Influence of cutting time and N-fertilization on the nutritive value of timothy, 2: Estimates of rumen degradability of nitrogenous compounds
1988
Lindberg, J.E. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Husdjurens Utfodring och Vaard)
Rumen degradability of nitrogenous compounds in 14 batches of timothy (Phleum pratense L.) cut at different stages of maturity and fertilized with 60, 120 and 180 kg N per hectare in the spring, was studied using the nylon bag technique. The effective rumen degradability of feed N (EPD), if estimated from total N disappearance, was related to the crude protein content (Nx6.25) of the batches (r2=0.78). There was a very close relationship between total N and neutral detergent fibre N (NDF-N) disappearance (r2=0.88) from h rumen incubation and onwards. On average, the neutral detergent fibre bound N (NDF-N) was 42.3, 40.6, 33.2, 36.8, 30.0 and 28.5% at 2, 4, 8, 16, 24 and 48 h rumen incubations, respectively. It was assumed that the proportion of N not recovered in the NDF-N fraction (i.e., NDS-N) was attributed both to degraded feed protein and to colonizing rumen microbes not removed in the washing procedure. A new set of EPD values was calculated from NDS-N disappearance. The latter EPD values was considered to be closest to true N disappearance in the rumen, while the first set of EPD values (from total N) should be considered as apparent. The EPD values corrected for microbial contamination was close to 90% and did not differ significantly in the 14 batches despite a very large range in CP content (7 to 24% CP in DM).n
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