Dairy NZ

Some of the past research projects at NARF include:

• Split Calving (Autumn and Spring) vs. Spring Calving
• Autumn Calving vs. Spring Calving
• Maize Silage Supplementation
• The Role of Pasture Toxins in Summer-Autumn Milk Production Decline
• Mastitis Productivity Trial

Split Calving (Autumn and Spring) vs. Spring Calving

Over the years MAF and AgResearch and other conducted a large number of trials on grasses, animals and crops in plots and farmlet trials. More recently (1994-1997) the farm demonstrated that split calving (autumn and spring) works very well even on wet soils suck as the Kaipara marine clay on which much of the then 61 ha milking platform was based. A three year demonstration showed milk production increased by up to 20% under the split calving system compared to conventional spring calving. This demonstration provided the information for many of the 400 or so Northland suppliers who altered their calving systems. Under the split calving system the farm achieved 1030 kg MS/ha (350 kg MS/cow) on a mostly grass-based system which few farmers exceeded on the same soils around Dargaville.

Autumn Calving vs. Spring Calving

Following this, a three year trial comparing total autumn calving to spring, calving was initiated in 1997 and completed in 2000. This trial showed that a premium of $0.90/kg MS in May to July would give autumn calving the same profits as spring calving, somewhat of a surprise to many Northland suppliers considering the farm is considered by many as being far from an ideal total autumn calving farm.

Maize Silage Supplementation

In the 1999-2000 season a trial investigating the profitability of maize silage grown on 5% of the farm for autumn supplementation of the dairy herd was carried out. This showed that it was feasible to grow early-harvest maize silage and feed it out immediately over the autumn period. The maize silage was fed from 23 February to mid-May at an average of 2.75 kg DM/cow/day. The summer/autumn milk production of the supplemented cows increased by 59 kg MS/ha. The response rate was 1 kg MS:15 kg DM maize silage fed. The trial resulted in an increased profit of around $80 to $100 per hectare at a milk solids payout of $3.80/kg.

The Role of Pasture Toxins in Summer-Autumn Milk Production Decline

From October 2000 NARF embarked on a new trial to measure the effects of different ryegrass fungal endophyte strains on milk production, cow health and pasture composition and persistence. These fungi produce animal toxins which cause heat stress or nervous system dysfunction in the form of ryegrass staggers and may also cause depressed milk production and possible reproduction effects. These problems occur to varying degrees over much of the NZ dairying area.

In October 2000, 15 ha of the farm was sown with a novel endophyte rye (AR1, low levels of ergovaline and lolitrem B) and anther 15ha was sown with a high endophyte rye. The balance of the farm (30ha) was retained as the control area consisting of the resident rye/kikuyu mixed sward.

Two herds on the same newly established rye/clover with different types of endophytes in the rye were compared with existing pastures ranging from very old to new ryegrass/white clover with varying levels of kikuyu grass. The kikuyu influence was up to 95% of cover in autumn in some paddocks with the control farmlet about 50% kikuyu overall. This allowed a comparison of old pastures with a kikuyu base with new rye/white clover swards, a first under dairying in NZ.

Data Summary Endophyte Trial 2000 to 2003

Production Summary Endophyte Trial 2000 to 2004 (Kg MS/ha)

In all years, cows on the novel endophyte ryegrass farmlet (AR1) produced more milk per hectare than those on either the high endophyte farmlet or the control farmlet.

Mastitis Productivity Trial

Aim of the Trial

The aim was to examine the impacts of 2 key mastitis prevention treatments, Teat spraying & Blanket (whole herd) dry cow therapy on herd production and mastitis incidence, for cows managed within the same herd over a period of two years.  It commenced in July 2006 and completed in May 2008 and was conducted at NARF (240-250 cows) and TARS (120 cows, including 80 heifers) in Taranaki. 

Treatment Design

Results

Incidence of Clinical Mastitis across cows and heifers up to Dec 2008

Proportion of Cows infected with Strep. Uberis

Proportion of cows infected with Staph. aureus

Herd Production Differences for 2006/2007 and to Jan 2008

Summary

Teat sprayed cows had:

• Less Clinical mastitis in first season (44% less CM)
• Less Strep. uberis mastitis in the first season
• Less Staph. aureus mastitis both seasons
• Lower SCC post peak production
• SCC not sufficiently different to impact milk production.

Cows on "Selective" DCT had:

• More mastitis at calving (+24% more CM cows)
• Higher SCC for first few herd tests (+25% to Oct)
• SCC not sufficiently different to impact milk production for rest of season
• In real world, all these cows would have been eligible for DCT

NB - Full impact of not treating cows with DCT mitigated by "Selective" rules, requiring that 75% of cows be treated with DCT.

Conclusions

• Teatspray is a valuable tool
• Blanket DCT is an important tool in certain (high SCC) situations