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Biomedical subjects

H R Cross

Publications and source records attributed to H R Cross.

50 records · Page 3Linked to original sources
PubMed1991

Growth, carcass traits, and fatty acid profiles of adipose tissues from steers fed whole cottonseed.

To investigate the impact of dietary whole cottonseed (WCS) level on fatty acid composition, growth, and carcass traits, 45 Hereford steers were assigned to diets containing 0, 15, or 30% dietary WCS. The 15 and 30% WCS contributed an estimated 3.3 and 6.6% additional lipid, respectively, to the diets. After being fed for 54 d, all animals were weighed and slaughtered, and carcass measurements were obtained. There were no differences (P greater than .05) among dietary treatment groups in live weight or ADG for the 54-d feeding period. Control steers had larger (P less than .05) longissimus muscle areas than steers fed 30% WCS, which accounted for the advantage in yield grade (P less than .05) exhibited by the control group. Feeding of 30% WCS resulted in minor increases in linoleic and total polyunsaturated fatty acid content of perinephric fat expressed in both normalized (area percentage) and gravimetric (g/100 g of fresh tissue) formats. There were no significant differences in the monounsaturated or saturated fatty acid content of adipose tissues from animals fed the different diets. Subcutaneous adipose tissue samples were higher (P less than .01) in total unsaturates but had lower (P less than .05) proportions of C18:0 and C18:1 than perinephric samples. Feeding WCS at the levels reported herein only had minor effects on fatty acid composition of beef adipose tissues.

Adipose Tissue↗
PubMed1990

Using live animal ultrasound measures of ribeye area and fat thickness in yearling Hereford bulls.

Ultrasonic measurements of fat thickness (FAT) and ribeye area (REA) were analyzed together with weight (WT), scrotal circumference (SC) and age data from 385 yearling Hereford bulls representing 45 sires. Additional variables created were 100*REA/WT (REACWT) and 365-d adjusted REA (AREA). Multiplicative age adjustment for AREA was calculated from linear regression of REA on age. Heritabilities were .45 +/- .17 for REACWT, .36 +/- .16 for WT, .12 +/- .13 for REA, .11 +/- .13 for AREA, .04 +/- .13 for FAT and .18 +/- .14 for SC. Phenotypic and genetic correlations were strongly negative for WT with REACWT. Neither AREA nor REACWT alone were considered suitable muscling variables due to their association with age, WT and FAT. Ultrasound REA measurements should be adjusted for the linear effects of age and WT and quadratic effects of FAT before being used for selection. Measurement of SC indicated a strong association with WT (r = .55) and a moderate positive genetic correlation with REA (.49 +/- .58).

Adipose Tissue↗
PubMed1990

Effect of postmortem treatments on the tenderness of meat from Hereford, Brahman and Brahman-cross beef cattle.

The effect of postmortem aging (7, 14, 21 or 28 d), high-voltage electrical stimulation (stimulated or not stimulated) and blade tenderization (none or once; crossbreds only) on the sensory and cooking properties of meat from four beef breeds or breed-types (purebred Hereford, purebred Brahman, Hereford x Brahman and Brahman x Hereford) was determined. The meat from purebred Brahman cattle that was not electrically stimulated was less tender and more variable in tenderness than that from other breed-types but electrical stimulation reduced these differences in tenderness. The Brahman crossbred steers produced meat that was not different in tenderness or variability in tenderness from that of purebred Hereford steers, although all were only judged "slightly tender." Electrical stimulation reduced the length of postmortem aging needed to reach a given level of tenderness regardless of breed or breed-type. Meat from crossbred animals that was blade-tendernized was not different in tenderness from meat that was electrically stimulated. The results of this investigation indicate that purebred Brahman muscle was inherently less tender, but postmortem tenderization procedures produced meat that was similar tenderness to that of the other breed-types used in this study.

Animals↗
PubMed1990

Yields of by-products from different cattle types.

Slaughter cattle (n = 360), selected and allocated to types according to their phenotypic breed type characteristics, were slaughtered in lots of 15 head at a large commercial packing plant. By-product weights were obtained for these lots of 15 head after plant personnel had separated the by-products according to plant procedures. Percentage of slaughter weight in each by-product was calculated. The trait most influenced by cattle type was the hide; Bos indicus cattle generally had the greatest percentage of their live weights as hide (green, trimmed, fleshed or cured), and Holstein cattle generally had the lowest. For edible by-products, the liver differed significantly among cattle types, with Holstein cattle having the higher percentage of their live weight as liver. Other items studied were not significantly or economically different among cattle types.

