Villalobos O, Guillén O, García J
1Departamento de Zootecnia, Facultad de Agronomía, Universidad del Zulia, Av. 16 (Guajira), Ciudad Universitaria 'Dr. Antonio Borjas Romero'. Núcleo Agropecuario, Maracaibo, Venezuela.
Animal. 2010 Sep;4(9):1568-76. doi: 10.1017/S1751731110000613.
In order to evaluate heat stress and circadian rhythm 46 nulliparous rabbit does with a BW of 3.67 ± 0.05 kg (s.e.) were used. They were clipped once or not and rectal temperature, feed and water intake were recorded for 24 h. From this group, 43 rabbit does were mated 7 days after rectal measurements, and randomly assigned to one out of two breeding systems (including in both systems rabbit does that had been clipped or not). In the control one (C) rabbit does were mated 14 days after parturition and litter weaned at 35 days of age, and in the extensive one (E) they were mated 21 after parturition and weaned at 42 days of age. Rabbit doe and litter performance were recorded for 6 months (first three cycles). Two hundred twenty-eight weaned rabbits were divided into two cage sizes: 0.5 and 0.25 m2 with eight and four rabbits per cage, respectively, to study growing performance. Farm and rectal temperatures were minimal and feed and water intake maximal during the night (P < 0.001). Unclipped rabbit does showed higher rectal temperature (P = 0.045) and lower feed intake (P = 0.019) respect to clipped does, which are symptoms of heat stress. Neither breeding system nor cycle number influenced fertility, total number of kits born, born alive or dead per litter (91.6%, 6.98, 5.80 and 1.19 on average, respectively). Kit mortality during lactation tended to increase in E compared with C group (48.5% v. 63.4%; P = 0.070), reducing the number of kits at weaning per litter by 33% (P = 0.038). It also increased in the second and third cycles compared with the first (P ⩽ 0.054). It resulted that feed efficiency (g weaned kits/g feed intake does + litter) tended to decrease in E respect C group (P = 0.093), whereas it was impaired successively from the first to the third cycle by 48% (P = 0.014). Growing rabbits from the E group were heavier at weaning (by 38%; P < 0.001), showed a higher feed intake (+7.4%) and lower feed efficiency (-8.4%) throughout the fattening period (P ⩽ 0.056) respect to C group. However, age at slaughter was not different respect to C group (77.3 days on average). Cage size had minor influence in growing performance. In conclusion, rabbit doe and litter productivity impaired when lactation is extended from 35 to 42 days and along successive reproductive cycles.
为了评估热应激和昼夜节律，选用了46只体重为3.67±0.05千克（标准误）的未生育母兔。对它们进行一次剪毛或不剪毛处理，并记录24小时的直肠温度、采食量和饮水量。在该组中，43只母兔在直肠测量7天后进行交配，并随机分配到两种繁殖系统中的一种（两种系统中都包括已剪毛或未剪毛的母兔）。在对照组（C）中，母兔在分娩后14天交配，幼崽在35日龄时断奶；在粗放组（E）中，母兔在分娩后21天交配，幼崽在42日龄时断奶。记录母兔和幼崽6个月（前三个周期）的生产性能。228只断奶幼兔被分为两种笼舍大小：0.5平方米和0.25平方米，每笼分别饲养8只和4只兔子，以研究生长性能。夜间农场温度和直肠温度最低，采食量和饮水量最高（P<0.001）。与剪毛母兔相比，未剪毛母兔的直肠温度更高（P=0.045），采食量更低（P=0.019），这些都是热应激的症状。繁殖系统和周期数均不影响繁殖力、每窝出生的幼崽总数、存活或死亡的幼崽数（平均分别为91.6%、6.98、5.80和1.19）。与C组相比，E组哺乳期幼崽死亡率有增加趋势（48.5%对63.4%；P=0.070），每窝断奶幼崽数减少33%（P=0.038）。与第一个周期相比，第二和第三个周期的幼崽死亡率也增加了（P≤0.054）。结果表明，与C组相比，E组的饲料效率（断奶幼崽克数/母兔和幼崽采食量克数）有降低趋势（P=0.093），而从第一个周期到第三个周期，饲料效率依次降低48%（P=0.014）。与C组相比，E组的生长兔在断奶时体重更重（重38%；P<0.001），在育肥期的采食量更高（+7.4%），饲料效率更低（-8.4%）（P≤0.056）。然而，屠宰年龄与C组无差异（平均77.3天）。笼舍大小对生长性能影响较小。总之，当哺乳期从35天延长到42天以及连续繁殖周期时，母兔和幼崽的生产力会受到损害。
