Copper (Cu), iron (Fe), and zinc (Zn) are essential trace minerals for the reproduction, growth, and immunity of mammalian herbivore populations. We examined the relationships between Cu, Fe, and Zn in soils, common plants, and hepatic stores of two wild herbivores to assess the effects of weather, sex, and population density on the transfer of trace minerals from soils to mammals during the growing season. Soils, grasses, woody browse, hispid cotton rats (Sigmodon hispidus), and white-tailed deer (Odocoileus virginianus) were sampled across 19 sites. Concentrations of Cu, Fe, and Zn in grasses and browse species were not correlated with concentrations of those minerals in soils sampled from the same areas. Leaves of woody browse were higher in Cu, lower in Fe, and similar in Zn when compared with grasses. Available concentrations of soils were positively related to liver Cu and Zn in hispid cotton rats, which was consistent with the short lives and high productivity of these small mammals that rely on grass seed heads. Interactions between soil concentrations and weather also affected liver Cu and Fe in deer, which reflected the greater complexity of trophic transfers in large, long-lived, browsing herbivores. Population density was correlated with liver concentrations of Cu, Fe, and Zn in hispid cotton rats, and concentrations of Cu and Fe in deer. Liver Cu was < 5 mg/kg wet weight in at least 5% of animals at two of eight sites for hispid cotton rats and < 3.8 mg/kg wet weight in at least 5% of animals at three of 12 sites for deer, which could indicate regional limitation of Cu for populations of mammalian herbivores. Our data indicate that supplies of trace minerals may contribute to density dependence of herbivore populations. Local population density may therefore influence the prevalence of deficiency states and disease outbreak that exacerbate population cycles in wild mammals.
Juniper (Juniperus spp.) foliage is consumed by free-ranging goats in the southwestern US. Junipers contain monoterpenes which have toxicological and pharmacological effects. We sampled 20 male Spanish goats (Capra hircus; 10 young [2-year-old] and 10 old [3-5-year-old]) from a herd selected for their propensity to consume a high (estimated breeding value [EBV] = 13.01 ± 0.20) or low (EBV = -14.76 ± 0.48) proportion of juniper in the diet to determine the ability of near infrared spectroscopy (NIRS) in detecting physico-chemical differences in animal tissues. Heart (ventricle; interior and exterior surfaces), liver (caudate lobe), and muscle (longissimus dorsi) samples as well as an entire kidney and testicle, were collected at harvest (n = 5 of each age [i.e. length of exposure to monoterpenes] and juniper EBV combination). Tissue samples were stored in whirl-pac bags at -20o C and later thawed to ~24o C for NIRS analysis. Spectra (400–2500 nm) were obtained with an ASD Field Spec using a contact probe directly through the whirl-pac sample bag. Principal component and partial least squares regression procedures were accomplished in SAS; P < 0.05 indicated statistical significance. Both age (RSQ, 0.2 to 0.6; P < 0.05) and juniper EBV (RSQ, 0.2 to 0.65; P < 0.05) were correlated with near infrared (NIR) spectral characteristics. Propensity to consume juniper was most strongly correlated with NIR spectra in testicular tissue (RSQ = 0.65, MSE = 0.25, P < 0.01), and least strongly correlated in the heart interior surface (RSQ = 0.21, MSE = 0.21, P < 0.05). Spectral correlations with propensity to consume juniper were stronger in tissues from old (RSQ ~ 0.68) than young (RSQ ~ 0.52) goats, especially in liver, kidney, muscle, and testicle. Physico-chemical differences in goat tissues were affected by genetic propensity to consume juniper, and these were detected by NIRS.
Metabolic and endocrine tissues of goats (Capra hircus) consuming juniperus species containing monoterpenes were evaluated. Monoterpenes have toxicological and pharmacological effects. We sampled Spanish goats selected for their propensity to consume above (H) or below (L) the population average for proportion of juniper in the diet as determined by fecal near infrared spectroscopy. Our objective was to determine the effect of divergent propensity to consume juniper on various tissues in adult male goats [young (2-year-old) and old (3-5-year-old)] grazing pastures containing juniper at the Texas A&M AgriLife Sonora Research Station. In June 2019, 20 animals (n = 5 of each age and juniper consumption combination) were slaughtered at the Angelo State University Meats Lab. Body weight was recorded 2 days prior to harvest. Tissue samples (i.e. liver, kidney, heart, adrenal, testicle, epididymis) were collected and weighed at the time of harvest. Tissue weights were analyzed as a proportion of body weight. Differences in proportional tissue weights between young (Y) and old (O), H and L animals were determined by analysis of variance. Body weights (kg) were 75.5 ± 4.2, 76.5 ± 6.2, 63.5 ± 1.9, and 69.0 ± 2.8 for HO, LO, HY and LY respectively. Body weight for O (76.0 ± 3.72) was greater (P < 0.03) than Y (66.3 ± 1.9). Total paired testicle, epididymal, adrenal, and heart proportional weight (g/kg) was not affected (P > 0.1) by age nor juniper consumption group. Total paired proportional weight was significantly greater (P < 0.05) in H (2.53 ± 0.09) than L (2.19 ± 0.08) for kidneys and greater (P = 0.15) in H (15.80 ± 0.75) than L (14.58 ± 0.39) for liver. High apparent consumption of juniper was associated with an increase in mass of tissues typically involved in metabolism, biotransformation, and elimination of plant secondary compounds.
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