|dc.description.abstract||The New Zealand dairy farm system is based on a seasonal calving interval with the
system being reliant on seasonal pasture production. A seasonal calving interval
requires all cows to reproduce every 365 days. Farmers typically experience difficulty
in achieving this 365 day cycle and hence the practice of induced parturition has been
widely used. Induced parturition has become internationally unacceptable and the New
Zealand dairy industry has set a target for <2% inductions in the national herd by 2010.
With reduction in the use of induced parturition as a tool, farmers require new strategies
to manage late conceiving cows.
The aim of this study was to identify management strategies which are being used by
farmers who are already achieving a compact calving spread, and acceptable
reproductive results under a nil induction policy.
The main factor identified in the scientific literature affecting the calving spread of a
herd, was the post-partum anoestrus interval which is largely affected by both body
condition and nutrition pre-partum. Other factors which affect the reproductive
performance of a cow or herd are their breed and genetic potential, post-partum disease
and reproductive tract disorders, and early embryonic mortality. However some of these
factors are themselves either the outcome of or influenced by farm and livestock
Eight farmers were interviewed to develop case study profiles of their farm and
management strategies. The case study farms all achieved a compact calving spread
with 90% of the herd calved in less than 8 weeks. Empty cow rates on the farms ranged
between 4 and 12% with no use of induced parturition. The studied farms ranged from 350 to 1,139 cows milked in peak, with stocking rates
ranging from 2.9 to 5 cows/ha. Seven of the farms were producing over 400 kg MS/cow
with a range from 256 to 500 kg MS/cow. Milksolids production per hectare ranged
from 1,180 to 1,600 kg MS/ha with all of the farms being above their district averages.
Livestock management appeared to be one of the key reasons for the farms achieving
their reproductive successes. These farms placed emphasis on animal health, cow body
condition and feeding. Cow body condition was monitored regularly by farm staff and
farm advisors, with all farms achieving a body condition score of 5 or greater at calving.
The incidence of reproductive tract disorders was low, as was the somatic cell count
(SCC) which ranged from 80,000 to 180,000 cells/ml compared with a national all year
average of 244,000 cells/ml. Pasture grazing residuals were monitored which was
reflected in the high level of milk production (kg MS/ha and kg MS/cow) being
achieved. However there appeared to be less monitoring of pre-grazing mass and
pasture growth rates. Feeding of cows during winter and of young stock was typically
on runoff ground and in 7 of the cases was controlled by the herd owner.
Farm advisors were widely used, particularly for feed budgeting and monitoring cow
body condition, along with nutrient budgeting. The advisors visited farms between 4
and 12 times annually.
It was apparent that there are issues with calculating and measuring the key
performance indicators used on farm, and particularly the empty rate and body
condition score of cows. The variation in calculating the empty rate appears to be due to
the range in management strategies used around pregnancy testing, while the variation
in body condition scoring is due to human variation.
Acceptable reproductive performance with nil inductions was achieved on these farms
by placing emphasis on animal health, monitoring body condition of cows and
achieving targets set, and by controlling the feeding of all stock classes throughout the