In production systems of prickly pear fruit and prickly pear cactus, significant amounts of pruned material, which could be used as an ingredient in animal feeding, is generated. The aim of this study was to measure the nutrient content, fermentation kinetics and in vitro digestibility of eleven cultivars of cladodes of prickly pear cactus. The fermentation was measured indirectly using the gas production technique, where 500 mg of DM substrate (prickly pear cactus cultivars) were placed in amber glass flasks of 125 mL with 90 mL of ruminal inoculum under a continuous flow of CO 2 . Flasks were hermetically wrapped up with a rubber stopper and a metal ring, and were placed in a water bath at 39°C. The fermentation gas pressure was measured using a monometer at 0, 2, 4, 6, 8, 12, 16, 20, 24, 32, 38, 50 and 72 h incubation. Results show that the chemical composition ranged between (g kg -1 DM): 64 and 160 g kg -1 dry matter (DM), 137-293 g kg -1 DM ash, 52-101 g kg -1 DM crude protein, 3-22 g kg -1 DM ether extract, 251-393 neutral detergent fiber and 132-192 acid detergent fiber. The gas volume was different (p \ 0.05) among cultivars, with the Red Vigor cultivar having the largest volume at 378 mL g -1 DM. The highest volume of gas was produced during the first 24 h in on average 67 % of the total produced. The in vitro DM digestibility displayed values of up to 82 % in the Roja Pelota cultivar. It can be concluded that the cladodes of prickly pear cactus from different cultivars can be used in animal feed for its good rumen fermentation characteristics.

The present work describes a novel, simplified high-performance liquid chromatography (HPLC) method for evaluation of vitamin D3 and its 25-hydroxy metabolite in blood plasma. The retrieval of the analytes from the blood plasma matrix is based on a single-step extraction using acetonitrile. The method is specific, sensitive, and ensures good reproducibility. The recovery of the analytes, precision, and reproducibility obtained using the present approach gave results comparable to or better than more complex, laborious, and time-consuming procedures. This method is suitable for evaluation of the host's vitamin D physiological status, as well as for rapid analysis of blood plasma samples in suspected cholecalciferol toxicity. With a significantly shortened time of analysis (10 minutes), the present method allows the possibility for processing of a large number of samples rapidly, efficiently, and at a low cost.

Traceability in the Mexican dairy processing industry was studied to understand drivers behind its implementation. A questionnaire was applied to 33 plants. Data were analyzed using univariate and tabulate procedures of SAS. All plants operated Hazard Analysis and Critical Control Points, ISO or other food safety system. The 85.7% of respondents had traceability operating. Motivations to implement traceability were legal responsibility, and risks/worries of product recall; the enterprise problems were lack of supplier and customer feedback, and ability to manufacture new products; among benefits were regulatory requirements met, enterprises' image and reduced product recall/withdrawal. Economic and market reasons are important for traceability systems of the Mexican dairy processing industry. PRACTICAL APPLICATIONS Given the importance of traceability in domestic and international markets, especially the quality of raw materials used in the food processing sector, this study reports the first baseline information for the Mexican dairy processing sector. The results will allow improving the traceability systems in order to have a better market positioning both in the domestic and international markets. A higher number of Mexican suppliers could be incorporated into this food chain, because the most important quality requirements to be met will be available for this group of enterprises that process dairy products. Another impact is to determine the consumer preference, and a better positioning in foreign markets that require traceability systems in dairy products.

. 2004. Effect of supplementing high levels of vitamin D 3 on calcium homeostasis of steers fed barley-based finishing diets. Can. J. Anim. Sci. 84: 81-89. The objective of this study was to evaluate the effect of supplementing high levels of vitamin D 3 to steers fed barley-grain-based finishing diets on Ca metabolism. Fifteen Hereford steers (607 ± 12 kg) were individually penned and fed at 0800 and 1600 with a ration consisting of 90% barleygrain-based concentrate and 10% barley silage [dry matter (DM) basis]. Steers were randomly assigned to one of three treatments: 0, 2.5 or 5 million IU (MIU) of vitamin D 3 steer -1 d -1 for 7 d. Daily blood samples were obtained for measurement of serum for total and ionized Ca, parathyroid hormone (PTH) and calcitonin and plasma for vitamin D 3 and 25(OH)D 3 . Data were analyzed by repeated measures analysis and single degree of freedom contrasts. Feed intake was depressed relative to control animals by 18 and 37% for the 2.5 and 5 MIU D 3 treatments, respectively. Relative to controls, total and ionized Ca increased (P < 0.05) by 8 and 19% and 6 and 18% for the 2.5 and 5 MIU D 3 treatments, respectively. Serum PTH concentrations were reduced (P < 0.05) by vitamin D 3 feeding with the greatest reduction seen with animals fed the 5 MIU treatment. Calcitonin values were not (P > 0.05) affected. Relative to controls, plasma vitamin D 3 concentrations increased (P < 0.05) in a quadratic fashion over time with vitamin D 3 supplementation, while that of 25(OH)D 3 increased (P < 0.05) in a linear fashion. It was concluded that the increase in serum calcium was stimulated by a rise in plasma vitamin La vitamine D3 réduit la concentration sérique de PTH (P < 0,05), l'administration de 5 MUI entraînant la plus forte baisse. La concentration de la calcitonine n'est pas affectée (P > 0,05). Comparativement aux sujets témoins, le supplément vitaminé augmente la concentration plasmatique de la vitamine D3 (P < 0,05) de façon géométrique dans le temps, alors que la concentration de 25(OH)D3 s'accroît (P < 0,05) de manière linéaire. On en conclut que la hausse de la concentration de vitamine D3 dans le plasma et la hausse résultante de celle de 25(OH)D3 entraînent un relèvement du calcium sérique, le 25(OH)D3 exerçant une influence sur l'absorption du calcium directement ou indirectement par la synthèse de 1,25(OH)2D3.

The effect of six genotypes (Zebu = Z, European Brown Swiss = EBS, Holstein = H, Z × EBS, Zebu × American Brown Swiss = ABS, Z × ABS, Z × H) on carcass and meat characteristics of young bullocks finished under feedlot conditions was tested. The Z × ABS bullocks had the highest (P = 0.001) average daily gain. The highest (P = 0.017) final liveweight was observed with Z × ABS > EBS > H genotypes. The ribeye area was larger (P = 0.012) for EBS bullocks. Both H and EBS bullocks had lowest (P = 0.001) physiological maturity; although the H bullocks had higher (P = 0.006) pelvis and heart fat values. The best (P = 0.014) conformation was obtained with the Z × ABS and Z × EBS genotypes. The greatest amount of marbling (P = 0.001) was obtained with the H genotype. In general, the crossbred genotypes showed better feedlot performance and carcass characteristics, and it seems that Holstein breed could have a an advantage from the marbling score point of view.