l.mengying@cnhu.com
zhanglei@cnhu.com
z.honghe@cnhu.com
s.xiaowei@cnhu.com
1Researchers, Zhejiang NHU Company Ltd., Animal Nutrition Application Service Center
*Corresponding author
The global poultry industry, particularly broiler production, has grown rapidly to meet the increasing demand for animal protein. However, chronic heat stress(CHS) presents a significant challenge, affecting approximately 60% of broiler farming regions worldwide and resulting in billions of dollars in annual economic losses due to reduced growth rates and elevated mortality. CHS negatively impacts broiler health through multiple physiological mechanisms. Prolonged heat exposure decreases feed intake and reallocates metabolic energy toward thermoregulation, thereby impairing growth performance. Affected broilers exhibit diminished growth, compromised organ function, and weakened immune responses, all contributing to substantial economic consequences.
Taurine, a β-amino acid that does not participate in protein synthesis, has shown promising effects in mitigating stress-related disorders across various species. It exerts protective effects by activating antioxidant pathways, stabilizing cellular membranes, and modulating neurotransmitter activity. However, research on the application of taurine in broilers under CHS remains limited, particularly concerning optimal dosage and long-term physiological outcomes. This study aims to investigate the effects of dietary taurine supplementation on the growth performance and serum biochemical indices of broilers exposed to CHS. The findings may offer practical strategies for improving poultry resilience in heat-prone environments and contribute to the sustainability of the poultry industry.
A total of 600 AA＋broilers were randomly assigned to 5 dietary treatments, with 12 replicates of 10 broilers.From 22 to 42 days of age, chickens in the normal control(NC) and heat stress(HS) groups were fed a basal diet(Table 1). From days 29 to 42, in the taurine-supplemented groups (HT0.05, HT0.1, HT0.2) of the HS (heat stress) model, the chickens were fed a basal diet supplemented with 0.05%, 0.1%, and 0.2% taurine, respectively. From day 22 to day 28, all the chickens were raised at an appropriate temperature. From 29 to 42 days of age, NC-group chickens were kept at appropriate temperature. Meanwhile, chickens in the HS and HT groups were reared in a high-temperature environment(9:00-21:00, 32±1℃; 21:00-9:00, 22±1℃). Taurine, with a purity of 99.9%, was purchased from Zhejiang NHU Company Ltd.
Table 1. Composition and calculated nutrient content of the basal diet.
| Ingredient | 0-21d (g/kg) | 22-42d (g/kg) | ||
| Corn | 542 | 594.75 | ||
| Soybean meal(43%) | 275 | 228 | ||
| Soybean oil | 43 | 45 | ||
| Flour | 80 | 80 | ||
| Dicalcium phosphate | 20.5 | 18 | ||
| Limestone | 9 | 8.2 | ||
| Lysine(98%, HCl) | 4.3 | 3.9 | ||
| DL-Methionine | 3.4 | 2.8 | ||
| Threonine | 2.6 | 2.2 | ||
| Valine | 1.6 | 1.3 | ||
| Arginine | 1.8 | 1.6 | ||
| Isoleucine | 1.25 | 1.05 | ||
| Tryptophan | 0.2 | 0.2 | ||
| Glycine | 2 | 2 | ||
| Vitamin premix1 | 2 | 2 | ||
| Mineral premix2 | 2 | 2 | ||
| Choline chloride(50%) | 1.5 | 1.4 | ||
| Mould inhibitor | 1 | 1 | ||
| Phytase | 0.1 | 0.1 | ||
| Corn starch | 4.25 | 2.0 | ||
| Salt | 2.5 | 2.5 | ||
| Total | 1000 | |||
| Calculated nutrient and energy level | ||||
| AMEn, Kcal/kg | 3100 | 3100 | ||
| CP, % | 18.64 | 17.04 | ||
| d-Lys, % | 1.15 | 1.02 | ||
| d-Thr, % | 0.809 | 0.715 | ||
| d-Met, % | 0.582 | 0.506 | ||
| M+C, % | 0.827 | 0.735 | ||
| d-Val, % | 0.891 | 0.793 | ||
| d-Ile, % | 0.774 | 0.685 | ||
| d-Arg, % | 1.23 | 1.091 | ||
| d-Trp, % | 0.210 | 0.187 | ||
| Ca, % | 0.88 | 0.78 | ||
| aP, % | 0.44 | 0.39 | ||
1 Supplied per kilogram of diet: vitamin A, 10,000 IU as vitamin A acetate; vitamin D3, 4,500 IU as cholecalciferol; 65 IU of vitamin E; vitamin K, 3.0 mg as menadione sodium bisulfate; thiamine, 2.5 mg as thiamine mononitrate; 6.5 mg of riboflavin; pyridoxine, 3.2 mg as pyridoxine hydrochloride; 0.03 mg of vitamin B12; pantothenic acid, 18 mg as D-calcium pantothenate; 60 mg of niacin; 1.9 mg of folic acid; and 0.25 mg of biotin.
