A 5-yr study was conducted beginning in 1983 with 460 cows to evaluate the effects of three breeding seasons (30, 45, and 70 d in length) and two times of spring calving, March (early) and April (late), on cattle production under Nebraska Sandhills range conditions. Criteria evaluated included pregnancy and weaning percentages, calving date and distribution, cow weights and body condition at fo...

The wild ground squirrel is a typical seasonal breeder. In this study, using RT-PCR, western blot and immunohistochemistry, we investigated the mRNA and protein expressions of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) in the medial preoptic area (MPOA) of hypothalamus of the wild male ground squirrel during the breeding season (Apr...

The possibility of developing a hormone-based test to predict libido was evaluated using the response of LH and testosterone to naloxone. This test has been used to identify sexually active and inactive mature rams during the breeding season. The objective of this study was to determine whether the blood test could be used to detect differences in sexual activity of early postpubertal (29 +/- 0...

Long breeding seasons result in long calving seasons. This results in calvings distributed through a range of environmental and nutritional conditions and a disparity in calf maturity at any planned weaning time. It also results in cows entering their period of maximal nutritional requirements over the same range of environmental conditions. Attempts to increase cow and calf productivity often ...

Biological impacts of climate change are exemplified by shifts in phenology. As the timing of breeding advances, the within-season relationships between timing of breeding and reproductive traits may change and cause long-term changes in the population mean value of reproductive traits. We investigated long-term changes in the timing of breeding and within-season patterns of clutch size, egg vo...

--A field experiment, offering a choice of two prey fish of unequal sizes to foraging Bald Eagles (Haliaeetus leucocephalus), was devised. The objective of the field experiment was to determine if eagles preferred one prey item over another, and if this preference varied between breeding and non-breeding seasons. A total of 67 trials were conducted on four nesting pairs of eagles, 32 trials in ...

An increasing number of studies revealed the importance of estrogen in male reproduction. However, most research was conducted in laboratory rodents subjected to standardized environmental conditions. Therefore, seasonal regulations of estrogen pathways remain poorly understood under natural conditions. Using immunohistochemistry, the expression of several molecules involved in the functioning ...

Citation: Odom KJ, Omland KE, McCaffrey DR, Monroe MK, Christhilf JL, Roberts NS and Logue DM (2016) Typical Males and Unconventional Females: Songs and Singing Behaviors of a Tropical, Duetting Oriole in the Breeding and Non-Breeding Season. Front. Ecol. Evol. 4:14. doi: 10.3389/fevo.2016.00014 Typical Males and Unconventional Females: Songs and Singing Behaviors of a Tropical, Duetting Oriole...

Previous investigations suggest that male tropical birds have lower plasma testosterone concentrations than northern latitude species. To test whether this generalization is valid, we analyzed all currently available plasma testosterone data of tropical birds. We focused on peak breeding testosterone levels using phylogenetic and conventional statistics. Explanatory variables considered were so...

The present study was conducted to investigate the impact of breeding season on the productivity and profitability of Barki flock. Simulation technique was used based on technical coefficients derived from statistical analysis of the basic data. Basic data utilized in this study were obtained from the accumulated records collected over 34 successive breeding seasons from 1972 to 2005 of Barki s...