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Effects of stocking density and group size on thermoregulatory responses of laying hens under heat-challenging conditions.

机译:在热挑战条件下,放养密度和种群规模对蛋鸡温度调节反应的影响。

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摘要

Sectors of the U.S. cage layer industry have begun adopting practices of reduced stocking density (i.e., increased cage floor space per hen) and varying group sizes. This study was conducted with 24 groups of 48 W-36 laying hens (39 to 46 weeks old) to assess the effects of cage floor space or stocking density (SD) (348, 387, 465, or 581 cm2 hen-1; 54, 60, 72, or 90 in.2 hen-1) and group size (GS) (8 or 16 hens per cage) on the ability of the hens to cope with heat challenge. Data were collected at thermoneutral (24 degrees C or 76 degrees F) and warm conditions (32 degrees C or 90 degrees F, followed by 35 degrees C or 95 degrees F). No differences in core body temperature (CBT) of the hens were observed among the treatment regimens at 24 degrees C. In general, mean CBT increased with heat exposure duration (P<0.0001) but leveled off after the 32 degrees C phase. At 32 degrees C, CBT was higher for GS of 16 vs. 8 (42.3 degrees C vs. 42.1 degrees C, P=0.05) and higher for SD of 348 and 387 cm2 hen-1 than for 465 or 581 cm2 hen-1 (42.4 degrees C and 42.2 degrees C vs. 41.9 degrees C and 42.1 degrees C, respectively, P=0.009). Bird body mass decreased as heat exposure duration increased (P<0.0001), but no differences were observed among the treatments. No mortalities were observed during the thermoneutrality period, and the mortality rate increased with heat exposure duration. The results indicate that, while CBT was lower for lower SD, the increased space was not sufficient to offer a clear benefit for coping with heat challenge of 32 degrees C followed by 35 degrees C.
机译:美国笼式蛋鸡产业的部门已经开始采用降低放养密度(即增加每只鸡的笼子地板空间)和改变组群规模的做法。这项研究是由24组48头W-36产蛋鸡(39至46周龄)进行的,以评估笼舍空间或放养密度(SD)(348、387、465或581 cm 2 < / sup> hen -1 ; 54,60、72或90 in。 2 hen -1 )和组大小(GS)(每笼8或16头母鸡)。在热中性(24摄氏度或76华氏度)和温暖条件(32摄氏度或90华氏度,然后是35摄氏度或95华氏度)下收集数据。在24摄氏度的治疗方案中,未观察到母鸡的核心体温(CBT)的差异。通常,平均CBT随暴露时间的延长而增加(P <0.0001),但在32摄氏度阶段后趋于平稳。在32摄氏度时,GS分别为16和8时CBT较高(42.3摄氏度和42.1摄氏度,P = 0.05),SD则为348和387 cm 2 hen -1 大于465 cm或581 cm 2 hen -1 (分别为42.4摄氏度和42.2摄氏度和41.9摄氏度和42.1摄氏度, P = 0.009)。鸡的体重随着受热时间的延长而降低(P <0.0001),但各处理之间未观察到差异。在热中性期间未观察到死亡率,并且死亡率随着受热时间的延长而增加。结果表明,尽管对于较低的SD而言CBT较低,但增加的空间不足以为应对32摄氏度然后是35摄氏度的热挑战提供明显的好处。

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