Objective: Evaluate the effect of arrival weight on feedlot growth performance and carcass characteristics of Holstein steers of similar age. Material and Methods: Three hundred calf-fed Holstein steers (age 113 ± 1-day) were distributed in a completely randomly unbalanced design and divided into five categories (105, 112, 117, 123, and 129 kg) of shrunk initial weight (SIW). Calves were weighed on days 1, 112, 224, and 361. Calves were fed steam-flaked corn-based diets. Growth performance and dietary energy were evaluated for each period and the study as a whole (1–361-day). Results: During the rearing period, average daily gain (ADG) increased (linearly effect, p < 0.01) with increasing birth weight. Birthweight was positively associated ( p < 0.05) with feedlot arrival weight ( R 2 = 0.47) and final harvest weight ( R 2 = 0.36). Overall ADG increased ( p < 0.01) with increasing SIW. Dry matter intake increased linearly during the first 224-day but quadratically during the last 137 days. Overall, there was a quadratic effect ( p < 0.05) of SIW on gain-to-feed and observed-to-expected dietary NE, with lower efficiencies (4%) for steers in both the lightest and heaviest SIW. Hot carcass weight, Longissimus muscle area, marbling score, and fat thickness increased (linear effect, p ≤ 0.03) as SIW increased, whereas kidney-pelvic-heart fat and yield-grade were unaffected. Conclusions: The initial arrival weight influences the growth performance, energetic efficiency, and carcass characteristics of Holstein steers of similar age. The effect is more pronounced in the lighter (<112 kg) steers.

Sorghum (Sorghum bicolor (L.) Moench) is cultivated in regions with frequent drought periods and high temperatures, conditions that have intensified in the last decades. One of the most important photosynthetic components, sensible to hydric stress, is maximum quantum yield for photosystem II (PSII, or Fv/Fm). The objective of the present study was to identify sorghum genotypes with tolerance to hydric and heat stress. The treatments were hydric status (hydric stress or non-hydric stress (irrigation)), the plant’s developmental stages (pre or post-anthesis), and six genotypes. The response variables were Fv/Fm; photosynthetic rate (PN); stomatal conductance (gs); transpiration rate (E); relative water content (RWC); damage to cell membrane (DCM) at temperatures of 40 and 45 °C; and agronomic variables. The experiment was conducted in pots in open sky in Marín, N.L., in the dry and hot northeast Mexico. The treatment design was a split–split plot design, with three factors. Hydric stress diminished the functioning of the photosynthetic apparatus by 63%, due to damage caused to PSII. Pre-anthesis was the most vulnerable stage to hydric stress as it decreased the weight of grains per panicle (85%), number of grains per panicle (69%), and weight of 100 grains (46%). Genotypes LER 1 and LER 2 were identified as tolerant to hydric stress, as they had lower damage to PSII; LER 1 and LEB 2 for their superior RWC; and LER 1 as a thermo tolerant genotype, due to its lower DCM at 45 °C. It was concluded that LER 1 could have the potential for both hydric and heat stress tolerance in the arid northeast Mexico.

The study compared the economic results between five groups of Holstein steers with different arrival body weights (ABW) but similar ages in the feedlot. The average ABW were 105, 112, 117, 123 and 129 kg (30, 90, 87, 60, and 30 calves, respectively) with an age of 113 ± 1d. The calves were randomly distributed using an unbalanced design. The calves were weighed upon arrival at the feedlot and subsequently on days 112, 224, and 361 of the study. The calves were fed a steam- flaked corn-based diets. A receiving diet (2.21 Mcal of NEm/kg DM) was provided during the initial 112 days of feeding. From day 112 until harvest all steers received a finishing diet (2.27 Mcal of NEm/kg DM). Because two different diets were used, two partial (day 1 to day 112 and day 113 to day 361), and one full period (day1 to day 361) feeding periods were evaluated. Statistical differences between the final weights of all the groups were observed, which allowed a profit estimation, obtained by subtracting the purchase cost of calves plus the total feed cost from the revenue obtained from the sale of the steers. Overall weight gain and feed intake were higher with increased ABW, feeding efficiency was better for intermediate ABW groups (112 and 117 kg), with the calves with ABW of 112 kg being the most profitable (USD 15.8 more profit than the 117 Kg. group)

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.

Exposure to heavy metals has been documented to induce changes in the expression of plant proteins. Phaseolus vulgaris L., represents a great source of nutrition for millions of people, and is the second most important legume crop. The present study aimed to investigate the effects of Hg stress on germination rate and identify the gene expression profiling of U1-70 kDa by using SDS-PAGE analysis. Seeds of black beans (P. vulgaris L.) variety Jamapa were used. The study was performed in the municipality of Guadalupe in Zacatecas, México; August 2009 to 2011. Embryos were exposed to 10 µmol L-1 HgCl2. Expression and detection of U1-70 kDa was affected by mercury. It was possible to amplify the cDNA for U1-70 kDa in all tested samples, there were also found variations in the mRNA of embryos bean seeds for western blot analysis. Mercury does not affect the germination of bean seeds P. vulgaris L.; there is variation in the expression of the U1-70 kDa protein at different hours of exposure to 10 µmol L-1 of mercury. The presence of U1-70 kDa is identified for the first time in early stages of germination of bean seeds P. vulgaris L.