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Research Traces Broiler Health To Hen Diets
MISSISSIPPI STATE -- Better eggs mean better broilers, a fact that prompted one Mississippi State University researcher to look at what a hen must eat to lay these good eggs.
Mississippi's $1.5 billion poultry industry is the state's largest agricultural commodity. When even a small improvement is made in this business, the result is seen in millions of dollars.
David Peebles, poultry science researcher with the Mississippi Agricultural and Forestry Experiment Station, recently completed studies of how different breeder hen diets affect the eggs they lay and ultimately the broilers that hatch.
"The research deals mostly with the fat we add to poultry diets," Peebles said. "We fed corn oil, poultry fat and lard to these hens in different concentrations. We looked at its effect on the egg and followed that through to the broiler."
Fat added in breeder diets is used to increase their level of energy. The MAFES research found that the level and type of fat in the diet have separate, recognizable effects.
"The work that has been done up until now hasn't really separated out the effects of the types and amounts of dietary fat," Peebles said. "Previous research looked at overall effects, but we identified their individual effects."
Peebles researched how the hen's diet affected egg quality, the newly hatched chick's health and viability and the ready-for- slaughter broiler.
"Hens fed a higher percentage of fat and higher added levels of saturated fats laid eggs with thicker shells that allowed less movement of gas through the shell than those hens fed diets with lower levels of added fat and higher amounts of unsaturated fat," Peebles said.
The research noted that lower amounts of dietary fat with lower saturation allowed the egg to better sustain the growing chick. Thicker shells, the result of high fat diets, make the eggs less hatchable.
"You want to have a shell that is sufficiently strong but allows a sufficient exchange of gas," Peebles said.
Peebles also noted that hens fed higher fat diets actually produced fewer eggs.
Attention then turned to the contents of the egg as researchers looked at the yolk, albumen and weight.
"High dietary energy decreased the percentage of albumen in the egg without significantly altering its ratio to yolk," Peebles said. "When you start altering egg components, you're affecting the nutritional status of the developing chick."
Peebles also studied the developing embryo from the perspective of composition, and body, organ and yolk sac weights and found no difference that could be traced to breeder hen diets. The next significant difference he found was in the growing broiler after hatching.
"The rate of growth in the first 21-days was faster in those broilers that hatched from eggs laid by the hens fed corn oil, the lower-saturated fat," Peebles said. "This is surprising because we didn't see any immediate effects in the embryo, but we do see effects after they hatch."
The downside, however, is that the broilers had a poorer feed conversion ratio from 22 to 42 days old. This ratio compares the amount of feed taken in to the weight gained.
The final study looked at the broilers' weight at slaughter. Again, the less saturated fat from corn oil out-performed the lard.
The overall conclusion was that corn oil in breeder hen diets at an additional level of 1.5 percent is useful in producing quality eggs and broilers which gain weight better.
Results of this study are being published in May, and Peebles anticipates they will be immediately useful to the poultry industry.
"I think the nutritionists that formulate diets for companies will start looking in a little more detail at the types and levels of fats they use as energy sources in their poultry diets," Peebles said. "They'll be better able to tailor diets for the specific needs of flocks."