The present study aims to establish the relationship between chemical composition and in vitro methane (CH₄) production of high Andean grasses. For this purpose, eight species were collected in dry and rainy seasons: Alchemilla pinnata, Distichia muscoides, Carex ecuadorica, Hipochoeris taraxacoides, Mulhenbergia fastigiata, Mulhenbergia peruviana, Stipa brachiphylla and Stipa mucronata. They were chemically analyzed and incubated under an in vitro system. Species such as A. pinnata and H. taraxacoides were characterized by high crude protein (CP. 124 g/kg DM) and low neutral detergent fiber (NDF. 293 g/kg DM) contents in both seasons, contrary to Stipa grasses. This same pattern was obtained for H. taraxacoides, which presented the highest values of gas production, organic matter digestibility (DOM), metabolizable energy (ME) and CH₄ production (241 mL/g DM, 59% DOM, 8.4 MJ ME/kg DM and 37.7 mL CH₄/g DM, on average). For most species, the content of CP, acid detergent fiber (FDA) and ME was higher in the rainy season than in the dry season, which was the opposite for CH₄ production (p ≥ 0.05). In general, the nutritional content that most explained the behavior of CH₄ production was the NDF content (R² = 0.69). Grasses characterized by high NDF content produced less CH₄ (R = −0.85).

Two experiments were conducted to determine a prediction model of the net energy (NE) requirement from the net energy for maintenance (NEm) and the retained energy (RE) by the comparative slaughter technique and its validation, and the metabolizable energy was determined using the nitrogen-corrected total excreta collection method. A completely randomized block design was used, and in the validation, the error (%) and the analysis of the concordance correlation coefficient (CCC) were determined. In each experiment, two replicates were used (five chickens per replicate) for each treatment. The experiment included 370 Cobb 500 male chickens (one day old), distributed in two experiments (190 in the first and 180 in the second), fed with six diets, considering a basal diet (corn + soybean meal), from which was substituted on a percentage basis (weight/weight) for the ingredients frequently used in chicken feed (corn, wheat by-product, soybean meal, fish meal and soybean oil) with three feeding levels: ad libitum (AL), 85 % (AL) and 70 % (AL) in both experiments. To determine NEm, the relationship between RE and metabolizable energy intake (MEI) was established using simple linear regression. The second study estimated and validated the NE with the proposed model, where the NEm was calculated with simultaneous equations obtained from the basal diet of Study 1. The values of NEm/W^0.75, EMm/W^0.75, and the efficiency k, showed similar values among diets (p<0.05). The MEI was greater in the diet with soybean oil than others, the RE represented 45.6 % of the metabolizable energy (ME) consumed and was the greatest in the diet with soybean oil (p0.05), with an adequate linear relationship (R² = 0.996) and low error (4.01 %), the CCC was high (0.993) and a υ of 1.02. The proposed net energy model (NE(kcal/day)=79.66·W^0.75+RE), allows to estimate with precision and accuracy the NE requirement in broiler chickens.

The use of full-fat soybean meal (FSBM) in feeding guinea pigs would be a good alternative to improve dietary protein, but little is known about the use of their nutrients in this animal species. This study aimed to determine the nutrient digestibility and energy digestible of FSBM and the effects of its incorporation in guinea pigs' diets. Thirty male guinea pigs were used, aged two (15 animals) and 10 weeks (15 animals). A basal diet was used, from which the weight/weight substitution was carried out at proportions of 15 and 30 % inclusion of FSBM. The digestibility of nutrients in the diets differed between ages, being higher in adults than in growing (p<0.001). The digestibility of DM and nutrients of FSBM was high, being higher in adult guinea pigs (76.94 % DM, 77.56 % OM, 82.34 % CP, 86.87 % EE, and 60.96 % CF) than growing (71.78 % DM, 72.35 % OM, 66.24 % CP, 60.37 % EE and 50.41 % CF) (p<0.001). The digestible energy was 3375 and 3093 kcal.kg-1 DM for adult and growing guinea pigs respectively (p<0.001). FSBM meal is a good option for feeding growing and adult guinea pigs due to its high nutritional value and digestibility. Keywords: Cavia porcellus, Glycine max, digestibility, energy, nutritional value.

