I B Mandell

University of Guelph, Guelph, Ontario, Canada

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Publications (41)58.55 Total impact

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    ABSTRACT: A transgenic line of Yorkshire pigs named the Cassie ( CA: ) line was produced with a low copy number phytase transgene inserted in the genome. The transgenic line efficiently digests P, Ca and other major minerals of plant dietary origin. The objectives of this study were to i) compare carcass and tissue nutrient composition and meat quality traits for third generation hemizygous CA line market BW finisher pigs (n = 24) with age-matched conventional Yorkshire ( YK: ) finisher pigs (n = 24); and ii) examine effects of out-breeding with high index conventional YK boars on modifying carcass leanness from the third to sixth generations in CA line finisher boars (n = 73) and gilts (n = 103). CA boars (n = 12) and CA gilts (n = 12) were fed diets without supplemental P and comparable numbers of age-matched YK boars and gilts fed diets containing supplement P were raised throughout the finisher phase. The pigs were slaughtered and then fabricated into commercial pork primals prior to meat composition and quality evaluation. Proximate and major micro-nutrient composition was determined on tissues including fat, kidney, lean, liver, and skin. The main difference observed was greater (P = 0.033) crude fat content in CA boar carcasses and increased (P < 0.04) leaf lard in both CA boars and gilts, but no differences (P = 0.895 and 0.223, respectively) in carcass backfat thickness, as compared with YK pigs. There were no substantive differences in tissue composition, except for CA boar kidneys. Numerous changes in the mineral, fatty acid and indispensible AA composition for CA boar kidneys were not apparent in CA gilts. These changes may point to adaptive physiological changes in the boar kidney necessary for homeostatic regulation of mineral retention related to phytase action rather than to insertion of the transgene. However, from a meat composition perspective, transgenic expression of phytase in the CA line of Yorkshire pigs had little overall effect on meat composition. Out-breeding of high-index CA gilts with high-index commercial YK boars linearly reduced (P = 0.002) back fat thickness with a corresponding linear increase (P = 0.001) in lean yield in finisher CA gilts although no change in these parameters were observed in CA finisher boars. The increase in lean yield in CA gilts by selective breeding without affecting the level of salivary phytase activity documents the value of conventional genetic selection in conjunction with genetic modification.
    Journal of animal science. 08/2014;
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    ABSTRACT: This study was conducted to: (1) identify new SNPs for residual feed intake (RFI) and performance traits within candidate genes identified in a genome wide association study (GWAS); (2) estimate the proportion of variation in RFI explained by the detected SNPs; (3) estimate the effects of detected SNPs on carcass traits to avoid undesirable correlated effects on these economically important traits when selecting for feed efficiency; and (4) map the genes to biological mechanisms and pathways. A total number of 339 SNPs corresponding to 180 genes were tested for association with phenotypes using a single locus regression (SLRM) and genotypic model on 726 and 990 crossbred animals for feed efficiency and carcass traits, respectively. Strong evidence of associations for RFI were located on chromosomes 8, 15, 16, 18, 19, 21, and 28. The strongest association with RFI (P = 0.0017) was found with a newly discovered SNP located on BTA 8 within the ELP3 gene. SNPs rs41820824 and rs41821600 on BTA 16 within the gene HMCN1 were strongly associated with RFI (P = 0.0064 and P = 0.0033, respectively). A SNP located on BTA 18 within the ZNF423 gene provided strong evidence for association with RFI (P = 0.0028). Genomic estimated breeding values (GEBV) from 98 significant SNPs were moderately correlated (0.47) to the estimated breeding values (EBVs) from a mixed animal model. The significant (P < 0.05) SNPs (98) explained 26% of the genetic variance for RFI. In silico functional analysis for the genes suggested 35 and 39 biological processes and pathways, respectively for feed efficiency traits. This study identified several positional and functional candidate genes involved in important biological mechanisms associated with feed efficiency and performance. Significant SNPs should be validated in other populations to establish their potential utilization in genetic improvement programs.
