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Biomedical subjects

D G Fox

Publications and source records attributed to D G Fox.

At least 19 recordsLinked to original sources
PubMed1995

Application of the Cornell Net Carbohydrate and Protein model for cattle consuming forages.

Accurate prediction of forage biological values and performance with animals fed forages requires accurately accounting for factors that influence animal requirements and feedstuff utilization. The Cornell Net Carbohydrate and Protein System (CNCPS) is an application model that uses a combination of mechanistic and empirical approaches to account for the effects of variation in animal factors and feed carbohydrate and protein fractions on animal performance. Thus, accurate animal and environmental descriptions, DMI, feed carbohydrate, and protein fractions and their digestion rates are required inputs. In 25 growth periods with calves fed high-forage diets, the CNCPS accounted for 74, 81, and 83%, respectively, of the variation in ADG predicted to be supported by the ME, metabolizable protein, and essential amino acid intake, the first-limiting of all three accounting for 81% of the variation with a -1% bias. Thus, the CNCPS can be used to accurately describe forage quality and the effects of changes in forage composition on animal performance. The model was sensitive to variations in NDF, CP, protein solubility, NDF and starch digestion rates, feed and microbial amino acid composition, maintenance protein requirement, body protein amino acid content, and the coefficient of efficiency of use of absorbed protein. Analysis of several trials indicates an improved efficiency of ME use with improved amino acid balances. Uses of the CNCPS discussed include interpreting, planning and applying research, teaching, developing tables of requirements and biological values for feeds, complex nutritional accounting, and predicting performance and profits.

Animal Feed↗
PubMed1995

Influence of roughage and grain processing in high-concentrate diets on the performance of long-fed Holstein steers.

The effects of roughage source and timing of inclusion in high-concentrate diets on feedlot performance were evaluated in each of 2 yr with 144 and 120 long-fed Holstein steers, respectively. Roughage, when included in the diet, was delivered in a built-in-roughage (BIR) pellet supplying 15 and 6% roughage (percentage of DM) or hay crop silage (HCS) supplying 7 and 10% roughage (percentage of DM) for the growing and finishing periods, respectively. The six dietary treatments (two pens each) investigated were continuous whole corn and pelleted supplement (no added roughage; WSC-PEL); BIR with cracked corn either in the growing (BIR-G) or finishing (BIR-F) period with whole corn being fed with pelleted supplement when BIR was not part of the diet; BIR and cracked corn fed continuously (BIR-CONT); and two HCS treatments in which the corn was fed either whole (HCS-WSC) or cracked (HCS-CSC) for the entire feeding period. Replicates were slaughtered 4 and 3 wk apart for yr 1 and 2, respectively. Pooled daily gains (yr 1 and 2) for the entire trial (1.39 to 1.45 kg/d) were not different (P > .05). Daily DM and concentrate intakes were lower (P < .001) and gain efficiency was higher (P < .001) for the WSC-PEL than for the other treatments. Carcass characteristics were similar among treatments except for an improved yield grade (P < .02) for the HCS treatments over the BIR treatments. The WSC-PEL treatment was the most profitable (+/steer) and the BIR-CONT diet was the least profitable. The HCS treatments were the most profitable of the roughage treatments. A newly proposed intake prediction equation for feedlot cattle performed similarly to the 1984 NRC equation with long-fed Holstein steer calves.

Animal Feed↗
PubMed1994

Economic comparison of nutritional management strategies for Venezuelan dual-purpose cattle systems.

Objectives of this study were to compare three nutritional management strategies for dual-purpose herds in Venezuela in 1987 using a deterministic, multiperiod linear programming model of a representative farm. The model maximized discounted net margin (total revenues minus variable costs) from the herd for a 3-yr cow replacement cycle partitioned into six periods. The periods accounted for seasonal variation in forage availability and quality, and the model provided information about optimal animal inventories, animal sales, land in forage, and feed supplements. We compared current nutritional management practices and alternatives allowing optimal supplementation with commercial concentrate, molasses, cassava root, and urea. Iteration between the programming model and results from the Cornell Net Carbohydrate and Protein System assured technical coefficients consistent with predicted animal performance. Compared with management practices relying on commercial concentrate, optimal use of molasses and urea permitted increases in the stocking rate. Productivity and profit were restricted primarily by energy intake, which was constrained by intakes of NDF and DM. Alternative management strategies changed the relative importance of nutrient requirements and feed intake constraints. Thus, optimal interventions to alleviate nutritional constraints will vary with current management. Mobilizing adipose and protein tissues during lactation was optimal for most strategies. Supplementing with molasses and urea instead of commercial concentrate was the most profitable strategy, increasing herd net margin by 16% compared to the predominant feeding strategy in the late 1980s.

