| A total of six experiments were conducted to evaluate the effects of supplementing specific nutrients including menhaden fish meal (MFM), spray-dried plasma (SDP), glutamine (GLN), glutamate (GLU), monosodium glutamate (MSG), nucleotides (NUC), and a hatchling supplement (Oasis) in the diets of posthatch poultry and postweaning pigs on the growth performance, small intestinal morphology and immune responses. In the first experiment (Chapter II), during the first week, feeding 3% SDP improved growth performance of posthatch broilers. However, at d 3, 7 and 14 posthatch, no effects on villus height (VH) and villus height:crypt depth (VCR) ratio of broilers were observed by feeding GLN, MFM and SDP supplemented diets. In the second experiment (Chapter III), from d 0 to 7 after hatch, feeding 3 to 12% MFM resulted in linear increase in weight gain and feed efficiency of turkey poults. Feeding 1% GLN improved feed efficiency of turkey poults from d 0 to 21 posthatch. The third experiment (Chapter IV) indicated feeding the 1% GLN for 48 hours was more effective than 1% MSG, 0.8% NUC, or 1% GLU in restoring the disrupted intestinal morphology of 48 hours fasted broiler chicks. In the fourth experiment (Chapter V), from d 0 to 7 postweaning, feeding the 3.5% SDP and the GLU + NUC mixture diets improved the daily gain of pigs, and feeding the 3.5% SDP, GLU + NUC mixture and NUC diets increased the VH of jejunum of weaned pigs. In the fifth experiment (Chapter VI), the results indicated that feeding 7% SDP or 2% GLN was effective in alleviating growth depression caused by an E. coli K88 + challenge. Feeding either SDP or GLN mitigated villus atrophy and intestinal morphology disruption after E. coli challenge, indicating the beneficial effects of SDP and GLN in preventing pathogenic invasion and maintaining normal intestinal integrity and function. Feeding SDP or GLN may have different modulatory mechanism on the GH/IGF-1 uncoupling under an E. coli challenged situation. The sixth experiment (Chapter VII) indicated that broiler chicks having access to feed or Oasis immediately after hatch was beneficial for growth performance and resistance to subsequent E. maxima coccidiosis challenge. Glutamine supplementation was beneficial for the growth performance and livability of birds posthatch. Fasting for 48 h immediately after hatch impaired the gut development, immune system maturation and growth performance of broilers. Vaccination with E. maxima was proven to be effective to alleviate growth performance depression and intestinal infection associated with E. maxima challenge. In summary, these specific nutrients had different beneficial roles in the growth performance, intestinal morphology and immune responses of posthatch poultry and weaned pigs. Especially, glutamine was effective in maintaining the intestinal integrity and function of broilers and pigs under fasting and immune challenged (Escherichia coli K88+ or E. maxima) situations. |
