Influence of cutting time and N-fertilization on the nutritive value of timothy, 3: Rumen degradability of cell walls, in vivo digestibility and estimated energy and protein values
1988
Lindberg, J.E. | Lindgren, E. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Husdjurens Utfodring och Vaard)
In vivo digestibility of organic matter (OM), neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP; N x 6.25), NDF bound nitrogen (NDF-N) and rumen degradability of OM and NDF was studied in 14 batches of timothy (Phleum pratense L.) The rumen degradability of nitrogenous compounds has been presented separately (Lindberg, 1988). In the first cut , digestibilities of OM, NDF and ADF decreased with increasing NDF and ADF contents. In the second cut, digestibilities decreased despite fairly constant contents of both NDF and ADF. The content of metabolizable energy (ME) was most closely related to digestibilities of OM and NDF (r=0.98) and less to the digestibility of ADF (r=0.93). The digestibilities of CP and NDF-N both showed a non-linear increase with increasing CP content. It was also obvious that both the CP and NDF-N digestibilities were negatively correlated to the ADF-N content in timothy (r=0.93 and 0.75 respectively). The estimated rumen degradabilities (with nylon bags) of both OM and NDF were closely related to in vivo digestibilities (r=0.92 and 0.96 respectively). The calculated content of amino acids absorbed in the small intestine (AAT) from the timothy batches was within 1.2 units across all batches. On average, the timothy supplied 7.0 g AAT per MJ ME (c.v.=5.7%). The calculated balance between rumen degradable N and the potential microbial need for N (PBV) varied markedly. The PBV values were closely related to both the ratio of g CP per MJ ME (r=0.99) and to g buffer-soluble CP in the dry matter (r=0.98).
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