中国拥有世界上最大的肉羊存栏量和羊肉生产量，是名副其实的养羊越级大国。然而长期以来关于我国肉羊营养需要量的研究缺乏系统性，阻碍了肉用绵羊营养需要量参数的建立和相关标准的完善。我国科技部和财政部于2008年成立了国家现代肉羊产业技术体系为开展肉用绵羊的营养需要量研究提供了技术支持和财政支撑。基于此，本文综述了我国肉用绵羊营养需要量研究的历史发展情况，总结了肉用绵羊营养需要量（包括能量、蛋白质、矿物元素等）的最新研究进展，并重点阐述了中国肉用绵羊营养需要量的未来研究方向。

本研究旨在探讨日粮直链/支链淀粉比例对中国秦川牛生长性能、瘤胃发酵和血液参数、胴体特征和大理石花纹评分、肌肉脂肪酸和糖异生途径相关基因表达差异的影响。试验采用单因素随机设计，将45头肉牛随机分为3组。试验动物分别饲喂普通玉米添加日粮(对照组；n=15；中等直链/支链淀粉比=0.47)、蜡质玉米淀粉添加日粮(WS；n=15；低直链/支链淀粉比=0.23)或豌豆淀粉添加日粮(PS；n=15；高直链/支链淀粉比=0.60)，共饲喂90天。全混合日粮每日饲喂量至少按肉牛体重的2.1%供给，分成2次饲喂。每隔45天称重1次，并分别采集血液和瘤胃液样品。试验结束后，每组选取接近平均体重的6头健康肉牛，颈静脉放血屠宰，并采集背最长肌样品进行肉质测定。试验数据采用SAS9.3统计软件中的单因素方差分析，并采用LSD法进行多重比较。与PS组相比，在0～45天，对照组和WS组的平均日增重(ADG)和饲料转化率均提高(P<0.05)。然而，在46～90天，PS组的饲料转化率比对照组和WS组更高(P<0.05)。在试验全期，对照组和WS组的ADG比PS组有更高的趋势(0.05<P<0.1)。与PS组相比，WS组血清胰岛素浓度在第45天时显著升高(P<0.05)，而在第90天时无明显差异(P>0.05)。与对照组和WS组相比，PS组血清超氧化物歧化酶和总抗氧化能力在第45天时显著升高(P<0.05)，而在第90天时无明显差异(P>0.05)。与对照组相比，WS组和PS组的瘤胃微生物蛋白(MCP)含量在第1天时显著升高(P<0.05)，而在第45天时对照组和WS组的MCP含量比PS组更高(P<0.05)，在第90天时3组间无明显差异(P>0.05)。与PS组相比，对照组和WS组的背膘厚度显著升高(P<0.05)，而在大理石花纹评分和肝脏中糖异生相关基因表达量上3组间无显著差异(P>0.05)。3组间背最长肌(LT)的常规成分和理化特性上也无显著差异(P>0.05)。综上所述，低或中等直链/支链淀粉比的日粮会增加背膘厚度，并有改善ADG的趋势，但对秦川牛其它胴体性状、肌内脂肪和糖异生相关基因表达量上无影响。创新性：1) 在育肥期的秦川公牛上进行不同直链/支链淀粉比日粮饲喂试验，比较不同淀粉原料的有效利用率；2) 通过生长性能、血液和瘤胃发酵参数、大理石纹评分以及糖异生关联基因表达量的综合比较，从饲料淀粉中直支链比例的角度观察了育肥期肉牛糖代谢和肌内脂肪生成量的变化。

Calves are the reserve forces for dairy cattle.  Scientific rearing strategy of calves is the basis of efficient cattle breeding.  However, many problems exist in current rearing systems of calves and restrict the sustainable development of dairy cattle in China.  The absence of basic research is the most highlighted problem among them.  Recent researches on growth performance, nutrient digestibility, blood biochemical indices and rumen development in calves were summarized in this paper.  Additionally, the optimal levels of energy and protein in milk replacer and starter diets for calves were indicated, and limiting amino acids for calves fed different diets were discussed.  A variety of additives, such as acidifiers, probiotics and polysaccharides, are regarded as promising alternatives to antibiotics to reduce disease in calves.  Dietary supplementations of these additives have positive effects on growth and health of calves.  However, studies on the nutrition of vitamins and minerals in calves have been seldom done, and deserve our further researches.  To sum up, the postnatal period is one of the most critical “windows” for rumen manipulation and epigenetic regulation.  Any changes from environments, especially early nutrition, may produce long-term effects on growth, health and milk yields in adult cattle.

