How are Holstein Heifers Performing in PA?

Raising replacement heifers for your dairy can be a challenging task. Because they are an expensive part of a dairy, we want to ensure that those heifers are productive when they enter the milking herd. In their course of growth and development, it is important to understand that how they are raised from birth to freshening can impact their future milk production potential. Colostrum, housing, health events, nutrition, average daily gain, and age at first calving (AFC) are all factors that can play a role in future performance. Once any of these factors are compromised, the performance of that heifer may be negatively affected. One of these factors that have been tracked over the years is AFC. What is the average AFC for Pennsylvania Holstein heifers and how has this impacted milk production in recent years?

Penn State Extension recommends for Holstein heifers to calve between 22 and 24 months of age. A 2012 article stated that heifers could calve between 22-24 months without negative effects on milk yield. This article explained that calving too early was detrimental to milk performance and delayed calving put heifers at risk for excessive fattening and restricted mammary gland development (Froidmont et al, 2012). With the help of Dairy Records Management Systems (DRMS) records, Penn State Extension has routinely tracked heifers freshening throughout Pennsylvania. A previous report from Penn State compared the average AFC from 2002 to 2017 in Holstein heifers. In the figure below, it's easy to see that heifers are freshening earlier in 2017 compared to 2002.  Figure 2 shows this same information for fresh Holstein heifers in 2019 compared to 2023.  

Looking more closely at yearly averages within these graphs, there are only slight shifts in the averages. DRMS data over the years indicates that the average AFC for Holsteins was 25.68 months in 2013, 25.51 months in 2015, and 25 months in 2017. The latest data reports that the average AFC in 2019 was 25.02 months, 25.31 months in 2020, 25.18 months in 2021, 25.02 months in 2022, and 25.08 months in 2023. The last couple of years closely mirror the same trend that was seen in the 2017 numbers as the average AFC took a shift towards most heifers freshening in the desired age range of 22-24 months.

Now that we know what the AFC looks like for Holstein heifers in Pennsylvania, what does the performance of these heifers look like concerning milk production? The relationship between AFC and milk production has continued to be a debated and researched topic. A large-scale research study published in 2020 reported the results of contributing factors on milk yield in over 3.8 million Holstein heifers. This study revealed age at first calving to be an important determinant of milk yield (Van Eetvelde et al, 2020). Heifers calving earlier than 21 months are arguably not mature enough in size and body condition to perform well in the milking herd. In the Froidmont et al. study, it was reported that heifers calving prior to 22 months produced 11% less milk in their first lactation than older heifers (2012).

Figure 3 is a graph published in a previous Extension article highlighting 305D milk yield in Pennsylvania Holstein heifers in 2010 and 2017. Figure 4 uses updated information to show the number of Holstein heifers calving in 2019 and 2023 in relation to their age at first calving.

Some people prefer to use milk production on an energy-corrected basis. This method adjusts production based on a 3.5 percent fat and 3.2 percent component ratio for a more equal comparison. Figure 5 shows the same data but with energy-corrected milk. To determine this figure the following equation is used:

ECM = 0.327 x milk pounds + 12.95 x fat pounds + 7.2 x protein pounds

In comparing 2010 and 2017 data to 2019 and 2023, the trends are very similar. Milk production for first lactation animals seems to be maximized around 22-23 months. For those heifers entering the milking herd before 22 months, there is a significant reduction in their milk production. Van Eetvelde et al. (2020) revealed freshening younger heifers resulted in lower energy-corrected milk (ECM) and reduced revenues in the first lactation. This same study concluded AFC to be the most important contributing factor in milk yield showing an increase in ECM up to the age of 33 months (Van Eetvelde et al.,2020).

Van Eetvelde et al. (2020) reiterated first lactation milk yield is an important economic trait because of its predictor of lifetime performance and longevity. Heifers are an expensive part of any dairy operation. Ensuring that you are raising the healthiest, most productive heifer possible should be the goal of every heifer-raising program. Being able to track the performance of heifers is critical to measure the success of your calf and heifer program. If heifers are not reaching their milk production potential in the herd, a critical analysis of your program may be in order.

References:

Froidmont, E., Mayeres, P., Picron, P., Turlot, A., Planchon, V., and Stilmant, D. (2012). Association between age at first calving, year and season of first calving, and milk production in Holstein cow. The Animal Consortium. 7:4 pp 665-672.

Van Eetvelde, M., De Jong, D., Verdru, K., Van Pelt, M.L., Meesters, M., and Opsomer, G. (2020). A large-scale study on the effect of age at first calving, dam parity, and birth and calving month on first-lactation milk yield in Holstein Friesian dairy cattle. Journal of Dairy Science. 103:11515-11523.