    BMC Genetics 01/2014; 15(1):14. · 2.81 Impact Factor
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    ABSTRACT: Genetic improvement of beef quality will benefit both producers and consumers, and can be achieved by selecting animals that carry desired quantitative trait nucleotides (QTN), which result from intensive searches using genetic markers. This paper presents a genome-wide association approach utilizing single nucleotide polymorphisms (SNP) in the Illumina BovineSNP50 BeadChip to seek genomic regions that potentially harbor genes or QTN underlying variation in carcass quality of beef cattle.This study used 747 genotyped animals, mainly crossbred, with phenotypes on twelve carcass quality traits, including hot carcass weight (HCW), back fat thickness (BF), Longissimus dorsi muscle area or ribeye area (REA), marbling scores (MRB), lean yield grade by Beef Improvement Federation formulae (BIFYLD), steak tenderness by Warner-Bratzler shear force 7-day post-mortem (LM7D) as well as body composition as determined by partial rib (IMPS 103) dissection presented as a percentage of total rib weight including body cavity fat (BDFR), lean (LNR), bone (BNR), intermuscular fat (INFR), subcutaneous fat (SQFR), and total fat (TLFR). At the genome wide level false discovery rate (FDR < 10%), eight SNP were found significantly associated with HCW. Seven of these SNP were located on Bos taurus autosome (BTA) 6. At a less stringent significance level (P < 0.001), 520 SNP were found significantly associated with mostly individual traits (473 SNP), and multiple traits (47 SNP). Of these significant SNP, 48 were located on BTA6, and 22 of them were in association with hot carcass weight. There were 53 SNP associated with percentage of rib bone, and 12 of them were on BTA20. The rest of the significant SNP were scattered over other chromosomes. They accounted for 1.90 - 5.89% of the phenotypic variance of the traits. A region of approximately 4Mbp long on BTA6 was found to be a potential area to harbor candidate genes influencing growth. One marker on BTA25 accounting for 2.67% of the variation in LM7D may be worth further investigation for the improvement of beef tenderness. This study provides useful information to further assist the identification of chromosome regions and subsequently genes affecting carcass quality traits in beef cattle. It also revealed many SNP that acted pleiotropically to affect carcass quality. This knowledge is important in selecting subsets of SNP to improve the performance of beef cattle.
    BMC Genetics 09/2013; 14(1):80. · 2.81 Impact Factor
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    ABSTRACT: http://www.biomedcentral.com/1471-2156/14/80/abstract
    BMC Genetics 09/2013; 14:80. · 2.81 Impact Factor
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    ABSTRACT: The effects of chilling method and moisture enhancement were examined for improving eating quality of semimembranosus (SM) and longissimus lumborum (LL) from 62 cull beef cows. Chilling method included hot boning muscles after 45 to 60min postmortem or conventional chilling for 24h. Moisture enhancement included 1) a non-injected control (CONT) or injection processing (10% of product weight) using 2) Sodium Tripolyphosphate/salt (Na/STP), 3) Sodium Citrate (NaCIT), 4) Calcium Ascorbate (CaASC), or 5) Citrus Juices (CITRUS). Chilling method by moisture enhancement treatment interactions (P<0.09) were due to decreased hue, chroma and sarcomere length values in hot boned vs. conventionally chilled product (SM and LL) for CaASC vs. other moisture enhancement treatments. Chilling method by moisture enhancement treatment interactions (P<0.05) were due to decreased shear force and increased tenderness in conventionally chilled vs. hot boned LL using CaASC vs. Na/STP. Moisture enhancement can improve tenderness of cull cow beef depending on combinations of chilling method and moisture enhancement treatments used.
    Meat Science 07/2013; 96(1):237-246. · 2.75 Impact Factor
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    ABSTRACT: The heritability of shear force at 7, 14 and 21 d was estimated from a crossbred population of beef cattle. The population consisted of approximately 1400 crossbred cattle that were predominantly the offspring of Angus, Simmental, Gelbvieh and Piedmontese sires bred to predominantly Angus and Simmental females. Significant breed effects on tenderness were found within each aging time and no effect of heterosis was detected. The heritability of shear force declined from 0.194 to 0.048 as aging time increased from 7 to 21 d, highlighting the effectiveness of aging as a tool to improve tenderness. The repeatability of shear force was also found to be moderate (0.53). However, as energy prices increase it may be attractive to reduce aging times, thus breeding animals that are more tender at shorter aging times would be beneficial. The heritability of tenderness found at shorter aging times would indicate that improvement in this trait would be possible within a population where phenotypes are available.
