,140 INTRODUCTION. Werribee, Victoria, Parkville, Victoria, 3052.

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1 ,140 THE EFFECTS OF NUTRITION IN EARLY LIFE ON SUBSEQUENT GROWTH AND DEVELOPMENT IN THE PIG R.G. CAMPBELL* and A.C. DUNKIN** INTRODUCTION There is considerable evidence that nutrition in the early postnatal period influences subsequent growth and development. For ex,ample research with rats (Knittle and Hirsch, 1968) and humans (Brook, 1972) suggests that over feeding during infancy stimulates the proliferation of fat cells and that this, in turn, predisposes to obesity in later life. Conversely, low levels of feeding in early life have been reported to retard the hyperplasic development of muscle tissue and to impair subsequent growth performance in both rats (Winick and Noble, 1966) and poultry (Moss, 1968). Clearly, these findings, if applicable, could have important implications with respect to the nutritional management of the young pig. Unfortunately, information on the effects of nutrition in the early postnatal period on tissue cellularity and subsequent growth and development in the pig is both limited and contradictory. Robinson (1969) and Lodge et al. (1977) reported that a feed restriction imposed in early life reduced muscle DNA and impaired subsequent growth performance. However, in both these studies the pigs were compared at constant age but at widely different body weights, and feeding ad libitum was practiced in the period subsequent to that in which the initial treatments were imposed. Consequently, the effects of nutrition in early life on muscle DNA were confounded with the effects of body weight while the influence of the initial treatments on subsequent growth performance may have been confounded with differences in voluntary feed intake in the later period. In the only experiment published on the effects of nutrition in early life on the cellularity of porcine adipose tissue Lee et al. (1973a and b) concluded that hyperplasic development of subcutaneous adipose tissue was complete prior to birth and suggested therefore that fat cell number could not be influenced by post-natal nutrition. Yore recent data however, suggests that the hyperplasic development of porcine adipose tissue continues to at least 188 days of age (Hood, 1977; Wood et al. 1978). This paper summarises the results of a series of experiments designed to study the influence of nutrition in the early post-natal period on subsequent growth and development in the pig. * Present address, Animal Research Institute, Princes Highway, Werribee, Victoria, ** School of Agriculture and Forestry, University of Melbourne, Parkville, Victoria, 3052.

2 EXPERIMENTAL METHODS Pigs were weaned hours after birth and were reared, in individual cages, on liquid diets containing varying proportions of ultra-filtered skim milk powderi dextrose, soya bean oil and butter fat. The initial treatments which were imposed from 1.8 to 6.5, 10, 15 or 20 kg were designed to produce marked differences in growth rate and body composition. Cereal-based dry diets replaced liquid diets from kg in those experiments which continued to heavier,weights. Representative animals were slaughtered at the beginning of each.experiment and at the end of each phase of the dietary treatments. The effects of various treatments were assessed in terms of rate and efficiency of weight gains and chemical composition of the empty body. The cellularity of muscle and subcutaneous adipose tissue? was also measured. EFFECT OF FEED RESTRICTION DURING EARLY DEVELOPMENT Two experiments were conducted to study the effects of level of feeding in early life on subsequent growth and.development. In the first experiment, which was designed to examine carryover effects in the phase immediately subsequent to the termination of the initial treatments, the same protein-adequate diet (33% protein calories) was fed at either twice (2M) or 4.6 (4.6M) times maintenance from 1.8 to 6.5 kg. Subsequent to 6.5 kg both groups were fed a diet containing 26% protein calories at 4M to 11.5 kg. As expected, the pigs fed at 4.6M during the initial phase grew more rapidly and were fatter at 6.5 kg than those fed at 214 (Table 1). Fat cell size at 6.5 kg was also increased in pigs fed at the.higher level while muscle DNA was the same for both groups (Table 1).. TABLE 1 Effects of level of feeding from 1.8 to 6.5 kg on pig performance, body fat content and the cellularity of muscle and adipose tissue

3 142 Subsequ'ent to 6.5 kg the pigs previously fed at 2M exhibited.more rapid and efficient growth (P<O.Ol) and were still leaner and contained smaller fat cells at 11.5 kg than those fed at 4.6M prior to 6.5 kg (Table 2): Fat cell number at 11.5 kg was unaffected by level of feeding prior to 6.5 kg (Table 2). TABLE 2 Effects of level of feeding from 1.8 to 6.5 kg on the performance of pig.s growing from 6.5 to 11.5 kg and on body fat content and the.cellularity of muscle and adipose tissue at 11.5 kg The second experiment concerned the longer term effects of feed restriction in early life on growth rate and body composition at 75 kg. Pigs were fed a common diet at either 2.8M or 4.5M from 6.5 to 20 kg and at the same level (approximately 4M) subsequent to 20 kg. Pigs fed at the lower level grew at a slower rate and were leaner at 20 kg than those fed more generously. HoweverI subsequent to 20 kg the pigs previously fed at 2.8M exhibited more rapid and efficient growth than those fed at 4.5M prior to 20 kg. Overall, feed restriction between 6.5 and 20 kg increased the total time to reach 75 kg by 5.7%, but reduced the total feed required by 10.6% and carcass lipid at 75 kg by 8.5%. Comparison of changes in body composition between treatment groups showed that the magnitude of the induced differences gradually declined as weight increased. The data also suggested that compensatory growth following removal of feed restriction was associated with enhanced rates of retention of protein, fat and water. Level of feeding prior to 20 kg had no effect on muscle DNA or fat cell number at either 20 or 75 kg live weight.

