Effect of Intermittent and Mild Cold Stimulation on the Immune Function of Bursa in Broilers.

Yanhong Liu,Jianhong Li,Yajie Fu,Shuang Li,Jingwen Yin,Ge Xue,Runxiang Zhang

doi:10.3390/ani10081275

Yanhong Liu, Jianhong Li + Show 5 more

Open Access

https://doi.org/10.3390/ani10081275

Copy DOI

Abstract

Simple SummaryCold stress has an adverse effect on immune, antioxidant, and neuroendocrine systems as well as growth performance of broilers. Much attention was focused on how to improve the cold resistance of animals. However, it is not clear how intermittent and mild cold stimulation regulate the immune function. Therefore, the present study was designed to investigate the effect of intermittent and mild cold stimulation on the immune function of bursa in broilers. Our results indicated that the intermittent and mild cold stimulation (IMCS) could help broilers adapt to the low ambient temperature and maintain homeostasis by modulating the production of Toll-like receptors (TLRs), cytokines, and avian β-defensins (AvBDs) in the bursa of broilers. We expect to find a way to promote the establishment of cold adaptation through repeated intermittent cold trainings.Cold stress causes growth performance to decrease and increases production costs. Cold adaptation can enhance immune function and alleviate the negative impact caused by the stress condition. The study investigated the effect of intermittent and mild cold stimulation on the immune function of the bursa of Fabricius in broilers. A total of 400 healthy one-day-old broilers were divided into the control group (CC) and cold stimulation (CS) groups. The CC group was raised at a conventional raising temperature of broilers, while the CS groups were raised at 3°C below the temperature of the CC for three-, four-, five-, or six-hour periods at one-day intervals from 15 to 35 days of age (D35), denoted CS3, CS4, CS5, and CS6, respectively. Subsequently, they were raised at 20°C from 36 to 49 days of age (D49). The expression levels of TLRs, cytokines, and AvBDs were determined to access the immune function of bursa in broilers. After 21-day IMCS (at D36), the expression levels of TLR1, TLR15 and TLR21, interleukin (IL)-8, and interferon (IFN)-γ, as well as AvBD8 in CS groups, were lower than those in CC (p < 0.05). The expression levels of TLR3, TLR4 and TLR7, were decreased in the CS3, CS5, and CS6 groups (p < 0.05), but there were no significant differences in both the CC and CS4 groups (p > 0.05). When the IMCS ended for 14 days (at D49), the expression levels of TLR2, TLR3, TLR5, TLR7, TLR15, and TLR21, and IL-8, as well as AvBD2, AvBD4 and AvBD7 in CS groups, were lower than those in CC (p < 0.05). In addition to CS4, the expression levels of TLR1, IFN-γ, and AvBD8 in CS3, CS5, and CS6 were still lower than those in CC (p < 0.05). We concluded that the intermittent and mild cold stimulation could regulate immunoreaction by modulating the production of TLRs, cytokines, and AvBDs in the bursa, which could help broilers adapt to low ambient temperature and maintain homeostasis.

Highlights

In the alpine region, livestock and poultry often suffer from cold stress due to the low ambient temperature in winter
When the IMCS training ended for 14 days, the expression levels of AvBDs except AvBD5 and AvBD8 in the cold stimulation (CS) groups were significantly lower compared to the control group (p < 0.05)
We found that the expression levels of most TLRs were lower in the CS groups compared to the control group after 21-day IMCS, with the lowest expression levels of TLR1, TLR3, TLR4, TLR5, TLR7, and TLR15 in the CS5 group

Summary

Introduction

Livestock and poultry often suffer from cold stress due to the low ambient temperature in winter. Cold acclimation can enhance the immune function and disease resistance of the body. Our previous study has shown that when broilers were continuously given a cold stimulation of 3 ◦ C lower than rearing temperature for the period of 8 to 42 days of old, they were more likely to adapt to ambient temperature changes during their later growth stages [7]. Li et al [8] found that early cold stimulation at 3 ◦ C below the control group temperature could improve the antioxidant function in broilers. Moderate cold stimulation will not destroy homeostasis in the early growth of broilers, but will enhance disease resistance in later growth stages [10,11,12,13]

Objectives

Methods

Results

Conclusion