Biochemical and functional characterization of milk from alpina and tog-genburg goat breeds

Objective: This work aimed to evaluate the biochemical and functional properties of milk from two goat breeds (Alpina and Toggenburg) which could give goat's milk a higher added value and market, making it an attractive option for milk producers. Design/methodology/approach: Several biochemical analyses were performed to both breed milks: Total Fat (Gerber); Total Protein (Lowry); Lactose (reducing sugars); Fatty acid composition (Mass-mass coupled gas chromatography) and antihypertensive activity (angiotensin-converting enzyme inhibition). To determine possible applications, functional characteristics of yogurt and cheese were also evaluated. Statistical analyses were performed using NCSS software. Results: Fat content of Alpina breed was higher than Toggenburg’s (4.76% vs. 2.96%, α=0.00013), as was lactose (8.26% vs. 5.37%, α=0.003), while Toggenburg presented higher protein content (5.53% vs. 4.77%, α=0.00016). Potential biologically active fatty acids were found in both milks in similar concentrations. Toggenburg milk sowed higher antihypertensive activity than Alpina (100% vs 77.27%), which was maintained and in some cases increased, when fermented to obtain different derivatives such as cheese and yogurt. Limitations on study/implications: Further study is still needed to determine the entire biofunctionality of goat’s milk and provide milk producers with options to increase market and added value of their products. Findings/conclusions: Both, Alpina and Toggenburg goat’s milk showed a high Biofunctional potential due to their fat and protein fractions; The fact that biofunctionality can be transferred to derivatives such as yogurt or cheese may increase producers' interest in producing and commercializing it, since the products can be marketed as “functional foods”.Objective: This work aimed to evaluate the biochemical and functional properties of milk from two goat breeds (Alpina and Toggenburg) which could give goat's milk a higher added value and market, making it an attractive option for milk producers. Design/methodology/approach: Several biochemical analyses were performed to both breed milks: Total Fat (Gerber); Total Protein (Lowry); Lactose (reducing sugars); Fatty acid composition (Mass-mass coupled gas chromatography) and antihypertensive activity (angiotensin-converting enzyme inhibition). To determine possible applications, functional characteristics of yogurt and cheese were also evaluated. Statistical analyses were performed using NCSS software. Results: Fat content of Alpina breed was higher than Toggenburg’s (4.76% vs. 2.96%, α=0.00013), as was lactose (8.26% vs. 5.37%, α=0.003), while Toggenburg presented higher protein content (5.53% vs. 4.77%, α=0.00016). Potential biologically active fatty acids were found in both milks in similar concentrations. Toggenburg milk sowed higher antihypertensive activity than Alpina (100% vs 77.27%), which was maintained and, in some cases, increased, when fermented to obtain different derivatives such as cheese and yogurt. Limitations on study/implications: Further study is still needed to determine the entire biofunctionality of goat’s milk and provide milk producers with options to increase market and added value of their products. Findings/conclusions: Both, Alpina and Toggenburg goat’s milk showed a high Biofunctional potential due to their fat and protein fractions; The fact that biofunctionality can be transferred to derivatives such as yogurt or cheese may increase producers' interest in producing and commercializing it, since the products can be marketed as “functional foods”

Processes in meat oxidation and usage of rosemary (Salvia rosmarinus (L.) Schleid.,) as a natural antioxidant

Objective: Lipid oxidation of meat is one of the most important factors affecting shelf life and is one of the decisive factors in the consumer's purchase decision of the product. Therefore, information related to lipid oxidation using rosemary (Salvia rosmarinus (L.) Schleid.) as a natural antioxidant is described and analyzed. Design/methodology/approach: Mechanisms of oxidation were explored and described, as well as the alternatives to stop this process and different methodologies to measure antioxidant activity and innovative alternatives that are currently being investigated. Results: Appling antioxidants is one of the most widely used methods to counteract the oxidation process in meat. Currently, using herbs and spices has gained great acceptance, as in the case of rosemary. Its usage obtained satisfactory results for inhibiting and delaying lipid oxidation. Limitations of the study/implications: Using rosemary may have some drawbacks such as incorporating a strong flavor to the meat and the effects that its active compounds may have when exposed to oxygen, heat and humidity. Therefore, it is necessary to research for alternatives that will allow better preservation and availability of its compounds. Findings/conclusions: Nanoencapsulation of rosemary may be an alternative to the drawbacks of its use, working as a protective barrier for improved performance and improving food safety. However, this innovation is just being explored and is therefore not possible to have a certainty of success when using these new technological alternatives

Estudio de la actividad biológica de hidrolizados proteicos de Vicia faba L.

