Changes in southern Piedmont grassland community structure and nutritive quality with future climate scenarios of elevated tropospheric ozone and altered rainfall patterns.

Forage species common to the southern USA Piedmont region, Lolium arundinacea, Paspalum dilatatum, Cynodon dactylon and Trifolium repens, were established in a model pasture system to test the future climate change scenario of increasing ozone exposure in combination with varying rainfall amounts on community structure and nutritive quality. Forages were exposed to two levels of ozone [ambient (non-filtered; NF) and twice ambient (2×) concentrations] with three levels of precipitation (average or ±20% of average) in modified open-top chambers (OTCs) from June to September 2009. Dry matter (DM) yield did not differ over the growing season between forage types, except in primary growth grasses where DM yield was higher in 2× than NF treatment. Primary growth clover decreased in nutritive quality in 2× ozone because of increased concentrations of neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). Re-growth clover exhibited the largest decrease in nutritive quality, whereas grasses were not adversely affected in 2× ozone. Re-growth grasses responded positively to 2× ozone exposure, as indicated in increased relative food value (RFV) and percentage crude protein (CP) than NF-exposed re-growth grasses. Effects of precipitation were not significant over the growing season for primary or re-growth forage, except in primary growth grasses where DM yield was higher in chambers with above average (+20%) precipitation. Total canopy cover was significantly higher over the growing season in chambers receiving above average precipitation, but no significant effects were observed with ozone. Results indicate shifts in plant community structure and functioning related to mammalian herbivore herbivory in future climate change scenarios.

Distribution of bovine viral diarrhoea virus antigen in persistently infected white-tailed deer (Odocoileus virginianus).

Infection with bovine viral diarrhoea virus (BVDV), analogous to that occurring in cattle, is reported rarely in white-tailed deer (Odocoileus virginianus). This study evaluated the distribution of BVDV antigen in persistently infected (PI) white-tailed deer and compared the findings with those from PI cattle. Six PI fawns (four live-born and two stillborn) from does exposed experimentally to either BVDV-1 or BVDV-2 were evaluated. Distribution and intensity of antigen expression in tissues was evaluated by immunohistochemistry. Data were analyzed in binary fashion with a proportional odds model. Viral antigen was distributed widely and was present in all 11 organ systems. Hepatobiliary, integumentary and reproductive systems were respectively 11.8, 15.4 and 21.6 times more likely to have higher antigen scores than the musculoskeletal system. Pronounced labelling occurred in epithelial tissues, which were 1.9-3.0 times likelier than other tissues to contain BVDV antigen. Antigen was present in >90% of samples of liver and skin, suggesting that skin biopsy samples are appropriate for BVDV diagnosis. Moderate to severe lymphoid depletion was detected and may hamper reliable detection of BVDV in lymphoid organs. Muscle tissue contained little antigen, except for in the cardiovascular system. Antigen was present infrequently in connective tissues. In nervous tissues, antigen expression frequency was 0.3-0.67. In the central nervous system (CNS), antigen was present in neurons and non-neuronal cells, including microglia, emphasizing that the CNS is a primary target for fetal BVDV infection. BVDV antigen distribution in PI white-tailed deer is similar to that in PI cattle.

Concentrations of insulin-like growth factor-I in adult male white-tailed deer (Odocoileus virginianus): associations with serum testosterone, morphometrics and age during and after the breeding season.

Our understanding of insulin-like growth factor-I (IGF-I) in cervids has been limited mostly to its effects on antler development in red deer (Cervus elaphus), roe deer (Capreolus capreolus), fallow deer (Dama dama), and pudu (Pudu puda). Although IGF-I has been found to play a critical role in reproductive function of other mammals, its role in reproduction of deer is unknown. The objectives of the present study were to determine if serum levels of IGF-I change during the breeding season, assess whether age influences serum IGF-I, compare levels of IGF-I measured during and following the breeding season, and determine if IGF-I is associated with body and antler characteristics in free-ranging adult, male white-tailed deer (Odocoileus virginianus). We collected serum and morphometric data from hunter-harvested and captured white-tailed deer to investigate these objectives. Mean level of serum IGF-I during the breeding season was 63.6 ng/ml and was greatest in deer between 2.5 and 5.5 years old (57.4-79.9 ng/ml). Levels of serum IGF-I decreased by approximately 40% as the breeding season progressed, but levels were less in deer following the breeding season (34.6 ng/ml). Both body and antler size were associated positively with IGF-I when controlling for age. Serum testosterone was also associated positively with IGF-I. Levels of serum testosterone during the breeding season generally increased with age from 4.82 (1.5 years old) to 18.79 ng/dl (5.5 years old), but decreased thereafter. These data suggest that IGF-I may be an important hormone in breeding, male white-tailed deer.

Major-histocompatibility-complex-associated variation in secondary sexual traits of white-tailed deer (Odocoileus virginianus): evidence for good-genes advertisement.

Good-genes hypotheses predict that development of secondary sexual characters can be an honest advertisement of heritable male quality. We explored this hypothesis using a cervid model (adult, male white-tailed deer, Odocoileus virginianus) to determine whether antler development could provide an honest signal of a male's genetic quality and condition to adversaries. We compared antler, morphometric, hormonal, and parasitic data collected from hunter-harvested deer to characteristics of the Mhc-DRB (Odvi), the most widely studied gene of the major histocompatibility complex (MHC) in Artiodactyla. We detected associations between genetic characteristics at Odvi-DRB and antler development and body mass, suggesting that antler development and body mass may be associated with pathogen resistance in deer and thus may be an honest signal of genetic quality. We also detected associations between Odvi-DRB characteristics and serum testosterone during the breeding season, suggesting that certain MHC characteristics may help deer cope with stresses related to breeding activity. In addition, we observed a negative relationship between degree of antler development and overall abundance of abomasal helminths. Our observations provide support for the hypothesis that antler development in white-tailed deer is an honest signal of quality.

A decade since "diversification of ruminants": has our knowledge improved?

In his landmark 1989 paper, R.R. Hofmann classified ruminants into three categories based upon digestive anatomy and preferred forages, and proposed that divergence of feeding strategies among ruminants is a result of morphological evolution of the digestive tract. Because of the hypothetical nature of these views and the ingrained beliefs that they challenged, several papers were published that reported tests of Hofmann's predictions. The consensus among these papers was that Hofmann's predictions were inadequate. I describe the experimental evidence that has been put forth in opposition to the ruminant diversification hypothesis and contend that we have failed to adequately test Hofmann's predictions.