The Curtins Research farm adjacent to Moorepark has long been associated with long-term genetic and feeding system studies. In 2013, a new study comparing Jersey crossbreds and Holstein Friesians on three different stocking rates started.

The objective of the trial is to test if efficiency in grass growth and utilisation could be improved. The researchers decided to use two different breeds of cows at three different stocking rates to try to test the relative efficiencies of each breed at contrasting stocking rates.

The issue of cow liveweight is core to this topic. The trend in grass-based milk production systems worldwide is a move to smaller cows which weigh less than 500kg in mid-lactation. Mature herds in these systems can produce up to 500kg of milk solids per cow at grass (1kg of milk solids per kg of liveweight).

However, per-hectare production rather than per-cow production will be the best measure of output in a non quota world.

On average, the Jersey crossbreds this week are weighing about 470kg, compared to the Holstein Friesians at around 535kg, a difference of 65kg of liveweight per cow.

When cows are stocked at 2.5 to 3.5 cows/ha, this makes a difference. Finding out exactly what difference and what efficiency gains can be expected is part of this Curtins trial.

Is a cow weighing 550kg producing 400kg of milk solids more efficient than a 450kg cow producing 400kg of milk solids per year?

Moorepark research suggests the bigger cow will consume 0.3t more dry matter in the year, which is almost 1t of dry matter more per hectare. When hectares rather than milk quotas are limiting production, as will be the case post-2015, then the more you can grow and utilise profitably, the more your farm income and profit will grow.

Spring calving to grass

Before we start, Brendan Horan and pHD student Emma Louise Coffey explain the four driving principles of spring calving to grass. The first is to target 90% home-grown feed, reducing the impact and risk of purchased feeds into the system.

Secondly, it must be environmentally efficient, so for the last number of years, all nitrate levels in ground waters around and under the Curtins farm have been measured and tell a good story. Thirdly, the primary source of feed must be from grazed grass over a long grazing season (285 days plus). Finally, you need to expect high milk productivity (over 1,250kg of milk solids per hectare). Fundamental to delivery of the above is compact calving in spring to be able to match milk with the grass supply from the farm.

Current trial

This Curtins trial is looking for answers to the following questions: Is the impact in the change in stocking rate similar for Holstein Friesian and Jersey crossbred animals? What will be the effect on milk production, liveweight, condition score, animal health and feed efficiency? In terms of grass grown, etc, the trial should also provide answers about the impact of changing stocking rate (liveweight/ha) on the farm – grass grown, utilised and the environment?

As you can see from Table 1, there are Holstein and Jersey crossbreds on three different stocking rates, ranging from 2.4 Holsteins/hectare up to 3.4 Jersey crossbred cows per hectare in the high stocking rate group.

Cows in the high stocking rate group will obviously produce less milk solids per cow because grass won’t be as plentiful, but maybe they will produce more profitably per hectare?

In each system, 250kg of bag nitrogen is used and all paddocks are measured every week (grazing and silage).

Results to date

Farm manager Steven Fitzgerald and Emma Louise Coffey took me around the farm and explained some of the observations to date.

Obviously the trial is only halfway through its second year, so long-term conclusions cannot be drawn just yet, but trends and differences are appearing.

Grass grown

In year one of the trial (2013 – a late spring and small droughts through the year), there wasn’t much difference in total grass produced over the year (13.2 to 13.6 t DM/ha).

However, the low stocking rate system made much more silage than the high stocking rate group (3t DM/ha v 1.9t), so the high stocking rate system had to purchase silage for winter feed. So, as expected, there was surplus grass in the low stocking rate system converted to winter silage (1.25t DM/cow – plenty for a Cork winter), while the high stocking rate system was short silage for winter feed which needed to be purchased (over 0.5t DM/cow).

Purchasing winter feed means you are also purchasing nitrogen into the farm (obviously as silage, not bag nitrogen). The high stocking rate group consumed more grazed grass (11.3t DM/ha v 10.3t DM/ha).

Milk solids

You can see the milk production differences in Figure 1. The milk solids production per hectare is obviously the important barometer in coming years, so you can see the range is from 1,475kg MS/ha for the Jersey crossbreds stocked at 3.3 cows/ha, right down to 1,109kg of milk solids per hectare for the Jersey cross cows stocked at 2.4 cows/ha.

That’s a difference of 366kg of milk solids per hectare at the extremes, which, at a price of €5/kg MS is €1,830 per hectare, and, if you are farming 40 hectares, that’s a difference in output of €73,200 per year.

This output difference is highly significant, but of course you will have higher costs with the high stocking rate system that impact on profitability. In a year like last year, when grass growth suffered in the spring and again at various times through the year due the drought, a lot of extra feed has to be purchased. In a commercial farm, feed is plugged in when required.

Steven Fitzgerald maintains obviously you can minimise this cost/risk by growing and utilising as much grass as you can, but in years like last year, you will still get caught with extra costs.

Fertility results

The impact of the high stocking rate system on fertility was very apparent last year. The high stocking rate group was under pressure for grass at various times of the year, which obviously reduced condition score, and that group finished up with 22% not in-calf.

Meanwhile, the low stocking rate group ended up with 8% not in-calf, which was a very good result. This year, the fertility results are better overall and while there is a numerical difference in favour of the high stocking rate, there is no significant difference when analysed.

The high stocking rate group had only 2% not in-calf at the end of the breeding season, compared to 11% not in-calf in the low group. Six week in-calf rate is 70% for the high stocking rate group, compared to 56% for the low stocking rate group.

Again there is a numerical breed difference in fertility, but analysis suggests this is not significant. The pregnancy rate to first service was 35% for the Holsteins compared to 49% for the Jersey crossbreds, but the six week in-calf rate was the same for both breeds at 65%.

Observations

In terms of production, Emma Louise suggests while there are extra milk solids produced per hectare on average in the high stocking rate systems, they do mean more purchased feed.

She emphasises that you need to have the flexibility to feed more during lactation and source/buy winter feed because there will be times during the year, depending on weather, when you won’t be able to grow enough winter feed or have enough grazed grass for milking cows.

Steven suggested aiming to feed 260kg to 330kg of meal per cow is probably unrealistic in a high stocking rate system, especially in years when growth is difficult, like 2013.

He said: “We do have a hybrid grass (Shogun) in one paddock and that paddock grows more and needs to be grazed more often, so maybe hybrids may have a role in feeding a high stocking rate.”

The right stocking rate for your farm all comes back to what grass you can grow and utilise for the main five to six months of the grazing season. Early indications suggest a stocking rate of 2.9 to 3.0 cows/ha looks like the most sensible stocking rate for the majority of farms post-2015 and Jersey crossbreds look like a real option for those not achieving good fertility with black and white cows.