Net zinc requirements of Dorper×thin-tailed Han crossbred lambs

Abstract

Comparative slaughter trials were conducted to determine the net zinc (Zn) requirements for Dorper crossbred ram lambs and ewe lambs. Thirty-five Dorper×thin-tailed Han crossbred lambs [20kg body weight (BW)] of each gender were subjected to the same slaughter procedures: seven lambs were randomly chosen and slaughtered at 20kg BW as the baseline group for measuring the initial body composition; another seven lambs were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 28kg BW; the remaining 21 sheep were randomly divided into three groups containing seven sheep each and subjected to the same diet either ad libitum or at 70% or 40% of ad libitum intake. The three groups were slaughtered when the sheep fed ad libitum reached 35kg of BW. Finally, the body Zn contents were determined. The net Zn requirements for maintenance were 97 and 165μg/kg BW for Dorper×thin-tailed Han crossbred ram lambs and ewe lambs, respectively, and the requirements for growth decreased from 23.4 to 23.2mg/kg BW gain for ram lambs and from 23.8 to 22.1mg/kg BW gain for ewe lambs as their BW increased from 20 to 35kg. These findings were similar to those reported by most nutritional systems, except that the maintenance requirements for ewe lambs were greater than the previously published values.