The impact of dietary crude protein level, fiber inclusion, and arginine supplementation on post-weaning pig performance and clinical response during enteric health challenges
Date
2024-12
Authors
Hagen, Chloe Sue
Major Professor
Advisor
Greiner, Laura L
Gabler, Nicholas
Burrough, Eric
Silva, Gustavo
Rosero, David
Committee Member
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Abstract
The weaning period is characterized as the most stressful time in a pig's life, often leading to post-weaning diarrhea (PWD). Enterotoxigenic Escherichia coli (ETEC) is a leading cause of PWD, resulting in secretory diarrhea, weight loss, morbidity, mortality, and significant economic losses. While antibiotics (e.g., carbadox) and zinc oxide (ZnO) can reduce the incidence of PWD and improve nursery pig performance, regulatory pressures to reduce their use drive the search for alternatives. Potential approaches include reducing the crude protein (CP) level of the early nursery diet, incorporating insoluble fiber to decrease pathogen proliferation in the intestinal tract, and supplementing dietary or water-based arginine (Arg) to support piglet growth and intestinal development. However, inconsistent reports on their benefits for pigs facing enteric challenges warrant further investigation. The overall objective of this dissertation was to evaluate the efficacy of three strategies as methods to manage nursery pig performance during enteric health challenges, focusing on their effects on growth performance, PWD, intestinal morphology, and pathogen shedding during enteric challenges. These strategies included: 1) low CP diets with subsequent reductions in standardized ileal digestible (SID) lysine (Lys), 2) inclusion of insoluble fiber (FIB), and 3) arginine (Arg) supplementation provided in feed and/or water.
To achieve this objective, three experiments were conducted using commercially sourced pigs with poor enteric health at the time of weaning with rotaviral infections. Two experiments then followed the natural rotavirus challenge with an ETEC F18 challenge (Chapters 2 and 4). The ETEC challenge bacteria isolate contained F18 fimbriae and expressed enterotoxins heat-labile toxin (LT), heat-stable toxin b (STb), and enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1). This isolate was inoculated at a dose of 6 mL per pig and approximately 5 x 108 CFU/mL. Scouring was observed within the first week post-weaning due to rotavirus, with Chapters 2 and 4 demonstrating resolution of rotavirus-induced diarrhea around 10 days post-weaning. In Chapter 2, inoculation with ETEC occurred for one day at 14 days post weaning, while in Chapter 4, inoculation was conducted over two days at 15- and 16-days post weaning. The challenge with ETEC resulted in peak scouring at three days post inoculation (DPI) in Chapter 2 and two DPI in Chapter 4. Both studies confirmed the shedding of ETEC genes F18 and STb after inoculation; however, ETEC inoculation did not lead to reductions in growth or increased mortality in either experiment
Results from Chapter 2 indicated no benefit from LCP or FIB diets for nursery pigs challenged with ETEC compared to the PC diet. The PC diet, which contained carbadox (55mg/kg) and ZnO (3,750 mg/kg), consistently reduced scouring both pre- and post-ETEC challenge and resulted in rapid shedding of ETEC, confirmed via qPCR. Neither the LCP nor FIB diet improved fecal consistency, and the LCP diet prolonged ETEC shedding. Chapter 3 investigated dietary and water-based Arg supplementation on piglet performance and intestinal integrity during a natural rotavirus outbreak. Increasing dietary SID Arg:Lys from 0.85 to 1.05 improved growth rates and final body weight after recovery from rotavirus, suggesting that SID Arg:Lys requirements may be higher than previously recommended. Water-based Arg supplementation, provided as an 8% stock solution dosed through a 1:128 proportioner for the first week post weaning, did not benefit growth performance or intestinal structure/permeability, as measured via the lactulose and mannitol dual-sugar absorption test. Chapter 4 combined the LCP dietary strategy from Chapter 2 with the water-based supplementation strategy from Chapter 3, supplying water for the first three weeks post weaning at levels of 8%, 6%, and 4% Arg stock for weeks one, two, and three, respectively. Lowering the CP level of the diet or supplementing Arg in the water did not reduce scouring pre- or post-ETEC challenge. However, water supplementation increased ileal villous height (VH) both pre- and post-ETEC challenge, and the LCP diet improved ileal VH pre-ETEC. Notably, the combination of LCP and water-based Arg supplementation prolonged ETEC shedding, without prolonging clinical signs. The LCP diet also reduced overall feed efficiency in Chapter 4, with increased villous atrophy observed following the ETEC challenge. Therefore, the lack of health improvements in response to ETEC F18 infection does not justify the growth performance reductions associated with the LCP diet. This dissertation demonstrated that increasing dietary SID Arg:Lys improves growth performance. However, reducing dietary CP and subsequently SID Lys, adding insoluble fiber, or using water-based Arg were not effective strategies for managing PWD caused by rotavirus or ETEC in the context of this research.
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dissertation