An 80 day study was conducted to evaluate the growth promoting effects of a unique mannoserich fraction (MRF) derived from yeast cell walls of Saccharomyces cerevisiae, relativeto copper and tylosin in commercially housed grower and finisher pigs. 1008 male growerpigs (29.7±1.99 kg live weight) were randomly allocated to four treatment groups of 252pigs. There were 12 replicates for growth rates (21 pigs per pen) and 6 replicates for feedintake and FCR (42 pigs per feeder). The dietary treatments consisted of a control (CON,containing no growth promoting feed additives), copper (COP, containing 200 ppm of copperas copper sulphate in both grower and finisher pigs), MRF (containing 400 ppm and200 ppm of ActigenTM (Alltech Biotechnology, Nicholasville, KY) in grower and finisher dietsrespectively), and tylosin (TYL, containing 40 g and 20 g of tylosin in grower and finisherdiets respectively). Growth performance and mortality were monitored over the grower (d0–38) and finisher (d 39–80) periods. Slaughter characteristics (carcass weight and backfatthickness at the P2 position) were recorded at d 80. Mannose rich fraction pigs grew faster(P<0.01) than CON or COP pigs during the grower phase. Mannose rich fraction and TYLpigs also tended to (P=0.08) have better FCR during the grower phase than those on theCON and COP treatments. No significant treatment effects were observed for growth performanceduring the finisher phase or over the entire study (d 0–80). However, MRF pigshad a significantly higher (P<0.01) dressing percentage and heavier carcass weight thanpig on all other treatments. There was no influence of growth promoting feed additives onbackfat thickness. Overall, MRF was as effective as tylosin and more effective than copperas a growth promoter in grower pigs. Mannose rich fraction inclusion was able to enhancethe yield of saleable pork, and was the most effective growth promoting option tested.
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