Survey of abomasal lesions in slaughtered veal calves

Abstract: For many years, abomasal lesions have been recognized as one of the most common pathological findings in veal calves. In particular, ulcerations have been associated with the consumption of large volumes of milk replacer and with psychosomatic stressors, such as long lasting transport, confinement in individual pens, limited space allowance, repeated group mixing. In recent decades new European regulations have been adopted to improve the welfare of calves confined for intensive rearing and fattening. With regards to the feeding system, the regulations state that “a minimum daily ration of fibrous food should be provided for each calf over two weeks old the quantity being raised from 50 g to 250 g per day for calves from eight to 20 weeks old”. In relation to roughage supply there have been some concerns that this might induce abomasal lesions. The purpose of this study was, therefore, to investigate the incidence of abomasal lesions in veal calves reared and fed in conformity with the new rules. The mucosal surface of the abomasa of 682 veal calves six to eight months of age (85.5% Holstein; 93.5 % male) were examined post mortem at slaughter. The calves originated from farms with a loose housing system. Their diet was based on milk replacer and an adequate amount of fibrous food (mais silage and/or mais grain) in accordance with the aforementioned regulation. Pathological aspects were found in 594 out of the 682 abomasa examined (87.1 %). The following lesions were recorded: generalized edema (41 = 6.0 %), hyperemia (120 = 17.6 %), petecchial hemorrhages (180 = 26.4 %), erosions (241 = 35.3 %) and ulcers (227 = 33.3 %). In another 67 cases, the abomasa showed the presence of small superficial whitish nodules ranging from one to three millimetres, disseminated throughout the gastric mucosal surface. Histologically, this type of lesions was characterized by edematose infiltration of the mucosal lamina propria and submucosal layer, possibly due to a not better clarified immune-reactive process. In all cases, the presence of indigested fibrous particles and hairs was observed. Hairs were often embedded in the mucosa. The results of this study confirmed that abomasal lesions still constitute a common finding in veal calves, with erosion (superficial defect of the mucosa) and ulcers (deep defect with clear loss of mucosa with muscularis mucosae involvement) being the most important. Although it is likely that most of them are innocuous to the animal, they demonstrate that this type of rearing/feeding system cannot as yet be considered completely innocuous to the gastrointestinal tract of calves. Whether or not the mechanical abrasive effect of rough particles as well as hair, rather than some other stress-induced biochemical imbalances at the level of the mucosa, plays the most important role in inducing abomasal lesions should be the object of further investigations.