Abstract:
A NUTRITIONAL EFFECT ON RELATIVE GROWTH OF MUSCLES R. M. BUTTERFIELD* and R. T. BERG Summary Relative growth within the musculature of calves fed to LH and HH growth patterns was compared by studying changes in the percentage of total muscle represented by eleven muscles of known 'high/average impetus' growth patterns. These muscles in both groups of calves completed their high impetus phase when total half-carcase muscle weight was approximately 10 kg. The LH group took approximately 12 weeks to reach this weight, and the HH group less than 8 weeks. The low plane of nutrition retarded the growth of muscles uniformly when related to total muscle weight and differentially when related to age. 1. INTRODUCTION The effect of nutrition on the relative growth of muscles has not been clearly defined. Conflicting views on the effects of nutrition on the relative growth of body tissues have recently been discussed by Elsley, McDonald and Fowler ( 1964). The major difference in interpretation of experimental results by various authors has been the nature of the effect of sub-optimal nutrition on the relative growth of the various carcase tissues. Some authors have indicated that a uniform retardation of development occurs (Wallace 1948; Wilson 1952, 1954a, 1954b, 1958; Tulloh 1963) while others have demonstrated a differential effect (McMeekan 19400, 1940b, 194Oc; Palsson a n d V e r g e s 1952a, 1952b; Palsson 1955). The greatest differential changes of muscle weights occur during the first three months of post-natal life (Butterfield 1965; Butterfield and Berg 1966) Y and it is in this period that the effects of nutrition on relative growth of muscles may be most apparent. This paper reports the effects of different calf-rearing procedures during the first 22 weeks of post-natal life on the relative growth of muscles with 'high/ average impetus' growth patterns (Butterfield and Berg 1966). II. METHODS AND MATERIALS The feeding and management of the 20 Australian Illawarra Shorthorn calves used in this trial have been described (Butterfield, Pryor and Berg 1966). Briefly, two groups each of five calves were reared on different dry meals following weaning at two weeks. In these calves, a severe post-weaning check occurred so that the growth curve of both groups followed a low-high pattern. Mean values of this pair of groups are represented in tables and figures by the symbol 'L'. Two other groups .which were fed two different diets adequate in milk and other food throughout the experimental period grew to a high/high pattern and their mean values are represented by the symbol 'H'. 'Sub-Department of Veterinary Anatomy, University of Queensland. j-Department of Animal Science, University of Alberta, Edmonton, Canada. 298 Body weight curves have been presented elsewhere (Butterfield, Pryor and Berg 1966) and are reflected in the growth of muscle weight shown in Figure 1. The present study is concerned with the relative changes of weight of individual muscles grown on these two patterns with the region of major interest between birth and fifteen weeks. At 4, 8, 12, 15 and 22 weeks, the heaviest calf remaining in each of the four groups was slaughtered and the right sides of the carcases dissected into individual muscles (Butterfield, Pryor and Berg 1966). Data from seven A.15 calves slaughtered when one day old were also used. Eleven muscles, with 'high/average impetus ' growth patterns were compared between the 'L' and 'H' groups . These muscles, which are listed in Table 1, were shown by Butterfield and Berg ( 1966) to grow relatively faster than total muscle in the first three months of post-natal life (high impetus) and TABLE 1 In&vidual muscle weights as percentage of total muscle weight in calves of diflerent ages, grown on diflerent growth patterns ('L' & 'H') (Each 'L' or 'H' due represents a mean for two calves) 299 then to reduce to a relative growth rate equal to that of total muscle (average impetus). III. RESULTS In Table 1 are set out the weights of the 11 muscles of the 'L' and 'H' groups expressed as a percentage of total muscle weight of the half-carcase. At four weeks, all the values for the 'H' group were greater than the values for the 'L' group. At eight weeks, nine muscles were relatively heavier in the 'H' group and two muscles were the same relative weight. At twelve weeks three muscles, at fifteen weeks six muscles and at twenty-two weeks four muscles out of eleven were relatively heavier in the 'H' group. Figure 2 shows the pooled percentage value of the eleven muscles from the two groups of calves plotted against age. In Figure 3 the same values are plotted against total side muscle weight. The two planes of nutrition resulted in different growth patterns relative to time but in a similar pattern relative to muscle weight. IV. DISCUSSI0N Different patterns of growth of total muscle shown in Figure 1 had a marked effect on the timing of the relative growth changes of the muscles studied, but had no effect on the magnitude of the changes over the whole period. The proportion of total muscle weight represented by the sum of the weights of the eleven individual muscles used in this study is given by Butterfield and May ( 1966) as 36.2% in adult cattle. This value was achieved at approximately 10 kg total halfcarcase muscle weight on both planes of nutrition in the present study, being reached by the 'H' group when between 4 and 8 weeks old and by the 'L' group when about 12 weeks old. The percentage values of the individual muscles in Table 1 follow the same pattern as the pooled percentage of the eleven muscles. Although the data are limited, it is clear that:(a) The high impetus phase of development in the diphasic growth pattern of the muscles studied occupied only a very short span of post-natal life and was completed before the muscle weight at birth had doubled. (b) Low plane nutrition prolonged the time taken to complete the high impetus growth phase of the muscles studied, but did not alter the weight relationship between these muscles and total muscle at any given total muscle weight. The fact that under both nutritional regimes, growth of the muscles studied proceeded on similar pathways relative to total muscle weight supports the claim of Wallace ( 1948) that the normal allometric relationships continue under low plane nutrition and seems to disagree with Palsson ( 1955, 1963) that tissues are retarded in proportion to their growth intensity. However, if the results are interpreted over an age interval from birth it is seen that they also support Palsson's statement, since the 'high impetus phase ' of growth was extended in time by low nutrition. The present study involved calves during an age interval when differential muscle growth was maximum and the nutritional stress imposed did not result in muscle weight loss. Elsey, McDonald and Fowler ( 1964) suggested that loss of weight involves physiological mechanisms other than those concerned in the regulation of growth. Butterfield (1966) showed that severe loss of bodyweight was associated with a selective depletion of muscle groups which could be related 300 Fig. l.-Weight of muscle in the half-carcases of calves in groups 'H' and 'L' as determined by dissection. Each 'H' or 'L' symbol is the mean value for two calves. 'B' = value for seven calves slaughtered when one day old. 301 AGE (weeks) ` HIGH/AVERAGE IMPETus' nnusc~Es A S YO 0~ TOTAL MUSCLE MUSCLE F i g . 3.-Percentage of total impetus' muscles in groups Each 'H' or 'L' symbol is calves slaughtered when one WEIGHT (kg) muscle weight represented by eleven 'high/average 'H' and 'L' related to half-carcase muscle weight. the mean value for two calves. 'B' = value for seven day old. 303 to their order of development. Reanalysis of data from these adult cattle showed that the eleven 'high/average impetus' muscles used i n th.e current paper represented a significantly (P < 0. 0 1) smaller proportion of total muscle in semistarved cattle than in normal cattle. It can be concluded impetus in early life are nutrition which results in retards growth in young affect the relative weights that muscles with a relatively high post-natal growth particularly susceptible in adult animals to inadequate bodyweight loss. However low plane nutrition which animals without bodyweight loss does not differentially of muscles at any given total muscle weight. VI. REFERENCES R. b M. ( 1965 ). Practical implications of anatomical research in beef cattle. Proceedings of the New Zealund Society of Animal Production 25: 152. B UTTERFIELD , R. M. (1966). The effect of nutritional stress and recovery on the body composition of cattle. Research in Veterinary Science (in press). B UTTERFIELD , R. M. , and B ERG , R. T. (1 966). 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