Increasing the ratio of SID lysine to metabolizable energy improves pig performance during a viral challenge

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) compromises pig performance. However, increasing standardized ileal digestible Lys per Mcal metabolizable energy (SID Lys:ME) above requirement has been shown to mitigate reduced performance seen during a porcine reproductive and respiratory syndrome (PRRS) virus challenge. The objective of this study was to evaluate the effects of increasing the dietary SID Lys:ME from 100% National Research Council (NRC) requirement to 120% of the requirement in vaccinated (vac+; modified live vaccine Ingelvac PRRS) and non-vaccinated (vac−; no PRRS vaccine) grower pigs subjected to a PRRSV challenge. In addition, the dietary formulation approach to achieve the 120% ratio by increasing Lys relative to energy (HL) or diluting energy in relation to Lys (LE) was evaluated. This allowed us to test the hypothesis that pigs undergoing a health challenge would have the ability to eat to their energy needs. Within vaccine status, 195 mixed-sex pigs, vac+ (35.2 ± 0.60 kg body weight [BW]) and vac− (35.2 ± 0.65 kg BW) were randomly allotted to one of three dietary treatments (2.67, 3.23, or 3.22 g SID Lys:ME) for a 42-d PRRS virus challenge study representing 100%, 120%, and 120% of NRC requirement, respectively. Pigs were randomly allotted across two barns, each containing 24 pens with 7 to 10 pigs per pen (8 pens per diet per vaccine status). On day post-inoculation 0, both barns were inoculated with PRRSV and started on experimental diets. Within vaccine status, weekly and overall challenge period pig performance were assessed. In both vac+ (P < 0.05) and vac− (P < 0.05) pigs, the HL and LE diets increased end BW and overall average daily gain (ADG) ADG compared with pigs fed the control diet (P < 0.05). Overall, average daily feed intake (ADFI) during the challenge period was greater (P < 0.05) for pigs fed the LE diet compared with pigs fed control and HL treatments, regardless of vaccine status (20% and 17% higher ADFI than the control in vac+ and vac− pigs, respectively). The HL vac+ pigs had the greatest gain to feed (G:F) compared with the control and LE pigs (0.438 vs. 0.394 and 0.391 kg/kg, respectively; P < 0.01). Feed efficiency was not impacted (P > 0.10) by treatment in the vac− pigs. In summary, PRRSV-challenged grower pigs consumed feed to meet their energy needs as indicated by the increase in ADFI when energy was diluted in the (LE) diet, compared with control pigs. In both PRRS vac+ and vac− pigs subsequently challenged with PRRSV, regardless of formulation approach, fed 120% SID Lys:ME diets resulted in enhanced overall growth performance.

Evaluation of dietary approaches to improve growth performance of health-challenged pigs

“…In pigs, feeding a high fiber diets normally has negative effects on voluntary feed intake, as high fiber diets decrease the rate of gastric emptying, thus contributing to earlier satiety (Kerr and Shurson, 2013). However, in the current study, similar to results reported by Jasper et al (2020), overall ADFI increased 8.6% in HF fed PRRSV challenged pigs (Exp. 1).…”

“…Lys intake), as reductions in ADFI are typically reported in PRRSV challenged pigs . The beneficial performance reported when increasing dietary Lys:ME in PRRSV challenged pigs has been further validated by our group (Jasper et al, 2020) utilizing two formulation approaches;…”

“…either increasing SID Lys via increased inclusion of SBM or by diluting ME via the inclusion of fine grade sand. Improved growth performance in PRRSV challenged pigs was observed irrespective of formulation approach used to achieve 120% Lys:ME (Jasper et al, 2020).…”

“…The impact and severity that PRRSV has on growth performance is influenced by factors such as pig age, duration of study, viral strain and viral clearance . Recently, nutritional strategies have been shown to augment pig growth performance during PRRSV challenges Schweer et al, 2018;Jasper et al, 2020). Herein, we further evaluated formulation approaches to increase SID Lys:ME in PRRSV and MHP challenged pigs to augment growth performance during a health-challenge.…”

“…Previous work from our group utilizing breakpoint analysis has reported that increasing SID Lys:ME to 110% to 120% above requirement resulted in improved growth performance and feed efficiency in grower pigs subject to a PRRSV challenge, while unchallenged pigs did not benefit from an increased ratio . This concept has been further validated in PRRSV challenged pigs, in which Jasper et al (2020)…”