Meet BIOEPAR members for two conferences during the 25th edition of the 3R congress, on 2 and 3 December.  

Abstract: After being weaned, beef calves are transported to sorting centres, and grouped into batches of similar live weight for fattening. This practice aims to facilitate the feeding of young cattle and is expected to improve and homogenize their growth performance. However, it also leads to other practices affecting the welfare, health and performance of weaned calves. This study was carried out to identify such practices and quantify their impact on young bulls’ performance during the fattening period. The impact of batch characteristics on the growth and performance of young bulls indicated by their average daily gain (ADG) and fattening period duration was analysed using a dataset of 15,735 Charolais young bulls belonging to 740 different batches operated by the beef producers’ organization Ter’Elevage in 2014 and 2015. The transportation distance of the calves was negatively correlated with ADG (−11 g/d for each additional 120 km travelled), while weight homogeneity had no effect. Besides, the average weight in the batch and the proportion of animals vaccinated for bovine respiratory disease before batch creation were positively correlated with ADG. In the present study, the transportation distance was identified as an important factor affecting young bulls’ performance and is a factor on which it is possible to act. That is why we then developed an algorithm to minimize the transportation distance, without modifying the batch, the origin or the fattening farm of destination of young bulls but by selecting the sorting centre they should go through. We tested the efficiency of the algorithm using a dataset of 129,756 grazers sorted by Ter'Elevage into 9,383 batches via 13 different sorting centres between 2010 and 2018. The results showed a decrease in transportation distances of 29 km per calf on average, and 84 km per calf transported over more than 300km. In addition, the distribution of calves across sorting centres recommended by the algorithm differs significantly from the actual distribution, showing the relative usefulness of each sorting centre to reduce transportation distances. This study shows that it is possible for the beef cattle sector to reconsider which criteria should be used for batch constitution in particular thanks to decision support tools such as the present algorithm to improve the animal welfare, health and performance.

Abstract: The management of dairy calves on nurses developed in the field, particularly in Organic Agriculture, is increasingly widespread in France. However, it remains poorly documented. As this practice is associated with a phase of adoption by the nurse, preceded or not by a phase of artificial feeding, calves are exposed to a profound change in practice during the neonatal period which can have consequences on the epidemiology of diarrhoea, particularly cryptosporidiosis. The young heifers then graze with the nursing cows for several months and are thus brought into early and lasting contact with gastro-intestinal strongles (GIS). According to the farmers, this management is accompanied by better growth than standard management. The objectives of this study were therefore to evaluate the zootechnical performance as well as the parasitic risks linked to neonatal diarrhoea and GIS in calves reared under nurse. A follow-up was carried out in 20 farms carrying out this practice in 2019. Nineteen farms were located in the North-West of France (Brittany, Normandy, Pays de Loire) and the experimental farm of Mirecourt in the Grand-Est. Between January and September 2019, the farmers took faeces samples from all the calves on the farm at an age ranging from 3 to 21 days. A total of 611 samples were analysed. After a faeces smear was taken and stained, the excretion of Cryptosporidium sp. oocysts was assessed semi-quantitatively (score from 0 to 4 depending on the average number of oocysts seen on 20 microscopic fields). On average 40.2% of the calves excreted Cryptosporidium oocysts with an average score of 0.6 (25.5% with score 1, 9.5% with score 2, 2.6% with score 3 and 2.6% with score 4). Risk factors were highlighted concerning the calving period (mid or end of calving season vs. beginning of calving season, birth between January and July vs. birth in August-September), calf behaviour (calf with its mother in housing vs. in housing, going through an artificial suckling phase vs. calf with its mother only) and contact with other calves (including the presence of an excretory calf among the adopted calves). Concerning parasitism by IMS and the evolution of weights on pasture, the follow-up was carried out on 416 heifers. Blood and faecal matter samples were taken on 4 occasions: when the calves were put out to grass in June/July, in September and when they returned to the barn. On average, the heifers excreted 123 SGI eggs per gram of faeces (opg). The average level of serum pepsinogen, a marker of abomasum injury caused by Ostertagia, was 1282 milli tyrosine units (mUTyr). Ostertagia ELISA serologies indicating contact with SGI were performed (Mean Optical Density = 0.46). All these parasite indicators show a low parasite exposure despite a long grazing period (188 days on average) and an estimated recycling of infesting larvae up to the 4th larval generation (Parasit'Sim simulation software). These results suggest a protective effect of joint grazing of nurse cows with heifers against IMS. Concerning weight changes, the heifers had a high growth rate (on average 783 grams per day) during this first grazing season. Overall, the management of dairy calves under nurse cows seems to have a beneficial effect on the health and growth of the heifers throughout their first year of life.

Programme complet et modalités d'inscriptions sur le site du congrès: http://journees3r.fr/