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Response of Lambs to Oral or Abomasal Supplementation of Methionine Hydroxy Analog or Methionine¹

124 Animal Sciences Laboratory, Department of Animal Science, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

Methionine hydroxy analog (MHA) or DL-methionine was administered orally or abomasally to lambs 1) to determine the extent of rumen degradation of these compounds and 2) to estimate the replacement value of MHA for methionine at the postruminal level. In the first experiment, daily supplements of 2.7 g methionine or 3.08 g MHA were given orally or abomasally. Plasma methionine to valine (Met/Val) ratios for lambs supplemented orally with either of the compounds were not significantly different (P > 0.05) than the controls. Both compounds when supplied abomasally increased the plasma Met/Val ratio relative to the control (P < 0.005). DL-Methionine infusion increased the plasma ratio more than MHA infusion (P < 0.005). In the second experiment, the highest level (12.3 g offered, 9.7 g consumed) of MHA failed to affect plasma Met/Val ratios (P < 0.05). Consumption of the offered diet was depressed with the high level of MHA supplementation (P < 0.05). In the third experiment, DL-methionine or MHA providing equal amounts of methionine or "methionine precursor" were infused abomasally to evaluate the replacement value of MHA for methionine post-ruminally. Plasma Met/Val ratios indicated that less than one-third of the infused MHA was converted to methionine. Methionine infusion resulted in a linear change in feed intake but MHA had no effect. These studies show that at the levels tested, neither MHA nor DL-methionine survives rumen degradation to affect plasma Met/Val ratios and that it is unlikely that dietary MHA will meet postruminal requirements of methionine in ruminant animals.

KEY WORDS: • methionine • methionine hydroxy analog • abomasal infusion

¹ Supported in part by federal funds (Hatch 20-342) and by grants-in-aid from Masonite Corporation, Chicago, Ill., and National Soybean Processors Association, Washington, D. C.

² Present address: Agricultural Research Institute, Nicosia, Cyprus.

³ Present address: Departamento de Zootecnia, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil.

Manuscript received 18 June 1973.