EFFECT OF GRAZING TIME ON DIGESTION AND ENERGY UTILIZATION OF GOAT DURING LACTATION PERIOD IN HALAIB-SHALATEEN PASTURES

Thirty lactating Balady goats were employed in a 90-day experiment to study the effect of grazing time on pasture intake, digestion, energy expenditure (EE) and energy balance (EB) throughout early and late lactation periods in Halaib - Shalateen pastures. To achieve this objective, female goats were divided into three treatments, 10 per each; the first treatment (T1) was in-door without grazing and given 1% of live body weight (LBW) concentrates feed mixture (CFM) plus berseem hay ad libitum. The second (T2) and third (T3) treatments were allowed to graze daily on Panicum turgidum as a basal range plant for 4, 8 hours, respectively and given 1% of LBW CFM. The results could be summarized as follows: The forage intake (g/ kg BW^0.75) by goats was significantly (P≤0.01) higher in early lactation than that in late lactation period. Goats that grazed for 8 hours daily showed higher (P≤0.01) forage intake than those grazed for 4 hours daily, while, goats fed on berseem hay ad libitum without grazing had higher (P≤0.01) value of roughage intake compared to the two grazed groups whether in the early or late lactation period. Similar findings were observed for nutrients intakes (OM, CP and NDF). Grazed goats for 4 hr and 8 hr had higher (P≤0.01) values of DM, OM, CP, CF, NDF and digested energy (DE) than these in zero-grazing group whether in the early lactation or in the late lactation period. Goats grazed for 8 hr daily had higher (P≤0.01) values of digestible and metabolizable energy intake than those in 4 hr and zero-grazing groups whether in the early or late lactation periods. Grazed goats for 4 hr and 8 hr had higher (P≤0.01) values of heart rate (HR) and energy expenditure (EE) than that in zero-grazing group. The energy balance (EB), when expressed as kJ/kg BW^0.75/day, was positive and greater (P≤0.01) for zero-grazing goats than those in grazed groups. Also, 8 hr-grazing group had greater (P≤0.01) value of EB than that 4 hr-grazing group, but it was negative for the two groups. It could be concluded that, under arid-area condition, in Halaib – Shalateen pastures, grazing of goats for 8 hours daily showed better nutritional performance represented by an increase in the pasture intake, digestion, reduction energy expenditure (EE) and therefore, energy balance (EB) was better than that grazing for 4 hours during early and late lactation periods.