Farmers on extensive sheep and beef farms on hard hill country can continue to make production and eco-efficiency gains by increasing the reproductive performance of ewes and lamb weaning and growth rates, he told the Animal Production Society’s annual conference.
They can shift from breeding cows and older cattle to buying and finishing younger cattle.
However, though there are also options to make further production and eco-efficiency gains in more intensive livestock systems there is less scope to reduce their environmental footprint.
Mackay, who co-wrote a paper with fellow scientists David Scobie and Brian Devantier and agricultural consultant Tim Rhodes, on whether progress has been made in increasing the eco-efficiency of livestock systems, said changes in sheep performance and the shift in cattle policy both represent efficiency gains, with more forage eaten by young, growing animals and fewer lighter animals wintered.
To advance the change to a cattle policy focused on buying and finishing younger cattle on harder country will require expansion of dairy calf-rearing infrastructure and buy-in from meat processors.
The research found reductions in greenhouse gas emissions are small across farming systems compared to improvements in nitrate leaching and phosphorus loss, highlighting the lack of practical options to reduce emissions to air compared to water.
A Productivity Commission report last year suggesting large tracts of hill country be planted in trees to balance livestock gas emissions is a poorly informed approach because it offers only a short-term offset, the paper said.
Instead, policy should encourage the development of long-term, integrated approaches to land management.
It gave the example of a wetland on a Wairarapa dairy farm to cleanse water leaving the property, which has the potential to reduce nitrate loss, capture phosphate, sediment and microbial contaminants in run-off and accumulate carbon while providing habitat for indigenous aquatic life that has become endangered because of widespread drainage of wetlands.
Returning wetland tree species like kahikatea will accumulate carbon through increased sequestration and add to the indigenous biodiversity in a similar manner to that achieved through remaining vegetation on sheep and beef farms.
Nutrients captured in a manufactured wetland can also be salvaged and returned to farmland as a buffer at the bottom of farmlands to mitigate more than just carbon.
More importantly, each sector will shoulder the environmental cost of its business.
The research also noted in areas where crops like forage brassica, fodder beet or maize silage are grown for animals it might be more profitable to grow vegetables for human consumption. Large areas might revert to growing grain crops where intensive livestock farming has recently been more profitable.
However, a large proportion of the area farmed with sheep and beef is not suitable for cultivated crops and animal-based production will likely prevail on areas not converted to forestry or regenerating native bush. That production might tend towards other species such as goats or deer, depending on relative product values.
Mackay said that in the process of addressing outstanding environmental and animal welfare challenges, pasture area will decline, limiting production gains.
On the upside, in addressing outstanding sustainable land management practices, the potential exists to offset more than 20% of livestock greenhouse gas emissions on the hard hill country farming system beyond that already offset by woody vegetation on those farms.
A greenhouse gas budget for sheep and beef farms needs to include carbon sequestered by vegetation to obtain a complete picture of the net contribution to the gas inventory.
“As we move into an era where limits are set on emissions to the environment, how livestock systems affect emissions to receiving environments shifts from an academic exercise to a key performance indicator for the business.”
