Simulation of growth and production in sheep-model 1: A computer program to estimate energy and nitrogen utilisation, body composition and empty liveweight change, day by day for sheep of any age

Graham, N. McC.; Black, J. L.; Faichney, GJ; Arnold, GW

doi:10.1016/0308-521x(76)90010-x

Cited by 54 publications

(15 citation statements)

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“…Searle et al (1982) observed that each kg of live-weight gain, in two genotypes of lamb, contained 326 g chemical fat in fast growing lambs (200 g/day) but 432 g fat in lambs growing at ca. The reduced P : E ratio of the diet in the slow-growing lambs resulted in a greater amount of ME being available for growth which was directed towards fat gain, rather than lean, as postulated by Black (1974) and Graham, Black, Faichney and Arnold (1976), and since confirmed by 0rskov, MacLeod, Fahmy, Istasse and Hovell (1983) using cattle. This compared with 145 g and 326 g dissected fat per kg live-weight gain in this experiment; the difference being due to fat in muscle, bone and internal organs not being measured by dissection techniques.…”

Section: Lambs At the Same Live Weight But Different Ages (H And Ll)mentioning

confidence: 82%

Fat partitioning and tissue distribution in crossbred ewes following different growth paths

Butler-Hogg¹,

Johnsson²

1986

Anim. Sci.

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Forty Hampshire Down x Mule (Blue-faced Leicester cf X Swaledale 2) ewe lambs, obtained within a week of birth, were reared on milk replacer and from 6 weeks of age on a complete pelleted diet. Food intake of individual lambs was controlled to produce periods of high (H: ca. 210 g/day) and low (L: ca. 110 g/day) rates of live-weight gain from 4 to 20 and 20 to 36 weeks of age. Groups of eight lambs were slaughtered and dissected at 20 weeks having followed either growth paths H or L, and at 36 weeks having followed growth paths LL, HL or LH.Growth path had little effect on the lean or bone content of the carcass, but had a significant effect on carcass fat content and distribution. At the same carcass weight, the ratio of intermuscular to subcutaneous fat was higher in leaner carcasses. When compared at the same weight (ca. 35 kg) but different ages (H, 20 weeks; LL 36 weeks), the slower growing LL lambs contained 1-22 kg more fat than the H lambs, primarily in the intermuscular and subcutaneous depots but also in the internal omental depot. At the same age and weight (ca. 36 weeks and 48 kg), lambs which had followed the growth path LH contained 2-5 kg more fat than lambs which had followed the HL path. These differences in fatness are thought to have come about through changes in the effective protein : energy ratio of the diet, induced by the manipulation of food intake.Carcasses of HL lambs would be of more value to the meat trade compared with LH, since they would require less fat trimming before retail sale.

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Section: Lambs At the Same Live Weight But Different Ages (H And Ll)mentioning

confidence: 82%

Fat partitioning and tissue distribution in crossbred ewes following different growth paths

Butler-Hogg¹,

Johnsson²

1986

Anim. Sci.

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“…Maintenance The maintenance requirements of the animal are calculated from Graham et al (1976). From equations 2 a and 2b the rate of body-weight gain is The energy required for maintenance (EMa) is (Graham et al 1976, p. 124) ( 40 4where Wmet and Edig are given by equations 5 and 9 d. This energy is provided at the expense of the ATP pool, giving an ATP utilization rate for maintenance of EM, = 0.257 W e-o.oo0219(t-s8) + 2.8 ~ dWbody + 0.046Edig, where EAt is the energy content of ATP (MJ/kg mol), and is given by available at https:/www.cambridge.org/core/terms.…”

Section: ( 3 3mentioning

confidence: 99%

Simulation of the Metabolism of Absorbed Energy-Yielding Nutrients in Young Sheep: Efficiency of Utilization of Lipid and Amino Acid

