Say No to Positive Cytology!

Obese Mares Have More Problems Than We Thought!

It has been previously documented that obese mares have a higher tendency towards early embryonic death, particularly in hot weather and this has been put down to the core temperature of these mare potentially being higher than other mares, with a negative impact on embryo survival[1]. At ISER XIII Meikle et al however demonstrated that these mares have other issues as well, and even if younger may present some issues parallel to those seen in older mares.

17 mares were categorized by their body condition score using the Henneke scale, and were divided into two groups – “obese” (>7 score, n=6) and “normal” (<7, n=11). They were also divided into age groups – “mature” (5-14 years, n=9) and “aged” (15-21, n=8).

8 hours after being bred, the mares underwent a low-volume lavage (50 ml) and the resulting captured fluid was evaluated for neutrophil count. The captured fluid also underwent additional processing in order to be further evaluated for metabolite determination by spectrophotometry.

Obese mares - Post-breeding inflammatory response showing neutrophil presence

Stained cytology smear of uterine sample taken 12 hours after insemination

It was found that obese mares tended to present higher neutrophil counts than did those mares in the normal group. Unsurprisingly, those mares in the “older” group also had greater counts. Interestingly, there was no difference found between the groups related to edema or intrauterine fluid levels at the time of insemination or the subsequent LVL.

The content of the intrauterine fluid was not significantly different in the groups, with the exception of urea, which was found to be present at a higher level in the older mare group.

Our own interpretation of these findings suggests that obese mares may benefit from tighter post-breeding management, more in line with that which may be provided for older mares, even if the obese mares are younger.

(Meikle A, Pardie M, Kalpokas I, Villar L, Rotela F, Aguilar E, Gómez-Cuetara C. 2023. Obesity and age on post-breeding endometritis in the mare. JEVS 125:104731)

1: Mortensen CJ, Choi YH, Hinrichs K, Ing HN, Kraemer DC, Vogelsang SG, Vogelsang MM. 2009. Embryo recovery from exercised mares. Anim Reprod Sci 110(3-4):237-44