Dairies Run on Calcium

In recent years I’ve become more concerned with just what are we doing in our dairy farming. Certainly we’ve made advances in milk production per cow, dry matter harvested per hectare, but I see from time to time some disturbing signs while inspecting herds on my client’s farms. Soil issues, plant pest problems, both of which have driven me to reading appropriate material on these and other problems in cow health and performance, especially fertility.

With so many dramatic changes occurring in technology, machinery, computer recording, plant breeding, I do wonder about farming practices of my youth that I rarely see these days. Of course, the one I’m think most about is “ag lime’. In fact, spreading lime on paddocks has been around longer than anyone reading this article.

I see an inversion here – no lime but more nitrogen. Many crops and pastures are limited in yield due to acid soils. This inversion has multiplied the acid soil issue, and further compounded it by depleted sulphur from extended urea use and no supplementary sulphur. I am certainly not an agronomist, nor a soil microbiologist, but it does not take their level of understanding to realise we have soil health/productivity problems. I suspect soil microbiology does not do its vital task of feeding plants when soil pH is compromised.

I am advised, as soil pH drops below 6, the availability of some nutrients declines, especially phosphorous, but also magnesium to a lesser extent. Other nutrients can elevate enough in availability to become toxic to some crops/plants. We have seen decolourisation in sorghum leaves identified as nutrient deficiencies when fertiliser requirements had been met.

It requires 200 kgs of lime to counter 50 kgs of nitrogen in terms of soil pH. Ammonium sulphate is more acidifying than other nitrogen sources, and can require 350 kgs of lime to counter50 kgs of nitrogen from ammonium sulphate.

Turnip crops have grown in popularity in recent years, and I can’t encourage this crop enough. The Income Over Feed Cost we see when turnip is a ration ingredient, especially at a time when milk price is rising rapidly, makes them a highly beneficial exercise. However, turnip is a very capable scavenger of calcium from soils. Although in our turnip program we recommend 2.5 tonne of lime per hectare (gypsum is even better to replenish soil sulphur reserves), it is not regularly done. Turnip has multifaceted benefits in dairy cow rations.

Obviously it is a high energy source with bulbs up to 40% sugar. It is highly digestible, around 76% in 30 hrs (rate of passage of feed through the digestive tract does influence dry matter intake), and bulbs are around 17% crude protein and leaves 25% crude protein. When we are deficient in fresh pasture, turnips can supply significant protein to an otherwise, frequently, protein deficient diet.
However, this is not the last word on turnip. Our dairy cows have a high need for dietary calcium. Turnips, due to their calcium scavenging capacity, are an excellent source of calcium. We have tested turnip leaf at 3.5% calcium and bulbs at 1+% calcium. To put this in perspective, ryegrass averages around 0.3% calcium. We cannot feed anywhere near our cows calcium requirement via limestone in grain mixes.

Calcium is critical to virtually every metabolic function within a cow, especially immune function; let alone what she ships out on the milk tanker daily. We have learnt from experience, an enhanced calcium intake in dry and springer cows has profound influence on fertility. When the dry/springer cow’s calcium requirement has been met, we have recorded, on multiple occasions, rises from 30% conception on first insemination to 65% conception on first insemination. This is a staggering increase, and following on from January’s article on pregnancy rates, and their equal influence on farm profit to feed availability, calcium nutrition cannot be ignored.

Restoring forage, or forage species high in calcium is a must for cow health and performance, but we will gain in soil health and performance also. Turnips are a seasonal opportunity for dietary calcium intake, restoration of clover in pasture swards will benefit ryegrass production as well as increasing calcium content in grazed pasture. We have severely degraded our soils over the last forty years, especially with excessive use of urea, and to my observation, diminishing benefit, partially through depleted sulphur reserves, but also reducing soil pH.

To compound the soil acidification problem, we have also compacted soils further reducing their productive capacity. A return to a balance of clover and ryegrass will slowly improve ryegrass root penetration to access moisture and nutrient currently out of reach. Clover is a deep rooted plant and will penetrate ‘hard pans’ we regularly identify in paddocks with use of a penetrometer.

Deep ripping may be necessary in particularly compacted soils, but as a crop specialist friend in the USA says, “ripping a paddock of bricks only ends up with a paddock of broken bricks”. More is needed, and cropping programs have very significant impacts on soil productivity. We recommend a two year cropping program as part of a seven year pasture renovation program. Multiple crops throughout the seasonal variations enhance soil productivity. Different crops (summer crops and winter crops) remove and deposit substances that have mutually synergetic benefits, but all contributing to pasture growth when sown back to perennials.

The dramatic increased use of insecticides has a correlation to compromised plant health. Healthy plants contain insect repellents in their leaves. Further, insecticides cause a rise in soluble sugars and nitrogen in plants, the food of insects, so we only multiply our problem.