Objective: Evaluate the antioxidant and quelating activity of Vicia faba protein hydrolysates. Design/methodology/approach: Bean seeds of the San Pedro Tlaltizapan variety, purchased from the Institute of Agricultural, Aquaculture and Forestry Research of the State of Mexico (ICAMEX) were used. A protein substrate was prepared for enzymatic hydrolysis by alkaline extraction of the protein, followed by isoelectric precipitation from the defatted flour, the concentrate obtained was named CP. Subsequently, enzymatic hydrolysis of the PC was carried out with a sequential pepsin-pancreatin system and the degree of hydrolysis was determined. Finally, the antioxidant and chelating activity of protein hydrolysates was determined. Results: The defatted bean flour presented 18.6g of protein / 100g sample. While the concentrate obtained with this flour presented 62.7g of protein / 100g of sample. The protein increase in the concentrate was 3.4 times showing a significant difference (p?0.05) with the defatted bean flour. The total hydrolysis time was 90 min (45 min for each enzyme in the case of the sequential system). The highest GH obtained with the sequential system was 16% at 45 min. On the other hand, the chelation percentage of these hydrolysates was less than 25%. Limitations on study/implications: The protein concentrate of Vicia faba was not free of phenolic compounds, so this would be a limitation in the degree of hydrolysis and consequently in the chelating and antioxidant activity. Findings/conclusions: The protein hydrolysates of Vicia faba obtained through the sequential pepsin-pancreatin system present good antioxidant activity by the various methods studied, showing that when pancreatin is added to the system, these activities improve, since hydrolysates are active, they could be used as functional ingredients in food products.Objetivo: Evaluar la actividad antioxidante y quelante de los hidrolizados proteicos de Vicia faba. Diseño/metodología/aproximación: Se utilizaron semillas de haba de la variedad San Pedro Tlaltizapan, adquiridas en el Instituto de Investigación Agropecuaria, Acuícola y Forestal del Estado de México (ICAMEX). Se preparó un sustrato proteínico para la hidrólisis enzimática por extracción alcalina de la proteína, seguida de precipitación isoeléctrica a partir de la harina desengrasada, el concentrado obtenido se denominó CP. Posteriormente se llevó a cabo la hidrólisis enzimática del CP con un sistema secuencial pepsina-pancreatina y se determinó el grado de hidrólisis. Finalmente se determinó la actividad antioxidante y quelante de los hidrolizados proteicos. Resultados: La harina de haba desengrasada presentó 18.6g de proteína/100g muestra. Mientras que el concentrado obtenido con esta harina presentó 62.7g de proteína/100g de muestra. El aumento de proteína en el concentrado fue 3.4 veces mostrando diferencia significativa (p?0.05) con la harina de haba desengrasada. El tiempo total de hidrólisis fue de 90 min (45 min para cada enzima en el caso del sistema secuencial). El mayor GH que se obtuvo con el sistema secuencial fue de 16% a los 45 min. Por otra parte, el porcentaje de quelación de estos hidrolizados fue menor al 25%. Limitaciones del estudio/implicaciones: El concentrado proteico de Vicia faba, no estaba libre de compuestos fenólicos, por lo que esto sería una limitante en el grado de hidrólisis y consecuentemente en la actividad quelante y antioxidante. Hallazgos/conclusiones: Los hidrolizados proteicos de Vicia faba obtenidos a través del sistema secuencial pepsina-pancreatina presentaron actividad antioxidante por los diversos métodos estudiados, mostrando que, al adicionar pancreatina al sistema, estas actividades mejoran, por lo tanto, los hidrolizados podrían ser utilizados como ingredientes funcionales en productos alimenticios

