Desempenho, comportamento ingestivo e digestibilidade em novilhas da raça “Pantaneira”, sob dietas com diferentes níveis protéicos

Abstract

The objective of this experiment was to evaluate the performance, feeding behavior and physiology, the apparent digestibility and the blood and urinary parameters of heifers "Pantaneira" breed, fed diets containing different levels of crude protein (CP). Thus, it accompanied the growth of 15 animals, with average weight of 146 kg, kept in confinement and fed with hay and concentrate. The average age of heifers at 18 months and, after 30 days of adaptation, we evaluated the performance during three periods of 28 days, totaling 114 experimental days. The animals were weighed and divided into four batches of similar weights in a completely randomized design, each representative of a heifer experimental unit. Then the animals were allocated to treatment with different protein levels 11, 13, 15 and 17% CP. All diets were iso-energetic with 62% Total Digestible Nutrients (TDN) and fed twice a day will be composed of hay Massai (Panicum maximum cv. Massai) mixed with Stylosanthes leguminous (Stylosanthes guyanensis cv. Campo Grande) and concentrate on a dry matter ratio of 60:40, respectively. Thus, the different protein contents of diets were adjusted in the formulation of the concentrate. It determined the performance of the heifers through the consumption of dry matter in kg/day, percentage of body weight and metabolic function of weight, intakes of crude protein, neutral detergent fiber, acid detergent fiber, the average daily weight gain, feed conversion and increase in height at withers and croup. For this, both the food offered as the remains were collected daily, weighed and sampled, and the samples frozen for 28 days to form a composite sample period per animal. Later, there were chemical analyzes of samples of each period per animal. Measurement of the heifers was carried out at intervals of 28 days, taking a fasting period of 12 hours. At this time the measures were also taken from the heights at withers and croup. Observations of feeding behavior and physiology were made in three batteries of 48 hours each. The verification of nitrogen levels in plasma, urinary nitrogen excretion and the influence of protein level on apparent digestibility of diets were evaluated during the 84 days. In this case, were daily collected and frozen samples of food offered and orts from each cow, the completion of collection of feces and urine have been done in spot and the collection of blood was withdrawn from the jugular vein, at the end of each period 28 days. Fecal production was estimated using the indigestible neutral detergent fiber (NDFi) as marker. The data were interpreted by analysis of variance, Tukey test and regression studies. Gains weight daily were 0.580, 0.610, 0.570 and 0.530 kg/animal/day for treatments 11, 13, 15 and 17% CP, respectively, and thus no significant influence of dietary protein level for the variable gain weight. Similarly there was also no statistically significant differences to the variable intake, except for crude protein, feed conversion and gains in height at withers and croup, with averages of 5.13 kg/animal/day, 10.95, 6.93 cm and 5.4 cm, respectively. For eating behavior was not observed statistical difference in relation to levels of dietary protein on average expenditures were 5.59, 7.87 and 6.04 h/day for eating, ruminating and idling, respectively. The digestibility of dry matter (DMD), organic matter (OMD), crude protein (CPD), neutral detergent fiber (NDFD), acid detergent fiber (DADF), non-fibrous carbohydrates, total carbohydrates, and TDN was influenced by different levels of crude protein, since the ether extract (DEE) and mineral matter (DMM) were not different, with averages of 52.54 and 14.25% respectively, while the concentration of plasma urea and urinary urea loss showed significant differences depending on the levels of protein diets. The different levels of protein did not affect the performance of heifers of "Pantaneira" breed, being recommended diets with 11% crude protein because it's cheaper and meet the requirements of the animals without causing disruptions in performance, changes in ingestive behavior and physiological, and by providing a lower loss of nitrogen compounds in urine.