Animals↗
PubMed1990

Mechanisms associated with the variation in tenderness of meat from Brahman and Hereford cattle.

To study possible mechanisms for differences in meat tenderness, 10 purebred Hereford and 10 American Grey Brahman steers were fed a typical feedlot diet and slaughtered when ultrasound measurements indicated that they had approximately 1 cm of fat thickness at the 12th rib. Longissimus muscle from Brahman cattle was less (P less than .05) tender after 7, 14, 21, 28 and 35 d postmortem than muscle from Hereford cattle, but muscle from Hereford cattle showed greater improvement in tenderness from 7 to 14 d postmortem than muscle from Brahman cattle (interaction P less than .05). Cathepsin B or cathepsin B+L activities and the myofibrillar response to elevated ionic strength were not different between breeds, but both could be related to the postmortem increase in tenderness of both breeds. Calcium-dependent protease activity, as modulated by calcium-dependent protease inhibitor, seems to play a major role in the inherent tenderness differences between breeds.

Adipose Tissue↗
PubMed1990

The influence of sex-class, USDA yield grade and USDA quality grade on seam fat trim from the primals of beef carcasses.

Beef carcasses (129 steers and 80 heifers) differing in weight, muscling, fatness and marbling score were selected to represent the full spectrum of USDA yield grades; one side was fabricated into boneless primal cuts. Primals were trimmed of all external fat and intermuscular (seam) fat and all components were weighed. Regression equations were developed to predict the percentage of seam fat on an external fat-free primal basis using USDA yield grade (YG), marbling score and a squared function of YG as the independent variables. YG (.77) and marbling score (.67) were highly correlated to seam fat. Heifers tended to have a higher predicted percentage of seam fat than did steers across all YG. Primals from USDA Choice carcasses had approximately 1.0 percentage point more predicted seam fat than did USDA Select primals at the same YG and sex-class. The YG 2.5 heifers had similar proportions of predicted seam fat from primals as YG 3.5 steers, but YG 3.5 heifers tended to have more seam fat than YG 4.5 steers. The same trend was noted between YG 4.5 heifers and YG 5.5 steers, indicating a sex-related deposition of seam fat in fed cattle.

Adipose Tissue↗
PubMed1990

Lean beef: impetus for lipid modifications.

Health-conscious consumers want lean beef. The beef industry has responded by physically removing much of the adipose tissue from retail products and by initiating attempts to produce--genetically and environmentally--cattle with more muscle, less external fat, and less seam fat, without sacrificing the quality dependent on the amount of marbling present. Offering lean beef that is closely or completely trimmed of external fat has improved retail beef sales. Impetus for modification of the lipid composition of bovine muscle and adipose tissue, including marbling, has resulted from the following: (a) diet/health concerns of consumers and demands for leaner beef, (b) research clarifying effects of dietary fatty acids and cholesterol on serum cholesterol levels, (c) dietary guidelines and recommendations from health organizations, and (d) dietary recommendations by physicians and dietitians to reduce beef consumption. Analysis of cholesterol content of marbling dissected from the rib (longissimus dorsi) muscle revealed that marbling contributes little to total cholesterol content. Cholesterol content of marbling was 117 mg/100 gm intramuscular adipose tissue (equivalent to about a 2 mg cholesterol contribution to a 100-gm serving of uncooked meat). The difference in fatty acid composition of lean meat and of adipose tissue is primarily in the percentage of polyunsaturated fatty acids, which is higher in lean meat. The most prevalent fatty acids in adipose tissue including marbling were: palmitic acid (24.1%), stearic acid (13.5%), and oleic acid (37.7%).

Adipose Tissue↗
PubMed1989

Acute and long-term lipogenic response to insulin and clenbuterol in bovine intramuscular and subcutaneous adipose tissues.

