Beating the heat with phytonutrients
Because both the rumen and lower gut need to work optimally in order maximise dairy cow performance, nutritional strategies to beat heat stress must target both organs. Recent studies evaluating various additives showed that a specific combination of phytomolecules consisting of capsicum oleoresin, cinnamaldehyde and eugenol (CCE*), does just that.
1. Supplementation with capsicum oleoresin improves feeding behaviour by increasing the frequency of feeding, without increasing total feed intake, resulting in a more consistently filled rumen. This stabilises heat production by the rumen and also reduces the occurrence of rumen lesions.
2. The combination of cinnamaldehyde and eugenol improves the breakdown of ingested feedstuffs, resulting in an enhanced volatile fatty acids profile and optimal protein metabolism.Moreover, this specific blend of phytonutrients acts in the lower gut to decrease inflammation and associated local generation of heat and thereby maintaining optimal gut structure and nutrient absorption.
Taken together, the combined actions of the molecules in CCE exert effects on both the rumen and the lower gut to prevent any additional heat from being generated by dairy cows, while optimising digestion and nutrient absorption.
2 field trials conducted under conditions of heat stress in Israel confirm these findings. Both trials were carried out in similar conditions to test the effect of CCE in the form of a feed additive, in alleviating heat stress in high producing Holstein dairy cows, from June to September. The natural environmental conditions created heat stress as measured by the temperature and humidity index (THI). During the trials, the animals were systematically divided into 2 comparable groups and were fed a high concentrate diet, in which the CCE was blended with ground corn meal and top-dressed. The effects of heat stress in the control group were observable. For example, in trial 1, environmental conditions reduced milk production from 43.7 kg/d (low heat stress) to 39.4 kg/d (high heat stress). Feed supplemented with CCE caused significant improvements in milk production and feed efficiency under conditions of heat stress. Neither milk quality nor body condition score was negatively affected by the increase in milk production. Interestingly, somatic cell count reductions were also observed. Table 2 presents an overview, using results pooled from both trials with a total of 200 cows. Supplementation with CCE progressively increased milk production over time, resulting in an improved final milk persistency (Figure 2).
Figure 2 - Progression of milk production during the trial.
Fresh opportunities for heat-stressed cows
Recent findings on the performance of dairy cows during heat stress have shown that the reduction in feed intake plays a much smaller role than previously thought. Lower gut health is now known to be critical, representing new opportunities for refined animal management during periods of heat stress. Although feeding technologies currently available are limited, phytonutrients represent a promising natural solution to alleviate heat stress for producers.