03982naa a2200277 a 450000100080000000500110000800800410001910000200006024500780008026000090015852032770016765000260344465000110347065000090348165000180349065000200350865000100352865000130353865000270355165000100357865000200358865000090360865000200361770000170363777300500365417938691999-03-02       1965    bl ---       0--  u    #d1 aDYNE, G. M. van  aBotanical composition of sheep and cattle diets on a mature annual range.  c1965  aFive steers and seven sheep with esophageal fistulas were grazed on a mature California annual range for one summer. Early morning and late after noon dietary samples were ataken on five consecutive days in three periods from early July to early September, 1961. Samples were analyzed microscopically for genus or species and plants parts. Statistical analysis for twenty-four dietary components are presented for three periods, five days, two times of day, two classes of stock, individual animal differences, and interactions. Herbage availability decreased from 1490 to 420 pounds per acre during the three periods. Preference for most of the forage constituents changed significantly as herbage became limited. Heads, forb stems, forb leaves, total grasses, total forbs, Aira caryophyllea, Avena barbata and bromus spp. were grazed in the same relative amounts as they occurred on the range throughout the summer. Generally the diet had less stems and more leaves in early than in late summer. No significant differences were found in botanical constituents of the average daily diets within a sampling period of 5 days. One-third of the botanical constituents were eaten in different amounts in the morning than in the late afternoon. When based on differences between clipped and fistula samples, afternoondiets were more selected than were morning diets. Cattle and sheep diets differed significantly summer-long for about half of the constituents. Sheep selected more total leaves, grass leaves, forb leaves, and legumes than did cattle, whose diets were higher in total stems, grass stems, Avena barbata, Gastridium ventricosum, unidentifiable, and Erodium botrys. Cattle and sheep did not respond in the same way to decreased available herbage, as indicated by significant period x class of stock interactions for many dietary components. Decreasing selectivity by sheep suggests that they were more affected by herbage shortage than were cattle. Nevertheless, by the end of summer, sheep contunued to be more selective than cattle. On the average, individual sheep differed in more dietary variables than did individual cattle. Certain sheep had diets similar to those of cattle, but no steer selected a diet similar to the average diet of sheep. Differences in most dietary components among individual cattle and sheep decreased as herbage became limited. The number of animals required to sample dietary botanical composition within 10 per cent of the mean with 90 per cent confidence would be excessive for most constituents. Fewer animals would be required in late than in early summer and more sheep than cattle would be needed, but by grouping botanical constituents, fewer animals are needed. As many as nine animals would be required to sample the major plant groups in middle and latte summer with the precision mentioned above. Most previous studies have not used enough esophogeal-fistulated animals. The relative preference of cattle and sheep for each plant is given as the ratio of the amount or percentage of the plant in the diet to the amount available on the range. Less abundant species generally were either higly selected or rejected, while abundant ones furnished the bulk of the diets and were neither significantly selected nor rejected.  abotanical composition  acattle  adiet  adigestibility  anutritive value  asheep  aCarneiro  aComposição Botânica  aDieta  aDigestibilidade  aGado  aValor Nutritivo1 aHEADY, H. F.  tHilgardiagv.36, n.13, p.465-490, Sept. 1965.