STRATEGIES TO OPTIMIZE THE PRODUCTIVE PERFORMANCE OF BEEF CATTLE

The strategies to optimize the meat production process are mainly aimed at maximizing growth performance, reducing in this way the days on feed needed to achieve the slaughtering time. These strategies can be grouped into three categories: develop a proper diet to the needs of different types of animals in the different stages of production as well as the objectives of the farmer, improve the farm environment and therefore animal welfare, improve animal health. This PhD dissertation discussed and evaluated strategies to optimize the productive performance of beef cattle improving animal health condition, reducing morbidity and assess the risk to plan preventive approaches. Work 1 Respiratory Disease (BRD) is the main health problem in intensive beef cattle rearing. BRD is a multifactorial syndrome, and its etiopathogenesis is influenced by several predisposing and triggering factors. Management of the numerous risk factors is essential to maintaining appropriate preventative and therapeutic practices in the rearing of feedlot cattle. Because of the many stresses and the inevitable exposure to pathogens, incidences of BRD may be limited, but not avoided entirely. We propose a system for evaluating the potential risk of BRD for each new delivery of feedlot cattle, using a point attribution system that scores the principal risk factors of the production system, which is in turn able to judge the susceptibility of the animals to respiratory disease. The comprehensive risk assessment begins with an assessment of subject inherent risk in relation to weight, sex, race, transport length, transportation shrink, and the management practices of the breeding farm, which can be exacerbated or reduced by the management practices and structures present at the fattening facility. The analysis of risk allows for the focused management of each newly received lot of cattle in relation to its probable incidence and severity of BRD, providing the basic conditions for effective prevention and management of respiratory disease in the rearing of fattening cattle. Analysis of the data generated by the risk assessment system allows the quantification of the impact of each risk factor on the farm balance sheet, highlighting the cost-effectiveness of changes to management practices and investments in structural equipment. Work 2 Lameness is one of the main health and economic issues concerning not only dairy but even beef cattle production system. Lameness is a clinical condition in case of locomotor apparatus diseases (LAD) and is characterized by multiple triggering (microbial, mechanical, nutritional, and genetic) and predisposing factors (subjective and environmental). The aim of this work was to review the lameness causes and risk factors of beef cattle reared in the intensive system and in particular in the Italian situation. The results of the surveys proposed, show that in Italian intensive beef cattle rearing, LAD is an important problem characterized by variable incidence and different risk factors. Heavy Charolaise bullocks are more predisposed to LAD. Floor is one of the main risk factor, but the right choice of which animal will be housed on slatted floor can strongly limit arthropathies incidence and a proper litter management can prevent foot diseases. Other livestock facilities and management can limit or promote LAD incidence and severity. Furthermore even feed quality control, a proper vitamins and minerals integration and the gradual transition from arrival to finishing diet, limit acidosis events and then laminitis. The right diagnosis and the knowledge of the main features related to LAD can help and speed up the decision-making process not only about the fate of a specific lame animal but also to identify the cause behind of a widespread problem in the herd. In this way, can be adopted specific preventing strategies in order to limit drugs administration, not essential in every case of lameness. Work 3 The effects on health and growth performance of two different sources of selenium administered to newly received beef cattle were evaluated in a 54 days field trial. 228 Limousine x Charolaise crossbreed bullocks (average age: 13 ± 1 months; live weight: 374.84 ± 29.43 kg) imported from France to an Italian fattening unit were enrolled in the study and monitored for the entire adaptation phase. At arrival, animals were vaccinated, treated for internal and external parasites and received a preventive antibiotic mass treatment because considered at high risk to develop respiratory diseases. Animals were housed on concrete floor covered by straw litter and provided ad libitum access to water, hay for the first 5 days and a specific adaptation diet formulated to meet or exceed nutritional requirements. Experimental groups diets were different only with regard to mineral and vitamin mix that were formulated with the aim to provide 3 mg of selenium per day from different sources (Control: sodium selenite (NaSe); Treatment: selenised yeast (Se-Y)). At experimental days 0, 19 and 54, animals were weighted individually to evaluate ADG, and blood samples were collected to evaluate serum selenium content, neutralizing antibody levels, serum bactericidal activity and total antiradical activity of whole blood and red blood cells. Treatment positively affected serum selenium content proving that organic sources of this trace mineral are characterized by higher bio-availability. Se-Y supplemented bullocks have greater ADG as a consequence of a lower incidence of respiratory diseases (BRD). BRD affected animals in Se-Y sub-group had a better recover after illness period since their ADG was higher than in Na-Sa supplemented sick animals. The higher level of circulating selenium since the first days after arrival have led Se-Y bullocks to a better recover after transport stress. Se-Y group has a better immune-reaction after exposure to the vaccinal antigen and higher blood total antiradical activity. In the present experimental condition, the supplementation of 3 mg of selenium from organic source respect inorganic one, led to the improvement of immunity and antioxidant ability of newly received beef cattle. The higher bio-availability of selenised yeast is likely able to help animals to better and quickly recover after transport stress and illness events. The improvement of immunity and antioxidant ability reduced BRD morbidity promoting better growing performance. Work 4 A 53-day field trial was performed to evaluate the effects of the essential oils of cinnamaldehyde, eugenol, and capsicum on the health status and growth performance of 45 Charolaise beef cattle (average arrival weight: 422.0 ± 29.3 kg; control: n = 21; treated: n = 24). Each animal was weighed, and blood samples were collected on days 0, 25, and 53. The average daily gain of the treated group was significantly higher (P<0.05) than that of the control. The treated group showed a significant increase in antibody for BHV-1 after vaccination (P<0.05 at day 25 and day 53) and significantly higher serum bactericidal activity (P=0.01). No differences between groups were observed for serum content of haptoglobin or reactive metabolites of oxygen. The observed improvement in growth performance and health status is due to the capacity of essential oils to optimize rumen fermentations, to increase dry matter intake, and probably to the positive interaction between essential oils and immune system components.