    Canadian Journal of Animal Science 01/2013; 93(3):307-312. · 0.96 Impact Factor
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    ABSTRACT: One hundred and two cross-bred steer calves (BW=368±6.6 kg)were used in a 2×3 factorial arrangement of treatments plus a control to determine the effect of inclusion level and form of corn distillers grains plus solubles (DGS) on finishing performance, carcass characteristics, and feeding behavior using whole corn grain-based finishing diets. The DGS were fed at 0 (control), 167, 333, and 500 g/kg of diet DM using dry (DDGS) or modified wet (MWDGS) DGS. All diets contained 100 g/kg haylage as a forage source, and were formulated to contain at least 137 g/kg CP. Individual intake and feeding behavior was measured using the Insentec system. Cattle were fed until ultrasound backfat thickness reached 10 mm. Data were analyzed using GLM of SAS; treatment means were compared using contrast statements (control vs. others, DDGS vs. MWDGS, inclusion level of DGS (linear, quadratic), and interactions between form and linear and quadratic inclusion level). There were no effects (P>0.05) of dietary treatment on final BW, ADG, days on feed, dressing yield (g hot carcass weight/kg final BW), hot carcass weight, marbling score, lean yield, and lean color. Rumen pH at slaughter linearly increased (P=0.001) and liver abscess score linearly decreased (P=0.03) with increasing DGS inclusion. There were significant quadratic form × level interactions (P≤0.03) for time at feeder, time per visit, number of meals, meal size, and eating rate. Number of meals (meals/d) linearly increased (P=0.006) with increasing DGS inclusion and was greater (P=0.006) in cattle fed MWDGS than those fed DDGS. Meal size linearly decreased (P=0.002) with increasing DGS inclusion and was greater (P=0.002) in cattle fed DDGS than those fed MWDGS. Finishing performance and carcass traits were generally not affected by feeding DDGS or MWDGS up to 500 g/kg diet DM in whole corn grain-based finishing diets. However, liver abscess scores were reduced with DGS inclusion and feeding behavior was influenced by form and level of DGS.
    Livestock Science. 01/2013;
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    ABSTRACT: Four cross-bred steers (average BW = 478 ± 33 kg) were used in a 4 × 4 Latin Square design to determine the effects of dietary inclusion level of dry corn distillers grains plus solubles (DDGS) on total tract digestion, nutrient balance, and nutrient excretion. The DDGS were fed at 0 (control), 16.7, 33.3, and 50% of diet DM. All diets contained 10% haylage as a forage source (DM basis), and were formulated to meet or exceed the estimated requirements for CP. Steers were fed experimental diets for ad libitum intake for a 14-d adaptation period followed by 5 d of fecal and urine collection. Data were analyzed using the GLM procedure of SAS; treatment means were compared using contrast statements (linear and quadratic effects of DDGS inclusion level). Increasing inclusion level of DDGS in diets from 0% to 50% of diet DM linearly decreased (P < 0.05) total tract DM and starch digestibility (from 77.8 to 72.9% and 89.2 to 81.5%, respectively). Daily N and P intakes linearly increased (P = 0.06 and P = 0.01, respectively) with increasing DDGS inclusion level. Fecal and urinary N, P, S, Mg, and K excretion linearly increased (P < 0.05) with increasing DDGS inclusion level. However, Se and Na excretion did not differ (P > 0.05) among treatments. Retention (g/d; intake - urinary and fecal excretion) of N did not differ (P > 0.05) among treatments. Retention of P tended (P = 0.07) to linearly increase and retention of S (g/d) linearly increased (P = 0.004) with increasing DDGS inclusion level. There were no effects (P > 0.05) of dietary treatment on digestion and retention of Se, Mg, K, and Na. Plasma P and S concentrations increased (P = 0.03 and 0.01, respectively) with increasing DDGS inclusion level. These data indicate that feeding DDGS up to 50% diet DM in whole corn grain-based finishing diets does not have a negative effect on nutrient retention but decreases digestibility. Total excretion of N, P, Ca, Mg, S, and K increased as DDGS inclusion level increased.