Black

Gill

Thornley

et al. 1987

The Journal of Nutrition

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A previously described mathematical model that simulates the metabolism of absorbed nutrients in a sheep weighing 25 kg was used to examine the effects of altering lipid and amino acid absorption, and the potential of the animal to deposit protein on the efficiency of utilization (kf) of metabolizable energy. The predicted kf of energy from lipid added to several diets ranged from 0.65 to 0.74 and was influenced by both the protein and glucose content of the diet. The highest efficiency occurred when body protein deposition was limited by amino acid absorption. Lower values occurred with high protein diets when the proportion of body energy deposited as fat declined and, with low protein diets, when NADPH supply limited the synthesis of fatty acids from acetyl-CoA. Predicted kf of energy from amino acid added to several diets ranged from 0.003 to 0.47. Low values occurred when protein synthesis was limited by amino acid absorption; an increase in amino acid supply increased ATP utilization for protein synthesis and substantially reduced fat deposition with little resulting change in energy retention. The higher values occurred when most of the additional amino acid was oxidized. Glucose supply increased the kf of added amino acid primarily by reducing the synthesis of glucose from amino acids. Predicted kf of a whole diet generally declined as the proportion of protein in the diet increased. However, when the balance of absorbed nutrients was such that fat synthesis was limited by the supply of NADPH, kf increased with increasing dietary protein. Predicted kf of a diet also declined when the proportion of body energy deposited as protein increased, except when fat synthesis was limited by the supply of NADPH. The predictions suggest that kf is determined primarily by the energetic efficiency of biochemical reactions for maintenance and growth. However, most kf values less than 0.5 were associated with a flux of more than 1 g mol/d of ATP through the degradation pathway (representing substrate cycles) that occurred when NADPH supply limited the synthesis of fatty acids from acetyl-CoA.

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“…For example, Gill et al (1984) used the empirical relationship of Black & Griffiths (1975) to estimate the maximum rate of protein synthesis and the empirical equation of Graham et al (1976) to calculate maintenance energy requirements. Similarly, Pettigrew et al (1989) estimated values for maximum reaction rates and for affinity and inhibition constants from empirical data on such measures as body protein, fat depletion and milk yield of sows.…”

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confidence: 99%

Merits of empirical and mechanistic approaches to the study of the energy metabolism

McCracken¹

1992

Proc. Nutr. Soc.

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The title implies a clear separation of two approaches to the understanding of energy metabolism, which seldom, if ever, applies. Those empirical relationships which have stood the test of time were based on the concept of some uniformity of physiological function arising from an underlying and universal mechanism. Conversely the most sophisticated computer simulations of energy metabolism from cellular kinetics ultimately depend on empirical relationships which can be validated only by accurate measurements of whole-body energy expenditure.However, there are marked differences of philosophy and of purpose between empirical and mechanistic approaches. These were succinctly described by Baldwin & Miller (1989), and the author can do no better than to paraphrase two paragraphs of their comments.'The term empirical is appropriate to describe models/equations wherein data obtained in input:output animal experiments were used to parameterize equations. In a strict sense the only restriction imposed on defining empirical equations is that the equations should best describe relationships among two or more variables, i.e. the equations need not imply anything about underlying/metabolic relationships. Many models based on empirical relationships have been developed and have been useful when applied carefully and with appropriate recognition of the limitation that such equations only apply within the range and conditions of the collected data used to parameterize the model.Mechanistic models/equations, by definition are based on our understanding of underlying cause-and-effect relationships and should apply to a wide range of conditions. The use of the term mechanistic implies that our knowledge of the system is complete and, further, that sufficient biochemical, physiological and metabolic data are available to parameterize all the mechanistic equations in the model. This is rarely, if ever, the case. ' The main purpose of empirical relationships in the field of energy metabolism, as in other aspects of biological science, has been to identify and quantify the degree of uniformity of biological function within and between species. The secondary purpose has been to apply these relationships in order to determine energy requirements for different species in relation to specific physiological status, and this has been the cornerstone of development of feeding systems for animal production and of recommended dietary intakes for humans. Most notable among the empirical relationships are those relating to the allometry of growth and organ development, the surface area law and the inter-specific relationship between basal metabolism and metabolic body size. During the 1970s the increased availability of personal computers, coupled with the vast data pools which had been accumulated during the previous 20 years, gave an impetus to the development of complex factorial models such as the Edinburgh pig model (Whittemore available at https://www.cambridge.org/core/terms. https://doi

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Simulation of growth and production in sheep-model 1: A computer program to estimate energy and nitrogen utilisation, body composition and empty liveweight change, day by day for sheep of any age

Cited by 54 publications

References 54 publications

Fat partitioning and tissue distribution in crossbred ewes following different growth paths

Fat partitioning and tissue distribution in crossbred ewes following different growth paths

Simulation of the Metabolism of Absorbed Energy-Yielding Nutrients in Young Sheep: Efficiency of Utilization of Lipid and Amino Acid

Merits of empirical and mechanistic approaches to the study of the energy metabolism

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