The accuracy of two simple methods was compared for the prediction of crude protein (CP) content of aboveground plant material of mixed-species composition on abandoned cultivated land in Japan. The first method is based on standard CP values (in g kg )1 dry matter) for individual species (STV method) as listed in the literature. The second procedure (GLM method) was an application of the generalized linear model using the relative above-ground biomass of monocots and legumes, total herbage mass, and day of year. Predictions were made at the quadrat scale, and for surveyed sites based on average of values for five or six quadrats in a single survey. A 'leave-site-out' method was adopted for model validation of the generalized linear model. The observed values of CP content ranged between 21AE5 and 161AE9 g kg )1 dry matter (DM). With the STV method, the values of root mean square error (RMSE indicates average estimation error) were 50AE9 at the quadrat level and 53AE8 at the surveyed-site level (both g kg )1 DM). When a 'leave-site-out' validation was carried out, the RMSE-values for the GLM method were 23AE2 at the quadrat level and 13AE2 at the surveyedsite level (both g kg )1 DM). We therefore propose adoption of the GLM method for the purpose of estimating the CP content in herbage on abandoned sites.

Quantification and prediction of diet selection by animals grazing on forage with mixed-species composition is challenging. The objective of this study was to establish a method to predict the nutritive value of the selected diet in cattle grazing on multi-species plant communities. The nutrient concentrations in the selected diet and forage on offer were evaluated, and the relationship between these nutrient concentrations and the forage utilization rate was analyzed. Shortterm grazing experiments were performed on abandoned cultivated land, without seeding or fertilizer. Before and after each grazing session, the forage was harvested and analyzed to determine concentrations of crude protein (CP), neutral detergent fiber (aNDFom), acid detergent fiber (ADFom) and lignin. The nutrient concentrations on offer and in the selected diet, and the forage utilization rate were calculated based on the apparent disappearance during each experiment. Cattle selected a diet with, on average, 12.0% higher CP and 4.4-13.0% lower aNDFom, ADFom and lignin concentrations than those of forage on offer, and the selectivity depended on the forage utilization rate. The nutrient concentrations in the selected diet were then predicted using only the information on the offered forage. The aNDFom concentration in the selected diet could be accurately predicted, and the concentrations of CP, ADFom and lignin in the selected diet could be roughly predicted. The significant correlations between selectivity for each component and forage utilization rate were used to construct estimation models. Combining the forage utilization rate and the nutrient concentration on offer improved the accuracy of predicting the CP concentration in the selected diet. However, it had little effect on the accuracy of the predictions of aNDFom, ADFom or lignin concentrations in the selected diet.

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