When a heifer comes into heat, it’s important to take a peek at her birth date before making the decision whether or not to stick semen in her. Why? Because the age she calves could affect the amount of milk she produces throughout her first lactation, according to a 15-year study conducted in Belgium and the Netherlands.
While it might sound obvious, milk yield during the first lactation is an important economical trait. However, it can be a difficult trait to predict. According to researchers, one way to help forecast the amount of milk produced from these first lactation animals is to record their age at first calving (AFC).
Throughout the study, data was obtained from more than 4 million dairy heifers. However, animals with incomplete sire and dam information along with heifers who calved before the age of 21 months or after the age of 35 months were removed from the research. Additionally, animals who had a lactation of 250 days or less or 730 days or more were excluded. This dropped the number of animals within the study down to 3.8 million.
Data Deep-Dive
Over the 15 years, nearly 60% of the heifers calved between the ages of 24 and 27-months and gave on average 17,850 lb. of milk. In contrast, the lowest milk records came from heifers who calved in at 21-months, giving an average of 16,400 lb. of milk. Finally, the highest milk records were obtained from animals who calved during the 33 to 35-month range, as they gave approximately 18,700 lb. of milk during their first lactation.
While higher milk production is a significant contributor to profitability during the first lactation, it is not the only factor that should be considered.
For example, on one hand, heifers who calve earlier in life are able to offset their rearing costs, such as feed consumption, earlier and produce more replacement animals for the operation.
On the other hand, this study shows that younger heifers experience lower milk production, thus reducing the amount of revenue they generate during the first lactation. Lastly, while older heifers who calved in after 2.5 years of age produced more milk during their first lactation, they also consumed more feed, causing their individual rearing cost to skyrocket.
In conclusion, results of the study show that AFC can be an important determinant of milk yield during the first lactation. However, there are other important factors influencing profitability producers should consider before calving heifers in too early or too late.
