Abstract
We determined reference levels of minerals, fatty acids, and fat-soluble micronutrients in eggs from wild Attwater's Tympanuchus cupido attwateri and two (Minnesota, Nebraska) greater prairie-chicken T. c. pinnatus populations for comparison with eggs produced by captive Attwater's prairie-chickens to help guide formulation and evaluation of captive diets. Levels of all minerals found in wild Attwater's prairie-chicken eggs were similar to those in at least one of the two greater prairie-chicken populations, but these levels frequently differed between the two greater prairie-chicken populations. Ratios for n-6:n-3 fatty acids were >3 times higher for Minnesota greater prairie-chickens, which had more access to waste grain than Attwater's or Nebraska greater prairie-chickens. Captive eggs had n-6:n-3 ratios 6.7 times the pooled wild samples, while wild eggs had higher levels of anhydrolutein, zeaxanthin, β-carotene, and total carotenoids. More magnesium, zinc, and manganese were observed in wild eggs compared with those produced in captivity. Flaxseed was added to the captive breeder diet in an attempt to lower egg n-6:n-3 ratios, along with additional carotenoids found in marigold extract. These dietary modifications successfully lowered the n-6:n-3 ratio by 46%, but this ratio was still 3.6 times higher in captive eggs, consistent with the grain-based formulation of the breeder diet. Carotenoid additions successfully raised total carotenoids, but increases were primarily for lutein and not zeaxanthin or β-carotene as intended. Variability in egg nutrient composition among the three wild populations suggests that some tolerance exists in maternal diets, but impacts to offspring fitness are unknown. Given the purported importance of maternal nutrition to fitness of embryos and neonate chicks, we suggest additional research is needed to quantify the influence of key nutrient levels on offspring fitness for both captive and wild populations.
Nutrient Profiles of Wild and Captive Attwater's and Greater Prairie-Chicken Eggs
