| A comparative slaughter trial was conducted to estimate the net macromineral and trace elementrequirements for maintenance and growth of Dorper x Hu lambs; the digestion trial, respirometry trial, and carbon and nitrogen balance trial was conducted to determine energy and protein requirements for maintenance and the effect of feed intake level on energy metabolism, carbon-nitrogen balance, and methane emission of Hu sheep during pregnancy; an ovine intrauterine growth restriction (IUGR) model was established to test the hypothesis that dietary N-carbamylglutamate (NCG) and rumen-protected L-arginine(RP-Arg) supplementation are effective in ameliorating fetal growth restriction in undernourished ewes, and to determine how dietary NCG and RP-Arg supplementation in nutrient restricted pregnant Hu sheep would affect 1) maternal endocrine status; 2) maternal,fetal, and placental anti-oxidation capability 3) placental development. These results for the nutritional requirements may help to formulate more balanced diets for Dorper x Hu lambs in the growing period and Hu ewes during pregnancy. These results also indicate that dietary NCG and RP-Arg supplementation to underfed ewes could influence maternal endocrine status, improve the maternal-fetal-placental anti-oxidation capability and promote fetal and placental development during early to late gestation.1. The net macro mineral requirements for maintenance and growth of Dorper x Hu lambsA comparative slaughter trial was conducted to estimate the net macro mineral requirements for maintenance and growth of Dorper x Hu male and female lambs.Thirty-five lambs from each sex with an initial body weight (BW) of 19.2±0.36 kg (in the early growing period) or 33.45±0.64 kg (in the late growing period), respectively,were used. Seven lambs from each sex were randomly chosen and slaughtered at 20kg (in the early growing period) or 35kg (in the late growing period) BW as the baseline group for measuring initial body composition. Another seven lambs from each sex were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 28 kg (in the early growing period) or 42 kg (in the late growing period) BW. For each sex,the remaining lambs (n = 21) were allocated randomly on d 0 to 3 treatment intake levels(treatments were ad libitum or restricted to 70 or 40% of the ad libitum intake) within 7 slaughter groups. A slaughter group contained 1 lamb from each treatment, and lambs were slaughtered when the ad libitum treatment lamb reached approximately 35 kg (in the early growing period) or 50 kg (in the late growing period) BW. Empty bodies of the lambs (head+ feet, hide, internal organs + blood, and carcass) were weighed, ground, mixed, and subsampled for chemical analyses. In the early growing period, the net macromineral requirements for maintenance were 24.01 mg Ca, 11.70 mg P, 3.20 mg Na, 6.60 mg K, and 1.20 mg Mg/kg of empty BW (EBW) for males. The net macromineral requirements for maintenance were 22.21 mg Ca, 11.65 mg P, 3.41 mg Na, 6.92 mg K, and 1.23 mg Mg/kg EBW for females. The daily net requirements for growth ranged from 11.55 to 11.41 g Ca,5.82 to 5.77 g P, 1.47 to 1.69 g K, 0.42 to 0.44 g Mg, and 0.98 to 0.88 g Na /kg of EBW gain (EBWG) for males. The daily net requirements for growth ranged from 11.93 to 11.68 g Ca, 6.12 to 5.71 g P, 1.58 to 1.63 g K, 0.41 to 0.36 g Mg, and 1.34 to 1.24 g Na /kg of EBWG for females; In the late growing period, the net macromineral requirements for maintenance were 27.03 mg Ca, 12.53 mg P, 3.72 mg Na, 7.10 mg K, and 1.42 mg Mg/kg of empty BW (EBW) for males. The net macromineral requirements for maintenance were 20.20 mg Ca, 13.50 mg P, 3.80 mg Na, 7.91 mg K, and 1.10 mg Mg/kg EBW for females.The daily net requirements for growth ranged from 11.12 to 11.43 g Ca, 5.82 to 5.93 g P,1.71 to 1.91 g K, 0.46 to 0.48 g Mg, and 0.96 to 0.92 g Na /kg of EBW gain (EBWG) for males. The daily net requirements for growth ranged from 11.79 to 12.06 g Ca, 6.04 to 6.16 g P, 1.66 to 1.74 g K, 0.40 to 0.42 g Mg, and 0.98 to 0.95 g Na /kg of EBWG for females.These results for the nutritional requirements of macro-minerals may help to formulate more balanced diets for Dorper x Hu lambs in the growth phase of 20 to 50 kg BW.2. The net trace element requirements for maintenance and growth of Dorper x Hu lambsA comparative slaughter trial was conducted to estimate the net trace element requirements for maintenance and growth of Dorper × Hu male and female lambs. The design was in accordance with the experiment 1. In the early growing period, for males and females, the daily net trace element requirements for maintenance were 356.1 and 164.1 Fe,4.3 and 3.4 Mn, 42.0 and 29.8 Cu, and 83.5 and 102.0 Zn ?g/kg EBW, respectively. Net requirements for growth decreased from 65.67 to 57.27 Fe, 0.35 to 0.25 Mn, and 3.45 to 2.82 Cu and increased from 26.36 to 26.65 Zn mg/kg EBW gain (EBWG) for males. Net requirements for growth decreased from 30.66 to 22.14 Fe, 0.43 to 0.32 Mn, 2.86 to 2.18 Cu, and 27.71 to 25.83 Zn mg/kg EBWG for females; In the late growing period, for males and females, the daily net trace element requirements for maintenance were 429.3 and 310.4 Fe, 5.1 and 4.4 Mn, 48.8 and 35.7 Cu, and 94.6 and 110.3 Zn ?g/kg EBW,respectively. Net requirements for growth decreased from 70.41 to 68.40 Fe and 4.31 to 4.15 mg Cu, and increased from 0.86-0.93 Mn and 33.46 to 35.20 Zn mg/kg EBW gain(EBWG) for males. Net requirements for growth decreased from 41.02 to 37.05 Fe,0.52-0.49 Mn, 3.39 to 3.10 Cu, and increased from 34.21 to 35.80 Zn mg/kg EBWG for females. 