Effect of Tail Docking at Birth on Energy Utilization as well as Protein and Lipid Deposition by Fat-tailed Najdi Lambs

Abstract

Kraidees, M.S., Al-Saiady, M.Y. and Abouheif, M.A. 1995. Effect of tail docking at birth on energy utilization as well as protein and lipid deposition by fat-tailed Najdi lambs. J. Appl. Anim. Res., 7: 81–90.

Fifty six fat-tailed Najdi lambs, comprising 28 males and females each, were identically reared from birth to near-market live weight (40 kg). Half the lambs were docked at birth. Six lambs per docking x sex treatment were slaughtered at 40 kg; the remaining 8 lambs/treatment were individually fed for 60 days and then slaughtered. Over the 60-days period, there was no docking effect on the daily protein deposition between docked and undocked lambs. Docked lambs deposited a lower (P<0.10) daily amount of lipid in carcass soft tissue and a greater (P<0.01) amount of lipid in viscera than that in undocked ones. The daily weight gain of protein deposited in carcass soft tissue, bone, viscera, hide and wool components was higher (P<0.01) in rams than ewe lambs. Daily lipid weight deposited in bone and hide was greater (P<0.01) in ram than ewes, whereas ewes deposited more (P<0.01) lipid in their viscera than rams. In rams, the highest proportion of daily energy deposited as protein was found in carcass soft tissue followed by wool, whereas a reverse order was noticed for ewe lambs. Generally, the highest proportion of daily energy deposited as lipid was found in carcass soft tissue followed by viscera, bone and hide. Maintenance energy requirement (E_m) were lower (P<0.01) for rams than ewes. Also, E_m and the metabolizable energy intake in docked lambs were lower (P<0.01) than undocked lambs.

Keywords:

• Docking
• fat-tailed lamb
• energy utilization
• body weight gain