Caracterización físico-química de maíz (Zea mays L.) criollo (azul y rojo) del Estado de México

Objective: To evaluate the physical and chemical characteristics of the creole corn (blue and red) from the Estado de México. Design / methodology / approach: Size (mm), hectoliter weight (kg/Hl-1), color and aw were evaluated on blue and red creole corn. Besides, moisture, ash, ethereal extract, and protein content were evaluated. Statistical analysis was performed to assess possible significant differences using the Tukey test (p <0.05). Results: Red creole corn had lower moisture and higher protein and ethereal extract contents also it was larger and had higher hectoliter weight therefore the flour yield of red corn could be higher than in blue corn. Study limitations / implications: Biological activity of the evaluated creole corn kernels is necessary for it use as a functional food. Findings / Conclusions: Red corn had better physicochemical characteristics than blue cornObjetivo: Evaluar las caracterísicas físicas y químicas de maíz criollo azul y rojo del Estado de México. Diseño/metodología/aproximación: Para la caracterización físicoquímica del maíz criollo azul y rojo, las variables que se evaluaron fueron tamaño (mm), peso hectolítrico (kg/Hl-1), color (escala LAB) así como la  actividad de agua (aw). Además se realizó un análisis químico proximal determinando humedad, cenizas, extracto etéreo y proteína. Se realizó un análisis estadístico para evaluar las posibles diferencias significativas utilizando la prueba de Tukey (p<0.05). Resultados: El maíz rojo tuvo menor valor de humedad, mayor contenido de extracto etéreo y proteína que el maíz azul, además tiene mayor tamaño y peso hectolítrico lo que lo hace buen candidato para la obtención de harina. Limitaciones del estudio/implicaciones: La determinación de la actividad biológica es necesaria para poder recomendar el uso de estos maíces criollos como alimentos funcionales. Hallazgos/conclusiones: El maíz rojo tiene mejores características físicoquímicas que el maíz azul

How is the perception of the certified organic food benefits in a population from Estado de México region

Objective: To study and understand the population's perception in a region of the Estado de Mexico about the role of certified organic food in health and the environment, as well as the economic impact generated by its consumption. Desing/methodology/approach: A survey was conducted among a population sample of 10 municipalities in the Estado de Mexico, which consisted of seven questions related to certified organic food. Results: The population has an idea about what certified organic food is, although they confuse it with other types of food.  Study limitations/ implications: Results were obtained from an e-mail survey because this study was conducted during the current 2020-2021 pandemic. Findings/conclusion: The information obtained suggests that the population has a great perception about the intake of certified organic food, but there is confusion about other types of food. However, the population is willing to consume them because of their potential health and environment benefits

Actividad antihipertensiva de péptidos de zeína extraídos de maíz (Zea mays L.) criollo (azul y rojo) del Estado de México

