Doc’s Blog

Laboratory Testing for Trace Minerals

    An article in a recent issue of a prominent dairy magazine dealt with the problems of trace mineral deficiency diagnosis. One of the problems associated with testing for trace minerals is that some are found in the ‘transport pool’ in the blood and other are in a ‘storage pool” in the liver.   

    Unfortunately, serum concentration of most trace minerals can vary for many reasons, including; pregnancy, lactation, inflammation, weather, etc, etc   Bioavailability can also be affected by the presence of mineral antagonists.

    The author pointed out there are new testing techniques available that are sensitive and accurate. Samples of blood, serum, liver tissue, milk and urine can be tested, but databases of ‘normal’ parameters are lacking.

   With so many variables involved, I am skeptical of blood testing for mineral content.  It may be extremely accurate, but is, at best, only a ‘snapshot’ of what is happening at that particular instant in time.   Hair analysis would provide a broad panorama of mineral metabolism.

    As I read the article, it seemed that laboratory diagnosis of trace mineral imbalances was a daunting task and not all that accurate.  Applying the results of individual or small group testing to large groups negates any allowance for individual variation of mineral needs.  Force feeding a computer-generated mineral ration has a very good chance of adding to the problems rather than reducing them.

    There is, of course, a better way.  Take advantage of the animal’s innate nutritional wisdom, and provide a broad array of individual minerals for their individual evaluation.  It’s the natural way and it works. 

Selective Dry-Cow Therapy

   Many folks in the dairy industry are beginning to question the almost universal practice of dry-cow treating all their cows with intra-mammary antibiotics.  This is done in the hope that it will cure existing cases of subclinical mastitis and to prevent new cases from occurring at calving. 


    Probably the main reason for this change in thinking is the growing evidence that antibiotics used in livestock can result in antibiotic resistant strains of bacteria that are difficult to treat in humans.

    It doesn’t take a rocket scientist to figure out that one way to reduce antibiotic exposure is to only treat the animals that need treatment. Duh!    Research has indicated that as many as 70% to 80% of quarters are not infected at dry-off, and thus may not require dry cow therapy.

   The key to selective dry cow therapy is to identify the the cows and quarters that need treatment.  There are several options recommended to accomplish this, including: The California Mastitis Test (CMT). somatic cell count (SCC) tests, veterinary lab culturing of milk samples, and using on the farm culturing labs. The sensitivity rate of these procedures varies from 50% to (90% accuracy. 

   All of this costs time and money.  The University of Minnesota has estimated that the payback for selective dry-cow therapy is $2.62 per cow.  

    For dairymen who are unable or unwilling to do this, there is a tried and true, low tech way to identify the infected cows.  When it’s dry-off time quit milking the cow. It takes five or six days for the cow’s hormonal system to switch from milk production to no milk production.  After this five or six days, sanitize the udder and milk out some secretion.  It should look like regular milk.   Any abnormal signs in this secretion - watery, clotting, bloody, snotty, off color, bad odor - is an indication of infection and that quarter should be treated.  Whether the milk if normal or not, a good practice is to milk out all quarters at this time to aid in the involution of udder tissue. 

    Conventional dairymen will probably treat affected quarters with antibiotics.  It is also recommended to infuse teat sealants into all quarters. That procedure can introduce infection into the unprotected mammary gland. 

   Holistic or organic dairymen have more choices;  colostrum-whey products, herbs, homeopathy and others.  If using these products. it is best to check the milk every four or five days and treat again if indicated.  This methods supports and enhances immune response and works with the innate physiology of the animal.  These treatments generally work well in animals whose immune system is not already greatly compromised by stress, malnutrition, or exposure to toxic ag chemical in their environment.

Feedstuffs Analysis

The Feedstuffs magazine I received  recently contained the Feedstuffs Ingredient Analysis Table: 2017 Edition.  This summary is published every year and contains basic nutritional data on most commonly available feedstuffs. I knew I had the 1977 Edition in my files and surmised that a comparison of some of the data would be interesting.   Little did I realize that it would raise more questions than it answers.

Here is a comparison chart of three common feedstuffs.  

I anticipating that there would be some changes in nutritive value  but found only four is this admittedly small sample.

  • There was a 10 percent increase in phosphorus levels in corn.
  • There was a 16 percent decline in crude protein in corn.
  • There was a 19 percent decline in crude protein in wheat.
  • There was a 27  percent decline in ash or mineral content in corn.

The most astounding thing to me was the absence of change.  In 40 years, the analysis of dehydrated alfalfa meal was exactly the same - ditto for all the rest of the data in the chart. 

Specifically, I am curious to know how crude protein in corn and wheat  can decline 16 to 19 percent respectively and  the ruminant digestible protein not vary at all?.   

I know there could be some difference because of changes in analysis techniques and I know they are averages - but almost everything being identical after 40 years makes me suspicious of the validity of this data.  If at all possible, we should rely on individual testing of any feedstuffs included in out livestock rations.