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A pen of misfits: Don’t let your transition calves be the weak link

Kimberley Morrill, Keith A. Bryan and David Ledgerwood for Progressive Dairy Published on 22 February 2022

When we hear the phrase “challenges in the transition pen,” we often think about the lactating herd, paying particular attention to the transition from a dry, non-lactating animal to a highly productive lactating animal. We do this because we know that compounding challenges during this stage can have a dramatic impact on the entire lactation.

However, there is another transition period that is readily overlooked and can have a dramatic impact on the productive performance of that animal’s whole life. That transition period is the transition from a milk-fed pseudo-ruminant that gets highly digestible food delivered to key areas of the digestive tract, to that of a fully functional ruminant that now relies on a complex microbiome to extract the needed nutrients from harder-to-digest feeds. Combine this change with a housing transition, and we can be laying the framework for trouble.

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In other words, this is a high-stress change for an animal that has received two or more meals of warm milk per day at regular intervals, is used to daily interaction with a caregiver and had her own space. If you raise calves in a group setting from an early age, some of these stressors may be reduced compared to their individually housed counterparts. However, it’s hard to escape the inevitable transition from pseudo-ruminant to a fully functional ruminant.

We often think about the pre-weaning period as the most intense period of a heifer’s life. The calf is transitioning from being in utero – fully dependent on her dam for nutrition – to being a newborn dependent on milk, to becoming a functioning ruminant. From a labor and management standpoint, this time period can be just as challenging for people. Regardless of how stressful the pre-weaning period may be, we need to stay focused for a couple more weeks to ensure these calves transition smoothly to fully functioning ruminants and members of the replacement herd. Losing efficiencies gained during the pre-weaning period throughout the first couple of weeks after weaning is common, frustrating and expensive.

Why are transition calves problematic on so many farms, and what can be done to ensure a smooth and successful transition to fully functioning ruminants? Setting up the calf to be a healthy growing heifer, and eventually a member of the lactating herd, starts as early as the time she is born. How we feed and manage newborns and pre-weaned calves can influence gastrointestinal (GI) tract development, function and overall health.

1. Colostrum management. Colostrum consumed within the first hours of life stimulates the GI tract, initiating cell proliferation and turnover within the small intestine as well as cessation of macromolecule transport.

2. High-quality milk or milk replacer at a quantity that meets the nutrient requirements for both maintenance and growth.

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3. Access to a palatable starter and clean water is essential to support early rumen development.

4. Step-down approach to weaning versus cold turkey.

5. Minimize compounding of stressors. Don’t wean calves, vaccinate, relocate and dehorn all in the same day.

6. Feed a science-based, research-proven probiotic to help establish a healthy microbial population in the rumen and small intestine.

Microbial colonization of the GI tract during the pre-weaning phase plays a significant role in immune and metabolic development. Studies investigating the microbiota of the calf GI tract have reported less diverse bacterial communities at birth that increase in complexity and diversity with age, as a result of GI tract maturation and dietary changes. Immediate (and continued) feeding of colostrum is one of the first and best ways to influence both microbial colonization and GI tract development. Besides preserving a healthy microbiota in the GI tract, maintaining effective immune responses that can detect, prevent and eliminate invading pathogens is a key aspect of calf health.

The microbiome of the small intestine interacts with more than 70% of the immune system of the host. A healthy microbiome helps shape a healthy and balanced immune system. When dysbiosis occurs (microbiota are out of balance), we observe low-grade inflammation in the GI tract, more commonly referred to as “leaky gut.” This inflammation has been associated with diseases across all organ systems. While leaky gut is often associated with lactating cows, calves – especially those experiencing dietary changes near or at weaning – are just as susceptible. During periods of leaky gut in calves, food particles and pathogens can leave the lumen of the intestine and enter the circulatory and lymphatic systems. This leaves the calf’s naive immune system to deal with these insults.

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When the immune system is activated, there is also an energy shift. Energy, in the form of glucose and fat, and protein consumed through milk and starter that had been going toward growth is now going toward supporting an immune response.

Once a significant amount of starter or grain is consumed by the calf daily (approximately 0.25 to 0.4 pound per day), it takes about three weeks to develop the rumen to the point this digestive organ by itself has an established microbial population and enough absorptive capacity to allow the calf to continue normal growth once milk or milk replacer is stopped. Calves started on grain late or those that consume too little grain at a young age are at a disadvantage to their counterparts that have access to starter within the first days of life. During weaning, calves must transition from a milk-based diet primarily digested in the abomasum and small intestine to one based on solid feed intake and ruminal fermentation. Thus, weaning not only changes the site of digestion and absorption but also changes the nutrients available for absorption and post-absorptive metabolism.

If liquid feed is removed before rumen development has occurred, nutrients consumed may not meet the energy and protein requirements of the calf. This can lead to weight loss or stagnant growth until the rumen is developed and able to ferment the feed source available. During this period, growth is not the only function negatively affected. If energy and protein are limited, there may not be enough nutrients to support maintenance requirements and the immune system. This leads to a cycle of sick calves not able to respond to treatment and that become “poor doers.”

Supporting development of the microbiome in the rumen and lower GI tract, supporting normal barrier function, the immune system, feed intake and rumen development are all key aspects of a successful transition period. Throughout pre-weaning and at weaning, daily feeding of a science-based, research-proven probiotic can help support all these functions. Probiotics can enhance intestinal health by establishing supportive microbiota in the GI tract and aiding in the development of the rumen. It is well established that feeding lactic acid bacteria (LAB) during the pre-weaning phase is associated with improved weight gain after weaning due to a more efficiently functioning rumen. In addition to feeding LAB, feeding Bacillus subtilis and Bacillus licheniformis in milk replacer and starter rations led to increased starter intake and average daily gain (ADG) as compared to calves that did not receive a probiotic.

Success in the transition pen starts at birth and is subject to management of the calf during the pre-weaning period. Feeding a science-based, research-proven probiotic during the pre- and post-weaning period provides an opportunity to complement current management practices by supporting a healthy lower GI tract, a healthy calf and a smoother transition to a fully functioning ruminant.  end mark

PHOTO: Staff.

Keith Bryan is a technical service manager over ruminant DFM and silage inoculants with Chr. Hansen Animal Health & Nutrition. David Ledgerwood is a technical service manager over silage inoculants and cattle probiotics with Chr. Hansen Animal Health & Nutrition.

Kimberley Morrill
  • Kimberley Morrill

  • Technical Service Manager
  • Chr. Hansen
  • Animal Health & Nutrition
  • Email Kimberley Morrill

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