Effects of diet and light on growth, maturation, and adrenal size of Microtus montanus

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Abstract
M. montanus born and maintained under 4 different experimental regimes were studied to 9 weeks of age. One group was raised under 18 hr. of daily illumination, the other under 6 hr. Under each photo-period some animals received a dietary supplement of sprouted wheat every 3 days (G), others every 15 days (D). G-18 males and females grew significantly more rapidly than their G-6 counterparts. Significant differences also occurred in D-18 vs. D-6 males and G18 vs. D-18 females. Significant sexual dimorphism in growth rate existed in postpubertal G-18 and D-18 animals. G-18 animals matured 1st and D-6 animals last. Under 18 hr. of illumination males developed heavier testes and females heavier reproductive tracts than their 6-hr. counterparts. G-18 males had heavier adrenals than D-18 males until puberty when this relationship became reversed. G-18 females developed significant heavier adrenals than G-6 females. Similar nonsignificant trends existed in G-18 vs. D-18 and D-18 v. D-6 females. Postpubertal G-18 females developed significantly heavier adrenals than postpubertal G-18 males. The effects of seasonal variations in diet and photoperiod on animals under natural conditions are discussed.