The net protein (NP) and metabolizable protein (MP) requirements of Dorper crossbred female lambs from 20 to 35 kg body weight (BW) were assessed in a comparative slaughter trial.  Thirty-five Dorper×thin-tailed Han crossbred lambs weaned at approximately 50 d of age ((19.1±2.37) kg of BW) were used.  Seven randomly selected lambs were slaughtered at the beginning of the trial as baseline group (BL).  An intermediate group of seven randomly selected lambs fed ad libitum (AL) intake was slaughtered when the lambs reached an average BW of 28.6 kg.  The remaining 21 lambs were allotted randomly to three levels of dry matter intake: AL or restricted to 70 or 40% of the AL intake.  All lambs were slaughtered when the sheep fed AL intake reached 35 kg of BW.  Total body N and N retention were determined.  The results showed that the maintenance requirements for NP and MP were 1.75 and 3.37 g kg^–1 metabolic shrunk body weight (SBW^0.75), respectively.  The partial efficiency of protein use for maintenance was 0.52.  The NP requirements for growth ranged from 10.9 to 42.4 g d^–1 for the lambs gaining 100 to 350 g d^–1 from 20 to 35 kg BW.  The partial efficiency of MP for growth was 0.52.  In conclusion, the NP and MP requirements for the maintenance and growth of Dorper crossbred female lambs were lower than those reported by AFRC (1993) and NRC (2007) recommendations.

   We evaluated the effects of diets with different crude protein (CP) levels on growth performance, rumen fermentation and bacterial communities in weaned Chahaer lambs. 128 weaned Chahaer lambs ((20.56±1.43) kg body weight; ram:ewe 1:1) aged (61±1.85) d were randomly allotted to one of four diets with CP content of 11.17% (T1), 12.06% (T2), 13.40% (T3) or 14.36% (T4). Ruminal fermentation parameters were measured and bacterial communities were analysed using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR. The average daily gain and feed utilization efficiency in T3 were higher than those in the other groups (P<0.05), although the dry matter intake and metabolizable energy intake were similar. Total volatile fatty acid concentration in the ruminal fluid of T3 was lower than that of T1 (P=0.011), T2 (P=0.008) or T4 (P=0.309). The ammonia nitrogen concentration and acetate/propionate ratio of ruminal fluid were significantly higher in lambs fed the higher CP diets, whereas the molar concentrations of propionate and butyrate of ruminal fluid were lower. The rumen bacterial community was similar in T2 and T3 which shown more stable and diverse rumen microbes ecosystem compared with the other groups. The DGGE profiles and phylogenetic tree indicated that Bacteroides uniformis, Clostridium alkalicellulosi, Alkalibaculum bacchi and Saccharofermentans sp. were common bacterium of Chahaer lamb rumen. B. uniformis, C. alkalicellulosi, Saccharofermentans sp. and Gracilibacter thermotolerans, which belong to the Bacteroidetes and Firmicutes phyla, were the dominant species in the rumen of lambs fed 13.40% CP. However, Ruminococcus albus, Ruminococcus flavefaciens and Butyrivibrio fibrisolvens were not different in lambs fed different CP diets. Therefore, it could be concluded that B. uniformis, C. alkalicellulosi, A. bacchi and Saccharofermentans sp. were common bacteria of Chahaer lamb rumen. Furthermore, the dietary CP of 13.04% could improve performance and change rumen fermentation model by increasing the dominant species’ peak intensities of B. uniformis, C. alkalicellulosi, Saccharofermentans sp. and Gracilibacter thermotolerans and stabilizing rumen microbial ecosystem.