Adipose Tissue↗
PubMed1994

Predicting net energy and protein requirements for growth of implanted and nonimplanted heifers and steers and nonimplanted bulls varying in body size.

Energy and protein retained in 50, 38, and 54 nonimplanted Holstein and Angus heifers, steers, and bulls, respectively, 17 pens (237 cattle) of beef breed implanted heifers, and 65 pens (535 cattle) of beef breed implanted steers were compared to values predicted by the 1984 National Research Council (NRC), Cornell Net Carbohydrate and Protein System (CNCPS), and the model of Oltjen et al. (OLTJEN). The NRC accounted for 83, 85, 86, 88, and 88% of the variation in retained energy (RE) with biases of -8, +13, -6, +6, and -12% for nonimplanted heifers, implanted heifers, nonimplanted steers, implanted steers, and bulls, respectively. The CNCPS accounted for 93, 98, 92, 95, and 91% of the variation in RE with biases of +2, +10, -6, +1, and -13% for nonimplanted heifers, implanted heifers, nonimplanted steers, implanted steers, and bulls, respectively. OLTJEN accounted for 78, 76, 48, 93, and 96% of the variation with biases of -3, -2, +9, -8, and -1% for nonimplanted heifers, implanted heifers, nonimplanted steers, implanted steers, and bulls, respectively. For retained protein (RP), the NRC accounted for 57, 68, 70, 86, and 84% of the variation with biases of -12, -7, +16, -8, and -10% for nonimplanted heifers, implanted heifers, nonimplanted steers, implanted steers, and bulls, respectively. The CNCPS accounted for 69, 77, 84, 94, and 84% of the variation in RP with biases of -7, -11, 0, -3, and -9% for nonimplanted heifers, implanted heifers, nonimplanted steers, implanted steers, and bulls, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A net carbohydrate and protein system for evaluating cattle diets: IV. Predicting amino acid adequacy.

The Cornell Net Carbohydrate and Protein System was modified to include an amino acid submodel for predicting the adequacy of absorbed essential amino acids in cattle diets. Equations for predicting the supply of and requirements for absorbed essential amino acids are described and presented. The model was evaluated for its ability to predict observed duodenal flows of nitrogen, nonammonia nitrogen, bacterial nitrogen, dietary nonammonia nitrogen, and individual essential amino acids. Model-predicted nitrogen, nonammonia nitrogen, bacterial nitrogen, and dietary nonammonia nitrogen explained 93.2, 94.6, 76.4, and 79.3% of the observed duodenal flows, respectively, based on R2 values from predicted vs observed regression analysis. Based on slopes of regression lines, model-predicted duodenal nitrogen and nonammonia nitrogen were different from observed duodenal flows (P < .05), whereas model-predicted bacterial nitrogen and dietary nonammonia nitrogen were not different from observed duodenal flows (P < .05). Model-predicted duodenal flows of individual essential amino acids explained 81 to 90% of variation in observed duodenal amino acid flows. Based on slopes of regression lines, model-predicted duodenal threonine, leucine, and arginine were the only amino acids different from observed duodenal flows (P < .05). Ideas for further model improvements and research in amino acid metabolism were also presented.

Absorption↗
PubMed1993

Predicting amino acid adequacy of diets fed to Holstein steers.

