Akins is an extension dairy specialist with the University of Wisconsin-Madison. Hribar is a graduate research assistant at UW-Madison.

There seems to be growing interest in grazing dairy heifers, especially in areas looking to utilize perennial forages to protect water resources. In addition to environmental benefits, other reasons include getting heifers off concrete to reduce hoof wear and lameness, reducing labor and feed costs, and potentially improving health after calving.

The cost to raise heifers is substantial. In a 2015 survey of Wisconsin dairy producers and heifer growers, daily costs were $2.20 to 2.75 for 300- to 900-pound heifers (weaning to 15 months old) and $3 to 3.50 for heifers over 900 pounds. Feed and labor made up a significant portion of these costs with feed accounting for 54 percent and labor being 16 percent of the total outlay.

Data from the University of Minnesota and Cornell University has shown reduced costs for grazing dairy heifers due to lower feed, labor, and machinery inputs. Both of these studies supplemented heifers while on pasture to maintain growth between 1.7 and 2 pounds per day. Heifers on pasture should be expected to have similar growth to a confinement system in order to keep heifers on track for breeding and attaining an optimal weight prior to calving. Research at the University of Wisconsin (UW) Marshfield Agricultural Research Station has addressed grazing heifer growth for several years.

A tale of two grasses

In a project to evaluate Hidden Valley meadow fescue, a three-year study with the USDA Dairy Forage Research Center and UW-Madison compared meadow fescue to Haymaster orchardgrass grown as monocultures. Twenty-four heifers (5 to 6 months old, weighing 550 pounds) were grazed each year. Our stocking rate of 1.6 heifers per acre stretched the available forage with lower residues remaining than desired at the end of the grazing seasons.

In spring of 2017 and 2018, grazing started one to two weeks later than desired, which was likely due to insufficient residue in the fall that slowed regrowth in spring. Heifers were moved every three to four days to a new paddock with a rotation length of 35 days. Only a mineral supplement was provided with no other concentrates or forages fed. Nitrogen was applied in late June and late August each year to stimulate growth in summer and fall.

Available forage when the heifers entered a paddock was on average higher for meadow fescue (1,350 pounds of dry matter [DM] per acre) than orchardgrass (1,210 pounds of DM per acre), with total forage yield being similar at about 6,200 pounds of DM per acre. Orchardgrass pastures were ready a week earlier in spring than the meadow fescue.

As expected, meadow fescue had better forage quality with lower neutral detergent fiber (NDF, 53 percent), higher NDF digestibility (67 percent of NDF), and higher crude protein (CP, 14.8 percent) than orchardgrass (56 percent NDF, 64 percent NDF digestibility, and 14.1 percent CP).

Heifer growth was similar between orchardgrass (1.63 pounds per day) and meadow fescue (1.72 pounds per day), but there was variation with heifers grazing orchardgrass having lower gains (1.49 pounds per day) than meadow fescue (1.78 pounds per day) in 2017.

In spring 2017, it was very wet, which delayed clipping when forages headed out. This led to more mature growth and lower production, especially for orchardgrass. Meadow fescue headed out later and forage quality was less affected by the delayed clipping. Heifers also seemed more apt to consume the meadow fescue stems.

Use of later maturing varieties may help slow heading and maintain higher quality forage if clipping or harvest is delayed. The heifer growth was slightly lower than the target of 1.8 to 2.2 pounds per day for the Holstein heifers, which may have benefited from a lower stocking rate or the use of a forage or concentrate supplement when grass growth slowed. Inclusion of a legume in the pasture may also have improved productivity by providing nitrogen for the grass and raising the protein content of the forage.

In another project, we looked at the growth of heifers grazing a mixed forage pasture (meadow fescue, perennial ryegrass, festulolium, red clover, and white clover). Sixteen 6-month-old heifers were grazed on a 16-acre pasture in 2017 and 2018. The stocking rate was not high enough to keep ahead of the forage growth, so forage was harvested from part of the pasture once the grasses headed out in 2017.

A rotation length of 35 to 45 days was used with heifers grazing three to four days on each paddock. No concentrate or forage supplement was provided to the heifers, and no nitrogen fertilizer was applied to the pasture. There was plenty of forage available with an average of 2,600 pounds of DM per acre and a residue of 1,330 pounds DM per acre left in the pasture after each grazing move. A higher stocking rate could have been used to improve utilization, as there was surplus forage for much of the season.

Mixed pastures are dynamic

Forage quality was high with an average of 46 percent NDF, 60 percent NDF digestibility, and 19 percent CP. Together, the high forage availability and quality led to heifer growth of 2 pounds of gain per day. It should be noted that in 2018 the pasture had a greater proportion of red clover as heifers grazed the more palatable grasses in 2017. With the high clover content, a few of the heifers bloated in the fall with cooler temperatures and very immature growth.

Mixed pastures will change over time as animals graze more palatable species and may require reseeding of desired species or a shift in management to favor those species. A faster rotation can be used to minimize overgrazing of more palatable species and/or nitrogen can be applied to encourage greater grass growth.

As with any heifer program, it is important to monitor heifer growth
to ensure they are meeting growth targets and adjust pasture management as needed or possibly provide supplemental feeds.

This article appeared in the November 2019 issue of Hay & Forage Grower on page 8.

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