Since the previous decade, the ruminant market has been quickly evolving, offering both possibilities and problems for those involved in animal production. Heat stress in ruminants, in particular, is a significant concern in our profession due to its deleterious influence on performance.
Heat stress has serious repercussions.
According to Kemin study, the following negative impacts of heat stress have been demonstrated:
- This has a negative influence on the animal’s usual physiological behaviour.
- Reduced dry matter intake, which has a direct influence on dairy cow production.
- Dry matter intake should be reduced by 20 to 25%.
- Milk yield declines by 40 to 45%.
- Reduced fibre digestive efficiency has an effect on ruminal acidosis.
- Oxidative stress alters endocrine function and nutrition absorption.
Reduced reproductive efficiency.
Kemin argues that dietary solutions that improve the negative protein and energy balance associated with heat stress are crucial in helping cows to retain milk output and health. To reduce the impacts of heat stress, we must first enhance our general health and then implement a healthy dietary approach.
Heat stress mitigation strategies
There are two critical paths to reducing the consequences of heat stress. It is critical to ensure:
– Improved overall health
– Appropriate nutritional strategy
Both of these channels are critical not just during heat stress, but also throughout the animal’s life. Here’s an overview of both ways, along with some solutions:
1) Improved overall health
Improving dry matter intake to preserve and boost production under heat stress may be accomplished via two strategies: choline supplementation and dietary cation-anion balance (DCAB):
Choline. Choline nutrition has lately gained a lot of interest owing to its significance in boosting liver function. Aside from increased production, Choline’s significance in enhancing dry matter intake, immunity, and health makes a compelling case for improved bioavailable Choline supplies. We have demonstrated that choline changes the plasma NEFA concentration, enhancing hepatic fat export. This reduces hepatic fat content and, as a consequence, improves liver function, resulting in appropriate dry matter intake.
Arshad et al. (2020) did a meta-analysis of the effects of rumen protected choline supplementation on the performance and health of parous dairy cows. They discovered that eating 200 g dry matter prepartum and 500 g postpartum resulted in better body weight and body condition score.
Dietary cation-anion balance (DCAB). In animals, dietary cation-anion balancing (DCAB) increases dry matter intake. Rumination activity diminishes when plasma calcium levels fall during hypocalcemia. Rumination is distinguished by a complicated sequence of muscular contractions that transport a bolus of ingesta to the mouth for further mastication before swallowing it again. In pre-calving cows exposed to heat stress, DCAB may overcome impaired rumination induced by hypocalcemia.
Santos et al. (2019) just published a meta-analysis based on 42 studies, 134 treatments, and 1803 cows. The statistical models’ resultant equations suggested that decreasing the Dietary Cation-Anion Difference (DCAD) from +200 to 100 mEq/kg would raise blood total calcium on the day of calving from 1.86 to 2.04 0.05 mM, DMI postpartum 1.0 kg/d, and milk output 1.7 kg/d in parous cows.
2) Appropriate Nutritional Strategy: Diets include rumen-protected amino acids (AA), methionine, and lysine.
Effective nutritional management and adequate ration formulation are critical for improving health and productivity, and thereby alleviating the harmful impacts of heat stress in dairy cows. Heat stress entirely alters rumen and small intestine functions, impacting digestibility and feed efficiency, as well as metabolic responses to lower intake and a decrease in endogenous heat generated to sustain gluconeogenesis.
As a result, precision feeding with Amino Acid nutrition is critical to mitigating the effects of heat stress on animals. Formulating low-rumen degradable protein diets, as well as meeting methionine (Met) and lysine (Lys) requirements, lowers circulating insulin levels and improves both protein efficiency and the metabolic status of heat-stressed cows due to better AA utilisation.
The only viable approach to accomplish the above is to improve protein quality supply, increase the levels of the first two limiting AA, Met, and Lys in diets, and maintain an acceptable energy level.
One thing is certain: regardless of production level, temperature-humidity index, or diet components, we cannot meet Met and Lys demands without employing both rumen-protected Met and Lys.
Amino acids have been shown to provide the following advantages. They:
Increase the production and utilisation of glucose.
Reduce the negative energy balance (together with the negative protein balance) caused by heat stress.
Reduce oxidative stress while preserving immunological function.
Increase antioxidant capacity while preserving immunological function.
Assist us in developing low heat increment diets.
Increase your consumption of dry matter and energy-corrected milk under heat stress.
Restore the intestinal barrier when it has been damaged.
Conclusion
Two new meta-analyses of rumen-protected Choline and DCAB supplementation reveal that Choline and DCAB considerably enhance dry matter intake, which is crucial in improving farm profitability.
In addition, combining AA with other ingredients is one of the most cost-effective strategies to enhance health and performance at all times, particularly under heat stress.
