Allometric relationships determined for skin area and fleece production of Angora goats

This study aimed to determine the relationships between skin surface area, animal size and mohair physical properties using estimates of skin area determined on animals prior to slaughter and to compare these with skin weight and skin area determined after slaughter. Angora kids born in late winter were shorn at 18 weeks of age. Prior to slaughter at 20 weeks of age, 15 kids of each sex were identified to cover the entire range of live weights. Body girth, body length circumference and body condition score were determined. Following slaughter, skins were weighed and skin area determined. Clean fleece weight and mean fibre diameter (MFD) were determined. Parsimonious general linear models were developed to determine the relationships between measured skin area, estimated skin area, live weight and skin weight, clean fleece weight and MFD both with and without log10 transformation. Live weights ranged from 8.3 to 23.1 kg, skin weight from 796 to 2262 g and measured skin area 0.23 to 0.59 m2. The weight of the skin represented 9.6% of the average live weight of the goats. Predicting measured skin area using body dimensional measurements accounted for 83.7% of the variance in measured skin area. Measured skin area was a constant 0.057 m2 greater than the estimated skin area. It was more accurate to use live weight to estimate measured skin area as the regression between estimated skin area and live weight accounted for 93.7% of the variance. Measured skin area and clean fleece weight were proportional to live weight 0.67, which is the general allometric relationship expected between the surface area of a shape and its volume. Both clean fleece weight and MFD were proportional to measured skin area but were better predicted by live weight. Predicting skin surface area using live weight 0.67 was more reliable than using body dimensional measurements.