@article {3672,
	title = {Implications of using an extended lactation to change from a spring-calving to an autumncalving farm system in South Taranaki},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {80},
	year = {2020},
	month = {09/2020},
	pages = {143-149},
	address = {Online},
	abstract = {Recent changes to pasture-supply curves in South Taranaki, and the availability of winter milk premiums have increased farmer
interest in changing from a spring-calving to an autumn-calving farm system. One approach to changing the season of calving
from spring to autumn is to extend the calving interval (CI) by delaying the mating period by ~8 months, so that they next calve
in autumn and undertake an extended lactation [>305 days in milk (DIM)]. A large-scale farmlet experiment was established in
South Taranaki to investigate the production and reproduction responses of cows using this approach. In June 2017, 602 springcalving
cows were allocated to two farmlets. In one farmlet (SPR) 301 cows were mated in October to maintain a 12-month CI
spring-calving pattern. In the other farmlet (AUT, n=301 cows), mating was delayed for eight months, and cows underwent an
extended lactation (mean DIM, 488; max DIM, 577) to calve next in autumn 2019. The experiment analysed two lactations for the
AUT farmlet and two and a half lactations for the SPR farmlet. Across the total experimental period, milksolids (MS) production
was similar between farmlets (1,194 vs. 1,174 kg MS/cow), however, cows in the AUT farmlet were fed more supplementary feed
[2,371 vs. 1,951 kg dry matter (DM)/cow]. The extended lactation changed the relationship between feed supply and herd demand,
which led to excessive BCS gain and ryegrass staggers for AUT farmlet cows. Further research is required to examine grazing
management during extended lactations and to assess the economic implications of this approach.

Keywords: autumn calving; spring calving; extended lactation},
	issn = {1176-5283},
	author = {Jarman JWM and Kay JK and Neal M and Donaghy DJ and Tozer P}
}
