Results

4.4.1 General management

Neither the size of the dairy nor the specific tools used to improve the health status of calves (i. e., vaccinations, vitamin and iron supplementation, BHV-1 and BVD- status) significantly affected the incidence of CS. Interestingly, on farms struggling with CS, less time was invested in the observation of and care for the calves compared to the noCS farms (p=0.05). While the place of calving did not reveal any effect, there was a statistical trend that, on farms struggling with nCS, calves were less frequently separated from the dam within one hour compared to farms where CS was not a problem (p=0.08) (Table 1).

4.4.2 Calves in the first and the second weeks of life

On all farms, colostrum was fed to calves within the first hours of life according to the recommendations. However, a significantly higher proportion of farms without CS fed more colostrum at the first feeding and during the first day of life compared to farms where CS was a problem later (p=0.01). The difference between noCS farms and nCS farms was also significant (p=0.04) (Table 2).

Teat buckets were used on almost all farms to feed the calves with no obvious differ-ences between noCS and CS farms. There was no evidence that the type of feed (whole milk vs. milk replacer) affected the occurrence of CS. However, feeding of larger quantities of milk or milk replacer reduced the probability of CS (noCS vs. CS:

p=0.03; noCS vs. nCS: p=0.04).

Moreover, on farms without incidences of cross-sucking (noCS), calves had access to drinking water more frequently from the first day of life than on farms with CS (noCS vs. CS: p=0.03; noCS vs. nnCS: p=0.05).

Neither the type of housing nor environmental factors, such as light, air quality and the hygiene of calf pens, revealed significant effects on the probability of CS.

4.4.3 Calves aged 3-10 weeks

The time at which calves were grouped together after initially being in individual housing did not affect the incidence of CS (Table 3). At most, farms with nCS had more frequent groups of calves with a small age range compared to farms without CS (p=0.05).

The type and quality of milk did not significantly differ among the farm categories.

However, on farms with CS, calves were fed lower quantities of milk per day more frequently than on farms without any cross-sucking (noCS vs. CS: p=0.03). The comparison of nCS- and noCS farms was particularly striking (Table 3; noCS vs.

nCS: p=0.01). A higher proportion of farms without CS (noCS) fed calves milk for a longer period of time than those with the problem (Table 3; noCS vs. CS: p=0.008).

There was no evidence that the availability of water, roughage and concentrate had significant effects on the incidence of CS.

The type of housing and environmental factors (air and light) did not differ among the groups. However, environmental stimuli, such as toys (balls, twigs) or water-filled teat buckets to combat boredom were offered more often on farms with predominant nCS than on farms with predominant nnCS (p=0.01). Compared to farms without cross-sucking, poor litter quality was found more often on farms with predominantly non-nutritive cross-sucking (noCS vs. nnCS: p=0.02).

On farms without CS, abundant space for calves was more frequently available than on the other farms; this difference was particularly evident with respect to farms with predominant nnCS (noCS vs. CS: p=0.02; noCS vs. nnCS: p=0.004).

With respect to dehorning, calves from farms with predominant nnCS were dehorned more often before the fifth week of life than calves from farms with predominantly nu-tritive cross-sucking (p=0.006).

4.4.4 Weaned calves

As in calves of younger ages, no significant effects of the water supply and solid feeding at an older age revealed significant effects on the incidence of CS (Table 4).

Farms whose calves predominantly performed nnCS were often found to have better lighting conditions than farms with predominantly nCS (p=0.04). Additionally, com-pared to farms without CS, the air of farms with predominantly nCS was more fre-quently enriched with ammonia (noCS vs. nCS: p=0.05). Further effects of housing conditions such as climate, type of flooring or environmental stimuli were not found.

Farms without CS, however, more often had clean straw than farms with CS (noCS vs. CS: p=0.03) (Table 4).

With respect to stocking density, significant differences were also found in this age group. Compared to farms with CS, the available space per animal was significantly higher in farms without CS (noCS vs. CS: p=0.009). This difference was mainly due to farms with predominant nnCS (noCS vs. nnCS: p=0.01; noCS vs. nCS: p=0.06).

4.4.5 Blood samples

4.4.5.1 Individually housed calves at an age of 1-2 weeks

The total protein concentration in the serum of calves from farms with predominant nnCS was significantly lower than that of calves from farms without CS (noCS vs.

nnCS p=0.02) or with predominantly nutritive cross-sucking (nCS vs. nnCS p=0.05).

In addition, significantly higher white blood cell counts were found among the calves from farms with predominant nnCS compared to farms without CS (noCS vs. nnCS:

p=0.03). The other tested blood parameters (red blood cells, hematocrit, hemoglobin,

platelets, urea and albumin) did not significantly differ among calves of the various farm categories (Table 5).

4.4.5.2 Group-housed calves

The blood of group-housed calves aged 2-4 months differed between the groups in respect to the selenium, vitamin A and vitamin E concentrations (Table 5). The blood from calves that performed CS showed significantly higher selenium levels than that from calves with no problems (noCS vs. nCS p=0.01; noCS vs. nnCS p<0.001). In contrast, calves from farms that did not have a cross-sucking problem showed higher vitamin A concentrations than calves from farms with predominantly nutritive or non-nutritive cross-sucking. The vitamin E concentration differed only in farms without and those that displayed predominantly non-nutritive cross-sucking; blood from calves with no problems had a significantly higher vitamin E concentration than blood from calves that exhibited predominantly non-nutritive cross-sucking (noCS vs. nnCS p=0.03) (Table 5).