Experimenting with transition
Research conducted on Dairy Trust Taranaki’s Kavanagh farm is considering the benefits, and downsides, of a transition to autumn calving. Anne-Marie Case-Miller reports.
C
ompleting his ag science masters degree through Massey University, with support from the DairyNZ Masters Scholarship, saw Jake Jarman make a retrospective analysis of transitioning to autumn calving, based on data collected from the Dairy Trust Taranaki’s Kavanagh Farm. The 208-hectare research farm, next to Fonterra’s Whareroa dairy factory near Hawera, transitioned to autumn calving between July 2017 and March 2019, with Jake beginning the data analysis in February 2019. “When I came on board, the experiment had been underway a while and the cows had just finished the extended lactation period and were about to calve the next month.” “The hard and fast transition process
72
comes with both risks and benefits and that’s what we were looking at,” Jake says. The benefits of that process include completing the transitioning of the whole herd at the same time and maintaining the herd. “If you’ve got a connection to the herd, maybe you’ve been breeding it up for years or maybe you just don’t want to sell it, then the extended lactation is a good option. You also get to control that process all the way through.” The risks include the unsuitability of New Zealand dairy cows for extended lactations which leads to cows gaining above-optimal body condition post 300 days in-milk, which can result in problems around metabolic risks heading into calving. “Because the cows don’t produce much milk later on in the extended lactation
period, there’s going to be a lack of milk production in the second financial year, relative to if the farmer had stayed spring calving,” Jake says. The data suggests seasonally specific mismatches between feed supply and feed demand. “What we saw over time was through the first winter period when the cows began the extended lactation, a lot of supplementary feed was needed as there wasn’t enough grass available to meet cow feed demand. Conversely, the first summer when they’re just about to be dried off, the cows’ feed demand was really low relative to the pasture supply. Through the decision rules of the trial, deferred grazing was chosen as an option for the herd. This is believed to have led to an unintended consequence of some cases of ryegrass staggers in the herd just before they started to calve.
Dairy Exporter | www.nzfarmlife.co.nz | December 2020
