Elisha Gootwine  - Department of Ruminant Science, Institute of Animal Science, The Volcani Center for Research and Development, Bet Dagan, Israel.

Alexander Rosov  - Department of Ruminant Science, Institute of Animal Science, The Volcani Center for Research and Development, Bet Dagan, Israel.

Tamir Alon  - Department of Ruminant Science, Institute of Animal Science, The Volcani Center for Research and Development, Bet Dagan, Israel.

Claire Stenhouse  - Department of Animal Science, Texas A&M University, College Station, Texas, U.S.A. 
Katherine M Halloran  - Department of Animal Science, Texas A&M University, College Station, Texas, U.S.A.

Guoyao Wu  - Department of Animal Science, Texas A&M University, College Station, Texas, U.S.A.

Fuller W Bazer  - Department of Animal Science, Texas A&M University, College Station, Texas, U.S.A.

This research determined effects of dietary supplementation with rumen protected arginine on metabolites and amino acids in maternal plasma and lamb survival rate at birth (LSRAB) in prolific Afec-Assaf ewes. The hypothesis was that rumen protected arginine, the precursor for nitric oxide and polyamines, would increase placental development and vascularity, utero-placental blood flow and nutrient transport, and reduce oxidative stress to increase LSRAB. Ewes were fed either their basal diet, basal diet with rumen protected arginine or basal diet with unprotected arginine (18g/head/d). The supplemental arginine was about 1% of the dry matter intake from d 40 or d 60 of gestation until parturition. Ninety-two of 98 ewes produced live lambs. Ewes fed protected arginine had greater (P=0.002) concentrations of arginine and other amino acids in plasma, whereas unprotected arginine did not affect concentrations of arginine, but decreased (P&0.05) concentrations of some amino acids. There was no effect of treatments on gestation length (144±2d), prolificacy (2.65 lambs born/ewe), LSRAB (0.80), body weight (88.8±10.8 kg) and body condition score (2.8±0.6) of ewes, or birth weight and crown-rump length of lambs. The GI was affected by sex of lamb (P=0.008), parity of ewe (P=0.002), litter size (P=0.0001) and lamb status (P=0.003). Of 229 lambs born, 32 were dead and 16 died before 5 mo of age, leaving 181 lambs with records on weights at birth and 5 mo of age. Interestingly, lambs born to ewes fed the unprotected and protected arginine weighed 3.6 kg less at postnatal d 150 than lambs from control ewes.