Objective: To evaluate the antihypertensive activity of peptides extracted from nixtamalized and non-nixtamalized creole corn (blue and red) zein from the Estado de México. Design / methodology / approach: Bioinformatic tools, such as the NCBI database, were used to search for primary sequences of the maize zein protein. The methodology included a prediction of peptides with antihypertensive activity through various bioinformatic servers. Inhibitory activity was determined by percentage regression. Statistical analysis was performed to assess possible significant differences using the Tukey test (p <0.05). Results: The following peptides were found by in silico hydrolysis: IFSILMLLA, LSACVLDATI, TASVCENPTL, LPLSPLLFQQ, SPALSLVQSL, LSPYSQQQQF, PFSQLATAY, LPFYQQFSAN and PAAFYQQHII that showed inhibition activity. The results showed that the GH (grade of hydrolysis) was higher in blue corn (13.96 ± 0.02) than in red corn (10.38 ± 0.79) without nixtamalization, while, with the nixtamalization process, this parameter was also higher in blue corn (10.52 ± 0.57) than in red corn (8.96 ± 0.01). Study limitations / implications: The enzyme used for hydrolysis generates oligopeptides that may not be as closely related to the angiotensin-converting enzyme. Findings / Conclusions: In vitro antihypertensive activity of unhydrolyzed blue corn zein showed a lower percentage of ACE inhibition compared to unhydrolyzed red corn. Trypsin hydrolysis only increases ACE inhibitory activity in blue corn at a concentration of 0.3 mg / mL without nixtamalizing.Objetivo: Evaluar la actividad antihipertensiva de péptidos extraídos de zeína de maíz criollo azul y rojo nixtamalizado y sin nixtamalizar del Estado de México. Diseño/metodología/aproximación: Se emplearon herramientas bioinformáticas, tales como la base de datos NCBI para la búsqueda de secuencias primarias de la proteína zeína del maíz. La metodología incluyó una predicción de los péptidos con actividad antihipertensiva a través de diversos servidores bioinformáticos. La actividad inhibitoria se determinó mediante la regresión del porcentaje. Se realizó un análisis estadístico para evaluar las posibles diferencias significativas utilizando la prueba de Tukey (p<0.05). Resultados: Por medio de la hidrólisis in sílico se encontraron los siguientes péptidos: IFSILMLLA, LSACVLDATI, TASVCENPTL, LPLSPLLFQQ, SPALSLVQSL, LSPYSQQQQF, PFSQLATAY,            LPFYQQFSAN y PAAFYQQHII que mostraron actividad de inhibición de la ECA. Los resultados mostraron que el GH de la zeína fue mayor en maíz azul (13.96±0.02) que en maíz rojo (10.38±0.79) sin nixtamalizar, mientras que, con el proceso de nixtamalización, este parámetro también fue mayor en el maíz azul (10.52±0.57) que en el maíz rojo (8.96±0.01). Limitaciones del estudio/implicaciones: La enzima utilizada para la hidrólisis enzimática genera oligopéptidos que tal vez no puedan ser tan afines a la enzima convertidora de angiotensina. Hallazgos/conclusiones: La actividad antihipertensiva in vitro del maíz azul sin hidrolizar mostraron un menor porcentaje de inhibición de la ECA con respecto al maíz rojo sin hidrolizar. La hidrólisis con tripsina solo incrementa la actividad inhibitoria de la ECA en maíz azul a concentración de 0.3 mg/mL sin nixtamalizar

Funcíon fisiológica del selenio suplementado como selenito de sodio y selenometionina en corderos

