The digestion of pasture plants by sheep. IV*. The digestion of Phalaris tuberosa at different stages of maturity

Abstract

A study was made of the composition, intake, and digestion of dried Phalaris tuberosa forage that had been harvested at three stages of maturity. Advancing maturity was associated with: (i) decreased food intake; (ii) increased expenditure of time and energy in chewing activities; (iii) decline in the rate of flow of digesta from the abomasum though not from the rumen; (iv) decline in digestibility in the whole tract of organic matter, nitrogen, and the structural carbohydrates; (v) decline in the digestion of fibre in the rumen relative to that occurring in the whole tract; (vi) decline in the quantities of volatile fatty acids and amino acids made available to the animal. By contrast only small differences attributable to maturity were observed in: (i) the distribution of digestion of organic matter between stomach and intestines; (ii) the digestibility of nitrogen other than ammonia in the intestines; (iii) the proportions of digestible organic matter derived from volatile fatty acids and amino acids; (iv) the proportions of individual amino acids in the digesta passing to the intestine. It was calculated that microbial piotcin contributed 33, 38, and 47% of the protein passing from the stomach to the intestincs with the diets of advancing maturity. Most of the remaining protein was presumably of dietary origin. About 80% of the crude protein in the digesta was present in the form of amino acids, and the quantities of amino acids released in the intestines were calculated to be equivalent to 64–66 g/100 g crude protein intake. With advancing maturity of the diets the plasma levels of the essential ammo acids except lysine, histidine, and arginine declined; there was little effect of diet on the plasma levels 01 non-essential amino acids. However, relative to total essential amino acids, the ratios of valine and leucine decreased with advancing maturity of the diet while those of lysine, histidine, glutamate, glycine, alanine, and serine increased. * Part 111, Aust. J. Agric. Res., 1969, 20, 347.

An evaluation of Panicum maximum cv. Gatton: 2. The influence of stage of maturity on diet selection, intake and rumen fermentation in sheep

“…The results of Hogan et al (1969) and Playne & Kennedy (1976) are in concordance with these findings. Proportions of propionic acid decreased (P < 0.05) as herbage matured during summer and autumn.…”

“…Rumen NH 3 -N levels decreased as pasture matured during all seasons (Table 4). Hogan et al (1969) also observed a decrease in rumen NH 3 -N levels with advancing forage maturity. Rumen NH 3 -N concentrations were the highest in summer, followed by autumn and winter which corresponds with the results of Meissner et al (1993).…”

Prospects for improving the nutritive value of temperate, perennial pasture grasses

“…However, there are several other changes associated with advancing maturity that contribute to the lowering of the nutritive value of grass forage. Thus Hogan et al (1969) showed that for P. tuberosa there was a decreased intake; an increased expenditure of time and energy in chewing activities; a decline in rate of flow of digesta from the abomasum, though not from the rumen; a decline in digestibility, in the whole tract, of organic matter N and structural carbohydrates; a decline in digestion of fibre in the rumen relative to that occurring in the whole tract; and a decline in quantities of volatile fatty acids and amino acids made available to the animal.…”

Quantitative digestion of fresh herbage by sheep:V. The digestion of four herbages and prediction of sites of digestion

“…Relationship between organic matter digested in the stomach and organic matter apparent digestibility in sheep fed a wide range of diets. Data used include: (A)Ulyatt & MaeRae, 1974; (B) present paper; (C)Beever et al 1972; Egan et al 1975;(E) Egan, 1974; Nicholson & Sutton, 1969; Thomson et al 1972; Hogan & Weston, 1967a; (I) (J)Hogan, Weston & Lindsay, 1969;(K) …”