Heifer rearing is a major expense and accounts for 15% to 20% of the total cost of producing milk for U.S. producers. Therefore, consider maximizing the return on your heifer development investment. To do that, you first need to set and meet evidence–based goals for heifer performance.
Although most discussions of heifer rearing begin with the newborn, instead, start with goals for heifers in their first or even second lactation. This allows you to step back and examine each stage of heifer development to find the critical control points or the bottlenecks that might be holding them back.
Of course, specific goals for heifers will vary from farm to farm, based on breed and the current status of the herd. But in general, you need the right number of heifers calving at the right age with the optimum investment in their development, producing the right amount of milk and components, with few getting sick and few being culled early in lactation.
Consider the following seven points as you evaluate your heifer-rearing program to maximize its impact on your dairy.
- High First-Lactation Milk
The value gained from raising heifers is in the milk and components they produce once they have their first calf. The prevailing theory is that you do not see a return on the heifer investment until the middle of the second lactation, meaning first-lactation performance is critical for success.
Three measures to examine are:
- Mature equivalent (ME–305) milk production in first lactation. Most recommendations are that ME–305 milk should be more than that of mature cow production.
- First lactation total yield should be more than 80% of that for mature cows.
- Peak milk may occur about 13 to 14 weeks in lactation and should be more than 80% of that for mature cows.
- High First-Lactation Fertility
Cows in their first lactation are still growing and both milk production and reproduction may be affected. First–lactation cows tend to have more days to first service than their older herd mates but greater pregnancy rates, which can be up to a third greater than second- or greater lactation cows.
Although much information exists about the economics of getting cows bred back early, there is little evidence on how heifer rearing can influence the establishment of pregnancy.
In one study, conception rate at the first A.I. was greatest (about 37%) in the medium age at first-calf (AFC) group (701 to 750 days of age) compared with low or high AFC heifers (28% and 31%, respectively) and more of the middle AFC group were pregnant at 310 days. More research is needed to determine the influences of age at first calving or average daily gain (ADG) on the fertility of cows in their first lactation.
- Reduced First-Lactation Disease and Culling
An indicator of fresh cow (and heifer) problems is the proportion of culls of the total number freshening in the same cohort within the first 60 days in milk. The same transition issues of cows can affect heifers (like ketosis, metritis and mastitis), but there is also an increased risk of culling first–lactation cows if they had respiratory disease some time before calving. One recommended goal is for less than 6% of first–lactation culls to occur during the first 60 days in milk.
- Reduced Age at First Calving (AFC)
One way to reduce total rearing cost is to reduce the AFC. This is an easy number to find and monitor for most producers.
The consensus is that the younger the AFC, the earlier the return on the investment is achieved. But questions remain. How early is too early and when is early enough? The specific goal should be farm–dependent because breed, management, feeds, employees and facilities all play a role.
In addition, AFC must be considered as well as body weight, height (frame size) and body condition score (BCS). Unfortunately, monitoring weight and height—and even BCS at calving—are not routinely done on most farms. Recommendations for the optimum AFC are 21 to 23 months at a BCS of 3.5 and body weight (Holstein) of 1,450 to 1,550 pounds at calving, or 90% of mature body weight.
- Ready to Breed—Younger Age at Puberty
Puberty is dictated by heifer growth, and growth is dictated by nutrition and management.
If a goal is for heifers to calve at 22 months, then they must conceive by 13 months and become pubertal by nine to 11 months. First estrus may be at 55% of mature body weight and 48 to 50 inches at the withers. A BCS of 3.0 at breeding is recommended.
Diet is the key influence on when heifers become pubertal. In a French study, grazing heifers reached puberty about one month later than those fed a corn-silage–based diet with a high level of concentrate, but productive life was longer in the grazing heifers. The study also indicated that the greatest growth rate before puberty was associated with lower milk production.
- High Average Daily Gain (ADG)
Exactly how fast and when heifers should grow fast can be confusing. Because there is some debate about pre–pubertal growth rates and future heifer performance, pre–pubertal growth can be divided into early life (or preweaning) and postweaning growth. Although older heifers can experience compensatory gain, neonates lack the mechanisms to support compensatory gain.
Feeding preweaned calves is expensive and time consuming, but doing it “right” can make a big difference for a heifer to be highly effective. There seems to be substantial evidence that supports accelerated preweaning growth for a variety of outcomes, as well as increasing heifer–rearing economic returns.
For example, feeding an intensive, high solids, high feeding level milk replacer compared with a 20:20 milk replacer resulted in a reduction of AFC by about four weeks. Milk–fed calves reached puberty sooner (by 23 days) and had greater yields of 305–day fat–corrected milk during first lactation.
In a recent report, a large group of Holstein heifers were followed for more than eight years.
- The youngest AFC was achieved with the greatest ADG (2.07 pounds/day).
- Those with a medium range ADG (about 2 pounds/day) from five to 14 months had the greatest first–lactation milk yield.
- Those growing 2 pounds per day had the greatest lifetime performance, approximately 1,000 kg (305 days) more than the medium group.
The conclusion from these studies is that pre-pubertal growth is important to first-lactation milk yield, but there may be a maximum beyond which diminishing returns occur. If a dairy operation has a specific goal for ADG, just as with adult cows’ milk production, anything that affects dry matter intake will affect ADG.
- Low Morbidity–Mortality as a Neonate.
In recent years, more research has been devoted to the heifer’s very early nutrition and management, with more evidence coming to bear on the importance of the preweaning period. To have a healthy calf that survives through weaning and beyond is the primary goal.
- Fetal Programming. Even before the heifer’s birth, nutrition and other dam factors can potentially affect calf health. In addition to nutrition, heat stress during late gestation can affect calf growth and survivability.
- Calving Difficulties. Immediate effects of a dystocia on the calf include death, but also neonatal hypoxia, which can lead to an increased risk of death. Heavier birth weight calves were also more likely to die during the first 60 days of life compared with normal birth weight calves. Delivery score is associated with ME–305 milk yield. For each one–unit increase in delivery score, average milk production was reduced by approximately 430 pounds. A goal of dead–on–arrival rates less than 5% seems reasonable.
- Colostrum Feeding and Management. Ample evidence exists concerning the importance of colostrum to calf survival. Colostrum intake seems to influence heifer performance later in life. In 1989, a prospective study detected a positive correlation between serum IgG concentration and ME–305 milk yield. For each unit of IgG above 12 mg/mL, there was an 18-pound increase in ME–305 milk yield.
- Disease. For calves on dedicated calf-rearing facilities, approximately 18% and more than 16% were reported to be affected with digestive and pneumonia conditions, respectively.
- Calves with pneumonia may have poorer preweaning ADG than calves without pneumonia. If calves had respiratory disease during 60 days after being moved into group housing (after about 56 days of age) they had poorer ADG from two to nine months (about 0.22 pounds/day), greater AFC and a tendency for reduced first-test milk production.
- If calves had both diarrhea and respiratory disease in the preweaning period, their ADG was about 0.11 pounds/day lower.
- The number of days that calves were ill negatively impacted ME-305 milk production during first lactation.
To get the heifers into the milking string when desired and how we want them requires regular monitoring. Monitor first-test–day milk, peak milk, ME–305 milk and AFC. These measures are reported by most dairy management software programs. Other items to consider monitoring include body weight at various stages, height and feed intakes—considered the minimum measurable items, as well as growth rates and BCS.
For each measurable item, maintain a summary of the number of heifers, the average values and the range of values to help in decision–making.