Seasonal changes in avian blood pressure related to age, sex, diet, confinement, and breed

Abstract

Systolic arterial blood pressure was measured four times on 219 "outdoor" adult chickens at 6-month intervals which coincided with midwinter and midsummer. Both sexes, seven diets, three types of confinement, and several breeds, strains, and ages were represented. Marked and reproducible seasonal changes in systolic pressure were observed (higher in winter, lower in summer) in essentially every group and subgroup including animals in which huddling was possible and in a selected hypertensive line. Allowance for seasonal changes permitted the following evaluation of the change of pressure with age: 12 mm Hg or 6%/year in the male, 13 mm Hg or 9%/year in the female. The observed seasonal changes were as follows: a) uncorrected for age: 10% decrease from winter to summer, 20% increase from summer to winter, both sexes; b) corrected for age: male, 29 mm Hg, and female, 22 mm Hg change, either season, or a 15% change, both sexes, either season. The average monthly environmental temperature ranged between 1.6 and 21.1 C, and within these limits, the change in systolic pressure/degree Centigrade (age corrected) was 1.6 mm Hg in the male and 1.2 mm Hg in the female.