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Kirkland RM, Gordon FJ. The effects of milk yield and stage of lactation on the partitioning of nutrients in lactating dairy cows. J Dairy Sci 2001; 84:233-40. [PMID: 11210038 DOI: 10.3168/jds.s0022-0302(01)74473-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective of the experiment was to examine, using indirect calorimetry, the effects of milk yield and stage of lactation on the response in milk and body tissue energy, and heat production, to a reduction (decrement) in nutrient intake (assessed as metabolizable energy intake). Eight lactating dairy cows, four representing each of two stages of lactation [either mean initial days in milk (DIM) 158 (SD 6.1) or 414 (SD 51.1)] were used. Each cow underwent four 17-d periods incorporating two physiological states [number of mammary glands milked: either four (periods 1 and 2), or two (periods 3 and 4)], and two levels of metabolizable energy intake within each physiological state [either sufficient to meet requirements for zero tissue balance plus 10 MJ/d (periods 1 and 3)] or these allowances reduced by 20 MJ/d in the subsequent period (periods 2 and 4, respectively). Partitioning was calculated from the changes in metabolizable energy intake, milk energy, tissue energy, and heat production between DIM groups and between four and two gland milking (milk yield) components of the study. Partitioning of the changes in metabolizable energy intake was not influenced by DIM, but milk yield response was greater in the early lactation cows compared with the late group. Cows milked in four glands (higher milk yield) partitioned a significantly greater proportion of decremental changes in metabolizable energy intake to milk energy and less to tissue energy, than when milked in only two glands (lower milk yield).
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Affiliation(s)
- R M Kirkland
- The Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down.
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52
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Mackle TR, Dwyer DA, Ingvartsen KL, Chouinard PY, Ross DA, Bauman DE. Effects of insulin and postruminal supply of protein on use of amino acids by the mammary gland for milk protein synthesis. J Dairy Sci 2000; 83:93-105. [PMID: 10659969 DOI: 10.3168/jds.s0022-0302(00)74860-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We examined the relationships between amino acid supply, net utilization of amino acid by the mammary gland, and milk protein yield, in investigations that utilized a hyperinsulinemic-euglycemic clamp. A two-way crossed factorial design was employed. There were two 12-d periods involving abomasal infusions of either water or a mixture of casein (500 g/d) plus branched-chain amino acids (88 g/d), with a hyperinsulinemic-euglycemic clamp during the last 4 d of each period. During the clamp, insulin was infused at 1.0 microg x kg BW(-1) x h(-1) to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. The insulin clamp treatments increased milk protein yield by 15 and 25% during abomasal infusion of water or casein plus branched-chain amino acids, respectively. Circulating concentrations of essential amino acids were reduced (33%) during insulin clamp treatments, especially branched-chain amino acids (41%). Arteriovenous difference of essential amino acids across the mammary gland was linearly related to their arterial concentrations. However, milk protein yield was not related to either arterial concentration or arteriovenous difference, for any of the essential amino acids. During insulin clamp treatments, the mammary gland was able to support the increased milk protein yields by increasing extraction efficiency of essential amino acids, mammary blood flow, and glucose uptake. Furthermore, a positive mammary balance of total amino nitrogen and carbon was maintained for all treatments. These adaptations demonstrate the unique ability of the mammary gland to adjust local conditions to allow for an adequate nutrient supply.
