Health and performance of Omani sheep fed salt-tolerant sorghum (Sorghum bicolor) forage or Rhodes grass (Chloris gayana)

Sorghum variety Super Dan was planted and irrigated with water containing three different concentrations of salt: 3, 6 and 9 dS/m. The sorghum fodder was termed low salinity sorghum (LSS), medium salinity sorghum (MSS) and high salinity sorghum (HSS). The sorghum was manually harvested, dried and chopped before feeding. Thirty-two, 3-month-old Omani male lambs were randomly distributed into four groups of eight lambs each. The first group was fed a control diet of Rhodes grass hay (RGH) plus a commercial concentrate. The other groups were given one of three sorghum hays irrigated with water containing one of the three different concentrations of salt plus the commercial concentrate. Daily feed intakes and weekly BW were determined throughout the experimental period of 11 weeks of which the first two were regarded as an adaptation period. A digestibility trial was carried out using 12 animals (3 sheep per diet) consisting of 10 days of adaptation and a subsequent 10 days collection period for faeces and urine. Blood samples were drawn three times during the experiment and analyzed for haematological and serum biochemistry levels. At the end of the trial the animals were slaughtered. The RGH had higher mineral content than sorghum forage grown under various levels of salinity. Animals fed sorghum-based diets did not show any signs of ill health. There were no differences (P > 0.05) in digestibility coefficients of acid detergent fibre, neutral detergent fibre, and ether extract between RGH, LSS, MSS and HSS diets. However, the LS diet had lower DM, Ca, CP, P and energy digestibilities but higher ash digestibility. There were no treatment effects on hay, concentrate or total feed intake; total body weight gain or gain per kg/body weight of experimental animals. Sheep fed the RGH, LSS, MSS and HSS diets had average daily body weight gains of 96, 84, 82 and 68 g/day, respectively. There was no diets effect on rumen condition except that RGH-fed animals had lower N-ammonia and butyric acid concentration. This study indicated that sorghum forage grown under high salinity levels may be used for feeding Omani sheep without adverse effects on health or performance.