Claudio Aguilar

Nutritional evaluation of diets. Simulation model of digestion and passage of nutrients through the rumen-reticulum

Abstract To evaluate the nutritional behaviour of simple and complex diets provided under different feeding regimes, a stochastic, dynamic and predictive simulation model was developed. Feed fractions, considered in the model were soluble non-structural carbohydrates (SNSC), insoluble non-structural carbohydrates (INSC), INSC degradation rate ( kd INSC ), fractional passage rate ( kp ), neutral detergent fibre (NDF), NDF potentially digestible (PNDF), PNDF degradation rate ( kd PNDF ), soluble crude protein (SCP), insoluble crude protein (ICP), ICP potentially degradable (PICP), and PICP degradation rate ( kd PICP ). Animal characteristics considered in the model, were live weight and physiological status (lactation and/or pregnancy). Variables inherent to management practices were amounts and schedule of DM offered to the animals. The model was subjected to validation for a wide range of experimental conditions. Predictions of total DM and forage DM intakes (and therefore the estimate of the substitution of forage for concentrate) had an R 2 = 0.95 and 0.92, respectively. Prediction of NDF digestibility had an R 2 = 0.61 in a smaller range of experimental conditions.

FEEDING DRY OLIVE CAKE MODIFIES SUBCUTANEOUS FAT COMPOSITION IN LAMBS, NOTING CAKE RESISTANCE TO DEGRADATION AND PEROXIDATION

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized experiment using 36 single male Suffolk Down lambs with an initial age and live weight of 80 d and 25 kg, respectively. The three treatments were: (a) suckling lambs kept with their mothers on annual Mediterranean grassland (GRAZE); (b) weaned stall-fed lambs on a control ration (CONC); and (c) weaned stall-fed lambs on an olive cake-based ration (CAKE). At the end of the 28-d experimental period, lambs were slaughtered, carcass quality evaluated, and samples of subcutaneous fat analyzed for fatty acids. Treatments did not differ in weight gain or carcass weight and quality, but highly significant differences were found in several fatty acid contents. CAKE animals had reduced palmitic acid as well as increased oleic and stearic acid contents. Atherogenic and thrombogenic indices improved with cake feeding. Principal component and discriminant analyses clearly differentiated treatments suggesting they could be applicable for traceability purposes. A laboratory experiment demonstrated that with or without added vitamin E, the dry olive cake did not alter its lipid properties with increased storage time.

Differentiation of sheep milk and cheese based on quality and composition

Traditional sheep production for meat and wool for meat and wool among small and medium-sized Chilean farmers has low profi tability. Therefore, there is interest in producing value-added, differentiated products. One alternative is the production of sheep milk and cheese. This article analyzes and discusses existing alternatives for modifying milk and cheese compositions with the aim of differentiating these products. Also, analytical techniques that allow the chemical characterization of milk and cheese are briefl y mentioned. The main international thrusts are focused on the modifi cation of the content and composition of milk fatty acids and on the identifi cation of volatile compounds, terpenes, polyphenols and other analytes that allow differentiation of cheese types on the basis of aroma, taste and fl avor and that would help in ensuring traceability. La rentabilidad de la produccion ovina tradicional entre productores pequenos y medianos es muy baja, razon por la cual es deseable buscar alternativas con mayor valor agregado y diferenciacion. Una alternativa de interes es la produccion de leche ovina para la elaboracion de quesos. El articulo analiza y discute las alternativas para modifi car la composicion de la leche y quesos de forma de diferenciarlos. Se discute como es posible cuantifi car objetivamente dichos cambios y se mencionan brevemente algunas de las tecnicas analiticas disponibles con ese fi n. En general, los esfuerzos que se estan realizando a nivel mundial se focalizan en la modifi cacion del contenido y perfi l de los acidos grasos, asi como la identifi cacion y cuantifi cacion de compuestos volatiles, terpenos, polifenoles y otros que permitirian diferenciar quesos y leche por sabor y olor, y que permiten asegurar la trazabilidad.

Performance of lambs grazing an annual Mediterranean pasture or fed supplements based on olive oil cake or maize and its influence on system outputs

Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual Mediterranean pasture (GRAZE), weaned followed by a concentrate plus hay diet (CONC), or weaned and fed a concentrate with 33% dry olive oil cake plus hay (CAKE). Grazing lambs averaged a liveweight gain of 334 g/day during the 28-day experimental period, which was higher (P < 0.05) than that of CONC and CAKE (283 and 276 g/day, respectively); however, there were no differences in empty body or dressed carcasses weights due to dietary treatment. The feed conversion of the olive seed cake supplement (kg supplement/kg gain) was lower (P < 0.01) than that of the maize-based supplement. Despite some significant differences between carcasses traits, all were small and of little commercial consequence. Simulation modelling of whole-system performance suggested that early weaning of lambs followed by concentrate feeding would reduce the finishing period, marginally increase the liveweight of ewes and would have little effect on pasture availability. It was further concluded that olive oil cake can be a large proportion of concentrate diets without negatively affecting carcass quality.