    Journal of Animal Science 09/2012; · 2.09 Impact Factor
  • P J Streiter, C P Campbell, I B Mandell
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    ABSTRACT: Sixty-two cull beef cows were slaughtered to investigate effects of skeletal separation and moisture enhancement on beef eating quality. Muscles from each carcass side were randomly assigned to 1) no postmortem processing (NPP), 2) prerigor skeletal separation (SS), 3) moisture enhancement (ME) using calcium ascorbate or 4) a combination of SS and ME (SS/ME). Postmortem processing treatment (PPT) by ageing (PM) interactions (P<0.01) for shear force were present for longissimus. As PM ageing increased from 7 to 21 d, there was a greater decrease (P<0.05) in shear force with NPP vs. all other PPT. Trained taste panellists found SS, ME and SS/ME improved (P<0.05) palatability attributes vs. NPP. An additive effect of combining SS and ME improved palatability traits versus SS or ME alone. Panellists found no differences (P>0.14) in softness and tenderness between SS/ME and Canadian AA or AAA beef. Postmortem processing of beef cows may produce beef as tender and juicy as beef from younger carcasses.
    Meat Science 05/2012; 92(4):400-8. · 2.75 Impact Factor
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    ABSTRACT: Vitamins influence collagen metabolism in animals grown for meat. This study investigated whether vitamins E and C regulate collagen turnover in muscle by the balance of effects on the synthesis of collagen and its degradation by secretion of matrix metalloproteinases (MMPs) by bovine intramuscular fibroblasts. Fibroblasts isolated from longissimus dorsi (LD) and semitendinosus (ST) muscle were treated with different concentrations of vitamins. Pro-MMP-2, MMP-2, and total soluble collagen (TSC) synthesis were determined. Vitamins E and C each preferentially increased (P < 0.05) MMP-2 in cells derived from LD relative to those derived from ST. Higher TSC values (P < 0.05) were found for ST cells than for LD cells. Both vitamins may increase collagen turnover exerted by intramuscular connective tissue fibroblasts. These results may have implications in vivo on animal production, as a high rate of collagen turnover may lead to increased collagen solubility in muscles, which can affect meat tenderness.
    Journal of Agricultural and Food Chemistry 01/2011; 59(2):608-14. · 2.91 Impact Factor
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    ABSTRACT: Sixty cross-bred steers (Angus ×; n=36 and Charolais ×; n=24) were used in a split-plot design to investigate the effects of feeding corn (Zea mays) or sorghum (Sorghum bicolor) dried distillers grains plus solubles in growing and finishing diets on growth performance and carcass traits. Steers were randomly assigned to one of three dietary treatments used in both feeding periods: a control diet containing soybean meal (n=20; CON), a diet containing 200g/kg (DM basis) corn dried distillers grains+solubles (n=20; CDDGS) and a diet containing 200g/kg (DM basis) sorghum dried distillers grains+solubles (n=20; SDDGS). Steers were fed a corn silage (CS) based grower diet (∼750/kg CS) for 56d and then switched to a high grain finisher diet (150g/kg CS). Feed intakes were measured using Insentec (n=48) and Calan gate (n=12) feeding systems. Animals were weighed every 28d and slaughtered at an estimated backfat of 10mm as estimated by ultrasound. Total trial average daily gain (ADG) was 1.56kg/d±0.04 for CON, 1.54kg/d±0.04 for CDDGS, and 1.51kg/d±0.04 for SDDGS and did not differ (P>0.68) between treatments. Dietary treatment did not affect (P>0.14) dry matter intake (DMI) in the growing phase, although ADG was lower for SDDGS vs. CON (P=0.008) and CDDGS (P=0.02). There was a lower gain:feed in the growing phase for SDDGS vs. CDDGS (P=0.04). In the finishing phase, inclusion of corn or sorghum DDGS did not affect (P>0.41) ADG, DMI or G:F. However, fewer days on feed were required for SDDGS to reach the target backfat for slaughter than CDDGS (P=0.03) and CON (P=0.05). These results indicate that sorghum dried distillers grains plus solubles can be included at 200g/kg inclusion level, similar to corn distillers grains plus solubles, in grower and finisher diets, without negatively influencing overall growth or carcass traits, although feeding SDDGS may result in reduced performance when corn silage based diets are fed and results in earlier fattening at a lighter body weight.
    Fuel and Energy Abstracts 01/2011; 165(1):23-30.
