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。

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.

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