Impact of protein supply on the productive performance of growing lambs drinking natural saline water and fed low-quality forage under semi-arid conditions.

Consuming saline water causes animals salinity stress, which leads to many adapting metabolic changes that could negatively affect its performance and the quality of the derived products. Therefore, this study aimed to evaluate the impact of increasing diet protein level on the productive performance of growing lambs drinking natural saline water in Egyptian semi-arid region. Twenty-four growing Barki lambs (4-5 months old) with an initial body weight of 20.7 ± 0.25 kg were randomly distributed into four similar groups for 150 days. Two diets were formulated: low protein and high protein levels (concentrate feed mixture containing 14% and 20% crude protein (CP) on dry matter basis, respectively). Within each level of CP, natural saline water was represented by low saline (LS) and high saline (HS) water, containing 658 and 2100 mg/L of total dissolved solids, respectively. Results showed that the HS water increased (p = 0.02) water intake by about 18% and had adverse effect (p < 0.001) on dry matter intake, nutrient digestibility, and growth performance. The ruminal pH values, total volatile fatty acids, and ammonia-N concentrations were not affected by drinking the HS water. However, the protein supplementation enhanced the HS lambs' nutrients digestion and showed greater growth performance. The HS water decreased (p < 0.001) the serum concentrations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and increased (p = 0.03) the urea-N by about 9%. The protein supplementation amended the serum ALT and AST concentrations of HS lambs. It is concluded that the dietary protein supply was affective sustainable management strategy against the deleterious effect of drinking high saline water on growing lambs.