ArticleVolume Number October 21, 2019

Is rumination linked to the fat test?

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Article written in collaboration with Julie Baillargeon, Agr.

Looking at the fat test results, Régis is a little discouraged; the fat result in the tank is dropping again this month. In order to slow down ruminal transit, he adds straw to the ration. He also hopes to  measure an increase in rumination time using sensors on his cows' necks. Between April and mid-June, the amount increased from 300 g to 1.4 kg but the fat test does not move and the rumination time is stable (graph 1).

Graph 1. Variation in fat test and rumination during the period February to July 2018 for Régis farm (in french only for the moment).

After several analyses, it seems that a protein ingredient, with a much higher than expected oil content, is involved. The protein source is changed and the fat level tested begins to increase immediately. And the rumination doesn't change.

So is rumination time related to fat production? Let's see what the research says on the subject.

Feeding parameters that influence rumination

Rumination is an essential process for a ruminant in order to digest feed. One would assume that there might be a link between feeding parameters and rumination. In a review of 60 scientific articles on rumination, Karen Beauchemin noted that the following feeding factors have an impact on rumination time (Table 1)

Table 1. Correlation between feeding parameters and rumination

Correlation between feeding parameters and rumination

Although several parameters have an influence on rumination, it must be recognized that these parameters are all interrelated and that none of them have a major influence on rumination. The 8 mm portion of a forage sieve is often related to rumen health and is the factor with the most impact on rumination.

Little connection to the fat test

Just like Régis, we frequently link the fat test to rumination;  if rumination goes down, we expect to see a decrease in the fat test and if it is normal, then the fat test should be too. Danielle Andreen, a student at Pennstate University, validated these statements  in a research project.

More than 1,800 cows in five commercial herds were the subject of this study. Rumination data was collected seven days prior to test day. All milk samples were tested for fat. Three farms had ear medallions to measure rumination and the other two used the collar. Rumination detection systems had been in place for more than six months on all farms. Graph 2 illustrates the relationship between the fat test and rumination. Each point is the result of a cow.

Graph 2. Relation of rumination measured with two sensor systems according to the fat test.

The two sensor systems show a common result: there is no link between the fat test and rumination.  When the fat test is low, some cows have low rumination results while others show higher scores. Similarly, when rumination is low, some cows have low fat tests while others show higher fat results.

Often, the decrease in the fat test is caused by a large amount of oil in the ration. Because of this, the fatty acids are not completely hydrogenated and will lower the fat test. Thus, a ration that contains a little more unsaturated fats (oils) will  have very little influence on cow rumination. This explains the situation encountered by Régis at the beginning of this article.

The fact that there is very little link between rumination and fat testing may cause some disappointment. However, rumination is an important process in the feeding of dairy cows!

But as we have seen, several parameters influence rumination and there are probably many variations associated with the cow. Also, there is still a lot of research to be done to better define the link between feeding and rumination. In the meantime, rumination probably remains one of the most reliable piece of data for detecting health issues.

Reference: Can rumination data improve nutritional management? Danielle Andreen, Kevin Harvatine, PennState University, January 2018