Herd-level risk factors for cow and calf on-farm mortality in Estonian dairy herds

Table 2 Results of multivariable negative binomial regression analysis for risk factors associated with within-herd calf (aged 21–90 days) mortality rate in years 2017–2018 in 209 Estonian dairy herds

Variable	Categories	n	IRR^a	95% confidence intervals	Category p-value	p-value
Herd size (centered) (number of cows^b)			1.02	1.01; 1.03		0.005
Square term of herd size (centered)			0.9997	0.9995; 0.9999		0.001
Herd proportion of stillbirths (%)			1.09	1.04; 1.14		< 0.001
Herd proportion of abortions (%)			1.22	1.09; 1.36		< 0.001
Region^c	Northeast	59	1			0.020
	Southeast	44	0.63	0.44; 0.90	0.013
	Southwest	71	1.10	0.79; 1.53	0.573
	Northwest	35	1.01	0.68; 1.52	0.946
Farmer attending trainings within the last 4 years	Once	48	1			0.008
	2–3 times	107	1.91	1.30; 2.81	0.001
	More than 3 times	31	1.34	0.83; 2.19	0.233
	No	23	1.09	0.57; 2.08	0.792
Prophylactic administration of vitamins to calves	No	70	1			0.041
	Sometimes	62	1.19	0.83; 1.69	0.337
	Yes (to more than 95% of calves)	77	1.48	1.09; 2.01	0.012
Housing of preweaned calves > 2 weeks of age	Group pen	168	1			0.020
	Single pen	18	1.17	0.67; 2.03	0.581
	Single and group pen	23	0.51	0.32; 0.83	0.007
Place of calving	Group pen	68	1			0.020
	Individual pen	41	0.83	0.59; 1.17	0.284
	Tiestall	84	1.13	0.79; 1.61	0.510
	Combined or other^d	16	0.40	0.20; 0.78	0.008

^aIncidence rate ratio
^bOne unit change is 20 cows
^cNortheast Estonia: Ida-Viru, Lääne-Viru, Jõgeva, Järva county; Southeast Estonia: Tartu, Valga, Võru, Põlva county; Southwest Estonia: Pärnu, Viljandi, Saare county; Northwest Estonia: Harju, Rapla, Lääne, Hiiu county
^dOther: calving on pasture and its combinations between other systems

ISSN: 1751-0147