Introduction
This translated summary article in allaboutfeed.net, compiled by Bonato and Borges (2018) and titled “How stress can affect calf health and performance,” discusses the goal of beef production, which is to have healthy animals that can achieve their maximum genetic potential at lower cost. Animal health is not only related to diseases caused by pathogens or metabolic or physical problems, but also to stress factors.
External stress is defined as “the result of exposure to a situation or environment that is abnormal for an animal.” In beef cattle production, handling and transport can be the greatest sources of stress for animals. According to Grandin (1997), animals may suffer psychological stress (confinement, transport, and novelty) or physical stress (hunger, thirst, fatigue, injury, and thermal extremes).
Adapting to a new environment
Many producers/farmers buy calves from different places/regions, even from different states. When these new calves arrive, common signs of stress are thirst, hunger, fatigue, and fear; in addition, arriving in a new environment with new social interactions with an unfamiliar group is an added stress. As a result, a series of endocrine responses directly affect metabolism, interfering with the immune system, health, growth, reproduction, animal welfare, and meat quality.
Mortality and morbidity occur, and higher medication and veterinary costs and lower production indicators are further realities. The ideal situation is to receive animals from the same farm and keep them in the same group, providing high-quality, palatable water and feed with easy access, avoiding unnecessary handling and different people, etc. The use of feed additives can help the rumen microbiota, strengthen the immune system, and reduce pathogen contamination, and can also support overall health and the animals’ response to this challenge.
Reducing stress with yeast
Yeast has been widely used in ruminant nutrition as a functional feed additive, and there is extensive literature demonstrating its benefits. RumenYeast, produced by the Brazilian company ICC, is a pure Saccharomyces cerevisiae yeast that undergoes autolysis and contains soluble fermented solids from the medium and cellular contents. This final product contains vitamins, peptides, free amino acids, and functional carbohydrates such as MOS and β-glucans. A trial was conducted to investigate the benefits of the product on the health and performance of newly arrived beef calves.
This trial was conducted on a commercial farm in the state of Texas with support from Texas A&M University (unpublished data). A total of 100 heifers with an initial body weight of 258.95±17.46 kg were divided into 2 treatments:
- Control group
- RumenYeast supplementation (9 g/head/day).
Replicating typical market conditions
The test animals were housed in pens, confined in 20 lots (6 x 6 m), 5 animals per lot. A local cattle buyer purchased the animals with the aim of having the same type and conditions as the typical market in northeastern Texas. The animals were transported to the research facility in 3 separate groups over more than 1 week. Upon arrival, the farm’s vaccination protocols (Bovine Respiratory Disease Complex, Clostridium Complex) and deworming were applied.
It is important to mention that during the trial (6 weeks) there were significant temperature and rainfall fluctuations, which could have increased stress levels in the cattle. The animals’ baseline data varied widely, ranging from cattle that had already been clearly handled (vaccinated, etc.) to cattle that had never been handled before. These cattle were fed 3 times a day with 3.17 kg/head/day of commercial concentrate and increasing Bermuda grass until feed intake reached 1% of the daily feed offered that was refused. Feed refusals were collected daily and body weight was measured weekly.
No change in voluntary feed intake
Voluntary feed intake did not differ between treatments (P>0.05). However, both treatments increased over time (Table 1). It was speculated that the high roughage content of the diet and the cattle’s ability to sort the longer roughage particles may have led to the lack of difference between treatments. Furthermore, environmental conditions (a rainy period, temperature variation, excessive mud) may have increased the caloric requirements of the animals, thereby reducing the ability to gain weight efficiently.
Table 1: Voluntary DM intake and average daily gain.
*Different means are significant when P<0.05.
| Control | RumenYeast | Probability: Treatment | Probability: Time |
Daily voluntary intake, g DM/kg BW⁰∙⁷⁵ | 140.00±0.66 | 136.96±0.66 | 0.402 | <0.01 |
Average daily gain, kg | 0.957±0.077 | 0.913±0.077 | 0.681 | <0.01 |
Medication costs, mortality, and morbidity rates did not show statistical differences (P>0.10). However, based on observations, cattle fed the diet supplemented with the product tended to respond better to veterinary treatment than the control group (P>0.10) in terms of reducing mortality and morbidity. In addition, the economic data for cattle fed RumenYeast showed a trend toward improved economic efficiency and health compared with the control group (Table 2).
Table 2: Health and cost results over the 42-day evaluation period.
¹Mortality rate of the group and number of animals lost. ² Sick: all signs of illness in the cattle were subsequently classified as chronic. ³Initial value was $742.00/hd. 4Veterinary and labor costs per animal were approximately $30.00/hd/medication and $20/hd/labor. 5Considering all costs and dividing by each head of the herd. * No statistical difference was found (P>0.10).
Health parameter | Control | RumenYeast | Gain |
Mortality rate (%)¹ | 10% (5) | 4% (2) | -60% |
Morbidity rate (sick) (%)² | 12% (6) | 6% (3) | -50% |
Costs related to death ($)³ | 3,710.00 | 1,484.00 | $2,226.00 |
Total costs related to illness and death ($)⁴ | 3,860.00 | 1,784.00 | $2,076.00 |
Total costs related to illness and death ($/head)⁵ | 85.78 | 37.17 | $48.61 |
Improved immune response
Supplementing the diet with this product appears to increase immune function due to the findings on health parameters and the reduction in mortality, morbidity, and response to treatments in these cattle. This potential improvement in immune response allows faster recovery when animals are treated, resulting in fewer retreatments. Consequently, this leads to lower production costs and labor requirements.
Furthermore, this product helps regulate and support the rumen microbiota to speed up the digestion of cellulose and hemicellulose, stabilize rumen pH under feed or heat stress conditions, and increase volatile fatty acid production. The presence of yeast cell walls rich in β-glucans and MOS will help strengthen the immune system and control pathogen contamination in the intestine.
Assoc. Prof. Bui Xuan Men, Vemedim RD Center.
References
Melina Bonato, M. and L. Borges. 2020. How stress can affect calf health and performance.