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Affiliation(s)
- T R Mackle
- Department of Animal Science, Cornell University, Ithaca, NY 14853-4801, USA
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53
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McNamara JP, Baldwin RL. Estimation of parameters describing lipid metabolism in lactation: challenge of existing knowledge described in a model of metabolism. J Dairy Sci 2000; 83:128-43. [PMID: 10659973 DOI: 10.3168/jds.s0022-0302(00)74864-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have been conducting research to improve quantitative descriptions of metabolism in lactating dairy cows depicted in an existing mechanistic, computer-assisted model. The model is dynamic and deterministic and is based on biochemical equations describing ruminal fermentation and chemical interactions in body tissues. The objective was to challenge this model with data collected in in vivo and in vitro experiments on high producing dairy cattle fed a range of energy. Cows that varied in genetic propensity for milk production (7045 to 12,909 kg of milk/305 d), lactation number (1 to 4), stage of lactation (-30 to 345 d in milk), and rate of intake (14 to 29 kg/d of dry matter) and that were fed various energy-yielding feedstuffs were used. Dietary inputs, milk component outputs, body fat, nutrient concentrations in blood, and maximal velocity and substrate sensitivity of adipose tissue metabolic reactions were observed. Model simulations were conducted; simulated yields of milk components for a 305-d lactation were within 5% of observed means. Simulated lipid metabolism and accumulation of body fat were adequate in many situations; however, the model response to changes in energy intake was too sensitive. This inadequacy was especially noticeable in later lactation because of inadequate representation of dynamic responses over periods more than a few weeks long. The model behaves consistently with biochemical principles, behavior was in the correct direction, and precision was adequate for many variables. Lack of precision in long-term dynamic changes indicates that the parameters describing energy-utilizing reactions are inadequate. This severe challenge of the model supports its functionality. Further experiments must be designed to determine how nutrients in viscera, muscle, and adipose tissue are used; these experiments must encompass sufficient range in genetic ability, nutrient input, and time to adequately describe the dynamic and integrated nature of metabolic reactions.
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Affiliation(s)
- J P McNamara
- Department of Animal Sciences, Washington State University, Pullman 99164-6351, USA
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54
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Rotz CA, Mertens DR, Buckmaster DR, Allen MS, Harrison JH. A dairy herd model for use in whole farm simulations. J Dairy Sci 1999; 82:2826-40. [PMID: 10629832 DOI: 10.3168/jds.s0022-0302(99)75541-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A dairy herd submodel was created for integration with other farm submodels to form DAFOSYM, a dairy farm simulation model. The herd submodel determines the best mix of available feeds to meet the fiber, energy, and protein requirements for each of six animal groups. The groups are early-, mid-, late-, and nonlactating cows, heifers over 1 yr old, and younger heifers. Feed intake, milk production, and manure dry matter and nutrient (N, P, and K) excretions are functions of the nutrient content of the diets. Required feed characteristics include crude protein, rumen degradable protein, acid detergent insoluble protein, net energy of lactation, neutral detergent fiber, total digestible nutrients, P, and K concentrations. Feed intake is predicted with fill and roughage units. These units are functions of feed neutral detergent fiber adjusted for particle size distribution and the relative rate of ruminal digestibility or physical effectiveness of the fiber. The herd submodel predicted feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or measured for dairy animals. When integrated with other farm components in DAFOSYM, the comprehensive model provides a useful tool for evaluating the long-term performance and economics of alternative dairy farm systems.
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Affiliation(s)
- C A Rotz
- USDA/Agricultural Research Service, University Park, PA 16802, USA
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55
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Hanigan MD, Cant JP, Weakley DC, Beckett JL. An evaluation of postabsorptive protein and amino acid metabolism in the lactating dairy cow. J Dairy Sci 1998; 81:3385-401. [PMID: 9891282 DOI: 10.3168/jds.s0022-0302(98)75903-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The current protein system utilized in the US was formulated in 1985 with minor modifications in 1989 and has gained widespread acceptance. However, some of the assumptions that were adopted by the National Research Council (NRC) appear to be inconsistent with observational data. The marginal efficiency of conversion of absorbed protein to milk protein was assumed by NRC to be 70% until the requirement for absorbed protein was met and was 0% thereafter. The mean marginal efficiency observed for abomasal casein infusions reported in the literature and collected at the Purina Mills Research Center was 21%. Sorting the data into protein-sufficient and protein-deficient classes did not support the assumptions of 70% marginal efficiency in a deficient state and 0% marginal efficiency in the sufficient state. Analyses of nitrogen balance data and abomasal flow data and the work of Van Straalen et al. (77) indicated that energy status of the animal plays a role in determining the response to absorbed protein. Such a consideration was not included in the NRC model. The adoption of equations that describe metabolism at the organ level as opposed to the animal level would allow direct use of organ level data for parameterization and may provide better predictions. Simple representations of digestion and absorption, splanchnic metabolism, and mammary metabolism of amino acids or protein in aggregate are described. These representations could be used to improve the current system and could serve as a bridge to adoption of more complex models.
