EFFECT OF SEASONAL CHANGES AND TYPE OF ROUGHAGE ON: I- GROWTH PERFORMANCE, METABOLIC ACTIVITY AND CARCASS CHARACTERISTICS OF CROSSBREED LAMBS

Eighteen growing crossbreed lambs (23.2±0.91 kg average live body weight; 5 month old) were used to investigate growth performance, feed efficiency, metabolic aspects and carcass characteristics of lambs as affected by type of roughage under different seasons. Lambs were randomly distributed to three experimental groups (six for each). First group was fed starter concentrate feed mixture (CFM) and berseem hay (R1;as a control). Whereas, other groups were fed CFM plus berseem silage supplemented with either 5% ground yellow corn (BSC; R2) or lactic acid bacteria and yeast mixture (BSB; R3) during ensiling process. The local environmental temperature was recorded monthly. Daily weight gain, relative growth rate, daily dry matter intake and feed conversion were recorded. Also, production and economic efficiency of lambs were calculated. The adjusted net energy of maintenance (NEm) and growth (NEg) were calculated according to thermal air temperature. Results showed that total gain and average daily gain of lambs fed R2 were higher than other groups with no significant differences, while feed conversion in R3 was better than other groups (7.771 vs. 9.425 and 8.497 for R3, R1 and R2, respectively) owing to the lowest total dry matter intake with R3.The NEm was slightly higher in R2 than other groups. Whereas, R3 was the lowest (P<0.01) value of NEg. Retained energy and production efficiency were higher (P<0.01) in R3 than other groups and followed by R2. Carcass characteristics of lambs did not differ significantly among groups. However, R2 showed better values of hot dressing%, L.D weight, DM and CP%. It can be concluded that, both ground yellow corn and biological supplements to ensiling process of berseem improved feed conversion and production efficiency of lambs. The best growth performance, profit and economic efficiency under the local thermal temperature was recorded in groups fed berseem silages, specially in R2, compared with control which fed berseem hay as a basal diet.