The Power of Calving Date
Getting tight for grass going into the second round creates a few more problems than we give it credit for. A step in the production curve is easy to see but the effect on reproduction is subtle no matter what farm system you run. A cheap and easy way to help this problem is a later calving date. But only a discussion on stocking rate causes more apoplexy in farmers.
With different farm systems, different scenarios do develop with grass deficiency. System one and two farms manifest as a simple feed deficiency – no surprises there. The herd will be prone to persistent negative energy balance after calving, be slow to cycle, have an increased number of short returns and more phantom pregnancies. High rates of urea to boost low covers drives up protein content at times to very high levels. In association with an energy deficiency, these high pasture protein levels cause additional problems for cows at mating.
At higher farm system inputs, supplementary feed aims to bridge the feed gap before balance date. But grass deficiency still creates problems with repro, particularly in high producing cows. Notwithstanding a raft of issues come into play with system four and five farms. These include quantity and quality of supplementary feed, how you feed it, how well you can mix it, and changes in mineral profile. These are all potential ways for it to go wrong. Increase these inputs further in a tighter spring and before you know it, in contrast to all-grass systems, a protein deficiency develops. And in more extreme situations the effects are devastating.
Maize silage is the most common bulk feed used, with grass silage, PKE or combinations of the three. Maize silage is very low in protein. Grass silage is highly variable and often much lower than expected. There is a common misconception that PKE is a protein source – it’s not. At best there is just enough protein in its own right. At worst PKE protein is largely indigestible. But the reality remains, adding PKE to maize silage does little to improve the protein situation.
Protein rich feeds such as soya meal, DDG, canola and cottonseed are expensive at around $1.50 a kg of protein. However, leafy spring grass is an excellent protein source and it costs about 60 cents a kg of protein. Given the expense of protein supplements, there is a tendency to hang tight and box through the lack of grass – because it will grow soon won’t it? However, when low protein hits the production curve and impacts on reproductive performance, being short on grass is a very expensive problem and an expensive problem to fix.
Clearly, a cheap solution is to put the calving date back a bit and better match grass supply with demand. Even 10 days can make a considerable difference. Lost lactation days will be more than made up by promoting a compact calving. And, milking later into the season becomes an option with a lot of flexibility to milk on or dry off depending what the season offers. Worth thinking about eh?