Effect of feed withdrawal or challenge with Pasteurella multocida on growth, blood metabolites, circulating growth hormone, and insulin-like growth factor-I concentrations in eight-week-old turkeys

The daily effects of feed withdrawal or a bacterial disease (Pasteurella mu ltocida; PM) challenge was studied in a slow-growing line of turkeys. The f ollowing groups (n = 6 birds/group) were sampled for up to 13 d: untreated control (CON), 4-d feed withdrawal followed by refeeding (FAST), a group th at succumbed within the first 2 to 3 d after PM challenge (E-DEAD), a group that succumbed 8 to 9 d after PM challenge (L-DEAD), a group that survived the PM challenge (SUR), and a group treated with both PM challenge and 4-d feed withdrawal followed by refeeding (FAST/CHAL). Daily feed intake and B W gains were markedly reduced in the E-DEAD and L-DEAD groups immediately a nd 3 d after PM challenge, respectively. Feed intake and BW gain between CO N and SUR groups of turkeys were not different throughout the trial. The tu rkeys in the FAST group followed the expected feed withdrawal and refeeding patterns for feed intake and BW loss or gain. The FAST/CHAL turkeys consum ed the minimal amount of feed to maintain BW after refeeding. Plasma uric a cid sharply increased 1 d prior to death in both E-DEAD and L-DEAD groups o f turkeys. Plasma uric acid also increased each consecutive day during fast ing in the FAST and FAST/CHAL groups of turkeys. Plasma growth hormone was measured in only the CON and FAST groups and increased from about 40 to 85 ng/mL in the FAST group during fasting but returned to control levels withi n 1 d of refeeding. Circulating plasma insulin-like growth factor-I (IGF-I) decreased from about 17 to 5 ng/mL in the PM-challenged (E-DEAD, L-DEAD, a nd FAST/CHAL groups) and FAST groups. The concentration of IGF-I returned t o prefeed withdrawal levels within 3 d of refeeding the FAST group of turke ys. It was concluded that 1) turkey poults that were not susceptible to the PM challenge generally maintained physiological functions at control bird levels, 2) susceptible turkey poults generally exhibited depressed feed int ake and BW gains, and 3) poults challenged with both feed withdrawal and PM treatment responded differently than poults challenged with either feed wi thdrawal or challenge with PM. The depletion of energy intake and mobilizat ion of energy stores in susceptible poults might have contributed to the ra te at which PM caused the poults to die.