Effects of Chronic Heat Stress on Reproductive Hormones in West African Dwarf Goats in Ondo State

Thermal stress is a major physiological challenge confronting small ruminant production in Nigeria's tropical regions, with documented effects on reproductive performance in goats. The West African Dwarf goat, indigenous to the humid forest zones including Ondo State in the South West, is particularly susceptible to heat-induced hormonal disruptions. This study investigated the effect of chronic heat stress on circulating levels of luteinising hormone, follicle stimulating hormone, progesterone, and oestrogen in female West African Dwarf goats. Thirty adult does were divided into two groups: a heat-stressed group (maintained at 35 to 40 degrees Celsius for six weeks using climate-controlled chambers) and a control group maintained at thermoneutral conditions of 20 to 25 degrees Celsius. Blood samples were collected weekly and serum hormones were quantified by enzyme-linked immunosorbent assay. Animals in the heat-stressed group showed significant reductions in LH and FSH concentrations by week three of the experiment, with subsequent declines in oestrogen and progesterone levels. Rectal temperatures and respiratory rates were significantly elevated in heat-stressed animals compared to controls. Oestrous cycle irregularities were also recorded via vaginal cytology. These findings underscore the need for shade infrastructure and nutritional interventions during hot seasons to protect reproductive output in goat farming systems across southern Nigeria. The study contributes practical knowledge for improving small ruminant management under climate variability. Keywords: heat stress, goat, reproductive hormones, WAD, South West Nigeria.