Variation in measurement of nitrogen balance and feed digestibility with pigs.

Abstract

Nitrogen was determined in duplicate (urine and faeces) and triplicate (diets) with fresh samples of 1 ml, 0.6 g and 2 g respectively. Digestion, with selenium as catalyst, was continued for 30 min after clearing. Standard analyses of variance were made on data from each collection period, and the three collection periods combined. III. RESULTS All pigs appeared healthy throughout both trials. Nitrogen retention and dry matter digestibility in Experiments 1 and 2 and results from Jones and Cadenhead (1965) and Cole, Duckworth and Holmes (1967) are presented in Table 1. Percentage dietary nitrogen retention (N), percentage dry matter digestibility (DM), and litres of urine output (U) for Experiments 1 and 2, and data presented by Jones and Cadenhead (1965) and Cole, Duckworth and Holmes (1967) TABLE 1 ,447 estimation of small treatment effects. The selection of pigs on a litter-mate basis and not on adaptability to cages may have placed some animals under a greater stress than others, so affecting nitrogen metabolism and resulting in variation between animals. Incomplete separation of urine and faecal nitrogen in Experiments 1 and 2 made it invalid to calculate apparent nitrogen digestibility and nitrogen retention. Such knowledge would be essential if a fuller understanding of factors affecting nitrogen balance was to be gained. However, it is possible that the errors associated with these measurements are similar in magnitude to those of nitrogen balance. The variation in measurements of nitrogen bal.ance under our conditions, and in the work of others, indicates that, unlike the determination of dry matter digestibility, the technique is only useful when large treatment differences are likely to be encountered. The number of replicates required and labour involved in detecting smaller differences restricts its usefulness. V. ACKNOWLEDGMENTS The author acknowledges the assistance of Mr. R. J. Williams, Biometrician, Department of Agriculture, N.S.W. Thanks are also due to Mr. M. B. Manson for laboratory analysis and Mr. H. D. Mathers for management of the pigs. VI. REFERENCES ~OCHRAN, W. G., and Cox, G. M. (1960). 'Experimental York). C OLE, D. J. A., DUCKWORTH, J. E., and H OLMES , W. (1967). D UNCAN , D. L. (1966). In 'Recent Advances in Animal J ONES , A. S., and C ADENHEAD , A. (1965). J. Sci. Fd. Agric. M AYO, R. H. (1961). J. Anim. Sci. 20: 71. Designs'. 2nd Ed. (Wiley: New Anim. Prod. 9: 141. Nutrition'. (Churchill: London). 16: 38. 449