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Pigs exhibit variations in feed intake, growth rate, and nutrient utilization efficiency, influenced by genetic, physiological, and environmental factors. Intact males, for example, show lower voluntary feed intake and higher efficiency in protein deposition—and consequently, a higher lysine requirement—compared to females and barrows (Figure 1; Brazilian Tables for Poultry and Swine, 2024). Failure to account for these differences in feeding management can lead to under- or overfeeding, thereby compromising the production system's productive and economic performance.
Figure 1. Digestible lysine requirement by category (70–100 kg). Source: Brazilian Tables for Poultry and Swine, 2024.
As previously noted on several occasions, precision feeding is based on the principle that each animal has individual nutritional needs, which vary over time depending on growth, physiological state, health, and the environment. In practice, this means adjusting nutrient supply daily to the animal's actual requirements, avoiding the excesses and deficiencies common to phase-feeding systems.
Precision feeding uses data such as individual intake, body weight, and weight gain to estimate the daily nutritional requirements of each animal (Hauschild et al., 2010), allowing for continuous dietary adjustments and a reduction in nutrient waste released into the environment, particularly nitrogen and phosphorus. Growing pigs fed individually via precision feeding systems showed a 30% reduction in nitrogen excretion and feed costs compared to those kept in group-feeding systems, without compromising performance (Figure 2; Andretta et al., 2016). This effect stems from more precisely matching protein and mineral supply to actual requirements, thereby reducing the surplus that would otherwise be excreted as urinary nitrogen and fecal phosphorus.
Figure 2. Individual vs. group precision feeding, without compromising animal performance. Source: Andretta et al., 2016.
Another relevant aspect is the variability among animals within the same batch, resulting from factors such as health history, immune status, and gut microbiota composition. By accounting for these differences, precision feeding better aligns nutrient supply with each individual's requirements. For instance, in a batch of growing pigs (30–60 kg) with an estimated average requirement of 0.95% digestible lysine, animals with higher protein deposition potential may require around 1.05%, whereas those with lower potential need only 0.85%—a variation of ±10–15% relative to the mean (Hauschild et al., 2012). In a conventional system, however, all animals receive the same single diet.
Following ingestion, absorbed nutrients are directed toward multiple biological functions: growth, tissue deposition, maintenance of homeostasis, and immune response. Under stress conditions—such as health or thermal challenges—physiological priority is given to maintenance and bodily defense at the expense of productive functions (growth, milk production, and reproduction), as immune responses and stress-adaptation mechanisms increase the demand for energy and amino acids, alongside the energetic costs of thermoregulation and inflammation. This metabolic redirection partly explains the decline in performance observed when the diet fails to meet the animal's actual physiological needs, even when feed intake remains constant.
Amino acids play a central role in this process, as they are constituents of immune cells and participate in the synthesis of immunoglobulins, cytokines, and acute-phase proteins. Diets with higher amino acid intake tend to be more suitable for pigs facing health challenges; when provided with levels exceeding requirements for tryptophan, methionine, and threonine, supplemented animals exhibited feed efficiency that differed from that of non-supplemented animals (Figure 3; Valini et al., 2024). However, this response is not uniform across animals and depends on each individual's capacity to cope with the challenge. More "resistant" animals—possessing greater immunological and metabolic competence—allocate amino acids to both the immune response and productive functions, whereas more compromised animals prioritize maintenance and defense at the expense of production.
Figure 3. Feed efficiency under health challenge for animals supplemented with amino acid levels exceeding tryptophan, methionine, and threonine requirements, and for non-supplemented animals. Source: Valini et al., 2024.
In this context, precision feeding can continuously and individually adjust nutrient supply to the animals' varying physiological conditions (Hauschild et al., 2010), making feed provision more precise and economically viable, although the application of this concept to challenged animals requires further study.
Linking the animals' biological and physiological mechanisms with precision feeding systems enables nutritional adjustments that are more timely and aligned with individual variations, thereby contributing to greater feed efficiency, improved resource utilization, and enhanced sustainability of production systems.
