Integrating Nutrition and Animal Welfare in Extensive Systems

Abstract

Extensive systems present herbivores multiple biotic and abiotic challenges such as temporal and spatial variation in the availability and quality of food and water, changes in the chemical and morphological defenses of plants, thermal stress, disease, predation, and competition. Due to variability in resource abundance and quality, food intake might not always satisfy their appetite or hunger. Animals can adapt by increasing their grazing time and/or by dispersing more widely. These changes in behaviour may improve the use of poor quality pastures, but may also have negative effects on productivity and welfare. For instance, poor pasture conditions lead to reductions in mating activity and reproductive performance, decrease the efficiency of behavioural strategies aimed at decreasing parasitic loads, and increase energetic costs. Thermoregulation has an energetic cost, which decreases animal production. However, a lack of exposure to thermal stress may not necessarily imply adequate animal welfare. Plant secondary compounds (PSC) can inhibit food digestion, increase metabolic costs, and potentially have toxic effects on animal tissues and metabolic processes, but at appropriate concentrations certain PSC may improve nutrition and immunity and alleviate some of the diseases that challenge herbivores in extensive systems. Predators have both a direct lethal impact on herbivores and indirect effects that challenge animal nutrition and welfare. They may restrict the use of high-quality habitats and increase the time invested in vigilance, which restricts foraging time. In contrast to this, facilitative interactions among animals with contrasting foraging strategies may positively impact on nutrition and welfare. In conclusion, some relationships between the variables described in this chapter (thermoregulation, PSC, animal–animal interactions) and welfare do not always vary in a uniform direction. Many of the challenges described in this chapter stem from variability and unpredictability of the environment, which is largely a function of natural—instead of managerial—influences. The challenge of managers is to provide the conditions and flexibility in their operations to allow animals to express their behaviour to cope with these challenges in a way that production and welfare are maximised within the constraints imposed by an ever-changing environment.