Effects of maternal nutrition and rumen-protected arginine supplementation on ewe performance and postnatal lamb growth and internal organ mass.

The hypothesis of this study was that arginine supplementation would overcome negative effects of restricted maternal feed intake during the last two-thirds of gestation on ewe performance and positively affect postnatal lamb growth and development. Multiparous, Rambouillet ewes (n = 32) were allocated to 3 treatments in a completely random design at 54 ± 3.9 d of gestation. Dietary treatments were 100% of nutrient requirements (control, CON), 60% of control (restricted, RES), or RES plus a rumen-protected arginine supplement dosed at 180 mg/kg BW once daily (RES-ARG). Ewes were penned individually in a temperature-controlled facility. At parturition, lambs were immediately removed from dams and reared independently. At day 54 ± 3 of age, lambs were stunned using captive bolt, exsanguinated, and organs were collected and weighed. Ewe BW from day 68 of gestation through parturition was greater (P ≤ 0.03) in CON compared with RES or RES-ARG. Similarly, ewe BCS from day 68 of gestation through parturition was greater (P ≤ 0.03) in CON than either RES or RES-ARG. Total ewe colostrum mass (g) at 3 h after parturition was greater (P ≤ 0.001) in CON than RES or RES-ARG. Lamb birth weight was greater (P = 0.04) in CON than RES ewes and tended (P = 0.10) to be greater in CON vs. RES-ARG. Lambs born to CON ewes had greater (P ≤ 0.03) BW than lambs from RES ewes at 7, 14, and 33 d postpartum. On day 19, lambs from CON and RES-ARG ewes both had greater (P ≤ 0.04) BW than lambs from RES ewes (12.0 and 11.5 vs. 10.3 ± 0.41 kg, respectively). Lambs born to CON and RES-ARG ewes had greater (P ≤ 0.04) ADG than lambs from RES ewes on day 19 (355.0 and 354.0 vs. 306.4 ± 15.77 g, respectively). Lambs from CON and RES-ARG ewes also had greater (P ≤ 0.02) girth circumference than lambs from RES ewes on day 19 (55.4 and 54.6 vs. 51.3 ± 0.97 cm, respectively). On day 54, lambs from RES-ARG ewes had greater (P = 0.003) curved crown rump length than lambs from RES ewes (99.8 vs. 93.9 ± 1.28 cm, respectively). Adrenal glands in lambs from CON dams had greater (P = 0.01) mass than adrenal glands in lambs from RES dams. Livers from lambs born to RES-ARG ewes weighed more (P = 0.05) than livers from lambs born to RES ewes. These results confirm our hypothesis that arginine supplementation during the last two-thirds of gestation can mitigate offspring, but not maternal negative consequences associated with restricted maternal nutrition.