Table 4.

Multivariable multi-level Poisson regression using “parasitic liver” condemnation rates

Variable	Categories	IRR1	Std. Err.	P-value		95% CI
Year	2001	—	—	—	—	—
	2002	1.08	0.04	0.08	0.99	1.17
	2003	1.73	0.04	< 0.01	1.60	1.88
	2004	1.81	0.04	< 0.01	1.67	1.96
	2005	2.06	0.04	< 0.01	1.90	2.24
	2006	2.29	0.04	< 0.01	2.12	2.49
	2007	1.71	0.04	< 0.01	1.57	1.86
Animal class	Calves	—	—	—	—	—
	Cows	1.00	0.06	1.00	0.89	1.13
	Heifers	1.45	0.05	< 0.01	1.30	1.60
	Steers	1.29	0.08	< 0.01	1.10	1.50
Season	Winter	—	—	—	—	—
	Spring	0.88	0.03	< 0.01	0.83	0.94
	Summer	1.08	0.03	< 0.01	1.02	1.14
	Fall	1.22	0.03	< 0.01	1.15	1.29
Region	Central	—	—	—	—	—
	Southern	0.49	0.18	< 0.01	0.35	0.69
	Western	0.61	0.18	< 0.01	0.43	0.86
	Northern	0.22	0.31	< 0.01	0.12	0.41
	Eastern	0.23	0.22	< 0.01	0.15	0.35
Rating	C	—	—	—	—	—
	AAA	0.53	0.13	< 0.01	0.41	0.69
	AA	0.72	0.09	< 0.01	0.60	0.85
	A	0.72	0.09	< 0.01	0.60	0.85
	B	0.74	0.09	< 0.01	0.62	0.88
	unrated	0.58	0.10	< 0.01	0.48	0.71
Season x animal class	Winter x calves	—	—	—	—	—
	Spring x heifers	1.04	0.04	0.37	0.96	1.12
	Summer x heifers	0.96	0.04	0.33	0.90	1.04
	Fall x heifers	0.90	0.04	0.00	0.84	0.97
	Spring x steers	0.96	0.04	0.30	0.90	1.03
	Summer x steers	0.89	0.03	< 0.01	0.84	0.95
	Fall x steers	0.95	0.03	0.11	0.89	1.01
	Spring x cows	1.13	0.04	< 0.01	1.05	1.21
	Summer x cows	0.87	0.04	< 0.01	0.81	0.93
	Fall x cows	0.75	0.03	< 0.01	0.70	0.80
Region x animal class	Central x calves	—	—	—	—	—
	South x heifers	1.90	0.05	< 0.01	1.71	2.10
	West x heifers	1.82	0.05	< 0.01	1.65	2.00
	North x heifers	2.96	0.17	< 0.01	2.11	4.15
	East x heifers	7.34	0.09	< 0.01	6.10	8.82
	South x steers	1.55	0.05	< 0.01	1.42	1.69
	West x steers	1.76	0.04	< 0.01	1.63	1.91
	North x steers	2.90	0.17	< 0.01	2.09	4.01
	East x steers	6.09	0.09	< 0.01	5.10	7.28
	South x cows	0.96	0.06	0.45	0.85	1.07
	West x cows	1.38	0.05	< 0.01	1.26	1.57
	North x cows	3.12	0.17	< 0.01	2.24	4.34
	East x cows	5.96	0.09	< 0.01	4.96	7.17
Year x animal class	2001 x calves	—	—	—	—	—
	2002 x heifers	0.88	0.06	0.02	0.79	0.98
	2003 x heifers	0.52	0.06	< 0.01	0.47	0.58
	2004 x heifers	0.57	0.05	< 0.01	0.51	0.63
	2005 x heifers	0.58	0.05	< 0.01	0.53	0.65
	2006 x heifers	0.55	0.05	< 0.01	0.50	0.61
	2007 x heifers	0.72	0.05	< 0.01	0.65	0.80
	2002 x steers	0.74	0.05	< 0.01	0.67	0.82
	2003 x steers	0.65	0.05	< 0.01	0.59	0.72
	2004 x steers	0.63	0.05	< 0.01	0.58	0.69
	2005 x steers	0.60	0.05	< 0.01	0.55	0.66
	2006 x steers	0.50	0.05	< 0.01	0.45	0.54
	2007 x steers	0.64	0.05	< 0.01	0.59	0.71
	2002 x cows	1.09	0.09	0.32	0.92	1.29
	2003 x cows	1.06	0.08	0.46	0.91	1.23
	2004 x cows	1.41	0.07	< 0.01	1.23	1.63
	2005 x cows	0.91	0.07	0.17	0.79	1.04
	2006 x cows	1.01	0.07	0.88	0.88	1.16
	2007 x cows	2.12	0.07	< 0.01	1.83	2.44

¹Incidence rate ratio.

Multivariable multi-level Poisson regression model (PQL-1) investigating the association between “parasitic liver” condemnation rates in Ontario provincial abattoirs and year-animal class interaction, season-animal class interaction, region-animal class interaction and audit rating.