Potencial produtivo de novilhas da raça “pantaneira” alimentadas com fenos de baixa qualidade

Abstract

The cattle "Pantanal" breed is a national genetic resource in the Brazilian Pantanal. Originally from the Iberian Peninsula in Europe. These animals had to modify their phenotypic characteristics to adapt to climatic conditions and nutritional distinctive characteristic from Pantanal Plain, reproducing and multiplying freely for centuries with little human intervention. Although cattle breed have did dominate the scene in the past, now this genetic group is in extinction risk. Moreover, as the zootechnical information of the "Pantanal" breed of cattle are scarce, it is necessary to make evaluations about the ability of these animals to utilize forage, especially that of low quality. Thus, the objective of this assay was to evaluate the productive potential of the Pantanal heifers fed different forages, by measuring the intake, digestibility and weight gain, and to generate information that could help in keeping this species, in order that it becomes a germplasm bank in situ. It was used fifteen heifers, with average body weight of 298.0 kg kept in confinement and fed diets containing forage and concentrate in the 60:40% proportions in dry matter, respectively. Were used as forage hay of Brachiaria brizantha cv. Piata, Panicum maximum cv. Massai and Stylosantes capitata/ macrocephala cv. Campo Grande, thus, it was tested two grasses and one legume. Diets containing similar protein levels were offered twice daily at 7:00 and 16:00. It was determined the performance of animals through the dry matter intake, expressed in kg/day, percentage of body weight and in terms of metabolic weight, feed conversion, weight gain and average daily gains in height at withers and croup. Heifers were weighed at intervals of 28 days after a fasting period of 12 hours. On the same day it was measured heights at withers and croup. The digestibility of nutrients, glucose concentrations and plasma urea and urinary nitrogen loss was mensuared. The data were interpreted by analysis of variance and Tukey test at 5% probability. The different forage did not affect the performance of the animals, which showed average body weight of 336.9 kg and a weight gain of 460 g/day. There was not statistical differences in the variables consumption, feed conversion and gains in height at withers and croup with averages of 6.77 kgDM/animal/day, 15.4, 2.0 cm and 2.0 cm, respectively. The apparent digestibility of dry matter, organic matter, crude protein and carbohydrate were higher for animals fed hay Piatã. Not having, however, differences in the digestibility of non-fiber carbohydrates and mineral matter. Since the digestibility of acid detergent fiber was lower for diets containing legume Estilozantes. On the other hand, the digestibility of neutral detergent fiber was statistically different between the forages with greater use of Piata, followed by Massai and Estilozantes. The serum levels of glucose and urea as well as the excretion of urea-N, they were statistically similar means of 71.03 mg/dl, 6.71 mg/dl and 154.75 mg/kgPC, respectively. The forages testeds did not influence the intake, average daily gain and body growth of heifers "Pantanal" breed. Among the forages testeds (Brachiaria brizantha) cv. Piatã presented better apparent digestibility when compared with the others forages.