How to make sure only the most productive animals enter the milking herd
Producers every day dedicate a significant amount of time to improving the productivity and profitability of their lactating herds. Much of their effort focuses on opportunities in reproduction, health, and feed management.
These areas play a significant role in lactating cow profitability, but delivering a healthy heifer into the milking herd can have just as significant an impact. Therefore, culling can be a great tool to ensure the most productive animals enter the milking herd.
Critical culling times include:
- When calves leave hutches
- The pre-breeding growing phase
- At breeding
Culling heifers out of hutches
It is likely that the calf’s greatest genetic potential is at conception. From that point on, extraneous impacts can diminish her potential productivity. Possibly the most vulnerable time is during her first 60 days of life. During this period, illness can impact both the calf’s performance as well as the heifer and mature cow’s lactation performance.
Several papers have summarized the?impact of morbidity in calves on their future health and?performance. Illness affected both calves’ ability to stay in?the herd and their performance in first calving. Diarrhea?increased the chance of a leaving the herd by 2.5 times?and increased the chance of calving after 900 days of age?by 2.9 times (Waltner-Toews et al., 1986). Respiratory?illness in caves resulted in increasing the age at first calving by 6 months, if those heifers calved at all. Also, heifers were 2 times more likely not to calve if they were diagnosed with respiratory illness (Correa et al. 1988).
Pneumonia also has an impact on future milk production as shown in Table 1 (Morrison et al. 2013). This research shows calves diagnosed with pneumonia had lower milk, fat, and protein production for both first and second lactations.
Growth rates during the early part of a calf’s life play a significant role in future production. Dry matter intake (DMI) has a major effect on that growth rate, as shown in work summarizing the effect of DMI at weaning on subsequent heifer milk production (Heinrichs et al., 2005). Researchers found that for every 1 lb increase in DMI, there was a corresponding 286.7 lb increase in first-lactation 305-day lactation mature equivalent milk yield (305-d ME).
These observations in young calves certainly demonstrate the need for increased scrutiny when culling. This period of time in a calf’s life has a very large impact on the calf’s ability stay in the herd and be productive. Calves that do not meet standards for health and growth should certainly be evaluated to determine whether the risk of keeping them in the herd is warranted.
Pre-breeding growing phase
There is a tendency to overlook the period between the hutch and breeding. Heifers are typically put on a growing diet and left to themselves for the next 300 days or so. However, there are opportunities during this period to make evaluations and cull if necessary. Most of these animals are not facing health challenges, so growth is going to be the biggest driver of their future productivity.
Researchers at Penn State University used meta-analysis to look at how average daily gain (ADG) in heifers impacted first lactation 305-d ME (Figure 1; Heinrichs, et al., 2016). They found that there is not a linear response to ADG and 305-d ME, but a curvilinear effect. The data suggested that an optimum rate of gain was about 1.75 lbs/d from 2 months of age to puberty, with an acceptable range of 1.6 – 1.9 lbs/d.
Any gains less than or greater than that range resulted in diminished 305-d ME in first lactation animals.
When heifers within groups are not growing at the same rate as their contemporaries, evaluations should be made to see if those animals fit the program moving forward. Most of the heifers of concern are going to be those that do not gain as fast as our recommended rates. If these animals are behind, but have received diets that should provide adequate gains, then they are not likely to perform well in the milking string.
Conversely, there are occasions when heifers gain at rates that are greater than recommended. Typically this is due to dietary issues and, if corrected early enough, the gains can be reduced to an acceptable range without too much trouble. Those that slip through and arrive at puberty significantly over-conditioned are likely to be a problem in the future and should be evaluated. These cases involve a few animals, not the whole heifer development program. If the whole program is over- conditioned, then there are going to be larger issues at stake, but the dairy probably cannot, or would not, cull the whole program.
Culling at breeding
The goal of raising the heifer is to have a productive lactating cow. Also, developing that heifer to breeding age is a significant cost to producers. Therefore, getting her bred at the appropriate time is paramount. Unfortunately, things don’t always go as planned.
Although most heifers are relatively fertile, there are some that struggle to get pregnant. It’s fair to say that most producers continue to breed until they become pregnant. They may use continuous artificial service (AI) breeding or a set amount of AI breedings followed by a trip to the bull pen. This can be a costly venture.
Matt Sattler, one of Diamond V’s Ruminant Field Technical Specialists, analyzed a group of 34 herds with about 200,000 animals total, examining the impact of continuous breeding of heifers. He looked at conception rates of heifers by times bred and found that, after the fourth breeding, the conception rates drop considerably (Table 2).
This result is likely due to heifers that are just not as fertile as their contemporaries for some reason. Not only are these animals difficult to breed as virgin heifers, they typically struggle to breed back as first lactation animals.
Matt also found that reproductive performance as related to number of times bred as a virgin heifer shows significant breeding lag. Heifers that took more than 4 services before conception had a 25% lower pregnancy rate as a first lactation animal. In addition, their first service conception rates and overall conception rates were 19% and 22% lower, respectively (Table 3).
These data suggest that if there is significant trouble breeding a heifer, then there will be issues as the animal matures, as well. This results in delayed lactation and reduced productivity and profitability in the herd. Given the goal to get animals pregnant, heifers bred more than 4 times should be removed from the herd.
Corea, M.T., C.R. Curtis, H.N. Erb, M.E. White. 1988. Effect of calfhood morbidity on age at first calving in New York herds. Prev. Vet. Med. 6:253-262.
Heinrichs, A.J., B.S. Heinrichs, O. Harel, G.W. Rogers, and N.T. Place. 2005. A prospective study of calf factors affecting age, body size, and body condition at first calving of Holstein dairy heifers. J. Dairy Sci. 88:2828-2835.
Heinrichs, J., C. Jones. 2016. Monitoring Dairy Heifer Growth. Penn State Extension.
Morrison, S., G. Scoley, and J. Barley. 2013. The impact of calf health on future performance. Veterinary Ireland Journal. Vol. 3. Number 5.
Waltner-Toews, D.S., S.W. Martin, and A.H. Meek. 1986. The effect of early calfhood health status on survivorship and age at first calving. Can. J. Vet. Res. 50:314-317.