'The difference between light and half light is important'
Beef & Sheep 7

Short Days Less Milk

The clocks are back and winter is coming even if the weather hasn’t realised yet! No one likes the end of the summer period, but the worst bit to me is the creep into short days – dark in the morning and evening with sometimes only gloom in between.

Cows don’t like short days either. I am reminded of this when I look at a broad range of production figures every year at this time and see the same seasonal slump. When cows (and any mammals including us) are exposed to longer dark periods there is a rise in melatonin which is an important hormonal messenger. How all the hormone interactions work is complicated and poorly understood, but the important bit for us is ultimately they lead to a fall in IGF (a growth hormone).  IGF is an important driver of growth and production. .

  • Studies show an average of 2.5kg increase in milk production from cows in long days versus short days. The average production in these trials was in the high twenties so you can see how significant the effect is – in excess of 10%. Day-length manipulation stands along with 3 times a day milking and bST (artificial growth hormone injection banned in EU) in significance when it comes to stimulation of milk production.
  • Fertility – Heifers get to puberty quicker in longer days. Cows also return to oestrous after calving quicker in long days than in the winter.
  • Youngstock grow quicker and more efficiently in long days. There is also evidence of post puberty heifers laying down fat more in the short winter days than in long days – think about this and perhaps the effect of heifers at grass may not be all due to the grass!

Very significant benefits then – even better is that these studies showed animals operating at increased efficiency of food utilisation/conversion so the extra production was at lower extra feed cost.

What is a long day?

Cattle need to be in the light 15hours after their perceived dawn to register a long day. This is where the recommendations for a 16-18 hour lighting period come from. The light needs to be 160l-200lux. This is bright, it is more like an office building than the average cow shed. It is vital to remember that a dark period is required to keep a daily rhythm – without this the lighting benefit does not work at all.

Maybe Brighter times are coming…

The return on investment from proper lighting will be many times over. In a world of many claims for more milk and healthier cows light stands out as an excellent investment. Yet I have measured light in many cow buildings and very few are actually long day stimulatory.  This research is nothing new, so why is it not standard? Often leaving inadequate lights on 24hour is a pointless alternative taken to doing it properly.

The last 2 years have not been the time to talk about investing in dairy farm infrastructure, but the future is looking better, and hopefully there will soon be a time when investment is discussed. When that time comes put good, stimulatory lighting on the wish list.