Feeding chickens a low-protein diet has led to a notable reduction in the environmental impact of poultry farming. However, this diet negatively impacts muscle mass, consequently affecting meat production. In this study, researchers explore the effects of supplementing a low-protein diet with amino acids, the building blocks of proteins. Results reveal the mechanism through which amino acid supplementation offsets the negative effects of a low-protein diet in chickens.
Chicken is one of the most widely consumed meats worldwide and global food demands have steadily grown over time, making poultry farming a thriving industry. However, raising chickens for meat has also contributed to global warming, mainly as a result of increased nitrogen excretion and ammonia emissions. Feeding broiler chickens (chickens bred and raised for meat production) a low-protein diet can alleviate the environmental impact of chicken meat production since it has the potential to reduce nitrogen emissions.
Why protein matters
The downside of using a low-protein diet is that it negatively affects the growth performance of broiler chicks, measured by factors such as weight gain and feed conversion ratio, which is the efficiency with which the chickens convert their feed intake into mass. Studies have shown that to ensure that there is no loss of growth performance, low-protein diets can be supplemented with amino acids, which are the building blocks of proteins. However, precisely how amino acid supplementation helps alleviate the negative effects of a low-protein diet is not entirely understood.
Underlying mechanisms
Now, in a study published in The Journal of Poultry Science, Dr Kazuhisa Honda, Editor-in-Chief – Japan Poultry Science Association, and Professor – Graduate School of Agricultural Science at Kobe University, Japan examined the mechanisms underlying the impact of amino acid supplementation on broiler chickens that were fed a low-protein diet. Explaining further about their endeavour, Dr Honda says, “Throughout the world, a protein crisis is a serious problem in the animal industry. Secondly, global warming as a result of meat production has added to these concerns worldwide. By applying our results and utilising low-protein feed, we hope to reduce N2O emissions in the environment.”
First, the researchers fed 3 groups of broiler chicks different types of food:
- a standard recommended diet,
- a low-protein diet with 15% reduced protein content and
- a low-protein diet supplemented with AAs.
Effects of diets
To see how these diets affected growth performance, they monitored parameters such as feed intake and weight gain until the chicks were 35 days old. For chicks fed a low-protein diet there was a significant decrease in body weight as well as breast and leg muscle weight, compared to those fed a standard diet. However, none of these effects were observed in chicks fed a low-protein diet supplemented with amino acids, indicating that amino acid supplementation was able to mitigate the negative effects of a low-protein diet.
Gene-level investigation
To explore these findings further, they looked closely at various genes that are involved in muscle synthesis and degradation. Real-time polymerase chain reaction analyses — a technique that detects the amplification of DNA molecules in real time — were used to examine the extent to which these genes were ‘expressed’ in different muscles. Surprisingly, the results showed that the impact of the low-protein diet was different in the breast muscle (pectoralis major) and the leg muscle (biceps femoris).
Distinct muscle responses
The pectoralis major of chicks on a low-protein diet was found to have an increased expression of the gene LC3B (microtubule-associated protein 1 light chain 3 isoform B). However, in the biceps femoris muscle of the thighs, increased expression of the genes atrogin-1, MuRF-1 (muscle RING-finger protein-1), and MyoD (myoblast determination protein 1) was observed. While there were distinct gene expression patterns for different muscle groups, all the identified genes are involved in protein degradation, suggesting that a low-protein diet induces proteolysis in muscles. Moreover, no differences were found in gene expression between chicks fed a standard diet and those fed the amino acid supplemented low-protein diet. The results not only provide an explanation for the reduced growth performance with the low-protein diet, but also indicate that amino acid supplementation alleviates these effects differently in different muscle groups.
Implications for global farming
Findings from the study have major implications for the poultry industry. As Dr Honda explains, “Our results will contribute to the development of low-protein feed for broiler chickens, which is still a major challenge in developing countries.” By doing so, it opens doors for the increased use of low-protein feed, which means lower animal production costs in the future. Moreover, these findings also address important concerns around global warming and the environmental impacts of the poultry industry. The researchers are hopeful that using low-protein feed with amino acid supplementation can reduce nitrogen emissions to the environment, promising a more sustainable and eco-friendly future for meat production.
References available upon request
