L.F.M. Heutinck

Prevalence of gastrointestinal disorders recorded at postmortem inspection in white veal calves and associated risk factors

The study aimed at assessing the prevalence of poor rumen development, presence of rumen plaques, rumen papillae hyperkeratinization, and abomasal lesions in veal calves and to investigate risk factors for their occurrence at the farm level. Within a wide cross-sectional study, a sample of 170 veal farms representative of the European veal meat production systems was considered in the 3 major producing countries (99 in the Netherlands, 47 in France, and 24 in Italy). An average of 59 ± 10 (SD) rumens and abomasa belonging to calves from a single batch per farm were inspected at the abattoir by trained observers to assess the incidence of these gastrointestinal disorders. Potential risk factors for their occurrence related to farm management, housing, and to the feeding plan were obtained by a questionnaire submitted to the stockperson. Prevalence of poor rumen development (almost no papillae present), rumen plaques, and hyperkeratinization were 60.4, 31.4, and 6.1% of rumens, respectively, whereas abomasal lesions in the pyloric area were recorded in 74.1% of abomasa. Independent variables related to the feeding system confirmed to be the main risk factors for the occurrence of gastrointestinal disorders in veal calves. However, additional risk sources for each given problem were identified among housing and management variables. The provision of a low amount of solid feed (≤ 50kg of dry matter/head per cycle) was a relevant risk for rumen underdevelopment. Rumen wall alterations (plaques and hyperkeratinization) and abomasal lesions were instead associated with the administration of large quantities of solids (151-300 kg of dry matter/head per cycle) in calves receiving milk replacer during the entire fattening cycle. Among the types of solid feed, cereal grain acted as a preventive measure for low rumen development, whereas it was a risk factor for the occurrence of rumen plaques, papillae hyperkeratinization, and abomasal lesions. Some housing and management options adopted to improve veal calf welfare (i.e., higher space allowance and use of heating) were associated with lower risk for gastrointestinal disorders.

Prevalence of respiratory disorders in veal calves and potential risk factors

The study aimed to assess the in vivo and postmortem prevalence of respiratory disorders in veal calves and investigate risk factors associated with them. A cross-sectional study was carried out in 174 farms in the 3 major veal meat-producing countries in Europe (50 in France, 100 in the Netherlands, and 24 in Italy). Trained veterinarians visually evaluated individual calves of 1 batch per farm at 3 and 13 wk after arrival and at 2 wk before slaughter to assess the prevalence of hampered respiration, nasal discharge, and coughing. A random sample of lungs belonging to calves of the same batch was monitored at the slaughterhouse for mild to moderate or severe signs of pneumonia, and presence of pleuritis. Data regarding veal calf housing, feeding, and management and specific characteristics of the batch were collected through an interview with the stockperson, and the potential of these as respiratory disease risk factors was assessed. Regardless of the stage of fattening, the prevalence of in vivo signs of respiratory disorders in calves was always <7%. This low prevalence was likely the outcome of the general implementation by veal producers of standardized practices such as prophylaxis, all-in/all-out, and individual daily checks of the calves, which are recognized tools for effective disease prevention and management. However, at postmortem inspection, 13.9% and 7.7% of lungs showed mild to moderate and severe signs of pneumonia, respectively, and 21.4% of the inspected lungs had pleuritis. Thus, even mild clinical signs of respiratory disorder in calves at specific time points during the fattening period may be associated with high prevalence of lungs with lesions at slaughter. Alternatively, clinical symptoms recorded during routine visual inspections of veal calves on-farm may be poor predictors of the true prevalence of respiratory disease in calves. Among all potential risk factors considered, those concerning the characteristics of the batch were predominant but factors related to housing, management and feeding equipment were also relevant. Different risk factors were involved at different stages of the fattening period. Therefore, to overcome respiratory disorders in veal calves, different solutions may apply to different stages of the fattening period.