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    ABSTRACT: Different muscles in a beef carcass are known to respond differently to the same stimulus or animal growth pattern or both. This may complicate the search by the meat industry for production methods to render meat tender. One of the major differences between muscles in the same carcass is in the expression of intramuscular connective tissue. Current study investigates the existence of a phenotypic difference among fibroblasts from 3 bovine skeletal muscles as exemplified by the expression of matrix metalloproteinases (MMP) the main enzymes responsible for connective tissue turnover. The sensitivity of phenotypic differences to cell culture conditions (passage number, presence of growth factors from fetal serum) was also examined. Fibroblasts, the main cells responsible for the production and turnover of collagen were isolated from LM, semitendinosus (STN), and sternomandibularis (SMD) muscles from a bull calf and grown in DMEM, 10% fetal bovine serum, and 5% CO(2). Cell doubling times, survival time, resting expression, and activity of MMP and the effect of serum withdrawal in the culture media on MMP expression and activity were determined for each cell line during 15 passages. Fibroblasts isolated from the 3 muscles had different growth potentials. The shortest (P < 0.0001) cell doubling times for almost every passage were found in cells from STN muscle. Cells from the LM had a shorter (P < 0.0001) survival time in comparison with STN and SMD. Cells derived from the STN had greater values (P > 0.05) of MMP-2 activity in comparison with LM and SMD cells until passage 4. At passage 15, no activity was detected for any cell line. Serum withdrawal generally reduced MMP-2 activation but did not eliminate differences in activity between fibroblasts from the 3 muscles. These results suggest that fibroblasts from different locations are phenotypically different and may respond differently to the same growth or nutritional stimulus in vitro. This may be related to in vivo differences in accumulation, maturity, and turnover of collagen, and ultimately meat tenderness. These findings may be important for selecting a management strategy for improving meat tenderness by manipulation of animal growth; a strategy applied to the whole animal may work for some muscles but not for others.
    Journal of Animal Science 12/2010; 88(12):4006-15. · 2.09 Impact Factor
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    ABSTRACT: Manipulation of growth rate and/or diet has been shown to affect protein turnover and may be used to improve beef quality. This trial was conducted to evaluate the effects of average daily gain (ADG) and diet on animal performance, collagen characteristics and beef quality of two different muscles; longissimus dorsi (LD) and semitendinosus (ST). Seventy six Hereford and Angus steers were assigned to three dietary management regimens for finishing: high grain diet based on corn (n=28), alfalfa pasture (n=22) and grass pasture (n=26). Average daily gains were greater (P<0.001) in Herefords vs. Angus and for corn- vs. pasture finished cattle. Overall, total collagen content was greater (P<0.001) and the percentage of total collagen that was heat soluble was lower (P<0.0001) for ST than for LD muscle. The lowest (P<0.05) values for both total and heat soluble collagens were found in animals finished on corn. WBSF values for LD were greater (P<0.01) in grass-fed vs. alfalfa- and grain-finished cattle while there was no difference in WBSF values for ST between grass- and corn-fed animals. No correlation between ADG and WBSF was observed for any muscle. ADG was not correlated with collagen solubility in ST, but was correlated (P<0.05) with collagen solubility in LD. A key finding is that growth rate affected heat soluble collagen in the two muscles to a different extent. In conclusion, this study shows that different feeding strategies may not influence the tenderness of all muscles in a similar way.
    Meat Science 10/2010; 86(2):491-7. · 2.75 Impact Factor
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    ABSTRACT: Thirty-two grain-fed veal calves (177±6.7kg body weight (BW)) were used in a completely randomized block design experiment to determine effects of feeding corn diets naturally contaminated with Fusarium mycotoxins and/or a modified yeast cell wall extract (YCW) on performance, immunity and carcass characteristics. Calves were fed one of four dietary treatments in individual pens for at least 84 days either: (1) control corn+supplemental pellet (CC), (2) control corn+YCW supplemental pellet (CY), (3) mycotoxin contaminated corn+supplemental pellet (MC), and (4) mycotoxin contaminated corn+YCW supplemental pellet (MY). Diets consisted of 750g/kg whole corn grain and 250g/kg supplemental pellet with corn as the source of food-borne mycotoxins. The major contaminants present in the contaminated diets (average concentrations of MC and MY) were deoxynivalenol (DON; 10.27mg/kg), 15-acetyl DON (1.27mg/kg) and zearalenone (1.84mg/kg). Final BW and total BW gain of the calves were not different between treatment groups. However, ADG tended (P=0.07) to be higher and F:G was decreased (P=0.003) in calves fed contaminated diets. Haptoglobin, fibrinogen and IgA concentrations did not differ between treatments. Concentrations of IgG were lower (P=0.003) in calves receiving YCW. Plasma urea N and glucose concentrations were increased (P
    Animal Feed Science and Technology - ANIM FEED SCI TECH. 01/2010; 159(1):27-34.
