# Effect of N-Carbamylglutamate Supplementation in Late Pregnancy on Nutrient-Restricted Twin-Bearing Ewes on the Pre-Lambing Maternal Metabolome, Colostrum Quality and Lamb Birth Weight

## TL;DR

NCG supplementation in undernourished twin-bearing ewes improved colostrum quality but did not increase lamb birth weight or maternal body condition.

## Contribution

NCG is shown to enhance colostrum protein and IgG content in nutrient-restricted twin-bearing ewes, offering a potential alternative to arginine.

## Key findings

- NCG did not improve ewe body condition or lamb birth weight.
- NCG increased plasma urea and altered amino acid profiles in maternal blood.
- Colostrum from NCG-treated ewes had higher protein and IgG content.

## Abstract

Lamb mortality around birth, especially in twin lambs, is of major concern for producers. Under natural nutrient restriction, arginine, a conditionally essential amino acid for the fetus, is known to improve fetal growth and colostrum quality in restricted ewes. However, its use is limited in ruminants due to its high cost and degradation in the rumen. N-carbamylglutamate (NCG) can stimulate the body’s own arginine production and may serve as an alternative. This study evaluated the effects of NCG supplementation during late pregnancy in undernourished twin-bearing ewes. Ewes received 60 mg/kg body weight of NCG daily from day 100 of gestation until lambing. Compared to unsupplemented controls, NCG did not improve ewe body condition, placental traits, or lamb birth weight. However, NCG supplementation resulted in changes in maternal blood metabolites, including higher plasma urea and altered amino acid profiles. Importantly, colostrum from NCG-treated ewes had significantly higher protein and IgG content. While NCG did not reverse the negative effects of undernutrition on fetal growth, it did improve colostrum quality and immunoglobulin content, which may enhance immunity in lambs and contribute to reducing lamb mortality after birth, a key constraint in extensive sheep production systems.

Arginine supplementation improves fetal growth and colostrum composition in nutrient-restricted ewes, but its high cost and ruminal degradation limit its practical use. N-carbamylglutamate (NCG), which stimulates endogenous arginine synthesis, and is not degraded in rumen, may be a viable alternative. This study evaluated the effects of oral NCG supplementation (60 mg/kg BW/day from day 100 of gestation to term) on undernourished twin-bearing ewes (~50% NRC requirements; NCG n = 20, Control n = 21). Maternal body weight (BW), body condition score (BCS), blood metabolites, placental traits, lamb body measurements, and colostrum composition were assessed. BW increased and BCS decreased over time (p < 0.0001), with no treatment effect. Lamb and placental traits were similar between groups. NCG supplementation resulted in a 15% higher plasma urea concentration (p < 0.03) and altered 21 serum metabolites, with reduced levels of valine, leucine, isoleucine, glycine, proline, and phosphate, and increased serine, ethanolamine, urea, and 2-hydroxyhexanoic acid concentration compared to CON animals. Colostrum from NCG ewes had a 21% higher protein (p < 0.04) and a 16% higher IgG content (p < 0.03) compared to CON animals. Although NCG did not mitigate the negative effects of maternal undernutrition on fetal traits, it influenced maternal metabolism and improved colostrum quality.