On-farm factors associated with cross-sucking in group-housed organic Simmental dairy calves

In EU organic dairy farming, group housing of calves is required after the first week. Especially in Simmental herds, this is perceived as a risk factor for cross-sucking (CS), i.e. sucking the udder-region or the scrotal area or any other body part of another calf, which may reflect frustrated motivation, lead e.g. to umbilical infections or be continued after weaning. Therefore, this study aimed at identifying factors associated with cross-sucking to provide farmers with effective preventive measures and to investigate potential relations of cross-sucking with treatment incidences. During one-day visits data were collected by the same observer on 31 organic dairy farms with Simmental cattle. The visits included 90 min of direct continuous behaviour observation starting at the morning milk meal, semi-structured interviews and analysis of treatment records (available from n = 25 farms). The average herd size was 31 10 cows (range: 17-59) and 11 7 calves (range: 3-37) with a mean of 4 2 calves per group (range: 2-8). Potential risk factors were screened using univariable analyses or Spearman rank correlation (inclusion threshold P < 0.2). General linear models with backward selection of factors were applied for final modelling. Associations between behaviour and health data were identified using Spearman rank correlation. CS was observed on 29 farms (94%) at a median rate of L66 (Q1 = 0.70, Q3 = 3.00) events/calf*hour. CS (explained variation 61.3%, Intercept = 2.75) decreased when age was similar within group (estimate = 2.40, p = 0.001) and increased when calves were not restrained during the milk meal (as compared with restraint for > 30 min; 1.46, p = 0.026). It was shown less frequently when use of nose-clips was not reported as a countermeasure (2.22, p = 0.008). Duration of sucking at teat buckets was negatively correlated with CS (0.23, p = 0.018) and the age at grouping had no significant effect on its occurrence. There were no significant correlations of cross-sucking and treatment incidences of diarrhoea, respiratory diseases and umbilical infections. This on-farm study comprising Simmental organic dairy herds partly confirms existing knowledge on preventive measures (e.g. homogenous age groups, long duration of sucking) to be applicable on-farm. Furthermore, it provides evidence that grouping after the first week of life is possible without an increased risk for cross-sucking. The perceived risk of cross-sucking leading to infections could not be proven, as most likely other factors are more relevant.