Carlos Fernando Aréchiga Flores

Performance and nutrient digestion of lambs fed incremental levels of wild cactus (Opuntia leucotrichia)

In a performance trial, 50 intact Rambouillet×Dorper male lambs (19±2.8 kg), were randomly assigned to experimental diets containing 0, 10, 20, 30 or 40%, Opuntia leucotrichia (O. leucotrichia; dry matter basis). At day 91 animals were slaughtered for carcass and meat quality evaluation. In trial two, five ruminal cannulated Rambouillet male rams were used in a digestion study. Dry matter intake, average daily gain and feed efficiency of lambs decreased (P<0.05) generally with increasing levels of O. leucotrichia. Carcass dressing was increasing as O. leucotrichia was augmented. Water intake decreased as consumption of O. leucotrichia increased. Crude protein was digested higher (P<0.05) in lambs fed 40% diet than other lambs. Ruminal pH and ammonia-N were not significantly different among treatments. Inclusion of O. leucotrichia on feedlot lamb diets is a good option for production systems if this resource is available.

Efecto del nivel de infestación de Varroa destructor sobre la producción de miel de colonias de Apis mellifera en el altiplano semiárido de México

The aim of this study was to determine if the mite Varroa destructor affects honey yields of honeybee (Apis mellifera) colonies in Mexicos semiarid high plateau. A total of 32 colonies with different degrees of mite infestation that had not been treated with miticides in the previous two years were used. Honey yields and mite infestation levels in adult bees were recorded and data were subjected to correlation analyses.

Evaluación de un sistema de enfriamiento aplicado en el periodo seco de ganado lechero durante el verano

In order to determine some physiological responses 60 d prepartum and production responses postpartum to a cooling system in summer, 24 multiparous Holstein cows were allocated to two groups: one group with (n=12) and a second group without (n=12) cooling. Cooled cows showed a lower (P 0.05). Reproductively, only total conception rate was higher (P<0.05) in cooled cows than in non-cooled cows (100 vs 63.6 %). Non-cooled cows showed a 42 % culling rate, while no cow was culled in the cooled group (P<0.05). An economic analysis showed a net profit of 75 dollars cow/year for the cooling system. Results show that cooling dry cows reduce heat stress, that resulted in higher fat-corrected milk and milk fat production in the subsequent lactation and in higher economical benefits for dairy producers.

Respuesta fisiológica y productiva de novillos engordados con un sistema de enfriamiento a espacio abierto en un clima árido y seco

Evaluation of the effects of an open space cooling system on weight gain, respiration rate and serum thyroid hormone (T3 and T4) levels in feedlot steers was done using 60 Holstein steers (344 kg) allotted randomly in two treatments: a control with only shade in the corral (n=30), and a cooling with an open space cooling system (n=30). Daily maximum temperature-humidity index (THI) ranged from 82 to 88 during the 12-week study period. The open space cooling system consisted of a fan with 2.4 m diameter blade that displaced 1,416 m3 of air per minute and had a 90o oscillation range, and sprinklers. The fan was installed at 8 m distance on the south side of the shade. Water discharge was 12 L per minute over a 7 h period. Body weight and thyroid hormone levels were measured every two weeks and respiration rate twice a week (1400). Data were analyzed by repeated measures, including initial weight as a covariate. Daily weight gain was different (P<0.05) between the cooling treatment (1.43±0.091 kg/d) and the control treatment (1.25±0.091 kg/d). Respiration rate was lower (P<0.05) in steers in the cooling treatment (94±0.74 breaths per minute) than in those in the control treatment (111±0.74 breaths per minute). Levels of T3 were higher (P<0.05) in the cooling treatment (1.7±0.042) than in the control (1.5±0.042). Levels of T4 were similar between the cooling (79.3±1.82 ng/ml) and control (78.2±1.82 ng/ml) treatments. Use of this cooling system improved production performance and comfort in feedlot Holstein steers in a hot, dry climate.