Is early spring grass enough for the lactating heifer?

The young lactating heifer has and will continue to be a rancher’s biggest nutritional challenge in the beef herd. If the young cow’s mature bodyweight is between 1,200 and 1,300 pounds, she likely only weighs a little over 1,000 pounds the first month after calving.

Karla Jenkins

Therefore, she presents a challenge because she must gain weight to reach her mature body size, lactate to supply her new calf with nourishment and rebreed within 83 days if she is to calve again within 365 days of her first calf.

The heifer calving in March is likely to have very little access to green grass in April in the Upper Midwest. However, many producers try to utilize some early green-up of cool-season grasses with lighter stocking rates than is recommended for season-long grazing during this early spring period.

Adding some green grass to the diet can certainly increase the protein and digestibility of the diet. However, producers need to be cognizant of the fact that grazing, even at light stocking rates, reduces the available high-quality forage very rapidly and may make the heifers select a large enough proportion of dormant grass to substantially reduce the quality of the diet selected.

A research study conducted at the Gudmundsen Sandhills Laboratory near Whitman, Nebraska, evaluated the quality and quantity of diets available during the last three weeks of May on predominantly warm-season grass pastures.

The pastures were either not grazed or grazed at one-third or one-half the recommended season-long stocking rate. By 21 days of grazing, the digestibility of the new growth was 71 percent, and that of the dormant forage was 47 percent.

That selected by the cattle was 63 percent, suggesting that as the pastures were grazed, the cattle were being forced to select more of the dormant forage.

For the young lactating cow, this selected diet would still meet her protein and energy needs. However, if the stocking rate were heavier, or environmental conditions prevented expected grass growth, the selected diet could quickly fall below the needed quality. If the heifer begins to lose weight rather than gain weight, it will reduce her chances of rebreeding on time.

If green grass is not available for the young lactating heifer for a month or two after calving, a supplemental diet which meets her needs is critical.

For an example diet, this lactating heifer might be receiving ad libitum hay that contains 52 percent total digestible nutrients, and 10 percent crude protein and 3.5 pounds of dried distillers grains. It might be surprising to note that this diet is still slightly short of her energy needs.

Providing this same amount of hay – that was at least 58 percent total digestible nutrients and 10 percent crude protein – with the distillers grains supplement would supply the heifer’s needs.

Therefore, it is critically important for the producer to evaluate the feed resources available, the time between calving and green grass, and the availability of high-quality feed at the initiation of the breeding season.

Testing forage resources for nutrient content, evaluating heifer body condition before and at calving, monitoring heifer body condition as breeding approaches and not overgrazing early spring growth can go a long way to set these young cows up for a long career in the cow herd.