To anyone in the poultry industry who's wondered if paying close attention to the details of managing breeder birds really makes any difference in the broilers, Dr. Suzanne Dougherty has an answer for you:
"Everything you do [with breeders] from start to finish can and will affect your broiler performance in some way or fashion," said Dougherty, a poultry veterinarian, speaking at the U.S. Poultry & Egg Association's Hatchery-Breeder Clinic.
Dougherty, who at the time of the clinic was director of veterinary services for Keystone Foods, told attendees at the seminar that a wide variety of breeder management factors can affect broiler performance, "in both a negative and a positive way." Many factors are critical to optimal broiler health and performance, she said.
Dougherty outlined areas of concern, ranging from the impact of body weight and nutrition of breeder birds on their offspring to vaccination programs to biosecurity and vertical transmission of disease organisms.
Body weights and variations among pullets, broiler breeders
"Managing pullet and hen body weights and CV [coefficient of variation] is critical to hen production and hatchability" and the uniformity of the broiler flock, she said. "Broiler health is directly related to breeder flock nutrition and feed consumption."
Smaller pullets and hens typically are not as healthy as the average-sized and larger hens, she said. Small pullets that are light stimulated too early have a higher risk of peritonitis which can affect hatch and chick quality.
In providing proper nutrition of pullets and achieving good body weight, many factors are critical, she said. These include the ingredients, feeding schedule and distribution of the feed. Factors such as lighting, environmental stress and control of coccidia are also important.
As pullets become hens, a host of management factors can affect body weights and the degree of variation among birds in a breeder flock, she said. These include:
- Environmental temperatures too low or high
- Lighting too early, even before sexual maturity
- Leg damage at move
- Hens not finding feed at move
- Food formulation (low energy and/or low/high protein)
- Missed or delayed feedings
"Feed management is critical to hen body weights and uniformity," Dougherty said. This includes feed restriction, which is necessary for egg production and the maintenance of proper body weight. Feed restriction is also needed to maintain good eggshell quality.
Hens that are not getting enough feed to support their bodies will lose weight, start laying smaller eggs, and may eventually stop laying, going into a molt, she said. "It's critical for hens not to lose body weight."
Hen body weights and egg size
Heavier body weights in the hens are associated with larger eggs, which typically have poorer shell quality, she said.
"There's only so much calcium she can put on the egg," Dougherty said of the hen, "so bigger eggs have thinner shells."
Eggs normally get larger as a breeder flock gets older, she said. The size of the egg, in turn, is directly correlated with the weight of the chick. "Various egg sizes can result in poor uniformity of chicks at hatch, and carry through the life of that broiler flock," she added.
Egg handling and management
The on-farm egg handling system has to be kept clean since clean eggs are critical to obtaining good chick quality and minimizing early mortality.
"You only want to send hatching eggs to the hatchery," she said. "Do not send dirty, contaminated eggs. They will explode and contaminate the clean eggs."
Vaccinating breeder birds against a variety of diseases is a complicated and expensive process, but Dougherty said poultry companies have little choice in the matter.
"Vaccine programs are one of those necessary evils," she said. "They protect the hens and the progeny."
Live vaccines are given mainly to pullets to protect them and to serve as primers for killed products that are given later on. These include vaccines for:
- Marek's disease
- Reovirus (respiratory enteric orphan virus, REO)
- Infectious Bronchitis Virus (IBV)
- Newcastle Disease Virus (NDV)
- Infectious Bursal Disease (IBD)
Vaccinations are also available for fowl cholera (Pasteurella bacteria), Salmonella and fowl pox. In addition, intestinal deworming needs to be done three or four times for the various types of worms, including round, cecal, capillaria and tape worms, she said.
Killed vaccines include IBD, REO, Salmonella, Chicken Anemia Virus (CAV), Avian Encephalomyelitis (AE) and IBD/NDV. These protect the progeny when they are most vulnerable to infection by providing maternal antibodies, she said.
Pullet and breeder biosecurity to prevent disease
Biosecurity is very important to prevention and management of disease. Dougherty called for an "all-in, all-out approach."
"If disease enters, allow for a full cleanout and no host birds to support the disease," she said.
Water systems should be kept sanitized and closed to help prevent spread of bacteria and litter should be treated between flocks to control capillaria and cecal worms. Rodent and pest control is also important.
Disease and hatchability
"Many diseases of poultry affect hatchability and can cause mortality at all stages of embryonic development," she said. These can result from disease in the flock or from organisms in the hatchery.
Many diseases are vertically transmitted from breeder to broiler, including reovirus, mycoplasma, CAV, AE and Salmonella.
Most Salmonella in chickens is not pathogenic and will not cause disease, Dougherty said, but some Salmonella enteritidis and Salmonella typhimurium will transfer to the chick from the eggshell or inside the egg and cause increased mortality from seven to 14 days of life.
Breeder intestinal microflora vertical transmission
Vertical transmission from breeders to progeny is known to occur with some organisms. Dougherty cited research showing that the first organisms to gain access to the chick gut originate from the parent. Microbes that survive in breeder facilities are carried over from one cycle to the next, serving as "seed stock" for the gut flora of the next birds to come along, as one research paper puts it.
Disease organisms that could potentially be transmitted to offspring include Clostridium perfringens, which causes necrotic enteritis; Enterococcus cecorum, for "kinky back" leg issues; and runting-stunting syndrome (RSS).
"In the future, more research and emphasis will be put on pullet and breeder intestinal flora and properly establishing the good bacteria in the intestine -- a seed, feed and weed type program," she said.
The missing vaccinations
If any proof is needed that vaccination of breeders is good for broilers, Dougherty said her former company had an unfortunate case study that makes the point.
The story began with serological tests of breeder flocks that showed titers for Newcastle disease, REO and IBD that were lower than expected. Where were the antibodies?
A close look showed that the suspicious flocks were all serviced by the same technician. The breeder manager looked at his inventory and found anomalies over a period of several months. Clearly certain things were not being done.
After an investigation, it turned out that the service tech had elected not to vaccinate the pullet flocks, said Dougherty.
In some respects, the missing vaccinations seemed to make little difference, since the IBD and REO titers in the poorly vaccinated flocks were actually as good as normally vaccinated flocks once they began to lay -- apparently stemming from field exposure to the organisms. However, one farm experienced a spike in undefined mortality in the hen house, while another saw leg issues in the breeder house. Other disease problems also occurred.
The impact carried over to the broiler progeny of the poorly vaccinated flocks, Dougherty said. Livability was below normal, and respiratory disease caused a spike in parts condemnation at the processing plant.
The company instituted new monitoring procedures to ensure this would not happen again, and the problems eased once the poorly vaccinated flocks were out of the field.