THERIOGENOLOGY – MARE


were 15% to 19%(fair quality), and 5mareswere≤14% (poor quality). There was no statistical difference (p>0.05) in colostrum quality between multipa- rous mares (27.364.5%; n=139) and primiparous mares (26.065.5%; n=51). Therewas alsonodiffer- ence in colostrum quality between mare age groups (27.964.6,< 10years; 26.664.9, 10–14years; 27.164.6, 15–19years; 26.065.6, ≥ 20years). The average plasma IgG concentration of foals born tomares with a colostrum Brix score of<20% (1456.76572.4mg/dL; n=15) was significantly less (p<0.05) than the IgG concentration of foals born to mares with a colostrum Brix score of 20% to 29% (1775.96377.5mg/dL; n=123) or≥30% (17756483.6mg/dL; n=91). There was a strong cor- relation, r(98) = 0.97, p<.05, between the SRID IgG values and Brix refractometer scores for colostrum samples collected from the subset of mares during the first 12hours postpartum. ColostrumIgG concen- tration and Brix score immediately after foaling were 20694.066284.3mg/dL and 28.264.0%, respectively, and declined to 1720.461910.8mg/dL and 11.161.8%, respectively, at 12hours postpartum, and 626.16 232.0mg/dL and 10.560.5%, respectively, at 24hours postpartum.


4. Discussion


Evaluation of colostrum using a Brix refractometer is a rapid and inexpensive technique to estimate quality,


Conflict of Interest The Authors have no conflicts of interest.


and results are correlated with IgG content as determined by SRID assay. Foals born to mares with fair or poor-quality colostrum have lower plasma IgG concentration than foals born to mares with good- or very good-quality colostrum. Mares with fair- or poor- quality colostrumcan be identified early and their foals supplemented with frozen-thawed colostrum and/or a colostrum substitute orally within the first few hours after birth. Knowledge of colostrum quality is also im- portant when selectingmares fromwhich to harvest co- lostrumfor banking. Colostrumshould be harvested as soon as possible in the postpartum period to optimize colostrumquality as nursing by the foal results in rapid depletioninIgG. Inaddition, understandingwhenco- lostrum IgG concentrations decline to baseline levels can be helpful in determining when to allow a foal con- sidered to be at risk of neonatal isoerythrolysis to nurse from their dam.


Acknowledgments


Declaration of Ethics The Authors have adhered to the Principles of Veterinary Medical Ethics of theAVMA.


AAEP PROCEEDINGS / Vol. 68 / 2022 279


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