Effects of water restriction after feeding during heat stress on nutrient digestibility, nitrogen balance, blood profile and characteristics in Corriedale ewes

• Water restriction for 2 and 3 h after feeding increased N retention in sheep.
• Water should be available to ewes less than 3 h after feeding.
• IgG levels were not affected by water restriction in sheep exposed to heat stress.
• Urine output (weight and volume) and fecal excretion decreased by water restriction.

This study was designed to determine the effect of water restriction after feeding on nutrient digestibility, N balance, blood profile and immunoglobulin G levels in heat stressed Corriedale ewes. Nine Corriedale ewes (average BW = 43 ± 6.5 kg) were individually fed diets based on maintenance requirements in metabolic crates. Sheep were assigned to three treatment groups according to a 3 × 3 Latin square design for 3 periods of 21 days duration each (9 sheep per treatment). Treatments were free access to water (FAW), 2 h water restriction (2hWR), and 3 h water restriction (3hWR) after feeding. No differences were found in body weight gain among all treatment groups (P<0.05). Measures of N balance (g/day) including digestible N, and retained N increased significantly whereas urinary and fecal N decreased significantly in 2hWR and 3hWR groups compared with FAW group (P<0.05). Digestibility of ether extract was not different between treatment groups (P>0.05). However, crude protein, crude fiber, organic matter, dry matter, neutral detergent fiber, acid detergent fiber, and non-fiber carbohydrate digestibilities were significantly higher in 2hWR group than the other treatment groups (P<0.05). Urine weight and volume were higher (P<0.05) in FAW than restricted groups, but there was no difference between 2hWR and 3hWR groups (P>0.05). No significant difference (P>0.05) was observed for serum protein, glucose, and urea N among the treatment groups. However, serum triglyceride was higher in 2hWR compared with other groups (P<0.05). Immunoglobulin G and blood hematology including red blood cells, white blood cells, hemoglobin, hematocrit, basophils, and eosinophils were not different among treatment groups (P>0.05). It is concluded that water restriction after feeding, especially 2 h water restriction in heat stressed ewes could improve N balance parameters and nutrient digestibilities without negative effects on immune function.