Goopy, John P.

Onyango, Alice A.

English

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Digestibility and metabolizable energy intake equations of tropical ruminant forages using nutrient concentration of cattle faecesOnyango, Alice Anyango1,2* and Goopy, John Patrick1,31Mazingira Center, International Livestock Research Institute, Nairobi, Kenya; 2Maseno University, Maseno, Kenya; 3University of Melbourne, Victoria, AustraliaIntroduction- smallholders  use feeds of unknown or highly variable nutritive value undermining proper nutrition - determination of feed intake and accurate nutritive value in grazing animals is resource-intensive - faecal collection and analysis is relatively easy- prediction equations of feed nutritive value based on faecalnutrient concentration would be fast, cheap and routineMethod- in vivo studies with Friesian and/or Boran steers (n = 42):a. Protein-deficit: wheat only and with daily or bi-daily Calliandra calothyrsus supplementation b. Energy-deficit: Chloris gayana at 40%, 60%, 80% and 100% of maintenance energy requirement c. Balanced: tropical grasses (Pennisetum purpureum, Brachiaria brizantha, C. gayana) planted alone or wihLablab purpureus intercrop- determination of feed and faecal proximate nutrient, fibreand energy concentration, DMD, DOMD and MEI- faecal nutrient concentrations from a. and b. regressed against diet DMD, DOMD and MEI; c. for validation dataset- equations were evaluated using root mean square prediction error (RMSE) and mean error (PE)Conclusion- ideally, these equations are developed using a balancedration at maintenance level- however, equations developed from a large database of invivo animal experiments with sub-optimal diets may betterreflect prevailing conditions among smallholders- this is a first step towards development of such a databaseand prediction equationsTable 1. Apparent digestibility (arithmetic mean ± SEM, g/100 g) of diets fed to steers in three in vivo studies carried out at ILRI, Nairobi, Kenya 2014 – 2017 (n = 92)CP = crude protein; DMD = dry matter digestibility; OM = organic matter*Alice Onyango a.onyango@cgiar.org ● Box 30709 Nairobi  Kenya  ● +254 20 422 3000 Nairobi, Kenya ● ilri.org   This document is licensed for use under the Creative Commons Attribution 4.0 International Licence.Date Year.September 2020FindingsILRI thanks all donors and organizations which globally support its work through their contributions to the CGIAR Trust Fund.StudyParameter N-balance Sub-maintenancefeedingTropical grasses feedingDMD 57 ± 1.2 56 ± 0.9 59 ± 0.7OM digestibility 60 ± 1.1 60 ± 1.4 62 ± 0.7CP digestibility 15 ± 3.8 60 ± 1.5 64 ± 0.9Table 2. Equations predicting DMD and DOMD (g/100 g DM)and ME intake (MJ/day) of feedstuffs using faecal nutrientconcentrations from in vivo studies carried out at ILRI, Nairobi2014-2017 (n = 92)DMD, DOMD = apparent dry matter digestibility, digestible organic matter in dry matter; fADF, fCP,fDM, fNDF = faecal acid detergent fibre, crude protein, dry matter and neutral detergent fibrer; ME= metabolizable energy; PE = mean (predicted value – observed value); r = correlation coefficientbetween actual and predicted values; RMSE = square root (mean (predicted value – observedvalue)2)Parameter Equation Adj. R2p-valuer RMSE PEDMD 53 – 0.3fDM + 0.4fNDF – 0.4fADF0.06 0.04 0.32 4.0 ±5DOMD 29 + 0.6fNDF –0.5fADF + 1.0fCP0.10 0.01 0.37 4.0 ±5ME intake 75 – 1.8fDM –1.9fADF + 1.8fCP0.36 <0.01 0.66 7.0 ±22Discussion- equations are weak but may be improved by using data frommore test animals and more varied diets- best predictors (whose analysis is simple, cheap and routine)were faecal DM, CP, NDF and ADF- low PE in digestibility equations demonstrate possibility ofusing cattle’s faecal nutrient concentrations to predictapparent digestibility and ME content of feedstuffsObjective- prediction equations of dry matter digestibility (DMD), digestible organic matter in dry matter (DOMD) and metabolizable energy (ME) intake of tropical feedstuffs using cattle faecal nutrient concentrationsG. Montenegro

Digestibility and metabolizable energy intake equations of tropical ruminant forages using nutrient concentration of cattle faeces

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Digestibility and metabolizable energy intake equations of tropical ruminant forages using nutrient concentration of cattle faeces

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