The Cornell Net Carbohydrate and Protein System (CNCPS) and NRC (1985) models were evaluated for accuracy in predicting metabolizable protein (MP) and essential amino acid (EAA) allowable ADG, using chemical body and feed composition data from feeding trials with Holstein steers. Nine Holstein steers (113 to 200 kg) were slaughtered and determined to have the following whole-body essential amino acid composition of (grams/100 grams of protein): arginine, 5.94; histidine, 2.07; isoleucine, 2.28; leucine, 5.72; lysine, 5.81; methionine, 1.99; phenylalanine, 3.04; threonine, 3.52; tryptophan, .57; and valine, 3.32. The NRC and CNCPS were then tested against data from 25 feeding periods, each representing the 56-d growth of 10 Holstein steers (mean BW of 162 kg), to determine their ability to predict the gain allowed by the supply of MP and the first-limiting EAA. The NRC (1985) system accounted for 46% of the variation in MP allowable gain, with an average bias of -30%. The CNCPS accounted for 87 and 73% of the variation in MP and EAA allowable gain, with a bias of 8 and 5%, respectively. The bias was reduced to 3% (R2 of .82) when ADG was predicted by the factor (ME, MP, or EAA) first-limiting ADG.

Amino Acids, Essential↗
PubMed1992

Abomasal infusion of casein enhances nitrogen retention in somatotropin-treated steers.

The effects of bovine somatotropin (bST) administration and abomasal protein infusion on nitrogen metabolism were investigated using four abomasally-cannulated Holstein steers in a 4 x 4 Latin square design. Treatments were factorially arranged to include daily abomasal infusion (water or casein, 0.9 g/kg body wt) and daily bST injection (0 or 200 micrograms/kg body wt). Each treatment period lasted for 23 d and consisted of an adjustment period (d 1 to 7), casein infusion (d 8 to 23) and bST treatment (d 10 to 23). Nitrogen metabolism and serum insulin-like growth factor-I (IGF-I) profiles were characterized on d 16-22. Animals were fed a total mixed diet balanced to achieve 0.75 kg gain/d and supplemented to provide 115% of requirements for crude protein and minerals. Nitrogen retention was increased by casein and bST individually (21 and 33%, respectively) or in combination (75%). Somatotropin treatment increased the biological value of absorbed N, which was consistent with reductions in plasma urea nitrogen. Circulating IGF-I was increased by bST and was highly correlated (r = 0.73) with N retention. Overall, bST altered requirements so that less absorbed N was required per unit of N retained. However, results also demonstrated that because of limitations in amino acids supplied from microbial and ruminal escape protein in young growing cattle, amino acid supply may limit the magnitude of N retention response to bST under many situations.

Abomasum↗
PubMed1992

A net carbohydrate and protein system for evaluating cattle diets: I. Ruminal fermentation.

The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation. The ruminal microbial population is divided into bacteria that ferment structural carbohydrate (SC) and those that ferment nonstructural carbohydrate (NSC). Protozoa are accommodated by a decrease in the theoretical maximum growth yield (.50 vs .40 g of cells per gram of carbohydrate fermented), and the yields are adjusted for maintenance requirements (.05 vs .150 g of cell dry weight per gram of carbohydrate fermented per hour for SC and NSC bacteria, respectively). Bacterial yield is decreased when forage NDF is < 20% (2.5% for every 1% decrease in NDF). The SC bacteria utilize only ammonia as a N source, but the NSC bacteria can utilize either ammonia or peptides. The yield of NSC bacteria is enhanced by as much as 18.7% when proteins or peptides are available. The NSC bacteria produce less ammonia when the carbohydrate fermentation (growth) rate is rapid, but 34% of the ammonia production is insensitive to the rate of carbohydrate fermentation. Ammonia production rates are moderated by the rate of peptide and amino acid uptake (.07 g of peptide per gram of cells per hour), and peptides and amino acids can pass out of the rumen if the rate of proteolysis is faster than the rate of peptide utilization. The protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%. Validation with published data of microbial flow from the rumen gave a regression with a slope of .94 and an r2 of .88.

Ammonia↗
PubMed1992

A net carbohydrate and protein system for evaluating cattle diets: II. Carbohydrate and protein availability.

