Effects of medium-chain fatty acids as alternatives to ZnO or antibiotics in nursery pig diets

The objective of this experiment was to evaluate the effects of medium-chain fatty acids (MCFA) on nursery pig performance in place of ZnO and carbadox. In this trial, 360 weanling pigs (DNA 200 × 400; 5.4 ± 0.07 kg BW) were fed for 35 d, with 6 pigs/pen and 10 replicate pens/treatment. Upon weaning, pigs were weighed and allotted to pens based on BW in a completely randomized design to one of six treatment diets: 1) Negative control (no added ZnO or carbadox); 2) Control + 3,000 ppm ZnO in phase 1 and 2,000 ppm ZnO in phase 2; 3) Control + 50 g/ton carbadox; 4) Control + C6:C8:C10 MCFA blend; 5) Control + Proprietary Oil Blend (Feed Energy Corp.); and 6) Control + monolaurate blend (FORMI GML from ADDCON). Treatment diets were fed through two dietary phases and a common diet fed through phase three. Pigs and feeders were individually weighed on a weekly basis to determine average daily gain (ADG) and average daily feed intake (ADFI). From days 0 to 19, pigs being fed the ZnO or Carbadox diets had the greatest ADG. These pigs had significantly higher (P < 0.05) ADG than pigs fed the control or Feed Energy Proprietary Oil Blend, whereas pigs fed the C6:C8:C10 blend or FORMI GML diets had similar (P > 0.05) ADG compared with those fed carbadox. These effects were primarily driven by feed intake, which was greatest (P < 0.05) in pigs fed ZnO and carbadox. Treatment diet had a marginally significant effect (P = 0.078) on G:F. Increased day 19 BW (P < 0.05) was observed for pigs fed ZnO and carbadox compared with the negative control, whereas other treatments were intermediate. Additionally, blood data and fecal scores were collected throughout the trial. On day 21, pigs fed ZnO or carbadox had higher (P < 0.0001) glucose values than those fed the Feed Energy Proprietary Oil Blend, with other diets being intermediate, showing potential health benefits of carbadox. Although ZnO resulted in higher glucose values, it may also contribute to hepatic issues. Although replacing ZnO and carbadox with MCFA did not result in significant changes in gut microflora, it did affect fecal consistency by softening the feces during the treatment period. Overall, these results show that ZnO and carbadox are valuable additives to help maximize growth performance in early stages of the nursery. Some MCFA products, like FORMI GML, may result in similar performance, whereas others restrict it. Thus, additional research is needed to study the effectiveness of MCFA to replace ZnO or feed-based antibiotics.