With a constant focus on managing feed costs, we spend most of the time thinking about ingredients that would qualify as expensive. Maybe this is in dollars per ton, or even better, cents per cow per day. What about the other extreme? What ingredient in your ration has the lowest cost per ton and is the lowest cost per cow?
Before telling you the answer, let’s make note that this ingredient doesn’t really make milk. This key nutrient is notable in milk and is used by the body as well. But, unlike corn, soybean meal, or wheat straw, it doesn’t support milk production per se.
What is this bargain ingredient? Calcium carbonate (CaCO3), which is usually sourced from limestone.
Vitamin and mineral premixes
When we think of the feed ingredients that make up the building blocks of milk, we are usually talking about grains, by-products, and forages. We also know there are numerous lower inclusion ingredients that are often combined in what might be called the “mineral.” Maybe you call it a premix, a mineral premix, or in some geographies, a supplement. In any case, this ingredient is where the more complicated, often costly, and usually highly detailed ingredients are supplying grams or even milligrams of micro ingredients, when they are either required by the cow or added to allow a cow to perform at a higher level. Included often here are the vitamins and various feed additive technologies. Many of these ingredients are included at a rate less than 1/100th of a pound.
Good for humans and cows
On the higher end of the components of this “mineral” ingredient are, in fact, the minerals. These ingredients supply sodium, magnesium, potassium, or sulfur, and are usually mined minerals with a feed rate per cow of 0.05 pounds, up to perhaps 0.15 pounds per cow. But calcium carbonate usually dwarfs all others in feed rate.
In almost all commercially available and custom-built dairy mineral products, limestone is the largest part of the mix. In fact, in most feed or mineral mill environments, it is the filler to adjust as needed to target a consistent feed rate at the farm. Thank goodness it is also the cheapest ingredient in the formula.
Everyone knows that calcium is abundant in milk. I expect dietitians and milk drinkers would count calcium intake as a reason for the consumption of dairy products. In the prevention of osteoporosis and in support of general health, high calcium intake is encouraged. So, it isn’t any surprise that the amount of calcium in a cow’s diet is of human interest.
What’s the right amount?
So, why all the fuss over this low-cost ingredient? The reason is that calcium fed in excess amounts does not support milk production. It doesn’t hurt the cow, but are excess amounts taking up space that could be replaced with something more beneficial to achieve additional milk? This is where I think we (me included) may be missing an opportunity.
I know we are way into the minutia here, but stay with me for a minute. I will skip to the end to give a peek at why it matters. Using a leading dynamic nutrition model, I demonstrated an additional 0.90 pounds of milk production by changing the calcium approach just a little. By dropping from industry calcium norms to actual requirements, you can model additional milk yield. That is an additional $65,000 of milk revenue per 1,000 milking cows per year — not bad for doing nothing difficult.
Let’s look at some industry information. First, I did an informal survey of sorts among some of my most respected dairy nutrition colleagues. From the query, I found that there was a range of 0.70% to 1% of calcium. I also reached out to two respected national feed and forage laboratories to see if they would share wet chemistry analysis results from total mixed ration samples marked as lactation rations.
First, Cumberland Valley Analytical Services (CVAS) supplied the following results: From 141 recent samples, the average calcium level was 0.97%, with a standard deviation of 0.24. This indicates that approximately one-third of these samples was between 1.0% and 1.2%. My suspicion of frequent overfeeding of calcium was growing.
Rock River Laboratory shared the following information: On several hundred samples, the average was a little lower, coming in at 0.89% of calcium, with a standard deviation of 0.24. Thus, many samples were sent to the lab with calcium levels at or in excess of 1%.
You must be asking what is the actual requirement of calcium for a lactating dairy cow? The go-to source for this question is the nutrient requirement table included in the National Academies of Sciences, Engineering, and Medicine’s (NASEM) Nutrient Requirements of Dairy Cattle. Nutrient requirements are divided into days in milk (DIM) ranges and by parity. For starters, the highest percentage of calcium required across various combinations of DIM, milk production, components, and predicted intake is much lower than anything seen from the labs at 0.69%. This is surprising considering our discussion above was closer to 1%.
The science behind
The next step in my preparation for this article was to do some ration modeling. I have already told you the result, but I will describe the process. I took a corn silage-based ration that I had recently evaluated for another project. The ration included a low feed rate of alfalfa haylage and small grain silage. This diet had a calcium level of 0.91%, which is similar to the averages from both labs. To achieve this level, there was a whopping 0.83 pounds of limestone. I reduced limestone and replaced it with corn gluten feed and haylage. I was able to shift soybean meal (SBM) to gluten, to keep the protein from increasing. The result was an increase of 0.90 pounds of metabolizable energy (ME) milk support, with adequate metabolizable protein (MP) supply. The higher cost to feed less of the cheapest ingredient in the ration was 1.1 cents per cow — a nice economic return.
Next, I wanted to see if the results were the same for a ration with more alfalfa. Although alfalfa is much higher in calcium than corn silage, it also has a slightly lower calcium availability. The results were nearly the same.
A ration including 12.5 pounds of DM each of corn silage and alfalfa haylage, plus a touch of triticale silage, had a higher calcium level of 1.1%, similar to the higher end of the lab samples. Because alfalfa contributes much more calcium than corn silage, the limestone requirement was less at 0.77 pounds per cow. Due to the lower availability of calcium in the alfalfa, I was only able to drop the calcium level to 0.76% of the diet using only 0.25 pounds of limestone. The drop in limestone was then appropriated to gluten, with a small decrease in soybean meal. The increase in milk support was equivalent to the high corn silage ration at 0.90 pounds additional metabolizable energy milk support with adequate metabolizable protein. The improved feed cost in this example was 4.5 cents — still leaving a nice margin.
Finding a happy medium
I suppose the reason we tend to include more calcium is that, as we have said, it is cheap. But it is usually included in a mineral-type product purchased from a feed or mineral company with the highest cost structure of your entire ration. So, are we doing the best thing? High-producing cows are often limited in intake and every part of every pound matters.
Lab analysis of ingredients and rations can give us more confidence. On this note, I must say that in many, if not most cases, the calcium results in my ration lab analyses are higher than my formulated values.
Perhaps going all the way down to the NASEM recommendations of 0.64% is not going to be very popular. What if we drop down to a comfortable 0.75%? This can be a nice step that could support an additional 0.50-pound of ME milk.
One last comment on NASEM’s requirements — the requirements on a percentage basis are set from milk production levels and expected intake. So, if your feed conversion is in the 1.6:1 to 1.7:1 range, your grams of calcium supply for the stated milk will be even higher.
The leading nutrition models will show the total calcium, absorption coefficient, and absorbed calcium supply. My guess is that in many, if not most cases, this supply could be 150% of the requirement. This should be the last checkpoint. Perhaps dropping that to 125% of the requirement might be a start. Consider grams of calcium supplied over various intake situations. Be sure to use the newest NASEM absorption coefficients.
Calcium nutrition is not as exciting as things such as fatty acid balancing, or fine-tuning branched-chain amino acids to maximize mechanistic target of rapamycin (mTOR) signaling, but it is an easy way to support just a touch more milk. Admittedly, it is a small thing. Just like in the rest of life though, it’s about doing several little things better to create long-term success.
