Culling Quebec Holstein herds. 2. Study of phenotypic trends in reasons for disposal
1997
Durr, J.W. | Monardes, H.G. | Cue, R.I. | Philpot, J.C.
A total of 1 558 080 lactation records from PATLQ Holstein cows were used to describe the annual trends in reasons for disposal in Quebec dairy herds from 1981 to 1994. Differences in culling trends between official and owner sampler herds, between parities, and between Quebec agricultural regions were compared. Statistical analysis was carried out by means of a logistic regression model, and the significance of trends was tested by linear contrasts. Involuntary culling had a clearly ascending trend during the period of study (from 23% in 1981 to 32% in 1994), as opposed to culling for low production (voluntary), which had a descending trend (from 16% in 1981 to 4.5% in 1994). This increase in involuntary culling was mainly due to increasing trends in culling for reproductive problems, mastitis and feet and leg problems. Official herds had a greater proportion of cows with sale codes and fewer cows culled for mastitis than owner sampler herds, and the trend for sale codes was ascending for official and stable for owner sampler herds. Culling for low production was more intensive in first parity, but all parities showed a descending trend over time. The proportion of cows with sale codes decreased with parity number. For all involuntary reasons, proportion of cows culled increased with parity number.
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