The importance of nutrient provisions and weaning methods for calves has been well established over the past few years, while as increasing interest has focused on contribution of animal behavior and their overall performance in production regimes.  The present study investigated the effects of feeding methods and space allowance on growth performance, individual and social behaviors in Holstein calves.  Twenty-four Chinese Holstein male and female calves were allocated to either an individual or group of 6 and fed either with a bucket or a teat.  Milk replacer, calf starter, and Chinese wildrye were offered during the experiment.  A fecal index used in the present study was defined as the total fecal scores/total number of calves in each treatment.  The results showed that there was no significant difference among the 4 treatments in terms of feed intake, body weight, average daily gain, and fecal index.  For the feeding behaviors, the ingesting milk time and ingesting milk rate were significantly affected by space allowance, while the feeding methods showed a significant influence on the bunting behavior of the calves.  There was no significant difference among the 4 treatments in terms of licking fixtures, self-grooming, and lying down behaviors, irrespective of the feeding method or space allowance.  However, sucking an empty bucket or the teat was significantly affected by the feeding method.  Several selected group behaviors were examined in the present study, and similar values for sniffing the other calves, social grooming, and cross-sucking behaviors were observed.  Overall, the present study demonstrated that different feeding methods and space allowances had a significant effect on the feeding behavior of calves, while the feed intake, growth performance, health condition, individual and group social behaviors were not significantly influenced.  Furthermore, under intensified production systems, Holstein calves raised in a group may obtain a similar production performance, thus reducing management input and profitability compared with those kept individually.  However, there may be competition during the feeding period.

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.

A comparative slaughter trial was conducted to determine the net mineral requirements for maintenance and growth of Dorper crossbred female lambs raised from 20 to 35 kg of body weight (BW). Thirty-five Dorper×thin-tailed Han crossbred female lambs of (20.3±1.14) kg BW were used: 7 lambs were randomly chosen and slaughtered at the beginning of the experiment as the baseline group for measuring the initial body composition; another 7 lambs were randomly chosen and offered a pelleted mixed diet ad libitum and slaughtered at (27.0±0.73) kg BW; the remaining 21 lambs were randomly divided into 3 groups of 7 animals each and subjected to the same diet either ad libitum or at 70 or 40% of ad libitum intake. The 21 lambs were fed in 7 slaughter groups, with each group consisting of one lamb from each treatment (ad libitum, 70 or 40% of ad libitum intake). The 3 groups were slaughtered when the sheep fed ad libitum attained (33.8±0.52) kg of BW. The body composition of five minerals (Ca, P, Na, K, and Mg) was determined. The net mineral requirements for maintenance were 35.01, 25.18, 9.30, 31.35, and 2.03 mg kg–1 empty BW (EBW) for Ca, P, Na, K, and Mg, respectively, and the net growth requirement per kg of EBW gain ranged from 9.73 to 8.87 g of Ca, 5.83 to 5.27 g of P, 1.73 to 1.63 g of Na, 3.73 to 4.08 g of K, and 0.26 to 0.25 g of Mg for Dorper crossbred lambs in China, respectively. The estimates of mineral requirements with Dorper crossbred lambs in the current study were not consistent with the recommendations from previous studies.

