Net protein and metabolizable protein requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

Background： Dorper is an important breed for meat purpose and widely used in the livestock industry of the world.However, the protein requirement of Dorper crossbred has not been investigated. The current paper reports the net protein（NP） and metabolizable protein（MP） requirements of Dorper crossbred ram lambs from 20 to 35 kg BW.Methods： Thirty-five Dorper × thin-tailed Han crossbred lambs weaned at approximately 50 d of age（20.3 ± 2.15 kg of BW） were used. Seven lambs of 25 kg BW were slaughtered as the baseline animals at the start of the trial. An intermediate group of seven randomly selected lambs fed ad libitum was slaughtered at 28.6 kg BW. The remaining 21 lambs were randomly divided into three levels of dry matter intake： ad libitum or 70% or 40% of ad libitum intake. Those lambs were slaughtered when the lambs fed ad libitum reached 35 kg BW. Total body N and N retention were measured.Results： The daily NP and MP requirements for maintenance were 1.89 and 4.52 g/kg metabolic shrunk BW（SBW0.75）.The partial efficiency of MP utilization for maintenance was 0.42. The NP requirement for growth ranged from 12.1 to 43.5 g/d, for the lambs gaining 100 to 350 g/d, and the partial efficiency of MP utilization for growth was 0.86.Conclusions： The NP and MP requirements for the maintenance and growth of Dorper crossbred male lambs were lower than the recommendations of American and British nutritional systems.

Effects of protein sources for milk replacers on growth performance and serum biochemical indexes of suckling calves

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). The4 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); 2) there was not a significant difference in withers height, body length and heart girth among treatment groups 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.