New Zealand Journal of Agricultural Research abstracts
Quantifying the effect of thermal environment on production traits
in three breeds of dairy cattle in New Zealand
J. R. Bryant1*
N. López-Villalobos1
J. E. Pryce2
C. W. Holmes1
D. L. Johnson2
1Institute of Veterinary, Animal and Biomedical Sciences
Massey University
Private Bag 11222
Palmerston North 4442, New Zealand
2Livestock Improvement Corporation
Private Bag 3016
Hamilton 3240, New Zealand
*Present address: AgResearch Limited, Grasslands
Research Centre, Tennent Drive, Private Bag 11008, Palmerston North
4442, New Zealand. Jeremy.Bryant@agresearch.co.nz
Abstract In this study, the effects of hot and
cold conditions throughout New Zealand were assessed from 1990 to 2002
using daily milk yield, fat and protein concentration records from
19 201 spring calving first lactation cows comprising Holstein
Friesian (HF), New Zealand Jersey (NZJ) and crossbred ( ½
HF and ½ NZJ; HF × NZJ).
The effect of hot and cold conditions on test day records were assessed
using a 3-day average of temperature-humidity index (THI) and a 3-day
average cold stress index (CSI), which includes the effects of
temperature, rain and wind. Hot conditions were associated with
reductions in milk and milksolids yields, and fat and protein
concentrations in all breeds. Reductions greater than 10 g of
milksolids day–1 per unit increase in 3-day average THI,
started to occur at 3-day average THI of 68 in HF, 69 in
HF × NZJ,
and 75 in NZJ cattle. Temperature-humidity indices of 68 and 75 are
approximately equivalent to temperatures of 21 and 25.5°C,
respectively at 75% humidity. Fat and protein concentrations were also
reduced at high THI. There was also some evidence that HF cows of
high genetic merit, as determined by their estimated breeding value for
milk, exhibited greater milk yield reductions due to hot conditions
than their low genetic merit counterparts. Cold conditions
significantly reduced milksolids yields in HF and
HF × NZJ
cattle. However, the frequency of cold conditions where performance is
likely to be compromised is low (1–3% of days). Feed supply and feed
quality data for each herd test day would have improved the estimation
of 3-day average THI and CSI thresholds when performance was reduced.
Keywords cold; dairy cattle; Friesian; genetic
merit; heat; Jersey; thermal; weather
A06054; Online publication date 4 July 2007; Received 28 September
2007; accepted 22 May 2007
New Zealand Journal of Agricultural Research, 2007, Vol. 50:
327–338
0028–8233/07/5003–0327 © The Royal Society of New Zealand 2007
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