The parents of broilers are defined as broiler breeders. In contemporary poultry industry practices, there are many selection criteria for broiler breeders. Beyond selecting for future broilers, maximizing broiler breeder characteristics (i.e. reproductive success) is also important. In essence, we are not only selecting for future broilers but future broiler breeders (grandparents, parents) as well. Striking a balance between reproductive success with the appetite and growth designed for broilers can be challenging and can inadvertently compromise the welfare of broiler breeders.
Why is an Appropriate Feeding Regime Important?
Broiler breeder performance relies on being physically able to reproduce. Genetically, they have the same trait that broilers do: fast growth. This fast growth, while desired in broilers, conflicts with the selected purpose of broiler breeders. To limit this counterproductive trait, growers practice restricted feeding regimes rather than feeding ad libitum (birds are given free access to feed). There have been many discussions on which feeding regime to feed broiler breeder pullets and cockerels that ensures peak reproductive performance during the laying period. Because the rearing phase can greatly impact the laying phase, it is ideal to provide broiler breeders with the essential nutrients they need to grow in addition to maintaining a specific trend in body weight. Breeder pullets are typically given free access to feed for the first 21 days. After 21 days, broiler breeders are feed restricted based on their body weight and the breeding company’s target weight. However, feed restriction regimes mainly start between Week 2 and Week 5 of rearing. The two common feeding programs employed by flock owners in the industry are skip-a-day (SAD) and every-day (ED) feeding.
Skip-a-day (SAD) Feeding
As the name suggests, pullets and cockerels are fed every other day (ON). Days where they are not fed are called (OFF). ON days are where the birds are fed twice the daily amount to account for the OFF day. This has been the industry’s main way to maintain body weight and uniformity in broiler breeders as they grow. There are drawbacks to this method, however. On OFF days, birds display “hangry” behavior and begin to exhibit abnormal behaviors. An abnormal behavior such as excessive feather pecking may lead to bare spots on the side of hens and roosters that increase the chances of open wounds (either from mating, fighting, or unfortunate scratches on protruding sharp objects in the environment). For example, a flock that is experiencing an increase in feather pecking may see a rise in mortality cases related to wound infection or cannibalism. The abnormal behaviors and chronic hunger on the OFF days have led to welfare concerns.
Different variations of SAD feeding schedules also exist. For example, a 4:3 schedule is a fixed feed schedule where birds get feed for four days a week and skip three days a week. A 5:2 feed schedule is also common which is a combination between a 4:3 and an ED feeding where birds have either two or three consecutive feed days (feed for five days a week, skip for two).
SAD fed birds have been shown to have elevated corticosterone levels, particularly on OFF days. Chronic distress can have long-term welfare implications on broiler breeders and the broilers hatched from their eggs. Chronic distress can result in endocrine changes and has been proven to influence growth rates, immune system, behavioral traits, and birth weight of offspring in mammalian species. In chickens, studies have linked maternal stress (in this case, injected synthetic glucocorticoids in vivo to mimic maternal stress) to reduced growth rate and body weight in chicks.
Every-day (ED) Feeding
Pullets and cockerels are fed every day, generally with an increased amount of ‘filler’ material to ensure appropriate daily amount of nutrients and minerals as well as a longer feeding time. As examples, soybean, oat, and rice hulls are known filler ingredients that can be added to the feed. However, filler material is generally high in fiber and can lead to litter quality issues depending on the type. A diet with higher level of soluble fibers lead to moist and compact litter more so than insoluble fibers. ED feed is more expensive to make because of the additional cost of fillers.
ED feeding is not as common as SAD in the broiler breeder industry. There is the problem that ED feeding is not as effective in controlling body weight as SAD feeding regimes have proven to be. There is also an issue with flock uniformity under ED feeding: it is reasoned that because the SAD birds are getting a larger amount on their ON days, there is a longer opportunity for more birds to eat. Even with filler material added to diet, there isn't enough feed time for the subordinate birds to eat their fill in ED feeding programs. A lower stocking density and provision of sufficient feeder space may alleviate some of the concerns related to flock uniformity in the ED program.
Alternatives have been examined to decrease the welfare concerns associated with chronic feed restriction.
Addition of environmental enrichments
- Environmental enrichments can help prevent abnormal behaviors or reduce the extent of such behaviors
- These can come in different types
. Enrichments such as plastic strings and scattered feed can stimulate explorative pecking and foraging
- There are some concerns with the relationship between production and enrichments, however
* Cover panels and hutches have the potential to encourage hens to lay eggs on the floor and slats (higher chance of dirty and lost eggs)
* Added feed objects may disrupt the delicate balance of nutrients in the feed
Use of slow growing genetic lines
- Growth potential of slow growing broiler genotypes mean they do not exhibit the increased hunger drive as that of faster growing broiler breeders
- As such, a rigid feed restriction practice similar to faster growing broiler breeder strains is not required
- Broiler breeders are feed restricted during growth using ED or SAD feeding program
- SAD feeding subjects the birds to longer periods without feed causing chronic hunger
- ED feeding provides birds with daily access of feed but at a reduced amount of their daily need. ED feeding can come at a cost of reduced flock uniformity
- Further research to identify appropriate qualitative feed restriction methods and relevant environmental enrichments are warranted