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Affiliation(s)
- M D Hanigan
- Dairy Research Group, Purina Mills, Inc., St. Louis, MO 63144, USA
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56
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van der Honing Y. Perspectives of future feed information based on energy and nutrient availability. ARCHIV FUR TIERERNAHRUNG 1998; 51:135-53. [PMID: 9672712 DOI: 10.1080/17450399809381914] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The need for improvement of feed information in future is discussed from the perspective for implementation in practice. Weaknesses of the current feed evaluation systems, energy systems in particular, are described: prediction of voluntary feed intake, additivity of digestibilities of individual feedstuffs and dynamics of digestion, efficiency of utilization of energy and variation in maintenance requirements. A brief inventory of models to quantify energy and nutrient metabolism by farm animals is followed by an overview of aspects required to fulfill the demands for a nutrient-oriented feed evaluation. These include feed characteristics to determine and animal aspects, as well as involvement of environmental and management factors. The need for better harmonization of methods and quality of feed information and for international coordination in this matter is underlined.
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Affiliation(s)
- Y van der Honing
- Institute for Animal Science and Health (ID-DLO), Lelystad, The Netherlands
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57
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58
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Pettigrew JE. Mathematical modelling of nitrogen flow in growing pigs and lactating sows. Proc Nutr Soc 1997; 56:645-56. [PMID: 9264114 DOI: 10.1079/pns19970064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present paper describes both nutrient-partitioning and metabolic models as applied to pigs. It is suggested that nutrient-partitioning models are most useful for use as management aids for commercial pork production, but that metabolic models may be more useful in understanding biological mechanisms. There is a pressing need for more quantitative information on potential protein deposition rates, the relationship between protein deposition and energy intake, endogenous amino acid losses, and metabolic effects on reproduction, all under varying conditions of genetic strain, health, ambient temperature, stocking density, and other factors.
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Affiliation(s)
- J E Pettigrew
- Department of Animal Science, University of Minnesota, St. Paul 55108, USA
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59
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Hanigan MD, Dijkstra J, Gerrits WJ, France J. Modelling post-absorptive protein and amino acid metabolism in the ruminant. Proc Nutr Soc 1997; 56:631-43. [PMID: 9264113 DOI: 10.1079/pns19970063] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- M D Hanigan
- Dairy Research Group, Purina Mills, Inc., St Louis, MO 63144, USA
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60
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Oldham JD, Emmans GC, Kyriazakis I. Limits and limitations to nitrogen use in farm animals. Proc Nutr Soc 1997; 56:525-34. [PMID: 9264105 DOI: 10.1079/pns19970055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- J D Oldham
- Genetics and Behavioural Sciences Department, SAC, Bush Estate, Penicuik, Midlothian
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61
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Gerrits WJ, Dijkstra J, France J. Description of a model integrating protein and energy metabolism in preruminant calves. J Nutr 1997; 127:1229-42. [PMID: 9187640 DOI: 10.1093/jn/127.6.1229] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
This paper describes the development of a mechanistic model integrating protein and energy metabolism in preruminant calves of 80-240 kg live weight. The objectives of the model are to gain insight into the partitioning of nutrients in the body of growing calves and to provide a tool for the development of feeding strategies for calves in this weight range. The model simulates the partitioning of nutrients from ingestion through intermediary metabolism to growth, consisting of accretions of protein, fat, ash and water. The model contains 10 state variables, comprising fatty acids, glucose, acetyl-CoA and amino acids as metabolite pools, and fat, ash and protein in muscle, hide, bone and viscera as body constituent pools. Turnover of protein and fat is represented. The model also includes a routine to check possible dietary amino acid imbalance and can be used to predict amino acid requirements on a theoretical basis. The model is based on two experiments, specifically designed for this purpose. Simulations of protein and fat accretion rates over a wide range of nutrient input suggest that the model is sound. In can be used as a research tool and for the development of feeding strategies for preruminant calves.
