Nguyen Huu Van

Understanding interactions between forages and concentrates is important for formulating feeding strategies for growing cattle in central Vietnam

Three experiments were conducted in Vietnam to measure responses in forage intake and diet digestibility to concentratefeedingingrowingcattle.Thebasaldietinallexperimentswasgrass(elephantgrass,Pennisetumpurpureum,in experiments 1 and 2; native grass in experiment 3) fed at 1.25% liveweight (DM basis) during the day and rice straw fed ad libitum at night. The concentrate in experiment 1 was cassava powder plus urea. In experiments 2 and 3, a formulated concentratecomprisedofmaize,ricebran,fishmeal,ureaandsaltwasused.Theconcentrateswereofferedat~0.3,0.7,1.3 and 2.0% liveweight in each experiment, and a zero concentrate treatment was also included. Effects of the amount of concentrate on substitution rate of concentrate for forage and on diet neutral detergent fibre (NDF) digestibility were measuredtoassessinteractionsbetweenfeeds.Substitutionratewashigh(0.5--0.7kgDMreductioninforageintakeperkg DMsupplementconsumed)andnotaffectedbyamountofsupplementfedinexperiment1.Inexperiments2and3,therewas nosubstitutionatthelowestintakeofsupplement,butitsubsequentlyincreasedwithamountofsupplementconsumed,toa high of 0.3--0.5kg DM reduction in forage intake per kg DM supplement consumed. The cassava powder supplement markedly decreased dietary NDF digestibility (from 62 to 41%), whereas the formulated concentrate only reduced NDF digestibilityby11and8%unitsinexperiments2and3,respectively.ItwascalculatedthatdepressionsinNDFdigestibility wouldreducetheestimatedmetabolisableenergycontentofthebasalforageby1--3.6MJ/kgDMatthehighersupplement intakes. The importance of these results in making decisions on tactical feeding systems tofatten cattle in central Vietnam is discussed.

Evaluation of a Nutrition Model in Predicting Performance of Vietnamese Cattle

The objective of this study was to evaluate the predictions of dry matter intake (DM) and average daily gain (ADG) of Vietnamese Yellow (Vang) purebred and crossbred (Vang with Red Sindhi or Brahman) bulls fed under Vietnamese conditions using two levels of solution (1 and 2) of the large ruminant nutrition system (LRNS) model. Animal information and feed chemical characterization were obtained from five studies. The initial mean body weight (BW) of the animals was 186, with standard deviation ±33.2 kg. Animals were fed ad libitum commonly available feedstuffs, including cassava powder, corn grain, Napier grass, rice straw and bran, and minerals and vitamins, for 50 to 80 d. Adequacy of the predictions was assessed with the Model Evaluation System using the root of mean square error of prediction (RMSEP), accuracy (Cb), coefficient of determination (r2), and mean bias (MB). When all treatment means were used, both levels of solution predicted DMI similarly with low precision (r2 of 0.389 and 0.45 for level 1 and 2, respectively) and medium accuracy (Cb of 0.827 and 0.859, respectively). The LRNS clearly over-predicted the intake of one study. When this study was removed from the comparison, the precision and accuracy considerably increased for the level 1 solution. Metabolisable protein was limiting ADG for more than 68% of the treatment averages. Both levels differed regarding precision and accuracy. While level 1 solution had the least MB compared with level 2 (0.058 and 0.159 kg/d, respectively), the precision was greater for level 2 than level 1 (0.89 and 0.70, respectively). The accuracy (Cb) was similar between level 1 and level 2 (p = 0.8997; 0.977 and 0.871, respectively). The RMSEP indicated that both levels were on average under- or over-predicted by about 190 g/d, suggesting that even though the accuracy (Cb) was greater for level 1 compared to level 2, both levels are likely to wrongly predict ADG by the same amount. Our analyses indicated that the level 1 solution can predict DMI reasonably well for this type of animal, but it was not entirely clear if animals consumed at their voluntary intake and/or if the roughness of the diet decreased DMI. A deficit of ruminally-undegradable protein and/or a lack of microbial protein may have limited the performance of these animals. Based on these evaluations, the LRNS level 1 solution may be an alternative to predict animal performance when, under specific circumstances, the fractional degradation rates of the carbohydrate and protein fractions are not known.

Evaluation of the Small Ruminant Nutrition System model (SRNS) for goat production in Vietnam

Applied nutrition models that can accurately predict goat performance under different feed intake regimes play a crucial role in developing improved feeding strategies. The primary objective of this study was to evaluate the ability of the SRNS model to predict the dry matter intake (DMI), average daily gain (ADG), nutrient digestibility, and faecal output characteristics of Vietnamese goats.The SRNS version 1.9.4468 (http://nutritionmodels.tamu.edu/srns.html) was used to simulate animal intake and performance of two local Vietnamese goat breeds for four feeding experiments.The model under-predicted DMI (kg/d) for most treatments (R2 = 0.70) and under-predicted ADG (g/d) for all treatments (R2 = 0.69) (Table 1). Nutrient digestibility and faecal outputs were generally under-predicted. Coefficients of determination for DM (0.94) and CP digestibility (0.93) were high.Our evaluation indicated that the SRNS model can predict the DMI and ADG of Vietnamese goats when nutritive values of the feeds are known. The regression equations developed in this study could be used to adjust the outputs of the SRNS model to predict the results of feeding systems.