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Guanidino acetic acid (GAA) supplementation to manage broiler heat stress

09 August 20226 min reading

Heat stress has the potential to significantly impact the performance and therefore the profitability of modern broilers. By understanding the metabolic and physiological effects of heat stress, we can see the potential for GuanAMINO® supplementation to alleviate these negative effects. Production trials confirm that GAA supplementation is a relevant strategy for producers to combat the negative economic effects of heat stress in broiler production.

Heat stress is a major challenge for poultry producers around the world. High environmental temperature and relative humidity reduces feed intake, impairs growth and increases mortality. The result is a significant reduction in performance and profitability. The poultry industry continues to look for innovative ways of alleviating the negative effects of heat stress and avoiding the consequent economic losses.  


Fig 1. Creatine demand increases in heat stressed broilers


Research into the metabolic and physiological effects of heat stress in birds has identified the pivotal role of creatine (CRE) in energy homeostasis. Exposing birds to chronic heat stress increases the cellular energy requirements of broilers and at the same time negatively impacts mitochondrial adenosine triphosphate (ATP) generation (Akbarian et al., 2016). CRE is directly involved in muscle energy buffering system and is important for ATP replenishment and the levels of phosphocreatine and glycogen in muscle tissue. 

Heat stress conditions are known to lower energy intake, reduce efficiency of energy utilization and decrease cellular ATP production in poultry. As a consequence, the energy supply from CRE-phosphate buffer plays a pivotal role for maintaining bird performance and health (Fig 1). 

The availability of CRE in turn depends on the supply of guanidine acetic acid (GAA) which is its only immediate metabolic precursor. Research has already confirmed that GAA supplementation can indeed improve cellular energy status owing to the pivotal role of creatine (CRE) in energy homeostasis (Majdeddin et al., 2020). This finding highlights the potential application of GAA in broilers under heat stress conditions.


CRE SOURCES

CRE and CRE phosphate are the key elements for energy metabolism in all living cells, particularly in muscle and brain cells. The constant turnover of CRE to creatinine (CREAN) is an irreversible process and the metabolic end product is excreted in the urine, so there is a continuous need to replenish CRE.

GAA is synthesized from dietary arginine (Arg) and glycine (Gly) in the kidneys (Fig. 1). In addition, under heat stress, Arg may be utilized for nitric oxide (NO) synthesis. NO is an important molecule for vasodilation and aids in glucose transport during muscle contraction indicating that Arg requirement would be high in broilers under heat stress conditions (Esser et al., 2017). 


It is estimated that only around two thirds of the daily creatine requirement of broilers can be met through endogenous synthesis by the bird’s own metabolic pathways; the remaining third must be obtained from feed. To further complicate the situation, plant-based feed ingredients do not contain any GAA or creatine and thus cannot help meet CRE shortfall. Feed based on animal products, such as fish, meat and bone meal, does contain GAA, creatine, and creatinine, but there is a huge variation in how much of these ingredients is present. In addition, meeting the need for additional CRE through animal byproducts is also limited in some countries as a result of import bans.

GAA supplementation (GuanAMINO®) has been shown to increase CRE and CRE-phosphate levels in broiler tissues and to spare metabolic Arg. Supplementing feeds with GAA, is an obvious nutritional strategy in commercial broilers for optimizing energy homeostasis and production performance in broilers and for alleviating heat stress. So how does it perform in practice?

GAA BENEFITS IN BROILERS DURING HEAT STRESS

A growth performance study was conducted in Iran to evaluate the effects of GAA supplementation in broilers subject to heat stress conditions (Majdeddin et al., 2020). In this feeding trial, a total of 720 Ross 308 male broilers were randomly distributed to 3 dietary treatments; 12 groups per treatment consisting of 20 birds per group. Dietary treatments were a control diet, and the same diet supplemented with 0.06% or 0.12% GAA. The trial lasted 39 days, including starter (d 0 to 10), grower (d 11 to 25) and finisher (d 25 to 39) phases. Broilers were raised in an environmentally controlled facility maintained at 34ºC on day 0 and linearly reduced to 22ºC by day 25. Birds were then exposed to chronic cycle heat stress during the finisher phase. Daily temperature was gradually increased to 34ºC between 8 to 9 am and maintained for 7 hours, while relative humidity was kept between 50 to 60% by water spray. 

The results from this trial demonstrated that diets supplemented with 0.06% or 0.12% GAA showed 4 points improvement in FCR compared to non-GAA supplemented birds (Fig 2. 1.44 or 1.43 vs. 1.48). Similarly, birds that received GAA-supplemented diets had reduced mortality compared to the non-GAA group (6.7% or 5.0% vs. 9.2%, respectively). Analysis of breast muscle at d 39 showed that phosphocreatine, free CRE, total CRE, and PCr-to-ATP ratio levels were increased in birds fed higher GAA diets (Table 1). Thus, it can be seen that GAA supplementation improved production performance, survival rate and breast muscle energy status in broilers subjected to chronic cyclic heat stress.

IMPROVEMENT IN FCR WITH GAA SUPPLEMENTED DIETS

Another study, conducted during the summer period at Bangladesh Agricultural University, demonstrated that 0.06% GAA supplementation improved FCR by 4 points and body weight gain by 26g compared to control birds. In this study, 250 day-old Cobb 500 broilers were randomized to two different dietary treatments: a control diet (no GAA) and a 0.06% GAA supplemented diet. There were 5 groups per treatment with 25 birds per group. At the end of the 35-day trial period, two birds from each group close to pen average weight were sacrificed to determine carcass yield and abdominal fat. Both body weight gain and FCR (Fig 3) significantly improved in the broilers fed the GAA supplemented diet. As well as improving FCR by 4 points, GAA supplementation reduced abdominal fat by 46% compared to control (15.6g vs. 28.8g). 

SUMMARY

Heat stress has the potential to significantly impact the performance and therefore the profitability of modern broilers. By understanding the metabolic and physiological effects of heat stress, we can see the potential for GuanAMINO® supplementation to alleviate these negative effects. Production trials confirm that GAA supplementation is a relevant strategy for producers to combat the negative economic effects of heat stress in broiler production.

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