A comparative slaughter trial was conducted to estimate the trace element concentrations and distributions in the main body tissues and the net requirements for maintenance and growth of Dorper × Hu crossbred lambs. Thirty-five lambs of each gender (19.2 ± 0.36 kg initial BW) were used. Seven lambs of each gender were randomly chosen and slaughtered at approximately 20 kg BW as the baseline group for measuring initial body composition. Another 7 lambs of each gender were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at approximately 28 kg BW. The remaining 21 sheep of each gender were randomly divided into 3 groups with 7 sheep each and assigned to ad libitum or 40 or 70% of ad libitum intake of a pelleted mixed diet (42:58 concentrate:roughage, DM basis). The 3 groups of each gender were slaughtered when the sheep fed ad libitum reached approximately 35 kg BW. Empty body (head + feet, hide, viscera + blood, and carcass) trace element contents were determined after slaughter. The results showed that the trace elements were mainly distributed in viscera (blood included), except for Zn, which was mainly distributed in the muscle and bone tissues. The net requirements were calculated using the comparative slaughter technique. For males and females, the daily net trace element requirements for maintenance were 356.1 and 164.1 μg Fe, 4.3 and 3.4 μg Mn, 42.0 and 29.8 μg Cu, and 83.5 and 102.0 μg Zn per kilogram empty body weight (EBW), respectively. Net requirements for growth decreased from 65.67 to 57.27 mg Fe, 0.35 to 0.25 mg Mn, and 3.45 to 2.82 mg Cu and increased from 26.36 to 26.65 mg Zn per kilogram EBW gain (EBWG) for males. Net requirements for growth decreased from 30.66 to 22.14 mg Fe, 0.43 to 0.32 mg Mn, 2.86 to 2.18 mg Cu, and 27.71 to 25.83 mg Zn per kilogram EBWG for females from 20 to 35 kg BW. This study indicated that the net trace element requirements for Dorper × Hu crossbred lambs may be different from those of purebred or other genotypes, and more data are needed for sheep in general.

This study was conducted with an ovine intrauterine growth restriction (IUGR) model to test the hypothesis that dietary -carbamylglutamate (NCG) and rumen-protected -Arg (RP-Arg) supplementation are effective in ameliorating fetal growth restriction in undernourished ewes. Beginning on d 35 of gestation, ewes were fed a diet providing 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations (50% NRC), 50% of NRC recommendations supplemented with 20 g/d RP-Arg (providing 10 g/d of Arg), and 50% of NRC recommendations supplemented with 5 g/d NCG product (providing 2.5 g/d of NCG). On d 110, maternal, fetal, and placental tissues and fluids were collected and weighed. Ewe weights were lower ( < 0.05) in nutrient-restricted ewes compared with adequately fed ewes. Maternal RP-Arg or NCG supplementation did not alter ( = 0.26) maternal BW in nutrient-restricted ewes. Weights of most fetal organs were increased ( < 0.05) in RP-Arg-treated and NCG-treated underfed ewes compared with 50% NRC-fed ewes. Supplementation of RP-Arg or NCG reduced ( < 0.05) concentrations of β-hydroxybutyrate, triglycerides, and ammonia in serum of underfed ewes but had no effect on concentrations of lactate and GH. Maternal RP-Arg or NCG supplementation markedly improved ( < 0.05) concentrations of AA (particularly arginine-family AA and branched-chain AA) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids within nutrient-restricted ewes. These novel results indicate that dietary NCG and RP-Arg supplementation to underfed ewes ameliorated fetal growth restriction, at least in part, by increasing the availability of AA in the conceptus and provide support for its clinical use to ameliorate IUGR in humans and sheep industry production.

Ovarian steroid hormones regulate follicular growth and atresia. This study aims to determine whether key ovarian sterol-regulatory genes are differentially expressed in Hu sheep under different short-term nutritional regimens. Estrus was synchronized using intravaginal progestagen sponges. The ewes were assigned randomly to 3 groups. On d 6 to 12 of their estrous cycle, the control (CON) group received a maintenance diet (1.0×M), the supplemented (SUP) group received 1.5×M, and the restricted (R) group received 0.5×M. On d 7 to 12, blood samples were taken. The sheep were slaughtered at the end of the treatment, and their organs and ovaries were collected. The plasma concentrations of urea (P<0.01), total cholesterol (P<0.01), low-density lipoprotein cholesterol (P<0.01), NEFA (P<0.01), FSH (P<0.05), and estradiol (P<0.05) increased with decreasing dietary intake, whereas plasma triglyceride (P<0.01) and triiodothyronine (T3) concentrations decreased (P<0.05). The ewes in the R group had higher spleen weight and percentage of spleen to BW and lower liver and small intestine weights and percentage of liver/stomach to BW than the SUP group ewes (P<0.05). Nutritional restriction decreased the cytochrome p450 (CYP17A1) and estrogen receptor 1 (ESR1) mRNA expression (P<0.05) and increased the cytochrome p450 aromatase (CYP19A1) mRNA expression (P<0.05) in follicles>2.5 mm. Follicle size affected the mRNA expression of very low density lipoprotein receptor (VLDLR), estrogen receptor 2 (ESR2), FSH receptor (FSHR), CYP17A1, and CYP19A1 (P<0.05). In conclusion, we suggest that a potential mechanism by which short-term negative energy balance inhibits follicular growth may involve responses to disrupted reproductive hormone concentrations and influenced the intrafollicular expression of CYP17A1, CYP19A1, and ESR1. This result may be due to increased plasma urea and lipid concentrations.

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This research aimed to define the energy requirement of Dorper and Hu Hybrid F1 ewes 20 to 50 kg of body weight, furthermore to study energy requirement changes with age and evaluate the effect of age on energy requirement parameters. In comparative slaughter trial, thirty animals were divided into three dry matter intake treatments (ad libitum, n = 18; low restricted, n = 6; high restricted, n = 6), and were all slaughtered as baseline, intermediate, and final slaughter groups, to calculate body chemical components and energy retained. In digestibility trial, twelve ewes were housed in individual metabolic cages and randomly assigned to three feeding treatments in accordance with the design of a comparative slaughter trial, to evaluate dietary energetic values at different feed intake levels. The combined data indicated that, with increasing age, the net energy requirement for maintenance (NEm) decreased from 260.62±13.21 to 250.61±11.79 kJ/kg0.75 of shrunk body weight (SBW)/d, and metabolizable energy requirement for maintenance (MEm) decreased from 401.99±20.31 to 371.23±17.47 kJ/kg0.75 of SBW/d. Partial efficiency of ME utilization for maintenance (km, 0.65 vs 0.68) and growth (kg, 0.42 vs 0.41) did not differ (p>0.05) due to age; At the similar condition of average daily gain, net energy requirements for growth (NEg) and metabolizable energy requirements for growth (MEg) for ewes during late fattening period were 23% and 25% greater than corresponding values of ewes during early fattening period. In conclusion, the effect of age upon energy requirement parameters in the present study were similar in tendency with previous recommendations, values of energy requirement for growth (NEg and MEg) for Dorper and Hu crossbred female lambs ranged between the NRC (2007) recommendation for early and later maturating growing sheep.