[Is there a predictable correlation between time of birth, birth and the puerperal period and clinical and hormonal findings in horses?].

This study aimed to investigate if there is a consistent relationship between the time of birth, birth and the post-birth period, and clinical and hormonal findings in horses. The researchers also examined progesterone and estradiol levels in the blood, the Ca/Mg ratio in the milk, as well as clinical signs of birth and post-partum period.

Methodology

The researchers conducted the study on 108 mares which are made up of 78 warm-blooded horses, 25 cold-blooded horses and 5 trotters. They:

• Examined levels of progesterone and estradiol – two hormones involved in pregnancy – in the jugular vein blood of the mares from 30 days before their calculated birthing date to 30 days after birth.
• Measured the Calcium/Magnesium (Ca/Mg) ratio in the mare’s milk using a semi-quantitative test strip.
• Recorded clinical signs and observations during the birth, parturition itself and the post-partum period.

Results

They observed that:

• The ratio of progesterone to estradiol shifted in favor of estradiol as parturition approached, indicating the onset of labour contractions, as well as signaling increased activity and regulation of hormones in the ovary.
• The “predict of the foal-test” – which measures the Ca/Mg ratio in the mare’s milk – is useful when combined with clinical observations in deciding when to induce birth.
• The color and viscosity of the mare’s milk was noted to change from grey-aqueous 48 hours prior to birth, to grey-brownish 24 hours prior, to white-yellow and viscous 12 hours prior to birth.
• Larger mares were observed to retain the fetal membranes more often than their smaller counterparts. They also produced lighter offspring with equally lighter fetal membranes, and the surfaces of the microvilli of the microcotyledons appeared to be smaller.
• The researchers concluded that disturbances in the fetus-mother relationship likely occur during pregnancy due to deficiencies in placental development, which may eventually lead to the retention of the second uterus.