Lower feed costs, less manure and fewer over-conditioned heifers are the top reasons to consider limit feeding, says Pat Hoffman, a University of Wisconsin-Madison dairy scientist based in Marshfield.
Limit feeding, or feeding a more nutrient-dense ration at less than intake potential, has been used successfully on other livestock species, such as beef cows, beef heifers and ewes. It's gaining interest among dairy producers and commercial heifer growers who feed total mixed rations, too, says Hoffman.
“Achieving adequate growth rates with limit feeding is relatively easy to do,” he says. “Heifers get the nutrients they need, but in smaller, denser packages. Dairy producers are always looking for innovative ways to reduce feed and environmental costs. Limit feeding is difficult for lactating cows, but there's a lot of potential to do it with heifers.”
The amount of limit feeding being used on dairy farms is low because most operations don't have adequate bunk space. But Hoffman sees that changing.
“Because of the benefits it provides, many producers are evaluating the bunk space in their facilities so that they can consider doing it,”he reports.
His experiments have limited heifer diets to 80-90% of their intake potential. In a recent 111-day feeding trial, three groups of 1,000-lb heifers were fed diets with 67.5%, 70% or 73.9% TDN. The control group was fed the 67.5%-TDN ration at intake potential. The heifers fed 70%- and 73.9%-TDN diets were limit-fed at 80% and 90% of their intake potential, respectively. While the latter two groups were fed less dry matter per day, they consumed the same amount of protein and energy as the control group.
After the trial, Hoffman and his associates didn't see any differences in the size or body condition scores of the three groups, and no negative effects were observed among the limit-fed animals after they calved. But those heifers excreted significantly less manure than the ones in the control group.
“Manure production can be reduced by up to 20%; however,the amount of nutrients in the manure is going to remain relatively the same,” says Hoffman.
He encourages producers to work closely with knowledgeable nutritionists to develop their own limit-feeding rations.
“In general, limit-fed diets have the opportunity to contain more corn silage and higher levels of concentrate feed, such as corn, distillers grains or other byproducts.”
Just prior to calving at 24 months, Holstein heifers should weigh around 1,400 lbs, says Hoffman. To meet that goal, they have to gain an average 1.8 lbs/day.
There are three management points to consider before limit feeding, reminds Hoffman:
Adequate bunk space is needed to prevent uneven gains. “The current guideline for bred heifers eating out of a bunk at one time is 18"/head.”
Heifers should not be bedded with straw or cornstalks because they might eat them.
Increased feed push-ups may be required to ensure that heifers don't have to reach for feed.
Limit-fed heifers need to be fed only once a day. To a minor extent, they're likely to bellow just before feeding for about the first week, but seem to adjust well, Hoffman says.