DIET BOTANICAL COMPOSITION AND RUMEN PROTOZOA OF SHEEP IN BRAZILIAN SEMI-ARID

1Departamento de Zoologia. Universidade Federal de Juiz de Fora. 36036-900 Juiz de Fora-MG. Brazil. *isabelmartinele@yahoo.com.br; Amarta.dagosto@ufjf.edu.br 2Empresa Pernambucana de Pesquisa Agropecuária-IPA. 50761-000 Bongi-PE. Brazil. gladstonrafael@ipa.br 3Departamento de Zootecnia. Universidade Federal Rural de Pernambuco. 52171-900-PE. Brazil. Adanyezoo@hotmail.com; Bangela.batista@pq.cnpq.br


SUMMARY
This study aimed to determine the influence of seasonal variations on diet botanical composition and rumen protozoa of five rumen fistulated Santa Ines crossbred sheep kept in natural Caatinga vegetation pasture, Pernambuco State, Brazil.Samples were collected in July 2005 and January 2006, the respective rainy and dry seasons.Botanic composition of animal diet was determined by analysis of ruminal extrusa.The rainy season diet was composed mainly by herbaceous and grass species (88%), with Herissantia tiubae making up 51.7%.The dry season diet consisted of shrub species (67.4%), mainly Capparis yco (26.3%) and Bauhinia cheilantha (22.3%).Under such conditions variations in protozoa populations were observed, with the higher total concentration (p<0.05) during the rainy season.Populations of Entodinium genus predominated in both seasons, although decreasing (p<0.05) during the dry season, as did the Epidinium and Eremoplastron genera.The Dasytricha, Diploplastron, Eudiplodinium and Isotricha genera had the higher concentrations (p<0.05) in the dry season.

INTRODUCTION
Animal production in Brazil's northeastern semi-arid region is based mainly on pastures of native Caatinga vegetation (Guimarães-Beelen et al., 2006).Caatinga is the low-thorn forest which covers the semi-arid region of North-eastern Brazil, comprising an area of about one million square kilometers.This biome sustains more than 90% of the country's goats and 35% of its sheep production (Araújo Filho et al., 1998).
Both the ovine pasture food habitat and diet composition, are subject to the season changes with local variations in food availability (Molina Alcaide et al., 1997), plant structure characteristics, leaf quality attributes, dry matter content and total protein, and secondary chemical products (O'Reagain, 1993).
In Caatinga pastures, feed availability and quality are influenced by seasonal variations, which are mainly governed by rainfall (Pimentel et al., 1992).In rainy seasons, these pastures contain herbaceous, shrub, and tree species, which have very suitable nutritional characteristics for flock productivity.However, during dry seasons, the herbaceous component practically disappears, reducing the support capacity of the pastures.There is also a considerable reduction in nutritional quality attributes in the shrub and tree food species (Almeida et al., 2006;Araújo Filho et al. 1996).
The occurrence and concentration of protozoa population are influenced by various factors, the principal being the nature of the diet, which in the case of roaming flock farming is influenced by seasonal variations.The vegetation of Caatinga is composed of species rich in tannins and other secondary compounds, whose level change according to phenological state, and that influenced the ruminal microbiota.Condensed tannins of Mimosa hostiles and Bauhinia cheillantha influenced the adhesion conditions, colonization and activity of the microbial ecosystem, and consequently the ruminal degradation of the different dietary fractions (Guimarães-Beelen et al., 2006).Thus, the objective of this study was to evaluate how the seasons affect diet botanical composition and rumen protozoa ciliate populations of crossbred Santa Ines sheep in natural Caatinga pastures from semi-arid regions of Pernambuco State, Brazil.

MATERIALS AND METHODS
The experiment was conducted between January 2005 and January 2006 with five 10-12 months old Santa Ines wethers with fistulated rumen.Animals were kept in a 37 hectare area of Caatinga pasture (Latitude 8º03'38" S, Longitude 37º13'32" W) belonging to the experimental farm of Empresa Pernambucana de Pesquisa Agropecuária, Sertânia, PE, Brazil; this vegetation was the only food source.The sheep had access to the pasture from 07:00 a.m. to 05:00 p.m. when they were corralled.They were kept in the experimental area for the whole year without any supplements, receiving only water and mineral mixture in dust ad libitum.Precipitation was monitored daily throughout the year.All the sampling was performed in July 2005 (30 samples) and January 2006 (26 samples), months which fall in the periods known as rainy and dry seasons, respectively.
Species found in the experimental area were collected and sent to Universidade Federal Rural de Pernambuco, Department of Botany for identification.There were 280 observation points and species samples were grouped as herbaceous, shrub, and tree according to Allaby (2004).
A set of spot ruminal content samples was obtained before the animals had access to the pasture and then at 2, 4, 6, 8, and 10 h after the animals began feeding to obtain an average, in order to decrease the effects of diurnal changes in population density.A maximum of two samplings were made per day so as to minimize the effects on animal foraging time.These samplings were made one time for each season.Each sample consisted of 20 ml rumen contents, which were immediately fixed in a 1:2 formol mixture (Dehority, 1984).Total and differential quantification of ciliate protozoa were performed in a Sedgewick-Rafter chamber, using a counting grid in one of the eyepieces to quantify the number of ciliates in 50 fields, and then in another 50 fields after rotating the chamber 180°.Total number of ciliates per ml of content was calculated by multiplying values found by 80 and 20.These values correspond to the total counting  (Dehority, 1984).Ciliates were stained with three drops of lugol solution instead of brilliant green (D'Agosto and Carneiro, 1999).Ciliate identification was based on Ogimoto and Imai (1981).
For rumen fistula sample extraction, animals were fasted for 15 h, then released into the pasture for one hour, and recaptured for proceeding manual of complete rumen emptying.The contents were stored in plastic recipients so that they could be returned to the rumen after sample collection.These samplings to analyse extrusa were made after the samplings of ruminal content to protozoal analysis.The diet botanical composition was determined as Heady and Torrel (1959).
The total and differential mean numbers of ciliate protozoa were compared between seasons using the Student's T test (p<0.05).The BIOEST 2.0 program was used to analyze data (Ayres et al., 2000).

