Within all cattle production systems, veal calves are the most severely affected by abomasal damage, with current prevalence at slaughter ranging from 70 to 93% of all animals affected. Although most damage is found in the pyloric region of the abomasum, fundic lesions are also found. Despite past research into the etiology of abomasal damage and the many risk factors that have been proposed, consensus on the causal factors of abomasal damage in veal calves has not yet been reached. The aim of this review was to integrate and analyze available information on the etiology of, and possible risk factors for, abomasal damage in veal calves. We describe various proposed pathways through which risk factors may contribute to damage formation and conclude that the etiology of abomasal damage is most likely multifactorial, with diet being a main contributor. Pyloric lesions, the most common type of damage in veal calves, are likely the result of large and infrequent milk and solid feed meals, whereas fundic lesions may be caused by stress, although the evidence for this is inconclusive. Providing calves with multiple smaller milk and solid feed meals (or ad libitum provision) may decrease abomasal damage. In future research, ulcers, erosions, and scars as well as fundic and pyloric lesions should be recorded separately, because etiologies of these may differ. Further research is required to understand the exact pathway(s) by which milk replacer causes abomasal damage in veal calves; that is, whether low abomasal pH, overloading, or composition are important. Further research is also required to elucidate whether rapid intake of milk replacer and solid feed, which is influenced by restricted amounts fed, inter-calf competition, and calf breed, increases abomasal damage. Research is also needed into the effect of medication and nutrient deficiencies other than iron. The types of experimental designs that can be used for future research could be enhanced if a means to assess abomasal damage antemortem is developed. We conclude that it is unlikely that abomasal or ruminal hairballs, iron deficiency, water provision, and various infections and diseases are significant contributors to abomasal damage in veal calves.

Affective states can be inferred from responses to ambiguous and threatening stimuli, using Judgement Bias Tasks (JBTs) and Attention Bias Tasks (ABTs). We investigated the separate and interactive effects of personality and housing conditions on dairy cattle affective states. We assessed personality in 48 heifers using Open-Field, Novel-Object and Runway tests. Personality effects on responses to the JBT and to the ABT were examined when heifers were housed under reference conditions. Heifers were subsequently housed under positive or negative conditions, and housing effects on animal responses in both tasks were investigated while controlling for personality. A Principal Component Analysis revealed three personality traits labelled Activity, Fearfulness and Sociability. Under reference conditions, personality influenced heifers’ responses to the JBT and to the ABT, therefore questioning the tasks’ generalizability across individuals. Against expectations, housing did not influence responses to the  JBT and heifers in the negative conditions looked at the threat later than heifers in the positive or reference conditions. More research is warranted to confirm the validity and the repeatability of the JBT and of the ABT as appropriate measures of affective states in dairy cows.

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