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The requirement of net protein (NP) and metabolizable protein (MP) by Dorper crossbred ewe lambs grown from 35 to 50 kg of body weight (BW) was assessed by comparative slaughter experiment. Thirty-five ewe lambs (33.5 ± 0.6 kg BW) of F1 crosses of Dorper × thin-tailed Han sheep were used: 7 lambs were slaughtered as reference animals at the start of the trial, and the remaining 28 lambs were randomly divided into 4 groups of 7 lambs each. Three of the 4 groups were fed a pelleted mixed diet (concentrate/roughage = 44:56, dry matter basis) for ad libitum intake or 65% or 45% of ad libitum intake, and they were all slaughtered when the lambs that were fed ad libitum reached 50 kg BW. The lambs from the fourth group were also fed ad libitum and slaughtered at 43 kg BW as the intermediate group. The intake of MP by the animals of these 4 groups was estimated, and their total body protein and protein retention were measured. The daily requirements of NP and MP for maintenance were 1.52 and 3.98 g/kg BW0.75 , respectively, with a partial efficiency of MP utilization for maintenance of 0.38. The MP requirement for growth ranged from 77.4 to 124.5 g/day for average daily gains from 100 to 250 g BW, and the partial efficiency of MP utilization for growth was 0.66. The Dorper crossbred ewe lambs required more MP for both maintenance and growth in comparison with the recommendations of the US nutritional system.

This study aimed to investigate the net and metabolizable energy (NE and ME) requirements of Dorper crossbred lambs. Thirty-five Dorper×thin-tailed Han crossbred intact male lambs weaned at approximately 50 d of age (20.26±1.29 kg of BW), were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of 7 randomly selected lambs fed for ad libitum intake was slaughtered when the lambs reached an average BW of 28.2 kg. The remaining 21 lambs were alloted randomly to 3 levels of dry matter intake: ad libitum, or restricted to 70 or 40% of the ad libitum intake. All the lambs were slaughtered when the ad libitum fed sheep reached 35 kg of BW. Total body energy, crude protein, fat, ash, and moisture contents were determined. In a digestibility trial, fifteen Dorper×thin-tailed Han crossbred intact male lambs (32.38±2.23 kg of BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at 3 feed intake levels. The results showed that the maintenance requirements for NE and ME were 250.61 and 374.21 kJ/kg metabolic shrunk body weight (SBW0.75), respectively. The partial efficiency of energy use for maintenance was 0.67. Net energy requirements for growth ranged from 1.12 to 5.31 MJ/d, for the lambs gaining 100 to 350 g/d from 20 to 35 kg BW. Partial efficiency of ME for growth was 0.42. In conclusion, the current study suggested that the NE requirement for maintenance and growth of Dorper×thin-tailed Han early-weaned crossbred lambs were lower than those reported by existing AFRC and NRC nutritional systems.

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 [20 kg body weight (BW)] of each gender were subjected to the same slaughter procedures: seven lambs were randomly chosen and slaughtered at 20 kg 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 28 kg 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 35 kg of BW. Finally, the body Zn contents were determined. The net Zn requirements for maintenance were 97 and 165 μg/kg BW for Dorper×thin-tailed Han crossbred ram lambs and ewe lambs, respectively, and the requirements for growth decreased from 23.4 to 23.2 mg/kg BW gain for ram lambs and from 23.8 to 22.1 mg/kg BW gain for ewe lambs as their BW increased from 20 to 35 kg. 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.

A comparative slaughter trial was conducted to estimate the phosphorus (P) requirement for maintenance and growth of crossbred lambs of Dorper with a Chinese indigenous sheep breed, thin-tailed Han sheep. Thirty-five Dorper×thin-tailed Han crossbred, noncastrated ram lambs (20.3±0.22 kg of shrunk body weight (SBW)) were used. Seven lambs were randomly chosen and slaughtered at 20 kg SBW as the baseline group for measuring initial body composition. Another seven lambs were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 28 kg SBW. The remaining 21 sheep were randomly divided into 3 groups with 7 sheep each and subject to the same diet of either 70 or 40% of ad libitum intake. The 3 groups were slaughtered when the sheep fed ad libitum reached 35 kg of SBW. Body P contents were determined after slaughter. The results showed that the net P requirement for maintenance was 30.0 mg/kg of empty body weight (EBW) or 23.4 mg/kg body weight (BW), and the P requirement for growth decreased from 5.3 to 5.0 g/kg of EBW gain as the lamb grew from 20 to 35 kg. The net P requirement for growth of Dorper×thin-tailed Han crossbred ram lambs was lower than that of sheep adopted by the American nutritional system.

