Twenty Pelibuey 3-4 month old and 23.7±3.3 kg body weight male lambs were used in a randomised design to study the effects of daily oral administration of Salix babylonica (SB) extract on dry matter (DM), water intake, average daily gain (ADG), and feed efficiency for 72 days. Animals were divided into four groups fed the same total mixed ration with different doses of SB: 0 (Control), 20 (SB20), 40 (SB40) and 60 (SB60) mL/lamb/d. In vitro gas production (GP) of the same diet fed to lambs as a substrate was measured with different doses of SB (0, 0.3, 0.7, 1.0 mL/g DM). Daily administration of SB to lambs had no effects (P=0.05) on growth performance and DMI (linear effect, P=0.2805; quadratic effect, P=0.3747). Both low and moderate doses of SB (SB40>SB20) tended to increase (linear effect, P=0.4010; quadratic effect, P=0.9166) ADG. The asymptotic GP quadratically increased (P<0.001) with decreased GP rate and with increasing SB extract doses. In vitro GP increased (P<0.05) with advancing of incubation time in all SB doses. During the first 24 h of incubation, 0.3 mL SB/g DM had the highest GP, whereas 1.0 mL SB/g DM quadratically increased (P<0.001) GP. The low dose of SB extract increased ME (linear effect, P=0.024) and short chain fatty acids (SCFA) (linear effect, P=0.023). However, the highest dose quadratically decreased (P=0.02) DM degradability. In conclusion, administration of SB extract at 40 mL/lamb/d tended to increase DM intake, improve daily weight gain in growing lambs with increasing asymptotic in vitro ruminal GP and SB dose. This work is licensed under a Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). ©Copyright J.

The objective of this study was to evaluate the effects of three fibrolytic enzyme products (cellulase (CEL), xylanase (XYL) and a 1:1 mixture of CEL and XYL (MIX)) at three dose levels (0, 1 and 3 lL/0.5 g DM) on the in vitro fermentation of a diet for growing lambs. Bottles were incubated for 96 h at 39 C. A mathematical model was used to estimate the parameters describing the gas production (GP) curve (b, c and L). Dry matter degradability (DMD) and fibre (NDFD and ADFD) degradability were determined at the end of the incubation period. Metabolisable energy (ME) and short chain fatty acids (SCFA) were calculated at 24 h of incubation. The asymptotic GP (parameter b) was affected (p < 0.02) by enzyme product and dose level, with a significant linear response (p < 0.05). Dose level affected ME and SCFA with a significant linear (p < 0.05) and quadratic (p < 0.01) response. The interaction between enzyme product and dose level was significant (p < 0.05) for cumulative GP up to 72 and 96 h of incubation, pH, ADFD and DMD. The results suggest that application of exogenous cellulases has the potential to alter asymptotic GP and degradability of ADF and DM of a diet for growing lambs, but most of the results depend on the interaction between enzyme product and dose level. Future studies are required to determine the ideal combination between enzyme product and dose level for optimal degradation of ruminant feeds. ARTICLE HISTORY

Pelibuey sheep is the main breed in the tropical and subtropical regions of Mexico, and high demand of sheep meat has favored the finishing of lambs in feedlots with diets containing high levels of grains. The objective of this study was to evaluate the effects of exogenous enzymes (EE) and application method on nutrient intake and digestibility and performance of growing Pelibuey lambs. Treatments were based on comparison of two different methods of adding an enzyme product (sprayed on the total mixed ration or applied orally to the lambs) versus control treatment (no added enzyme). Twenty-one Pelibuey lambs, weighing 15.7 kg (SD = 1.8 kg) initial body weight, were individually housed in shaded pens and assigned randomly to one of the three enzyme treatments. At the end of study (lasting for 45 days), three lambs from each treatment were randomly selected and adapted to a pants and harness designed for fecal collection to measure nutrient digestibilities. Total body gain and average daily gain were affected (P < 0.05) by supplemental EE. The application method of EE had significant (P < 0.05) effect on FCE and FCR, but no effects were observed on nutrient intake. Supplemental EE did improve (P < 0.05) the digestibilities of dry matter, organic matter, neutral and acid detergent fiber, but no differences were observed in crude protein digestibility. The application method of EE had significant (P < 0.05) effect on the digestibility of acid detergent fiber. Supplemental EE can improve body weight gain and nutrient digestibilities without affecting nutrient intake in Pelibuey lambs, but the results of feed conversion efficiency and acid detergent fiber digestibility depend on the application method used of the EE.

With the aim to assess the effect of short-term thermal stress on physiological traits of ewes an experiment was designed. Fourteen hair sheep ewes were selected during early reproductive management and randomly segregated in two groups. Control group (CG) with indoor conditions, and an experimental group (EG) under continuous outdoor conditions without shadow accessing during 14 days (d). Respiratory frequency (RF), rectal temperature (RT) and infrared image temperatures were estimated. Traits were measured for 8 d twice a d (9:00 am and 15:00 pm). Environmental temperature and humidity were monitored, and temperature and humidity index was estimated. All physiological and environmental traits showed significantly variation by group and time of measurement (P < 0.001). RT and RF were significantly higher for EG and during pm measurements. Environmental conditions indicated thermal stress conditions for outdoor EG during the afternoon was related ultimately with respiratory mechanism as the main indicator of continuous thermal stress. Head infrared image temperature was a good predictor of body temperature.

ABSTRACT. K-casein (CSN3) gene is of particular interest in goat production due to the eect of its polymorphisms on milk quality and composition. The objective of this study was to assess the genotypic and allelic frequencies in CSN3 gene in the Saanen goat breed and its eect on milk production and some of its compositional traits. Allelic discrimination assays were designed to determine the variants (A, B or C) using qPCR and allelic discrimination method. Allelic frequencies for A, B and C were 0.23, 0.64 and 0.13, respectively. Association analysis indicated that the CSN3 was signicantly associated only with protein percentage (p = 0.006). Results indicated that animals with AC, BB and CC genotypes showed higher milk protein percentage than those with genotype AB. This evidence suggests that genotypes favorable to this associated trait could be included into Saanen goat breeding strategies. Key words: Allelic discrimination, caprine, kappa casein, milk quality RESUMEN. El gen de la κ-caseína (CSN3) es de especial interés debido al efecto de sus polimorsmos sobre la calidad y composición de la leche. El objetivo de este estudio fue investigar las frecuencias genotípicas y alélicas del gen CSN3 en la raza caprina Saanen y su efecto sobre la producción de leche y algunas de sus características de composición. Se diseñaron diferentes ensayos de discriminación alélica para determinar las variantes (A, B y C) mediante qPCR. Las frecuencias alélicas para las variantes A, B y C fueron de 0.23, 0.64 y 0.13, respectivamente. El análisis de asociación indicó que el gen CSN3 esta asociado solamente al porcentaje de proteína en leche (p = 0.006). Los resultados mostraron que los animales con los genotipos AC, BB y CC producen leche con mayor porcentaje de proteína que aquellos con el genotipo AB. Esta evidencia sugiere que los genotipos favorables para la característica asociada podrían incluirse en estrategias de selección asistida por marcadores en cabras de la raza Saanen.Palabras clave: Discriminación alélica, caprinos, kappa caseína, calidad de la leche