RESEARCH ▶▶▶
Boosting turkey reproductive output
A research team in the US has received a grant of US$ 500,000 to develop strategies to overcome the constraints that the seasonal cycle imposes on the reproductive output of turkey hens.
BY NATALIE BERKHOUT I
n agricultural systems such as turkey production, the day- length-timing mechanism that regulates reproduction can impede animal production because this mechanism provides only a seasonal window when an animal is able
to reproduce, according to Paul Bartell, lead researcher of the Penn State University research team and associate professor of avian biology at the College of Agricultural Sciences. “In this research, we are seeking to identify the mechanisms un- derlying photoperiodism in the brain of turkey hens so that we can develop methods to overcome the constraints that the seasonal cycle puts on their reproductive output,” he explains. Reproduction in turkeys is initiated by increased daylength and becomes limited by the onset of ‘broodiness’, eventually resulting in the termination of egg laying. Hens lose their sensitivity to the effects of long days which stimulate repro- ductivity, even under ever-increasing daylengths. Loss of
productivity is costly as the birds must be cared for until they come back into production again.
Discovering the turkey brain In birds, photoperiodic information is sensed directly in the brain by specialised photoreceptors. Scientists have suggest- ed several brain areas where these photoreceptors may be housed, although the precise site or sites of these photo- receptors is, in fact, unknown, says Bartell, whose research team will attempt to discover the neuronal mechanisms and hypothalamic structures involved in the photoperiodic regulation of reproduction in turkey hens. During the study, researchers will compare these brain areas prior to photoperiodic activation, during egg laying and dur- ing broodiness to understand how the brains of turkey hens change to regulate the reproductive cycle. These findings will pave the way towards the development of strategies to allevi- ate production inefficiency due to the limited laying period resulting from photoperiodic insensitivity. “We will use immu- nohistological, autoradiography and MRI techniques to iden- tify the brain areas responsible for light-sensing and the neu- ronal pathways that are activated during photostimulation to carry photic information to the pituitary,” says Bartell. “We will also employ electrophysiological techniques to understand the type of neuronal signals produced and the neurons in- volved in their production to provide a target for the future modulation of reproductive activity.”
Neurobiological mechanisms for measuring daylength regulate reproduction in turkeys and provide a seasonal window when the bird can reproduce.
34 ▶ POULTRY WORLD | No. 7, 2021
Significant economic impact This research not only has the potential to make a substantial contribution to animal scientists’ understanding of photoperi- odism and the seasonal regulation of reproduction, but its re- sults could have a significant economic impact on the industry. An average breeder hen lays for approximately 28 weeks, pro- ducing up to 130 eggs. In a typical commercial operation with 25,000 breeder hens, postponing the end of egg-laying by 2.5 weeks to allow 10 additional eggs per hen to be laid – at a value of about US$ 1 per fertile egg – would yield US$ 250,000 in additional revenue per operation. The grant for this study, which will be conducted primarily at the Penn State Poultry Education and Research Center and at the Huck Institutes of the Life Sciences, was provided by the National Institute of Food and Agriculture of the US Department of Agriculture.
PHOTO: BERT JANSEN
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