This study aimed to determine the energy requirements of Dorper crossbred sheep that have been used for meat production in China. Thirty-five 1/2 Dorper×1/2 thin-tailed Han crossbred noncastrated ram lambs [34.1±0.6 kg body weight (BW)] were used in a comparative slaughter trial. Seven ram lambs were randomly selected as the baseline group and slaughtered at 35 kg BW. The remaining 28 lambs were randomly divided into four groups of seven lambs each. Three of the four groups were fed a mixed diet either for ad libitum intake, 60% or 45% of the ad libitum intake. The three groups were slaughtered when the ram lambs that were fed ad libitum reached 50 kg BW. The ram lambs from the fourth group were also fed ad libitum as an intermediate group and slaughtered at 43 kg BW. Total body energy, nitrogen, fat, ash, and moisture content were measured. In a digestibility trial, another 15 ram lambs (41.3±0.8 kg BW) were housed in metabolism cages to estimate the metabolizable energy (ME) value of the diet at the three levels of feed intake. The daily net energy (NE) requirement for maintenance was 263 kJ/kg 0.75 of BW or 278 kJ/kg 0.75 of shrunk BW (SBW), with a partial efficiency of ME utilization for maintenance of 0.69. The NE requirement for growth ranged from 1.12 to 5.31 MJ/d for daily gains of 100–400 g BW, or from 1.29 to 6.18 MJ/d for daily gains of 100–400 g SBW. The partial efficiency of ME utilization for growth was 0.46. The energy requirements of Dorper×thin-tailed Han crossbred ram lambs were lower than those recommended by the British or American nutritional systems.

This study investigated the effects of protein sources for milk replacers on growth performance and serum biochemical indexes of suckling calves. Fifty Chinese Holstein bull calves with similar BW and age were randomly allocated to 5 groups (1 control and 4 treatments) of 10 calves in each group. Five types of milk replacers were designed to have the same level of energy and protein. The protein source for milk replacers of the control group was full milk protein (MP). The protein source of milk replacers of the 4 treatment groups was composed of MP and one vegetable protein (VP) (30 and 70% of total protein). The 4 types of VP were soybean protein concentrate (SP), hydrolyzed wheat protein (WP), peanut protein concentrate (PP), and rice protein isolate (RP). Results of the experiment showed: 1) there was no significant difference on average daily gain (ADG) and feed:gain ratio (F:G) among the MP, SP and RP groups (P > 0.05), whereas the ADG and F:G of the WP and PP groups were significantly lower compared with the MP group (P 0.05). Thereby the 4 VP milk replacers had no adverse effects on body size of calves; 3) all groups showed no significant difference in the serum contents of urea nitrogen, total protein, albumin, globulin, β-hydroxybutyrate, growth hormone, insulin-like growth factor-1, and the ratio of albumin to globulin (A:G) (P > 0.05). In conclusion, SP or RP (accounts for 70% of the total protein) as calf milk replacers could substitute MP, whereas wheat gluten and PP had a significant adverse effect on growth performance in this experiment.

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35 kg were assessed in a comparative slaughter trial. Thirty-five Dorper × thin-tailed Han cross-bred female lambs weaned at ~50 days of age (20.3 ± 2.15 kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed ad libitum was slaughtered when the lambs reached an average BW of 28.5 kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: ad libitum or restricted to 70% or 40% of the ad libitum intake. All the lambs were slaughtered when the sheep fed ad libitum reached a BW of 35 kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper × thin-tailed Han cross-bred female lambs (28.7 ± 1.75 kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3 kJ/kg metabolic shrunk body weight (SBW0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18 MJ/d for the lambs gaining 100-350 g/d from 20 to 35 kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.