This study aimed to investigate the effects of dietary supplementation of yeast β-glucan on the nutrient digestibility and serum profiles in pre-ruminant Holstein calves. Forty-two neonatal Holstein calves ((39.6±4.2) kg) were randomly allotted to six groups, and each was offered one of the following diets: a basal diet (control) or the basal diet supplemented with 25, 50, 75, 100 or 200 mg of yeast β-glucan kg–1 feed (dry matter basis). The basal diet consisted of a milk replacer and a starter feed. The trial lasted for 56 d. Two digestibility trials were conducted from d 14 to 20 and from d 42 to 48. Blood samples were collected on d 0, 14, 28 and 42 for serum profile analyses. On d 56, three calves from each group were slaughtered, and intestinal samples were collected to assess the villous height, crypt depth and mucosal thickness. Although feed intake was not affected by dietary treatment (P>0.05), the average daily gain (ADG) and gain-to-feed ratios were higher (P<0.05) for the calves fed 75 mg of yeast β-glucan kg–1 feed than those in the other groups. The supplementation of yeast β-glucan at 75 mg kg–1 feed increased the apparent digestibility of dry matter (DM), crude protein (CP), ether extract (EE), and phosphorus (P) (P<0.05) and the ratio of intestinal villous height to crypt depth (V/C) (P<0.05) when compared with the control group. No effects of yeast β-glucan on the serum concentrations of total protein (TP), albumin (ALB), serum urea nitrogen (SUN) and glucose (GLU) were observed (P>0.05). Compared with the control group, supplementation of yeast β-glucan decreased (P<0.05) the serum concentrations of triglycerides (TG) and total cholesterol (TC). The serum concentration of immunoglobulin G (IgG) and immunoglobulin M (IgM) increased quadratically (P<0.05), whereas the serum concentration of immunoglobulin A (IgA) was unaffected by dietary treatments (P>0.05). The supplementation of yeast β-glucan stimulated the enzymatic activity of alkaline phosphatase (ALP) (P<0.05) compared with the control group. The lysozyme (LYZ) concentration increased quadratically (P<0.05) with increasing yeast β-glucan levels. The results suggested that dietary supplementation of yeast β-glucan at 75 mg kg–1 feed improved nutrient digestibility, enhanced immunity by increasing the immunoglobulin concentration and stimulating ALP, and exerted no adverse effects on metabolism in pre-ruminant calves.

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.

A comparative slaughter trial and a metabolism trial were conducted to determine the requirement of net energy (NE) and metabolizable energy (ME) by the crossbreed of German Mutton Merino×Inner Mongolia Merino for fattening from 35 to 50 kg of body weight (BW). 49 crossbred female lambs ((33.9±2.3) (SD) kg BW) of German Mutton Merino×Inner Mongolia Merino were used. 34 lambs were randomly chosen for comparative slaughter, which were offered an identical mixture diet (concentrate:roughage=55:45) at 100, 75 or 55% of ad libitum intake, whereas the remainders were used in the metabolism trial to evaluate the ME of the diet after methane production was measured by open-circuit respirometry. As feed intake decreased from 100 to 75 and 55% of ad libitum intake, the apparent digestibility of dry matter (DM) linearly increased (P=0.010) from 60.8 to 63.6 and 66.9%, respectively, and methane production decreased from 52.1 to 44.3 and 39.9 L d-1, respectively, but the ratio of methane energy to gross energy intake increased linearly (P=0.010) from 8.20 to 8.96 and 10.97%, respectively. Consequently, the ME values of the diet increased from 9.35 to 9.64 and 9.85 MJ kg-1 DM, respectively. The NE requirement for maintenance (NEm) was 255 kJ kg-1 BW0.75, and the ME requirement for maintenance (MEm) was 352 kJ kg-1 BW0.75, with a partial energy efficiency for maintenance (km) of 0.72. The NE requirement for growth (NEg) ranged from 1.26 to 4.66 MJ d-1 as average daily gains increased from 100 to 300 g d-1, with a partial energy efficiency for growth (kg) of 0.45. These results indicated that the NEg required by crossbred female lambs of German Mutton Merino×Inner Mongolia Merino was lower than the recommendation of the American or British nutritional system.

The development of mammary glands, endocrine hormone concentrations and the gene expression of related receptors were measured in ovariectomized virgin rats after adminstration of an estrogen-like plant extract, rutin. Thirty-two ovariectomized virgin Wistar rats were randomly assigned to 4 treatments with 8 animals each: gastric infusion of 2 mL normal saline per unovariectomized rat per day (Sham), gastric infusion of 2 mL normal saline per ovariectomized rat per day (Ova), gastric infusion of 60 mg rutin kg-1 body weight (BW) per ovariectomized rat per day (Ova+Rut), or intramuscular injection of 60 μg estradiol kg-1 BW per ovariectomized rat weekly (Ova+Est). Samples of blood and mammary glands were harvested to determine the levels of estrogen (E2), prolactin (PRL) and growth hormone (GH), and the gene expression of estrogen receptors (ER), prolactin receptors (PRLR) and growth hormone receptors (GHR) with radioimmunoassy (RIA) and RT-PCR technology, respectively. The E2 concentration in plasma and gland tissues from the rats of Ovx+Rut or Ovx+Est was higher than that of Ovx (P<0.05), but the plasma E2 concentration from the rats of Ovx+Rut was lower than that of Sham (P<0.05). The order of the PRL concentration in plasma and gland tissues was Ovx