I . The effect of grinding and pelleting S 24 perennial rye-grass (Lolium perenne L.), harvested at two stages of maturity and artificially dried, on the sites of digestion of nitrogenous constituents was studied with sheep equipped with a fistula into the rumen and re-entrant cannulas at the proximal duodenum and terminal ileum. Chopped and pelleted grasses at both stages of maturitywere each givcn at goo g dry matter ( D M ) / z~ h to each of five shcep; the two forms of the early-cut grass were also given each to four of the five sheep at 1400 g D M / Z~ h.
2.The pelleting process significantly depressed apparent digestibility of total nitrogen in both grasses ( P < 0.05). For the early-cut grass neither physical form nor level of feeding had any significant cffect on N retention; for the medium-cut grass N retention was significantly higher ( P < 0.05) when thc pelletcd form was given. N retention was significantly lower on the medium-cut grass ( P < 0.05) than on the early-cut grass.
3.For individual amino acids the greatest relative increases (intake = 100) at the proximal duodenum were found for mcthionine and cysteine/cystine ( P < 0.001) on all six diets, together with tryptophan ( P at least < 0.01) and lysine ( P at least < 0.05) on five of the diets, and including histidine on the early-cut diets ( P at least < 0.01). At the low level of feeding, incrcase in stage of growth at cutting significantly dcpressed the relative amounts of phenylalanine, lysine, serine ( P < 0.05), histidine, aspartic acid and tyrosine ( P < 0.01) entering the small intestine, and increased those of tryptophan ( P < 0.05). Pelleting of the early-cut grass significantly increased the amounts of methionine entering the small intestine compared with feeding it chopped (P
A microbiological assay using Lactobucillusplanturum was used to determine the levels of pantothenic acid (PA) in food and digesta samples from sheep fitted with duodenal and ileal re-entrant cannulas, given a variety of diets. ACP-bound PA was not measured. With most of the diets studied there was an increase in 'total' PA and CoAbound PA before the small intestine. Both the increase in CoA-bound PA prior to the duodenum and the 'total' PA reaching the duodenum were positively and significantly related to the microbial dry matter synthesised in the rumen. Free PA at the duodenum was significantly related to the dietary intake of free PA. The apparrent absorption of total PA within the small intestine was significantly related to the quantity entering the small intestine suggesting a passive absorption mechanism. It is suggested that CoA-bound PA entering the small intestine is hydrolysed to release free PA which is then available for absorption.
I . The effect of altering the physical form of a regrowth crop of dried lucerne (Medicago sativa L. Tar. Chartainvilliers) on the site of nitrogen digestion was studied with sheep fitted with a rumen cannula and re-entrant cannulas at the proximal duodenum and the terminal ileum. Chopped, cobbed, and ground and pelleted diets were prepared by processing the same high-temperature dried crop and given twice daily to sheep at a level of intake of 910 g dry matter/z+ h. 2.The chopped diet had a slightly lower content of total N and amino acid N than the other forms but the amino acid composition was similar and there was no difference between the diets in the apparent digestibility of total N.3. For all three physical forms the amounts of total N reaching the small intestine were greater than those ingested. The disappearance of apparently digested N in the caecum and colon of the sheep was significantly higher with the chopped form of the diet than with the cobbed and ground, pelleted forms ( P < 0.01).4. Of the individual amino acids, the greatest (and significant) increases compared with the food at the proximal duodenum were found for methionine, lysine, tryptophan and cysteinel cystine, and there were significant differences between diets for methionine, tryptophan, valine and cysteinelcystine. The amounts of isoleucine were also significantly increased at the proximal duodenum. Significant losses at the duodenum occurred for aspartic acid (all diets) and for phenylalanine and proline (two diets).5 . The amounts of tryptophan, methionine, cysteinelcystine and serine absorbed from the small intestine, relative to amounts ingested, were significantly greater on the chopped and pelleted diets than on the cobbed diet. Ditferences between the chopped and pelleted diets in relative amounts absorbed from the small intestine were observed for tryptophan ( P < 0.01) and for cysteinelcystine ( P < 0.05).6. Apparent digestibilities of total amino acid N within the small intestine (based on amounts entering the small intestine) were 71'5, 66.2 and 69.8 yo for the chopped, cobbed and pelleted diets respectively. 7.Mean values for apparent digestibility of individual amino acids within the small intestine ranged from 47 % for histidine to 80 "/o for methionine. Of the eighteen amino acids examined, values for apparent digestibility in the small intestine of thirteen of them were lowest on the cobbed diet; the effect was particularly noticeable for histidine. Despite this variation, there was a very significant positive correlation between the amounts of individual amino acids reaching the small intestine and absorbed from it with all three diets (n = 54; r = 0.990; P < 0.001); the same was true for each individual diet.8. Significantly lower amounts of nucleic acid N entered the small intestine of sheep given the pelleted diet ( P < 0.01). From the results for nucleic acid N it was calculated that on the chopped and cobbed diets 44-46 yo of the total N entering the small intestine was of microbial origin; on the pelleted di...
SummaryDifferences in milk-fat composition in summer and winter have been demonstrated and related to feeding for an autumn calving Friesian herd and an Ayrshire herd in which calving was equally divided between spring and autumn. The observations are in agreement with previous results obtained for milk fat in the Northern Hemisphere.Summer milk fat contained more C18acids and less C4–C16acids than winter milk fat, the effect being particularly marked for the autumn calving herd.Changes in the pattern of feeding altered the fatty acid composition of milk fat from both herds, and abrupt changes in feeding were clearly reflected even at times when stage of lactation effects were greatest.
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