Current research has focused on feeding calves an elevated plane of nutrition during the pre-weaning period. Research has shown multiple benefits to this choice of calf management programme, including increased average daily gains, early onset of puberty, improved longevity and potential for higher milk production in the future.
Why has meal size been previously restricted?
In the past, it was common belief and practice to restrict calves to 2L of milk or milk replacer per meal, due to concerns that abomasal overload risks milk entering the rumen. However, this presumption has little scientific basis.
There are also some commonly-discussed concerns when feeding larger volumes of milk to young calves when it is split over a small number of feeds. It is thought feeding elevated planes of nutrition may impact on digestion and metabolism, and may have detrimental effects that persist post-weaning. These effects may include impaired insulin sensitivity.
Calves are essentially born monogastric. As the rumen develops it becomes less desirable for the lactose-rich milk to enter as it can change the pH and microbiota, which can cause digestive problems and reduce growth. Until now it has been presumed that the capacity of the abomasum is around 2L and that therefore milk meal size should reflect this.
Time to rethink calf feeding strategies
However, this is outdated thinking. Dr Michael Steele, Assistant Professor University of Alberta, Canada presented data from Ellingsen et al. (2016) reporting that three-week old calves will voluntarily consume up to 6.8L of warm whole milk in one meal without milk entering the rumen or any indications of abdominal pain or discomfort. This enhances the data that confirms the abomasum has a high capacity to accommodate fluids significantly greater than 2L at a time.
Insulin is an important hormone for controlling glucose levels within the calf; especially important for growth. In response to increased glucose levels in the blood, for example, after a meal, insulin is secreted from the pancreas. This is a key bodily function to utilise glucose for energy by the liver, and to build body fat and muscle. Insulin maintains glucose levels within the normal physiological range to prevent blood sugar levels from getting too high or too low; but in order to do this the body has to remain sensitive to the actions of insulin and not become resistant, which may happen with prolonged periods of increased blood glucose levels. Decreased insulin sensitivity in calves could lead to reduced efficiency of protein and energy utilisation and may predispose calves to metabolic disease later in life.
Trouw Nutrition R&D has completed a study, as part of the LifeStart programme, to further investigate the relationship between milk replacer intake and insulin and glucose kinetics. In this study the calves on the higher plane of nutrition (8L of milk replacer vs. 4L of milk replacer) had greater basal glucose levels and higher glucose and insulin concentrations after eating. This was to be expected as these calves were receiving a two-fold greater concentration of lactose in their diet. Importantly though, blood glucose and insulin concentrations in these calves fed a high level of milk replacer returned to baseline within 6 hours, demonstrating that insulin sensitivity is not impaired by plane of nutrition, and calves fed large meals can regulate glucose metabolism. At 4, 7 and 10 weeks of age there were no differences between the two groups of calves and their glucose metabolism. Furthermore, there were no differences in glucose metabolism before or after weaning noted in either group of calves. Therefore we can conclude that calves fed an elevated plane of milk replacer did not have decreased insulin sensitivity pre- or post-weaning, and as such had increased growth rates compared to calves fed on a conventional plane of nutrition.
Pre-weaning, calves do not yet have a functional rumen; therefore milk passes directly into the abomasum due to closure of the oesophageal groove. Abomasal (gastric) emptying is important for controlling the glucose level in the bloodstream; if the abomasum empties quickly following a large meal then there could be a large influx of glucose into the bloodstream. This may require higher levels of insulin secretion in order for the glucose to be utilised effectively and could result in prolonged periods of high insulin and glucose, affecting sensitivity to insulin. In this study, calves fed elevated levels of milk replacer had a slower abomasal emptying rate than the calves fed lower amounts of milk replacer. This is thought to be an adaptive mechanism of the calf to increased levels of milk replacer, thus regulating and stabilising blood metabolite levels.
Conclusions
Feeding calves on an elevated plane of nutrition (8L milk replacer vs. 4L of milk replacer in two meals per day) has significant pre-weaning advantages. The increased preweaning growth has been shown to increase overall lifetime performance, without the proposed adverse effects.
