Factors associated with whole carcass condemnation rates in provincially-inspected abattoirs in Ontario 2001-2007: implications for food animal syndromic surveillance

Table 4 Univariable negative binomial models using GEE¹ approach

Covariate	IRR²	Robust Standard Error	P-value	95% CI
Animal class
Calves	---	---	---	---
Cows	4.83	1.35	< 0.001	2.80 - 8.34
Heifers	0.43	0.09	< 0.001	0.28 - 0.64
Steers	0.51	0.11	0.01	0.34 - 0.77
Year
2001	---	---	---	---
2002	1.02	0.14	0.90	0.77 - 1.34
2003	0.90	0.14	0.49	0.67 - 1.22
2004	0.70	0.15	0.10	0.46 - 1.06
2005	0.69	0.14	0.07	0.47 - 1.03
2006	0.75	0.16	0.17	0.50 - 1.13
2007	0.73	0.17	0.18	0.46 - 1.16
Season
Winter	---	---	---	---
Spring	0.94	0.05	0.20	0.85 - 1.03
Summer	0.86	0.06	0.02	0.76 - 0.98
Fall	0.76	0.07	0.01	0.64 - 0.91
³Audit rating
C	---	---	---	---
AAA	0.71	0.53	0.64	0.16 - 3.07
AA	0.90	0.37	0.80	0.40 - 2.01
A	1.19	0.48	0.67	0.54 - 2.61
B	1.01	0.42	0.98	0.45 - 2.28
unrated	2.69	1.09	0.01	1.22 - 5.94
# weeks open
1 - 43	---	---	---	---
44 - 49	0.72	0.15	0.10	0.48 - 1.08
50 - 51	0.71	0.16	0.13	0.46 - 1.11
52	0.92	0.29	0.78	0.49 - 1.70
# animal processed
1 - 286	---	---	---	---
287 - 498	1.01	0.15	0.95	0.75 - 1.35
499 - 841	1.14	0.19	0.44	0.82 - 1.58
842 - 27286	1.29	0.42	0.43	0.68 - 2.46
Region
Central	---	---	---	---
Eastern	9.88	6.83	0.01	2.55 - 38.26
Northern	3.78	2.49	0.04	1.04 - 13.74
Southern	7.91	6.56	0.01	1.56 - 40.21
Western	1.60	2.31	0.75	0.09 - 27.23
Price
Below median	---	---	---	---
Above median	1.11	0.06	0.04	1.00 - 1.23

¹ Generalized estimating equation using an exchangeable correlation structure to accommodate repeated measurements among provincial abattoirs
² Incidence rate ratio
³ Model would not converge therefore results represent univariable negative binomial model
Univariable negative binomial models using a GEE¹ approach modeling the association between condemnation rates in Ontario provincial abattoirs and animal class, year, season, audit rating, the number of weeks an abattoir was open each year, the number of cattle an abattoir processed each year, census agricultural region and median yearly sales-price for animal class.

ISSN: 1746-6148