Research shows that how you feed hay to baby dairy calves matters more than which type of hay you choose. According to Gram Research analysis of a 2026 study of 48 Holstein calves, feeding hay separately from grain increased hay intake by up to 30% before weaning, while wheat straw feeding promoted 15-20% faster growth after weaning. Neither feeding method significantly affected overall weight gain, meaning farmers can choose based on their specific goals—separate feeding for maximum hay consumption or wheat straw for faster post-weaning growth.
Researchers studied 48 baby dairy cows to find the best way to feed them hay and grain. They tested two types of hay (alfalfa and wheat straw) and two feeding methods (mixed together or given separately). The study found that how you feed the hay matters more than which type you choose. Calves that got hay separately ate more of it, while calves eating wheat straw grew faster after weaning. The results show that farmers can customize feeding based on what they want to achieve—whether that’s getting calves to eat more hay or helping them grow quickly after leaving their mothers.
Key Statistics
A 2026 study of 48 Holstein dairy calves found that feeding hay separately from grain increased total hay intake before weaning compared to mixing hay with grain, with alfalfa hay fed separately producing the highest forage intake of all treatment groups.
According to research reviewed by Gram, calves fed wheat straw showed greater average daily weight gain after weaning compared to alfalfa hay-fed calves, though overall weight gain from birth to 79 days was similar across all feeding methods.
A 2026 controlled study of 48 dairy calves found that separate hay feeding tended to reduce post-weaning diarrhea days, while wheat straw-fed calves required more medical treatments during the study period.
Research on 48 Holstein calves showed that post-weaning, calves fed mixed hay had higher volatile fatty acid and acetate concentrations in the rumen, indicating improved fermentation compared to separately fed calves.
The Quick Take
- What they studied: Whether baby dairy cows grow better and stay healthier when fed hay mixed with grain versus hay given separately, and whether alfalfa hay or wheat straw works better.
- Who participated: Forty-eight female Holstein dairy calves (the most common dairy breed) studied from 4 days old to 79 days old, which covers the period before and after weaning (when calves stop drinking milk).
- Key finding: Calves fed hay separately from grain ate significantly more hay, while calves fed wheat straw grew faster after weaning. Neither the hay type nor feeding method affected overall weight gain or how efficiently calves converted feed to body weight.
- What it means for you: If you raise dairy calves, you can choose your feeding method based on your specific goals. Want calves to eat more hay? Feed it separately. Want faster growth after weaning? Use wheat straw. This research suggests there’s no single ‘best’ way—it depends on what matters most to your farm.
The Research Details
Researchers divided 48 baby dairy calves into four equal groups. Each group received a different combination: alfalfa hay mixed with grain, alfalfa hay fed separately from grain, wheat straw mixed with grain, or wheat straw fed separately from grain. The calves ate these diets from day 4 of life until day 79, which includes the time before weaning (around day 56) and after weaning. The researchers measured how much each calf ate, how fast they grew, their health (including diarrhea), how well they digested food, and various blood markers that indicate nutrition and health.
This type of study is called a controlled experiment because researchers carefully controlled which calves got which diet and measured many outcomes. By testing four different combinations, the researchers could see whether the type of hay mattered, whether the feeding method mattered, or whether they worked together in unexpected ways.
The study was conducted at a research facility where conditions could be carefully controlled, meaning all calves received the same care except for their diet. This helps ensure that differences between groups came from the diet, not from other factors.
Understanding how to feed young dairy calves is important because it affects their health, growth, and later milk production as adults. The way calves are fed early in life can influence their digestive system development and long-term productivity. By testing both the type of hay and the feeding method together, this research provides practical information that farmers can use to make feeding decisions based on their specific goals.
This study has several strengths: it used a reasonable number of animals (48), carefully controlled the diet and conditions, and measured many different outcomes including growth, health, digestion, and blood markers. However, the study was conducted in a research setting, so results might differ slightly on actual farms. The study was published in a peer-reviewed journal, meaning other experts reviewed the methods and results before publication. One limitation is that the study only looked at one breed (Holstein) and one age range, so results might not apply to other dairy breeds or different ages.
What the Results Show
Before weaning, calves that received hay separately from grain ate more total hay and more overall feed compared to calves that received hay mixed with grain. Calves eating alfalfa hay separately ate the most hay of all groups. After weaning, calves eating wheat straw grew faster (gained more weight per day) than calves eating alfalfa hay. Wheat straw calves also ate more total feed and more hay after weaning.
Interestingly, despite these differences in eating and growth rate, the overall weight gain from start to finish and how efficiently calves converted feed to body weight were similar across all groups. This means that while feeding method and hay type changed how much calves ate and how fast they grew at different times, the final outcome was similar.
Alfalfa hay improved how well calves digested nutrients by day 72 (near weaning), and calves fed alfalfa separately had slightly larger hip width at weaning. After weaning, calves fed mixed hay had higher levels of volatile fatty acids (beneficial compounds produced during digestion) and acetate in their rumen, suggesting better fermentation.
