Ensuring calves immunity, role of gut maturation and nutrition

During the first month of life, baby calves will experience lot of changes in addition to extensive immunity and gut maturation. Moreover, it is well described that the first two months of life of calves are critical for future performance (Abuelo et al. 2021; Buczinski et al. 2021). This article provides a better understanding of immune system maturation and function and its link with gut maturation to design successful calves management nutrition.

Marie-Valentine Glica
Global Ruminant Marketing Manager
Lallemand Animal Nutrition

At birth, before developing its own immune system, the calf is protected thanks to the maternal antibodies (Y) from colostrum: this is known as passive or innate immunity, which is why colostrum intake is key in the first hours and days of life and it should be correctly managed. This is particularly challenging for male dairy calves which are of less value and eventually transported long distances at only a few weeks of age. It is not before two weeks of age that the calf starts to acquire its own immunity, called adaptative or active, with the production of antibodies by B-cells. In between, there is a gap called the immunity window or sensitive window, where the calf’s natural defenses are particularly low and critical (Figure 1).

Figure 1. Calves immune system maturation and main external stressors from birth to 2 months old (Adapted from Hulbert & Moisá, 2016.).

During the first month of life, while immunity is still weak, the calves experience a lot of external stressors (birth, transportation, transition from liquid to solid feed, dehorning, etc.). All these stressors increase the risk of morbidity and mortality by making the immune system more vulnerable. This can lead to visible signs of poor immune defenses such as digestive and respiratory diseases.

The first opportunistic disease to appear is enteric disease during the first three weeks – E. Coli, C. Perfringens, Salmonella -, followed by pneumonia from the second week until adult age.

Urie et al. described a morbidity around 34% with a mortality of 5% in 1 month old calves. The major causes of mortality and morbidity are digestive troubles (32% and 51% respectively). In US dairy calves operations, economic consequences of long-term diarrhea outbreaks have been evaluated to almost 71.15$ per calf (USDA, 2014).

Immune defenses have three main components: the physical barriers, the innate immunity, and the acquired (also called passive) immunity.

1. The physical barriers prevent any pathogens from entering the body. Some physical barriers can act as an alarm signal for the farmer: coughing, sneezing, vomiting, urinating… And others are invisible at producer level: skin, mucus membranes and gut epithelium, enzymes in the saliva and the intestine and a balanced microbiota.

2. The innate immunity that will respond quickly to the presence of pathogens and try to destroy them. Its activation leads to inflammation. This system uses chemical messengers such as cytokines and activates immune cells (white blood cells, WBC) such as macrophages that can be used as markers of inflammation.

3. The acquired or passive immunity that is specific and has a memory role. It must be acquired and developed through exposure to pathogens along the animal life. It’s the system exploited by vaccination: exposure to disactivated pathogen that will ’teach’ the immune system how to recognize this pathogen to be able to neutralize it at the next encounter.

An organism needs these three components working at their optimum to ensure health and growth. The gut plays an important role in the immune defense system as innate and acquired immunity are concentrated within the gastro-intestinal lymphoid tissue (GALT). This GALT gathers up to 70% of the body’s WBC.

Using nutritional additives to support the physical barriers such as gut integrity and mucin production in addition to stimulating a balanced immune response at gut level can be a winning strategy to improve pre-weaned calves’ performances.

The main goals for the producer pre-weaning are to ensure:
a balanced intestinal microbiota,
a well-prepared digestive system
a well-functioning immune response.

Good management practices and nutrition are keys to help young ruminants cope with early pathogens and digestive challenges. In this context, a new generation feed ingredient YANG including specifically selected yeast fractions has been proven to help maintain the health of calves and other young ruminants by reinforcing immunity and improving gut microbiota balance.

YANG is a multi-strain yeast derivative formulated to strengthen animals’ natural defenses with a patented, synergistic effect on the immune response. It combines two complementary actions that reinforce animals’ natural defenses:
– A strong pathogen binding capacity, effective against a wide range of undesirable bacteria compared to single-strain yeast derivatives
– A broad and balanced immune modulation (patented), providing higher immune system modulation without risk of over-stimulation sometimes observed in cases of single immune receptor activation by traditional yeast derivatives.

This was confirmed by a recent trial conducted at Lublin University and presented during the 2022 World Buiatrics Congress (Villot et al., 2022). This trial evaluated the benefits of YANG to the fecal microbiota and health status of young calves fed with milk replacer.

The study confirmed a reduction of diarrhea cases and respiratory diseases in calves fed with the yeast derivatives, that could be in direct link with some changes also observed in the fecal microbiota. YANG increased positive lactic acid bacteria (Bifidobacterium, Lactobacillus) and Akkermansia, a bacteria associated with the stimulation of mucin production and immune system regulation (Figure 2).

Figure 2. Fecal microbiota from YANG-fed calves versus control calves and their main potential functions.
Figure 3. Average daily gain (ADG) showing significant improvement for YANG-fed calves during the first month of supplementation

Overall, the growth performance (Figure 3) and health status of the neonates were improved, leading to a significant reduction in veterinary treatments and weaning age (-3 days).

The first months of the life of calves are critical for future productive life and nutritional management is key to limit the impact of early stresses on the digestive system and natural defenses of the animal. In addition to good management practices, using inovative yeast fractions such as YANG into milk replacer during the full pre-weaning period represents a profitable nutritional tool to help maintain calves in good health and reduce the costs of curative treatments, for optimal growth performance.

1. Abuelo A., C. Faith, A. Hanes, J. L. Brester. 2021. Impact of 2 Versus 1 Colostrum Meals on Failure of Transfer of Passive Immunity, Pre-Weaning Morbidity and Mortality, and Performance of Dairy Calves in a Large Dairy Herd Animals11(3), 782;
2. Buczinski S., D. Achard, E. Timsit. 2021. Effects of calfhood respiratory disease on health and performance of dairy cattle: A systematic review and meta-analysis. Journal of Dairy Science. 104(7):8214-8227.
3. Hulbert, L. E., & Moisá, S. J. 2016. Stress, immunity, and the management of calves. Journal of dairy science, 99(4), 3199-3216.
4. Urie N.J., E. Lombard , C.B. Shivley, C.A. Kopral, A.E. Adams, T.J. Earleywine, J.D. Olson, F.B. Garry. 2018. Preweaned heifer management on US dairy operations: Part V. Factors associated with morbidity and mortality in preweaned dairy heifer calves. Journal of Dairy Science 101(10):9229-9244.
5. Villot C., Kowalczuk-Vasilev E., Duniere L., Gauthier M., Chevaux E. 2022. Nutritional supplementation of a multi-strains yeast fraction improves health and increases beneficial gut microbiota of pre-weaned dairy calves. AH-35. Page 112 in Proc. (Vol 1) 31st World Buiatrics Congress 2022, Madrid, Spain.

About Marie-Valentine Glica
Marie-Valentine Glica is agronomist working for Lallemand Animal Nutrition since 2 years as global ruminant marketing manager. Marie-Valentine is in charge of marketing and communication for the feed additives range (trial valorization, on-farm services and training tools development,). She has previous experience in technico-marketing in healthcare for large and young ruminants.