Effects of N-carbamylglutamic on blood biochemistry and reproductive performance of pregnant female Hu sheep

The aim of this study was to analyze the effects of dietary supplementation with different levels of N-carbamylglutamate (NCG) on the blood biochemistry, reproductive hormones, and lambing traits of first-bearing Hu sheep ewes during pregnancy, and to lay a foundation for improving the reproductive efficiency of Hu sheep ewes. A total of 300 healthy first-bearing ewes with similar age (8 months) and body weight (31.81 ± 1.20 kg) were randomly divided into four groups with 75 ewes in each group. Ewes in the control group were fed a basal diet, while those in the experimental group were fed a basal diet supplemented with 1.0 (Group I), 1.5 (Group II), and 2.0 g (Group III) NCG per day. A breeding method was used in this study. The rams were released into the female pen for 20 days. One month after the rams were out of the pen, 40 pregnant ewes in each group were selected to continue the experiment through B-ultrasound detection. The trial was conducted one month before the breeding of the ewes until the completion of lambing of all ewes. Ewe blood was collected during the first (28 days after the end of male breeding) and second trimesters (15 days before the due date), and the effects of NCG on the reproductive performance of the ewes were analyzed by measuring their blood biochemistry, reproductive hormones, and lambing characteristics. The results were as follows: 1) During the early gestational period, plasma progesterone levels of ewes in Group III were significantly higher than those of ewes in the control group (P < 0.01). The plasma estradiol level of ewes in Group I was significantly higher than that of ewes in the control group (P < 0.01). The plasma arginine level of ewes in Group I was also significantly higher than that of ewes in the control group (P < 0.05), whereas the plasma total nitric oxide synthase level of ewes in Group III was significantly higher than that of ewes in the control group (P < 0.05). Furthermore, plasma endothelial nitric oxide synthase levels of ewes in Group III were significantly higher than those of ewes in the control group (P < 0.05). 2) In the late gestation period, the plasma glucose level of ewes in Group II was significantly higher than that of ewes in the control group (P < 0.01), whereas the plasma prolactin (PRL) level of ewes in Group I was significantly higher than that of ewes in the control group (P < 0.05). 3) Compared with the control group, the pregnancy rate, the number of lambs at birth, and the number of live lambs at birth for the first-bearing female Hu sheep in the experimental groups supplemented with NCG were increased to varying degrees (P > 0.05) and were the highest in the the ewes in Group II, with increases of 5.13%, 0.15, and 0.18, respectively. In summary, dietary supplementation of NCG can increase the number of pregnant ewes, litter lambs, and litter live lambs, increase the plasma arginine and NO contents, and improve the reproductive performance of first-bearing female Hu sheep. The appropriate dose was determined to be 1.5 g NCG per sheep per day.