Nguyen Xuan Ba

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.

Impact of Forage Fertilization with Urea and Composted Cattle Manure on Soil Fertility in Sandy Soils of South-Central Vietnam

Increased production in smallholder beef systems requires improved forage management. Our objective was to evaluate the effects of composted cattle manure and mineral nitrogen (urea) application on soil fertility and partial nutrient balances in plots established to Brachiaria cv. Mulato II in south-central coastal Vietnam from 2010 to 2013. A randomized complete block design was implemented on six farms (blocks), with five rates of composted cattle manure (0, 4, 8, 12, and 24 Mg DM/ha per yr) and three urea rates (0, 60, and 120 kg N/ha per yr) in a factorial design. Soil was analyzed before and after the experiment. Compost increased soil pH, organic matter, Ca, Mg, and Mn. The effect of compost and urea applications on postexperiment soil fertility depended on preexperiment soil fertility for K, P, S, Mg, Zn, Mn, Cu, and organic matter, suggesting that the ability to maintain soil fertility depends on the interaction between soil organic and inorganic amendments and existing soil fertility. Highest farm yields were also achieved on farms with higher preexperiment soil fertility levels. Negative partial nutrient balances for N, P, and K suggest that yields will not be sustainable over time even for the highest fertilization inputs used in this experiment.

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.

Structure and impact of cattle manure trade in crop-livestock systems of Vietnam

Cattle manure value chains play important biological and economic roles in smallholder crop-livestock systems in developing countries, but relative to other livestock products our understanding of the nature and impact of manure sales is limited. In regions with an active manure trade, farmers face a choice between manure use on-farm and sales, which affects nutrient flows and participant incomes. We analyzed the manure value chain operating in south-central Vietnam as an example of the function and role of manure trade in crop-livestock systems. Lowland cattle farmers sell manure through a network of chain participants, including small-scale collectors, lowland and highland traders, to pepper, coffee, dragon fruit and rubber farms in the central highlands and southeast coast. We collected and summarized quantitative data (e.g., manure-related labor, manure transactions, and fertilizer and manure use) gathered in semi-structured interviews with value-chain participants [lowland cattle owners ( n = 101), traders ( n = 27) and end users ( n = 72)]. Lowland cattle owners were selected by stratified random sampling, and subsequent participants were identified in preceding interviews. One key finding concerns the seasonality of the manure value chain: most manure flowed between February and August (lowland dry season and period of peak highland demand) from lowland communes to highland coffee and pepper farms for use as organic soil amendments. Fewer sales occurred, at a lower price, to southeast coastal dragon fruit farms and rubber companies. Value addition to manure occurred via drying, bagging, collection, transport and composting. The presence of local traders facilitated market sales for smallholder cattle owners, and prices through the value chain generally reflected costs for value addition. The geographic distribution of cattle relative to agricultural land influenced the flow of manure, with net outflows from regions with higher animal density to regions with lower density and higher value crop production. Manure trade was an important source of supplementary income for farmers and a primary livelihood activity for traders. Value chain participant net incomes ranged from near US

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

100 yr -1 for lowland farmers to over US

Effects of Amount of Concentrate Supplement on Forage Intake, Diet Digestibility and Live Weight Gain in Yellow Cattle in Vietnam

13,000 yr -1 for traders, and returns to labor were just over US

Amount of Cassava Powder Fed as a Supplement Affects Feed Intake and Live Weight Gain in Laisind Cattle in Vietnam

0.50 h -1 for lowland farmers and US

Systems of cattle production in south central coastal Vietnam

2 h -1 for traders. The quantitative information generated during our descriptive assessment provides an important first step toward manure value chain improvement, indicates survey methods that can be applied in other areas, and identifies next steps necessary to evaluate chain evolution and resilience.

Practice on improving fattening local cattle production in Vietnam by increasing crude protein level in concentrate and concentrate level

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.