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.

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Abstract Sixty nonpregnant, nulliparous Rambouillet ewes (51 ± 1.4 kg initial body weight) were used in a completely randomized design to determine 1) if rumen-protected l-Arg (RP-ARG) supplementation would increase serum concentrations of amino acids resulting from Arg supplementation and metabolism, and decrease serum concentrations of amino acids that compete with Arg for transporters, 2) if RP-ARG supplementation would alter carotid artery hemodynamics, and 3) the most effective oral dose of RP-ARG to positively increase both circulating amino acids and improve peripheral tissue blood perfusion as measured by carotid hemodynamics. Ewes were penned individually in a temperature-controlled facility. Ewes were randomly assigned to one of four treatments: a control group that received no supplemental Arg (CON; 50 g of finely ground corn, only), or Arg-supplemented groups that received 90 (90), 180 (180), or 360 (360) mg RP-ARG·kg BW−1·d−1 mixed in 50 g of finely ground corn. Supplements were administered once daily for 14 d and fully consumed before the delivery of a total pelleted diet at 0630 and 1830 hours daily. Baseline and final blood samples were collected at days 0 (before treatment initiation) and 15, respectively. Doppler ultrasound was used to assess carotid arterial hemodynamics at 0600 hours on days 0 (before treatment initiation), 5, 8, 12, and 15. After 14 d of supplementation, ewes fed 180 had greater Arg (P = 0.05) and Orn (P = 0.05) and tended (P = 0.08) to have greater Asp in serum than ewes fed 90, and for these amino acids, ewes fed 180 were similar (P ≥ 0.16) compared with ewes fed 360. All supplemented ewes (90, 180, and 360) had a negative change (P = 0.02) from baseline when normalized to CON for the pulsatility and resistance indices, which indicate greater distal tissue blood perfusion and lower vascular resistance of blood flow, respectively. Additionally, there were quadratic responses for the pulsatility and resistance indices (P = 0.03 and 0.01, respectively) where ewes fed 180 had the greatest change from baseline when normalized to CON. Results indicate that Arg supplementation increased serum amino acid concentrations and improved peripheral tissue blood perfusion. The 180 mg·kg BW−1·d−1 RP-ARG dose was determined to be the optimal dose for nonpregnant, nulliparous Rambouillet ewes.

Multiparous Rambouillet ewes (n = 32) were allocated in a completely randomized design to determine if rumen-protected L-arginine (RP-Arg) supplementation during mid- and late gestation would 1) alter maternal carotid artery hemodynamics and 2) affect circulating amino acids associated with arginine metabolism in dams from day 54 of gestation to parturition and in their offspring from birth to 54 d of age. Ewes were assigned to one of three treatments from day 54 ± 3.9 to parturition: control (CON; 100% nutrient requirements), restricted (RES; 60% of CON), and RES plus 180 mg RP-Arg•kg BW-1•d1 (RES-ARG). Ewes were penned individually in a temperature-controlled facility. Carotid artery hemodynamics was measured via Doppler ultrasound at day 50 and 130 of gestation. Maternal serum was collected at day 54 and 138 of gestation and at parturition. At parturition, lambs were immediately removed from their dams and reared independently. Lamb serum samples were collected at birth and 1, 3, 7, 33, and 54 d of age. Pulsatility index was the only hemodynamic measurement altered by dietary treatment, where day 130 measurements were greater (P ≤ 0.04) for RES and RES-ARG compared with CON. The change in pulsatility index was greater (P < 0.01) for RES compared with CON but tended to be intermediate (P ≥ 0.12) for RES-ARG. Maternal serum Arg, Cit, and Asp at day 138 were greater (P < 0.01) for CON compared with RES and RES-ARG; serum Orn at day 138 was greater (P = 0.04) for CON compared with RES. Maternal serum Cit at parturition was greater (P ≤ 0.03) for CON and RES-ARG compared with RES. Offspring serum Arg was affected by a maternal treatment by day of age interaction (P = 0.03), where at day 3, CON and RES-ARG had greater (P ≤ 0.03) serum Arg concentrations than RES, and at day 54, RES-ARG was greater than (P = 0.002) CON and RES was intermediate and did not differ from (P ≥ 0.09) CON and RES-ARG. Offspring serum Orn and Cit were less (P ≤ 0.03) for RES and RES-ARG compared with CON. Results indicate that distal tissue blood perfusion decreased due to maternal RES, and RES-ARG was able to improve perfusion but not to the level of CON ewes. Further, maternal RP-Arg altered offspring Arg and related amino acid concentrations during the postnatal period.