Good quality well-managed pasture is an excellent feed for dairy cows – if only cows could graze more of it, says Howard de Klerk.
There have been a plethora of articles recently that have bagged the use of supplements. One recent article said that if a cow ate enough pasture to provide the required digestible nutrients, she would not be deficient, implying cows need pasture only. The key words are “if” and “required”.
However, this referred to United States research in 1936. At that time, the average cow in the US produced about 225kgMS/cow. Based on energy requirements, such a cow would only require about 3700kgDM or 12-13kgDM of good quality pasture. It was correct that such a low daily requirement could easily be met by pasture only.
New Zealand’s average production per cow has improved from 308 to 377kgMS in the past 10 years, currently requiring about 16kgDMI per day. This is a long way from a modern cow’s genetic potential, but the average New Zealand cow could satisfy this low requirement from pasture only.
But is this the most profitable approach?
Good quality well-managed pasture is an excellent feed for dairy cows – if only cows could graze more of it.
It is not a qualitative problem but a quantitative problem. Cows simply cannot graze enough of it to support modern-day potential production levels, the reason why New Zealand cows are only producing about 380kgMS/cow. This is the reason many New Zealand farmers are using energy-dense supplements to increase DMI, production and profitability.
Previous researchers at Ruakura, like Eric Kolver, did a number of trials on supplements in the 1990s and reported that cows producing 29.6kg milk per day could only eat 19kgDM from pasture. However, similar cows on total mixed ration (TMR) diets consumed 23.4kgDM and produced 44.1kg of milk, not that anyone is suggesting TMR diets in New Zealand. Kolver concluded that research, both locally and internationally, suggested that the maximum pasture intake is about 19-20kgDM for a 500kg cow at peak intakes. IF only cows could graze more pasture!
Substitution is a favourite bogyman in New Zealand. I have heard it stated a number of times that the energy added through supplements will simply be left behind as wasted pasture, comparing supplements to feeding a child chocolate cake before dinner. This is a favourite half-truth.
If there is no net gain in energy intakes when supplements are fed, how is it possible that some herds in New Zealand on pasture plus supplements are producing 500-600+kgMS/cow? While there is no doubting that substitution does exist, the information is often selectively presented to fit the narrative of pasture only.
Results from a feed trial that showed that cows eating the SAME amount of energy per day, whether from pasture or pasture plus supplement, produced the same amount of milk. This should be no surprise. This research is often presented when discussing substitution, leaving farmers with the perception that pasture will produce the same amount of milk as pasture plus supplements. Farmers need to understand that this trial was conducted in pens and cows were not free grazing. What the cows ate was carefully controlled. The more grain the cows were fed, the less cut grass was offered. There was no opportunity for cows to increase energy intakes, as the trial simply compared different energy sources that provided the same amount of energy.
Kolver also reported that cows on pasture produced 269kgMS, while similar cows on pasture plus maize silage produced 363kgMS/cow, cows on pasture plus maize grain produced 400kgMS/cow, while cows on pasture plus a balanced ration produced 407kgMS/cow.
If the net gain in energy intake was zero due to substitution, how is this increase in production possible? The reported response to maize silage supplement was 78 grams MS/kgDM of maize silage; 99 grams MS/kgDM of grain and 99 grams per kg of balanced pellets, which just happens to be very similar to what numerous others have reported in New Zealand and what we typically see on-farm. Kolver found the response to extra supplemented energy was 7.5 grams MS per MJ ME for maize silage, maize grain or balanced pellets.
Monitoring milk responses over the short-term rather than over the whole lactation can be very misleading but is often quoted in preference to the previous full lactation studies.
The key to profitable supplementation is to ensure the cow eats the maximum amount of pasture she can physically graze, and is then supplemented to optimise DMI and milk production.
The first 4000-4500kg a cow eats must be homegrown pasture. Offering more pasture than the cow can physically graze is a sure way to waste grass.
Increasing stocking rate and buying in feed to carry more cows, for which there is not enough available pasture, is a sure way to get low response rates and lose money. Choose the right system with the correct stocking rate and efficient supplementation will always be profitable, as long as the marginal cost is kept below the milk price.
In most parts of the world the protein fraction of the diet is the most expensive component, while energy from grains is relatively cheap.
In New Zealand we are in the fortunate position to have surplus cheap, protein in pasture. Supplementing cheap grain (additional energy) to improve the utilisation of the protein in grass, which would otherwise be wasted, is a massive competitive advantage for New Zealand, but is not being fully utilised.
With typical response rates of 100 grams MS/kg of grain measured over a lactation, simple maths would reveal that $3 grain (10kg) would give 1kg milksolids worth $6.
Even if the total costs of producing the extra milk solids increased by 1.5 times the cost of the supplement, the cost of producing the additional milk solid (the marginal cost) would be $4.50 per MS.
The economic rule states, that if the cost to produce the additional milksolid is less than the milk price, then it is beneficial to increase production.
Not using supplements to increase profits this season was a wasted opportunity. In fact, data published at DairyNZ Farmers Forums showed that on average, over nearly a decade, the marginal cost (the added cost for the additional milk produced from the use of supplements etc) was lower than the milk price, which shows that using supplements has been profitable over the past decade.
This is confirmed by the graphs showing an increasing profit as production increased per ha in DairyNZ annual economic surveys. Farmers are urged to check this for themselves on DairyNZ’s website.
Farmers are advised to make sure their consultant (and scientists) understands the concepts of marginal analysis and proper use of supplements to design a system where total farm profit is maximised, rather than pursuing a system that maximises profit per milksolid. Farming for the lowest FWE/kg MS is seldom the most profitable system.
Using supplements to maximise New Zealand’s competitive advantage of cheap surplus protein in pasture makes perfect economic sense. What a pity there are so many conflicting messages when the data is so clear. This is costing the New Zealand dairy industry millions.
Source: Stuff