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    Canadian Journal of Animal Science - CAN J ANIM SCI. 01/2010; 90(1):69-76.
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    ABSTRACT: If variation in behaviour is consistent within individuals and reliably associated with relevant welfare measures, this variation could aid in genetic selection, or development of management schemes designed to improve welfare. In this study, we focused on temperament tests in group-housed finishing pigs, with the objective of validating measures that are readily applicable in commercial settings and potentially related to individual differences in stress response. A total of 118 pigs in two replicate studies were housed in pens of 7–8 pigs per pen. At 24 weeks of age, animals were subjected to three tests of fear in the home pen: the human approach test (HAT), novel object test (NOT) and open door test (ODT). In each test, pigs were scored on their latency to contact the human or object, or to leave the home pen. Tests were repeated on three occasions at intervals of 3–4 days. On each test day the HAT was performed twice to compare results between different handlers. Behaviour in tests of fear was compared with two social tests in a subset of 58 pigs. Lesion scoring was performed after mixing as a measure of aggression, and a feed competition test was used to assess social status. Repeatability within-test was evaluated in a mixed model with pig as a random effect, and agreement between days, handlers and tests was evaluated by partial correlations after controlling for replicate, pen and day effects. Latency to perform all three fear tests decreased significantly over time. Correlations within-test showed significant agreement between all days for HAT and ODT, and between HAT handlers. Between tests, the HAT and ODT were correlated, and ODT and NOT tended to correlate. Comparisons between group fear tests and social tests showed that pigs which readily approach a human tended to have higher lesion scores and fewer feeding bouts in the feed competition trial. While test latencies decrease with repetition, the HAT and ODT show individual consistency over time, which suggests that these tests describe behavioural tendencies and may be useful for predicting fearful responses at slaughter.
    Applied Animal Behaviour Science - APPL ANIM BEHAV SCI. 01/2009; 118(1).
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    ABSTRACT: Ninety-three crossbred steer calves (BW+/-SD=385+/-50 kg) were used (n=48 steers in yr 1, n=45 steers in yr 2) to examine the relationship among carcass traits, lean, bone, and fat proportions, visceral tissue weights, and pancreatic digestive enzyme activity with DMI, ADG, G:F, and residual feed intake. Calves were progeny from crossbred dams predominantly of Angus and Simmental breeding and were sired by Angus, Simmental, crossbred (predominantly of Angus and Simmental breeding), Charolais, or Piedmontese bulls. Steers were fed a high-moisture corn-based diet for an average of 112 d. Partial correlation analysis accounting for year, pen within year, week of slaughter within year, and sire breed was conducted. Gain:feed was negatively correlated (P <or= 0.04) with backfat thickness (r= -0.38), marbling score (r= -0.32), and trim and kidney fat weight proportion (g/kg of BW; r= -0.42). Residual feed intake (P=0.008; g/kg of BW; r=0.34) and backfat-corrected residual feed intake (P=0.005; r=0.29) were positively correlated with trim and kidney fat weight proportion. Gain:feed was negatively correlated (P<0.001) with total fat weight proportion (g/kg of rib; r= -0.45) and positively correlated (P <or= 0.03) with lean weight proportion (g/kg of rib; r=0.30) and bone weight proportion (g/kg of rib; r=0.28). Gain:feed was negatively correlated (P <or= 0.01) with subcutaneous fat weight proportion (g/kg of rib; r= -0.32) and intramuscular fat weight proportion (g/ kg of rib; r=0.37). Gain:feed was negatively correlated (P<0.001) with total visceral weight proportion (g/kg of BW; r= -0.44) and visceral fat weight proportion (g/kg of BW; r= -0.41) but was positively correlated (P=0.02) with spleen weight proportion (g/kg of BW; r=0.30). There were no significant correlations (P>0.10) between performance measures and the pancreatic proportional content of alpha-amylase and trypsin activity (units/kg of BW). These data indicate that carcass fatness traits and changes in the proportional weight of total viscera may be negatively associated with G:F and that visceral fat weight proportion and trim and kidney fat weight proportion may be important factors influencing this relationship.
