Intake and Digestibility of Native and Exotic Grasses Fed Ad libitum to Djallonke Sheep in South Benin

Native （Andropogon gayanus, Panicum maximum and Pennisetum purpureum） and exotic grasses （Brachiaria ruzi：iensis, Panieum maximum cv. C1 and T58） consumed in tropical humid zone were evaluated by estimating their voluntary intake and in vivo digestibility. The measurements were performed with 4 male Djallonke sheep （28 kg LW） fed ad libitum in metabolic cages, during a 10-days in vivo trial, preceded by a 14-days accommodation period. Each grass was studied at 3 stages of development. The samples （distributed grasses, refusals and faeces） were analysed for organic matter （OM）, crude fibre （CF）, neutral detergent fibre （NDF）, acid detergent fibre （ADF）, acid detergent lignin （ADL） and crude protein （CP） contents. Voluntary digestible organic matter intake （VDOMI） and voluntary digestible crude protein intake （VDCPI） were calculated （in g kg ^-1 LW075） as synthetic parameters to compare the grasses. The chemical composition of the distributed forages varied significantly （P 〈 0.001） between species or cultivars and development stages. After 4-5 leaves per tiller stage, CP contents decreased in all species and lowest in native species. Andropogon gayanus was the most l ignified species at any stage of development. At the end of the rainy season, Pennisetum purpureum leaves and Brachiaria ruziziensis had the highest CP. For all the grasses, CP contents were higher （and CF contents lower） in the consumed material, compared to the offered forages, showing thereby the high selectivity by the sheep. Dry matter intake, OM and CP digestibility varied greatly （P 〈 0.001） between forages and development stages with high interactions between these factors （P 〈 0.001）. Voluntary digestible organic matter intake and VDCPI were the highest （P 〈 0.05） for native Panicum maximum and Pennisetum purpureum. There was a relationship between digestibility and intake parameters, and ADL content of the grasses seems to be an important factor determining at least digestibility.

Effects of supplementation of Brachiaria brizantha cv. Piatá and Napier grass with Desmodium distortum on feed intake,digesta kinetics and milk production in crossbred dairy cows

This study was planned to analyse the basis that make Brachiaria species with greater feeding value than Napier grass(Pennisetum purpureum) for lactating dairy cows.Forty lactating crossbred cows were stallfed on Brachiaria brizantha cv.Piata or Napier grass cv.French Cameroon supplemented(mixed on fresh matter basis) or unsupplemented with Desmodium distortum, a forage legume.All cows were fed on fresh matter basis under small-holder farming conditions.Results showed that B.brizantha cv.Piata had higher contents of dry matter(DM), crude protein(CP) and organic matter(OM), but lower contents of neutral detergent fibre(NDF) and acid detergent fibre(ADF) than Napier grass(P < 0.001).The legume supplementation increased intakes of CP and metabolizable energy(ME; P < 0.001), with higher effect on cows fed B.brizantha cv.Piata than on cows fed Napier grass.Average daily milk yield was lower on diets based on Napier grass than those based on B.brizantha cv.Piata(P < 0.001).The retention time of the particle phase of digesta in the digestive tract was longer on Napier grass(83.1 h) than on B.brizantha cv.Piata(62.8 h)(P < 0.05).It was concluded that in dairy cows, legume supplementation of B.brizantha cv.Piata increases nutrient intake, hence resulting in higher milk yields than supplementation of Napier grass.

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N_(2)O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N_(2)O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^(-1),and N 5.6 g kg^(-1))sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N_(2)O emissions,N_(2)O derived from fertilizer,soil ammonium(NH_(4)^(+))and nitrate(NO_(3)^(-)),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH_(4)^(+)content between the UR and UR+NI treatments,probably because of soil mineralization and NO_(3)^(-)produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N_(2)O emissions in UR(0.51±0.12 mg N_(2)O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH_(4)^(+)and NO_(3)^(-)production.Additionally,it was found that N_(2)O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N_(2)O emissions only if a substantial N surplus exists in soils with high organic matter content.

Accuracy of two optical chlorophyll meters in predicting chemical composition and in vitro ruminal organic matter degradability of Brachiaria hybrid,Megathyrsus maximus, and Paspalum atratum

The objective of this study was to determine the accuracy and reliability of 2 optical chlorophyll meters:FieldScout CM 1,000 NDVI and Yara N-Tester, in predicting neutral detergent fibre(NDF), acid detergent fibre(ADF), acid detergent lignin(ADL), acid detergent insoluble nitrogen(ADIN) and in vitro ruminal organic matter degradability(IVOMD) of 3 tropical grasses. Optical chlorophyll measurements were taken at 3 stages(4, 8 and 12 weeks) of regrowth in Brachiaria hybrid, and Megathyrsus maximus and at 6 and 12 weeks of regrowth in Paspalum atratum(cv. Ubon). Optical chlorophyll measurements showed the highest correlation(r = 0.57 to 0.85) with NDF concentration. The FieldScout CM 1,000 NDVI was better than the Yara N-Tester in predicting NDF(R^2 = 0.70) and ADF(R^2 = 0.79) concentrations in Brachiaria hybrid and NDF(R^2 = 0.79) in M. maximus. Similarly, FieldScout CM 1,000 NDVI produced better estimates of 24 h IVOMD(IVOMD_(24 h)) in Brachiaria hybrid(R^2 = 0.81) and IVOMD_(48 h) in Brachiaria hybrid(R^2 = 0.65) and M. maximus(R^2 = 0.75). However, these prediction models had relatively low concordance correlation coefficients, i.e., CCC >0.90, but random errors were the main source of bias. It was,therefore, concluded that both optical chlorophyll meters were poor and unreliable predictors of ADIN and ADL concentrations. Overall, the FieldScout CM 1,000 NDVI shows potential to produce useful estimates of IVOMD_(24h) and ADF in Brachiaria hybrid and IVOMD_(48 h) and NDF concentrations in M. maximus.