The present study was conducted to determine whether insulin and clenbuterol affected either short-term (2-h) incubations or long-term (48-h) tissue cultures of i.m. and s.c. adipose tissue explants. Samples were taken from control steers and steers fed 7 mg.head-1.d-1 clenbuterol for 50 d, after which time the drug was withdrawn from the diet for 90 d prior to slaughter. Neither short-term incubations nor long-term explant cultures contained bovine serum albumin (BSA). Insulin (6.67 x 10(-9) M) had no effect (P greater than .05) on lipogenesis in s.c. and i.m. adipose tissue in 2-h tissue incubations of fresh adipose tissue. There was a substantial decrease in activity during the culture period, which was ameliorated somewhat in s.c. adipose tissue by the presence of insulin in the culture media. Clenbuterol exposure for 48 h in vitro decreased the production of lipids from acetate in both adipose tissue depots but had no effect in short-term adipose tissue incubations. Results from the present study confirm that omitting BSA from incubation media does not enhance the responsiveness of bovine s.c. adipose tissue or the less mature i.m. adipose tissue to insulin. Insulin may maintain greater cell viability in 48-h explant cultures.

Adipose Tissue↗
PubMed1989

Using ultrasound technology to predict pork carcass composition.

Twenty market hogs were evaluated with real-time ultrasound both before and after slaughter. Fat measures (n = 9) were taken at various body locations along with the longissimus muscle area measurement at the 10th rib. After live ultrasound, the hogs were slaughtered and the unsplit carcasses were measured with ultrasound at the same live ultrasound locations. After chilling, carcass measures were taken at the same locations using a backfat probe for fat measures and a loin eye dot grid for measuring the longissimus muscle area. One side of each carcass was fabricated into the four lean cuts, which then were expressed as a percentage of the side weight. The most appropriate prediction equation found was a two-variable equation (fat thickness at the anterior tip of gluteus medius and longissimus muscle area) with a R2 of .83 and a RSD value of 1.67. This prediction equation was verified on a different sample of 20 market hogs; actual vs predicted four lean cuts revealed that the prediction equation had a R2 of .63 and a RSD value of 2.04. Although some accuracy and precision was lost when this live animal prediction equation was incorporated in market hog evaluation, this equation offers producers an objective mechanism for identifying carcass merit in live hogs.

Adipose Tissue↗
PubMed1988

Visual and chemical tissue markers for bovine carcass components.

A two-component, nontoxic, quantifiable animal/carcass tracing system was developed using riboflavin as an on-premises, initial carcass identifier visible under longwave ultraviolet (UV) light and deuterium oxide (D2O) as a tracer analytically quantified via fixed wavelength infrared spectrophotometry. Twenty-four cull cows and heifers were allocated into eight antemortem treatment groups (1, 12, 24, 48, 72, 96, 120, 144 h) for evaluation of the efficacy of riboflavin and D2O as tissue tracers in postmortem meat tissues. All cattle were slaughtered using conventional procedures and inspection. To study postmortem riboflavin marker changes due to constant light exposure over time, fluorescence and emission intensity scores were obtained by a trained panel 24, 48, and 168 h postslaughter. The riboflavin marker intensity rating means for UV fluorescence were classified as identifiable on all carcasses when evaluated under UV light, but were classified as not identifiable when evaluated under ambient light. Deuterium oxide levels in all tissue water samples, regardless of antemortem infusion group, contained D2O concentrations at least 2.5 times greater than those found in background water. Deuterium oxide was shown to disperse rapidly throughout living tissues. Correlations within animals for D2O levels from blood and muscle were all highly significant (r = .99).

Animals↗
PubMed1987

Growth and carcass traits of heifers as affected by hormonal treatment.

Seventy-seven heifers weighing about 200 kg were assigned randomly to intact control (C), ovariectomized (OVX) immunized against estradiol (BSA-E), BSA-E + trenbolone acetate (BSA-E + TBA), TBA or ovx + TBA groups. The objective of the study was to determine the effects of ovariectomy, immunoneutralization of estradiol and trenbolone acetate treatment on growth rate and carcass merit. Heifers were fed a corn-corn silage diet and were slaughtered when treatment groups attained live-animal weights of 433 kg. Observations of rate of growth, efficiency of feed conversion, characteristics of carcasses and characteristics of organoleptic properties of the cooked meat were made. Average daily gains (ADG) were similar in the control and OVX groups and tended to be less than in other treatment groups (P less than .36). Although not statistically significant, the observed mean for the BSA-E + TBA treatment suggests improved ADG and TDN per unit of gain, indicating a possible immunization X TBA interaction. Data also suggested that heifers implanted with TBA had increased ADG and efficiencies of gain. Possibly, immunoneutralization of endogenous estradiol can improve ADG as compared with control and OVX groups. Treatments had no effect on color or texture of lean muscle at the 12th rib interface. The OVX + TBA group had less (P less than .01) 12th rib fat cover than other groups and lower percent fat in the rib than C. The BSA-E + TBA and TBA groups also possessed larger (P less than .02) longissimus muscle areas than the control group. Observations of juiciness, tenderness and flavor were similar among all treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Effect of diethylstilbestrol on tissue gain and carcass merit of feedlot beef steers.

