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Journal ArticleDOI

Regulation of Food Intake in Ruminants. 6. Influence of Caloric Density of Pelleted Rations

01 Mar 1970-Journal of Dairy Science (Elsevier)-Vol. 53, Iss: 3, pp 311-316
TL;DR: In this article, the authors evaluated 40 rations with varying digestibility and density and found that fill limited intake of these sheep when the digestible energy of the rations was less than 2.5 kcal/g, whereas above this level energy intake was regulated.
About: This article is published in Journal of Dairy Science.The article was published on 1970-03-01 and is currently open access. It has received 81 citations till now. The article focuses on the topics: Dry matter.
Citations
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Book ChapterDOI
02 Nov 2015
TL;DR: Although intake is more important than digestibility in assessing forage quality, progress in understanding the basic factors that affect intake has been hampered by the inability to measure it accurately and to separate the influences of animal and diet on intake.
Abstract: Forage quality can be assessed in terms of the animal performance that is elicited when the forage is offered to the animal. Animal performance is the product of supply, nutrient and energy concentration, intake, digestibility, and metabolism. Typically, forage quality is measured assuming that the forage is freely available and that deficient nutrients other than protein and energy are provided in a supplement. Of the remaining factors affecting forage quality, intake is the most important one affecting animal performance. Reid (1961) listed the amount of forage eaten as the first factor limiting the usefulness of forage-testing schemes. His list also included the effect of concentrates on the amount of forage eaten, degree of selective feeding, and effect of physical form as important information not provided by the forage testing systems used at that time. Unfortunately, intake, substitution rates, selection, and physical form still are not a part of routine forage evaluation systems in the 1990's. Animal performance depends on the intake of digestible and metabolizable nutrients. Of the variation in digestible dry matter (DDM) or digestible energy (DE) intake among animals and feeds, 60 to 90% is related to differences in intake, whereas only 10 to 40% is related to differences in digestibility (Crampton et al., 1960; Reid, 1961). Intake generally accounts for twice as much variability in DDM intake as does digestibility (Milford, 1960; Ingalls et al., 1965). Milford and Minson (1966) observed that DDM intake is more closely correlated with dry matter intake (DMI) than any other feed or animal characteristic. Similarly, high correlations would occur between DMI and metabolizable (ME) or net energy (NE) intake, and between DMI and overall animal performance when forages are fed. The primary importance of intake in assessing forage quality does not mean that digestibility or metabolizability of nutrients are invariant or unimportant. Metabolizability can vary depending on the amounts and ratios of absorbed nutrients, the individual and interacting biochemical pathways of nutrient conversion and the type of animal production (MacRae et al., 1985; Blaxter, 1989). However, differences in the efficiency of converting DE to ME are small compared to differences in intake and digestibility, and the metabolic conversion of DE to ME or NE is typically considered to be relatively constant within type of production, such as maintenance, growth, pregnancy, or lactation (Moe and Tyrrell, 1976; NRC, 1989). Digestibility of forages is more variable than metabolizability, and feces typically are the greatest loss of ingested nutrients and energy. Extensive research has been devoted to measuring digestibility and relating it to feed characteristics because digestibility can be accurately measured with relative ease compared to DMI. Although intake is more important than digestibility in assessing forage quality, progress in understanding the basic factors that affect intake has been hampered by our inability to measure it accurately and to separate the influences of animal and diet on intake. Thus, we routinely use availability information (DE, ME, andNE)

784 citations

Journal ArticleDOI
TL;DR: Simulations based on the energy-intake model suggest a number of key environmental factors that should determine the impact of forage maturation and spatial variation on herbivore distribution patterns.
Abstract: Three general hypotheses have been proposed to explain why many large herbivores have highly aggregated patterns of distribution: dilution of predation risk, maintenance of forage in an immature bu...