The Cornell Net Carbohydrate and Protein System (CNCPS) has a submodel that predicts rates of feedstuff degradation in the rumen, the passage of undegraded feed to the lower gut, and the amount of ME and protein that is available to the animal. In the CNCPS, structural carbohydrate (SC) and nonstructural carbohydrate (NSC) are estimated from sequential NDF analyses of the feed. Data from the literature are used to predict fractional rates of SC and NSC degradation. Crude protein is partitioned into five fractions. Fraction A is NPN, which is trichloroacetic (TCA) acid-soluble N. Unavailable or protein bound to cell wall (Fraction C) is derived from acid detergent insoluble nitrogen (ADIP), and slowly degraded true protein (Fraction B3) is neutral detergent insoluble nitrogen (NDIP) minus Fraction C. Rapidly degraded true protein (Fraction B1) is TCA-precipitable protein from the buffer-soluble protein minus NPN. True protein with an intermediate degradation rate (Fraction B2) is the remaining N. Protein degradation rates are estimated by an in vitro procedure that uses Streptomyces griseus protease, and a curve-peeling technique is used to identify rates for each fraction. The amount of carbohydrate or N that is digested in the rumen is determined by the relative rates of degradation and passage. Ruminal passage rates are a function of DMI, particle size, bulk density, and the type of feed that is consumed (e.g., forage vs cereal grain).

Animal Feed↗
PubMed1992

A net carbohydrate and protein system for evaluating cattle diets: III. Cattle requirements and diet adequacy.

The Cornell Net Carbohydrate and Protein System (CNCPS) has equations for predicting nutrient requirements, feed intake, and feed utilization over wide variations in cattle (frame size, body condition, and stage of growth), feed carbohydrate and protein fractions and their digestion and passage rates, and environmental conditions. Independent data were used to validate the ability of the CNCPS to predict responses compared to National Research Council (NRC) systems. With DMI in steers, the CNCPS had a 12% lower standard error of the Y estimate (Sy.x) and three percentage units less bias than the NRC system. For DMI in heifers, both systems had a similar Sy.x but the NRC had four percentage units less bias. With lactating dairy cows' DMI, the CNCPS had a 12% lower Sy.x. Observed NEm requirement averaged 5% under NRC and 6% under CNCPS predicted values at temperatures above 9 degrees C but were 18% over NRC and 9% under CNCPS at temperatures under 9 degrees C. Energy retained was predicted with an R2 of .80 and .95 and a bias of 8 and 4% for the NRC and CNCPS, respectively. Protein retained was predicted with an R2 of .75 and .85 with a bias of 0 and -1% for NRC and CNCPS, respectively. Biases due to frame size, implant, or NEg were small. Body condition scores predicted body fat percentage in dairy cows with an R2 of .93 and a Sy.x of 2.35% body fat. The CNCPS predicted metabolizable protein allowable ADG with a bias of 1.6% with a Sy.x of .07 kg compared to values of -30% and .10 kg, respectively for the NRC system.

Animal Feed↗
PubMed1992

Management systems for Holstein steers that utilize alfalfa silage and improve carcass value.

Two trials were conducted to evaluate the effect of two-phase feeding systems using alfalfa silage or pasture on the performance and carcass characteristics of Holstein steers. During the growing phase (98 d) of Trial 1, steers received alfalfa silage at either 40, 22, or 7% of the DMI. During the growing phase of Trial 2, steers received alfalfa silage at either 39 or 8% of their DMI (140 d) or grazed an orchardgrass/ryegrass pasture (175 d). During the finishing phase, all steers received a 90% concentrate diet until they reached a small degree of marbling at the 12th rib as predicted by ultrasonic attenuation. In Trial 1, one-half were initially implanted with zeranol and reimplanted with trenbolone acetate and estradiol (TBA+E) after 98 d. In Trial 2, one-half were implanted twice with TBA+E at a 120-d interval. Trial 1 average daily gains (kilograms) for the 40, 22, and 7% alfalfa silage treatments were 1.14, 1.25, and 1.38 in Period 1 (all different from each other at P less than .05); 1.31, 1.34, and 1.19 in Period 2; and 1.25, 1.25, and 1.26 overall. Trial 2 average daily gains (kilograms) for the 39, 8, and pasture treatments were 1.50, 1.71, and .92 for Period 1 (all different from each other at P less than .05); .93, .75, 1.11 for Period 2 (all different from each other at P less than .05); and 1.16, 1.17, and 1.03 overall (pasture different at P less than .05). No consistent effects of diet or implant on carcass characteristics were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

Predicting the profitability of alfalfa silage and pasture feeding systems for Holstein steers.

