Association between the Area of the Highest Flank Temperature and Concentrations of Reproductive Hormones during Pregnancy in Polish Konik Horses-A Preliminary Study

Abstract

Determination of the pregnancy status is one of the most important factors for effective pregnancy management. Knowledge of the stage of pregnancy is important to interpret many of the reproductive hormones' concentrations, including progesterone (P4), estrone sulfate (E1S), 17-ß estradiol (E2), and relaxin (REL). However, it is limited in wildlife or captive equids that cannot be handled. Reproductive hormones affect regional blood flow, the proliferation of tissues, and local metabolism intensity. Therefore, this preliminary study aimed to assess changes in thermal features of the abdomen lateral surface and concentrations of reproductive hormones in Polish native pregnant mares. The study was carried out on 14 non-pregnant and 26 pregnant Polish Konik mares during eleven months of pregnancy. Infrared thermography was conducted to image the lateral surface of mares' abdomen (Px1) and flank area (Px2); P4, E1S, E2, and REL concentrations in serum were also determined. The evidence of the association between the area with the highest temperatures (Area of Tmax) and serum concentrations of P4 (the slope = 1.373; p = 0.9245) and REL (the slope = 1.342; p = 0.4324) were noted dependent across months of pregnancy. Measures of superficial body temperatures were found to change monthly, similarly to ambient temperatures, with no evidence of coincidence with changes in reproductive hormone concentrations. Individual thermal characteristics of the lateral surface of the abdomen differed between pregnant and non-pregnant mares in other periods. Differences in maximal and average temperature and Area of Tmax were observed from the sixth month of pregnancy, and those in minimal temperature were observed from the eighth month.

Keywords: Konik Polski; estrogens; gestation; progesterone; relaxin; thermography.

Figure 1

Thermal images of the lateral surface of the abdomen of the pregnant mare. Rainbow HC palette with marked Px1 and Px2 (A). Gray palette with red annotated areas at a certain temperature (B). Gray palette with yellow annotated areas at a certain temperature in the pixel counting procedure (C). The counted pixels with non-zero value (D). Abbreviations: Px1, the whole area of the lateral surface of the abdomen; Px2, the flank area of the lateral surface of the abdomen.

Figure 2

Thermal images in gray palette of the mare. The area with the highest temperatures in the range of 3 °C (Area of Tmax) marked in red in the following months of pregnancy: third (A), fourth (B), fifth (C), sixth (D), seventh (E), eighth (F), ninth (G), tenth (H), and eleventh (I).

Figure 3

Linear regressions of estrone sulfate concentration in the serum and selected thermal features of the lateral surface of the abdomen in pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 4

Linear regressions of estrone sulfate concentration in the serum and selected thermal features of the lateral surface of the abdomen in non-pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 5

Linear regressions of 17-ß estradiol concentration in the serum and selected thermal features of the lateral surface of the abdomen in pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 6

Linear regressions of 17-ß estradiol concentration in the serum and selected thermal features of the lateral surface of the abdomen in non-pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 7

Linear regressions of progesterone concentration in the serum and selected thermal features of the lateral surface of the abdomen in pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 8

Linear regressions of relaxin concentration in the serum and selected thermal features of the lateral surface of the abdomen in pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).

Figure 9

Linear regressions of progesterone concentration in the serum and selected thermal features of the lateral surface of the abdomen in non-pregnant mares: the maximal temperature in Px1 and Px2 (A); the area with the highest temperatures in the range of 3 °C (B); the average temperature in Px1 (C); the average temperature in Px2 (D); the minimal temperature in Px1 (E); the minimal temperature in Px2 (F).