The effect of lysine intake on energy partitioning and utilization in growing pigs

Abstract

An experiment utilizing 12 castrated male pigs within a body weight range of 23 – 147 kg was conducted to ascertain whether the alteration of protein quality by varying the level of lysine intake is influencing total energy retention, heat production and therewith efficiency of energy utilization for growth. The animals were allotted to two treatments of a constant medium (11.5 g/d) or high lysine intake (13.5 g/d) level on the basis of an isonitrogenous diet at an energy intake level of 1.3 MJ ME/kg BW^0.75. Representing a tool for determining body composition, at target body weights of 35, 55, 80, 115 and 145 kg measurements of deuterium dilution space were undertaken. Protein and lipid accretion were calculated by difference, assuming accretion to contain 23.8 and 39.0 kJ/g, respectively. The results show a significant effect (p < 0.05) between treatment groups for the values of energy retained in protein, thus ensuring the intended alteration by protein quality. Furthermore total energy retention, heat production (difference between ME intake and energy retention) and therewith energy utilization demonstrate independence from the composition of body weight (BW) gain. These observations confirm earlier results, but however, seem to be in contrast to the supposition of a constant efficiency for protein (k_p) and fat (k_f) accretion, respectively. This may be attributed to a variable k_p, in fact to a smaller k_p at minor values for protein accretion due to an increased whole body protein turnover. Lacking evidence from experimental data for advantages in using constant values for k_p and k_f to determine the accurate energy requirement for growth, a uniform value for the efficiency of total energy retention seems to be more adequate.

Keywords:

• Growing pigs
• lysine
• energy partitioning
• energy utilization

Acknowledgements

The authors are most grateful to the Institute of Animal Nutrition, University of Hohenheim for providing the facilities to measure D₂O concentration, especially to Dr H. Steingass for scientific support and R. Haller for technical assistance. They thank C. Benthin for excellent care of the animals and Dr G. Rave for his valuable advice regarding statistical analyses of the data. Financial support of this study by the “Deutsche Forschungsgemeinschaft” (DFG, German Research Foundation, grant SU 103/4-1) is gratefully acknowledged.