The effect of diethylstilbestrol (DES) on the composition of tissue gain of Hereford steers was studied in a complete slaughter balance trial. Eight steers were slaughtered initially (IS) and, after 177 days on feed, eight control steers (C) and seven steers that had been fed 20 mg DES daily (DES) were slaughtered. Initial full body weight averaged 224.8 kg, and final full body weight averaged 403.0 kg for the C steers and 433.6 kg for the DES steers. Final empty body weight averaged 346.6 kg for the C steers and 368.0 kg for the DES steers. DES improved live weight gain by 17% and conversion of feed dry matter to live weight by 12%. Recovery of wet weight during slaughter averaged 99.6%. DES steers had larger rib cut weights and greater proportions of separable lean and bone plus connective tissue in the rib cuts than C steers, an ribeye area tended to be larger in DES steers. DES caused a small shift in relative body composition toward more protein, moisture and ash. Tissue gain in DES steers consisted of 28.3% more protein, 26.0% more moisture, 73.2% more ash, 1.5% less fat and 109.1% more residual (dry matter not accounted for by N x 6.25, ether extract and ash) than did tissue gain in C steers. Energy gain per unit of energy intake over the feeding period was not affected by DES treatment, but DES improved protein gain per unit of protein intake and per unit of energy intake by approximately 20% within the total empty body and by about 25% within the carcass fraction. Results confirm indirect estimates in the literature indicating that DES increases skeletal growth and lean tissue deposition in feedlot steers.

Animal Feed↗
PubMedDate not supplied

Overexpression of the cardiac Na+/Ca2+ exchanger increases susceptibility to ischemia/reperfusion injury in male, but not female, transgenic mice.

Influx of Ca2+ into myocytes via Na+/Ca2+ exchange may be stimulated by the high levels of intracellular Na+ and the changes in membrane potential known to occur during ischemia/reperfusion. This increased influx could, in turn, lead to Ca2+ overload and injury. Overexpression of the cardiac Na+/Ca2+ exchanger therefore may increase susceptibility to ischemia/reperfusion injury. To test this hypothesis, the hearts of male and female transgenic mice, overexpressing the Na+/Ca2+ exchange protein, and hearts of their wild-type littermates, were perfused with Krebs-Henseleit buffer and subjected to 20 minutes of ischemia and 40 minutes of reperfusion. Preischemic left ventricular developed pressures and +dP/dtmax, as well as -dP/dtmin, were higher in the male transgenic hearts compared with wild-type, implying a role for Na+/Ca2+ exchange in the contraction, as well as the relaxation, phases of the cardiac beat. Postischemic function was lower in male transgenic than in male wild-type hearts (7+/-2% versus 32+/-6% of preischemic function), but there was no difference between female transgenic and female wild-type hearts, both at approximately 30% of preischemic function. To assess whether this male/female difference was due to female-specific hormones such as estrogen, the hearts of bilaterally ovariectomized and sham-operated transgenic females were subjected to the same protocol. The functional recoveries of ovariectomized female transgenic hearts were lower (17+/-3% of preischemic function) than those of wild-type and sham-operated transgenic females. The lower postischemic functional recovery in the male transgenic and female ovariectomized transgenic hearts correlated with lower recoveries of the energy metabolites, ATP and phosphocreatine, as measured by 31P nuclear magnetic resonance spectroscopy. Alternans were observed during reperfusion in male transgenic and female ovariectomized transgenic hearts only, consistent with intracellular Ca2+ overload. Western analyses showed that alterations in the expression of the Na+/Ca2+ exchange or L-type Ca2+ channel proteins were not responsible for the protection observed in the female transgenic hearts. In conclusion, in males, overexpression of the Na+/Ca2+ exchanger reduced postischemic recovery of both contractile function and energy metabolites, indicating that the Na+/Ca2+ exchanger may play a role in ischemia/reperfusion injury. From the studies of females, however, it appears that this exacerbation of ischemia/reperfusion injury by overexpression of the Na+/Ca2+ exchanger can be overcome partially by female-specific hormones such as estrogen.

Adenosine Triphosphate↗