El Objetivo de este trabajo fue evaluar el efecto del suplemento de selenio (Se) sobre la función digestiva de corderos. Veinte corderos fueron utilizados en este experimento, y todos ellos fueron incluidos en el tratamiento uno: 1) Sin suplemento de Se 0.1 ppmSe, Después de finalizar este, todos los corderos fueron divididos en los siguientes 2 tratamientos T2) Con suplementación de Na2SO3,: dieta con 0.3ppmSe y 3) Con suplementación de selenometionina, dieta con 0.3 ppmSe. Antes de iniciar el experimento, los 20 corderos con un peso de 30 kg y una edad de 6 meses fueron canulados en el rumen y duodeno. Los animales fueron mantenidos en jaulas metabólicas; el consume del alimento fue realizado por dos veces al día, ajustando este para que no existieran rechazos. Los tratamientos fueron distribuidos en 3 grupos con una adaptación de 10 días y 5 días de muestreo por periodo, las comparaciones entre los promedios fue realizado con la prueba de diferencia mínima significativa. Las muestras de liquido ruminal fueron usadas para determinar el pH, Se en bacteria, población de bacterias y protozoarios, concentración de AGV y concentración de Se. Las muestras de liquido duodenal y fecal fueron usadas para determinar la digestibilidad pre-gástrica, post-gástrica y total, con la inclusión de 0.4% de óxido crómico como marcador de la digesta. Los resultados de las pruebas demostraron el efecto de Se de la dieta sobre la tasa de pasaje en el intestino delgado. El suplemento de Se en la dieta con selenito de sodio y selenometionina mejoró la tasa de pasaje del selenio al intestino delgado. La eficiencia microbiana ruminal (g NM/kg MO verdadera fermentada) tendió a incrementar con la suplementación de Se. No hubo diferencias en la solubilidad de Se, proporción molar de acético, propionico y butírico. La concentración de bacterias en el liquido ruminal incrementó con ambas fuentes de suplementos de Se. En conclusión, no hubo diferencias en la absorción y digestibilidad con selenito de sodio o selenometionina incluida en la dieta de corderos.______The objective of this work was to evaluate the effect of selenium (Se) supplement on the digestive function of lambs. Twenty lambs were used in this experiment and all they were included in treatment one: 1) Without supplement of Se :0.1 ppmSe, After finished this one, all lambs were divided in following 2 treatments: T2) With suplementation of Na2SO3: diet with 0.3ppm and 3) With suplementation of selenometionin, diet with 0.3 ppm. Before to beginning this experiment, twenty lambs with to weight of 30 kg and an age of 6 months were cannulated in rumen and duodenum. The animals were housed in metabolic cages; the consumption of the food was carried out twice a day, adjusting it so that there were not rejections. The treatments were distributed in 3 groups with an adaptation of 10 days and 5 days of sampling per period; the comparisons among the averages of the effects were carried out with SMD. The samples of the ruminal liquid were used to determine the pH, Se bacteria, bacteria and protozoa population, the concentration of VFA and the concentration of Se. The samplings of duodenal and fecal liquid were used to determine the digestibility pre-gastric, post-gastric and total, with the inclusion of 0.4 % chromic oxide as a digesta marker. The results of the tests showed Se effect of the diet on the passage rate in the small intestine. The Se supplement in the diet with sodium selenite and selenometionin improved the passage of Se to the small intestine. The efficiency microbial ruminal (g NM/kg MO truly fermented) tend to increase with the suplementation of Se. There were not differences on the solubility of the Se, proportion molar of acetic, propionic and butyric acid. Bacteria concentration in ruminal fluid increased with both sources of Se supplement. In conclusion, there were not differences in absorption and digestibility with sodium selenite or selenometionin including in the diet of lambs.Tesis (Maestría en Ciencias, especialista en Ganadería).- Colegio de Postgraduados, 2008

“EFECTO DE PIGMENTOS CAROTENOIDES Y PECTINA EN LA CALIDAD DE LA GRASA DE BOVINOS”