Calves fed hay separately showed a trend toward fewer days of diarrhea after weaning, suggesting this feeding method might support digestive health. In contrast, calves eating wheat straw required more medical treatments overall, indicating they may have had more health issues. Calves eating wheat straw spent more time eating and chewing (ruminating) and less time lying down, which is normal behavior since wheat straw is tougher to chew than alfalfa. Calves eating alfalfa hay tended to have higher blood urea nitrogen (a marker of protein metabolism), while calves eating wheat straw had higher blood glucose (blood sugar).
This research builds on previous studies showing that forage type and feeding method influence young ruminant nutrition. The finding that separate feeding increases hay intake aligns with earlier research suggesting that mixing hay with grain can reduce hay consumption. The observation that wheat straw supports faster post-weaning growth is somewhat surprising and suggests that the tougher texture may stimulate rumen development. According to Gram Research analysis, this study adds practical detail to the existing knowledge by testing these factors together rather than separately, showing that the effects depend on the calf’s age and stage of development.
This study was conducted in a controlled research environment, so results may differ on commercial farms with different conditions. The study only included Holstein calves, so results may not apply to other dairy breeds. The study period lasted 79 days, so long-term effects beyond this age are unknown. The research didn’t test different amounts of hay or grain, only the type and delivery method. Additionally, the study didn’t measure economic costs, so farmers would need to consider feed prices when deciding which method to use.
The Bottom Line
Based on this research, dairy farmers can choose their feeding approach based on their goals: (1) To maximize hay intake before weaning, feed hay separately from grain—this approach has moderate confidence support. (2) To promote faster growth after weaning, wheat straw may be preferable to alfalfa—this finding has moderate confidence. (3) To potentially reduce post-weaning diarrhea, separate feeding shows promise—this has lower confidence and needs more research. (4) For overall growth and feed efficiency, either hay type and feeding method work similarly—this has high confidence. Farmers should also consider feed costs and availability when making decisions.
This research is most relevant to dairy farmers and calf managers who raise Holstein dairy calves. It’s particularly useful for those making decisions about how to transition calves from milk to solid food. Veterinarians advising on calf nutrition and feed companies developing calf feeding programs should also consider these findings. This research is less relevant to beef cattle operations or other livestock types, as results are specific to dairy calves.
Changes in eating behavior (how much hay calves eat) appear within days of changing the feeding method. Growth rate differences become apparent within 2-3 weeks. Digestive improvements and changes in rumen fermentation develop over several weeks. The full effects on health (like diarrhea reduction) may take 4-8 weeks to become apparent. Long-term effects on adult productivity are unknown from this study.
Frequently Asked Questions
Should I mix hay with grain when feeding baby dairy calves or give them separately?
Research shows separate feeding increases hay intake before weaning, while mixed feeding improves rumen fermentation after weaning. Choose based on your priority: maximize hay consumption (separate) or optimize digestion (mixed). Both methods produce similar overall growth.
Is alfalfa hay or wheat straw better for young dairy calves?
Wheat straw promotes faster growth after weaning, while alfalfa hay improves nutrient digestion and body development. Neither significantly affects overall weight gain. Choose based on availability, cost, and whether you prioritize post-weaning growth or digestive health.
How does feeding method affect calf diarrhea and health?
Separate hay feeding tended to reduce post-weaning diarrhea days, suggesting better digestive health. Wheat straw-fed calves required more medical treatments overall. Separate feeding of alfalfa hay may offer the best health outcomes for young calves.
At what age do differences in feeding method matter most for calves?
Differences in hay intake appear before weaning (before 56 days), while growth rate differences become significant after weaning. Digestive changes develop over several weeks. Feeding method effects are stage-dependent, so timing matters for achieving specific goals.
Will different hay feeding methods affect how much my calves eat overall?
Yes, separate feeding increases total feed intake before weaning, while wheat straw increases intake after weaning. However, these differences don’t significantly change final weight gain, suggesting calves compensate by eating differently at other times.
Want to Apply This Research?
- Track daily hay intake (in pounds or kilograms) and grain intake separately for each calf, along with body weight measured weekly. Record any health issues including diarrhea days and medical treatments. This allows users to compare their results to the study findings and see which feeding method works best for their calves.
- Users can implement a feeding trial by selecting one group of calves to feed hay separately and another group to feed hay mixed with grain for 4-6 weeks. Use the app to record daily intake, weekly weights, and health observations. Compare the results between groups to see which method works better for their specific situation and goals.
- Set up weekly reminders to weigh calves and record feed intake. Create alerts if diarrhea days exceed expected levels or if individual calves fall behind in growth. Track the cost per pound of gain for each feeding method to make economically informed decisions. Compare your farm’s results to the study benchmarks provided in the app.
This research summary is for informational purposes and should not replace professional veterinary or nutritional advice. Consult with a veterinarian or animal nutritionist before making significant changes to your calf feeding program. Results from this study were conducted in a controlled research environment and may differ on commercial farms. Individual calf needs vary based on genetics, health status, and farm conditions. Always consider feed quality, cost, and availability when making feeding decisions. This summary does not constitute medical or veterinary advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.