The Esophageal Groove
In nature, when a calf drinks from its mother, it drinks slowly with its neck stretched out. This position helps the calf make a lot of saliva. The saliva helps close a special passage called the esophageal groove, which sends the milk past the rumen and straight into the abomasum (the true stomach).
Calves are born wanting to suck on a nipple, and doing so makes them feel calm and satisfied. After drinking milk from a bucket, many calves still want to suck on something. If they’re kept with other calves, they may suck on another calf’s ears, navel, or teats. This can lead to health problems or damage the other calves.
When a calf sucks, it releases digestive hormones that help the body use nutrients and feel full. Suckling also helps close the esophageal groove so milk goes where it should—into the abomasum instead of the rumen.
The esophageal groove is a tube that connects the esophagus to the omasum. It lets milk skip the rumen, which is the part of the stomach used for fermenting feed. In newborn calves, the rumen is very small and holds about one pint.
Research has shown that the neck position while suckling doesn’t stop the groove from closing (Wise et al., 1942). However, if the calf’s head and neck are too high, milk might go down the wrong way. When a calf’s nose is lifted above its eyes, the throat opens toward the lungs, which can let milk or milk replacer slip into the trachea and cause coughing or pneumonia.
When feeding with a bottle or nipple bucket, keep the nipple low so the calf’s head stays level. This helps prevent milk from getting into the lungs.
How Calves Digest Milk
When milk reaches the abomasum, enzymes like rennin cause it to curdle. The liquid part, called whey, moves to the intestine for digestion. The curd is broken down in the abomasum and then also passes into the intestine to be absorbed.
The Critical Role of Saliva
Slow suckling helps calves produce more saliva, which maintains the stomach’s pH balance and aids in curdling the milk. Saliva contains enzymes that digest fat and even has natural germ-fighting properties.
The Dangers of Fast Feeding
If a calf drinks too fast, it won’t make enough saliva to digest milk properly. It may start sucking on other calves or parts of the pen to make more saliva; this is called cross-suckling.
Fast feeding can also cause milk to overflow into the rumen, where it ferments and causes stomach upset. Without enough saliva or curdling, undigested milk may reach the small intestine, leading to bacterial growth and scours.
Excited calves may also drink too fast, letting milk slip into the trachea. This can cause coughing right after feeding. This is common if bottles or nipples are too high.
Conclusion
It’s important that a calf drinks in the right position so that the milk travels its designated route to the abomasum. Doing so releases hormones that make them feel good and full. Slow drinking is crucial for the production of saliva to digest the milk properly.
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