The aim of this thesis was to study the physiological processes in bovines involved in the disapparence and digestibility of carotenoides found in feeds, and the interaction of these pigments with pectin to reduce β-carotene absorption leading to “yellow fat” incidence. The experimental work was divided in two parts. The first one involved the analysis of the most common forages used in tropical areas of Mexico. Based on their characteristics, Star grass (Cynodon plectostachium) was selected for experiments in situ on carotenoid absorption. The second part was focused on metabolic studies of pectin infused to the duodenum as an antagonist to carotenoids for reducing pigment intestinal absorption. First Part. Tropical forage analysis and in situ degradability of Star grass Samples of fifteen forage species were colected from seven regions of Veracruz State; the samples were at 21 to 25 days preflowering regrowth. Based on forage growth and bromatological characteristics, Star grass was selected as study material. Four Holstein steers (384±60 kg), cannulated at the rumen and duodenum, were studied. Nutrient decrease through the intestine was study by the mobile nylon bag technique. Nylon bags, containing a known amount of forage, were introduced by the cannula into the rumen. After a given time of incubation, the bags were removed and placed into a solution simulating abomasal digestion. A total of 20 bags divided into 5 batches were placed through the duodenum cannula towards the small intestine; the batches were introduced into the duodenum every 15 min. The bags were then collected from feces, washed, and total carotenoid and dry matter (DM) analyzed. Carotenoid concentration significantly decrease (P˂ 0.001) in the rumen during the first 12 h; further decrease between 24 and 72 h was not significant (P=0.71). Correlation index for DM and total carotenoides in the rumen was r=0.997 (P˂ 0.001). Approximately 53% carotenoids in Cynodon spp. contained in duodenum bags (bags not previously incubated in the rumen) dissapeared when introduced in the small intestine. As expected, bags incubated for longer periods of time contained less carotenoid concentration and, therefore, the total pigment amount disapperance in the small intestine was significantly reduced (P˂ 0.001). The results of this study showed that considerably high carotenoid xi proportions were not degraded through microbial metabolic pathways in the rumen. It was concluded that the incubation time was a factor affecting bioavailability of carotenoids. Second Part. In vitro digestability and digestive metabolism studies on duodenum β-carotene dosification and pectine infusion Four Holstein steers (average weight 462.5 kg) with duodenal and ruminal cannulas were studied. Feed was supplied twice a day (7:00 and 19:00), 9.603 kg (DM) approximate total daily intake. Low (0.004%), medium (0.01%) and high (0.02) pectin levels were infused through the duodenum. No pectin or β-carotene were included in the control; 0.4% chromium oxide was used as a digesta marker, infused through the ruminal cannula together with 3 g βcarotene. The animals were subjected to 10 days adaptation and 5 days sampling allocated to a 4x4 Latin Square experimental design. The response variables were: dry matter, organic matter, protein, neutral detergent fiber, β-carotene, chlophyll a and chlorophyll b, analyzed in the ruminal liquid, duodenal liquid and feces. In addition, cholesterol concentration was analyzed in blood and feces. Not significant differences were observed for the four treatments in dry matter, organic matter, protein and fiber in post-ruminal flow (P=0.202). Conversely, significant differences were observed with respect to β-carotene and chlorophylls a and b in the post-ruminal flow (P=0.0002). β-carotene excretion increased twice with 0.004 and 0.01% pectin infusion. Moreover, four-fold β-carotene excretion was observed with 0.02% pectin infusion. Correlation index for pectine dose and β-caroteno excretion was r=0.912 (P=0.02). β-carotene post-ruminal digestibility decreased with pectine supply, whereas absorption or digestibility was proportional to the pectine dose (P=0.05); 44.5 to 55.5% decrease in digestibility was observed. No significant differences were observed among treatments for chlorophyll a and b concentration (P=0.77). Digestibility of chlorophyll a pigment had not significant differences among treatments (P=0.43) (Xdigestibility = 99.8%) Absorption of chlorophyll b increased threefold when pectine was infused as compared to the control (P=0.004) although not significant differences were observed among pectin-containing treatments. Blood cholesterol decreased 15.6, 18 and 27% when pectin was infused. It was concluded that pectin supply decreased βcarotene, chloropyll b and blood cholesterol, but not chlorophyll a absorption.El objetivo de la presente tesis fue estudiar los procesos fisiológicos involucrados en la disminución de la concentración y digestibilidad de carotenoides en las dietas de bovinos y su interacción con pectina, con el fin de disminuir la absorción de estos pigmentos y con esto, reducir el color amarillo que dicha absorción ocasiona en la grasa. El trabajo experimental se dividió en dos partes. La primera consistió en la caracterización de los forrajes tropicales más comunes en zonas tropicales de México. Posteriormente, y con base en esta