4 143 Z?F'F:CTS OF PROTEIN RESTRICTION IN EARLY LIFE The results of two experiments showed that in contrast to the effects of feed restriction, protein deprivation during early development had an adverse effect on muscle DNA and impaired subsequent growth performance. The latter effect however, was only evident when nutrition in the later period permitted near maximum.growth performance. In the first experiment pigs were fed either a low (15% protein calories) or high (33% protein calories) protein diet at 4,OM from 1.8 to 6.5 kg and a moderate (15%) or high (22%) protein diet at 3.2M from 6.'5 to 45 kg. Pigs fed the low protein diet grew more slowly to 6.5 kg and. were fatter atthe latter 'weight than those fed the high protein diet (Table 3). Pigs fed the low protein diet also contained less DNA in the m. adductor and had larger fat cells at 6.5 kg than those fed -the high protein diet (Table 3). TABLE 3 Effects of protein nutrition from 1.8 to 6.5 kg on growth performance, body fat content and the cellularity of'muscle and adipose tissue There was a significant (PcO.05) interaction between the eff,ects. of protein nutrition prior and subsequent to 6.5 kg on growth performance between 6.5 and 45'kg (Table 4). When fed the diet of moderate protein conten-t, subsequent to 6.5 kg, pigs previously fed the low protein diet grew at a faster rate than those fed the high protein diet prior to 6.5 kg. This trend however, was reversed when the high protein diet was fed subsequent to 6.5 kg. This suggested that potential for growth had been impaired by protein restriction in the period prior to 6.5 kg.

5 144 TABLE 4 Effects of protein nutrition prior and subsequent to 6.5 kg on the rate of gain of pigs growing from 6.5 to 45 kg The difference in body composition between the two initial groups. had disappeared at 45 kg. However, pigs previously fed the low protein diet contained fewer but larger fat cells thanthose fed the high protein diet prior to 6.5 kg'(table 5). It appeared therefore that the hyperplasic development of adipose tissue had also been reduced by protein restriction in the period 1.8 to 6.5 kg. TABLE 5 Effects of protein nutrition between 1.8 and 6.5 kg on body fat content and the cellularity of muscle and subcutaneous adipose tissue at 45 kg

6 145 These findings were confirmed by the results of a second experiment, in which the effects of protein nutrition between 1.8 and 15 kg on subsequent growth and body composition were investigated in pigs grown to 75 kg. The latter results also showed that the effects of protein deprivation in early life on muscle DNA, body composition and the cellularity of adipose tissue gradually diminished as live weight increased. The persis,tence of the initial differences was dependent oh nutritional status in the later period. Overall, the results of,both experiments showed that restricting protein intake in early life increased both age at 'slaughter and total feed usage but had no effect on body composition at live weights in 'excess of 60 kg. DISCUSSION The results clearly demonstrated that level of feeding and protein nutrition in early life had marked but different effects on subsequent growth and development. A feed restriction whether imposed between 1.8 and 6.5 kg or between 6.5 and 20 kg had no effect on the hyperplasic development of muscle.or subcutaneous adipose -tissue. The data also showed that the extra fat accumulated by pigs fed more generously in early life was accommodated by an increase in fat cell size. It was also evident that feed restriction in early life had 'no adverse effect on subsequent growth performance. Indeed, the results suggest that the pig has considerable propensity for compensatory growth following a period of restricted feeding. Furthermore, it appears that this attribute may be comme,rcially exploitable.. In particular, our data suggest that for pigs grown to light bacon weight (75 kg), a degree of feed restriction between weaning at 3-4 weeks of age and kg, may be a tire profitable feeding strategy than the more common practice of feeding ad libitum during this period. On the other'hand, protein deprivation in early life retarded the hyperplasic development of both muscle and adipose tissue and ' impaired subsequent growth performance. These effects however, were transitory,- and it is unlikely therefore that protein restriction in early life will have any adverse effects on growth on development in the long term. Nevertheless, from a more practical aspect the data showed that protein insufficiency during early development increased both age at commercial slaughter weights and total feed usage. Consequently, diets for young pigs should contain adequate levels of protein and/or essential amino acids. REFERENCES BROOK, G.C.D. Lancet (1972). ii, 624. HOOD, R.L. and ALLEN, C-E. (1977). Proc. Nutr. Soc. Aust. 2: 43 KNITTLE, J.L. and HIRSCH, J.,(1968). J. Clin. Invest. 47: LEE., Y.B., KAUFFMAN, R.G. and GRUMMER, R.H. (1973). J.Anim.Sci. 37: LODGE, G-A., SARKAR, N.K. and FRIEND, D.W. (1972).lJ. Anim. Sci-25: MOSS, F.P. (1968). Amer. J. Anat. 122: 555. ROBINSON, D.W. (1969). Growth 33: 231. WINICK, M. and NOBLE, A. (1966). J. Nutr. 89: 300. WOOD, J.P., 'ENSER, M.B.,and RESTALL, D.J. (197.8). Anim. Prod. 27: 1