Effects of drinking water acidification by organic acidifier on growth performance, digestive enzyme activity and caecal bacteria in growing rabbits

• Published in: Animal feed science and technology 2014-04, Vol.190, p.87-94
• Main Authors: Zhu, K.H., Xu, X.R., Sun, D.F., Tang, J.L., Zhang, Y.K.
• Format: Article
• Language: English
• Subjects: Bacteroides–Prevotella; Drinking water acidification; Escherichia coli; Growing rabbit; Growth performance; Lactobacillus; Pepsin activity
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/j.anifeedsci.2014.01.014

This study investigated the effect of drinking water acidification by organic acid on growth performance, gastrointestinal enzyme activity and pH, and the proportion of selected bacterium to total bacteria in growing rabbits. Ninety-six male healthy rabbits weaned at 35 days old of age were randomly divided into four groups: control, pH 5.0, pH 4.3 and pH 3.6 groups. The control group drank groundwater with a pH of 7.3. To obtain the required pH, a commercial mixture of organic acid was added to groundwater in groups pH 5.0, pH 4.3 and pH 3.6 by 0.55g/kg, 0.85g/kg and 3.3g/kg, respectively. The trial lasted for 35 days, and 6 rabbits from each group were slaughtered at the end for subsequent measurements. Acidification of drinking water did not affect diarrhoea incidence and mortality rate, but had a quadratic increasing effect on average daily gain (ADG) and final weight, and quadratic decreasing function on feed conversion ratio (FCR) (P=0.013, P=0.007 and P=0.040, respectively), 0.85g/kg organic acid supplementation showed maximal positive effect on ADG, final weight and FCR. Compared to control, ADG and final weight in pH 4.3 group increased by 12.9% (P=0.016) and 8.3% (P=0.020), respectively. The acidity of digesta in gastric fundus and gastric middle was decreased linearly (P=0.007 and P=0.014, respectively). Rabbits in pH 3.6 group tended to have a lower gastric middle pH than control (P=0.09). Organic acid supplementation in drinking water showed a quadratic increasing effect on the activity of pepsin in the stomach (P=0.036), and pH 4.3 group had highest value, which increased by 23.6% (P=0.06) when compared with control. The proportions of Escherichia coli to total bacteria and to Bacteroides–Prevotella were decreased linearly (P=0.025 and P=0.003, respectively). Compared with control, rabbits in other three groups had lower proportions of E. coli to Bacteroides–Prevotella (P=0.03, P=0.01 and P=0.02, respectively). The relative proportion of Bacteroides–Prevotella or Lactobacillus to total bacteria tended to increase linearly (P=0.09 and P=0.058, respectively). This study demonstrated that acidification of drinking water with organic acid improved part of growth performances, compensated for gastric acidity and affected microbial community structure in caecum in growing rabbits. The most appropriate pH of acidified drinking water was 4.3 in present study.