Nutritional components of neonatal diarrhea in calves

Juliette Wilms, Research Scientist at Trouw Nutrition R&D and PhD Candidate

Dr. Michael Steele, Associate Professor

Dr. David Renaud, Assistant Professor

University of Guelph

Digestive disorders remain the leading cause of calf morbidity and mortality on dairy farms within the first three weeks of life. Management and nutritional factors causing diarrhea in calves are numerous and the choice of feeding strategies is crucial. Low plane of nutrition (10 per cent birth body weight (BW)) remains common under the perception that high milk volumes (20 per cent birth BW) induce diarrhea and reduce preweaning starter feed intake. Feeding low planes of milk can cause alterations of the immune system that can lower the ability of calves to fight infections from enteric pathogens. While feeding adequate levels of milk to calves is important, the choice of liquid feed requires careful considerations.

What shall I consider when feeding whole milk?

A clear distinction should be made between saleable whole milk (WM) taken from the milk tank and waste milk including milk from treated cows that may contain antimicrobials. Feeding of saleable WM may be appealing when considering its optimal nutrient composition, however, feeding of raw milk (saleable WM and waste milk) can expose the calf to enteric pathogens that can be introduced either from the udder or when handling the milk and is therefore not recommended when hygiene on-farm cannot be ensured. The use of commercial on-farm pasteurization systems allows a substantial reduction of pathogenic bacteria in waste milk resulting in lower morbidity and mortality rates in calves. However, this does not alter the activity of most antimicrobials that may be present in waste milk, which can cause gut microbial imbalances predisposing the calves to enteric infections. In addition, the composition of waste milk can be highly variable: a high somatic cell count in milk leads to changes in the percentage of solids and in the mineral composition. Thus, waste milk is unlikely to represent a suitable option for feeding high levels of milk to calves.

What shall I consider when choosing a milk replacer product?

In contrast to waste milk, milk replacers (MR) provide a consistent nutrient supply to calves and do not contain antimicrobial residues. However, the use of low-quality raw materials in MR can increase diarrhea prevalence in calves.

Osmolality. Whereas WM has a low osmolality, defined as the number of particles in solution, MR osmolality can be very hypertonic (Figure 1 and 2). This is due to higher lactose and minerals, as well as a high percentage of solids per litre of solution (15 to 20 per cent) in MR. Other feeding practices such as the addition of milk balancers to WM, mixing oral rehydration solutions into MR or WM, as well as mixing errors will substantially increase milk osmolality. Although the link between osmolality and diarrhea in calves is not clear, high milk osmolality can reduce water absorption by the intestines leading to what is called “osmotic diarrhea”. Feeding of hypertonic MR to young animals may also impair gut health, which could facilitate susceptibility to pathogens causing diarrhea.

Protein quality. During the pasteurization and evaporation process of WM, high heat can damage the proteins as indicated by a low (less than three mg/g) whey protein nitrogen index (WPNI), a parameter which is only relevant for WM powders and dry skimmed milk-based MR. Damaging milk proteins alters the protein structure causing a reduction in protein digestibility in calves. Furthermore, in MR containing a high inclusion of non-dairy proteins, protein availability is reduced. Although some interesting vegetable sources such as hydrolyzed wheat proteins exist, unprocessed soy proteins include antinutritional factors causing gut mucosal damages. Unlike casein, whey and vegetable proteins do not curd in the abomasum leading to a faster gastrointestinal transit which can lead to an overflow of proteins arriving in the gut. This may negatively affect protein availability when feeding larger meals or elevated level of nutrient intake. Impairment of digestive processes related to the presence of low-quality proteins is often associated with severe digestive disorders, which is critical for calves younger than three weeks of age.

Figure 3. Macronutrient profile of MR for calves.

Fat amount and composition. Milk replacer for calves usually contain lower levels of fat (16 to 20 per cent dry matter (DM)) and higher levels of lactose (40 to 45 per cent) than WM (Figure 3). Increasing the fat content in MR was associated with a reduced number of medical treatments, lower fecal scores, and reduced mortality in preweaned calves. However, the fat composition should also be evaluated as MR contain alternative fat sources to milk fat which have a different fatty acid profile and triglyceride structure. Factors related to the oil saturation level, the oil dispersion, and emulsification can affect digestibility of dietary fats. When the composition of the oil largely differs from that of milk fat, diarrhea has been observed in calves.

Calves should be fed high quality WM or MR and the nutritional factors related to calf diarrhea should be evaluated by your nutritionist and veterinarian.

Take home message

  • Calves need an adequate energy supply
  • Waste milk and low-quality MR are not a suitable feeding strategy
  • Highly hypertonic MR (greater than 500 mOsm/kg) meals should be avoided 
  • When feeding WM powder and MR with high skimmed milk, WPNI should be above three mg/g
  • MR containing a large inclusion of vegetable proteins should be avoided, especially within the first three weeks of life
  • MRs with high fat levels are preferable and fat composition of MR should be as close as possible to that of WM