Long-term adaptation of sheep to low protein roughage diets: effects of water deprivation and urea supplementation in the drinking water

Abstract

Nine rams were fed low protein roughage diets in three groups: daily watering, and intermittent watering every 3 days with and without urea supplements in the drinking water. The experiment lasted 63 days to investigate possible long-term adaptive responses. Live body weights were recorded every 2 weeks, and urine was collected for 3 consecutive days every 2 weeks. The experiment ended with a 10-day rehydration period. Daily dry matter intake was not affected by water deprivation or urea supplementation, and the amounts offered were apparently insufficient for maintenance in all groups. Nitrogen intake was significantly greater in the urea-supplemented group. All groups showed a loss of nitrogen in urine at the beginning of the experiment, 136 to 157% of total nitrogen intake. However, rapid adaptation was observed and after one month urinary nitrogen excretion represented 57 to 75% of intake. The urea-supplemented group constantly excreted more nitrogen, but the trend of adaptation was similar in all three groups. All sheep lost weight which amounted to 2·1, 2·1 and 4·1% of their initial weight in the control and water-deprived with and without urea supplementation, respectively. On rehydration, the latter two groups restored or slightly exceeded their initial weight.