Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

John. P. Hitchcock

Committee Members

Kelly R. Robbins, Frank B. Masincupp


Three experiments were conducted utilizing 62 crossbred pigs, 30 pigs in experiment 1 and 16 pigs each in experiments 2 and 3. Two other experiments were conducted utilizing 168 Hubbard X Hubbard chicks; 60 chicks in experiment 4 and 108 chicks, 54 per age group, in experi-ment 5. The objective of these experiments was to evaluate the effects of incremental additions of D,L-methionine to the diet of chicks and weanling pigs. Pigs were allotted by weight within litter replicate and chicks were allotted within weight groups to one of four dietary treat-ments in experiments 1 and 5. The diets contained methionine and cystine at recommended levels (N.R.C., 1977 and 1979) for control diets and methionine at 2.5, 4.0 or 5.5 X N.R.C. requirements in treatment diets of experiments 2, 3 and 4. Diets containing the N.R.C. requirement of methionine with treatment diets having 1.5 or 3.0 X N.R.C. levels were used in experiments 1 and 5. Bodyweight, feed consumption, hematocrit, hemoglobin and plasma glucose were determined at one-week intervals in each experiment. In all but experiment 1, plasma free amino acid concentrations were also determined. Results from the first swine experiment indicated that feed consumption was significantly reduced in pigs fed methionine at 3 X the N.R.C. requirement, however, gain per feed (gain:feed) was significantly increased in pigs consuming that level of methionine during week 2. Data from weanling pig experiments 2 and 3 indicated that gain and gain:feed were increased by the addition of 2.5 times the control dietary level of methionine but that a precipitous decrease resulted from higher methionine supplementation during the first week of each trial. Gain and gain:feed were affected to a smaller degree in weeks 2 and 3 as compared to week 1. Hematological parameters were not affected by methionine additions in any of the weanling pig experiments. Plasma methionine, threonine and cystine were increased in both experiments 2 and 3 in pigs fed the two highest levels of dietary methionine. Plasma glycine was depressed throughout the experiment in pigs fed 4.0 or 5.5 X the methionine requirement in experiment 2 and was depressed during week 1 only, in experiment 3. Plasma serine increased in pigs consuming the highest level of methionine in experiment 2 but did not "exhibit a consistent pattern in experiment 3. Plasma cystathionine levels decreased in pigs fed 4.0 or 5.5 X the N.R.C. requirement of methionine in both pig experiments. Weanling pigs appear to adapt to high methionine consumption evidenced by resumption of gain and gain:feed while consuming elevated levels of methionine. Also, by decreasing the plasma free methionine concentration over a short period of time while dietary methionine supplementation remains high, indicated an adaptive mechanism was functioning. Results from the chick experiments indicated that excess methionine consumption depressed gain, feed intake and gain:feed in both young (8-day-posthatched) and older {5-week-posthatched) birds. Hematocrit and hemoglobin values were reduced in young chicks fed increasing amounts of methionine. Hematocrit levels were significantly decreased in older chicks but hemoglobin values were unaffected in chicks consuming high levels of dietary methionine. Plasma glucose was increased in young chicks consuming the highest amount of methionine but older chicks' plasma glucose was not significantly affected. Plasma methionine was elevated in young and old chicks consuming supplemental methionine. Plasma threonine was depressed in young chicks fed 3.0 X the N.R.C. requirement. In experiment 4, plasma glycine, serine, cystine and cystathionine were not affected by treatment. In experiment 5, plasma glycine was increased in young chicks fed 5.0 X the N.R.C. level but was decreased in older chicks consuming methionine at 3.0 or 5.0 X the requirement. Plasma serine and cystine were elevated in young chicks (experiment 5) fed the two highest levels of methionine but, in 5-week-old chicks, plasma serine and cystine were not altered by methionine supplementation of 5.0 X the N.R.C. requirement. Plasma cystathionine was not affected in either chick experiment or in either age group.

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