Table 3.

Manuscripts comparing Johne's disease (JD) across different durations of dam-calf contact¹

Study	Country	Breed2	Study design	Groups compared (length of dam- calf contact)	n (animals)	Number of herds	Diagnostic	Conclusion
Berghaus et al., 2005	United States	Not specified	Risk assessment questionnaire paired with clinical case reports (data from United States National Animal Health Monitoring System)	Frequency with which calves are permitted to nurse on farm (continuous variable)	Not applicable	815	(Clinical case reports)	Reports of clinical JD less likely in herds that allowed calves to nurse the dam	+
Collins et al., 1994	United States	Not specified	Latency to dam-calf separation evaluated as a risk factor and paired with results from cross-sectional blood samples	Separation time categorized as <1, 1 to 8, or >8 h	4,990	158	Serum ELISA	Herd MAP3 prevalence not associated with calf-dam separation time	=
Cetinkaya et al., 1997	England	Varied	Producers surveyed on duration of cow-calf contact in combination with an assessment of clinical case reports	Separation time categorized as 0, 1 to 10, or >10 d	Not applicable	2,9154	(Clinical case reports)	No association between disease risk and duration calves are kept with the dam	=
Johnson- Ifearulundu and Kaneene, 1998	United States	Not specified	Latency to dam-calf separation evaluated as a risk factor and paired with results from cross-sectional blood samples	Not specified (likely a continuous variable)	Not specified	121	Serum ELISA	Number of hours before dam-calf separation not associated with herd MAP infection status	=
Wells and Wagner, 2000	United States	Not specified	Data from United States National Animal Health Monitoring System assessed based upon latency to dam-calf separation	Separation time categorized as <24 or ≥24 h	32,622	1,004	Serum ELISA	Latency to cow-calf separation not associated with a current JD diagnosis	=
Ridge et al., 2005	Australia	Not specified	Latency to dam-calf separation evaluated as a risk factor in relation to results from the voluntary JD testing program	Separation time categorized as <12, 12–24, or >24 h	Cows >2 yr tested annually	54	Unspecified ELISA	Time before calf removal had no relationship to JD control	=
Ansari- Lari et al., 2009	Iran	HF and HF crossbreeds	Risk factors for MAP-positive bulk tanks evaluated, including whether the calf spent ≥3 h with the dam	Separation time categorized as <3 or ≥3 h	Not specified	110	Bulk-milk PCR	No association between herd infection status and calves spending ≥3 h with dam PR (95% CI)5 = 0.91 (0.13–6.33)	=
Dieguez et al., 2008	Spain	HF	Latency to dam-calf separation evaluated as a risk factor and paired with results from cross-sectional blood samples	Separation time categorized as before or after colostrum feeding	5,528	101	Serum ELISA	Separating the calf after colostrum feeding not associated with herd infection status PR (95% CI) = 0.79 (0.13–4.94) (“positive” and “highly positive” herds considered together)	=
Tavornpanich et al., 2008	United States	HF and Jersey	Early separation of calf and dam evaluated based upon whether herds had a high MAP prevalence	Separation time categorized as 1 to 6 vs. >6 h	1,260	21	Serum ELISA	Late calf separation not associated with high MAP prevalence PR (95% CI) = 0.57 (0.16–2.06)	=
Norton et al., 2009	New Zealand	HF and Jersey6	Average duration of dam-calf contact evaluated in relation to self-reports of clinical JD	Separation time categorized as <12, 12 to 24, or >24 h (not specified if categories were used in analysis)	Not applicable	427	(Clinical case reports)	Average duration of dam-calf contact not associated with incidence of clinical JD	=
Correia-Gomes et al., 2010	Portugal	Not specified	Latency to dam-calf separation evaluated as a risk factor of herd MAP status	Separation time categorized as ≤ 6, 7 to 12, or >12 h	5,294	122	Milk ELISA	Hours cow and calf are together not associated with herd MAP status. Crude OR (95% CI)7 with ≤6 h as reference = 1.26 (0.72–2.21) for 7–12 h and 1.40 (0.50–3.93) for >12 h	=
Nielsen and Toft, 2011	Denmark	Not specified	Longitudinal (4.25 yr) blood samples analyzed alongside the practice of separating calves from high-risk dams within 2 h	Separation time categorized as ≤2 or >2 h	All lactating cows	97	Milk ELISA	Removal of calves from high risk dams not associated with decreased MAP prevalence	=
Donat et al., 2016	Germany	HF	Average latency of cow-calf separation evaluated as a risk factor and paired with data from longitudinal (5 yr) fecal sampling	Not specified	All cows	28	Fecal culture	Latency of cow-calf separation not associated with cumulative herd-level incidence of MAP shedders	=
Pillars et al., 2011	United States	HF and Jersey	Longitudinal (5 yr) blood and fecal samples analyzed and assessed relative to time spent with the dam (including nursing)	Risk scores (1–10) assigned based upon time spent with dam (<30 min to >24 h) and nursing the dam (never to always)	3,707	7	Serum ELISA, fecal culture, or both	Nursing and time spent with the dam were risk factors associated with JD positive cows at the univariable but not multivariable stage	−/=

¹Listed for each study are country, breed of cattle, study design, groups compared (in reference to length of cow-calf contact), total number of animals sampled, number of herds included, the diagnostic test implemented, and the authors' conclusion and direction of effect (with + signifying a beneficial effect of suckling or cow-calf contact, − signifying a negative effect, and = representing no difference. Studies are ordered by effect direction, then chronologically by year, then alphabetically within year).

²HF signifies that breed was reported as Holstein, Friesian, or Holstein-Friesian. This designation includes country-specific variants such as Danish Holstein.

³MAP = Mycobacterium avium ssp. paratuberculosis, the etiological agent of Johne's disease.

⁴Sample size obtained from Cetinkaya et al., 1998.

⁵PR (CI) = prevalence ratio (95% CI).

⁶Predominantly.

⁷OR (CI) = odds ratio (95% CI).