The relationship between clinical signs of respiratory system disorders and lung lesions at slaughter in veal calves

The presence and severity of lung lesions recorded post-mortem is commonly used as an indicator to assess the prevalence of respiratory problems in batches of bovines. In the context of a welfare monitoring based on on-farm measures, the recording of clinical signs on calves at the farm would be more convenient than the recording of lung lesions at slaughter. The aim of the present study was to investigate the relationship between clinical respiratory signs at farm and post-mortem analyses of lung lesions observed at slaughter in veal calves. If clinical signs were a good predictor of lung lesions it could be possible to integrate only those measures in a welfare monitoring system. One-hundred-and-seventy-four batches of calves were observed 3 times: at 3 and 13 weeks after arrival of the calves at the unit and at 2 weeks before slaughter. For each batch a maximum of 300 calves was observed and the proportions of calves showing abnormal breathing, nasal discharge and coughing were recorded. Post-mortem inspection was carried out on a sample of lungs belonging to calves from the observed batches. Each examined lung was classified according to a 4-point scale for pneumonia from healthy lung (score 0) to severe lesions (score 3). The clinical signs recorded infra vitam were significantly correlated with moderate and severe lung lesions for observations at 13 weeks and 2 weeks before slaughter and the level of the correlation was highly variable (r(sp) from 0.16 to 0.40). Receiver operating characteristic (ROC) curves were created and the area under the curves showed that batches with a high proportion of lungs with moderate or severe lesions could not be accurately detected by the three clinical signs of respiratory disorders. These results suggest that both clinical signs and post-mortem inspection of lung lesions must be included in a welfare monitoring schemes for veal calves.

Effects of roughage source, amount, and particle size on behavior and gastrointestinal health of veal calves

The European Union 1997 Directive, stipulating that veal calves should be fed a minimum of 50 to 250 g of fibrous feed from 8 to 20 wk of age, is vague. A fibrous feed ration maximum of 250 g has been implicated in welfare issues, namely the occurrence of abnormal oral behaviors and poor gastrointestinal health. Past research suggests that this amount is insufficient to prevent the development of abnormal oral behaviors and enabling good rumen development. Different sources and particle sizes of roughage could lead to very different welfare outcomes. In a 3×2 × 2 factorial design, 240 group-housed calves (10±1 d; 46.1±0.1 kg) were fed different roughage sources (straw, maize silage, or maize cob silage; the latter 2 were dried and provided no extra moisture compared with straw) in 2 amounts (250 or 500 g of dry matter per day), and 2 particle sizes (chopped or ground). Roughage was supplemented to milk replacer (MR) from 2 wk after arrival. In addition, 60 calves were fed 1 of 3 additional control treatments: MR only (n=20), MR plus an iron supplement (n=20), or MR plus ad libitum hay (n=20). Oral behaviors were recorded using instantaneous scan sampling at 2-min intervals for 2 h in 3 periods per day, at 12 and 22 wk of age. Calves were slaughtered at 24 wk of age and rumen and abomasal health parameters were recorded. Limited provision of straw resulted in behavior comparable with that from unlimited provision of hay, with reduced tongue playing and oral manipulation of the environment, as well as increased chewing compared with diets with no roughage supplement. Straw prevented ruminal hairballs, but impaired rumen development and increased abomasal damage. A higher ration of roughage increased chewing (12 wk), decreased oral manipulation of the trough (12 and 22 wk) and the pen (22 wk), and increased rumen weight. However, more roughage led to increased abomasal damage for certain parameters. Longer feed particles had no obvious benefits for behavior, but decreased hairball prevalence. Overall, unlimited hay had the highest benefit for both behavior and gastrointestinal health. Adding iron to the MR did not alter behavior or gastrointestinal health compared with MR without iron supplement. This study demonstrated that different roughage sources, amounts, and particle sizes have different effects on veal calf behavior and gastrointestinal health, and hence on veal calf welfare.