title: Intake, digestibility and rumen dynamics of neutral detergent fibre in cattle fed low-quality tropical forage and supplemented with nitrogen and/or starch.
abstract: The objective of this work was to evaluate the effects of nitrogenous compounds and/or starch supplementation on the intake, digestibility and rumen dynamics of neutral detergent fibre (NDF) in cattle fed low-quality tropical forage. Four crossbred heifers (Holstein x Zebu) with a body weight 231.9 +/- 15.5 kg and fitted with ruminal cannulae were used. The forage fed to the animals consisted of low-quality signal grass (Brachiaria decumbens Stapf.) hay, with an average crude protein (CP) level of 51.6 g/kg, on a dry matter (DM) basis. Four treatments were evaluated: control, without supplementation; supplementation with nitrogenous compounds (CP of the roughage was raised to 100 g/kg), on a DM basis; supplementation with starch at a ratio of 200 g/kg DM of roughage; and supplementation with nitrogenous compounds and starch as described above. A mixture of urea, ammonium sulphate and albumin was used as a source of nitrogenous compounds at a ratio of 4.5:0.5:1.0. The experiment was carried out according to a 4 x 4 Latin square design in a 2 x 2 factorial arrangement. There was a positive effect of the nitrogenous compound supplementation on the DM and NDF intake (P < 0.01). In contrast, starch supplementation decreased forage intake (P < 0.10). Nitrogen supplementation increased the digestibility coefficient of DM and NDF (P < 0.05). Supplementation with nitrogen and starch together increased the microbial assimilation of nitrogenous compounds in the rumen (P < 0.05). We observed that nitrogen supplementation increased the estimated weighted degradation rate of NDF by 14.8%, whilst starch supplementation decreased this rate by 32.5%.
authors.affiliation: Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36571-000, Brazil.
authors.forename: Marjorrie A
authors.initials: MA
authors.lastname: Souza
authors.forename: Edenio
authors.initials: E
authors.lastname: Detmann
authors.forename: Mário F
authors.initials: MF
authors.lastname: Paulino
authors.forename: Cláudia B
authors.initials: CB
authors.lastname: Sampaio
authors.forename: Isis
authors.initials: I
authors.lastname: Lazzarini
authors.forename: Sebastião C
authors.initials: SC
authors.lastname: Valadares Filho
mesh_terms: D000481:Allantoin / Q000652:urine; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001938:Brazil; D002417:Cattle / Q000502:physiology*; D003124:Colorimetry; D003401:Creatine / Q000652:urine; D004043:Dietary Fiber; D019587:Dietary Supplements; D004063:Digestion / Q000187:drug effects / Q000502:physiology*; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D005243:Feces / Q000737:chemistry; D005504:Food Analysis / Q000379:methods; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D012417:Rumen / Q000378:metabolism*; D013213:Starch / Q000378:metabolism / Q000494:pharmacology; D014329:Tropical Climate; D014508:Urea / Q000097:blood / Q000652:urine
chemical_list: D004043:Dietary Fiber; D000481:Allantoin; D014508:Urea; D013213:Starch; D003401:Creatine; D009584:Nitrogen
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