Research is showing how to effectively adjust amino acid levels in layer pullet diets, maintaining birds’ longevity and egg production without adding cost.
Although there has been extensive research on amino acids in layers, little of this research has focused on pullets during the rearing phase, said Jo Ann Chew, University of Alberta graduate student, at the 2024 Poultry Science Association annual meeting. This needs to change, she said, especially given that the industry is looking to extend the laying period “to 100 or even 120 weeks of age,” with birds responsible for 500 eggs in their lifetime.
“We need to start thinking of how we raise our pullets and consider them as an investment phase, whereby if we help them grow well from the start, we can prepare them and set them up for a successful lifetime of egg production,” she stressed.
Putting diets to the test
With that in mind, Chew’s team developed a study to explore the impact of different levels of amino acids in the diets of two laying-hen breeds (Bovans Brown and Babcock White), looking specifically at bodyweight, feed intake and egg production.
Using a precision feeding system that monitored and allocated feed to each individual bird, they fed the pullets six diets with varying levels of amino acids according to the ideal protein concept: All essential amino acids are formulated in the same ratio to digestible lysine.
The researchers also carried out two choice tests with both of the breeds, in which birds could choose either 60%, 80% or 100% of recommended amino acids, or 70%, 90% and 110%.
The treatments took place from 0 to 18 weeks. Afterward, the scientists fed the birds a regular commercial diet until 30 weeks.
Real-world implications
At the 9th week of age, birds’ feed preferences differed in the choice tests. Brown pullets ate more of the 100% recommended amino acids diet than the 60% diet, while white pullets ate more of the 100% and 110% diets than the 60% diet.
This finding suggests that the birds may be able to distinguish between different amino acid levels in diets, Chew explained, with them choosing higher levels during the grower phase.
After analyzing the impact of diet on bodyweight, the researchers concluded that the recommended digestible lysine levels in breeder guides may be much higher than what is needed to achieve the desired weight-gain curve — closer, in fact, to what is recommended by the National Research Council.
“Putting everything together, what we observed tells us that, perhaps, what we feed the pullets during the rearing program has quite a small effect on layer performance, provided that their minimum requirements are met and they achieve maximum bodyweight by the time of photostimulation,” Chew explained.
The team also saw that neither amino acid levels nor choice of diet significantly impacted egg production at 30 weeks of age or age of first egg. With diets in the study containing as low as 60% of recommended levels of amino acids, this provides some food for thought for producers, Chew noted.
“Our study’s findings suggest that there is a potential for us to reduce amino acid levels in pullets’ diets,” she added. “From a broader perspective, this could reduce ingredient costs for the producers as well as excess nitrogen excretion on the environmental front.”