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Affiliation(s)
- W J Gerrits
- Wageningen Institute of Animal Sciences, Wageningen Agricultural University, The Netherlands
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62
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Affiliation(s)
- J P McNamara
- Department of Animal Sciences, Washington State University, Pullman 99164-6320, USA
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63
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64
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Chalupa W, Sniffen CJ. Protein and amino acid nutrition of lactating dairy cattle—today and tomorrow. Anim Feed Sci Technol 1996. [DOI: 10.1016/0377-8401(95)00874-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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65
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McNamara JP, Harrison JH, Kincaid RL, Waltner SS. Lipid metabolism in adipose tissue of cows fed high fat diets during lactation. J Dairy Sci 1995; 78:2782-96. [PMID: 8675761 DOI: 10.3168/jds.s0022-0302(95)76909-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The adaptations of fat synthesis in adipose tissue to lactational state, rate of milk production, and dietary fat intake were determined for dairy cows. Lipogenesis and esterification were determined in cows of average or high genetic merit for milk production and fed either a control TMR of corn silage, alfalfa, and concentrate (2.5% fat; 1.47 Mcal of NEL/kg); a TMR with whole cottonseeds replacing 12% of the concentrate (4.4% fat; 1.49 Mcal NEL/kg); or a TMR with 12% cottonseeds and 2.7% of Ca salts of fatty acids (6.0% fat; 1.53 Mcal of NEL/kg). Dietary treatments began on d 17 of lactation and continued for 288 d. Lipogenesis and esterification decreased equally from 15 d prepartum to 15 d postpartum in all groups. Cows of high merit had lower rates of lipogenesis and esterification at d 60 than did low merit cows but had higher rates of lipogenesis at d 120. Rates of lipogenesis were decreased by dietary fat treatments. Esterification rates were lowest on the intermediate fat TMR and highest on the highest fat TMR. Lipogenesis was decreased logarithmically by dietary fat intake; this effect was greater as lactation progressed. Adipocyte size and body fat mass decreased during early lactation and then increased for all treatment groups. Supplemental dietary fat reduces de novo synthesis of fatty acid, and this effect increases as lactation progresses.
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Affiliation(s)
- J P McNamara
- Department of Animal Sciences, Washington State University, Pullman 99164-6320, USA
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66
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Cant JP, McBride BW. Mathematical analysis of the relationship between blood flow and uptake of nutrients in the mammary glands of a lactating cow. J DAIRY RES 1995; 62:405-22. [PMID: 7593827 DOI: 10.1017/s0022029900031113] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A dynamic mathematical model of blood flow regulation in the mammary glands of a lactating cow was constructed from a principle of local vasodilator release in response to changes in intracellular adenylate charge. An equation was derived to predict uptake of the milk precursors acetate, glucose, amino acids and fatty acids, as affected by mammary blood flow rate. Metabolism of the precursors to milk components and CO2 was simulated with a set of empirically derived equations. Relative rates of ATP production and utilization regulated both the number of perfused capillaries and the conductance of arteriolar segments in the mammary glands. The model simulated local control phenomena of functional and reactive hyperaemia, and simulation of autoregulation under changing arterial pressure suggested a predominance of precapillary sphincter regulation. It was predicted that an increase in blood flow without the mammary capacity to utilize blood metabolites efficiently would be detrimental to milk synthesis. Conversely, increased blood flow through changes in mammary activity resulted in predictions of higher milk production. It was proposed that the equation for uptake, [equation: see text] be used in analysis of mammary arteriovenous differences.
