One hundred and twenty New Zealand White growing rabbits
were used to study the effects of period of the year (60 animals in the
mild, and another 60 in the hot period), feeding system (30 ad libitum
and 30 fed only at night per period), and Nigella sativa seeds dietary
supplementation (0, 0.5 and 1% seeds, 10 animals per each group of
Nigella sativa seeds dietary supplementation). The Temperature–
humidity index (THI) values estimated were 18.9 and 29.7 at mild and
hot periods, indicating absence of heat stress during the mild period
and exposure to severe heat stress during the hot period. Exposure to
severe heat stress decreased (P<0.01) feed intake (by 14.6%), live body
weight (by 17.4%), daily live body gain (by 28.3%) than in the mild
period. Dressing percentage and prime cuts percentage were also
decreased (by 11.7 and 17.3%, respectively) in the hot period.
Contrarily, heat stress increased (P<0.01) water intake (by 86.3%), feed
conversion (by 19.85%), rectum temperature (by 2.6), respiration rate
(by 14.5%) and serum urea-N (by 21.8%) by exposure to severe heat
stress. Serum total proteins, albumin, globulin and creatinine were
insignificantly affected by period of the year. Feeding growing rabbit
only during the night improved (P<0.05) feed intake (by 6.8%), live
body weight (by 5.6%) and daily live body gain (by 10.2%) compared
to ad libitum feeding system during all day. Similarly, dressing
percentage and prime cuts were increased (by 4.4 and 7.4%,
respectively). Water consumption of animals fed only during the night
decreased (by 22.5%; P<0.05) than of those fed all the day. Feed
conversion rate, rectum temperature, respiration rate, serum total
proteins, albumin, globulin, urea and creatinine, were insignificantly
affected by feeding system. Dietary supplementation with 1.0% Nigella
sativa seeds increased (P<0.05) feed intake, live body weight, serum
total protein and serum globulin than without supplementation.
Dressing percentage and prime cuts were also increased with Nigella
sativa supplementation. Feed conversion, water consumption, daily live
gain weight, rectum temperature, respiration rate, serum albumin, urea
and creatinine were insignificantly affected with Nigella sativa seeds
dietary supplementation. It is recommended to feed rabbits only at
night, under the warm sub-tropical environmental conditions and to
supplement growing rabbits with 1.0% N. sativa seeds. All interaction
effects between period of the year and feeding system on the studied
traits were not significant. Therefore, the main effects were only
discussed.