Compensatory growth in pigs

Our thanks to the author and Conference Organisers, a Committee consisting of both University and Industry colleagues.

The full paper will appear in the Conference Proceedings ('Recent Advances in Animal Nutrition - 2007', edited by Phil Garnsworthy and Julian Wiseman) published by Nottingham University Press in the autumn of 2007 www.nup.com

Compensatory growth in pigs - Image 1

Courtesy of the 41st Annual University of Nottingham Feed Conference www.nottingham.ac.uk/biosciences/ah/research/conferences.php

Numerous investigations have explored compensatory or catch up growth (CG) in pigs following a period of nutrient intake restriction. These studies indicate that the extent and rate of CG vary with the type, degree, timing and duration of nutrient intake restriction, as well as the pig’s genotype and nutrient availability following the period of nutrient intake restriction. Underlying mechanisms that control CG and that allow for prediction of the rate and extend of CG remain to be fully elucidated.

Based on observations on the dynamics of CG following a period of amino acid intake restriction (Qualitative nutrient intake restriction), we propose that the rate and extent of CG is constrained by the pigs’ upper limit to body protein deposition (PdMax) and is driven by a target whole body lipid to whole body protein ratio (TargetL/P).

These concepts imply that CG following a period of amino acid intake restriction occurs primarily during the energy dependent phase of body protein deposition and is unlikely to occur in growing pigs with relatively low PdMax, i.e. low lean tissue growth potentials.

In practical terms, this means that at the end of the amino acid intake restriction period, body fatness (whole body lipid to whole body protein ratio; L/P) of pigs is higher than TargetL/P and, once the amino acid intake restriction is removed, pigs will increase Pd – constrained by PdMax – and reduce body lipid deposition to achieve TargetL/P.

Apparently CG following amino acid intake restriction is merely a repartition of feed energy for production between body protein deposition and body lipid deposition.

Various studies have shown that the (marginal) biological efficiency of using available amino acid intake for body protein deposition is not improved during CG.

These concepts can be used to explore CG as a means to manipulate carcass and meat quality, nutrient utilization efficiencies, reduce gut health problems induced by feeding large amounts of protein, to simplify feeding strategies such as phase feeding, and thus to improve pork production efficiencies.

Indeed, well-controlled studies, such as these on phase feeding at the MLC in the UK using pigs with high lean tissue growth potentials and between 35 and 102 kg body weight, show that pigs fed a single diet achieve the same or better growth performance as compared to pigs that were exposed to phase feeding to closely meet that pigs’ changing amino acid requirements at the various stages of growth, when cumulative amino acid intakes are kept similar for both feeding strategies.

Such observations are highly consistent with the proposed concepts.

These concepts may also apply to CG following periods of feed intake restriction (Quantitative nutrient intake restriction). However, in that case feeding level and diet composition effects on the size and chemical composition of the visceral organs – especially those involved in food processing – should be considered explicitly.

In several well-controlled studies CG following a period of feed intake restriction can be attributed fully to CG in visceral organs.

However, in other studies some CG has been observed in carcass protein and carcass lipid deposition following periods of feed intake restriction. The dynamics of voluntary feed intake during CG are not well understood, especially following a period of feed intake restriction, when pigs will attempt to increase both body lipid deposition, to achieve targetL/P, and body protein deposition, to reach a target body protein mass relative to the pigs’ physiological age.

In order to exploit CG commercially, populations of pigs need to be characterized in aspects of nutrient partitioning for growth. In particular, the changes in PdMax and TargetL/P with time or increasing body weight need to be characterized.

We suggest that the assumption that PdMax is independent of body weight up to about 85 kg of body weight is acceptable for the routine characterization of pig genotypes and allows accurate representation of the dynamics of CG following a period of amino acid intake restriction.

The increase in daily body protein deposition with time or body weight in young growing pigs must then be represented based on changes in daily energy intake and TargetL/P. TargetL/P is known to increase with both level of energy intake and body weight.

However, body weight effects can be attributed largely to increases in energy intake with body weight. Therefore, a simple (linear) relationship between absolute daily energy intake and TargetL/P may be used to routinely characterize TargetL/P in different pig genotypes.

More quantitative information is required to represent the impacts of feeding level, diet characteristics and pig genotype on the size and chemical composition of visceral organs. Dynamic and mechanistic pig growth models will be useful to exploit CG in commercial pork production.

Selected references

Bikker, P. (1994). Protein and lipid accretion in body components of growing pigs. PhD. Thesis Department of Animal Nutrition Wageningen Agricultural University, Haagsteeg 4, 6708 PM Wageningen, The Netherlands.

Kristensen, L., Therkildsen, M., Aaslyng, M.D., Oksbjerg, N. and Ertbjerg, P. (2004). Compensatory growth improves meat tenderness in gilts but not in barrows. Journal of Animal Science 82, 3617-3624.

Kyriazakis, I. and Emmans, G. (1992b). The growth of mammals following a period of nutritional limitation. Journal of Theoretical Biology 156:485-498.

Martínez-Ramírez, H.R. (2005). Characterization of the dynamics of body protein deposition response following sudden changes in amino acid intake. M.Sc. Thesis. Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada.

MLC (2004). Finishing pigs: Systems Research. Production trial 2: evaluation of phase feeding in two contrasting finishing systems (fully slatted versus straw based housing). Meat and Livestock Commission, Milton Keynes, UK.

Weis, R.N., Birkett, S.H., Morel, P.C.H. and de Lange, C.F.M. (2004). Effects of energy intake and body weight on physical and chemical body composition in growing entire male pigs. Journal of Animal Science 82, 109-121.

Author: H.R. Martínez-Ramírez and C.F.M. de Lange
Centre for Nutritional Modelling, Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada. N1G 2W1

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