Mathematical models of food intake and metabolism in ruminants.

Illius, A.W.; Gill, Mikhail; Cronj, P. B.

doi:10.1079/9780851994635.0021

Cited by 11 publications

(9 citation statements)

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“…The outflow rate for each rumen pool is different, but both the fluid and particulate phases will wash out microbial protein (Illius et al, 2000). It is generally accepted that a faster passage rate and an increased turnover time would improve microbial efficiency due to a faster change of rumen population and better supply of microbial protein to the lower tract.…”

Section: Ruminal Fluid Kinetics and Degradation Of Dietary Componentsmentioning

confidence: 99%

Effects of dietary addition of zinc and(or) monensin on performance, rumen fermentation and digesta kinetics in beef cattle

Arelovich

Laborde

Amela

et al. 2008

Span. j. agric. res.

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Two experiments (Exp1 and Exp2) were conducted to investigate the effect of dietary inclusion of Zn and(or) monensin on performance and rumen fermentation in beef cattle fed a barley grain, alfalfa hay and sunflower meal. In Exp1, 20 calves were assigned to one of the following treatments: CON = control; Z = 430 mg Zn kg -1 of DM; M = 35 mg monensin kg -1 of DM; and ZM = both Zn and monensin. Dry matter intake (DMI), DM digestibility (DMD), average daily gain (ADG), and feed to gain (F/G) ratio were determined. Blood analyses included hematocrit, glucose, urea, total protein, alkaline phosphatase and creatinine. In Exp2, the rumen fluid of four cannulated steers, in identical treatments, was studied for Zn concentration, pH, NH 3 -N, VFA. Rumen dilution rate, turnover time, and volume; in situ DM disappearance of barley and alfalfa were also determined. In Exp1, no treatment response was observed for DMI, ADG or DMD (P > 0.10). Differences in F/G were not significant, despite a numeric F/G decrease in M (6.6 kg kg -1 ). No differences were detected in blood variables. In Exp2, an interaction of treatment × time (P = 0.0174) for Zn concentration was detected, where ZM, followed by Z, had highest mean values at all time intervals. Ruminal parameters, kinetics or DM degradability were not modified by treatments; pH reached the lowest value (6.1; P < 0.05) 12 h after supplement feeding. Overall, supplying more than 20 times the Zn requirement has not substantially affected performance or digestion.Additional key words: additives, blood parameters, intake, rumen kinetics, ruminants, weight gain. ResumenEfecto de la adición a la dieta de Zn y/o monensina sobre la respuesta productiva, fermentación ruminal y cinética digestiva en bovinos de carne En dos experimentos (Exp1 y Exp2) se investigó el efecto de la inclusión en la dieta de Zn y/o monensina sobre la productividad y fermentación ruminal de bovinos alimentados con grano de cebada, alfalfa y harina de girasol. En Exp1, 20 terneros fueron asignados a tratamientos: CON = control; Z = 430 mg Zn kg -1 de MS; M = 35 mg monensina kg -1 de MS y ZM = Zn + monensina. Se determinó consumo de materia seca (DMI), digestibilidad (DMD), ganancia de peso (ADG) y eficiencia de conversión alimenticia (F/G). Análisis de sangre incluyeron: hematocrito, glucosa, urea, proteína total, fosfatasa alcalina y creatinina. En Exp2, el líquido ruminal de cuatro novillos fistulados sujetos a tratamientos idénticos fue analizado para: concentración de Zn, pH, NH 3 -N, VFA. Se determinó dilución de fase líqui-da, tiempo de recambio y volumen ruminal; y degradación in situ de cebada y alfalfa. En Exp1 no se observó respuesta a los tratamientos para DMI, ADG y DMD. Las diferencias no fueron significativas para F/G, a pesar de una disminución en M (6,6 kg kg -1 ). Tampoco fueron observadas diferencias para variables sanguíneas. En Exp2, se detectó una interacción tratamiento × tiempo (P = 0,0174) para concentración de Zn; ZM resultó mayor para todos los intevalos de tiempo, seguido de Z. ...

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Section: Ruminal Fluid Kinetics and Degradation Of Dietary Componentsmentioning

confidence: 99%

Effects of dietary addition of zinc and(or) monensin on performance, rumen fermentation and digesta kinetics in beef cattle

Arelovich

Laborde

Amela

et al. 2008

Span. j. agric. res.

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“…Gut-reactor and cost-benefit models of food intake have not been rigorously tested. Models which integrate a number of mechanisms (Poppi et al 1994;Illius et al 2000) show that it is possible for more than one mechanism to be limiting, and suggest that metabolic mechanisms may be more important for food regulation than previously thought. The overall impression is of several possible mechanisms, where each mechanism plays some part in regulating food intake.…”

Section: Discussionmentioning

confidence: 99%

“…The animal science and ecological literature associated with food intake is vast, and we review only the most recent literature (for reviews of animal science literature, see Forbes & France, 1993;Ingvartsen, 1994;Mertens, 1994;Allen, 1996;Poppi, 1996;Pitroff & Kothmann, 1999;Baumont et al 2000, Illius et al 2000; for reviews of the animal ecology literature, see Stephens & Krebs, 1986;Hughes, 1993;Perry & Pianka, 1997;Belovsky et al 1999).…”

Section: Food Intake Model: Eating To Requirements: Ingestion Constramentioning

confidence: 99%

“…Digestion compartment models of ruminant intake are reviewed along with metabolic models and some other approaches by Mertens (1994), Illius & Allen (1994) and Illius et al (2000). Compartment models assume that food intake is governed wholly by the rate of digesta clearance from the rumen.…”

Section: Digestion Modelsmentioning

confidence: 99%

“…Digestion and ingestion models can be combined with other processes to give an integrated model Poppi et al 1994;Sauvant et al 1996;Armstrong et al 1997;Illius et al 2000). Poppi et al (1994) extended a model of energy metabolism of absorbed nutrients originally developed by Gill et al (1984).…”

Section: Integrated Modelsmentioning

confidence: 99%

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Theoretical developments in the study and prediction of food intake

Yearsley¹,

Tolkamp

Illius

2001

Proc. Nutr. Soc.

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The purpose of the present paper is to review recent theoretical developments in food intake modelling applied to animal science and ecology. The models are divided into those that have been developed for intensive agricultural systems, and those which consider more extensive systems and natural systems. For the most part the present paper discusses models that predict the food intake of herbivores. The mechanisms of each model are discussed, along with a brief mention of the experimental support for the most popular models. We include a discussion of models that approach the study of food intake behaviour from an evolutionary perspective, and suggest that lifetime models are especially useful when food intake carries an intrinsic cost. These long timescale evolutionary models contrast with the more common food intake models, whose timescale is usually much shorter. We conclude that the 'eating to requirements' model highlights an important food intake mechanism that provides an accurate predictive tool for intensive agricultural systems. The mechanisms of food intake regulation in extensive systems are less certain, and closer links between the ideas of animal science and ecology will be helpful for improving our understanding of food intake regulation. Food intake model: Eating to requirements: Ingestion constraint: Digestion constraintFood intake is one of the most important aspects of an animal's life history. Explaining food intake behaviour has correspondingly generated a large amount of research interest in the fields of animal ecology, animal science and medicine. Despite studying the same basic subject, these different fields have developed independently of one another, possibly due to their different research goals. The present paper reviews the recent theoretical approaches in the study of food intake for animal science and ecology, but does not look at the medical literature.The animal science and ecological literature associated with food intake is vast, and we review only the most recent literature (for reviews of animal science literature,

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