I. B. Mandell

Relationships among measures of growth performance and efficiency with carcass traits, visceral organ mass, and pancreatic digestive enzymes in feedlot cattle

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.

Comparison of alternative beef production systems based on forage finishing or grain-forage diets with or without growth promotants: 2. Meat quality, fatty acid composition, and overall palatability

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.

Effects of gender and breed on carcass traits, chemical composition, and palatability attributes in Hereford and Simmental bulls and steers

The effects of gender and breed on carcass and chemical composition, and palatability attributes were investigated in 222 Hereford and Simmental bulls and steers. Cattle were progeny of 12 Hereford and 17 Simmental sires using six half-sibs per sire. Bulls were fed a 64% TDN diet to slaughter endpoints of either 4, 7, or 10 mm backfat. Steers were fed diets containing up to 80% TDN until cattle achieved 7 to 10 mm backfat. Gender effects were confounded with diet to take into account differences in commercial cattle feeding vs. bull testing. Gender by breed interactions (P < 0.05) were present for carcass traits due to large between breed differences for bulls as limited ability for Simmental bulls to fatten resulted in deposition of more lean tissue. Gender by breed interactions (P < 0.05) were present for shear, and tenderness and flavour attributes. Beef from Simmental bulls was characterized with less flavour intensity, and tough due to high scores for shear and time spent chewing, and low scores for softness and tenderness. Shear, tenderness, and flavour attributes were similar among Herefords of both genders and Simmental steers. Palatability attributes for Hereford bulls managed in a bull test program were non-significantly different than those from Hereford steers managed in a feedlot environment, suggesting that palatability attributes for steers could be predicted from bulls. This was not the case with Simmental bulls probably due to limited fattening ability on a relatively low energy bull test diet.

Effects of diet and slaughter endpoint on carcass composition and beef quality in Charolais cross steers

One hundred and eight Charolais cross steers were used to compare forage versus grain feeding as affected by slaughter endpoint on carcass composition and palatability attributes of beef. Diets included a 97% alfalfa silage ration or 68% high moisture corn, 25% alfalfa silage ration from start of test to finish or a ration of 97% alfalfa silage from start of test to day 42 of the trial followed by the 68% high moisture corn ration until slaughter. Cattle were slaughtered at either 4, 7, or 10 mm ultrasound backfat. Grain feeding increased (P = 0.01) average daily gain and decreased (P = 0.01) days to finish, while carcass weight and grade fat were similar (P > 0.10) between diets. Palatability attributes were generally unaffected by diet with the exception of slightly less (P = 0.09) beef flavour and more (P = 0.01) off flavour in forage-fed beef versus grain-fed beef. Higher (P = 0.01) concentrations of linolenic acid and lower (P = 0.09) concentrations of oleic acid in forage-fed beef may be partially r...

Disparity of dietary effects on collagen characteristics and toughness between two beef muscles

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.

Effect of management strategy on growth performance, carcass characteristics, fatty acid composition, and palatability attributes in crossbred steers

Crossbred steers (n = 136) were used to evaluate the effect of management strategy on growth performance, carcass characteristics, and fatty acid composition and palatability attributes of beef. Management strategies included: (1) high grain (75% high moisture corn) finishing (HG), or (2) backgrounding with restricted feeding of an alfalfa silage ration for 112 d, followed by HG until slaughter (BKG). Steers were slaughtered at 8–10 mm ultrasound backfat. Backgrounding increased (P 0.10) by management strategy. Longissimus muscle palatability attributes and shear force did not differ (P > 0.10) between management strategies, whereas BKG increased (P < 0.03) softness, overall tenderness, chewiness, and rate of breakdown scores, and decreased (P < 0.09) juiciness scores in semitendinosus ...

Single nucleotide polymorphisms for feed efficiency and performance in crossbred beef cattle.

BackgroundThis 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.ResultsStrong 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.ConclusionsThis 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.

Effects of diet, breed and slaughter endpoint on growth performance, carcass composition and beef quality traits in Limousin and Charolais steers

Ninety-six Charolais and Limousin steers were used to evaluate 75% grain (whole barley or corn) diets and two slaughter endpoints (7 mm backfat or 568 kg liveweight) in an experiment designed to constrain carcass weights to under approximately 341 kg yet produce optimal beef quality. Each breed was represented by eight progeny from each of six sires. The trial was terminated after 281 d feeding regardless of individual steers attaining designated slaughter endpoints. Limited availability of dietary energy in whole-barley diets resulted in decreased (P < 0.01) average daily gain and increased (P < 0.01) dry matter intake, feed/gain and days on feed for barley- vs. corn-fed cattle. Charolais outgained (P < 0.05) Limousin but dry matter intake was similar on a g BW00.75 basis. Feeding to 568 kg liveweight was associated with high (P < 0.10) ADG and decreased (P < 0.05) feed/gain compared with feeding to 7 mm. Corn feeding increased (P < 0.001) carcass weights, fat deposition and longissimus muscle area. Lean...

Effects of breed and dietary energy content within breed on growth performance, carcass and chemical composition and beef quality in Hereford and Simmental steers

Forty-eight Hereford and 60 Simmental steers were used to evaluate breed differences as affected by dietary energy content on growth performance, carcass and chemical composition, and beef quality. Diets were based on corn silage, alfalfa haylage, whole corn, and SBM and were formulated to provide 2.52 to 2.81 Mcal kg−1 ME and 11.7 to 12.6% protein in the growing phase and 2.69 to 2.86 Mcal kg−1 ME and 9.7 to 10.4% protein in the finishing phase. Low- and high-ener-gy diets were formulated for each breed with the high-energy diet for Hereford serving as the low-energy diet for Simmental. Steers were slaughtered after attaining 8 to 10 mm backfat determined by ultrasound. Higher energy diets increased (P < 0.09) average daily gain (ADG) and feed efficiency within both breeds. Hereford gained more rapidly (P = 0.074) and were more (P = 0.001) efficient in converting feed to gain than Simmental. High-energy diets decreased (P = 0.001) days on feed for both breeds and increased (P = 0.001) carcass weights for...

The determination and correlation of reproductive parameters of performance-tested Hereford and Simmental bulls

Purebred Hereford and Simmental bulls (n = 120), managed similarly to bulls in the Ontario Bull Evaluation Program, were evaluated for reproductive parameters. Four diets, equivalent except for the form of dietary fiber, were fed in a growth performance trial. Diet had no direct effect (P > 0.10) on any of the reproductive variables examined. Of the 117 bulls that had complete breeding soundness evaluations, 75% were classified as satisfactory potential breeders, 24% as questionable potential breeders and 1% as unsatisfactory potential breeders. The 2 breeds were significantly different (P < 0.05) for several end of test parameters. When controlling for age and weight differences, Herefords had a higher backfat thickness, smaller scrotal circumference, lower paired testicular weight and lower epididymal weight. Semen morphology and motility did not differ (P > 0.10) between the breeds. When examining simple correlations, scrotal circumference was highly correlated with paired testicular weight, moderately correlated with epididymal weight, daily sperm production and extragonadal sperm reserves, and negatively correlated with backfat thickness. Scrotal circumference was not related to backfat thickness when controlling for breed effects. The degree of germinal epithelium loss was moderately and negatively correlated with the percentage of spermatozoa with normal morphology and progressive motility, epididymal sperm reserves and epididymal weight, but was not correlated with scrotal circumference.