title: Levels of supplementation for grazing beef heifers.
abstract: The objective of this experiment was to evaluate the effect of providing different levels of a supplement on the nutritional characteristics and productive performance of heifers on pasture during the rainy-dry transition and dry season in Brazil or tropical area. Thirty crossbred heifers with predominance of Zebu breed were used in a completely randomized experimental design. Treatments consisted of a mineral supplement and 0.5, 1.0, 1.5, or 2.0 kg/animal/d of a protein supplement containing 300 g crude protein (CP)/kg of dry matter (DM). In the rainy-dry transition season there was quadratic effect of the protein supplementation (p<0.10) on daily weight gain (DWG). A linear relationship (p<0.10) was found between increasing supplement intake and intakes of DM, organic matter (OM), crude protein (CP), ether extract (EE), non fibrous carbohydrates (NFC) and total digestible nutrients (TDN). Coefficients of apparent digestibility of CP, EE, and NFC increased linearly (p<0.10) with increasing supplement levels, but there was no effect on the DM apparent digestibility (p>0.10); the microbial efficiency (g CPmic/kg TDN) and the relationship of microbial nitrogen flow with nitrogen intake (g/g nitrogen intake) were negative linear profiles. In the dry season, the descriptive pattern least squares means showed a trend of stabilization of DWG from the supply of 0.98 kg of protein supplement; the intakes of DM, OM, CP, EE, NFC, and TDN showed increasing linear relationship (p<0.10) with protein supplement levels; the means of apparent digestibility coefficients of the different dietary fractions presented a linear-response-plateau (LRP); the microbial nitrogen flow (g/d) showed positive linear profile (p<0.10) for supplementation levels. It is concluded that supplementation improves the productive performance of grazing heifers and that 1.0 kg/d of supplement per animal gives the maximum increment of weight gain.
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Carla Heloisa Avelino
authors: CH
authors: Cabral
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Mario Fonseca
authors: MF
authors: Paulino
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Edenio
authors: E
authors: Detmann
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Sebastião
authors: S
authors: de Campos Valadares Filho
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Lívia Vieira
authors: LV
authors: de Barros
authors: Departamento de Zootecnia, Researchers of INCT-CA, Universidade Federal de Viçosa (UFV), 36570-000, Viçosa, Minas Gerias, Brazil .
authors: Eriton Egidio Lisboa
authors: EE
authors: Valente
authors: Departamento de Engenharia Rural, Universidade Federal do Espírito Santo (UFES), 29075-910, Alegre, Espírito Santo, Brazil .
authors: Maristela
authors: M
authors: de Oliveira Bauer
authors: Faculdade de Agronomia, Medicina Veterinária e Zootecnia, Universidade Federal de Mato Grosso (UFMT), 78060-900, Cuiabá, Mato Grosso, Brazil .
authors: Carlos Eduardo Avelino
authors: CE
authors: Cabral
keywords: Nutritional Parameters; Protein Supplement; Weight Gain