Forage use and availability for white tailed deer Odocoileus virginianus thomasi (Artiodactyla: Cervidae) in an experimental unit of Campeche, Mexico. In Campeche state, 122 Wildlife Conservation and Management Units have been recently conformed. In these units, eventhough the white tailed deer Odocoileus virginianus thomasi is a game species, no studies on its diet have been undertaken. The objectives of this work were to estimate the botanical composition of the diet and its seasonal change, to determine forage availability, carrying capacity and stocking rate of O. virginianus thomasi. The study was conducted in the experimental unit of Colegio de Postgraduados in Campeche, Mexico, from October 2010 to May 2012. The diet was determined through microhistological analyses of the white tailed deer feces by the use of reference material. Forage availability was determined through the Adelaide´s method; the stocking rate, using the grazing pressure factor; and carrying capacity considering forage availability and 35% of utilization efficiency. In this experimental unit, the deer diet included 40 species belonging to15 families. The highest species richness ocurred during the rainy season with 29 species. However, deers preferred shrubs during all seasons, and herbaceous species during the rainy season. The diet composition, forage availability, carrying capacity and stocking rate varied throughout the year. Carrying capacity ranged from 0.04 to 1.08deer/ha. Additional studies are required to detail about the composition of the diet, habitat availability and use throughout its geographical range, and to detail on nutritional and health aspects.

Sixteen adult sheep fed on different proportions of barley grain and straw (60:40, 45:55, 30: 70 and 15:85) were used to obtain regression equations for prediction of dry matter (DMI) and digestible organic matter (DOMI) intake, dry matter (DMD), organic matter (OMD), crude protein (CPD) and neutral detergent fi bre (NDFD) digestibility, and proportion of straw consumed (% straw) from the NIRS analysis of the faeces. All equations had coeffi cients of determination in calibration higher than 0.65, except that for the prediction of NDFD (R 2 = 0.11). The coeffi cients of determination in cross-validation were much lower, with only DMD, OMD and % straw predictions showing values higher than 0.70.

Taking into account the relationship between rainfall and temperature, 64% of the Spanish territory can be classified as arid (25%) or semiarid (39%). In these areas, vegetal surface includes permanent pastures and drought grasslands (34.0%), fallows (13.4%), winter cereals for grain production (21.2%), forage crops (mainly lucerne, and winter cereals harvested as green forage; 2.6%) and woodland hills. Ruminants in these zones account for 15.4 million head, of which nearly 80% are sheep. In the present paper, the possibilities of integrating sheep in cropping systems are discussed, and an alternative based on the use of permanent sowed prairies (lucerne), self-sowing annuals (Wimmera ryegrass) and winter cereals (barley) will be analysed.

An experiment was carried out to examine the effect of increasing the proportion of Wimmera ryegrass hay in a lucerne hay-based diet on net transfer of nutrients to the intestine, and on the disappearance of n-alkanes in the reticulo-rumen and the hindgut of sheep. Following a latin square design, four adult ewes were fed 1:0, 0·33:0·67, 0·67:0·33 and 0:1 proportions of legume and grass. Increasing the proportion of ryegrass in the diet linearly decreased the intake of DM (P¼0·017), organic matter (P¼0·021) and N (P¼ 0·001). However, neutral-detergent fibre intake was not affected (P¼ 0·148), nor was its digestibility coefficient (P.0·10). Diet had no effect on duodenal flows of nutrients (P.0·10), although the proportion of N intake (NI) recovered at the duodenum as non-NH 3 N (NAN) increased linearly with Lolium rigidum in the diet (P¼0·002). Full recovery of NI as NAN was achieved at NH 3 concentrations in the rumen below 110 g/l. Microbial N contribution to NAN varied in a quadratic manner (P, 0·05) with the proportion of grass in the diet, although efficiency of microbial synthesis was not affected (P. 0·10). Duodenal recovery of consumed n-alkanes was not affected by diet and was complete for those present in higher concentrations in the forages. Isolated rumen bacteria contained significant amounts of n-alkanes, contributing to the duodenal flow of these hydrocarbons in variable proportions depending on the diet consumed.Key words: n-Alkanes: Duodenum: Nutrients: Rumen bacteria Net transfer of ingested protein to the duodenum (in the form of microbial protein, undegraded plant protein and endogenous protein) is complete only when the plants contain approximately 210 g crude protein (CP)/kg digestible organic matter (DOM) or less (1) . Above this threshold, there is net loss of protein with potentially large amounts of ingested N lost as NH 3 across the rumen wall. Legumes usually exceed this CP content, and hence including a grass in the diet might minimise N losses. The amount of protein reaching the abomasum when animals are fed different grass/legume mixtures (2) is largely unknown, with most of the work having been carried out with silages and dairy animals (3 -5) . Lucerne and Wimmera ryegrass (Lolium rigidum) are important resources of integrated sheep farming systems in many semi-arid areas of the world, but there is no information about net transfer of N to the duodenum when these are fed in combination.The use of n-alkanes as markers of diet selection and intake in grazing animals (6,7) is based on evidence that faecal recovery is related to chain length (6 -8) , which allows correcting for the incomplete faecal recovery of a determined hydrocarbon by dosing a selected alkane of similar chain length. Incomplete recovery of n-alkanes in faeces can be due to losses in the reticulo-rumen, in post-ruminal compartments or in both. Studies dealing with ruminal disappearance of n-alkanes are scarce (8 -11) , but they suggest that losses in the reticulo-rumen are minimal, if any. If this is th...