Birds cannot sweat and must rely on panting to cool down. That’s an inefficient method when you consider their feathers also serve as insulation. Maintaining animal welfare becomes harder during high-heat conditions. Additionally, the drop in performance and egg production can mean economic challenges for producers’ businesses. Producers should take a holistic approach of feed, farm and health management to defend against heat stress.
As global temperatures increase, heat stress is becoming a major challenge for poultry producers globally. Since 1980 every decade has seen a temperature hike, and the seven hottest years on record occurred since 2015.¹
Different strategies of management practices and diet-based interventions can support flocks during episodic or sustained periods of high temperatures. We caught up with Dr. Narendra Venkatareddy, global product manager with Selko, the Feed Additives brand of Nutreco, to learn more about how heat stress challenges affects poultry flocks – and what producers can do to manage heat stress. He also shared findings from a trial conducted in Australia with the University of New England. The trial found that the type of trace mineral supplied to laying hens can influence quality and performance indicators including egg production, egg FCR (feed conversion ratio) and egg mass.
Where are you seeing heat stress becoming more of a problem for poultry producers?
Global climate changes have their effect on animal production. Where heat stress used to be an issue for certain regions only, nowadays also areas with moderate climates are affected. The number of days where the temperature-humidity index (THI) exceeds the comfort threshold of the animals is increasing in the northern United States, Canada, and Europe and thus heat stress has become one of the most important ambient stressors in animal production worldwide.
What consequences does heat stress present to poultry?
Birds cannot sweat and must rely on panting to cool down. That’s an inefficient method when you consider their feathers also serve as insulation. Maintaining animal welfare becomes harder during high-heat conditions. Additionally, the drop in performance and egg production can mean economic challenges for producers’ businesses. For example, in just one country – the U.S. – industry research shows that heat stress causes the nation’s producers about $128 to $165 million in economic losses annually.²
What are some signs that indicate birds are experiencing heat stress?
The list is extensive. Clinical symptoms can include panting, lethargy, lower feed intake, poor average daily gain, higher feed conversion ratios and a drop in production or performance. In layers, high temperatures can correspond to a noticeable decline in daily egg production and the situation may adversely influence elements like egg mass and shell quality.
How can high heat conditions affect a bird internally?
The negative effects of heat stress, such as generation of free radicals, antioxidant imbalance, intestinal hypoxia, and gut barrier integrity disruption happen prior to the occurrence of clinical symptoms (e.g. panting, drooling, reduced feed intake) (Varasteh et al., 2017). Therefore, it is of crucial importance to have preventive strategies in place before heat stress is expected to occur. Traditional strategies to manage harmful effects of heat stress have focused on reducing oxidative stress alone. Birds can develop “leaky gut” or internal damage to the intestinal track allowing for easier movement of pathogens and hampering immune system function. They also can generate larger amounts of cellular-damage-causing free radicals and may see increased blood pH, which can lead to electrolyte imbalances.
However, with the more recently uncovered mechanisms suggesting a direct effect on the GIT in mind, new heat stress strategies have a twofold approach: reducing oxidative stress and supporting gut health. Gut health can be supported through Betaine, high level copper and organic acid products especially during heat stress conditions.
What management practices can help prevent or mitigate heat stress?
Producers should take a holistic approach of feed, farm and health management to defend against heat stress. The general management practices include reducing bird density, feeding during cooler parts of the day, reducing dietary protein levels, and adjusting nutritional density, or covering water tanks and flushing warm water out of a system to provide colder drinking water. But not all of these options may make sense based on the cost or infrastructure investment. For example, refrigerated water can be challenging to supply to birds in some regions. Also, some production environments traditionally have open houses, which can be harder to regulate in terms of providing a controlled climate. In fact, open-house facilities can see a production decline of 15-20% and high mortality rates during high-heat conditions.
What role can nutrition play in helping birds deal with heat stress?
Birds eat less when exposed to high temperatures so providing more nutritionally dense feed is one dietary change to make. Additionally, supporting birds’ nutritional intake with feed additives that supply extra antioxidants, osmolytes and gut health products. Supplying trace minerals that are more bioavailable support structural, physiological, regulatory, and catalytic function. Trace minerals also play very crucial role in egg production and eggshell formation in layers especially during heat stress conditions. Several studies have shown that Selko IntelliBond trace minerals provide a more bioavailable mineral source compared to sulphate sources. The crystalline structure of this particular hydroxychloride mineral makes it less soluble and keeps it from breaking down before the mineral can be released into the proper area of the gastrointestinal tract. The reduced solubility of IntelliBond trace minerals compared to sulphate sources also helps guard against interactions with other ingredients in the feed.
