There could be many reasons for this. It’s possibly just chance, maybe the favourite explanation of climate change, and certainly as far as the demonstration farm is concerned, a significant planting of later maturing species, as part of the past pasture renewal programme. My observation over the years is that if seed head formation is delayed, when it finally comes it does so in a rush, and the later this is the more spectacular is the transition from leaf to prolific stalk and seed head.
The other item that came up for discussion was the recent decline in production. Because of good levels of 1.9-2kg milksolids (MS)/cow/day generally holding from late September through to early November, this was still about 5% ahead of last year in total. However, come mid-November, it dived. This is best illustrated by the production record from the low-cost herd, which was fed pasture only. On November 10 production for this herd had dropped to 1.81kg MS/cow, but then it plummeted to reach 1.67kg MS/cow by November 24. It would be easy to attribute most of this to weather conditions. However this argument loses much validity when, at the same time, the intensive herd’s production went from 1.99kg MS/cow to 1.95kg MS/cow, a relatively small drop. The distinguishing factor was this herd was still getting 2-3kg/cow/day of palm kernel.
Another common explanation for the decline in production in November is that by then there will be a substantial proportion of the herd in-calf, and increasing every day.
This is an attractive and seemingly logical deduction. The rationale is that, in the natural world, where life is geared to the survival and continuation of the species, the maternal priority must shift from the calf at foot, which is now getting strong enough to thrive and prosper, to the foetal calf which need lot of TLC before it’s capable of looking after itself. So milk supply diminishes as maternal nutritional assets are diverted to the foetal calf.
‘The traditional cow of Mother Nature bears little similarity to the modern dairy cow, which is the end point of about 200 years of intensive, selective breeding.’
Unfortunately, while persuasive, the argument has little validity. The traditional cow of Mother Nature bears little similarity to the modern dairy cow, which is the end point of about 200 years of intensive, selective breeding. The result of this is a cow that is quite capable of producing enough milk to rear at least four calves, rather than the one, or rarely two, required by Mother Nature. In reality, the foetus won’t need any significant nutritional input until at least five months into the pregnancy. This is confirmed by the recognised guidelines of increasing maintenance feeding at eight weeks before calving, with further increases at four weeks before calving.
The conclusion has to be that the major factor causing the decline in milk production is the decline in the quality of feed being offered to the cow. This is quite apparent from the data from the demonstration farm. The fact there was a big drop in daily production at the same time as a sudden and dramatic alteration in pasture characteristics was no coincidence. The commonly accepted belief that cows will peak some time in late spring and then experience a continual steady decline until drying off late autumn, and that this is an immutable law of nature, is largely a fallacy.
‘My observation over the years is that if seed head formation is delayed, when it finally comes it does so in a rush, and the later this is the more spectacular is the transition from leaf to prolific stalk and seed head.’
This is confirmed by the fact that in situations where quality feed is provided, the decline in production levels the peak kept very low. This can be seen in studying production records from northern hemisphere cows being fed primarily bought-in feed of consistent high quality. Many New Zealand dairy farmers would have observed this, admittedly to a lesser degree, when reasonably high levels of palm kernel have been supplemented all the way through the lactation.
It would be logical to conclude that the way for the NZ dairy industry to increase productivity is to extensively supplement all post-peak feeding with high quality bought-in feed. While this might be a logical conclusion it is not a good one. The better option is to try to maintain pasture quality, and thus feed quality, right through the latter part of the season. This is made particularly relevant by the precipitous fall in dairy prices.
There is no argument that with the advent of stalk and seed head in a pasture its feed quality will drop. Feed quality is generally assessed by the metabolisable energy (ME) of the feed. This is expressed in megajoules of energy per kilogram of dry matter (MJ/kg DM). Thus we have leafy ryegrass white clover pasture in the spring with an ME of up to 12.5 MJ ME/kg DM. This can drop as low as 8.0 when dry and stalky in the summer, especially when poorer grass species are also present. Leaving aside the values of the total pasture, the point can be further made by looking at the individual plant data. For ryegrass a fresh green leaf in the spring will typically have an ME of 12-13, a dead leaf 7-8, a green stem 11, and a mature stem 8. Closely associated with ME is digestibility, the proportion of the feed consumed actually metabolised and thus used by the grazing animal. Leafy spring pasture digestibility will likely be, on a DM basis, 80%-85%, dropping to 60%-65% for stalky summer pasture.
The common belief is that lower quality feed will reduce production because it isn’t such a good raw material for the manufacture of milk. While this might be true, the greater influence is the reduced intake resulting from lower quality. Appetite is reduced by the lower quality feed being less palatable. With lower digestibility, the food takes more time to be processed and moved through the gut. As a result the animal feels less hungry – what is known as a double whammy. When its summer and generally hot, grazing and digesting food is hard work and tends to be avoided, so it isn’t surprising intakes are reduced.
Over the years I’ve often heard dairy farmers in summer and autumn say “I don’t know why they are dropping in production so fast, they’re getting plenty to eat, look how much they are leaving behind”. The next day they go into a regrowth silage or hay paddock and the pasture is evenly grazed out to ground level – intakes are obviously up on previous days, as is the resulting milk production.
Generally, in NZ, half the season’s milk production will be obtained after mid-December, so good summer and autumn production levels will be critical to ensure a satisfactory season. There can be no doubt that for the pastoral farmer, the key to achieving this has to be management to ensure a continual level of quality pasture over the whole period.
It’s not a simple task but ideas on how to do it will have to wait until February.
