Grazing autumn-calved cows comes with a host of different challenges to those associated with spring-calving herds and demands a different approach. Hannah Noble reports.
Speaking at an AHDB meeting in Denbigh, Andre van Barneveld, Graise Consultancy, said in autumn calving systems there needed to be a balance between looking after the nutritional requirements of the dairy cow and trying to maximise use of pasture while minimising the compromises.
Mr van Barneveld said in grazing systems it was important to start thinking about profit rather than output.
He said: “If one herd is producing 1,000kg per cow more than another farm we automatically presume they are doing a better job or they are achieving more but that is not necessarily always the case.
“8,500kg of production with a 10p/kg margin provides £850 profit per cow, however 7,500kg of milk at 12p/kg margin results in £900 profit per cow.”
He said it took skill and knowledge to get value out of grazed grass and there was no such thing as a simple grazing system.
He added, if farmers wanted to achieve profitability from grass they needed to focus on the grass first and foremost. Farmers needed to then consider what could be profitably added to the diet alongside grass to complement it, increase energy intakes and provide a return on investment.
“Generally in all-year-round calving or autumn calving systems, which are usually output-driven systems, people look at their diet with the concentrate as the main ingredient and grass is often an afterthought.”
Mr van Barneveld said pasture management revolved around residuals, grazing the grass plant down to 3-4cm, 1,500kg dry matter per hectare so that there was always enough light getting to the base of the plant.
He said two things that impacted on achieving the desired residuals were pre-grazing cover and appetite.
“The moment you start giving cows forage or high concentrate levels they will not clean up the grazing paddocks and you will not achieve the residuals you want.
“Substitution is the amount of pasture or silage, when housed, that a cow will not consume if it is fed an extra kilo of concentrates.”
Mr van Barneveld said understanding substitution was the key to reaching the desired residuals, and therefore seeing profit from grazed grass.
He said 1kg of concentrate usually added at least 12MJ energy to the cow’s intake and it took 5.3-5.5MJ to produce 1-litre of milk. So for every 1kg concentrate fed he said there should be at least 2kg of milk produced. However he added it did not work like that because of substitution.
“If you give a child a small piece of cake at a party they will still come home and eat their vegetables, but if you give them a big piece of cake they will not want to eat their vegetables, cows are the same.”
“With the first kilo of concentrate being fed it is a 10 per cent substitution rate so a cow will only drop out 0.1kg of grass to consume the first kilo.
“However, with the second kilo it will go up to about 50 per cent, to about a 0.5 kg drop in pasture intake, the third kilo will generally be over 80 per cent substitution rate.
Mr van Barneveld said despite this, in a pasture deficit situation, substitution was the greatest ally.
“If you are short of grass you can now feed so the demand for pasture will decrease, but in a pasture surplus substitution is your greatest threat because demand is sitting much lower than the amount of grass being grown.”
Preparing the grazing platform going into winter and understanding the principle of when and where to turn cows out in the spring was one of the most important things to get right said Mr van Barneveld.
“In an autumn calving system, ideally I would suggest you have a quick last rotation in October, cover the whole farm, grazing down to a flat wedge. With grass at the top of the wedge at 2,800kg dry matter (DM) per hectare in the spring and 2,400kg DM/ha cover at the bottom.
“If you graze anything after the November 20, you are just pulling grass out of the spring.
He said farmers did not want covers too low going into the winter, but equally there was a risk carrying high covers into the winter which could ‘melt away’ in some circumstances.
He said when turning cows out in the spring it was critical the conditions were right and they were grazing the correct covers.
“I would look at the weather forecast, if you are going to have a couple of fine days and then solid rain for a week, I would hold-off, I would rather turn out to be able to keep them out.”
Mr van Barneveld said the ideal situation in the spring was having no pasture with cover over 3,000kg DM/ha. The temptation was to turn out on to the highest covers, however he said in longer swards light was not able to get to the bottom of the plant and leaves would have turned yellow. He said these longer swards required high grazing pressure to graze them down properly and did not recover well afterwards.
He added, in periods of low soil temperature, grazing long covers down to the ground and trampling them did not work well and that ryegrass did not start to become active until soil temperature reached six degrees, and clover at eight degrees.
“You must identify paddocks with even cover, sitting around 2,300-2,400kg DM/ha. You are looking for grass that still has light to the bottom, and is green and leafy tight to the bottom.
When you turn the cows out you have to give them an area that you know they are going to graze down to the right residual, you are aiming to graze it down to 1,500kg DM/ha or 3-4cm evenly.”
He said: “You will never have enough grass on hand to feed an autumn calving herd solely on grass from early February