Effects of Porcine Zona Pellucida Immunocontraception on Mare Body Condition and Foaling Season Length in Two Western Wild Horse Populations.

Birthdates in 2010–2011 were significantly later in treated than untreated mares, but the difference in SBD spread was not quite significant ( Figure 4 b; t = −3.24, df = 197, p = 0.001; Levene’s test of equal variances, F = 3.41, df = 1, 197, p = 0.066).

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