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Affiliation(s)
- J P Cant
- Department of Animal and Poultry Science, University of Guelph, Ontario, Canada
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67
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Baldwin RL, Emery RS, McNamara JP. Metabolic relationships in the supply of nutrients for milk protein synthesis: integrative modeling. J Dairy Sci 1994; 77:2821-36. [PMID: 7814748 DOI: 10.3168/jds.s0022-0302(94)77222-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The objective of research under the NC-185 regional project is to identify the critical chemical transformations in the rumen, digestive tract, gastrointestinal and splanchnic tissues, and adipose and mammary tissues that define patterns of nutrient utilization in lactating dairy cows. This objective includes research on differences in fermentation, digestion, absorption, and tissue utilization of nutrients in sufficiently different situations to permit estimation of parameters defining various nutrient interconversions. The regional project is utilizing dynamic, mechanistic models of metabolism as tools for integrative analyses of experimental data generated by the group. During the early phases of the project emphasized herein, primary emphasis was on development of models of adipose tissue, mammary gland, liver, rumen, and whole animal metabolism. Serious inadequacies exist in the detail and scope of knowledge of rates of chemical transformations across the wide range of milk yields and nutrient intakes found in production situations. Current knowledge, as described in the various equations and parameters in the models, is presented and discussed. Some characteristics of the current models are illustrated, and methods to utilize the models to identify important experiments are discussed. More cooperative efforts are necessary, including experimental designs that focus on quantification of relationships between input and output, physiological mechanisms that alter patterns of nutrient utilization in lactating dairy cows, and yield estimates of the parameters describing the pre- and postabsorptive uses of feed nutrients.
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Affiliation(s)
- R L Baldwin
- Department of Animal Science, University of California, Davis 95616-8521
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68
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69
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70
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Sniffen CJ, Beverly RW, Mooney CS, Roe MB, Skidmore AL, Black JR. Nutrient requirements versus supply in the dairy cow: strategies to account for variability. J Dairy Sci 1993; 76:3160-78. [PMID: 8227638 DOI: 10.3168/jds.s0022-0302(93)77655-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dairy producers must overcome substantial challenges to achieve milk outputs > 14,000 kg of milk/yr per cow within the next decade. To obtain high productivity, a more complete comprehension of the dynamics of metabolism, nutrient utilization, and nutrient absorption will enable better prediction of the efficiency of utilization of these nutrients. A better understanding of the dynamics of rumen function and a more accurate prediction of nutrient flow from the rumen are necessary. Grouping strategy and group feeding behavior influence cow productivity and farm profitability. Understanding of the variance of individual cow responses to management practice is critical. Feeding system design and management and diet formulation techniques need to be developed that recognize the dynamic nature of cow physiology and the variability in feedstuffs and cow requirements. These concepts need to be integrated into total farm management and require the use of new computer modeling technologies.
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Affiliation(s)
- C J Sniffen
- Department of Animal Science, Michigan State University, East Lansing 48824
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71
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Pettigrew J, McNamara J, Tokach M, King R, Crooker B. Metabolic connections between nutrient intake and lactational performance in the sow. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0301-6226(93)90187-m] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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72
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McNamara JP, Becker-Khaleel B, Parmley KL. Quantitative relationships between cyclic adenosine-3',5'-monophosphate and lipolysis in adipose tissue during the peripartum period. J Dairy Sci 1992; 75:1901-13. [PMID: 1323584 DOI: 10.3168/jds.s0022-0302(92)77950-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The objective was to study the control of lipolysis and to determine kinetic relationships between subcutaneous adipose tissue cyclic AMP concentrations and rates of lipolysis in primiparous dairy cows in late pregnancy and early lactation. Adipose tissue was biopsied from primiparous cows at -30, -15, -5, 5, 15, 30, and 60 d around parturition. Tissue was incubated with the following treatments: basal, no additions; isoproterenol at 10(-5) M; adenosine deaminase at 1 x 10(6) munits/ml; combined isoproteranol and adenosine deaminase; isoproteranol, adenosine deaminase, and 1 mM theophylline. Cyclic AMP was highest at .25 h and remained elevated for 2 h. Response of cyclic AMP at .25 h was 5-, 9-, 27-, and 38-fold for the four stimulatory treatments, respectively. Glycerol release at 2 h increased 3-, 2.3-, 2.7-, and 3-fold, respectively. Lipolysis was related logarithmically to cyclic AMP concentrations within and among treatments and times around parturition. Either logarithmic or Michaelis-Menten equations predicted similar maximum lipolysis but increased sensitivity to cyclic AMP in tissue from lactating compared with pregnant heifers. Thus, the sensitivity of response of lipolysis to cAMP may be increased in adipose tissue from first lactation cows. These relationships also may be useful in constructing and improving mechanistic models of adipose and whole animal metabolism.