RESULTS
Seventy eight species were identified in the experimental area, 34 herbaceous, 9 cactus, 22 shrubs, and 13 trees (table I).The families that presented high number of species were Leguminosae (15), Euphorbiaceae (9), Malvaceae (7) and Poaceae (6), contributing approximately to 46% of total species observed.The species identified in animal diets (table II), in the rainy season 87.8% were herbaceous while in the dry season 67.4% were shrub and 12.7% tree.
Ciliate protozoa population concentrations varied between rainy and dry seasons (table III).The Eodinium and Enoploplastron genera were only seen in rainy season samples.In the dry season, Entodinium, Epidinium, Eremoplastron genera and mean number of total protozoa decreased (p<0.05),whereas Dasytricha, Diploplastron, Eudiplodinium and Isotricha genera showed increases (p<0.05).Pimentel et al. (1992) andAraújo Filho et al. (1996) reported that sheep are basically dicotyledonous herbaceous plants consumers in Caatinga pasture.However, they are considered moderately selective with high feeding flexibility depending on the time of year, and feed availability and quantity because during dry seasons, they use bush and tree biomass (Araújo Filho et al., 1996;Pimentel et al., 1992).They even select the bush and tree species according to the nutritional value of the available biomass, taking into account the seasonal variations in total protein, dry matter, and acid and neutral detergent fiber levels from various species which make up the Caatinga vegetation, and which are used as forage (Almeida et al., 2006;Araújo Filho et al., 1996;Araújo Filho et al., 2002).This is confirmed by the increased levels of Bauhinia cheilantha in the animal's diet during the dry season, the use of which as a foodstuff has been recommended due to its high nutritional value (Araújo Filho et al., 1998;Guimarães-Beelen et al., 2006).

DISCUSSION
The variations in sheep's diet composition due to seasonality, and feeding flexibility to the available vegetation have also been seen in studies on sheep and goats in other semiarid locations in South Africa (Du Toit, 1998), Spain (Molina Alcaide et al., 1997), Mexico (Lopez-Trujillo and Garcia-Elizondo, 1995) and India (Sharma et al., 1998).
In this study dietary botanical composition was strongly influenced by the seasons which consequently determined protozoa occurrence and concentration.In this way variations in these protozoa concentrations could be linked to seasonal variations or even to the phenological state of the plants used as forage, both being able to trigger changes in soluble sugar and fiber levels which are used by different protozoa populations, according to the enzyme activity shown by each one (Bonhomme-Florentin et al., 1978;Manella and Lourenço, 2004;Nogueira Filho et al., 1992).
The significant reduction in Entodinium concentration in dry seasons, when most of the vegetation is in an advanced phenological state corroborates observations by Manella and Lourenço (2004) and by Nogueira Filho et al. (1992), and can be attributed to the reduction in total protein content, a reduction in solu-Table III.Mean concentration (x10 4 ) and composition (%) of ciliate protozoa per ml of rumen contents from crossed sheep Santa-Ines wethers in natural Caatinga pasture. (Concentração   média (x10 4 ) e composição (%) de protozoários ciliados, por mililitro de conteúdo ruminal de ovinos mestiços Santa-Inês em pastagens naturais de Caatinga).

Rainy season
Dry ble sugars and increase in fiber due to the level of plant maturation.Also Entodinium ciliates have lower cellulolytic activity (Takenaka et al., 2004), therefore their populations are at a disadvantage when ruminants are fed fiber-rich diets.
Variations in rumen protozoa concentrations are also attributed to nutritional quality of plants available in pastures (Bonhomme-Florentin et al., 1978) and available dietary protein content, with higher protein content diets tending to produce higher ciliate concentrations (Franzolin et al., 1997).Protein content is known to vary with the phenology of the forage plant, and in characteristic Caatinga species the higher protein levels are seen in the vegetative stage (Araújo Filho et al., 2002), which coincides with the rainy season when the highest number of protozoa are seen.
Diplodiniinae ciliates, Diplodinium and Eudiplodinium, presented high fibrolytic activity and play an important role in rumen fiber digestion (Takenaka et al., 2004;Williams and Coleman, 1992).Possibly due to their fibrolytic activity, presented significant increases in concentration during the dry season, when the vegetation have higher fiber level (Araújo Filho, 2002).Guimarães-Beelen et al. (2006) observed that the tannin concentration in plants used in Brazilian semi-arid pastures influences degradability, microbial adhesion, and microbial enzymes.So although various Caatinga plant species have nutritional characteristics which make them potential forages, one must take into account their effect on ruminal microbiota.Using these native species in ruminant diets, it may have unsatisfactory results, not from the lack of productively adequate nutritional characteristics, but because they possess antinutritional factors such as tannins, saponins, lignins, and mimosins which are toxic to rumen microrganisms (Kamra, 2005;McSweeney et al., 2001;McSweeney et al., 2002).

CONCLUSION
The botanical dietary composition of sheep grazing on natural Caatinga vegetation has seasonal variations, with herbaceous species predominating in rainy seasons.In dry seasons, the diet consists mainly of shrub species, with this flexibility linked to food availability; this is linked to seasonal variations, which influence the ciliate protozoa concentrations in the rumen, which amounts vary depending on analyzed population.

Table II .
Seasonal botanical composition (%) of food eaten by crossbred Santa Ineswethers grazing on natural Caatinga pasture.