Data from two research trials were used as inputs to a model to project the return to capital of two-phase alfalfa silage and pasture feeding systems for Holstein steers. This approach presents a methodology for applying research data over widely varying conditions. Cattle received a 40% (High = H), 22% (Medium = M), or 8% (Low = L) alfalfa silage diet or grazed an orchardgrass/ryegrass pasture (Pasture = P) during Period 1. During Period 2, cattle consumed a 90% concentrate diet until ultrasonic attenuation predicted that the longissimus muscle contained a small degree of marbling. All systems produced similar carcass grades, so profitability differences resulted from relationships between feed requirements, cost of feed, and cost of time. Cattle grazed on pasture yielded a higher return to capital during Period 1 and over the entire feeding system. Among the other systems, L returned more to capital during Period 1, but over the entire feeding system additional silage returned more when silage cost was less than $32 per 1.02 t (as fed). Above this cost, the continuous 90% concentrate diet yielded a higher return. Cattle implanted with trenbolone acetate and estradiol returned $60 in Trial 1 and $86 in Trial 2 more per animal than did unimplanted steers.

Animal Feed↗
PubMed1992

Dynamic model prediction of the value of reduced solubility of alfalfa silage protein for lactating dairy cows.

A net carbohydrate and protein system was used to develop model diets for lactating dairy cattle with various protein solubilities in the alfalfa silage component of the diet. The objective was to determine the level to which alfalfa silage could be used to replace supplemental protein sources as the silage protein solubility decreased and to estimate the value of silage treatments needed to reduce protein solubility. Four cow groups were considered: early lactation multiparous cows, primiparous cows, midlactation cows, and late lactation cows. Diets were balanced for metabolizable protein, metabolizable energy, and ammonia and peptides for rumen bacteria; limits on DMI and effective NDF were enforced. Lower protein solubility was predicted to increase the yield of bacteria per unit of alfalfa silage DM and the yield of metabolizable protein per unit of alfalfa silage CP. Because of reduced protein supplements, diet costs were decreased. The savings per unit of silage in these rations increased as alfalfa silage protein solubility decreased. For example, with a reduction in solubility from 61 to 51% of CP, the savings ranged from $2.96 to $3.26/tonne of silage across the four cow groups. The value of acid treatment of silage needed to effect these reductions exhibited diminishing returns as application rate increased and appeared to be most cost effective when used on high quality alfalfa fed to high producing cows with application rates less than 2 kg/tonne. Management practices that reduce silage temperatures were predicted to save $.50 to $1.50/tonne of silage when the diets were balanced to account for protein degradability.

Animals↗
PubMed1991

Effect of an implant of trenbolone acetate and estradiol on growth, feed efficiency, and carcass composition of Holstein and beef steers.

The effects of an implant of 140 mg of trenbolone acetate and 28 mg of estradiol (TBA + E2) on performance and carcass composition were evaluated with 72 individually fed steers. Holstein (n = 24), Angus (n = 24), and Angus x Simmental (n = 24) steer calves were allocated by breed and implant treatment to either an individual feeding pen (n = 36) or an electronic feeding door in a group pen (three pens with 12 animals per pen). Intake and refusal of the 85% concentrate diet were recorded daily. Animals were slaughtered when ultrasonic attenuation values of the longissimus muscle at the 12th rib reached .55, which is correlated with low Choice marbling. At slaughter, complete carcass measurements were taken and the right side of each carcass was separated into boneless wholesale cuts. Implanting with TBA + E2 improved (P less than .01) daily gain and feed efficiency. Daily gain was increased 17, 26, and 21% in Holstein, Angus, and crossbred steers, respectively. The implant increased overall daily protein and fat accretion 23%. Carcass conformation and dressing percentage were not affected (P greater than .05) by TBA + E2 treatment. Implantation with TBA + E2 had little effect on yield of wholesale boneless cuts when expressed as a percentage of carcass weight but increased absolute weight as a small degree of marbling by 6 to 40 kg.

