# Daily Variation of Body Temperature: An Analysis of Influencing Physiological Conditions
## 3 Some Factors Affecting Body Temperature and Its Circadian Rhythm
### Daily Variation of Body Temperature during the Gestation and Neonatal Period  
In some animals, such as cattle and goats, it is important to assess body temperature, which has an important circadian rhythm. In this case, the temperature has a circadianrhyth with a minimum in the morning and a maximum in the late afternoon [72]. The rotation of the Earth and its orbit around the sun cause a photoperiod, so an alternation of light and dark is the main environmental signal regulating circadian clocks and influencing circadian rhythms in organisms. In view of the above, certain physiological mechanisms, especially in female pets, such as pregnancy and lactation, alter circadian clocks and daily rhythms [73]. The above influences metabolism and consequently mammary development and lactation, particularly improved nutrient partitioning to support physiological needs during reproduction [74]. For the assessment of circadian body temperature rhythms in the goat, a 24 h measurement was taken. Measurements were taken three weeks before birth, three weeks after birth, and finally five weeks after birth. Every day, over a 24 h period, rectal temperatures in the goats were measured six times every four hours [75]. In the present study [65], in the third week before delivery, the circadian rhythm of body temperature was affected, the latter being higher in the long duration photoperiod (16 h light and 8 h dark) than in the short duration photoperiod (8 h light and 16 h dark), with a difference of 39.6 \(\pm\) 0.06 and 39.3 \(\pm\) 0.1 \({}^{\circ}\)C. At five weeks postpartum, the postpartum temperature was higher in the long-day photoperiod than in the short-day photoperiod, showing temperatures of 40.1 \(\pm\) 0.15 and 39.7 \(\pm\) 0.1 \({}^{\circ}\)C, respectively. Also, during the pregnancy period, in the cattle, [PERSON] et al. [73] show an increasing increase in the circadian rhythms of temperature and, at the same time, cortisol and serotonin in cows that were exposed to 16 h of light and 8 h of darkness for 35 days until delivery. This is due to changes in underlying circadian rhythms, such as changes in sleep close to the calving days. This is important to maintain because any interruption or mismatch in the timing of the circadian clock can cause a reduction in body temperature adaptation and lead, in cattle, to an increase in the duration of gestation. In sheep, [PERSON] et al. [76] conducted a study, relating the average temperature at 24 h before parturition and after parturition. The results showed a decrease in temperature upon landing and an increase in temperature up to twenty-four hours after delivery. This has been found in several studies of, for example, sheep or cows, where a lower temperature before delivery was found to increase after delivery. In particular, the decrease was found in the rectal temperature or on the body surface of both sheep and cows (Figure 3). The assessment of body temperature associated with the oestrus cycle may also be interesting. According to measurements taken at dawn and dusk, the temperature at dawn was lower and had a greater range than at dusk. Robustness, on the other hand, was similar [5]. During the neonatal period, a difference must be made between species with respect to achieving and maintaining the circadian rhythm of temperature. In fact, calves do not show a rectal temperature rhythm. In lambs and kids, on the other hand, a temperature rhythm is observed from the very beginning. It was noted that when a temperature rhythm was reached, the rectal temperature was higher in kids. In lambs, a different expression of the temperature rhythm was observed by [PERSON] et al. [22], even in animals born on the same day. This was caused by a different development of the mechanisms underlying the circadian rhythm [2]. As far as single lambs are concerned, these show a temperature rhythm at the fifth or ninth hour after birth. The same was true for twins that did not, therefore, show similar rhythms (Figure 4). This obviously causes a delayed acrophase.