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Effects of Stocking Density and Group Size on Thermoregulatory Responses of Laying Hens under Heat-Challenging Conditions

机译:挑战性条件下放养密度和种群规模对蛋鸡温度调节反应的影响

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°C or 76°F) and warm conditions (32°C or 90°F, followed by 35°C or 95°F). No differences in core body temperature (CBT) of the hens were observed among the treatment regimens at 24°C. In general, mean CBT increased with heat exposure duration (P u3c 0.0001) but leveled off after the 32°C phase. At 32°C, CBT was higher for GS of 16 vs. 8 (42.3°C vs. 42.1°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°C and 42.2°C vs. 41.9°C and 42.1°C, respectively, P = 0.009). Bird body mass decreased as heat exposure duration increased (P u3c 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°C followed by 35°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(即增加每只鸡笼子的地板面积)和改变组群规模的做法。这项研究是对24组48只W-36产蛋母鸡(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 cm2母鸡-1)的影响; 54 ,60、72或90 in.2母鸡1)和组的大小(GS)(每笼8或16只母鸡)应对母鸡应对热挑战的能力。在热中性(24°C或76°F)和温暖条件(32°C或90°F,然后35°C或95°F)下收集数据。在24°C的治疗方案中,未观察到母鸡的核心体温(CBT)差异。通常,平均CBT随暴露时间的延长而增加(P <0.0001),但在32°C阶段后趋于平稳。在32°C时,GS的16与8相比CBT更高(42.3°C与42.1°C,P = 0.05),SD的348和387 cm2 hen-1高于465或581 cm2 hen-1 (分别为42.4°C和42.2°C与41.9°C和42.1°C,P = 0.009)。鸡的体重随着受热时间的延长而降低(P <0.0001),但在各处理之间未观察到差异。在热中性期间未观察到死亡,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,CBT较低,但增加的空间不足以明显应对32°C和35°C的热挑战。

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