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The activity of antioxidant enzymes in different apricot (Prunus armeniacaL.) cultivars, resistant or susceptible to Plum pox virus (PPV), was analyzed during the years 2002 and 2003. Resistant cultivars showed higher activities of catalase (CAT), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) than susceptible cultivars. Only CuZn-SOD isozymes were detected in the apricot cultivars. However, no correlation was observed between this isozyme pattern and the resistance to PPV. On the other hand, PPV-resistant apricot cultivars could have a greater capability for elimination of H2O2and recycling of ascorbate-glutathione cycle, and they have at least two of these enzymatic activities (CAT, APX and DHAR) over the average. In contrast, this response was not observed in the susceptible cultivars. All these data suggest that the activities of CAT, APX and DHAR could be used as biochemical markers of sharka resistance in apricot.

The growth of Holstein heifers in the campesinodairy systems in the highlands of Mexico was evaluated in three feeding strategies. Thirty-three heifers from 11 farmers, grouped according to strategy, were weighed every 14 days for 28 weeks. The live weight change over each 14-day period was estimated by individually regressing live weight over period, taking the regression coefficient as an unbiased estimate of live weight change. Regression coefficients were analysed as a randomized design with feeding strategies as treatments. Strategies were as follows: S1: grazed or cut pasture all year, maize silage and maize straw in the dry season, and 1.0–1.5 kg concentrate/heifer per day. S2: maize straw in the dry season, cut pasture forage, grazing of native grass, weeds from maize fields, and 1.0–1.5 kg concentrate/heifer per day. S3: maize straw in the dry season, grazed native grasses and weeds in the rainy season. Live weight gains were: S1, 0.511 kg/heifer per day; S2, 0.271 kg/heifer per day; and S3, 0.252 kg/heifer per day. Despite the better gains in S1, they are 24% below recommendations, arriving to service at 20 months of age. Not rearing their replacements may be a better alternative for campesinofarmers under current economic conditions.

The on-farm evaluation of three feeding strategies for smallholder campesino dairy herds was undertaken in the highlands of Central Mexico with cooperating farmers: traditional, alternative and intermediate feeding strategies. All three incorporated grazing of cultivated pastures, but concentrate use was 4.0 and 7.0 kg per cow per day in the rainy and dry seasons respectively for the traditional feeding strategy, 3.3 for the alternative feeding strategy in both rainy and dry seasons and 5.0 and 9.0 kg per cow per day in the rainy and dry seasons respectively for the intermediate feeding strategy. Feeding during the dry season was based on maize straw in the traditional strategy, on pasture complemented with maize silage in the alternative feeding strategy, and with some maize silage but mostly maize straw in the intermediate feeding strategy. The trial ran between 25 September 1996 and 24 September 1997, divided by season into four, thirteen-week periods. Milk yields were recorded once per week, and live weight and body-condition score, every 28 days. Three cows per strategy that completed each period were blocked according to stage of lactation and used for the statistical analysis of a split-plot design with feeding strategies as main plots and weeks as split-plots. Overall mean milk yields were 15.5±2.05, 13.4±2.43 and 12.4±2.37 kg milk per cow per day for alternative, intermediate and traditional feeding strategies respectively, with significant interactions (P<0.05) for autumn, winter and summer. The alternative feeding strategy (with over 50% less concentrate) produced milk yields 0.24 and 0.38 higher than the intermediate and traditional feeding strategies in the dry season. In the rainy season, milk yields with the alternative feeding strategy (30% less concentrates) were 0.09 and 0.16 higher than the other two strategies. Margins per day of family labour were: alternative feeding strategy US$36.48 per day, intermediate feeding strategy US$9.22 per day and the traditional feeding strategy US$9.11 per day, although in the case of the last two there were two family members in charge of the dairy herds. Results demonstrate the successful integration of grazed pasture and maize silage for the efficient production of milk, and provide evidence on the productive use of limited campesino land resources in the face of unviable economic conditions for maize grain production.

Twenty-four Dorper × Pelibuey ram lambs (32.19 ± 0.69 kg initial BW and 5 mo of age) were housed in individual pens during a 31-d feeding period and then slaughtered to determine the effects of zilpaterol hydrochloride (ZH) supplementation on productive performance, carcass characteristics, and wholesale cut yields. Lambs were assigned to 4 treatments (n= 6) under a randomized complete block design, where initial BW was used as the blocking factor. Treatments consisted of offering a basal diet and 3 different daily doses of ZH: 0 (control), 0.1, 0.2, and 0.3 mg/kg BW. All data collected were analyzed with ANOVA using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC). Means were separated with a PDIFF STDERR statement. Significance was declared at P< 0.05 and tendency when 0.05 < P< 0.10. Final BW (P= 0.02) and ADG (P= 0.04) were greater for lambs that received 0.2 mg/kg BW. Supplemental ZH tended to improve DMI (P= 0.008) and the ADG:DMI ratio (P= 0.078). Water intake was lower (P< 0.01) in lambs supplemented with ZH. Zilpaterol hydrochloride supplementation did not affect carcass characteristics such as hot and cold carcass weight, dressing, KPH, conformation, fat thickness, carcass and leg length, thorax depth, and pH of LM at 45 min; however, cooling loss (P= 0.06) and pH at 45 min (P= 0.06) showed a trend to increase as ZH supplementation increased. Wholesale cut yields were not affected by ZH supplementation. Percentage of head was greater (P= 0.043) in lambs treated with ZH. LD area increased (P= 0.01) with ZH addition. Percentage of blood presented a trend (P= 0.051) of decreasing with ZH supplementation. Also, the liver decreased in size (P< 0.05) for treatments in which ZH was included. In conclusion, using a daily ZH dosage of 0.2 mg/kg of BW produced the best productive performance and carcass characteristics in hair-breed rams.

The effect of hydroalcoholic extracts of fruits and leaves from Caesalpinia coriariaon the egg hatching inhibition of Haemonchus contortusand Haemonchus placeiwas evaluated. The tested concentrations were 25.0, 12.5, 6.2, 3.1, and 1.5 mg/mL; likewise, a 4% methanol solution and albendazole were used as negative and positive controls, respectively. The results were analyzed under a 2 × 2 × 6 factorial arrangement of treatments under a completely randomized design, and for the mean comparison, Tukey's test was used. The mean (LC50) and maximum (LC90) lethal concentrations were estimated with Probit analysis of SAS. The hydroalcoholic leaf extract as well as the fruit extract had ovicidal activity (Table 030; P< 0.05), inhibiting hatching in around 100% with the concentration of 25.0 mg/mL. The fruit extract had better egg hatching inhibition (P< 0.001) in H. contortusand H. placeithan the leaf extract. The LC50for the fruit extract were 1.63 and 3.91 mg/mL and for the leaf were 3.98 and 11.68 mg/mL for H. contortusand H. placei, respectively. The main compounds contained in both extracts were tannins, flavonoids, gallic acid, and ethyl gallate. It is concluded that the hydroalcoholic extracts from mature fruits and leaves of C. coriariahave the ability of inhibit the egg hatching of H. contortusand H. placei.