That is, the low input herd, relying primarily on a totally pasture-based feeding regime, has always had lower production than the high input herd which has the ability to have its pasture supply supplemented with brought-in feed, which because of the much higher stocking rate is a very frequent requirement. In last month’s issue, I attributed most, if not all, of this ongoing difference to the much better condition of the high input cows at calving. In mid-November we were at a point where production for both herds was on the decline, as is to be expected. The low input herd is currently milking at 1.7kg milksolids (MS)/cow/day, down from a peak of 1.72kg MS late October, while the current level for the high input herd is 1.95kg MS, down from a peak of 2.0kg MS.
That the continuing superior production of the high input herd can still be attributed to the better condition at calving is still a reasonable supposition, as earlier research work at Ruakura Research Station showed quite clearly that production gains made from ideal liveweight (LWT) condition at calving would carry over for the whole of the season.
Some further support for this contention would come from the fact that the condition difference between the two herds was consistent, although the gap narrowed somewhat. The low herd declined from body condition score (BCS) 4.9 at calving to 4.4 mid-November while the comparable figures for the high herd were 5.5 to 4.7. The picture was somewhat further confused by the fact that initial mating results looked good, with a 98% submission rate at three weeks for the low herd and 100% for the high, although admittedly proportionately more CIDRs were used for the former.
The big question is,”How long will it continue to be profitable to keep supplementing the high input herd?”
There's no simple answer to this. Superficially you could say for the rest of the season, because there’s a fairly substantial leeway. Currently the low input herd is consuming 16.5 kg drymatter (DM)/day of pasture, the high input herd 14.5kg DM/day of pasture plus 2.8kg DM of palm kernel. The difference in production is .25kg MS/day (1.95–1.7).
Price and production
Simply put, if palm kernel costs average 30c/kg DM, and 2.8kg is producing .25kg MS, some simple sums will show that provided the MS price stays above $3.36/kg MS continued feeding will be profitable. (And if it doesn’t, rest assured there would be much bigger, urgent and more important questions being asked than whether to continue feeding palm kernel).
It's at this point the low input herd data becomes of little use in the decision-making process. We know from past experience this herd is capable of peaking at 2.0kg MS/cow/day on pasture alone. The fact that it has not done so this year, as has been seen, largely goes back to condition at calving.
Despite late September/October ad lib feeding on quality pasture, production has not exceeded 1.76kg MS/cow/day, and is now on a downward trend, so if it were possible to feed palm kernel to this group logic would indicate that at best it would only slow the decline in production reduction.
The same basically also applies to the high group, but here there is a big difference and that is of course whether cutting out the palm kernel will drop total DM intake. The input levels from the low group would suggest this could well be the case. If so, would production drop with it and to what extent?
There are a lot of unknowns and uncertainties in all this but overall the key factor has to be pasture quality. I believe that in planning and implementing farm management, as a generalisation, pasture quality gets too much attention in early spring and not enough attention in late spring and early summer. As a result I have promulgated the rule of thumb that, from calving through to the onset of seedhead formation in the pastures, cows get priority attention. Once seedhead formation gets underway, pastures get priority attention.
The rationale behind this rule of thumb is simple. In early spring the grasses and clovers in the pasture sward are all solidly in the vegetative stage. When defoliation occurs, within a very wide range of grazing intensities subsequent regrowth will be all leaf. The words “pasture control” will mean many things to many people, but in the context of a high grazing intensity to ensure a high percentage of utilisation of the pasture present and a relatively uniform and even length of pasture post grazing, it has little application in early spring. This is simply because all regrowth will be leaf so that, by and large, what the cows leave behind this grazing they will pick up on the next.
If any mistakes in pasture management are made at this time they are likely to be small, and easily corrected, with plenty of time to do so. This is not so with stock management. Any mistakes in this area at this time of year will result in suppression of milk production which, it has been well established, will carry over for the rest of the season.
Feed levels
Without doubt the biggest mistake that can be made with stock management in early lactation is underfeeding. Reduced to the basics, in early lactation, the more a cow can eat the more milk she will produce, and a top level of production can carry over for the rest of the season. The cow’s daily intake will be limited by factors such as appetite, gut capacity, and grazing fatigue and to counteract these she has to be motivated to consume just that little extra morsel of DM.
To do this the feed on offer has to be highly palatable and highly digestible. It should also have a high energy value and preferably a high DM percentage. With the possible exception of the last criteria, fresh spring pasture ticks all these boxes, thus the rule of thumb. Up until the onset of pasture seed head, stock has priority and after that pastures have priority.
With pastures moving into the reproductive phase, naturally quality will drop and with this, on a predominantly pasture diet, intake and hence production will also go into decline. The high spring pasture growth rates mean pasture supply is adequate, and, as designed would be quite capable of supporting the high input herd. With efficient feed utilisation the aim, the options for this herd then come down to;
* Continuing to offer palm kernel with the aim of maintaining high intake, while at the same time hoping that because of the supplementation cows will be capable of grazing the paddocks harder, helping maintain pasture quality, and creating surplus feed for silage, or
* Ceasing the palm kernel supplementation hoping that the higher grazing intensity will be able to take care of most pasture control requirements, but being prepared to top if and when this fails.
There are of course other less attractive options, and all have their economic implications. At the time of writing, we have no fixed plan of action – which is as it should be for any grazing management plan. So in next month's issue I will continue the discussion on strategies to slow the mid to late season decline in production, and report on results to mid-December on our two herds.
Watch this space.
