Neonatal thermoregulation and dynamics of serum thyroid hormones in tropical breeds of goat kids

Abstract

The study was aimed at evaluating the concentration of serum thyroid hormones and diurnal trends in rectal and body surface temperatures in neonatal buck-kids and doelings. Rectal and body surface (eye, head and trunk) temperatures as well as the differences between rectal and surface (DBRS) temperatures were determined in 39 kids, having equal number of Red Sokoto, Sahel and West African Dwarf (WAD) goats during daytime nadir (07:00 h) and zenith (13:00 h) in ambient temperatures. All variables and blood samples were obtained from birth to Day 20, post-natal. Results revealed significantly (P < 0.05) lower values of morning and afternoon rectal temperatures at birth with subsequent post-natal increase, attaining higher stable values after Day 2. Morning head surface temperature decreased significantly after birth, whereas, DBRS temperatures were lower at birth and increased in subsequent days. From birth, diurnality was distinct (P < 0.05) in all body surface and DBRS temperatures, while, diurnality in rectal temperature was only observed on Days 1–8 (P < 0.05). All body temperatures (rectal, eye, head and trunk) recorded during the afternoon hours in the late neonatal life (Days 10–20) were significantly higher in WAD than Red Sokoto and Sahel kids. Buck-kids had higher (P < 0.05) values of morning rectal temperature than doelings. Circulating concentration of tri-iodothyronine was significantly lower in Sahel than Red Sokoto and WAD goat kids, whereas, the values of thyroxin were lower (P < 0.05) in Red Sokoto than Sahel and WAD kids. Similarly, lower (P < 0.05) values of tri-iodothyronine were recorded in buck-kids, while a higher (P < 0.05) level of thyroxin was recorded in doelings. In conclusion, neonatal adjustment in body temperatures of tropical breeds was influenced by thyroid hormone concentration, and the feeble cutaneous thermoregulation atbirth, contributed significantly to heat loss and gain during the morning and afternoon hours, respectively.