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Affiliation(s)
- J P McNamara
- Department of Animal Sciences, Washington State University, Pullman 99164-6320
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73
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France J, Thornley J, Baldwin R, Crist K. On solving stiff equations with reference to simulating ruminant metabolism. J Theor Biol 1992. [DOI: 10.1016/s0022-5193(05)80642-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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74
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McCracken KJ. Merits of empirical and mechanistic approaches to the study of energy metabolism. Proc Nutr Soc 1992; 51:125-33. [PMID: 1508924 DOI: 10.1079/pns19920019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- K J McCracken
- Food and Agricultural Chemistry Department, Queen's University of Belfast, Northern Ireland
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75
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Tran CL, Johnson CL. Prediction of responses in milk constituents to changes in the nutrition of dairy cows. J DAIRY RES 1991; 58:373-81. [PMID: 1765587 DOI: 10.1017/s0022029900029976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Milk quotas, based on an average fat content, severely limit milk production on UK farms. Predictions of the time-course of lactation are incorporated into most computerized herd management programs but these models take no account of food inputs, body weight change or milk composition. Dynamic models are generally used to simulate metabolic pathways and, as such, have little direct relevance to commercial milk production. Dynamic models can be converted to an adaptive-predictive model that partitions food energy into milk and non-milk constituents. This paper reports the development of an adaptive-predictive model to partition food into milk and non-milk components. Additional functions further partition milk energy into the principal constituents, fat, protein and lactose.
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Affiliation(s)
- C L Tran
- Department of Animal Physiology and Nutrition, University of Leeds, UK
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76
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A review of empirical and mechanistic models of lactational performance by the dairy cow. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0301-6226(91)90061-t] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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77
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Chalupa W, Sniffen CJ. Protein and amino acid nutrition of lactating dairy cattle. Vet Clin North Am Food Anim Pract 1991; 7:353-72. [PMID: 1893276 DOI: 10.1016/s0749-0720(15)30798-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This article describes the National Research Council Model of protein metabolism and illustrates its use in meeting the protein requirements of lactating cows. Attention is then directed toward amino acid nutrition with emphasis on the need for models to estimate amino acid requirements. Finally, the potential to improve productivity with rumen-protected amino acids is considered.
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Affiliation(s)
- W Chalupa
- Center for Animal Health and Productivity, University of Pennsylvania School of Veterinary Medicine, New Bolton Center, Kennett Square
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78
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Abstract
In the dairy cow, adipose tissue lipid accumulates during pregnancy, and catabolism begins prior to parturition and increases dramatically afterward. After peak lactation, body lipid is replenished. The duration and magnitudes of these adaptations depend on milk energy secretion, net energy intake, genotype, and endocrine environment. Recent research efforts have focused on endocrine, genetic, and biochemical mechanisms underlying metabolic adaptations in cows of high production potential. Adipose tissue lipid synthesis is decreased and lipolysis is increased in early lactation. The magnitude and duration of these adaptations are increased in animals either consuming relatively less energy or producing more milk. Adipose tissue is more responsive to catecholamines in early and midlactation and in animals with higher production. This is more of an increase in maximal response than in sensitivity. In vivo and in vitro rates of adipose tissue lipolysis correlate positively with milk energy secretion, whereas lipid synthesis rates correlate with energy intake. Thus, mammary metabolic activity, within and among lactations, correlates with that in adipose tissue. Likely mechanisms include adaptations in receptors for homeostatic signals and modulation of postreceptor responses. Research is needed into neural, genetic, and hormone regulation of nutrient utilization and body fat use and recovery during lactation. Research should describe mechanistic relationships among nutrients in animals of high production as well as investigate cellular and molecular mechanisms suitable to genetic manipulation.
