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Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed ('higher input-high efficiency', HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed ('lower input-high efficiency', LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable. [ABSTRACT FROM AUTHOR]

A short-term, dairy cow, grazing experiment was conducted in late-lactation (autumn) to determine the effect of fodder beet (FB) and maize silage supplementation on dry matter and nitrogen (N) intake, urinary N excretion and milk solids (MS; milk fat + milk protein) production. Seventy-two multiparous, lactating (224 ± 20.0 DIM; mean ± SD) Holstein-Friesian cows were randomly assigned (n = 24 per treatment; 8 per replicate) to one of three groups. Control animals were offered pasture (11 kg DM/cow/day) with maize silage (4 kg DM/cow/day; 'Maize'). The other two groups were either offered pasture (11 kg DM/cow/day) with 25% FB (4 kg DM/cow/day; 'FB25') or pasture (9 kg DM/cow/day) with 40% FB (6 kg DM/cow/day; 'FB40'). At the same supplement DM intake, diets containing maize silage or grazed FB had similar urinary nitrogen (UN) concentrations, but FB increased milk solids (MS) production. At 40% FB inclusion UN excretion was reduced but this came at the expense of MS production. Farmers need to exhibit caution when feeding fodder beet to lactating dairy cows to minimise the risk of adverse animal health effects. Feeding fodder beet allocations high enough to achieve significant environmental benefit is likely to compromise animal health and milk production. [ABSTRACT FROM AUTHOR]

Autumn grazing of high-yielding forage crops such as fodder beet (FB) has increased in popularity in many regions of New Zealand. During grazing, large amounts of urinary nitrogen (N) is returned to the soil which is at risk of leaching. This study evaluated using two different catch crops of oats or Italian ryegrass ('Italian RG') to reduce the risk of N leaching both after FB grazing by lactating dairy cows and after lifting (i.e. un-grazed FB) in autumn. During FB grazing, cows grazed either (i) high [40% of diet dry matter (DM), with pasture; FB40] or (ii) low (25% of diet DM, with pasture; FB25) FB allocations. Both Italian RG and oats reduced soil mineral N (0–90 cm depth) by 16%–37% by August, and 53%–58% by October, compared with a fallow control (115 and 100 kg N ha−1 for August and October, respectively). The greatest reductions in soil mineral N were from oats, largely attributed to higher DM yields resulting in greater N uptake. Furthermore, the total amounts of soil mineral N in the soil after grazing differed between FB allocation treatments and lifted FB (FB25 > FB40 > lifted FB), in proportion to urinary-N inputs and associated dietary N intake. [ABSTRACT FROM AUTHOR]

Simple Summary: Dairy farm system practices aimed at reducing nitrate leaching can also reduce emissions of the greenhouse gases methane and nitrous oxide. A study comparing 'current' and 'improved' grazed dairy system practices showed that 'improved' systems generally produced lower greenhouse gas emissions while milk production was maintained. The amount of feed eaten per hectare was the key driver of total greenhouse gas emissions per area, with 'improved' systems generally exhibiting lower total enteric methane and less N flowing through the herd. An important challenge facing the New Zealand (NZ) dairy industry is development of production systems that can maintain or increase production and profitability, while reducing impacts on receiving environments including water and air. Using research 'farmlets' in Waikato, Canterbury, and Otago (32–200 animals per herd), we assessed if system changes aimed at reducing nitrate leaching can also reduce total greenhouse gas (GHG) emissions (methane and nitrous oxide) and emissions intensity (kg GHG per unit of product) by comparing current and potential 'improved' dairy systems. Annual average GHG emissions for each system were estimated for three or four years using calculations based on the New Zealand Agricultural Inventory Methodology, but included key farmlet-specific emission factors determined from regional experiments. Total annual GHG footprints ranged between 10,800 kg and 20,600 kg CO2e/ha, with emissions strongly related to the amount of feed eaten. Methane (CH4) represented 75% to 84% of the total GHG footprint across all modelled systems, with enteric CH4 from lactating cows grazing pasture being the major source. Excreta deposition onto paddocks was the largest source of nitrous oxide (N2O) emissions, representing 7–12% of the total GHG footprint for all systems. When total emissions were represented on an intensity basis, 'improved' systems are predicted to generally result in lower emissions intensity. The 'improved' systems had lower GHG footprints than the 'current' system, except for one of the 'improved' systems in Canterbury, which had a higher stocking rate. The lower feed supplies and associated lower stocking rates of the 'improved' systems were the key drivers of lower total GHG emissions in all three regions. 'Improved' systems designed to reduced N leaching generally also reduced GHG emissions. [ABSTRACT FROM AUTHOR]