She’s weaned, now what? Setting heifers up for success in their post-weaning transition
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EmailBeing aware of and managing for shifts in the temperature humidity index in calf housing will help calves be healthier, develop better and be one step closer to entering the milking herd.
The journey from calf to developing heifer to productive cow doesn’t stop at weaning. The period from weaning to four months of age is one of the most critical growth phases in a heifer’s development, making this an essential component of a farm’s management plan. According to Jud Heinrichs, Professor Emeritus of Dairy Science at Penn State University, this transition phase is where proper rumen development, nutrition management and thoughtful housing strategies have a direct effect on a heifer’s future performance. With the right benchmarks and management practices, calf care teams can ensure a smooth transition—supporting growth, preventing setbacks and laying the foundation for lifetime productivity.
From monogastric to ruminant: The importance of early rumen development
At birth, calves function as monogastric animals. The first 8–12 weeks of life are critical for transforming the rumen into a large, efficient fermentation chamber lined with papillae that absorb nutrients. This development is driven by Volatile Fatty Acids (VFAs), specifically:
- Acetate and Propionate for energy and growth
- Butyrate to fuel papillae development directly
Starter grain, particularly its starch content, plays a key role in stimulating VFA production. Calves offered both milk and grain before weaning show significantly better rumen development compared to those raised on milk alone. Research highlights that pre-weaning grain intake is one of the strongest predictors of future performance, in milk production and growth rates. Studies from Pennsylvania, Cornell, Illinois and Minnesota consistently show that calves consuming more starter grain before weaning achieve better growth rates and produce more milk later in life. However, Heinrichs cautions against overstating this benefit. While early grain intake can add approximately 130 lbs .of milk per 0.2 lbs. of pre-weaning gain, these early advantages explain only about 2.3% of total lactation output. It's a meaningful boost—but just one piece of the productivity puzzle.
Calves that didn’t consume enough grain pre-weaning are at higher risk of ruminal acidosis when exposed to larger grain loads post-weaning. Signs include erratic feed intake, lethargy, diarrhea and poor growth. Prevention starts with ensuring calves are eating at least 1.5–2 lbs. of grain daily before weaning and monitoring closely during the first two weeks after milk removal.
Post weaning, aim for 4–5 lbs. of grain daily, gradually introducing forage. Excessive forage, especially early on, can lead to reduced gains and the dreaded "hay belly." Start with minimal amounts, allowing calves to naturally ramp up intake as they approach 16 weeks, targeting around 1% of body weight in Neutral Detergent Fiber (NDF). Whether using component feeding or a Total Mixed Ration (TMR), work with your nutritionist to manage protein levels and avoid abrupt dietary changes.
With weight gain being the clearest indicator of a successful transition, use a calf-specific weight tape or scale to monitor progress, checking weights at weaning and again after one month. Stagnant or negative growth signals issues with rumen development, nutrition or potential health concerns.
Aim for 1.3–1.8 lbs./day of weight gain from birth to weaning and 2.0+ lbs./day post-weaning.
Managing the transition pen: Setting calves up for success
The 2–4 weeks post-weaning, which is a transition period for calves, requires careful management to avoid growth slumps and health issues. Key recommendations include:
- Delay moving calves into group housing for several days after weaning to reduce stress.
- Maintain group sizes of 4–8 calves to limit competition and disease risk.
- Provide at least 18–24 inches of bunk space per calf and ensure easy water access.
- Focus on ventilation, dry bedding and a clean environment to promote comfort and health.
Heinrichs emphasizes that reducing stress and maintaining consistent routines are just as important as nutrition. Always move calves into transition pens as a group to avoid social disruption. Delay vaccinations or other high-stress procedures until calves are well-adjusted. Keep a close eye out for common challenges like:
- Coccidiosis, especially when adjusting feed additives
- Respiratory issues, indicated by nasal or ocular discharge
- Fly pressure and other environmental stressors
Dry bedding, proper ventilation and clean water access remain foundational to calf health during this phase.
A smooth transition builds a strong foundation
The post-weaning period is a pivotal time that requires proactive management. By focusing on rumen development, balanced nutrition, environmental comfort and careful monitoring, producers and calf care teams can ensure that heifers can become productive, healthy cows in the future. With the right strategies in place, the question isn’t just “She’s weaned, now what?” it’s “How far can she go?”
