RESUMO
Background: The search for productivity increase in finish ruminants is related with the intensification of production. The use of concentrated feed in finish lambs can determine a profitable product and quality, wich reachs ideal weight in a short time. However, the addition of concentrated feed can cause a shift in the whole rumen ecosystem, and as a result, having animals more susceptible to metabolic disorders. As protozoa have their growth stimulated or inhibited by dietary factors, it becomes important to quantify and evaluate its activity in response to diets for ruminants. Thus, using measurements of the number of protozoa in the rumen fluid, we are able to make early diagnosis of possible metabolic disorders, as well as adjustments in ration formulations. The objective of this study was to evaluate the concentration and activity of protozoa in rumen of sheep in a feedlot diet, and validate an adaptation of the technique Dehority for counting of protozoa in the rumen fluid. Materials, Methods & Results: It were utilized 5 crossbred Texel x Corriedale ewes not pregnant, not lactating, with approximately 18 months old and with average weight of 50.73 ± 4.38 kg. The females were kept confined, receiving water and ration ad libitum in individual feeders. Ewes were fed twice (8:30 and 16:30) daily with a diet aiming to provide the DM intake equivalent to 3.5% of body weight. The roughage supply was 60% of DM, divided into Alfalfa hay (Medicago sativa) and Tifton 85 (Cynodondactylon), plus supplementation with commercial concentrate of 40%. Before the experimental period, we conducted a pre-trial adaptation period (21 days in length). Pre-prandial ruminal fluid collections were performed before the AM feeding, at intervals of seven days, during 35 days (Day 0 to Day 35 of the experiment), in a total of six collections. The rumen fluid was collected through oro-ruminal probe and the contents stored in sterile containers for immediate realization of sedimentation and flotation tests, methylene blue reduction test and ruminal pH.The values found in the rumen evaluations are in agreement physiological parameters for sheep. The average number of protozoa in rumen fluid in the range of 35 days was similar to other studies. Discussion: In this study, supplementation of concentrate at 1.4% of BW did not induce ruminal acidosis, as well as other changes in the analysis of rumen fluid, demonstrating an appropriate relation concentrate/roughage in the diet. Furthermore, the supply of forages (Alfalfa hay and Tifton) at 60% of the diet (DM basis), or 2.1% of BW, was crucial to maintaining stable rumen pH. However, we observed an increase (P < 0.05) in the number of protozoa associated with the course of the experimental period. Moreover, this study we observed that even after a adaptation period of 21 days, the average number of protozoa in rumen fluid continued with a significant gradual increase. Using an alternative methodology was possible to validate a technical adaptation to the counting of protozoa in rumen fluid proposed by Dehority. In conclusion, diets based on alfalfa hay and Tifton, plus supplementation with concentrated promote a gradual increase in the number of ruminal protozoa in confined ewes, without any interference in other markers of rumen activity.