Other Management Articles
- Building A Herd of High-Producing, Healthy Cows with Low Involuntary Culling
- Culling Heifers: When and Why and the Impact on Herd Economics
- Economics Matter in Culling Decisions
- What is an ideal BCS at calving?
- Facts about Somatic Cell Counts
- First Layer of Defense Against Mastitis
- The When and Why of Milking Procedures
- Are Mastitis Vaccines a “Cure All”?
- Growing Heifers to Be Your Best Cows
- A Look in the Mirror
- Fertility Potential: The Bull + The Cow + The Inseminator + The Environment
The size and maturity of a heifer at first calving has an impact on her production and longevity as a cow, and heifer production may have a bigger impact on your herd average than you think. The cost of replacements to a dairy is significant, usually second only to feed and labor. Replacement costs may be lowered by an earlier age at freshening, but if these younger heifers are not of adequate size when they freshen there will be lost income from reduced production and higher culling rates. Focusing on heifer growth allows selection of the optimum age and size at first calving to get the most out of your replacement program.
To account for cow size variation between herds, goals for heifer size are based on percent comparison to mature cows in the herd. Mature weight for a herd is estimated by the average weight of mid-lactation cows (about 100-150 DIM) in their 3rd or greater lactation, with BCS 2.75-3.75. Table 1 shows recommended growth targets at various stages with examples of weights and average daily gains for each stage. Heifers should be 95% of mature weight as close-up springers, which will be about 85-90% of mature weight after calving. Figure 1 shows data collected by a farm in Europe and shared with the World Wide Sires technical team. Weight at first calving was measured and milk production data was collected through the first and second lactation. The heavier the animals were at first calving, the better they performed in both the first and second lactation. Additionally, heavier heifers were more likely to survive to the second lactation.
Of course, size and age are related, and it can be difficult to distinguish the effect of each in an individual herd where weight data is not available. From controlled research studies and experience with herds where weight is measured, the size and weight of the heifer is more important than age. In other words, heifers that calve at 650 kg in a Holstein herd where mature weight is about 700 kg produce the same in first lactation whether they are 22 months or 24 months of age. But, in herds with heifers that have not reached mature weight by 22 months, there is a clear trend for higher milk production with greater age at first calving. It is important to note that these weights must be achieved through body frame growth, not fat. Body condition score for heifers at calving should be 3.25 – 3.5, meaning the ligaments from the spine to the hooks and from tail head to pins should still be visible and not hidden by fat deposits. Over conditioned heifers have more calving problems, more disease post calving, and poorer conception.
Managing for heifer size at calving requires knowing the average daily gain after heifers are pregnant, and back-calculating to determine the size they need to be at conception to achieve adequate size during the 280 days of pregnancy. A general goal is that heifers should be 55% of mature weight at breeding. Seasonal variation in growth may occur due to higher energy demands during inclement weather. Managers should account for seasonal reductions in daily gains when determining goal size at breeding.
Taking advantage of heifer growth potential during milk feeding and post-weaning is key to reaching growth targets at breeding and calving. Heifers should at least double birth weight by weaning time, 220% of birth weight is achievable and even better. Weaning should be managed to maintain positive growth during and after the transition to solid feed. Disease early in life has an impact on both growth and later productivity, especially calf pneumonia. Controlling disease must be a part of the strategy to maximize first lactation production potential.
The impact of heifer growth on first lactation production in turn impacts overall herd production. Usually, first lactation cows make up 30-40% of a milking herd so their milk production significantly influences herd average daily milk production. A common trend across herds is that 10-12 week milk production for first lactation animals matches herd daily production average. A good way to assess the performance of your first lactation animals is to compare average peak milk for first lactation and second lactation cows to average peak milk for 3rd and greater lactation. First lactations should be 70-75% and second lactations should be 92-95% of third and greater lactations. To push your herd performance, have heifers that are ready to perform at their maximum potential from their first calving on.
Figure 1. 305 day projected milk yield (kg) by weight at calving (kg) for first and second lactation. First lactation is shown in blue and second lactation in orange, dashed lines represent the linear trend lines.