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Affiliation(s)
- J P McNamara
- Washington State University, Department of Animal Science, Pullman 99164-6320
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79
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Abstract
Nutritional science is developing from the calculation of requirements toward prediction of responses to nutrients. Responses are defined as the consequences of the animal's interaction with its feed and other aspects of its environment. For dairy cows the important responses to predict are yields of major milk constituents (fat, protein, and lactose), rates of changes of body fat and protein, and voluntary feed consumption. In order to make predictions of cow responses, equal weight needs to be given to quantitative descriptions of cow characteristics, feed characteristics, and relevant aspects of the environment. This paper presents a framework that allows quantitative descriptions of these various attributes to be combined for the purposes of response prediction. The nutrients of importance are those major end products of digestion, which act as substrates for the generation of animal products. Quantitative aspects of genotype include description of potential milk constituent yield, mature body size and composition, and rate of maturing, including a description of "labile" protein mass and animal capacities for ingestion of potentially constraining feed attributes. A variety of approaches is available to simulate nutrient supply and use for purposes of response prediction. The synthesis of such models adds both intellectual richness to the process of developing nutritional science and improved frameworks for testing theories through experiment.
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Affiliation(s)
- J D Oldham
- Edinburgh School of Agriculture, Scotland
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Baldwin RL, Thornley JH, Beever DE. Metabolism of the lactating cow. II. Digestive elements of a mechanistic model. J DAIRY RES 1987; 54:107-31. [PMID: 3819150 DOI: 10.1017/s0022029900025231] [Citation(s) in RCA: 149] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The structure and characteristics of a model suitable for estimating digestion within the rumen and rates and patterns of nutrient entry in lactating cows are presented. The model consists of 12 state variables comprising a large particle pool, small particle pools representing insoluble dietary nutrients, soluble pools representing soluble dietary nutrients, and fermentation intermediates and end products. The model was constructed assuming continuous feeding, using Michaelis-Menten or mass action kinetics. The computer program was written in ACSL to run on a VAX computer. A fourth-order Runge-Kutta procedure was used for numerical integration. Sensitivity and behavioural analysis demonstrated that overall stability and sensitivity of the model to individual parameters was generally satisfactory, but the need to improve the description and parameterization of aspects such as particle size in relation to availability, rate and affinity constants for amino acid degradation and rate constants for particle outflow from the rumen was established. Adjustments of the model to examine discontinuous feeding regimes were undertaken and initial results with respect to changes in fermentation rates, rumen acetate levels and microbial metabolism were considered realistic. Comparisons with experimental data were considered satisfactory on forage-based and medium concentrate-containing diets, but with diets comprising 90% cereal, some inconsistencies, especially with respect to predictions of volatile fatty acid production rates, were observed. Reasons for this are put forward and suggestions for improvements in the model are discussed.
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Baldwin RL, France J, Beever DE, Gill M, Thornley JH. Metabolism of the lactating cow. III. Properties of mechanistic models suitable for evaluation of energetic relationships and factors involved in the partition of nutrients. J DAIRY RES 1987; 54:133-45. [PMID: 3819152 DOI: 10.1017/s0022029900025243] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Two models of lactating dairy cows were constructed by combining mechanistic models of digestion and metabolism reported previously and by adding elements to allow simulation of changes in tissue metabolic capacities over time. One model (day version) had an integration interval of 0.005 d and was suitable for simulation of within-day dynamics of nutrient supply and partition. The other (lactation version) had an integration interval of 1 d and was suitable for simulation of full lactation cycles. A number of simulation analyses were conducted to characterize and evaluate the models, to examine quantitative and dynamic properties of mechanisms which influence partition of nutrients, to identify aspects requiring further study, and to illustrate the potential usefulness of mechanistic, as compared to empirical, models in analyses of energy balance in lactating dairy cows.
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