A simulation model of an alpaca system in the dry puna of the Andes

Abstract A stochastic model was developed to study the alpaca production system in the high Andes. The model was based on actual knowledge of the biology of the alpaca, especially energy metabolism. It is composed of six subroutines: voluntary intake, energy partitioning, reproduction, fiber production, offspring development and forage utilization. Outputs of the model were validated against data from research and from a dynamic survey of a peasant community (Apopata). Model predictions did not differ ( p >0·05) from actual data on voluntary intake, body weight and fiber production for different animal categories. Simulation experiments showed that the management given by the farmers allows the system to recuperate during years of good rainfall, assuring its sustainability.

Economic Sustainability of Organic Dairy Sheep Systems in Central Spain

Sheep production systems in regions with a Mediterranean climate are important in social, economic and environmental terms. Modeling these systems allows, among others, evaluation of the costs efficiencies which in turn permits assessing the expected effects of changes in production variables. This paper presents a prototype analysis of the economic sustainability of ecological dairy sheep systems of Castilla-La Mancha, Central Spain evaluated through the estimation of costs efficiencies. Costs functions were developed using data from 31 farms. Rate of supplementary feeding, labour use, and flock size were used to measure the cost efficiency. On average, cost efficiency was 61.7±15.5%, with significant differences among typological groups. High efficiency was found in only 29% of the farms. The economic analyses performed suggest that the continued existence of economically unsustainably farms is explained by the available subsidies, lack of amortization of fixed assets leading to progressive decapitalization, and subsistence incomes by family groups (gross family income).

Feeding extruded linseed to dairy ewes under extensive grazing conditions

The aim of this trial was to evaluate the effect of dietary supplementation of extruded linseed on the milk and cheese fatty acid (FA) profiles of ewes under extensive grazing conditions. Over 26 days, a group of nine lactating ewes (Latxa × Milchaf × Corriedale) in mid-lactation were managed under grazing conditions and given supplements during each manual milking (0830 and 1800 h) of 50% corn and 50% oats (500 g ewe -1 milking -1 ; control, TC) for the first 6 days. From day 7 to 20, the supplement was 25% corn, 25% oats and 50% extruded linseed (500 g ewe -1 milking -1 ) (extruded linseed; TEL). From day 21 to 26, the ewes were fed TC. The saturated FA content in milk was reduced (3.6%), and the monounsaturated, polyunsaturated and n-3 FA (7, 10 and 25%, respectively) were increased when the ewes were supplemented with extruded linseed. A correlation between rumenic acid with vaccenic acid (R 2 =0.68) was found in the milk fat from ewes fed TEL. In cheese obtained from TEL, the contents of n-3 and polyunsaturated FA were increased (21 and 7%, respectively). In conclusion, a supplement of extruded linseed in ewes under grazing conditions could be an alternative lipid source to produce cheese with additional nutritional value. However, the effect of extruded linseed supplementation in ewes under the same conditions with longer experimental periods and a more suitable statistical design must be investigated. El objetivo de este ensayo fue evaluar el efecto de suplementar extruido de linaza en el perfil de acidos grasos de leche y queso de ovejas en pastoreo extensivo. Durante 26 dias, un grupo de nueve ovejas lactantes (Latxa × Milchaf × Corriedale) fueron manejadas en pastoreo extensivo y suplementadas durante cada ordeno manual (830 y 1800 h) con 50% maiz + 50% avena (500 g oveja -1 ordeno -1 ) durante los primeros 6 dias (control; TC), de los dias 7 al 20 se suplementaron con 25% maiz + 25% avena + 50% extruido de linaza (500 g/oveja/ordeno) (extruido de linaza; TEL), y finalmente, del dia 21 al 26 las ovejas fueron alimentadas con TC. El contenido de acidos grasos saturados en leche fue reducido (3,6%) mientras que los acido grasos monoinsaturados, polinsaturados y n-3 fueron incrementados (7, 10 y 25%) en aquellas ovejas alimentadas con TEL. Se observo una correlacion de acido rumenico con acido vaccenico (R 2 =0,68) en leche de ovejas alimentadas con TEL. Los quesos elaborados de ovejas alimentadas con TEL, aumentaron su contenido de n-3 y acidos grasos poliinsaturados (21 y 7%). En conclusion, el suplementar ovejas en pastoreo extensivo con extruido de linaza puede ser una alternativa que puede resultar en la elaboracion de quesos con un valor nutricional mas saludable desde el punto de vista humano. Ademas resulta necesario investigar mas sobre el uso del extruido de linaza bajo las mismas condiciones con periodos mas largos de experimentacion usando un diseno estadistico mas apropiado.