caracterización, se seleccionó pasto Estrella (Cynodon plectostachium) como material de prueba en estudios in situ de la disminución en la concentración de carotenoides. La segunda parte consistió en el estudio metabólico digestivo de la pectina infusionada en el duodeno, como antagonista de pigmentos carotenoides con el fin de disminuir su absorción intestinal. Primera Parte. Análisis de forrajes tropicales y degradabilidad in situ del pasto Estrella Se recolectaron en el Estado de Veracruz y Tabasco 5 especies de forrajes, 15 muestras de forraje por cada especie con 21 a 25 días de rebrote prefloración. Con base en sus características de crecimiento y bromatológicas, se seleccionó pasto Estrella como material de estudio para ser evaluada en 4 novillos Holstein (384±60 kg) canulados en el rumen y en el duodeno. La disminución de los nutrientes durante el paso por el intestino se determinó mediante la técnica de bolsas móviles, la cual consistió en colocar en bolsas de nylon una cantidad conocida del forraje a estudiar; estas bolsas se introdujeron a través de la cánula del rumen e incubaron por un tiempo determinado. Posteriormente las bolsas se retiraron, se sumergieron en una solución que simulaba la digestión abomasal, y se introdujo un total de 20 bolsas en lotes de 5 a través de la cánula del duodeno hacia el intestino delgado, con tiempos de 15 minutos de separación en la introducción de cada lote. Las bolsas se recolectaron de las heces; una vez lavadas, se analizó el contenido de carotenoides totales y de materia seca (MS). Se observó una disminución significativa de carotenoides (P˂0.0001) en el rumen durante las primeras 12 h; posteriormente, entre 24 y 72 h, esta disminución no fue significativa (P=0.71). El índice de correlación entre la disminución de MS y los carotenoides totales en el rumen fue r=0.997 (P˂0.001). Alrededor de 53% de la concentración de carotenoides contenidos en Cynodon spp. en las bolsas duodenales (no incubadas previamente en rumen) disminuyó cuando se introdujeron en el intestino delgado. Como se esperaba, las bolsas con más tiempo de incubación en el rumen contenían menor concentración de carotenoides y, por lo tanto, la cantidad total degradada en el intestino delgado se redujo significativamente (P˂0.001). Los resultados de este estudio mostraron que una proporción alta de carotenoides no fueron degradados a través de rutas metabólicas microbianas en el rumen. Se concluyó que el tiempo de incubación es un factor que contribuye a la variación en la biodisponibilidad de los carotenoides. Segunda Parte. Digestibilidad in vitro y estudio del metabolismo digestivo con dosificación de -caroteno e infusión de pectina vía duodenal Se utilizaron 4 becerros Holstein con un peso promedio de 462.5 kg con cánulas ruminal y duodenal. El alimento se suministró dos veces al día (7:00 y 19:00 horas), con un consumo total aproximado por día de 9.603 kg (MS). Se incluyeron en las dietas dosis de pectina baja (0.004%); media (0.02%) y alta (0.01%), y 3 g de -caroteno. El control consistió en la dieta sin pectina ni -caroteno. Se empleó una dosis de 0.4% de óxido de cromo como marcador de la digesta. Las dosis de pectina se suplementaron por infusión por vía de la cánula duodenal; el cromo y β-caroteno fueron administradas directamente en la cánula de rumen. Se emplearon 10 días de adaptación y 5 días de muestreo en un diseño en Cuadro Latino. Las variables de respuesta fueron: materia seca, materia orgánica, proteína y fibra detergente neutra, -caroteno, clorofila a y clorofila b en liquido ruminal, liquido duodenal y heces. Adicionalmente, se analizó colesterol en sangre y grasa en heces. No se observaron diferencias significativas (P=0.202) entre los cuatro tratamientos en el flujo postruminal de materia seca, materia orgánica, proteína y fibra detergente neutra; de forma opuesta, se observaron diferencias significativas (P=0.0002) entre los tratamientos con respecto al flujo de β-caroteno y clorofilas b (P˂0.001). Al suministrar 0.004 y 0.01% de pectina se duplicó la excreción de β-caroteno en comparación con el testigo. Sin embargo, al suministrar 0.02% de pectina se incrementó por un factor de 4 la excreción de β-caroteno. La correlación entre la dosis de pectina y la excreción de β-caroteno en el tracto total fue r=0.912 (P=0.02). La digestibilidad postruminal de β-caroteno disminuyó con la administración de la pectina, mientras que el efecto en la disminución de absorción o digestibilidad fue proporcional a la dosis de pectina administrada (P˂0.05). Las dosis baja (0.004%) e intermedia (0.01%) de ix pectina no afectaron significativamente (P=0.72) a la digestibilidad total de β-caroteno, aunque se observó una disminución de la digestibilidad entre 44.5 y 55.5%. La concentración de clorofila a y b no presentaron diferencia significativa entre los tratamientos (P=0.77). La digestibilidad de la clorofila a no presentó diferencias significativas (P=0.43) entre los tratamientos (X digestión = 99.8%). La absorción de la clorofila b aumento tres veces en comparación con el tratamiento testigo (P=0.004), aunque no hubo diferencias significativas entre los tratamientos que incluían pectina. La concentración de colesterol sanguíneo decreció 15.6, 18 y 27% cuando se suministró pectina. En conclusión, la administración de pectina disminuyó la absorción de β-caroteno, clorofila b y colesterol hemático