Top strategies to support intestinal barrier function in nursery calves

The intestine plays a vital role in nutrient absorption, neural communication, immune sensing and serving as a barrier between intestinal contents and the bloodstream (Figure 1). When intestinal dysbiosis occurs — an imbalance in the microbial community — it can lead to decreased diet digestibility, microbiome shift, increased permeability (“leaky gut”), immune activation, pathogen growth and disrupted neuroendocrine signaling. Even brief stress can trigger prolonged dysbiosis and inflammation.

Systemic inflammation increases glucose demand and suppresses feed intake, reducing growth and feed efficiency (Figure 2). It also raises susceptibility to secondary pathogens and alters gene expression. A moderate immune response can increase glucose demand by 200 grams/day, equating to 800 kcal/day — enough energy to support 0.5 pounds/day of weight gain. A 1-degree Fahrenheit fever can reduce energy availability by 12-13% (Carroll and Forsberg, 2007).

Farm data links scours intensity and duration in calves aged seven to 14 days to increased respiratory disease risk around one month of age. Researchers continue to explore how intestinal integrity influences respiratory health. Below are 10 strategies to support intestinal barrier function in nursey calves.

1. Ensure a clean and healthy maternity environment:

Early microbial inoculation is shaped by maternal vaginal ecology, bedding and colostrum hygiene. Strategies include improving maternal gut health, maintaining clean maternity bedding and heat treating colostrum.

2. Optimize milk feeding volumes:

Milk meals should meet maintenance and growth needs without overwhelming digestion. Signs of underfeeding include vocalization and persistent searching for more milk post-feeding. Oversized meals can lead to undigested nutrients, bacterial overgrowth and inflammation.

3. Preserve milk nutrient integrity:

Milk fat is key to intestinal integrity. Small fat globules, preserved by the fat globule membrane, enhance digestibility and support beneficial bacteria. Disruption from poor pasteurization or aggressive mixing can impair digestion and increase inflammation. Milk replacer fat, encapsulated in protein and emulsifiers, is similarly sensitive to mixing and temperature.

4. Enhance milk with targeted additives:

• Mannan oligosaccharides (MOS) bind pathogens, stimulate immunity and support beneficial bacteria.
• Medium-chain fatty acids (MCFAs), found in cow’s milk and coconut oil, are digestible and antibacterial.
• Bovine plasma provides amino acids and immunoglobulins for repair.
• Direct-fed microbials (DFMs), such as Bacillus subtilis, produce bacteriocins and fungicins that inhibit pathogens communication and biofilm formation.
• Trace minerals like zinc methionine or zinc hydroxychloride support intestinal barrier integrity.

5. Minimize pathogen exposure:

Pathogens such as Clostridium, E. Coli, Salmonella, Cryptosporidium, Coccidia, coronavirus and rotavirus compromise gut health. Vaccination, biosecurity, sanitation and hygienic feeding practices are essential.

6. Promote adequate water intake:

Hydration supports digesta flow, nutrient absorption, and microbial ecology. Dehydration impairs immune function and intestinal membrane fluidity.

7. Encourage early starter grain intake:

Early grain intake boosts microbial diversity and gut maturation. It stabilizes nutrient flow and lowers gut pH, which discourages pathogens and supports beneficial microbes. Provide calves with consistent access from week one through the nursery phase.

8. Formulate starter feeds:

Balanced carbohydrates and adequate fiber promote rumination, rumen development and intestinal health.

9. Implement a gradual weaning process:

Gradual weaning starting at seven to eight weeks allows for increased grain intake and maintains nutrient supply. Abrupt weaning can compromise intestinal integrity.

10. Maintain environmental consistency:

Thermal stress reduces gut integrity. Consistent feeding schedules improve digestion and support barrier function.

Following these 10 strategies will increase intestinal integrity in nursery calves and promote calf growth and health. Monitor calf bodyweight gain and treatment during the nursery phase to determine if the changes you make are beneficial to your nursery calf program.