Evaluation of sources of error in weight records of commercially raised growing pigs : a thesis presented in partial fulfillment of the requirements for the degree of Master of Veterinary Studies in Epidemiology at Massey University, Palmerston North, New Zealand
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Date
2008
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Massey University
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Abstract
The objective of this research was to investigate sources of errors in pig weight
measurements. Three studies were conducted using data from one commercial
New Zealand pig farm. In XChapter 4X, finisher pigs fed ad libitum or via a
computerized liquid feeding system were weighed four times a day over a fourday
period. Results showed that standardization of weighing time reduced diurnal
fluctuations in pig weight. However, multivariate analysis showed that there was a
significant interaction between day and time of day, which indicates that diurnal
fluctuations in live weight are not consistent between days, particularly in ad
libitum fed pigs. Hence, XChapter 5X investigated whether overnight feed
withdrawal for 11 hours (weaners) or 17 hours (growers and finishers) is effective
in reducing between-pig variation in live weight and growth rate. For grower and
finisher pigs, feed withdrawal was associated with a reduction in variability in live
weight and growth rate by up to 11.5%, whilst the effect was inconsistent in
weaner pigs. It is recommended to repeat the investigation on other farms to
assess long-term effects on pig performance before general recommendations can
be made.
XChapter 6X compared the magnitude of sampling error when sampling pens from
batches of pigs, using different sample sizes and sampling methods. Increasing the
portion of randomly selected pens reduced the sampling error, but in a
diminishing manner. Purposive selection of two pens reduced sampling error by
more than 64% compared with random sampling. However, purposive sampling
introduces the risk of obtaining biased estimates. Thus, it is recommended to
select pens from batches at random. These results may be used as an educational
tool to demonstrate how to minimize errors in pig weights. Collecting more
accurate weight records is likely to lead to improved interpretability of pig
weights, and may promote better use of production data.
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Keywords
Pigs, Pig weight, Pig feed