Table I.11.

Associations between herd size and mastitis; + = positive association: significantly more mastitis in larger herds (p < 0.05), − = negative association: significantly more mastitis in smaller herds (p < 0.05), ns = not significant

Country	System	n 1	Herd size, ø (range)	Variable	Analysis 2	Association	Reference
USA	Tie‐stall, loose housing	267	66	BACT: ≥ 50 cfu/mL Coliforms in BM	MA	ns	Cicconi‐Hogan et al. (2013)
				BACT: S. aur. in BM	MA	ns
CAN	Loose housing, tie‐stall	372	84 (76–92)	BACT: S.aur. in BM	MA	ns	Bauman et al. (2018)
AT	Tie‐stall, loose housing	208	26.9 (8–94)	CM: acute or chronic/cow & year	MA	ns	Firth et al. (2019)
USA	Cubicle, straw yard, pasture or dry lot, tie‐stall	292	Only give in categories	CM: CM per 305 cow‐days	MA	ns	Richert et al. (2013)
CAN	Cubicle, straw yard, tie‐stall	59	65 (18–220)	CM: CM/100 cow years at risk	MA	ns	Levison et al. (2016)
IT	Tie‐stall, cubicle	41	12	CM: medical dry‐off	MA	ns	Zanon et al. (2021)
				CM: medical treated CM	MA	+
CH	Loose housing	46	27 (10–48)	SCC: % from < 100 to > 200	UA/MA	+/ns	Ivemeyer et al. (2011)
				SCC: %quarters SCC > 100	UA/MA	+/ns
CAN	Loose housing, tie‐stall	1,062	77 (72–82)	SCC: gBMSCC	UA	ns	Bauman et al. (2018)
NO	Cubicle, tie‐stall	812	27	SCC: gBMSCC	MA	+	Simensen et al. (2010)
FI	Tie‐stall, cubicle	7,640	only give in categories	SCC: mean herd SCC	MA	+	Hiitio et al. (2017)
				SCC: SCC ≥ 200 in ≥ 1 of 4 test days	MA	+
				SCC: SCC ≥ 200 in ≥ 3 of 4 test days	MA	+

¹Number of farms.

²Statistical analysis: MA = multivariable analysis, UA = univariable analysis.