Influence of cutting time and N fertilization on the nutritive value of timothy, 1: Crude protein content, metabolizable energy and energy value determined in vivo vs. in vitro
1988
Lindgren, E. | Lindberg, J.E. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Husdjurens Utfodring och Vaard)
All together 61 digestibility trials with timothy, harvested at different stages of maturity of 1st or 2nd cuts and different levels of applied N, were used to assess an optimal strategy for harvest in relation to the feeding of high-yielding dairy cows. The daily change in crude protein content of the 1st cut was mainly dependent on the level of crude protein content, the latter beeing highly influenced by the rate of N fertilization. By imposing a lower optimal feeding limit of 11.5 MJ ME/kg organic matter and 16% crude protein in the organic matter it was necessary that first cut was taken 2-4 days after heading and that at least 100 kg N per hectare was applied in the spring. The daily decline in energy value was fairly constant at 0.1 MJ ME. Lower optimal ME content of regrowth was reached about 60 days after the first cut. The protein content was by then only 12 % of organic matter at the highest rate of N fertilization (90 kg N/hectare directly after 1st cut). To reach a more adequate protein content, an increased application of N is preferable to a shorter period of regrowth with regard to total yield of organic matter per hectare. Prediction of the energy value by means of the one-stage in vitro method commonly used in Sweden showed good agreement with in vivo results for the first cut but tended to overestimate the energy value of regrowth. This difference was, however, not statistically significant.
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