Efficacy of a reduced protein diet on clinical expression of post-weaning diarrhoea and life-time performance after experimental challenge with an enterotoxigenic strain of Escherichia coli

Previous experiments have shown that feeding a reduced protein diet within the first 2 weeks post-weaning reduces gastrointestinal protein fermentation and clinical expression of post-weaning diarrhoea (PWD). However, growth of young pigs receiving a reduced protein diet without crystalline essential amino acids (CEAA) supplementation is depressed after weaning. It has been argued that the short-term performance reduction caused by feeding a reduced protein diet would be compensated and the lifetime performance of pigs would not be affected. An experiment was therefore conducted to examine PWD and lifetime growth of pigs after feeding a reduced protein diet without and with CEAA supplementation for 2 weeks after weaning. Two hundred individually housed pigs weaned at 21 d of age (Large White x Landrace, castrate:female ratio of 1:1, mean +/- SEM body weight of 5.5 +/- 0.05 kg) were stratified to one of four dietary treatments (n = 50): High protein + antimicrobial compound diet (HP + AMC, 230g crude protein (CP) with 2.5g lincospectin and 3 g zinc oxide per kg feed), High protein diet (HP, 230 g CP/kg), Reduced protein + amino acid supplemented diet (RP + AA, 185 g CP/kg with added CEAA up to HP level), and Reduced protein diet (RP, 185g CP/kg without CEAA supplementation). Pigs were fed the experimental diet for 2 weeks and then all pigs were fed the same series of commercial diets until slaughter. All pigs were experimentally infected with an enterotoxigenic strain of E. coli (6 and 10 mL of 1.9 x 10(9) cfu/mL, serotype 0149:K91:K88) at 72, and 96 h after weaning. Infection increased plasma haptoglobin levels (P<0.01) and faecal shedding of beta-haemolytic E. coli on days 5, 7, and 9 after weaning (P<0.001). Pigs fed the HP diet showed an increased faecal score (P<0.05-0.001), diarrhoea index (P<0.001), and mean number of therapeutic antibiotic treatments (P<0.001) compared with pigs fed other diets. Pigs fed the RP diet grew less (P<0.001), tended to eat less (P=0.063), and utilised the feed less efficiently (P<0.001) in the 2nd week post-weaning. When pigs fed an identical commercial diet on week 3, however, performance indices were not different between treatments. Lifetime performance was not affected by the dietary treatment (P>0.05). Carcass characteristics were not affected (P>0.05) by the treatments. The results indicate that although feeding a RP diet without CEAA supplementation decreased performance after weaning, it did not influence lifetime performance or carcass characteristics and reduced the clinical expression of PWD. (C) 2011 Elsevier By. All rights reserved.