For years, feeding a gallon of colostrum shortly after birth has been considered the gold standard for calf care. It’s simple, easy to remember and straightforward to train employees to follow. But today’s calves don’t all look the same. With more variation in size, some researchers are asking whether the same volume makes sense for every newborn.
During a recent “Dairy Health Blackbelt” podcast, Dr. Sabine Mann, associate professor at Cornell University, revisited the research behind that long-standing recommendation.
“One of the questions I have gotten frequently is, why are we feeding all calves a gallon of colostrum?” she says. “It’s a pretty widespread management strategy in the U.S. And if you try to dig into the literature of why that came about, there’s actually not that much evidence that that is the best approach for every calf.”
She notes that for an average 85- to 90-pound calf, four liters is probably appropriate. But not every calf falls into that range. When birthweights vary, feeding the same volume across the board may not always match what each individual calf truly needs.
Putting the Gallon Rule to the Test
To take a closer look at the gallon recommendation, Dr. Mann and her team conducted a study on a commercial dairy in collaboration with researchers at the University of Guelph.
They began by pooling colostrum to keep quality consistent across calves. From each pool, four calves were assigned different feeding levels based on a percentage of their body weight.
“We made a big pool of colostrum, and then we assigned four calves to that pool, and one calf got 6% and one calf got 8% and one calf got 10% and one calf got 12% so that was our range, six to 12,” Mann explains.
Rather than giving every calf the same fixed volume, the team adjusted how much colostrum each calf received relative to its size.
The intent was not to create a complicated system requiring producers to weigh every calf and calculate exact doses.
“This is not meant for people to weigh each and every single one of the calves and then figure out the milliliters,” Mann says. “But it’s for us to understand, is there an effect on the calf’s ability to take up IgG into circulation. And if there is, how would we translate this into actionable recommendations on farm.”
Ultimately, the study focused on whether feeding different amounts based on body weight would influence how well calves absorb the antibodies they need early in life.
More Isn’t Always Better
The study looked at how different colostrum volumes (as a percent of body weight) affected IgG in the blood, absorption efficiency, stomach emptying and calf comfort. As expected, bigger feeds gave calves more total IgG
“We found that the more volume they got within a certain quality of colostrum, the more IgG they had in their blood, which makes sense, right? The more you give, the more you get,” Mann says.
But the benefit slowed at the highest volume, 12% of the calf’s body weight.
“There was a declining return on investment, so to say, with increasing volumes,” Mann says. “There was a steep increase from 6% to 8% to 10% of body weight, but only a very small improvement in blood IgG concentration at 12% of body weight.”
This happened because calves absorbed a smaller proportion of the IgG when fed very large amounts.
“The proportion of the IgG in colostrum that actually appears in the blood was declining, meaning that the more volume you put into them, the less proportion the calf can actually take up into that in that window of time.”
When calves get a large meal, their stomach empties more slowly, so less colostrum reaches the intestine while the gut is still “open” to IgG absorption.
“We wanted to see if different volumes affect how the stomach empties colostrum into the intestine, and timing matters because the gut is only open for IgG absorption for a limited period.”
She compared it humans overeating during a holiday meal.
“We do this around Thanksgiving and Christmas, and we sit there and our belly hurts, right? Our systems know to slow down the gastric output in those situations, and that’s the same that happens in calves.”
Calf Comfort and Behavior
Dr. Mann’s team also looked at calf behavior, since small calves fed four liters often appear bloated or uncomfortable.
“We were interested in this notion from the field, and we did observe that the more volume we fed, the more we saw behavior associated with colic, like kicking the abdomen,” she says.
While lying time wasn’t significantly affected, higher volumes tended to reduce relaxed resting.
“We didn’t find a statistical effect in lying time, but those calves fed higher volumes tended to lie less in a relaxed position, similar to us at Thanksgiving,” she joked.
The “Goldilocks” Approach
When it comes to determining how much colostrum a calf truly needs, Mann describes the “Goldilocks” approach as the best option.
“I think we’re getting back to a Goldilocks approach where you want to have enough, but you don’t have to give too much,” she says. “Just the right amount is most beneficial to the calf.”
Based on this research, around 10% of a calf’s body weight is a solid target for an initial feeding. That amount provides enough immunoglobulins to support immunity without overwhelming the stomach, and it can be adjusted for smaller or larger calves.
Mann adds that while colostrum is packed with nutrients, extra benefits might be better delivered through multiple feedings rather than one very large meal.
“The nutritive value of colostrum should not be underestimated, but we also have to keep in mind the comfort of the calf,” she says. “Maybe it’s better given in separate feedings. A lot of farms have gone to feeding second feedings or even third feedings of colostrum.”
Practical Takeaways
While colostrum is essential for newborn calf health, Mann emphasizes that the goal isn’t to hit a fixed volume, but to give calves the right start while keeping them comfortable. She provides the following tips to use on the farm:
1. Know your herd’s average birth weight. “A good first step is to know the average birth weight of calves in your herd, since that can vary,” Mann says. “Once you know that, you can adjust the colostrum volume to match your average calf.”
2. Use a couple of standard volumes rather than one fixed size, “Many herds now use two standard volumes, like three liters and four liters. That way, even without a scale, you can look at a calf and decide: this one won’t be over 85 pounds, so it gets the smaller amount,” she says.
3. Consider second or third colostrum feedings. “Instead of giving all the colostrum at once, it can help to split it into two or three feedings if your farm can manage it,” Mann says. “Many people see benefits from this, though we could always use a bit more research to confirm.”
