Pasture-based fattening does not cause severe nonperforating lesions in veal calves of dairy breeds

Abomasal damage is a known health issue in intensive veal production and is associated with improper housing and feeding. Grass-based veal production could be an improvement, as access to pasture allows the expression of natural behaviors, such as species-specific foraging, and thus can contribute to calf welfare. However, data on the abomasal health of grazed calves have not yet been reported. As feed composition can affect the severity of mucosal damage, we compared the abomasa of calves that grazed on 2 swards with different plant composition. From 2018 to 2020, 111 calves of 2 dairy breeds, German Holstein and Jersey, were kept in whole-day strip grazing on these swards. Calves were sampled regularly for intestinal parasites and anthelmintic drug use was recorded. The animals were slaughtered at an age of 32 ± 2 wk (mean ± standard deviation) after individually varying grazing periods of 75 ± 22 d. After slaughter, dissection revealed that 104 of the 111 abomasa displayed low-grade nonperforating lesions, which were primarily located in the pyloric part. A more severe nonperforating lesion was registered in one calf only. In 46 abomasa, we observed diffuse inflammation. This inflammation was characterized by normal mucosal rugae but with slight discoloration that varied in the degree of redness and proliferation of the mucosa. Sward composition and breed did not affect the occurrence of abomasal lesions, but treatment with anthelmintics was negatively correlated with diffuse inflammation. Compared with the abomasa of calves fed under intensive conditions, the abomasa of calves kept on pasture in this study were not as severely altered, but completely unaffected abomasa were rarely observed either. This raises the question to what extent the observed changes in the abomasum were caused by husbandry and feeding conditions or whether they correspond to the normal condition of grazing animals