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当前位置: 首页 > 文章 > Stress and immunological response of heifers divergently ranked for residual feed intake following an adrenocorticotropic hormone challenge 畜牧与生物技术杂志(英文版) 2017,8
Position: Home > Articles > Stress and immunological response of heifers divergently ranked for residual feed intake following an adrenocorticotropic hormone challenge Journal of Animal Science and Biotechnology 2017,8

Stress and immunological response of heifers divergently ranked for residual feed intake following an adrenocorticotropic hormone challenge

作  者：
A. K. Kelly;P. R. Lawrence;Bernadette Earley;David A. Kenny;M. McGe
单  位：
Livestock Systems Research Department Teagasc, Animal & Grassland Research and Innovation Centre, Grange, Dunsany, Co. Meath, Irelan;Animal and Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Dunsany, Co. Meath, Ireland;Livestock Systems Research Department Teagasc, Animal & Grassland Research and Innovation Centre, Grange, Dunsany, Co. Meath, Ireland;School of Agriculture and Food Science, College of Health and Agricultural Sciences, University College Dublin, Dublin 4, Ireland
关键词：
Beef cattle;Cortisol;Feed efficiency;Residual feed intake;Stress respons
摘  要：
Background: When an animal is exposed to a stressor, metabolic rate, energy consumption and utilisation increase primarily through activation of the hypothalamic-pituitary-adrenal (HPA) axis. Changes to partitioning of energy by an animal are likely to influence the efficiency with which it is utilised. Therefore, this study aimed to determine the physiological stress response to an exogenous adrenocorticotropic hormone (ACTH) challenge in beef heifers divergently ranked on phenotypic residual feed intake (RFI). Results: Data were collected on 34 Simmental weaning beef heifers the progeny of a well characterized and divergently bred RFI suckler beef herd. Residual feed intake was determined on each animal during the post-weaning stage over a 91-day feed intake measurement period during which they were individually offered adlibitum grass silage and 2 kg of concentrate per head once daily. The 12 highest [0.34 kg DM/d] and 12 lowest [-0.48 kg DM/d] ranking animals on RFI were selected for use in this study. For the physiological stress challenge heifers (mean age 605 +/- 13 d; mean BW 518 +/- 31.4 kg) were fitted aseptically with indwelling jugular catheters to facilitate intensive blood collection. The response of the adrenal cortex to a standardised dose of ACTH (1.98 IU/kg metabolic BW0.75) was examined. Serial blood samples were analysed for plasma cortisol, ACTH and haematology variables. Heifers differing in RFI did not differ (P = 0.59) in ACTH concentrations. Concentration of ACTH peaked (P < 0.001) in both RFI groups at 20 min post-ACTH administration, following which concentration declined to baseline levels by 150 min. Similarly, cortisol systemic profile peaked at 60 min and concentrations remained continuously elevated for 150 min. A RFI x time interaction was detected for cortisol concentrations (P = 0.06) with high RFI heifers had a greater cortisol response than Low RFI from 40 min to 150 min relative to ACTH administration. Cortisol response was positively associated with RFI status (r = 0.32; P < 0.01). No effect of RFI was evident for neutrophil, lymphocytes, monocyte, eosinophils and basophil count. Plasma red blood cell number (6.07 vs. 6.23; P = 0.02) and hematocrit percentage (23.2 vs. 24.5; P = 0.02) were greater for low than high RFI animals. Conclusions: Evidence is provided that feed efficiency is associated with HPA axis function and susceptibility to stress, and responsiveness of the HPA axis is likely to contribute to appreciable variation in the efficiency feed utilisation of cattle.

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