Adipose Tissue↗
PubMed1991

Comparison of steaks from Holstein and Simmental x Angus steers.

Boneless rib eye steaks from 32 Holstein and 32 Simmental x Angus steers were evaluated by 55 supermarket meat managers. Within breed, steers were divided into light or heavy initial weights. Within initial weight groups, steers were either implanted with Revalor or not implanted. Steers were slaughtered commercially when they reached a small degree of marbling, and rib eye steaks were cut from the carcass and stored at -20 degrees C until the day before evaluation. After thawing overnight in a 0 to 4 degrees C cooler, uncooked steaks were randomly assigned to positions on paper plates. Each of the 55 evaluators was then told to record whether each steak was from a Holstein or a traditional beef breed. The percentage identified correctly was 50.9 +/- .96, which was not different from being random. Steaks were later assigned to blocks of eight treatments and cooked to an internal temperature of 68 degrees C before six or seven participants evaluated steaks from each block. Sensory attributes were acceptable for all steaks. Steaks from Holstein steers generally were superior to those from Simmental x Angus steers. Steaks from steers with heavy initial weights generally were superior to steaks from steers with light initial weights. Steaks from steers implanted with Revalor were slightly less acceptable than steaks from unimplanted steers for several sensory attributes, but the difference in overall acceptability was minor and nonsignificant. All the differences were small, and may have limited commercial relevance.(ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic Agents↗
PubMed1990

Predicting growth and performance of Holstein steers.

Refinements and additions were made to the growing cattle portion of the model of Fox et al. (1988) for predicting growth of Holstein steers. Based on observations of animal weight, DM intake (DMI), ADG, feed per gain (FPG) and diet ME, the modified model was tested on a database that included 299 feeding periods with Holstein steers fed in research trials over a period of 15 yr at Cornell University, the University of Minnesota and the University of Wisconsin. The modified model accounted for 93, 56 and 68% of the variation in DM intake, daily gain and feed required per unit gain, respectively. Averaged over all 299 periods in the database, the error in predicting DM intake, daily gain and feed required per unit gain was 1%, 4% and 2%, respectively. Analysis of residuals indicated that ME level did not influence the difference between predicted and observed values for DMI, ADG and FPG. Residuals analysis indicated that BW did not influence the difference between predicted and observed values for ADG and FPG but DMI of heavier cattle was overpredicted (P less than .01). These results indicated that the 8% increase in DMI for cattle over 318 kg was not warranted for the Holstein steers in this database, which were predominantly less than 15 mo at slaughter. The results of the validation indicate that this model accurately predicted performance of Holstein steers.

Animals↗
PubMed1988

The acquired immunodeficiency syndrome: a tuberculosis threat?

In the United States there has been an increase in mycobacterial infections that is attributable to the acquired immunodeficiency syndrome (AIDS). Since 1983, when the first case of AIDS was reported in Australia, there have been 523 patients (to June 30, 1987) notified with group-IV AIDS and, of these, 361 (69%) cases have been in New South Wales. Of these 361 notifications, 59 (16%) patients have had concurrent mycobacterial infection. Seven of these patients had Mycobacterium tuberculosis infection and five of these infections occurred in 1986. This means that, in 1986, patients with group-IV AIDS had a rate of infection with Myco. tuberculosis of 3000 per 100,000 population, compared with 5.2 cases per 100,000 population for New South Wales. We sought to determine whether or not there was any unexplained increase in notifications which might be attributable to AIDS. This paper reports cases that were notified to the AIDS and tuberculosis registers, finds that atypical mycobacterial infections are underreported by at least 19.5%, and examines trends in notifications for mycobacterial disease since the onset of the AIDS epidemic. It also raises the importance of appropriate measures to protect health workers from tuberculosis.

Acquired Immunodeficiency Syndrome↗