Morphological changes associated with rumino-reticular development was
compared in two groups of SA Mutton Merino lambs ( n=12) fed different
diets at 3-5 weeks, 17-19 weeks and 31-33 weeks of age. Diet groups were
identified as MMH or MHH according to the sequence at which the
full-milk replacement (M) or hay (H) diet were fed to the lambs over the
three study phases (phases I, II and III) preceding each age period.
Prominent differences in the morphology (size and volume) and function
(pH, proteolytic activity and microbial population) of the
rumino-reticulum were observed in indicator lambs ( n=2) killed at every
age period and also between milk-fed and hay-fed lambs. The size of the
rumino-reticulum was rudimentary at 3-5 weeks of age and remained
underdeveloped in lambs at 17-19 weeks of age which had received a
full-milk replacement diet during phase II. One lamb, slaughtered at 3
weeks of age, showed a large distended rumen with severe sloughing of
the surface cells of the stratum corneum. The size of the
rumino-reticulum increased in size (2 X) in lambs which were fed hay
relative to the milk-fed lambs during phase II and reached adult
proportions in all lambs at 31-33 weeks of age. Ultrastructural
examination showed that rumen papillae were more developed in lambs fed
hay during phase II when compared to those of milk-fed lambs. Rumen
papillae were best developed in phase III lambs.
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