Characterization of cheese consumers in Santiago Province, Chile

A high demand for Chilean cheese has resulted in increased cheese production. This increase represents an opportunity to promote the development of new markets, such as for small ruminant cheeses. However, little has been discussed regarding the extent to which cheese consumers consider small ruminant cheeses. We hypothesized that price is the main determining factor for purchasing cheese. The present study examined this previously unexplored aspect. The objective of this study was to identify the factors that contribute to the purchaser’s response behavior, including purchase, usage and product possession. This study also aimed to provide preliminary information on cheese consumption in the Province of Santiago, Chile. A personal interview was conducted in a sample of 323 individuals in major supermarkets from five municipalities (Santiago, La Florida, Las Condes, Pudahuel, and Recoleta) of Santiago city between March and May 2012. The largest proportion of surveyed individuals were female (62%) who were between 20 to 25 years (34%). The main cheese purchaser of the household was more often the woman (52%; P<0.01). The brand and origin (70%; P≤0.01) and price (30%; P≤0.01) of the cheese were the main aspects considered before making a purchase. Cow’s milk cheese was the predominant cheese type consumed (77%), followed by goat’s milk cheese (6%), cow’s and goat’s milk cheese (15%) and cow’s, goat’s and sheep’s milk cheese (2%). Of the individuals surveyed, 35% consumed cheese three times per week as a sandwich ingredient. We conclude that consumer fidelity is driven by brand and origin and a preference to use the cheese in sandwiches (81%). Data from this study may be used to determine the most adequate strategy for promoting the sales of small ruminant cheeses. La produccion de queso en Chile esta creciendo debido a un alza en su demanda; este fenomeno podria representar una oportunidad para promover el desarrollo de nuevos mercados (quesos de rumiantes menores), sin embargo, poco se ha investigado sobre el consumo de quesos. La hipotesis que se contrasta es que los sujetos que compran queso en el mercado lo hacen con un grado debil de implicacion, donde el precio del producto es la variable mas importante en el comportamiento de compra. Este estudio tiene por objetivo identificar funciones de respuesta comportamental, para analizar los procesos de adquisicion, utilizacion, y posesion del producto en la Provincia de Santiago en Chile. Un cuestionario personal fue realizado a una muestra de 323 personas en supermercados de cinco comunas (Santiago, La Florida, Las Condes, Pudahuel y Recoleta) de la ciudad de Santiago entre marzo y mayo del 2012. La mayor proporcion de personas encuestadas resulto ser mujeres (62%) entre 20 y 25 anos de edad (34%). Las mujeres (52%; P≤0.01) resultaron ser las personas que se encargan de comprar el queso mientras que marca y origen (70%; P≤0.01) y precio (30%; P≤0.01) fueron los aspectos mas importantes que el consumidor considera antes de realizar la compra de queso. El queso de origen vacuno fue el queso que mas se consume (77%), la diferencia se distribuye en queso de cabra (6%), queso de vaca y queso de cabra (15%) y quienes consumieron queso de vaca, cabra y oveja (2%). Del total de encuestados, el 35% consume queso tres veces a la semana como un ingrediente en sandwiches. Se puede concluir que la accion de compra de queso tiene una debil implicacion, como generalmente se asume, con una aprehension complementaria entre racional y emocional. Ello se explica por una presumible alta tasa de fidelidad a marca/origen en quesos cuya principal caracteristica es ser suave, caracteristica que lo hace apropiado para el fin que se utiliza (81%): sandwich. Los resultados de este estudio podrian ser utilizados para encontrar la forma mas apropiada de ingresar al mercado de quesos de pequenos rumiantes: un uso practico y habitual.

Predicción del consumo de materia seca en bovinos a partir del comportamiento ruminal y contenido de fibra detergente neutro (FDN) de los alimentos

Prediccion del consumo de materia seca en bovinos a partir del comportamiento ruminal y contenido de fibra detergente neutro (FDN) de los alimentos