) of soybean meal. Trends similar to these results were obtained in the other two -experiments. The possibility that an adequate lysine level had not been reached is supported by the results of Ericson, Larsson and Ostholm (1962) who found that pigs grew faster from weaning to bacon weight on a wheat-barley ration supplemented with 1 .O% L-lysine HCl than one supplemented with 0.34% L-lysine HCl. Thus the optimum dietary lysine level would appear to be greater than the estimated (N.A.S.N.R.C. 1964) 0.7 % in the latter ration. The lack of response to methionine in addition to 0.25% lysine with a sorghum ration reported by Jensen, Becker and Harmon (1965) would indicate that at this level of supplementation lysine was still the primary limiting amino acid, although threonine might have been a better choice to test as the second limiting amino acid (Pond, Hillier and Benton 1958). However, if lysine is the primary limiting amino acid to a level of 0.7% or more in the complete ration, the better growth produced by the 12% soybean meal ration in Experiment 3 than by the ration containing 0.36% L-lysine HCl.2H20 would be difficult to explain, as both these rations had approximately the same estimated lysine content of 0.50 to 0.57%. It appears that the change from the first limiting amino acid to the next may be a gradual one. No explanation can be offered for the trend towards poorer performance in Experiment 1 of the pigs receiving yeast compared with those receiving soybean meal, particularly in view of the similarity of the amino acid profile of these two products. (N.A.S.-N.R.C. 1964). V. ACKNOWLEDGMENTS The authors wish to express their appreciation to Miss Patricia M. Pepper for statistical analyses and to members of the Biochemical Branch for chemical analyses of ration components and carcasses. The technical assistance of Mr. M. H. Magee and Miss Ann Spiess was also appreciated. VI. REFERENCES F. ( 1964). Q6. agric. J. 90: 46. L. E., L ARSSON , S., and O STHOLM, C. 0. ( 1962). Acta Agric. stand. 12: 157. A. H., B ECKER , D. E., and HARMON, B. G. (1965). J. Anim. Sci. 24: 398. J. G., and M OIR, K. W. ( 1963). 'Technical Conference on Carcass Composition and Appraisal in Meat Animals'. C.S.I.R.O.: Melbourne. N.A.S. - N.R.C. (1964). 'Joint United States - Canadian Tables of Feed Composition'. National Academy of Sciences - National Research Council Publ. 1232. POND, W. G., HIT.T.IER, J. C., and BENTON. D. A. (1958). J. Nutr. 65: 493. BOSTDCK, ERICSON, J ENSEN , M ORRIS , 396