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.3. Energy and protein requirements for maintenance of Hu sheep during pregnancyThis study aimed to determine the effect of stage and level of feed intake on energy metabolism, carbon-nitrogen (C-N) balance, and methane emission to determine energy and protein requirements for maintenance during pregnancy using the method of C-N balance. Twenty-one ewes carrying twin fetuses were randomly divided into three groups of seven ewes each in the digestion and respirometry trialat d 40, 100, and 130 of gestation,respectively. Three groups were fed a mixed diet (Diet 1 was fed in the early gestation; Diet 2 was fed in the late gestation) either for ad libitum intake,70% or 50 % of the ad libitum intake for the duration of their gestation period. The results showed that the DMI (kg/d)increased (P < 0.05) from d 40 to 100 of gestation but then declined (P < 0.05) to d 130 of gestation. Methane energy, DE, MEI, DE/GE, ME/GE, and ME/DE were increased (P <0.05) as feeding levels increased at each stage of gestation. The methane emission rate(CH4 energy/GE) was decreased as feeding levels increased, and the CH4 energy/GE was greatest at d 100 of gestation (P < 0.05). The apparent digestibility of C and N were increased as feeding levels decreased at each stage of gestation. Apparent C digestibility was increased (P < 0.001) as days of gestation increased. Apparent N digestibility was greater (P < 0.001) at d 100 than d 40 and 130 of gestation. The methane emission (L/kg of DMI and L/kg of NDFI) was decreased as feeding levels increased at each stage of gestation (P< 0.01), and increased from d 40 to d 100 of gestation but then decreased to d 130 of gestation (P< 0.001). The CO2 to CH4 ratio was higher in 70% group than in AL and 50% groups at each stage of gestation, except for d 130 of gestation (P< 0.01), and decreased from d 40 to d 100 of gestation but then increased to d 130 of gestation (P<0.001). The daily NEm were 295.80, 310.09, and 323.59 kJ/kg0.75 of BW with a partial efficiency of ME utilization for maintenance of 0.664, 0.644, and 0.620 at d 40,100, and 130 of gestation, respectively. The daily net protein requirements for maintenance were 1.99, 2.35, and 2.99 g/kg0 75 of BW at d 40, 100, and 130 of gestation, respectively. These results for the nutritional requirements of the net energy and protein may help to formulate more balanced diets for Hu sheep during pregnancy.4. Dietary N-carbamylglutamate and rumen-protected L-arginine supplementation ameliorate fetal growth restriction in undernourished ewesThis study was conducted with an IUGR model to test the hypothesis that dietary NCG and 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% 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 (P< 0.05) in nutrient-restricted ewes compared with adequately fed ewes. Maternal RP-Arg or NCG supplementation did not alter (P = 0.26) maternal BW in nutrient restricted ewes. Weights of most fetal organs were increased (P<0.05) in RP-Arg-treated and NCG-treated underfed ewes compared with 50% NRC-fed ewes.Supplementation of RP-Arg or NCG reduced (P<0.05) concentrations of ?-hydroxybutyrate,triglycerides,and ammonia in serum of underfed ewes but had no effect on concentrations of lactate and growth hormone.Maternal RP-Arg or NCG supplementationmarkedly improved (P<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 fluidswithin 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.5. N-carbamylglutamate or L-arginine improved maternal and placental development in underfed ewesThe objectives were to determine how dietary NCG and RP-Arg supplementation in nutrient restricted pregnant Hu sheep would affect 1) maternal endocrine status; 2) maternal,fetal, and placental anti-oxidation capability 3) placental development. From d 35 to 110 of gestation, thirty-two Hu ewes carrying twin fetuses were allocated at random into 4 groups:100% of NRC-recommended nutrient requirements, 50% of NRC-recommendations, 50%of NRC recommendations supplemented with 20 g/d RP-Arg, and 50% of NRC recommendations supplemented with 5 g/d NCG product. The results showed that in maternal and fetal plasma and placentomes, the activities of total antioxidant capacity and superoxide dismutase were increased (P<0.05), but the activity of glutathione peroxidase and the concentration of maleic dialdehyde were decreased (P<0.05) in both NCG and RP-Arg-treated underfed ewes.The mRNA expression of vascular endothelial growth factor and Fms like tyrosine kinase 1 was increased (P < 0.05) in 50% NRC ewes than in 100%NRC ewes, and had no effect (P>0.05) in both NCG and RP-Arg-treated underfed ewes;A supplement of RP-Arg and NCG reduced (P< 0.05) concentrations of progesterone, cortisol,and estradiol 17?,had no effect on T4/T3, and improved (P< 0.05) concentrations of leptin,insulin-like growth factorl, triiodothyronine (T3),and Thyroxine (T4) in serum from underfed ewes. These results indicate that dietary NCG and RP-Arg supplementation to underfed ewes could influence maternal endocrine status, improve the maternal-fetal-placental anti-oxidation capability and promote fetal and placental development during early to late gestation. |
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