How can trace mineral supplementation help support birds during heat stress?
When feed intake drops, diets need to be more nutritionally dense, and every element should be easy for the bird to use. Trace minerals are essential to maintaining bird health and production so any included in a diet for birds facing high-heat conditions need to be bioavailable and easy to access where needed. Also increasing 10 to 15% additional levels may be appropriate to ensure birds are supported. Providing the additional trace mineral nutrition can help birds maintain production levels, support shell quality and egg mass during heat stress conditions. For example, birds need zinc which is a cofactor of the enzyme carbonic anhydrase. A lack of zinc in layer diets can lead to lower levels of carbonic anhydrase, resulting in shell defects. Zinc also helps in lot of immune functions. Copper plays a role in enzyme function, reproduction, skin pigmentation and several other areas within the bird. Selenium is an important antioxidant needed to counteract the increase in free radicals and manganese also has a role to play.
What studies are being done to support the use of bioavailable trace minerals during heat stress?
A trial done in Australia with researchers from the University of New England looked at using IntelliBond in place of sulphate-based trace minerals. Laying hens faced cyclical heat stress conditions, and birds receiving diets that included more bioavailable, hydroxychloride-based trace minerals demonstrated better egg production, egg mass, improved egg FCR and better responses to high-heat conditions.
Research Postcard from Down Under: How the trace mineral source matters source to supports birds during heat stress? How much can the type of trace mineral supplied in the diet influence laying hens’ performance and quality parameters during heat stress?
A series of feeding trials were done with laying hens in Australia to address this question. Researchers at the University of New England provided 600 laying hens with one of two diets during a multi-week period of cyclical heat stress. Temperatures during the trial ranged from 31⁰C (87.8⁰F) to 22⁰C (71.6⁰F) Diets used were wheat-soy-barley-based feeds with 500 FTU phytase and supplemented with either inorganic, sulphate-based copper, zinc, and manganese trace minerals or with IntelliBond versions of the same minerals. Both types of minerals were supplied in the same amounts – 15 ppm copper, and 80 ppm zinc and manganese.
Birds were monitored for feed intake, egg FCR, egg production, egg weight, egg mass, shell characteristics, and bone strength. Overall, birds on the IntelliBond trace mineral supplemented diet saw improved egg production (Figure 1) and egg mass (Figure 2) along with a better egg FCR (Figure 3). The hen egg day production (HDEP%) improved 2.3% compared to inorganic group. FCR based on gram of egg generated was improved by 4.6 points and FCR based on a dozen eggs was better by 3.3 points. Average daily feed intake tended to be similar regardless of diet across the length of the trial but was improved for birds receiving IntelliBond trace minerals in the first 6 weeks.
Looking at egg-based results, birds receiving the IntelliBond -based supplementation generated eggs with better albumen percentage and that had lower shell reflectivity, but most egg quality parameters were similar for birds on both diets.
The type of dietary trace mineral provided did generate a reaction based on the heat stress conditions. Laying hens getting the feed supplemented with IntelliBond-based trace minerals did not have the same response to high-heat conditions. Instead, the supplementation appeared to mitigate the drop in egg production during periods of heat stress.
1. United Nations. (2022, January 19). 2021 joins top 7 warmest years on record: WMO. United Nations News. https://news.un.org/en/story/2022/01/1110022
2. Lara, L. J., & Rostagno, M. H. (2013). Impact of Heat Stress on Poultry Production. Animals: an open access journal from MDPI, 3(2), 356–369. https://doi.org/10.3390/ani3020356
About Narendra Venkatareddy
Back in 2008, Narendra Venkatareddy received his Bachelor degree from Karnataka Veterinary, Animal and Fisheries Sciences University, India focusing on Livestock and Canine species. In 2011, he completed Post Graduate Diploma in Management from Birla Institute of Management in India. From 2011 to 2017, Narendra was holding many roles in different multinational companies in the animal health and nutrition industry focusing mainly on poultry nutrition and nutrition. He worked in various functions of marketing, technical and sales support, feed additives, and technology deployment in South Asian markets. Since 2018, Narendra is part of the Global Selko Feed Additives Team in Trouw Nutrition and responsible for supporting nutritional solutions programs in all livestock species with focus on trace mineral solutions across the globe.