Cows, calves and veterinary

January silage

In the past, I've been very dubious about farmers deciding to cut silage in the New Year. Usually I hear of the decision from neighbours who insist they have plenty of grass, when I know for certain that my own farm is heading into careful rationing after difficult weather has impacted grass growth, and ahead of expected drought.

Growth this year has been very on/off. We've had alternate months rain/dry resulting in bursts of growth followed by a slow-down. The cows have been fully fed through-out, but the amount of supplement cut has suffered as the reasonably large second cut I'd hoped to get vanished with the drought, leaving only enough surplus to grab the two paddocks of hay I'd dropped out of the grazing rotation before the grass all but stopped growing - I was measuring growth of about 30 kgDM/ha a day for around a fortnight, less than half what I'd expected.

At the beginning of December the feed ahead was looking tight enough that I decided to draft the lower yielders into a once a day milking herd and cut back their feed, to allow the remainder of the herd to continue being fully fed. The day I separated the cows was the day it began raining, and within ten days there was no further need to ration grass as the urea that had been applied just before the rain gave a further boost to growth rates.
However, the once a day herd looked happy in their small group and I haven't returned them to the main herd, being quite content to milk 'only' ten rows at night.

At the beginning of January both herds were going into grass at 3750kgDM/ha (15 cm in length) and struggling to clean up (down to 2100 kg DM/ha - still on the late spring scale, about five cm). As the grass cover ahead of them had increased their allotted area had been reduced - from 19 days before the dry spell, and 2 - 2.4 ha daily to a 30 day round at 1.4 ha daily. For a few days I'd been considering the possibility of a surplus appearing ahead of the cows, and trying to double-guess the weather to figure out whether it was safe to cut January silage.

Lengthening the round going into the summer is wise - the main reason being that grass growth rates are over their peak in late spring and will decline through summer and autumn. Moving from a short round (which maximises milk production and maintains grass quality in mid-late spring) to a longer one allows the normally good growth rates of December to increase the feed cover across the whole farm without any quality loss, and compensates for the reduced growth expected through January and early February. Maintaining the longer round provides a buffer that balances out the spurts/slow-downs in grass growth through the summer.

To put it in simple terms - if it's dry in summer the grass growth may all but cease. A couple of days of decent rain will restart growth across the whole farm, regardless of what length the individual paddocks are.
In mid-late spring on a 16 - 21 day round, a decent rainfall guarantees a feed supply for the herd for a fortnight, if it doesn't rain again.
On a 28-day round, a decent rainfall guarantees the feed supply for three weeks.
On a 35-day round, a decent rainfall will probably ensure four weeks build up of grass. In practice, rain usually falls every fortnight or three weeks through the summer. To really start suffering from drought, therefore, on a longer round you need to see little or no rain for about six weeks. On a twenty-one day round, three weeks without rain can ensure a feed deficit that it will be hard to recover from. long enough.

This is why I'm wary of taking grass out of the system in the summer. Soil temperatures at this time of year are such that a moisture deficit is almost inevitable - unless rainfall is exceptional, the evaporation rate will be greater than water added through rain. Surplus grass is better employed in building up feed ahead of the cows, to ensure they are fully fed for as long as possible into the summer.
Unless, of course, the farm really does have so much grass that the desired grazing rotation can be achieved while fully feeding the cows, and still there is more food ahead than the cattel can utilise.

Which is where we were at the beginning of January. That's what my gut told me - that I could afford to drop out maybe two paddocks ahead of the cows and cut it for silage in another two or three weeks.
Those pieces of card in the image above?
That was me not only verifying that 'gut feeling', but also establishing exactly how much I could afford to drop out and what growth rates I needed daily to fully feed the cows on the remaining area.
We were already on a thirty day grazing rotation, and I would call that optimal - 28 to 30 days from January to Autumn. The grass is past running to seed at this time of year and quality is easily maintained, provided grazing pressure is hard enough. In general I prefer shorter rounds rather than longer - I'm happy with 45 reducing through early spring, 17 through mid-late, 24 - 30 through summer and 60 in winter - much longer than those and palatability is reduced, growth isn't maximised and the cows may find it harder to leave an even residual. Lots of good farmers say otherwise, and I made the decision to use a very long winter round myself, last winter (because optimising feed quality wasn't my first priority - adequately feeding a large number of cows was).
I could have tightened the cows up further, extending the rotation out to 35 or 40 days then allowing it to come back to a slightly shorter round when growth reduced. I didn't want to do that.
I could have continued allowing the cows the same area, and used the topper to clean up what they left behind. This would maximise milk production per cow right now, but be inefficient use of the grass available, and reduce potential production per hectare.
Or skip the grass ahead of them and plan to cut it when it had bulked into a sufficient crop. The good part about this is that if the weather screws up and the grass stops growing, I can breakfeed those paddocks ot the cows while growth is catching up ahead of them again. The bad part is that if I cut them while growth is in a slow phase, and then run out of grass, I've wasted time and money because in a worst-case scenario I have to feed silage back to the cows in place of the grass removed from the feed wedge.

I needed concrete information to enable the decision.
* Pasture cover immediately ahead of the paddocks I'm contemplating skipping
* pasture cover of the proposed silage paddocks (to check that they're worth cutting)
* Average farm grass cover
* Forecast growth rates (guessed from current growth rates and weather forecast)
* Area required each day for grazing (calculated from cow requirements in kg DM, available cover per ha and number of cows)
* Total farm area
* Total cow numbers

A few calculations told me that I could feed the cows at their present rate, on a thirty day round, with 29 of the 31 available paddocks and a projected growth rate of at least 52 kg DM per hectare per day.
The unknown variable was the weather. If rain didn't fall within a week or so, the farm wouldn't achieve the required 52 kg daily growth, and the skipped paddocks wouldn't bulk up to a decent crop.
The weather forecast said no rain in sight.
I dropped the paddocks out anyway - after all, they could always be grazed if it turned out to have been a bad decision.
A week later we had two days of good rain.

Our neighbour cut silage yesterday. Mine will be ready in a bit over a week. It's a welcome boost to what was a rather low supply of conserved feed set aside for autumn.

posted by nellta holdings @ 3:30 AM