María del Socorro Alvarado

Trace elements in native shrubs consumed by white-tailed deer (Odocoileus virginianus) in northeastern Mexico

The contents of Cu, Fe, Mn, and Zn were seasonally determined in the leaves of the native shrubs – Castela erecta, Celtis pallida, Forestiera angustifolia, Lantana macropoda, and Zanthoxylum fagara – that are browsed by the white-tailed deer (Odocoileus virginianus). The study was conducted at the Tamaulipan thornscrub region, northeastern Mexico, between summer 2004 and spring 2006. Leaf tissues were collected from three county sites (China, Linares, and Los Ramones). Mineral contents were measured using an atomic absorption spectrophotometer. All minerals, in all plants, were significantly different among sites, seasons, and years, as well as the double and triple interactions. In general, plants at the Linares site, that had the highest rainfall, had higher trace element content. Moreover, during the second year, all plant species were higher in micromineral content. Furthermore, during summer were also higher. Regardless of spatiotemporal variations, all plants had suitable levels of Fe and Mn to satisfy the adult range of white-tailed deer requirements. The Cu and Zn presented marginal deficiency in some plants especially during dry seasons (winter and spring). Seasonal variations in minerals could be associated to soil water deficits, excessive irradiance during summer, and extreme low temperatures during winter and spring that could have affected leaf development and micromineral concentrations.

Nutritional value of Acacia amentacea and Parkinsonia texana grown in semiarid conditions

In order to evaluate the nutritional value of Parkinsonia texana and Acacia amentacea, two leguminosae species of the Tamaulipan scrubland, Northeastern Mexico, two experiments were carried out: the first tested the effects of season and browse species on chemical composition as nutritional variable to small ruminants; the second tested the effect of the addition of polyethylene glycol (PEG) on fermentation parameters. Foliage samples were collected from three sites. Data of chemical composition were analysed using analysis of variance for a bi-factorial arrangement, whereas the effect of PEG was analysed by a strip plot design. Results of chemical composition were affected by interacting factors season*species as individually they were significantly different (P<0.001). Addition of PEG affected (P<0.001) fermentation parameters. Significantly higher values of neutral detergent fibre (42%), condensed tannins (19%), purines (9 μmol), partitioning factor (PF) (6.1) and gross energy losses (GEL=6.7%) were found in A. amentacea, while P. texana gave higher crude protein (18%), in vitro true organic matter digestibility (82%), metabolisable energy (ME) [2.1 Mcal/kg dry matter (DM)], A (183 mL), c (0.07/h) and L (0.86 h). Addition of PEG increased ME, and affected (P<0.001) fermentation parameters A and c, while purines and PF decreased. Results indicate that chemical composition and fermentation parameters vary according to seasons and species. PEG addition increases the fermentation parameters, which indicates that PEG counteracts the detrimental effects of secondary components of samples. Data suggest that using both species combined could supply necessary nutritional requirements to small ruminants in the Tamaulipan scrubland.