Lactic Acid Bacteria (LAB) are generally recognized as safe. It has been used to increase the shelf-life of fermented products, and its antimicrobial action is based on the metabolites secretions, such as lactic acid, hydrogen peroxide, reuterin, bacteriocins and the likebacteriocins substances. It has been proven that LAB are able to inhibit deteriorating bacteria of raw meat, but improper handling of live cultures could lead to spoilage. So, the use of their bacteriocins, small antimicrobial peptides, could be an alternative. Besides reducing the number of spoilage bacteria, it seeks to inhibit pathogenic bacteria such as Salmonella, enterohemorrhagic Escherichia coli and Listeria. The food industry uses few bacteriocins and now bacterial resistance has been reported. For that reason, the search of novel bacteriocins produced by LAB is a priority. Moreover, the natural microbiota of meat could be a reservoir of LAB.

Objective: To measure the effect of zin injection, during an estrus synchronization protocol, on pregnancy rate in sheep from the “Valle de Mexicali”.Design/methodology/approach: The experimental units were 157 ewes, which wereallocated in five farms (UP): UP1 (n=19), UP2 (n=27) UP3 (n=20) UP4 (n=71) and UP5(n=21). In each farm, the ewes were randomly assigned to one of three treatments:control, z-100 and z-200. The ewes from control groups were subcutaneously injectedwith 4 mL of olive oil as placebo. The ewes from groups z-100 and z-200 weresubcutaneously injected with 100 and 200 mg of zinc oxide. The response variableswere the preovulatory diameter of the largest follicle and pregnancy rate.Results: The differences between experimental groups on diameter of the largestpreovulatory follicle and pregnancy rates were not significant different (p>0.05). Limitations of the study/implications: The ewe’s reproductive response to zincinjection might be affected by the animal mineral status, it is recommended to carry onsupplementation with base on mineral blood concentrations.Conclusion: The subcutaneous injection with 100 or 200 mg of zinc oxide did not affectthe size of the largest preovulatory follicle and pregnancy rate in ewes.

La producción nacional de leche es insuficiente para abastecer el consumo interno y para atender el déficit, por lo cual México ha tenido que incrementar la importación de leche en polvo. Con el fin de estimar el impacto económico provocado por la importación de leche en polvo, se utilizó la Matriz de Insumo-Producto (MIP) Nacional 2013, que permitió medir los impactos mediante los multiplicadores del producto, empleo e ingreso sectorial. Los resultados indican que el incremento de la demanda de leche en polvo por parte de la industria de lácteos en México repercute fuertemente tanto en la cadena de valor de la producción lechera bovina como en las unidades de producción, lo que promueve el abandono de la actividad productiva. Los resultados respaldan la factibilidad de cambiar la situación por la que pasa la ganadería lechera mediante una política pública que integre a los agricultores, ganaderos, industriales, servicios y gobierno, en una cadena de mayor valor compartido, de forma que la acción coordinada y complementaria contribuya a expresar todo el potencial de las empresas que integran la cadena de producción de lácteos.

In sheep production fed high-forage diets, lower quality carcasses are generally observed compared to sheep fed high-concentrate diets. However, the use of concentrates raises the cost of production, so one of the alternatives is to include grazing periods during the fattening of lambs. Therefore, the objective of the study was to determine if the inclusion of grazing periods during the fattening of lambs affects the carcass characteristics. For which, 28 recently weaned lambs (Dorper × Pelibuey × Katahdin) were randomly assigned to one of two treatments: fattening in pen (EC) and fattening in grazing and pen (EPC). In EPC the first 51 days were given morning access to a ryegrass meadow. The characteristics of the carcass did not present a significant difference (p≤0.05) between treatments. Therefore, it is concluded that the inclusion of grazing periods during the fattening of lambs does not affect the characteristics of the carcass.

Salmonella and E. coli are the most important genera in meat (Devlieghere et al., 2004) . Salmonella is related with 93.8 million of worldwide human infection cases, and 155,000 annually deaths (Majowicz et al., 2010) . In the Salmonella infections outbreaks, beef is the most commonly implicated food (Jackson, 2014) . In the same way, E. coli is the most frequent bacteria isolated from meat and its used as indicator of fecal contamination, their pathogenic serotypes (enterohemorrhagic, enteropathogenic, diarrheagenic and verotoxigenic) are responsible for multiple outbreaks of food-borne diseases throughout the world (Hiko et al., 2008) , only in USA is attributed about 40,000 annually deaths, and ground beef is commonly food vector (Russo and Johnson 2003) .The natural microbiota (NM) of meat is a complex ecosystem involving several types of microorganisms, including some LAB populations with inhibitory capacity.Over time, the use of LAB to preserve meat has been proposed, however, most of the suggest bacteria are from fermented products or ATCC strains. Therefore, the objective of this work was to isolate meat native LAB strains from ground beef with antagonistic capacity against two reference bacteria (Salmonella and E. coli) and estimate the inhibition effect of LAB cultures and their CFS, using in vitro techniques. Fifty samples of raw ground beef were aseptically obtained according to Official Mexican Standard No. 109, from butchers and meat retailers in Texcoco de Mora, Mexico, and which were transported and storage (-20 °C) in the laboratory of Livestock Microbiology, Chapingo Autonomous University. Aliquots (25 g) of each sample were placed on sterile bottles and homogenized with peptone solution (225 mL, Bioxon) in a blender for 1 min. Serial dilutions were made with sodium chloride solution 0.85% w/v (saline) and pouring (200 µL) in de Man, Rogosa and Sharpe (MRS, Dibico) agar and incubated 48 h at 37 °C. LAB characteristic colonies were taken and isolated by streaking in MRS agar. All bacteria strains were stored in appropriate media with glycerol (30%) at -20 °C.