Georgina Thomas
Ruminant Technical Manager
Trouw Nutrition
Why has meal size been previously restricted?
In the past, it was common belief and practice to restrict calves to 2L of milk or milk replacer per meal, due to concerns that abomasal overload risks milk entering the rumen. However, this presumption has little scientific basis.
There are also some commonly-discussed concerns when feeding larger volumes of milk to young calves when it is split over a small number of feeds. It is thought feeding elevated planes of nutrition may impact on digestion and metabolism, and may have detrimental effects that persist post-weaning. These effects may include impaired insulin sensitivity.
Calves are essentially born monogastric. As the rumen develops it becomes less desirable for the lactose-rich milk to enter as it can change the pH and microbiota, which can cause digestive problems and reduce growth. Until now it has been presumed that the capacity of the abomasum is around 2L and that therefore milk meal size should reflect this.
Time to rethink calf feeding strategies
However, this is outdated thinking. Dr Michael Steele, Assistant Professor University of Alberta, Canada presented data from Ellingsen et al. (2016) reporting that three-week old calves will voluntarily consume up to 6.8L of warm whole milk in one meal without milk entering the rumen or any indications of abdominal pain or discomfort. This enhances the data that confirms the abomasum has a high capacity to accommodate fluids significantly greater than 2L at a time.
Insulin is an important hormone for controlling glucose levels within the calf; especially important for growth. In response to increased glucose levels in the blood, for example, after a meal, insulin is secreted from the pancreas. This is a key bodily function to utilise glucose for energy by the liver, and to build body fat and muscle. Insulin maintains glucose levels within the normal physiological range to prevent blood sugar levels from getting too high or too low; but in order to do this the body has to remain sensitive to the actions of insulin and not become resistant, which may happen with prolonged periods of increased blood glucose levels. Decreased insulin sensitivity in calves could lead to reduced efficiency of protein and energy utilisation and may predispose calves to metabolic disease later in life.
Trouw Nutrition R&D has completed a study, as part of the LifeStart programme, to further investigate the relationship between milk replacer intake and insulin and glucose kinetics. In this study the calves on the higher plane of nutrition (8L of milk replacer vs. 4L of milk replacer) had greater basal glucose levels and higher glucose and insulin concentrations after eating. This was to be expected as these calves were receiving a two-fold greater concentration of lactose in their diet. Importantly though, blood glucose and insulin concentrations in these calves fed a high level of milk replacer returned to baseline within 6 hours, demonstrating that insulin sensitivity is not impaired by plane of nutrition, and calves fed large meals can regulate glucose metabolism. At 4, 7 and 10 weeks of age there were no differences between the two groups of calves and their glucose metabolism. Furthermore, there were no differences in glucose metabolism before or after weaning noted in either group of calves. Therefore we can conclude that calves fed an elevated plane of milk replacer did not have decreased insulin sensitivity pre- or post-weaning, and as such had increased growth rates compared to calves fed on a conventional plane of nutrition.
Pre-weaning, calves do not yet have a functional rumen; therefore milk passes directly into the abomasum due to closure of the oesophageal groove. Abomasal (gastric) emptying is important for controlling the glucose level in the bloodstream; if the abomasum empties quickly following a large meal then there could be a large influx of glucose into the bloodstream. This may require higher levels of insulin secretion in order for the glucose to be utilised effectively and could result in prolonged periods of high insulin and glucose, affecting sensitivity to insulin. In this study, calves fed elevated levels of milk replacer had a slower abomasal emptying rate than the calves fed lower amounts of milk replacer. This is thought to be an adaptive mechanism of the calf to increased levels of milk replacer, thus regulating and stabilising blood metabolite levels.
Conclusions
Feeding calves on an elevated plane of nutrition (8L milk replacer vs. 4L of milk replacer in two meals per day) has significant pre-weaning advantages. The increased preweaning growth has been shown to increase overall lifetime performance, without the proposed adverse effects.
Georgina Thomas
Ruminant Technical Manager
Trouw Nutrition
