الفهرس 
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Abstract
Objectives: The present study was conducted to study effects of genotype and weaning age interaction (G×WA) on growth traits of animals belonged to two lines of rabbit on performance of kits during the fattening period involving synthetic Egyptian line (APRI) and a Spanish maternal line (V line)
Methods & Results: The present study was conducted involving synthetic Egyptian line (APRI) and a Spanish maternal line (V line). Rabbits raised at the Experimental Rabbitry of Animal Production Research Institute, Sakha, Kafr El-Sheikh Governorate, Egypt .
One thousand and eight hundred young rabbits were chosen to be weaned. At weaning the first age kids weaning treat¬ment ≥28 days of age at weaning (WA1). The second weaning age was 28 < T ≥ 35 days included rabbit weaned at 29, 30,31, 32, 33, 34 and 35 days of age (WA2). While the third age of weaning was 35 < T ≥ 40 days included rabbit weaned at 36, 37,38, 39 and 40 days of age (WA3). The fourth age of weaning included rabbit weaned at 41, 42, 43 days (40<T days, WA4). At weaning, kids were placed in collective cages of about 5 rabbits until 16 weeks of age Individual rabbit weights were recorded weekly. Body weight (BW, g) was measured at 4 (BW4), 6 (BW6), 8 (BW8), 10 (BW10), 12 (BW12), 14 (BW14) and 16 (BW16) weeks of age. These days correspond to age at 4 weeks, the end of the 2nd (critical period after weaning, at 6 weeks), 8th weeks of fattening, and the slaughter week (10 weeks of age) and advanced weeks of age, respectively. Individual average daily gain (ADG, g/d) during from 4 to 6 wk (ADG4-6), 6-8 wk (ADG6-8), 8-10 wk (ADG8-10), 10-12 wk (ADG10-12), 12-14 wk (ADG12-14), 14-16 wk (ADG14-16), overall fattening period (ADG4-10), 6-10 wk (ADG6-10, after critical period of age), 10-16 wk (ADG10-16) and 4 to 16 wk (ADG4-16) of age were calculated.
The APRI line is superior to V line in all body weight traits during the whole period of the experiment with significant differences. Difference in body weight at 4 weeks was around 80 g in favor of line APRI with a significant difference and thus observed differences could be explained because fattened rabbits from the APRI line came from litters with the lowest number of kits born alive and the lowest number of rabbits at weaning. The differences in body weight are economically important with significant differences were observed where body weight of kits weaned at the age of more than 35 days was the higher than rabbits weaned before 35 d with a relevant difference (749.1 vs 835.535).The V line is affected by weaning age than APRI line where the differences between WA1 and WA4 in V and APRI lines were 153.53 and 87.56, respectively. There is a clear line-weaning age interaction where the rabbits in WA2 of APRI line were the heaviest while the rabbits of WA3 were the heaviest .
Conclusion: Under Egyptian conditions, results give a good hope of the APRI line, important differences for growth traits were detected favoring APRI line than V line. The early weaning had negative effects on growth traits during the fattening period, but these negative effects were compensated after 8 weeks of age. The early weaning (before 28 d) is not recommended for Egyptian rabbit. Clear indications for Genotype x weaning age (G x WA) interactions were observed for growth traits where V line is affected by weaning age than APRI line. It is recommended to wean the young rabbit of APRI between 29-35 days where in V line is recommended the weaning age after 35 days.