437 citations

MonographDOI
27 Jun 2002
TL;DR: An adaptive resource ecology: foundation and prospects References Index.
Abstract: The adaptation of herbivore behaviour to seasonal and locational variations in vegetation quantity and quality is inadequately modelled by conventional methods. Norman Owen-Smith innovatively links the principles of adaptive behaviour to their consequences for population dynamics and community ecology, through the application of a metaphysiological modelling approach. The main focus is on large mammalian herbivores occupying seasonally variable environments such as those characterised by African savannahs, but applications to temperate zone ungulates are also included. Issues of habitat suitability, species coexistence, and population stability or instability are similarly investigated. The modelling approach accommodates various sources of environmental variability, in space and time, in a simple conceptual way and has the potential to be applied to other consumer-resource systems. This text highlights the crucial importance of adaptive consumer responses to environmental variability and is aimed particularly at academic researchers and graduate students in the field of ecology.

239 citations

Journal ArticleDOI
TL;DR: Body size and physiological status of ruminants appear to have the largest effect of animal-related factors in governing level of voluntary intake and kind and amount of supplementation, forage availability, and grazing intensity are major management-controlled variables affecting intake by domestic range ruminant.
Abstract: Variation in voluntary forage intake is undoubtedly the major dietary factor determining level and efficiency of ruminant production. This variation is largest and least predictable for grazing ruminants. Range ruminant productivity and efficiency is relatively low due, in part, to intake limitations; therefore, productivity could probably be increased most by increasing intake. Most available literature points to digestibility and rate of ingesta passage and reticula-rumen fill as primary mechanisms of intake regulation in range ruminants. Body size and physiological status of ruminants appear to have the largest effect of animal-related factors in governing level of voluntary intake. Kind and amount of supplementation, forage availability, and grazing intensity are major management-controlled variables affecting intake by domestic range ruminants.

221 citations


Cites background from "Regulation of Food Intake in Rumina..."

  • ...A study by Dinius and Baumgardt (1970) showed little difference in voluntary intake when forage energy digestibility was expressed on a weight or volume basis....

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Journal ArticleDOI
TL;DR: This study indicated that meat production from sheep in Oman will be improved in form of higher BW gains and better carcass composition by increasing energy levels in the diet.

150 citations

References
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Journal ArticleDOI
TL;DR: It was concluded that physical and physiological factors regulating feed intake change in importance with increasing digestibility, and intake appeared to be dependent on metabolic size, production, and digestibility at higher digestibilities.

456 citations

Journal ArticleDOI
TL;DR: A series of experiments with adult sheep were carried out in an attempt to place on a quantitative basis the generalisation that the voluntary food intake of ruminants increases with the quality of the fodder they are given.
Abstract: 1. A series of experiments with adult sheep were carried out in an attempt to place on a quantitative basis the generalisation that the voluntary food intake of ruminants increases with the quality of the fodder they are given.2. Methods of determining voluntary intake free of subjective bias were developed. It was shown that voluntary intake varied with a fractional power of body weight close to 0·734. The length of time necessary to establish stable intakes was 12–15 days and the number of times fresh food was offered each day had no apparent effect on intake.3. It was found that voluntary intake of long fodders was related to the apparent digestibility of their energy, increasing rapidly as digestibility increased from 38% to 70% and thereafter more slowly.4. The giving of concentrated food resulted in a drop in the voluntary intake of fodder. With high quality hay 100 g. concentrates replaced 100 g. hay. With poor quality hay, 100 g. concentrates replaced 47 g. of hay.5. The passage of three widely different hays through the gut was measured and the poorest passed most slowly. Calculations showed that the dry matter content of gut contents was the same for all three materials irrespective of their quality.6. It was shown that an increase in digestibility of 10 units in the range 40–60% resulted in considerable increases in the total amount of energy apparently digested and in equivalent increases in daily gain.7. The digested energy consumed/day/kg. W0·734 (E) can be related to voluntary intake (I) g./day/kg. W0·734 by the equation:—E=4·(I—31)which provides a rapid and easy method of assessing fodder quality under conditions of ad libitum supply.8. The results are discussed and it is shown that under ad libitum feeding conditions an increase in the nutritive value of unit feed from 50 to 55, i.e. by 10%, increases body gain by 100%.

356 citations