Two feeding patterns of the segregated weaning or grazing in the pasture are carried out worldwide in animal production. To investigate the difference of growth performance and rumen microorganism population related to methane metabolism in the two feeding patterns, three groups of lambs (70 in total) were used: Weaning at 21 days old and being subjected to high-concentration diets (3WK group with 20 lambs), weaning at 35 days old and being subjected to high-concentration diets (5WK group with 20 lambs), or grazing at pasture with the nursing mother (Grazing group with 30 lambs). The growth performance, pH value of rumen content, and the rumen microbes were investigated during weaning period and fattening period with approximately 3 months. Our results showed that lambs in 3WK and 5WK groups demonstrated a better growth performance than the lambs in Grazing group, but no significant difference was observed in the pH value between the three groups (P>0.05). The total rumen bacterial population of the Grazing lambs was significantly lower than that of 3WK lambs (P<0.05) and 5WK lambs (P<0.05); however, the population of methanogens was 4.2- and 2.7-fold lower in the 3wk (P<0.05) and 5wk (P<0.05) lambs compared with Grazing lambs, respectively; protozoa were also 3.5- and 3.4-fold lower in the 3WK (P<0.05) and 5WK (P<0.05) lambs, respectively. The results revealed that segregated weaning lambs may have better growth performance, and reduce methane-producing microbes.

This experiment was conducted to investigate the energy requirement of Dorper×thin-tailed Han crossbred ewes during non-pregnancy and lactation. Fifteen ewes after parturition were randomly assigned to three treatments: ad libitum (100%) feed intake and 80 or 60% ad libitum intake, and another nine non-pregnant ewes were assigned to a blank control group. Digestibility trials were performed in the non-pregnant ewes and in the lactating ewes on the 20th, 50th, and 80th d of lactation. In parallel with the digestibility trial, a respirometry experiment was conducted to determine the methane and carbon dioxide production with an open-circuit respirometry system that was equipped with respiratory chambers. The net energy (NE) and metabolizable energy (ME) requirements for maintenance and growth were calculated using the carbon and nitrogen balance method. The results revealed that the carbon (C) and nitrogen (N) excretions and energy losses at faeces and urine, as well as the output of methane and CO2, increased significantly with decreasing feed intake (P<0.01). The apparent digestibilities of C in the stages of non-pregnancy and early, middle and late lactation were 55.8–58.3%, 62.5–73.8%, 64.8– 71.3%, and 61.7–65.0%, respectively, and the apparent digestibilities of N were 45.2–51.3%, 73.7–82.7%, 72.8–80.5%, and 73.6–76.5%, respectively. The corresponding energy apparent digestibilities were 52.0–56.3%, 60.7–76.6%, 61.0–68.8%, and 61.4–67.7%, respectively. The ME/DE (digestible energy) values were 79.5–85.9%, 79.4–83.5%, 81.0%–85.3% and 78.6–82.9%, respectively. The maintenance requirements of NE, ME, and the efficiencies of ME utilisation for maintenance during the stages of non-pregnancy and early, middle and late lactation were 215.5, 253.1, 247.7, and 244.7 kJ kg–1 BW0.75 d, and 372.4, 327.1, 320.9, and 362.0 kJ kg–1 BW0.75 d, and 0.58, 0.77, 0.77, and 0.68, respectively. The ME requirement for the growth of non-pregnant ewes was 31.3 MJ kg–1 BW gain.

Northern corn leaf blight (NCLB), caused by the heterothallic ascomycete fungus Setosphaeria turcica, is a destructive foliar disease of maize and represents a serious threat to maize production worldwide. A comparative proteomic study was conducted to explore the molecular mechanisms underlying the defense responses of the maize resistant line A619 Ht2 to S. turcica race 13. Leaf proteins were extracted from mock and S. turcica-infected leaves after inoculated for 72 h and analyzed for differentially expressed proteins using two-dimensional electrophoresis and mass spectrometry identification. 137 proteins showed reproducible differences in abundance by more than 2-fold at least, including 50 up-regulated proteins and 87 down-regulated proteins. 48 protein spots were successfully identified by MS analysis, which included 10 unique, 6 up-regulated, 20 down-regulated and 12 disappeared protein spots. These identified proteins were classified into 9 functional groups and involved in multiple functions, particularly in energy metabolism (46%), protein destination and storage (12%), and disease defense (18%). Some defense-related proteins were upregulated such as β-glucosidase, SOD, polyamines oxidase, HSC 70 and PPIases; while the expressions of photosynthesis- and metabolism-related proteins were down-regulated, by inoculation with S. turcica. The results indicated that a complex regulatory network was functioned in interaction between the resistant line A619 Ht2 and S. turcica. The resistance processes of A619 Ht2 mainly resided on directly releasing defense proteins, modulation of primary metabolism, affecting photosyntesis and carbohydrate metabolism.