A LOW-crude protein diet for broiler breeders changes body composition during the rearing period, which positively affects hatchability during the first phase and egg production during the second phase of the laying period.
Poultry scientist Rick van Emous of Wageningen University & Research in the Netherlands investigated the effect of two dietary protein levels — high and low — during rearing on feed intake, body composition at the end of the rearing period and reproductive performance of broiler breeder females. A total of 2,880 day-old Ross 308 broiler breeder female chicks were placed in 36 pens and were tracked until 60 weeks of age.
To meet bodyweight targets at 22 weeks of age, average feed intake increased by 12.8% for the pullets fed the low-protein diet. At 22 weeks of age, birds fed the low-protein diet had 15% less breast muscle but 86% more abdominal fat compared to birds fed the high-protein diet, an announcement said. This resulted in a 1.3% increase in hatchability due to a decreased embryonic mortality in the first phase of the laying period (23-45 weeks of age). Moreover, birds fed the low-protein diet produced 3.6 more hatching eggs during the second phase of the laying period (46-60 weeks of age).
Van Emous noted that during the last few decades, the genetic potential of broiler breeders has increased because of selection pressure for the growth of the offspring. The growing period of broilers has decreased from 84 to 33 days to produce a broiler weighing 1.8 kg, and the feed conversion ratio decreased in the same period from 3.25 to 1.50. This selection for increased feed conversion, growth rate and body fat content has affected not only the offspring but also the parent stock (broiler breeders), van Emous said.
Optimizing body composition (more fat and less breast meat) of female broiler breeders during the rearing period might improve the persistency of reproductive performance.
The study is part of a doctoral project on body condition and nutrition in broiler breeders.
More filling diets
The U.K. Biotechnology & Biological Sciences Research Council has awarded £400,000 to researchers who will investigate how to improve the diets of broiler breeder chickens.
A team from Scotland's Rural College (SRUC), Newcastle University, The Roslin Institute and Biomathematics & Statistics Scotland will study the birds' behavior and their brain activity to establish the best possible diet to keep them feeling full for longer.
Dr. Rick D'Eath, who will be leading the project at SRUC, said, "This research will assess how the chickens are affected by different types and amounts of food. We need to understand how best to rear them from chick to adult, keeping them healthy without over- or under-feeding them."
Broiler breeders are the focus of the study because they share the fast growth potential of their offspring — meat-producing chickens — but they live much longer, SRUC explained. If broiler breeders grow too fast prior to puberty at 20 weeks of age, they may become obese, which can lead to other serious health problems. On the other hand, if their diets are too restrictive, the birds may be left feeling hungry.
There may be better ways to raise the birds from chicks onward and better diets to support their growth and the appetite they develop, D'Eath said. Before puberty, birds are fed rations, receiving as little as one-quarter to one-third as much food as they would eat if allowed to feed freely from one day of age.
A potential solution to the problem of hunger resulting from restricted feeding in broiler breeders is adding indigestible, high-fiber ingredients to their feed. These can potentially make the chickens feel more satisfied, and since they are very low energy, they shouldn't result in excessive weight gain. However, having a physically full gut is only one part of feeling satisfied and not hungry.
This project will also investigate the way different diets affect signs of hunger in the brain and the gut and in the birds' behavior in order to better understand whether they genuinely feel less hungry when fed the newly designed diets. The SRUC team will assess the behavioral aspect, while The Roslin Institute and Newcastle University will provide expertise on brain and gut physiology.
This improved understanding of hunger will be critical when the team tests how satisfied chickens feel when fed alternative diets, some of which have been tested already in other trials by the poultry industry to ensure that the birds are healthy and laying well.
"The feeding of broiler breeder chickens is a welfare concern around the world. At the end of this three-year project, we hope to inform and influence future poultry industry guidance on feeding broiler breeders, which could improve the welfare of millions of chickens around the world," D'Eath said.
Selection of poultry with high levels of natural antibodies may increase animal welfare, reduce antibiotic usage and increase profit, according to researchers at Wageningen.
"Thanks to DNA markers, we will, in the future, be capable of selecting animals with high levels of natural antibodies. Future research will help to determine whether or not this will lead to the breeding of healthier poultry," Wageningen researcher Tom Berghof said.
Enhancing disease resistance, along with a balanced increase of production and efficiency, is an important goal in poultry breeding. Berghof has started a project that aims to improve poultry health by selectively breeding for natural antibodies using DNA markers. He said using only a limited DNA marker test, an association has been established between natural antibody levels and various immune response-related genomic regions.
An increased level of antibodies lowers the risk of mortality for layers by 20%. It is believed that selecting the best candidate birds for the breeding program will improve performance and health. This will be monitored in a field test over five years, Berghof said.
"Hopefully, we can identify the DNA markers within one-and-a-half years of research and, thereafter, test the theory in field conditions. Eventually, we will be able to include this approach in the breeding programs for layers and investigate further the effects on poultry health and welfare," he said.
Berghof hopes that this will provide the poultry industry with a new tool to implement genomic selection and develop breeding strategies for improving poultry health.