Special Edition: pig and poultry feed trends

Feed additive may help birds weather the heat

By Aerin Einstein-Curtis

- Last updated on GMT

Related tags Heat stress Small intestine

© iStock
© iStock
Additive N-acetylcysteine may boost growth performance and gut function in broilers faced with heat stress, say researchers.

A team of international researchers studied the use of N-acetylcysteine (NAC) as a feed supplement and its influence on broiler chick growth and intestinal function. The group published their results in the journal Animal Feed Science and Technology​.

“In order to clarify the efficacy of NAC application in poultry production, further study is warranted to investigate the effects of NAC on growth performance and intestine function of broilers under heat stress,”​ members of the team said.

The team found that using the feed supplement improved mortality rate, the feed to gain ratio, and lowered plasma corticosterone levels, malondialdehyde (MDA) concentration and intestinal mucosal levels of heat shock protein (HSP70), adenosine monophosphate-activated protein kinase (AMPK) and heme-oxigenase (HMOX).

“Dietary supplementation of 1 g/kg NAC improved the growth performance, intestinal morphology and absorptive function, maintained intestinal energy metabolism, and mitigated intestinal oxidative stress in the heat-stressed broilers,”​ said the researchers. “Improving the intestinal function may be an effective approach to partially attenuate the detrimental effects of heat stress on birds’ health and performance.”

Why NAC?

Global warming is a concern for animal production as hyperpyrexia can cause bird death and reduce poultry growth, both of which contribute to economic loss, the researchers said. Birds facing heat stress eat less, drink more water and spend little time moving.

Physiological and metabolic responses including altered blood parameters, plasma hormone concentrations, meat acidity and oxidative stress also have been noted in heat stressed birds, they said. High temperature conditions also can induce intestinal dysfunction, impair intestinal morphology, and increase intestinal permeability, while decreasing absorption immune functioning.

Several different nutritional supplements have been explored to improve bird response, they said. 

Previous work the team did exploring the use of NAC indicated that the feed supplement might improve growth performance and protect birds against heat stress, the researchers said. NAC can be metabolized in the small intestine to generate glutathione.

But, there is little research exploring the use of the additive in poultry diets, they said.

Feeding trials

In the study, 200 chicks were given one of two diets and two growing environments, said the researchers. The diets included a corn- and soybean meal-based basal diet and that diet with 1 g/kg NAC and the temperatures were thermo-neutral or heat stress.

“However, from day 8–35 of age, two groups, including one basal diet group and one NAC-diet group, were exposed to 36 ± 1 °C and 26 ± 1 °C as cyclic heat stress groups,”​ they said. “The other two groups (one basal diet group and one NAC-diet group) were raised at 30 ± 1 °C (from day 8–14 of age) and 26 ± 1 °C (from day 15–35 of age) as thermo-neutral groups.”

Average daily gain (ADG), average daily feed intake (ADFI) and the feed to gain ratio were determined, they said. On day 36, blood samples were collected, a selection of birds was harvested and the small intestines were analyzed.

Results

Broilers experiencing heat stress had lower ADFI and ADG than those in normal temperatures, said the researchers. Of the two groups in high heat production, those getting the NAC supplementation had better ADFI and an improved feed to gain ratio.

The treatment also lowered mortality rate, 6% for those getting the NAC supplement and 12% for the control group experiencing heat stress, they said. The additive had little influence on triiodothyronine (T3) and thyroxine (T4) levels, but it lowered corticosterone concentration.

The supplement improved the villus height to crypt depth ratio in heat stress conditions, they said. It also mitigated some effects of heat stress on broilers including by increasing adenosine triphosphate (ATP) and total adenine nucleotide (TAN ) levels in the jejunum and supporting activity of catalase (CAT) while repressing MDA.

In the heat stressed birds, the additive also boosted trypsine activity in the jejunum and lowered levels of HSP70, HMOX and AMPK, said the researchers.

Source: Animal Feed Science and Technology

Title: N-acetylcysteine improves the growth performance and intestinal function in the heat-stressed broilers

DOI: published online ahead of print: 10.1016/j.anifeedsci.2016.07.014

Authors: Dan Yi, Yongqing Hou, Linglin Tan, Man Liao, Jiaqian Xie, Lei Wang, Binying Ding, Ying Yang, Joshua Gong

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