Changes in Cholesterol, Triglycerides and Body Composition in Pregnant Mares
Authors: Mazzo Hortencia Campos , Nogueira Carlos Eduardo Wayne , Patten Ruth , Noronha Henrique dos Reis , Silva Gabriela Castro , Curcio Bruna Da Rosa 
Published: June 2021

Background: Mares are very different from other species during pregnancy, and studies on the physiological changes of this period are important. During late pregnancy, the distribution of weight and body fat are often used as indicators of adequate nutrition. This is a physiological period that results in an increase in metabolic demand. There is a tendency for the Criollo breed to have a higher body condition score that becomes more evident during pregnancy, a period when mares tend to gain more weight. The current study monitored serum cholesterol and triglyceride levels in pregnant mares during late gestation to determine a possible correlation with the distribution of fat or body weight.Materials, Methods & Results: Four body parameters of thirty-four Criollo-type mares in late gestation were evaluated: body weight measured with a weight scale, body weight using a commercial weight tape, total body fat and fat thickness and the serum levels of total cholesterol and triglycerides. The fat thickness was measured in an ultrasound device and the prediction of total body fat was calculated using an equation. According to the days prior foaling, biometric monitoring and blood collection were carried out in five periods: F-90 (± 90 days prior to foaling) n = 33; F-60 (± 60 days prior to foaling) n = 33; F-30 (± 30 days prior to foaling) n = 31; F-15 (± 15 days prior to foaling) n = 29 and Foaling (at day of foaling) n = 14. Mares were monitored daily and accompanied foaling was also performed, ensuring collection at the right time. Comparisons of means were performed between variables in addition to the Pearson correlation test. Statistical significance was established at P < 0.05. There was no difference in relation to the period in body composition measurements (P > 0.05). A strong positive correlation was observed between the average weights (P < 0.001). The fat thickness showed a correlation between the weights (P < 0.01). There was no correlation with body composition (P > 0.068). There was a strong positive correlation between weights (P < 0.001). In addition, differences in total cholesterol levels (P = 0.0016) were observed, with higher levels found in the Foaling period. The same was not observed for triglyceride levels (P = 0.443). There was no correlation between blood variables in this period (P > 0.191). There was also no correlation with the body composition (P > 0.068).Discussion: The absence of difference between the periods in relation to the weight measures and the correlations existing in these measures is related to the period in which they were collected, since the maximum relative weight of the foal is reached in ten months, causing the mare's weight stability. Interestingly, an unexplained increase in total cholesterol levels was found on the day of foaling. As the same change in triglycerides was not observed and there was no change in the diet or feeding behavior of the mares, the effects of the diet can be excluded in this case, which requires further studies to explain this result. Our hypothesis is that this increase is linked to hormones that tend to change in this pre-delivery period and that have their metabolism strongly linked to cholesterol levels. Levels of body fat and mare weight can therefore be correlated in the late gestation, allowing for their use as indicators of adequate nutritional and energy reserves.