    Journal of Animal Science 10/2008; 87(4):1548-57. · 2.09 Impact Factor
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    ABSTRACT: This study explores the interactions of sensory and nutritional environment with genotype occurring in current commercial pork production in Ontario, Canada, which may interact to result in poor quality meat. The study focussed on identifying factors and signalling mechanisms that contribute to poor meat quality, in order to develop strategies to reduce the incidence of unacceptable product quality. In the first phase of the work reported here, animal behaviour and muscle metabolism studies were related to meat colour, tenderness and water-holding capacity measurements from commercially-produced pigs killed in a commercial packing plant. A partial least squares analysis was used to determine the most important of the principal production variables, peri-mortem biochemical measures and post-mortem carcass condition variables studied, in terms of their influence on water-holding, toughness and colour (L*-value). Variations between producer and kill day at the slaughterhouse were very strong contributors to variability in these three meat quality parameters, followed by pH variations. A second phase of the study is currently underway to characterize patterns of gene expression related to extremes of end-product quality and to reduce quality variations by nutritional and behavioural management strategies.
    Meat Science 09/2008; 80(1):123-31. · 2.75 Impact Factor
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    ABSTRACT: Five beef cattle management regimens were evaluated for their effect on meat quality, fatty acid composition, and overall palatability of the longis-simus dorsi (LD) muscle in Angus cross steers. A 98-d growing phase was conducted using grass silage with or without supplementation of growth promotants (Revalor G and Rumensin) or soybean meal. Dietary treatments in the finishing phase were developed with or without supplementation of growth promotants based on exclusive feeding of forages with no grain supplementation, or the feeding of grain:forage (70:30) diets. Growth promotants increased (P < 0.01) shear force and tended (P = 0.06) to increase toughness of the LD muscle due to limited postmortem proteolytic activity (lower myofibrillar fragmentation index value; P = 0.02). Grain feeding increased DM and intramuscular fat content (P = 0.03 and P = 0.05, respectively) in the LD but decreased the sensory panel tenderness score (P = 0.01). Growth promotants increased (P </= 0.05) the proportion of C18:0, C20:0, trans isomers of C18:1, and cis-9, trans-11 C18:2. Exclusive feeding of forages increased the proportion of cis-9, cis-12, cis-15 C18:3 as well as several other isomers of the n-3 family and decreased in the ratio of n-6 to n-3 fatty acids in the LD muscle as compared with supplementing grain (P < 0.05). In addition, the forage-based diet increased (P < 0.01) the concentration in the intramuscular fat of several intermediates (cis-9, trans-11, cis-15 C18:3; trans-11, cis-15 C18:2; trans-11 C18:1) of ruminal biohydrogenation. Forage feeding also increased the proportion of cis-9, trans-11 C18:2 (P < 0.01) and decreased the concentration of trans-10 C18:1 in the LD muscle (P = 0.03). It is concluded that quality demands of health-conscious consumers can be met through a forage-finishing and growth promotants-free beef production system.
    Journal of Animal Science 08/2008; 86(7):1678-89. · 2.09 Impact Factor
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    ABSTRACT: Forty Angus-cross steers were used to evaluate 5 beef cattle management regimens for their effect on growth performance, carcass characteristics, and cost of production. A 98-d growing phase was incorporated using grass silage with or without growth promotants (trenbolone acetate + estradiol implants, and monensin in the feed) or soybean meal. Dietary treatments in the finishing phase were developed, with or without addition of the same growth promotants, based on exclusive feeding of forages with minimal supplementation or the feeding of barley-based diets. Overall, ADG for animals treated with growth promotants or fed supplemented diets (soybean meal and barley) was increased (P < 0.01) by 25 and 21%, respectively, compared with steers reared on grass silage alone and not treated with growth promotants. Except for HCW (P < 0.01), the use of growth promotants did not affect carcass measurements. Increasing the proportion of barley in the diet of steers finished on forage produced a heavier HCW (P < 0.01) and a greater (P < 0.01) quality grade. Because of their lower HCW and quality grade, cattle targeted to a forage-fed, nonimplanted beef market would need to garner a 16% premium to be economically competitive with cattle finished conventionally.
    Journal of Animal Science 09/2006; 84(8):2168-77. · 2.09 Impact Factor