Genomic testing is a popular way to rank heifers as part of a strategic breeding plan. But it’s not the only way. If you’re looking to not only maximize genetic progress, but also future profit, there might be alternative methods to decide which heifers to cull and which to keep.
ADG as a female selection tool?
References to average daily gain (ADG) typically come from the beef industry and more recently, dairy nutritionists and researchers. Dairy-focused studies have proven that individual dairy farms can see the impact of ADG on future milk production potential. In fact, a study from Cornell University showed that for every one kilogram of pre-weaning ADG, calves produced 1,113 kilograms more milk during their first lactation1.
Weighing individual animals at set points early in life to determine their average daily gain can be an effective means to predict which animals will produce the most throughout their first and later lactations.
Take the example below. On this 2,850-cow Holstein farm in Wisconsin, weights are taken on each individual calf at birth and weaning, and calculated within their herd management software to figure out the ADG of each animal.
|Table 1||Number of cows||ADG||Avg. 1st Lactation 305-day ME milk|
|Group 1: Top 25% for highest ADG||332||2.18||33105 lb|
|Group 2: Bottom 25% for lowest ADG||308||1.67||31838 lb|
Here, we’ve broken down all first lactation animals into quartiles based on their initial average daily gain. The top animals for ADG gained nearly 2.2 pounds per day from birth to weaning, while the bottom 25% of animals for ADG gained 1.67 pounds per day during that time.
Fast forward two years to when these calves have entered the milking herd, and that difference in average daily gain equates to a real and noticeable 1267 pound per animal difference in first lactation 305-day ME milk production. This is on par with the results from 2012 Cornell University study mentioned above.
Genetics still matter
If we take this analysis one step further, we can see that genetics are able to express themselves to a fuller advantage in healthier calves that grow more each day.
When we split the groups from the same analysis shown above in Table 1 to do two separate genetic assessments we can see how animals in each group perform in relation to their genetic predictions. This shows us whether ADG affects whether an animal can produce to their genetic potential.
Table 2 takes only the first lactation cows that were among the top 25% of heifers for highest birth to weaning ADG. Within this high ADG group of animals, we compare 305ME milk production based on parent average for PTA Milk within that group.
|Table 2: Highest ADG animals||Number of cows||ADG||Parent Average PTA Milk||Avg. 1st Lact 305ME Milk|
|Top 50%: Highest Parent Avg PTAM||166||2.19||586||34503 lb|
|Bottom 50%: Lowest Parent Avg PTAM||166||2.17||105||31725 lb|
Here, it shows that among only the calves with the highest average daily gain, those animals with the higher parent average for PTA Milk calved in to produce nearly 2800 pounds more milk than the animals with a lower parent average for PTA Milk.
Table 3 looks at this the same way, but only splits out just the first lactation cows that were in the bottom 25% for lowest birth to weaning ADG. When we compare milk production within that isolated low ADG group, we see that a higher parent average for PTAM equated to just over 1800 additional pounds of milk in the first lactation compared to the animals with the lowest parent averages for PTAM.
|Table 3: Lowest ADG animals||Number of cows||ADG||Parent Average PTA Milk||Avg. 1st Lact 305ME Milk|
|Top 50%: Highest Parent Avg PTAM||152||1.68||569||32768 lb|
|Bottom 50%: Lowest Parent Avg PTAM||152||1.67||55||30958 lb|
Within both groups of animals a higher parent average for PTAM meant even more milk than predicted by genetics. However, when you compare the difference in 1st lactation 305MEs you can see that the high ADG group outpaces the low ADG group by nearly an additional 1000 pounds of milk in the first lactation.
This means that when calves are given the best nutrition and care, and achieve higher average daily gains, their genetics are better able to express themselves beyond what’s even predicted.
Strategic management decisions
With this proof in mind, if your farm’s situation dictates culling extra heifers, it’s best to do that in a strategic way. While genomic testing certainly has its merits for this purpose, the power of monitoring and measuring ADGs can serve as an effective alternative.
If the animals that perform well early in life go on to perform better than herdmates later in life, it’s an easy decision to keep the fastest growing animals in your herd. If you cull those calves that perform at a sub-par level from the start, you can avoid the feed costs for animals that will produce less than herdmates in the future, and avoid housing for animals that you may not have room for on your farm.
Knowing that those healthy calves will put extra pounds in the tank down the road also enforces the power of proper and progressive calf nutrition and a sharp focus on overall calf health. Even when times are tight, the future of your milking herd should not be put on the back burner.
Points to ponder
When implementing a strategic plan to cull heifers, consider weighing each individual calf at various milestones in her life to determine average daily gains. A ranking based on ADG to sort which heifers to keep and which to cull can have a big impact on overall future costs of production.
Don’t let the genetics you select go to waste. An animal’s genetics are expressed best when she receives the best nutrition and care from day one. The amount each calf gains per day, even in those first few months, will make a major impact on future production potential.