Nutritional strategies to preserve dairy performance under heat stress should focus on supporting nutrient utilization by optimizing diet digestion, while preserving rumen function. In this context, the rumen specific yeast S. cerevisiae CNCM I-1077 — demonstrated to improve both nutrient digestion and rumen efficiency — has been shown to effectively alleviate the toll of heat stress on dairy production and improve rumination behavior.
Heat stress is now a well-established issue for both dairy and meat cattle, from North to South. It has a huge financial impact linked to both milk and meat yield reduction, but also a longer-term impact on animal health and fertility. Probiotic, or live yeast, used as rumen modifier, has proven its efficacy to help alleviate the negative effects of heat stress on dairy performance and rumen health. A recent study published in the Journal of Dairy Science (Perdomo et al., 2020) credits the positive effects of the rumen specific yeast Saccharomyces cerevisiae CNCM I-1077to its ability to benefit rumen pH, fermentation profiles and feeding behavior under such challenging conditions.
What happens during heat stress?
When the temperature humidity index increases (above 68 for dairy cows and 72 for beef cattle), respiration rate is increasing to regulate body temperature. Maintenance energy requirement is also increased. In order to limit body heat generated by digestion, the animals will reduce their feed intake, choosing cooler hours of the day to eat, which will also impact ruminating activity.
Inside the rumen, these changes in feeding behavior and rumination will impact rumen pH and microflora activity. The risk of SARA is increased, which can lead to lameness, liquid feces, lower milk production in dairy, aggressive behavior in beef and more.
All in all, through the direct impact on intake and indirect impact on rumen environment, animal performance will be affected:
• Lower feed efficiency
• Lower milk yield and milk fat to protein ratio in dairy
• Lower growth rate in fattening
• Poor feed efficiency.
HEAT STRESS IMPACTS RUMEN FUNCTION AND FEEDING BEHAVIOR
One of the many challenges of dairy production under hot and humid climates is decreased milk yields when cows are exposed to heat stress. Heat stress also represents challenges for the rumen, leading to increased risk of Sub Acute Ruminal Acidosis (SARA) (see boxed text).
Nutritional strategies to preserve dairy performance under heat stress should focus on supporting nutrient utilization by optimizing diet digestion, while preserving rumen function. In this context, the rumen specific yeast S. cerevisiae CNCM I-1077 — demonstrated to improve both nutrient digestion and rumen efficiency — has already been shown to effectively alleviate the toll of heat stress on dairy production and improve rumination behavior (Fustini et al, 2013). The recent study by Perdomo et al. (2020) further demonstrates the benefits of the live yeast on rumen fermentation profiles and feeding behavior, two parameters which are intimately linked. This is translated into better feed efficiency.
IMPROVED RUMEN EFFICIENCY AND FEEDING BEHAVIOR UNDER STRESSFUL CONDITIONS
The trial was conducted on lactating Holstein cows fed 40% corn silage, 10% alfalfa hay and concentrate, including 240g/head/day of sodium bicarbonate. The average daily temperature-humidity index (THI) during the trial was 81 and the lowest point was 75, which is still equivalent to high heat stress conditions.
The cows received either no supplement (Control), or S. cerevisiae CNCM I-1077 at the recommended dose for stressful conditions, 20X109 CFU/cow/day (LEVUCELL SC).
The live yeast supplement led to improved feeding behavior:
• Increased chewing activity (Figure 1)
• Improved rumination behavior with reduced time between rumination bouts
Overall, the longer time spent chewing and ruminating had a positive impact on rumen function and helps maintain rumen health.
Chewing and ruminating can contribute to increased saliva production, hence the higher buffer effect, as translated into improved rumen pH (+0.34 pH units on average with the live yeast) and reduced risks of SARA (Figure 2).
This is also confirmed by reduced levels of the inflammation biomarker in the blood, Amyloid A.
HIGHER FEED EFFICIENCY UNDER HEAT STRESS AND A 5:1 ROI
As a result, dairy performance was improved with the supplementation of LEVUCELL SC without impairing milk solids (no dilution effect):
• Feed efficiency is improved by 7.6% (+130g energy-corrected milk/Kg DMI) (Figure 3)
• Energy-corrected milk is improved by 2 Kg cow/day
The authors of the study explained that “improvement in feed efficiency is likely related to improved digestion of fiber, protein, and organic matter, perhaps because of direct effects of the live yeast on rumen microbial metabolism that favored a more stable ruminal environment. The changes in feeding behavior with reduced eating rate and increased chewing time per unit of DM and NDF consumed should also favor optimised digestion with reduced acidosis.”
In conclusion, this study by University of Florida confirms previous trials showing that under challenging conditions the rumen specific live yeast improves rumen conditions and feeding behaviour (Bach et al., 2007; DeVries and Chevaux, 2014). Here, the scientists went further than looking at performance only and looked at blood biomarkers and ruminal fermentation profiles. These show that S. cerevisiae CNCM I-1077 increases feed digestibility through higher fiber degradation (total tract NDF), which results in higher nutrients and energy extraction from the diet. Benefits for the producers are two-fold: reduced SARA risk and higher ROI due to the improved milk yield. We calculated a 5:1 ROI and recommend using this stress-specific dosage during challenging times.”
Bach A., C. Iglesias, M. Devant and N. Ràfols. 2007. Daily rumen pH pattern of loose-housed dairy cattle as affected by feeding pattern and live yeast supplementation. J. Anim. Feed Sci. Technol. 136: 146-153
DeVries T. J. and Chevaux E.. 2014. Modification of the feeding behavior of dairy cows through live yeast supplementation. J. Dairy Sci. 97: 6499–6510
Fustini M., A. Palmonari, H. Durand, A. Formigoni and E. Grilli. 2013. Effect of Saccharomyces cerevisiae CNCM I-1077 (LEVUCELL SC) on rumen pH and milk production during heat stress. J. Anim. Sci. 91 (S2)/J. Dairy Sci. 96 (S1)
Perdomo, M.C. et al. 2020. Effects of feeding live yeast at 2 dosages on performance and feeding behavior of dairy cows under heat stress. J. Dairy Sci., Vol. 103 (1) 325 – 339
About Aurélien Piron
Aurelien Piron is working for Lallemand Animal Nutrition since 12 years as ruminant technical manager. Aurelien is in charge of technical support for ruminants feed additives range (deployment of on-farm services, training for field salespeople, joined RandD program and field experiences with customers). He is also involved in several marketing, technical and RandD projects within Lallemand.