A study of nucleotides in weaning pigs challenged with Escherichia coli K88

Nucleotides have also been considered as an alternative to antibiotics (Sauer et al. 2011) and have been described to have positive effects on stimulation of systemic immunity (Nagafuchi et al. 1997), small intestinal growth (Domeneghini et al. 2004) and hepatic composition (Novak et al. 1994) in pigs. The objective of this study was to evaluate the effect of different level of nucleotides on growth performance, blood profiles, and faecal scores in weaning pigs challenged with Escherichia coli K88. It was hypothesised that different levels of nucleotides may have different effects on weaning pigs.

A total of 140 weaning pigs (Landrace × Yorkshire × Duroc mixed crossbred, n = 35) with an average initial body weight (BW) of 7.2 ± 0.33 kg (mean ± SD) was used in a 42-day feeding trial. Pigs were distributed to four treatments on the basis of BW and sex with five pigs/pen (three barrows and two gilts) and seven pens/treatment. Treatments were: Control (CON), corn-soybean meal diet; R150, CON + 150 mg/kg Rovimax NX (DSM Nutritional Products Philippines, Inc.); R220, CON + 220 mg/kg Rovimax NX; and R275, CON + 275 mg/kg Rovimax NX. According to the manufacturer’s fact sheet, experimental diets contained 0, 60, 88, and 110 mg/kg supplemented nucleotides. All diets were formulated to meet or exceed the nutrient requirements recommended by NRC (2012). On d 14 after weaning, two pens were selected from each group and orally dosed with 1.5 mL suspension containing 10¹⁰ colony forming units/ml of Escherichia coli K88. Twenty-four hours after E. coli K88 was dosed, blood was collected from two challenged pigs selected randomly per pen and centrifuged at 3000×g at 4°C for 15 min to prepare plasma for determination of cortisol, TNF-α, IGF-I, and IL-6. On d 42, the BW of each pig and food consumption per pen were measured to calculate average daily gain (ADG), average daily feed intake (ADFI) and gain to feed (G : F). On d 42, blood was collected from two pigs selected randomly per pen and centrifuged at 3000×g at 4°C for 15 min to prepare plasma for IgA and IgM. To assess the faecal score after challenge, faeces from each pig were scored on d 21, 28, 35, and 42 by determining the moisture content, and scored from 1 to 5: 1 = hard faeces, 2 = firm well formed, 3 = soft and partially formed faeces, 4 = loose, semi-liquid faeces, and 5 = watery faeces). Data were analysed as a randomised complete block design using GLM procedures (SAS^®; USA). The initial BW was used as a covariate for ADFI and ADG. Differences among the treatment means were determined using the Tukey’s multiple-range test with P < 0.05 indicating statistical significance.

From d 1 to 42, ADG and G : F of pigs fed the R275 diet was 6.9% and 6.9% higher (P < 0.05) than those fed the CON diet. On d 42, pigs fed with the R275 diet had higher (P < 0.05) IgA concentrations than other treatments, and IgM was 39.6% higher (P < 0.05) in the R275 treatment compared with CON pigs. After challenge, the concentrations of cortisol, TNF-α, and IL-6 in the CON treatment were 53.3%, 16.6%, and 10.3% lower (P < 0.05) than the R275 treatment, while IGF-I was higher (P < 0.05) in the nucleotide treatments than in CON. On d 21, 28, 35, and 42, CON pigs had higher (P < 0.05) faecal scores than the nucleotide treatments.

Nucleotides may maintain a stable microbiota in the ileum, which may lead to improved ADG and G : F. The reduction of diarrhoea could be a direct consequence of an improved intestinal maturation. The increase in immunoglobins after challenge may lead to an improvement in the immune system of pigs fed diets with nucleotides. In conclusion, dietary nucleotide supplementation can improve growth performance, indices of immune function, and decrease faecal score in weaning pigs challenged with E. coli K88.