Broodmare nutrition: Lactation remains most demanding period
Proper broodmare feeding is not much different than for any other female breeding animal. When it comes to nutrient needs for all young-bearing animals, the latter stage of pregnancy — especially lactation — is most demanding. What's most important prior to pregnancy is that the mare is neither too thrifty nor overweight, with a proper body condition score for her size (5-6, moderate to fleshy).
"Don't forget about your barren mares as the breeding season approaches," cautions Jim Brendemuehl, DVM, PhD, Dipl. ACT, assistant professor, University of Illinois College of Veterinary Medicine. If they are in an anabolic state coming into the breeding season, they will be more apt to be fertile/conceive.
As far as the non-pregnant mare is concerned, Brendemuehl explains, barren mares can be somewhat neglected, turned out to pasture and forgotten until the start of the breeding season. The result? Many will lose substantial body condition, stop cycling and won't start until they put the weight back on."I had a large number of underweight mares ship in the first of February this year, and they did not cycle for two months with body condition scores of about three, and ovaries the size of peas. It was not until they gained about 200 pounds, before they'd think about cycling," he adds.
During early pregnancy, from conception through eight months, while food intake and body weight should be monitored carefully, classical thinking was that the mare did not need additional nutrition.
Burt Staniar, PhD assistant professor of equine nutrition, in Virginia Tech's Animal Sciences Department, reports that while the concept may be correct in regard to energy, it may not be so in regard to other nutrients.
"At this time we're just not sure," he says. To say that the fetus is not developing that fast during the first months of gestation is one thing, but whether there are nutrients — be it amino acids for tissue, minerals for proper cartilage and bone growth, or vitamins — that might be better at levels above maintenance prior to the latter stages of gestationis unknown.
Traditional thinking is that good-quality pasture alone or good-quality hay can easily sustain the horse. During the early portion of gestation, the mare should be fed at the maintenance level of 1Mcal/per lb. feed, which may be met solely by good pasture or forage, about 15 pounds for the average light mare (1,100-1,200 pounds), along with a trace-mineral salt block free choice. This should provide about 8% crude protein, 0.3% calcium (Ca), and 0.2% phosphorus (P).
"We observed that mares would gain a lot of weight during mid-gestation (2nd trimester), and that weight gain was fairly flat during latter gestation," says Laurie Lawrence, PhD, professor/equine nutritionist, Department of Animal Sciences, University of Kentucky.
Maybe naturally, mares were inclined to eat plenty when available to build up fat stores to be used during latter gestation. Many mares back off feed during later gestation, possibly due to the lack of room from the fetus.
"From an energy, and possibly protein standpoint, it may be important to consider a modest increase in energy/protein intake during the 2nd trimester, rather than trying to force the mare to consume more later in gestation, especially if you think her intake is going to be dropping off," Lawrence states. It may be better to feed a bit more early on. While the pregnant mare uses body fat stores for energy during pregnancy, she does not have similar reserves of protein.
If the mare is re-bred during foal heat she will need to be treated differently because of the combination of early lactation and early pregnancy. In this case, she will need not only increased energy intake, but also protein quantity and quality, especially lysine.