Caracterização da vegetação e da dieta de ovinos em área de Caatinga no Sertão de Pernambuco

Abstract

The work was conducted at the experimental station of Sertânia - IPA with the objective of characterizing the vegetation at the caatinga, to evaluate the effect of fistula and hour of collection on the botanical and chemistry composition and in situ digestibility of dry matter, neutral detergent fiber and crude protein of the vegetation. The experiment was conducted between September 2004 and July 2005. Ten castrated sheep of the Santa Inês breed, five fitted with permanent ruminal cannula and five with esophageal cannula, were used. Samples were collected from both cannulas at 7:00 and 14:00. Sheep had free access to water and mineral mix. Eighty two species, belonging to 33 families were identified. Species were classified as 34 herbaceous, 24 shrubby, 14 arboreal and 10 cactáceas. Species belonging to euphorbiaceae, malvaceae, leguminosae and poaceae were the most dominant ones. The available biomass for the herbaceous component varied between 1022 kg DM/ha (September, 2004) to 401 kg DM/ha (JuIy, 2005), while the conlponent shrubby varicd between 1078 kg DM/ha (september/2004) to 545 kg DM/ha (january/2005). Samples collected from both cannulas revealed 39 species with an average of 20 monthly species. There was a significant effect (P <0,05) of collection time on the botanical composition and the fractions of the plants sclected by the sheep. Leaf was the most consumed fraction, corresponding the 55% of feed consumed. Percent of stem was affected by the interaction between month and hour of collection (P <0,05). There was not effect of the place of fistula or of time of collection on botanical composition of the diet. However, the interaction of month of collection, fistula placement and time of collection influenced (P <0,05) botanical composition and proportion of fractions of plant consumed. The selectivity index varied during the study for several species being directly related lo the ingestive behavior of the sheep. The rnonth in that occurred the collection influenced the chemical composition of the diet significantly. The percentage of dry matter, mineral matter, crude protein, ether extract, neutral detergent fiber, acid detergent fiber, insoluble protein in neutral detergent, insoluble protein in acid detergent, total carbohydrate, no fibrous carbohydrate, total phenols. total tannins and condensed tannins varied from 11,99 to 25,28%; 10,92 to 14,44; 10,64 to 17,19%; 2,95 to 4,77; 54,83 to 63,14%; 39,40 to 46,62%; 49,74 lo 57,95; 28,52 to 39,15; 65,40 to 72,73; 5,47 to 12,86%; 0,37 to 0,52%; 0,16 lo 0,28%; and from 1,28 to 6,24%, respectively. Potential degradability (%), fraction potentially degradability (%), degradation rate ofthe fraction potentially degradability (%/h), soluble fraction (%) and effective degradability for passage rate of 2 and 5%/h varied from 48,25 to 64,63; 35,77 to 47,78; 4,60 to 13,40; 9,74 to 18,13; 43,28 lo 55,71 and 37,60 to 47,27 for the dry matter; from 36,43 to 54,34; 33,28 to 50,38; 3,84 to 8,42; 2,16 to 4,41; 29,21 to 36,54; 23,02 to 33,33 for the neutral detergent fiber and from 62,13 to 77,24; 35,44 to 56,09; 5,37 to 14,36; 20,21 to 31,49; 55,84 to 67,49; 45,74 to 59,99 for the protein, rcspectively. The biomass readiness varies along the year. The herbaceous stratum is constituted mainly by poaceae, being Aristida purpusii mez. Chase the component that stayed in the pasture during the whole year. The main components of the shrubby straturn were Cnidoscolus sp., Sida galheirensis ulbr, Croton sonderianus mueli. arg., Herisanthia tiubae k.schum. bri, Cordia leucocephala moric. Plants selected sheep was very diversified with malvaceae and poaceae being the most important families. The chemical composition and “in situ” digestibility of sheep’s diet in caatinga is influenced by the month of evaluation. Although the high crude protein level in diet. part of that protein is unavailable for lhe animal for being linked to acid detergent fiber. The diet of the sheep to semi arid region presented low “in situ” digestibility of dry matter, neutral detergent fiber and crude protein. Ruminal cannula instead of esophageal cannula can be used to characterize the diet consumed by small ruminant.