Se realizaron dos estudios con el objetivo de determinar la energía digestible y el coeficiente de digestibilidad de la materia seca y proteína del pulimento de arroz; y evaluar el efecto de cinco niveles de polvillo de arroz (Oryza sativa) para reemplazar el salvado de trigo en dietas para cuyes en crecimiento (Cavia porcellus) sobre parámetros productivos. En el estudio I se utilizaron 12 cuyes machos tipo I con un peso vivo promedio de 875 g, se determinaron los coeficientes de digestibilidad y energía digestible del polvillo de arroz por el método indirecto, con la técnica de recolección total. El coeficiente de digestibilidad de la materia seca fue 80,33%, proteína 75,51%, energía 78,06% y la energía digestible del polvillo de arroz fue 3,77 Mcal/kg MS. En el estudio II se utilizaron 80 cuyes machos mejorados tipo I, de 14+2 días de edad y peso promedio de 441 g, para evaluar el efecto de cinco niveles de pulimento de arroz: 0%, 4,5%, 7,5%, 15% y 30% en sustitución del salvado de trigo, en dietas de crecimiento de 49 días. Como resultado, se observó que no hay diferencias significativas en el aumento de peso, el consumo de alimento, la conversión alimenticia y el rendimiento de carcasa al reemplazar el salvado de trigo con polvillo de arroz. La inclusión de pulimento de arroz en niveles superiores al 7,5% afecta la respuesta productiva en cuyes.

The extent to which energy and protein (CP) levels can be reduced without impacting productivity in slow-growing chickens remains undetermined. The treatments were conducted to evaluate the effect of dietary CP (17.5, 19, and 20.5%) and energy (2850-2950 kcal ME/kg) on slow-growing chickens using an ideal protein concept at a high altitude (3200 m). We used a total of 144 slow-growing chickens. The experiment lasted for eight weeks, a total of six treatments with three replicates each and eight chickens per replicate were used. Body Weight Gain (BWG) showed differences only in the growing chickens, for CP and the energy × CP interaction, the lowest BWG was at 17.5% CP (2850 kcal ME/kg) and 19.0% at 2950 kcal ME/kg (p<0.01) and higher for other interactions. BW and BWG maximized at 19% CP (2850 kcal ME/kg) and 17.5% CP (2950 kcal ME/kg). Feed intake was lower at 17.5 and 20.5% CP for respectively energy levels (p0.05). Abdominal fat increased with high energy (p<0.05). At both energies, maturity weight was highest at the lowest CP; growth rate (kg/d) was raised with higher dietary CP (2850 kcal ME/kg). The time to maximize growth rate decreased with higher CP at low energy but remained constant at high energy. There is an interaction effect between energy and crude protein in the diet, where the highest response is with 19% PC for 2850 kcal ME/kg and 17.5% for 2950 kcal ME/kg.The extent to which energy and protein (CP) levels can be reduced without impacting productivity in slow-growing chickens remains undetermined. The treatments were conducted to evaluate the effect of dietary CP (17.5, 19, and 20.5%) and energy (2850-2950 kcal ME/kg) on slow-growing chickens using an ideal protein concept at a high altitude (3200 m). We used a total of 144 slow-growing chickens. The experiment lasted for eight weeks, a total of six treatments with three replicates each and eight chickens per replicate were used. Body Weight Gain (BWG) showed differences only in the growing chickens, for CP and the energy × CP interaction, the lowest BWG was at 17.5% CP (2850 kcal ME/kg) and 19.0% at 2950 kcal ME/kg (p<0.01) and higher for other interactions. BW and BWG maximized at 19% CP (2850 kcal ME/kg) and 17.5% CP (2950 kcal ME/kg). Feed intake was lower at 17.5 and 20.5% CP for respectively energy levels (p0.05). Abdominal fat increased with high energy (p<0.05). At both energies, maturity weight was highest at the lowest CP; growth rate (kg/d) was raised with higher dietary CP (2850 kcal ME/kg). The time to maximize growth rate decreased with higher CP at low energy but remained constant at high energy. There is an interaction effect between energy and crude protein in the diet, where the highest response is with 19% PC for 2850 kcal ME/kg and 17.5% for 2950 kcal ME/kg.