Managing What You Can’t See

The strong emphasis on increased breast yield in broilers has resulted in a broiler breeder that is increasingly difficult to manage.  Genetic selection over the last 50 years has resulted in the modern broiler being 200 per cent heavier than the typical commercial strain used 35 years ago. To maintain egg production, breeders cannot be “allowed” to express their incredible genetic potential for growth and thus their bodyweight and rate of body-weight gain must be tightly controlled.

The goal is to have a uniform bodyweight (BW) in the breeder flock at time of photostimulation, and this requires a detailed attention to management.  
 
Martin Zuidhof of the University of Alberta, speaking to a group of broiler breeder producers at the 2011 Saskatchewan Industry Poultry Conference, says the biggest complaint he hears from technical service staff is a lack of BW uniformity at time of photostimulation.  If the target BW is not there at time of photostimulation, “it’s like a race, and those birds with a lower BW get left behind and never catch up,” he says.

The difficulty lies in the fact that the birds are competing for a limited resource – feed. To control BW gain, a common practice is to employ skip-a-day feeding. However, this results in a scenario Zuidhof described as “like rice being dropped in a famine-stricken area.”  Although there has been criticism concerning feed restriction in breeders, its purpose is to manage follicle development, the precursor of egg production.  Feed (or specifically, the nutrients within feed) has a direct effect on the hormonal regulation of the birds. Ad lib feeding results in a loss of hormonal regulation, and the result is what’s known as a “double hierarchy,” or more simply, twin follicles (two eggs). If these follicles are ovulated together, there is not enough oxygen available for embryo survival.  If ovulated separately, one of the follicles is without a shell since the shell gland requires 18 to 20 hours to lay down a shell.

Although feed restriction will improve flock uniformity, Zuidhof says that there are trade-offs: University of Alberta research show that it increases the fat stores, decreases muscle weight and average egg weight, and doubles the size of the liver on non-feed days. It’s also a welfare issue.

In a study conducted by his UofA colleagues Prof. Frank Robinson and graduate student Erica Holm, skip-a-day, scatter, fibre-diluted and sorted feeding methods were studied. In terms of achieving flock uniformity at photostimulation, the sorting method was found to be the best. This involved separating the smallest birds, isolating them from the others and providing them with additional feeding space. Although this method may not be practical for producers, it has been done with success in breeder flocks in Brazil and India, says Zuidhof. Scatter feeding and skip-a-day also improved flock uniformity at photostimulation.

Zuidhof says there is much that a producer can do to manage BW uniformity and egg production with some basic principles that take the bird’s metabolism into consideration (see sidebar). Weigh the birds frequently; BW gain is an indicator of metabolic status and should be used to make decisions regarding feed allocation, he says. He says by weighing two times per week, a much tighter growth curve can be achieved. “We may have more flexibility than we think when manipulating growth curves,” he says. Slow and steady wins the race, he says.  Make feed increases as small and as frequent as possible. If the birds are growing on target, they are in a positive energy balance and will prioritize nutrients toward egg production. He also pointed out that producers should stimulate sexual maturity by changing daylength, and not the amount of feed. 

Zuidhof says he’s currently performing what he calls a new “paradigm” in feed research: feeding based on the composition of the feed.  For example, he questions whether or not the current recommendation for protein is too high, as it may result in a diversion of nutrients from egg production to breast muscle production.  By changing the protein:energy ratio, breeder hens may have better nutritional support for the growing embryo. He’s also working on a proprietary feeding system that manages individual hens by providing the right amount of feed to the right bird at the right time.

Zuidhof told producers to remember that with breeders, it’s follicles that are being managed, something that they can’t see. It’s also important to have feedback.  “Managing broiler breeders without it is like driving drunk,” he says.