Effect of Naked Neck gene on egg production of layers selected for improved clutch length and selected for reduced residual feed consumption

• Main Authors: Nein-Zu Huang, 黃念祖
• Other Authors: Yen-Pai Lee
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/77087992484960001405

碩士 === 國立中興大學 === 畜產學系 === 93 === Taiwan, located in the tropical and subtropical region, is hot and humid in the summer. The temperature is often soaring up to over 35℃. Heat stress under high ambient temperature, not only influences chicken's physiological functions, but also results in egg production loss in laying birds. The purpose of this experiment was to study the effect of the naked neck gene on the adaptability of the two selected strains, one for longer clutch length and the other for reduced residual feed consumption, from the Institut National de la Recherche Agronomique, to the natural hot environment in Taiwan. Furthermore, the results might be an useful reference to the evaluation of the naked neck gene to reduce the summer heat stress in Taiwan. The results of both strains shows that, chickens with naked neck gene tend to have lighter body weight at any age, possibly due to less feather covering, and lower comb and/or rectal temperature than their normal feathering sibs. It suggests that they are superior in maintaining normal body temperature under hot environment than the normal feathered birds. Chickens with the naked neck gene tend to have stronger and longer shanks and longer wattles which represent a larger surface area to dissipate heat. The naked neck birds tend to lay their first egg at a later age. Their egg weight, egg mass production and yolk weight also tend to be heavier than those from the normal chicken. Chickens carrying naked neck genes had higher feed consumption and residual feed consumption. It is possible related to that higher heat loss requires more feed consumption to compensate the waste of energy. The results of the selected and the control strains for improved clutch length revealed that, the selection for clutch length could increase the number of eggs laid and egg mass production, and reduce the age at first egg. However, it also reduced the egg weight. Selection for clutch length had the merits to significantly increase the average clutch length and the maximum clutch length, and reduce the number of clutches, the average pause length, the maximum pause length and the total pause days. However, it also reduced the yolk weight and the egg shell weight significantly. The test results of the strain selected for reduced residual feed consumption revealed that chickens with the naked neck gene tend to have longer average clutch length and fewer number of clutches. In addition, the higher Haugh unit, thicker and heavier egg shell thickness suggest that the naked neck gene could also improve the albumin and the egg shell qualities of eggs.