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Title: Physiological responses to divergent selection for phytate phosphorus bioavailability in a randombred chicken population

item McMurtry, John

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2008
Publication Date: 12/1/2008
Citation: Sethi, P.K., McMurtry, J.P., Pesti, G.M., Aggrey, S.E. 2008. Physiological responses to divergent selection for phytate phosphorus bioavailability in a randombred chicken population. Poultry Science. 87:2512-2516

Interpretive Summary: Phosphorus is one of the more important minerals essential for normal growth, development and metabolism. The primary dietary source of phosphorus are the cereal grains. Unfortunately, poultry are unable to fully utilize this source of phosphorus since it is chemically bound to phytic acid. Domestic poultry do not have the metabolic enzymes necessary for completely breaking down phytic acid. Therefore, a large percentage of the phosphorus ends up being excreted. Not much is known about the hormonal control of phosphorus absorption and metabolism in birds. This study was conducted to evaluate several different hormones in the blood of two lines of broiler chickens that were divergently genetically selected for phosphorus utilization. The results strongly suggest that the thyroid hormones are an indirect indicator of phosphorus utilization in growing chickens. The results of this study will be of general interest to other scientists and poultry geneticists.

Technical Abstract: An investigation was conducted to study insulin-like growth factor (IGF) I, IGFII, insulin, glucagon, recombinant human leptin, triidothyronine (T3) and thyroxine (T4) levels in a randombred chicken population divergently selected for phosphorus bioavailability (PBA). There were also differences in growth and feed efficiency between the two lines. Insulin like growth factor I, IGF II and T3 were significantly higher in the high PBA line compared to the low PBA line whereas the reverse was true for glucagon. There were no correlations between the IGFs and PBA in both lines suggesting that the line differences may be the result of factors other than PBA. There was a significant correlation between PBA and T3, and the low line and between PBA and T4 in the high PBA line. Thyroid hormone levels may be an indirect indicator of PBA in growing chickens. The physiology of the divergent lines may be different. Glucagon and IGF I have a different relation with FCR in the high PBA line than the low PBA line.