2 Supplied per kilogram of diet: copper 8 mg, ferrous 40 mg, manganese 100 mg, zinc 60mg, iodine 0.7 mg, selenium 0.3 mg.
Growth performance
Table 2 Effects of dietary taurine supplementation on the growth performance in broilers under chronic heat exposure.
| Treatment | 29-42d ADG | 29-42d ADFI | 29-42d FCR |
| NC | 114.82±1.29a | 190.2±1.18a | 1.66±0.01b |
| HS | 73.27±1.10b | 149.89±2.2b | 2.05±0.04a |
| HT0.05 | 74.43±1.56b | 146.63±0.90b | 1.98±0.03a |
| HT0.1 | 77.53±2.03b | 150.61±2.17b | 1.95±0.04a |
| HT0.2 | 76.51±1.57b | 149.74±1.79b | 1.96±0.02a |
| S.E.M | 2.165 | 2.268 | 0.022 |
| P | <0.001 | <0.001 | <0.001 |
a, b Means with different superscripts within each column are significantly different (P < 0.05)
Compared with the NC group and HS group, there were no significant differences in the activities of alanine transaminase(ALT), as well as the levels of cortisol and thyroxine in the blood of broilers in the HT group (P > 0.05). Compared with the NC group, the blood uric acid level in the HS group was higher. However, due to taurine supplementation, the blood uric acid level in the HT group was significantly decreased, and in particular, the uric acid level in the HT0.2 group was significantly lower than that in the NC group (P < 0.05). Compared with the HS group, the blood malondialdehyde(MDA) level in the HT group showed a decreasing trend, yet no significant difference was observed(P > 0.05).
Table 3 Effects of dietary taurine supplementation on the serum biochemical indices in broilers under chronic heat exposure.
| Treatment | Uric acid (μmol/L) | ALT (U/L) | MDA (ng/mL) | Cortisol (ng/mL) | Thyroxine (ng/mL) |
| NC | 108.24a | 4.19 | 5.45 | 104.50 | 229.58 |
| HS | 127.64a | 4.00 | 6.79 | 112.22 | 255.19 |
| HT0.05 | 108.11a | 4.18 | 5.72 | 110.10 | 327.93 |
| HT0.1 | 100.28ab | 4.84 | 5.25 | 101.72 | 264.34 |
| HT0.2 | 77.67b | 3.63 | 5.58 | 108.31 | 229.42 |
| S.E.M | 3.862 | 0.265 | 0.233 | 3.398 | 19.000 |
| P | 0.001 | 0.716 | 0.254 | 0.879 | 0.473 |
a, b Means with different superscripts within each column are significantly different (P < 0.05)
Conclusion In the present study, heat stress significantly decreased the growth performance of broilers. However, dietary supplementation with taurine over a period of two weeks was found to mitigate the adverse effects of chronic heat exposure on growth performance. Blood biochemical indicators, such as blood uric acid level and MDA, can reflect the physiological status of animals. Studies have demonstrated that heat stress induces renal metabolic imbalance and exacerbates oxidative stress in broilers, whereas taurine supplementation exerts a mitigating effect on the damage caused by heat stress.Based on the findings of this study, a dietary taurine supplementation level of 0.1% is recommended for broilers subjected to heat stress.