By Lisa Boonstoppel-Pot

     It was having kids that shifted Dr. Michael Steele’s focus from cattle physiology and nutrition to early life programming and how prenatal and postnatal nutrition turns a calf into a  cow that produces more milk.
    Steele has two children and of the two, it was the younger one he routinely took to the  barn. “She has been exposed to cows every week and now she wants to be a farmer,” said Steele. “It’s an example of real life programming.”
    Dairy farmers can apply the same principle for their calves and it starts with prenatal programming. The most developmental plasticity occurs prenatally and the dairy herd’s nutrition program affects it, especially as it fluctuates during the lactation and dry cow cycle. Typically, farmers tend to oversupply energy during the cow’s dry period which crashes into an energy deficit in early lactation and evens out during the time of conception. Scientists are learning that cows that were not metabolically stressed during pregnancy have offspring that produce more milk. A lack of nutrients causes methyl groups to bind DNA which blocks certain genomes from being expressed. Sort of like some switches get turned on and others do not, explained Steele.
    Heat stress also affects the prenatal calf. “We have found that in cows with less heat stress, their offspring absorb more immunoglobulin from colostrum,” said Steele. This, in turn, impacts growth and lifetime performance. Scientists are still learning more about this process but given what is known, Steele said it’s a wise investment to feed pregnant cows really well.
    Once the calf is born, the colostrum regimen begins. Steele knows farmers have heard this over and over again but he wanted to stress that it does not matter how the calves receive it -- bottle or tube feeding works just as well. The goal is to feed the calf three to four litres within the first hour of life and feed a second dose of colostrum at 12 hours.
    Farmers tend to feed these two two meals of colostrum and switch directly to milk replacer but Steele cautions this approach. Ideally, the transition should occur over four days. Research into calf intestines has revealed calves develop more villi (which increase surface area for food absorption) when colostrum feeding is extended. Calves with an abrupt transition have depressed intestinal growth.
    Measurement of colostrum quality will become more commonplace on farms as dairy calf specialists move beyond just measuring for immunoglobulins to other bioactives on colostrum. Refractometers are coming down in price and data collection is becoming easier to analyze thanks to dairy software programs.
    Don’t underfeed the calves either. In a study comparing calves fed five litres of day compared to calves fed 10 litres a day, the calves which drank more milk had significant growth compared to their counterparts. Also, in winter, calves require more energy to stay warm so milk or milk replacer volumes should increase.    
    In terms of the value of milk versus milk replacer, Steele said he is a fan of both. However, he thinks it is important to look at the ingredients of milk replacers in more detail. Milk replacers tend to have more lactose and ash, and less protein and fats. “These higher-level lactose replacers can decrease insulin sensitivity in the first week of life, so, in effect, the way the animals use energy is changed by feeding milk replacer,”said Steele.
What you really want to pay attention to is the osmolality in milk replacers. The osmolality of cow's milk is close to 300mOsm/kilogram which is optimal for the absorption and digestion of nutrients by calves. However, many milk replacers have levels above 400mOsm/kg with some closer to 600. A rating of 600 is not allowed in baby formula and Steele believes that level is also too high for dairy calves because it can cause leaky gut in calves. More research is being done to determine how milk replacers affect calves through their lifetime.
    The next step is weaning and having watched the process of weaning dairy calves versus beef calves, he believes the process for dairy calves is really unnatural. “We wean very early and very abruptly,” said Steele. Weaning at six weeks of age is too early and calves should be drinking milk until eight weeks of age, when they transition better, averaging daily gains of 650 grams per day.
    “Under eight weeks, calves are not physiologically ready to consume dry matter feed and will dip in growth. If you wait until eight weeks, the calves are ready to consume calf starter,” explained Steele. He also recommended making sure calves have enough water because water and starter intake are closely related.
    As the calves age, some dairy farmers feed them a lot of hay. However, with a rumen the size of a basketball in younger calves, you can only stuff so much hay in that space. He has been following some dairy farmers who feed a 15 per cent straw mixture with 70 per cent concentrate and said these calves consume more and weigh in with high average daily gains.
    Which leads to Steele's main point. He wants every farmer to weigh their calves to know their average daily gain. Record the birth weight. Then record the weaning weight. With this information, you can almost predict how much milk that calf will produce later in life. “It is possible to reach one kilogram of average daily gain,” said Steele. Next level is getting an automated scale and weighing calves routinely.
    “I go to so many farms where the farmer says the calves are doing great but they have no associated data to support it,” said Steele. He hopes the dairy industry will follow practices already in place in poultry and swine barns where feed is measured daily. Moreover, automated feeding could program each calf’s nutrition instead of hand-feeding calves of different ages the same thing.  Automation results in a lot of data, but with the right program, farmers can then use this information to come up with the ideal management strategy for their dairy calves. ◊