For most of us, it is hard to remember that this is still winter. Spring calving farmers now know why autumn calving herds find calving so much easier – dry warm weather and no mud!
Too much winter grass – ketotic cows
However, the unusually high growth rates of June and July and going into August in many parts of the country mean average pasture covers at PSC were, and are still, high, with not enough mouths at maximum appetite to cope. This is causing some big dilemmas on farms and the results in some cases are starting to show up as ketotic cows in the face of supposedly plenty of grass.
Problems for lactating cows
Pasture-based dairying is always a compromise between what is best for the cow, best for the pasture and best for the long-term productivity of the farm. Traditionally in New Zealand, it is the cow that has been most compromised, especially at calving and in early lactation, as too much attention is focused on pasture quality and control. The 21st century cow does not cope well with this – if you cut her off at the knees before she has recovered from the metabolic and hormonal changes of calving and before she has had the opportunity to develop best appetite and intake, there are big downstream costs. Too much condition loss, poorer reproductive lactation length and lactational persistency included; clinical and sub-clinical ketosis may exist on top of the above.
We also know that at some stage we need to have control of pasture growth to maximise quality going into peak lactation and summer, so as to maximise mid-lactation production.
To meet these two goals, we recommend that the cow comes first through calving, so from 1st July, August into September. Worry about achieving maximum gut fill in a healthy cow with optimum appetite, not necessarily about achieving post-grazing residuals of 1500-1600 Kgs DM / ha! From late September through December pasture management is critical, but by then, if you have looked after the fresh cow, she will have the appetite to eat more (and not care what it is!) and weather conditions will tend to favour pregraze mowing to both increase cow intake and get even control without waste and without having already stuffed cow performance for the rest of the season.
At the moment, too many early lactation cows are being forced to eat into the base of overlong pasture which is actually not helping their long term goals of total performance, health and reproduction. This keeps rotation lengths long and slow, which means even more poor quality grass is developing ahead. And much of this is especially poor quality at the base. Having seen some of the lowest pasture sugar levels we have ever recorded this autumn, we are now seeing exceptionally low ME levels in grass that looks o.k. at a glance. Hamilton’s record cloudy July certainly hasn’t helped in the Waikato but overall NDF levels are high, digestibility and energy low. Grass is tough. It is hard for cows to actually collect as much as they need to meet their energy needs especially at this stage of lactation, anyway and this is made worse if they have to eat the really poor quality stuff at the base. This type of management also has the untoward result of actually delaying the development of maximum appetite and exacerbating the rate and degree of body condition loss, hence the high potential for clinical and sub-clinical ketosis. This is further worsened if cows are not being fed enough supplement. If cows are cleaning out the bins and trailers you need to be giving them more! With an apparent pasture surplus, this can be difficult to get your head around, but you cannot change how the early lactation cow is designed, and you cannot achieve higher bite rate or bite size just by wishing for it to happen!
The best option at the moment – don’t get too concerned about pasture grazing residuals with milkers. There is plenty of time to sort this out without compromising the rest of the season! The number one priority is to make sure they are full and fully fed.
Practise two tier grazing. The leafiest stuff on the top is all that is ideal for milkers and the colostrums. Put them through the paddock first, grazing down to around 2000 only, and then follow with the remaining dry cows and springers while you still have them! This means that calving cows can get a much bigger area which is better for them and they get less problematic N and K in their diet. There is no excuse for any cows overgrazing at the moment on most farms. In some cases, some early cropping or early silage harvesting may be needed but there is still a long way to go. We have the opportunity to fully feed early lactation milkers and develop high intakes, but it will not happen if they are on limited pasture area grazing non-milk-producing, stalky, low-energy, tough grass, especially if not getting adequate low volume, energy-dense supplements as a complement.
