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The nutritional demands of the immune system may result in tradeoffs with competing processes such as growth and reproduction. The magnitude of the nutritional costs of immunity is largely unknown. Thus, we examine the lysine content of the systemic components of the immune system in adult male chickens (Gallus gallus domesticus) in a healthy condition (maintenance) and following a robust Escherichia coli-specific immune response. Lysine was used as a metric, because it is found both in leukocytes and in protective proteins. The dynamics of subsets of leukocytes were monitored in primary and secondary immune tissues (thymus, bone marrow, and spleen) that would be expected to be involved in the response following iv injection of E. coli. The systemic immune system at maintenance has the same lysine content as 332 average-sized feathers, 16% of an egg, or 5.4% of a pectoralis muscle from an adult chicken. During the acute-phase response to E. coli, the additional lysine needed would equal 355 feathers, 17% of an egg, or 5.5% of a pectoralis muscle. The acute-phase proteins accounted for the greatest proportion of lysine in the immune system at maintenance and the proportion increased substantially during an acute-phase response. Hypertrophy of the liver required more lysine than all of the leukocytes and protective proteins that were produced during the acute-phase response. Size of the liver and levels of protein during the acute phase returned to normal during the time when the adaptive response began to utilize significant quantities of lysine. The catabolism would release a surfeit of lysine to provision the anabolic processes of the adaptive response, thus making proliferation of lymphocytes and production of immunoglobulins very cheap.

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Previous studies have shown that the inclusion of medium chain fatty acids (MCFA) results in an improvement in nursery pig performance. Therefore, the objective of this study was to evaluate a proprietary C8:C10 MCFA blend (CaptiSURE, Kemin Industries, Inc., Des Moines, IA) on nursery pig performance. A total of 360 weaned piglets (initial BW = 6.1 kg) were randomly assigned to a control (no MCFA blend) or 10 kg/t MCFA blend (10 pigs/pen, 18 replicate pens/treatment), in which MCFA blend was substituted at the expense of tallow at a 1:1 rate. Diets were manufactured in 3 dietary phases (d 0–7, 7–21, and 21–42) in pelleted form. Due to an unintended bacterial challenge at the sow farm, pigs were treated with amoxicillin using a pulse protocol (48 hrs on / 48 hrs off) from placement to d 21. Data were analyzed using the students T-test procedure, and pen served as the experimental unit. Within dietary phase 2 (d 7–21), the inclusion of MCFA blend improved ADG (264g vs 326g, P = 0.017) and G:F (0.79 vs 0.89, P = 0.005), while exhibiting a trend to improve ADFI (330g vs 364g, P = 0.080). Within dietary phase 3 (d 21–42), the inclusion of MCFA blend improved ADG (518g vs 581g, P = 0.024) and ADFI (719g vs 799g, P = 0.006). Overall (d 0–42), the inclusion of MCFA blend improved ADG (379g vs 438g, P = 0.007), ADFI (503g vs 0.562g, P = 0.009), and G:F (0.75 vs 0.78, P = 0.042), resulting in a 2 kg heavier pig (P = 0.043). In summary, the inclusion of a proprietary C8:C10 MCFA blend at 1.0% in nursery pig diets improved growth performance.