Nutrition of young rearing calves: digestion and feed utilisation

Dr Harma Berends, of Trouw Nutrition R & D, was the final speaker during the morning session on the second day of the international symposium that marked the official opening of Trouw Nutrition's new Calf & Beef Research Facility in April, 2016.

Her presentation, which revolved around aspects of digestion and feed utilisation in pre-weaned calves, included a discussion of altered nutritional requirements that are necessary when feeding a higher plane of nutrition, as suggested by Trouw Nutrition's LifeStart Program. After explaining what those larger meal sizes could mean for aspects like gastric emptying, digestion and possible insulin sensitivity issues, she concluded by outlining the challenges that lie ahead in formulating the LifeStart requirements that will optimize calf health while keeping an eye on sustainability.

The LifeStart requirements

Dr Berends began her presentation by pointing out that Trouw Nutrition, through its LifeStart Program, is moving away from restricted planes of nutrition to close to ad libitum feeding for pre-weaned calves. In so doing, daily intakes are basically doubling from 10% body weight (BW) to 20% BW. While the nutritional requirements formaintenance stay the same as calves grow while taking in these elevated planes of nutrition, the requirements for growth shift sharply with these accelerated growth rates.

And, as it turns out, requirements for specific nutrients don't just increase at the pace of growth, but rather they need to be balanced properly otherwise there is a risk of exceeding tolerance for some nutrients, which could lead to a variety of problems including nutritional diarrhoea, increased fermentation and insulin sensitivity. Therefore, Dr Berends cautioned that the right balance mustbe kept. She noted that finding that balance can be tricky, especially when trying to increase the sustainability of the dairy production chain by finding alternatives to dairy ingredients in milk replacers.

Meal size, gastric emptying and insulin sensitivity

What effects do the increased meal sizes of the LifeStart Program have on the physical responses of the calves? Dr Berends noted that one important aspect to examine when raising the plane of nutrition is what effect increasing meal size has on gastric emptying. While research has shown that the physical capacity of the abomasum is sufficient to hold increased meal sizes, Trouw Nutrition's own studies have shown that this greater meal size slows down abomasal emptying. While more research needs to be done about the effects of this, Dr Berends suggests that it most likely leads to positive outcomes. The calves could be slowing the rate at which the meal gets to the small intestine which could ultimately lead to higher total digestibility, and also to a potentially more gradual appearance of nutrients for the calf.

And how does the increased nutrient load affect insulin sensitivity? While there is some research that found that when the nutrition level is elevated from three weeks of age, there can be issues with insulin sensitivity, Dr Berends showed that when calves are directly programmed from birth with a strict colostrum protocol, and fed larger portions of calf milk replacer as in LifeStart studies on the subject, these elevated planes of nutrition neither affect glucose response nor lead to insulin sensitivity. This held true both before weaning and after. She therewith emphasized that adequate nutrition and management in the first weeks of life are the key factors for understanding insulin sensitivity in calves.

The challenges ahead

Dr Berends concluded her presentation by outlining the challenges that lie ahead. In conveying the big picture, she pointed to the ultimate desire to formulate LifeStart requirements that ensure future productivity while optimizing calf health which at the same time reduce dairy ingredient dependence, in order to contribute to greater sustainability. She emphasized the need to continue studying the previously mentioned insulin sensitivity and meal digestion issues. But, she also stated that more needs to be looked at in terms of short and long-term growth requirements and rumen development, water and mineral balance, the challenge of gut barrier function, and opportunities in feed technology.

Ultimately, while there are indeed still many hurdles, Dr Berends is optimistic that with the best facilities and the right focus, the complex puzzle of optimization of both digestion and feed utilization will be solved!

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