It is widely recognized that feed represents a major component of the total cost of pork production. Therefore, feed intake (FI) and efficiency of lean growth are important components of the swine breeding objective and selection toward that objective may be enhanced by measurement of FI on individual pigs.  In the past, the most common method to record FI was to pen pigs individually. This method had several drawbacks: it does not reflect the group housing condition commonly found in production units, genotype by environmental interaction may affect the selection of superior genotypes, and it is labor intensive and expensive. The advent of electronic feeders allows for accurate measurement of individual feed intake, body weight and feeding patterns of group-housed pigs. If modeling the trajectory of daily feed intake (DFI) of individuals is of interest, repeated measurement analyses using covariance functions, random regression models or character process models using mixed model methodology may be most appropriate and practical. This approach requires that pigs be on a continuous feeding regime, which may not be feasible due to limited test capacity. However, if the purpose is to measure feed efficiency traits for the entire performance test period, alternating continuous and conventional group feeding can be considered in order to make optimal use of the number of feeders available.  Eissen et al. (1999), using complete data (feed intake records for each test day) and a first-order degree polynomial to estimate average daily feed intake (ADFI), concluded that biweekly deletions of DFI records did not greatly affect the accuracy of estimation.  Schulze et al. (2001), using records from pigs under either periodic or continuous electronic feeding, showed that biweekly periodic feeding underestimated DFI. In their study, the first period on test was always in the electronic feeder, which would not be possible in an all-in-all-out system. Another factor to be considered is how the data quantity and quality might affect the selection strategy chosen, since collecting high quality electronic FI data on a large number of animals is not a trivial task (Buttram, 2001). The objectives of the present study were to estimate the effects of biweekly alternating feeding on electronic and conventional feeders on data quality, accuracy of ADFI, and the relationship of ADFI with average daily gain (ADG) and feed conversion rate (FCR), with particular application to an allin, all-out testing system. The feeding strategies compared were switch feeding or biweekly switch from electronic to conventional feeders (S) and continuous feeding on electronic feeders (N). 

F. Grignola, A. C Clutter, D. S Casey, Jack CM Dekkers, X. Liu

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 10, , 10.12, 2002
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