A longitudinal study of serological responses to Coxiella burnetii and shedding at kidding among intensively-managed goats supports early use of vaccines

Table 4 Multivariable linear regression analysis of the effect of seroconversions to C. burnetii on goat weights.

Model	Variable	Levels	n	Coef.	SE (coef.)	p value	95% CI of Coef.
Effect of seroconversion on weight at weaning^a	Cohort	Cohort 2	49	−4.84	0.88	< 0.001	−6.61, −3.08
	Cohort	Cohort 1	13	0.00 (ref)
	Sex	Male	4	3.64	1.46	0.016	0.71, 6.56
	Sex	Female	58	0.00 (ref)
	Time of first seroconversion	After 28 weeks	10	−0.33	1.00	0.740	−1.03, 2.35
		10–28 weeks	17	0.66	0.84	0.435	−2.36, 1.66
		0–10 weeks	35	0.00 (ref)
	Intercept	–	–	17.71	0.89	< 0.001	15.93, 19.48
Effect of seroconversion on weaning to breeding weight change^b	Cohort	Cohort 2	38	5.27	1.41	0.001	2.43, 8.11
	Cohort	Cohort 1	12	0.00 (ref)
	Time of first seroconversion	After 28 weeks	3	0.98	2.52	0.700	−4.09, 6.04
		10–28 weeks	16	−0.60	1.31	0.652	−3.23, 2.04
		0–10 weeks	31	0.00 (ref)
	Intercept	–	–	7.67	1.40	< 0.001	4.86, 10.49

Interpretation: ^a No statistically significant difference in weaning weight was observed between goats that seroconverted before breeding and those that seroconverted post-breeding after adjusting for cohort and sex. However, goats in cohort 2 had weighed 4.84 kg lower at weaning than goats in cohort 1
^bSimilarly, no statistically significant difference in weaning-breeding weight change was observed between goats that seroconverted before breeding and those that seroconverted post-breeding after adjusting for cohort. Surprisingly, goats in cohort 2 weighed 5.27 kg more than goats that had not seroconverted by breeding. Sex was not included in model^b because all male animals were lost from the study by breeding time

ISSN: 1297-9716