Abstract

Three groups of nine-month-old beef-type steers were fed on a high (Treatment I), medium (Treatment II), or low (Treatment III) nutritional plane for a period of 21 weeks. At the end of this period five cattle of each treatment were slaughtered (average after 23 weeks). The remaining cattle of Treatments II and III (the restricted groups) were then also fed the high nutritional plane such as those from Treatment I and allowed to grow to a final slaughter mass of 440 kg. Treatments were compared on an equal stage (0 weeks-control, 23 and 39 weeks) and mass basis (210 kg-control, 370 and 440 kg live mass) through the whole trial as far as certain hide characteristics were concerned. The most severely restricted animals (Treatment lII) had a lower hide fat percentage content than the moderately restricted (Treatment II) and unrestricted animals (Treatment I) slaughtered after 23 weeks in the trial. This was due to a decrease in the hide fat content of Treatment III during the 23 week period. After a period of compensatory growth, however, no differences were found between the treatments in hide fat content and, therefore, in hide composition. The hide fat content did not increase evenly over the total growth period. The nutritional restriction and/or a subsequent period of compensatory growth had no effect on the solubility of the hide collagen, neither did the hide collagen solubility change during the growth process (increase in mass and time). No significant differences were found in the total hide collagen content between the treatments after a period of nutritional restriction (23 weeks). At the final slaughter points (39 weeks and 440 kg live mass), the unrestricted group (Treatment I) had a higher total hide collagen content than the previously restricted groups (Treatments II and III). The total hide collagen percentage content decreased with growth progress in all the groups. The most severely restricted animals had thinner hides and hide layers (grain and corium major) than the moderately restricted and unrestricted animals after 23 weeks. The latter two groups did not differ significantly in hide layer thicknesses after 23 weeks. However, both the restricted groups had less hide corium fat (amount of fat cells) than the restricted group after 23 weeks. Animals with different treatments did not differ in these hide characteristics, however, after a period of compensatory growth. Animal growth (i.e. increase in mass and time), was characterised by an increase in total hide and layer thickness and the amount of fat cells in the hide corium. The majority of the hide collagen fibres overlapped in the hide corium major with an angle of 45°. A small decline in this angle of collagen fibre overlapping was found with growth progress over the total trial period which might, because of the importance of this characteristic in hide strength, have an influence on hide and hence on leather characteristics. The connective tissue, elastin, was found to be concentrated mainly in the grain layer of the hide.