A case study investigating the effects of emergency vaccination with Brucella abortus A19 vaccine on a dairy farm undergoing an abortion outbreak in China

Table 5 Effects of brucellosis seropositivity and emergency vaccination with A19 vaccine on 305-day milk yield during 2017–2020

Year	Category levels	No. animals	305-day milk yield (Kg)				Statistics
Year	Category levels	No. animals	Median	IQR	Mean	SD	p value ^‡	p value ^§
2018	Seropositive	20	5185.0	4444.3, 5779.3	5215.3	1055.1	0.283	-
2018	Seronegative	56	5533.0	4730.3, 6308.5	5578.0	1234.7	0.283	-
2017	All lactating animals	122	5268.5	4899.8, 5778.3	5333.4	673.2	0.019	0.063
2018	All lactating animals ^†	150	5259.0	4728.8, 5887.8	5339.6	1014.2		0.035
2019	All lactating animals	152	5256.5	4724.3, 5857.8	5332.1	1002.4		0.033
2020	All lactating animals	110	5505.0	5018.3, 6239.3	5629.5	840.2		-

^†The difference between the total number of lactating animals and the total number of animals tested were caused by the removal of low milk yield and aborted animals before the sampling activity of December 2018
^‡Wilcoxon Rank Sum test for two groups, Kruskal–Wallis Rank Sum test for three or more groups
^§The Dunn’s test with Holm-Bonferroni correction (only comparisons between 2020 and other individual years were shown, and other comparisons were not significant)