The trans-10, cis-12 isomer of conjugated linoleic acid is associated with a decrease in milk fat yield. When milk fat contents are low, there is also a lower yield of byproducts such as cheese and butter, so producers receive a lower milk price. However, supplementing the diet of lactating cows with controlled doses of the trans-10, cis-12 isomer of conjugated linoleic acid could reduce energy demand at times when nutrient intake is insufficient. Thus, that energy not used for milk fat synthesis would be used to improve the cow’s energy balance and this, in turn, would lead to increased milk production or changes in milk components.

Alkaline calcareous soils, typical of arid zones, can limit the availability of soil micronutrients for some crops. The aim of this work was to assess micronutrient concentrations in soil and castor-oil plants when soil fertilization involved ammonium sulfate and two types of biosolids. Treatments were designed taking into account three nitrogen (N) sources and three doses of each source plus the control (no fertilization). The N sources were ammonium sulfate (AS), biosolids from wastewater treatment plants with oxidation ponds (OPB), and with activated sludge (ASB). The N doses were 0 (control), 134, 200 and 260 kg∙ha-1. A randomized complete block experimental design with four replicates was used. Dry matter yield and seed oil content rose with increasing N rates. The highest concentrations of Cu and Fe in soil after harvest were obtained with OPB treatments, with means of 0.98 mg∙kg-1 Cu and 5.20 mg∙kg-1 Fe. Results suggest that the biosolids provided the necessary micronutrients for adequate development of Ricinus communis plants without risk of toxicity and pollution.

The Worthen´s Sparrow (WS) (Spizella wortheni) is endemic to Coahuila, Nuevo León and San Luis Potosí, Mexico. Currently, its distribution is restricted, it is found in small populations and it is a species in endanger of extinction. This species is associated with the margins of Prairie dog colonies and has been scarcely studied. During the non-reproductive season (fallwinter), February to March, and September to December 2015 mixed and monospecific flocks of birds associated with WS were monitored in Los Angeles Experimental Ranch, Coahuila, Mexico. In this study, the species associated with WS, its composition and size of the flocks were registered. In addition, foraging habitat characteristics were evaluated. Thirteen bird species were associated with the WS and three types of feeding associations of WS in flocks were identified: 1) large mixed flocks, 2) small mixed flocks and 3) WS monospecific flocks. Fifty-seven percent of the total number of species recorded in the flocks showed seeding food habits similar to those of the WS. In the mixed flocks dominated by WS, this species was the leader or core species, while the flocks dominated by other species were followers. The habitat components associated with the large mixed flocks were height and cover of coyonoxtle plants (Cylindropuntia imbricate Haw.), while those related to the small mixed flocks were height and cover of prickly pear (Opuntia rastrera Weber). The identification of non-breeding WS feeding sites in conserved grasslands may represent a useful tool in designing conservation strategies for WS and its associated species.

Food availability is an important factor in animal populations. Thus, understanding ecological parameters such as abundance and availability results indispensable in establishing appropriate management and conservation strategies of the species. The aims of this study were to determine the abundance of 10 potential preys of three different mesopredators (Leopardus pardalis, Leopardus wiedii and Puma yagouaroundi) found in the Sierra del Abra Tanchipa Biosphere Reserve and to identify changes in relation to the sampling season by means of camera-trapping. The relative abundance index was calculated from independent photographic events. The cottontail rabbit (Sylvilagus floridanus), great curassow (Crax rubra), and the plain chachalaca (Ortalis vetula) showed significant changes in their abundance. The cottontail rabbit was the most abundant species throughout the sampling period. This investigation is the first attempt in evaluating prey abundance in this region; thus, sampling should be continued in order to identify the tendency of the prey’s population and to determine the factors that intervene in its availability