The influence of mare's lactational status during early pregnancy on metabolism of foals up to 28 days of age

The influence of a mare's nutrition on the fetus plays a significant role in future health, growth and performance, affecting insulin and glucose control systems. When maternal nutrition is altered through concentrate supplementation, higher insulin concentrations are required to maintain euglycemia in the mare, which can lead to metabolic reprogramming in the foal. The "easy keeper" condition (obese animals and/or difficult to lose weight), as well as susceptibility to endocrinopathic laminitis can result from this intrauterine reprogramming. It is common to use lactating mares as embryo recipients, however, little is known about the effect on the mare's metabolism and influence on the foal's development. Our study aimed to compare the insulin, glucose and others metabolism markers of foals born from lactating (L) and non-lactating (NL) recipient mares, from day 1-28 of life. We used 12 normal foals, offspring of Mangalarga Paulista mares aged 5 to 15 years. Mares from the lactating group continued lactation from ovulation until a maximum of 170 days of pregnancy. Foal evaluations were performed the day after birth (D1) and at 7, 14, 21 and 28 days of age. Glucose (mg/dL), insulin (µU/mL), triglycerides (mg/dL), non-esterified fatty acids (NEFA; mmol/dL) and cortisol (µg/dL) were analyzed. We used factorial arrangements between groups (L, NL) and time (D1, D7,D14, D21 and D28). The results presented are the mean and standard error of the mean. There was no statistically significant interaction in any of the variables. There was no difference between groups, but insulin, glucose, triglycerides and cortisol changed over time. Insulin concentrations were lower on D1 and equal at other times (D1:3.82±0.27; D7:6.28±0.59; D14:7.89±0.98; D21:6.97±0.69; D28:5.87±0.88; P=0.002). Glucose was lower on D28, which was equal to D21 (D1:144.83±5.27; D7:148.33±3.96; D14: 147.25±4.27; D21: 140.25±3.04; D28: 133.33±3.75; P=0.02). Triglycerides were higher on D1 and D7, on D14 were equal to these times and to D21 and on D28 were lower than other times, being equal to D21 (D1: 72.64±21.95; D7: 65.59±8.38; D14: 51.92±7.73; D21: 41±3.47; D28: 34.05±2.84; P<0.01). Cortisol was higher on D1 and lower on all other times (D1: 0.83±0.09; D7: 0.42±0.06; D14: 0.43±0.04; D21: 0.57±0.06; D28: 0.6±0.07; P=0.003). In conclusion, some characteristics change with foal age such as insulin, glucose, triglycerides and cortisol. The lactating recipient mare status during the initial third of pregnancy does not influence the postnatal characteristics of the foal up to 28 days of life. Acknowledgements: FAPESP (2017/05425-0 and 2020/10260-3) and CAPES for financial support.