When maternal behavior in mares goes wrong
Early this spring, two famous primiparous mares will have their foals. The 2009 Horse of the Year, Rachel Alexandra—the first filly in 85 years to win the Preakness that also has wins in several G1 races including the Kentucky Oaks, Haskell Invitational and Woodward Stakes—is in foal to Curlin, two-time (2007/2008) U.S. Horse of the Year. Her expected due date is Feb. 1, 2012.
The 2010 Horse of the Year, Zenyatta—the darling of the Breeder's Cup and winner of 19 of 20 races, including the Ladies' Classic in 2008 and the Classic in 2009—is in foal to Bernardini with an early March 2012 due date.Likely, these two dams will show their natural maternal instinct to nurse and protect their foals. But these anticipated births may make us consider what normal maternal behavior is in mares and what triggers it. And what can equine practitioners do when confronted with aberrant mare behavior, foal rejection or outright aggression toward offspring?
Normal maternal bonding behavior
Normal maternal behavior is most likely triggered at parturition by a change in estrogen and progesterone concentrations, the production of prolactin and the release of oxytocin. Prolactin may not initiate maternal behavior, but it helps stimulate milk production.
As the foal is born, cervical stimulation promotes the release of oxytocin that not only initiates milk let-down but also a firing of axons in the olfactory bulb that fosters the mare's recognition when she sniffs the foal's breath and odor and licks the foal's head. With the foal in front of her and her smelling it, she will probably allow it to suckle. Foal recognition is also thought to be assisted by the mare sniffing the perianal region where she picks up the scent of her own digested milk once the foal is already nursing.
Not only does the mare elicit foal recognition and attention, but the foal plays a role in fostering maternal bonding behavior by its first movements toward the head of the mare, vocalizing, seeking the udder and suckling and keeping close to the mare.
Varying degrees of mare aberrant behavior exist, from ambivalence to rejection and aggression. Although rare, each can be a management hurdle for breeding farms but can be assisted by veterinary consultation and intervention.
"There are different extremes where mares may or may not accept their foals," says Karen Wolfsdorf, DVM, Dipl. ACT, Hagyard Equine Medical Institute. "You have to have a lot of patience to work with these mares, especially primiparous ones, to accept their foals."
The mare might accept and lick the foal but not allow it to nurse. This may be the result of the foal touching the mare's sensitive inguinal area as it seeks to nurse. "This relatively new finding is that a given mare is not objecting to having her udder or teats touched but that it's the inguinal fold that is sensitive, which the foal often hits with its head as it approaches the udder," says Katherine Houpt, VMD, PhD, Dipl. ACVB.
"If it is inguinal fold touching that bothers the mare, you can work on desensitizing her to that," Houpt says. "The procedure is for a caretaker to touch the area and gauge her response. If the response is negative, you can trot her around on a lead rope and try touching her again. Eventually she should give in to being gently touched in that area and, thereby, accept the foal's approach, even if not perfect. You can desensitize her until she does not object and then allow the foal to attempt to nurse, which, if done successfully, will relieve her objection."
In some cases, the mare may have little to do with the foal, or, alternatively, the mare might attack the foal, attempting to kick, bite or throw it.
"If you have a mare that routinely doesn't bond with any of her foals and just tries to ravish them, the farm manager understands that when she foals, the baby needs to be removed from the mare because from past behavior she has stomped and killed previous ones," Wolfsdorf says. "When the situation becomes that drastic, it is safer for mare, foal and caretakers just to put the foal on a nurse mare as an alternative."
"If she is overtly aggressive—her ears are pinned, she's chasing the foal, biting or kicking at it—it may be safer to get the foal a surrogate mare because she might well injure or kill the foal," says Houpt.
For primiparous mares, fear of the foal may trigger rejection. The fearful mare may move away from the foal each time it approaches or even try to attack it if the foal is too assertive.
"Especially with maiden mares, they seem to not know what's going on with a newborn that's trying to suckle on them every which way and often," says Wolfsdorf. In addition, maiden mares may have an excessively filled udder, their udders may be a little painful or the mares may not produce enough milk, making the foal go at them often, annoying the mares.
Reestablishing the bond vs. using a surrogate
To decide whether to try to reestablish a bond or go with a surrogate mare, you must determine why the mare is rejecting the foal. Some mares are just frightened of their foals. If this is the case, you can try restraining a mare until she learns that the foal is not going to hurt her.
"You can use drugs, either sulpiride (a dopamine D2-antagonist) or acepromazine, which will also help release prolactin," Houpt says. "If the mare learns that once the foal suckles, it feels good and it relieves tension in the udder, she may be more apt to accept it."
"With problem mares, management may be necessary, with the mare being held and the foal positioned to properly suckle the mare," says Wolfsdorf. "With practice, the mare becomes used to the foal, and as the foal continues to suckle, the mare begins to figure it out."
If you find that suckling is painful, Wolfsdorf says you can administer analgesics or anti-inflammatories.