Lactobacillus acidophilus fermentation product as an alternative to therapeutic zinc oxide in weaned pig diets on performance and response to Escherichia coli challenge

Previous research in pigs with chronic K88+ (F4) Escherichia coli has demonstrated that feeding Lactobacillus acidophilus fermentation product (LAFP; SynGenX^®, Diamond V, Cedar Rapids, IA, USA) at 1 kg/MT, in combination with carbadox and zinc oxide (ZnO) improves health and reduces the frequency of injectable treatments and mortalities (Probst Miller et al. 2016). Additionally, the combination of 1 kg/MT LAFP and oxytetracyline, or 2 kg/MT LAFP alone, has been shown to reduce E. coli in weaned pigs (An et al. 2015). Zinc oxide, fed at therapeutic levels, has been used to alleviate diarrhoea associated with weaning stress. However, concerns about the environmental impact of high inclusion levels of zinc, as well as the potential of zinc to drive antibiotic resistance in bacteria, may limit its use in the future. Therefore, we hypothesise that LAFP can aid in reducing the impact of E. coli on pig health and performance, demonstrating similar benefits as therapeutic levels of ZnO.

In the first of two studies, 288 piglets were weaned at 28 days (7.41 kg bodyweight (BW)) and randomly assigned to one of four dietary treatments (12 pens per treatment; three boars:three gilts per pen): Negative Control devoid of antibiotics (NC); Positive Control – NC + 3000 ppm ZnO (PC); NC + 1 kg/MT LAFP in pre-starter and 0.5 kg/MT LAFP in starter (LA1); and NC + 2 kg/MT LAFP in pre-starter and 1 kg/MT LAFP in starter (LA2). Diets were provided for 35 days (Pre-starter from weaning to 12 kg BW; Starter from 12 kg BW to the end of the study). Pigs and feeders were weighed on d 0, 7, 14, and 35 to determine BW, average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR). Data was analysed using Genstat 17 (VSN International, Hemel Hempstead, UK). In the first week post-weaning, a trend was observed in ADG and FCR in which PC had higher ADG and lower FCR than NC, with both LA1 and LA2 being intermediate. Significant improvements in ADG (P = 0.024) and FCR (P = 0.013) were observed using contrast comparisons between NC and the combination of LA1 and LA2. In the starter period (d 14 to d 34) and in the overall nursery period PC had higher ADG and final BW (P < 0.01) than NC and LA1, with LA2 being intermediate. Feed-to-gain was higher in NC compared to LA1 and LA2 combined (1.51 v. 1.44 g/g; P = 0.03) in starter period and in the overall nursery period (1.44 v. 1.36 g/g; P = 0.022). There were no differences in performance between PC and LA2 throughout the study.

In the second study, 48 piglets, 24 boars:24 gilts (Topigs Tempo x (Great Yorkshire x Finnish Landrace)), weaned at 26 days of age (7.1 kg BW) were allocated to four treatments: Negative Control devoid of antibiotics (NC2); Positive Control – NC2 + 2500 ppm ZnO (PC2); NC2 + 1 kg/MT LAFP (SG1); and NC2 + 2 kg/MT LAFP (SG2). Diets were offered to the piglets for 22 days. On d 10, piglets were orally challenged with 5 mL of 8.9 Log of nalidixine resistant E. coli. During d 11 to 15, 18, 20 and 22, faecal scores were measured (Gerritsen et al. 2012) and samples were collected to quantify nalidixine resistant E. coli and data was analysed using Genstat (17th edition). On d 14 (P = 0.064), 15 (P = 0.064) and 18 (P = 0.041), faecal E. coli excretion was lowest in boars fed SG2, with no differences between gilts and boars fed other diets. On d 20, pigs fed SG2 showed lower faecal excretion of E. coli than pigs fed with NC2, PC2 and SG1 (3.4 v. 4.3, 4.3 and 4.4 Log CFU/g faeces, respectively; P = 0.031). Overall faecal score was lowest for SG2 (P < 0.05). Pigs provided PC2 tended to have higher ADG (P = 0.053) compared with NC2 and SG1 (466 v. 359 and 385 g/d, respectively), with SG2 intermediate (406 g/d).

In summary, inclusion of ZnO at therapeutic levels improved performance compared to negative control fed animals. Feeding LAFP at 2 kg/MT resulted in performance comparable to therapeutic ZnO and additionally reduced faecal score and shedding of E. coli following challenge in diets that did not contain antibiotics or other additives. In conclusion, LAFP at 2 kg/MT may be a potential alternative for therapeutic ZnO in piglet diets post-weaning.