ALLOMETRIC ANALYSIS OF RAM GROWTH IN THE POSTNATAL-PERIOD

Gradual slaughters of animals from birth to 18 months of age were carr ied out to evaluate changes in body conformation of rams of the Merino breed in ontogenesis. General allometric equation y = a.x(b) (Huxley, 1932) was used for mathematical expression of the lack of growth unif ormity. As a working form of the mathematical model its logarithmic tr ansformation log y = log a + b. log x was used. Tables show log a valu es and growth constant b. Allometric coefficients were calculated for three growth stages: 1) early postnatal period (1-14 days of age), 2) period of intensive growth (1-5 months), 3) period when breeding matur ity has been attained (6-18 months). Morphological changes are reflect ed by intensive growth of thoracic limbs which is shifted from the neg ative value of b in the second growth stage (b = 0.59) to an isometric zone in the 6-18 month stage while the coefficient remains largely ne gative for the pelvic limbs (b = 0.71). This can explain the balancing of animal overgrowth at the end of the third stage concerned. The ski n including fleece gradually increases its growth rate up to b = 1.20 in the oldest animals under evaluation. An increase in forestomach wei ght shows the highest pace in the middle growth stage (b = 1.32), i.e. in the period of lamb habituation to bulk feed and increase in their intake. An increase in the growth rate of flank is related to the latt er. Allometric constants of the spleen are always negative, with an ob vious decrease in the values from the first to the third age stage eva luated. While the second stage is characterized by the highest growth rate of forestomachs, the allometry of the sides of mutton is consider ably increasing in the third stage (b = 1.28). The secretion organs (l iver, kidneys) show a steep fall of the allometry coefficient in the t hird stage in comparison with the second stage while the organs of blo od formation and circulation (spleen and heart) have the highest value s of b in the last growth stage. The coefficients of the investigated carcass parts are ranked in a typical caudal-cranial gradient in the t hird stage (leg 0.84 - loin 1.02 - rib 1.18 - scrag 1.28). Changes in carcass composition are accompanied by the widening of the meat to bon e ratio. An increase in the values of deboned meat was observed with t he growing age in all cases.