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  • 1
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: It is widely believed that the initial degradation of proteins contained in grazed forage is mediated by rumen micro-organisms, but the authors’ recent work suggests that the plant cells themselves contribute to their own demise. In the present study the responses of Lolium perenne leaves to the rumen environment were investigated by using an in vitro system which simulates the main stresses of the rumen but from which rumen micro-organisms were excluded. Degradation of leaf protein and the accumulation of amino acids in tissue and bathing medium occurred over a time-scale that is relevant to rumen function, and in a near 1 : 1 ratio. Significant loss of nuclear material was observed after 6 h incubation and chloroplasts became morphologically more spherical as the incubation progressed. In situ localization suggested that ribulose 1,5 bisphosphate carboxylase/oxygenase was broken down within chloroplasts which from cytology were judged to be intact. We conclude from these data that plant metabolism may play a significant role in breaking down plant proteins within relatively intact organelles in the rumen. The determinations of chlorophyll content and cell viability revealed that the plant processes occurring in the simulated rumen were similar but not identical to those of natural senescence.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 50 (1995), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The use of freshly cultured lactic acid bacteria in comparison with conventional freeze-dried preparations as inoculants for grass silage was examined. Perennial ryegrass was ensiled in laboratory silos, either untreated or treated with formic acid, or a commercial freeze-dried strain of Lactobacillus plantarum, or a fresh culture of the same strain of L. plantarum, or fresh cultures of Pediococcus pentosaceous, or Lactococcus lactis alone or in combination with L. plantarum. All inoculants were applied at a rate of 106 colony-forming units g−1 fresh matter, with the mixtures containing a 1:l ratio of each species. Herbage treated with freshly cultured inoculants exhibited shorter lag times, in relation to the initiation of pH decline, than those associated with untreated or freeze-dried inoculant-treated herbages. Treatment of herbage with inoculants containing L. plantarum increased the initial speed of pH decline. In comparison with silages made with freeze-dried L. plantarum, in measurements made during the initial 14 d of ensilage, those inoculated with fresh cultures bad significantly (P〈0·05) higher lactic acid concentrations and significantly (P·0.05) lower pH values. Both P. pentosaceous and L. lactis initiated a rapid fermentation, but compared to L. plantarum alone, or mixtures of L. plantarum with P. pentosaceous or L. lactis, these cultures demonstrated intermediate rates of lactic acid production and pH decline. All mature (105 d) silages were of good quality with pH values of four or less, low ammonia-N concentrations (〈100gkg−1 total N) and no detectable levels of clostridia or butyric acid. Results suggested that the main advantage of freshly cultured inoculants over their freeze-dried counterparts may lie in their metabolic state when added to herbage.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eight multiparous Holstein–Friesian dairy cows in late lactation were used to investigate the potential of using perennial ryegrass with a high concentration of water-soluble carbohydrate (WSC) to increase the efficiency of milk production. After a pretreatment period on a common pasture, the cows were each given ad libitum access to one of two varieties of zero-grazed grass continuously for 3 weeks. Treatments were: high sugar (HS), an experimental perennial ryegrass variety bred to contain high concentrations of WSC; or control, a standard variety of perennial ryegrass (cv. AberElan) containing typical concentrations of WSC. The two grass varieties were matched in terms of heading date. All animals also received 4 kg day–1 standard dairy concentrate. Grass dry matter (DM) intake was not significantly different between treatments (11·6 vs. 10·7 kg DM day–1; s.e.d. 0·95 for HS and control diets respectively), although DM digestibility was higher on the HS diet (0·71 vs. 0·64 g g–1 DM; s.e.d. 0·23; P 〈 0·01) leading to higher digestible DM intakes for that diet. Milk yield from animals offered the HS diet was higher (15·3 vs. 12·6 kg day–1; s.e.d. 0·87; P 〈 0·05) and, although milk constituent concentrations were unaffected by treatment, milk protein yields were significantly increased on the HS diet. The partitioning of feed N was significantly affected by diet, with more N from the HS diet being used for milk production (0·30 vs. 0·23 g milk N g–1 feed N; s.e.d. 0·012; P 〈 0·01) and less being excreted in urine (0·25 vs. 0·35; s.e.d. 0·020; P 〈 0·01). In a separate experiment, using the same grasses harvested earlier in the season, the fractional rate of DM degradation, measured by in situ and gas production techniques, was higher for the HS grass than for the control. It is concluded that increased digestible DM intakes of the HS grass led to increased milk yields, whereas increased efficiency of utilization of the HS grass in the rumen resulted in the more efficient use of feed N for milk production and reduced N excretion.
    Type of Medium: Electronic Resource
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