A QTL study of live animal and carcass traits in beef cattle was carried out in New Zealand and Australia. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. This paper reports on weights of eight organs (heart, liver, lungs, kidneys, spleen, gastro-intestinal tract, fat, and rumen contents) and 12 fat composition traits (fatty acid (FA) percentages, saturated and monounsaturated FA subtotals, and fat melting point). The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. For organ weights and fat composition traits, 10 and 12 significant QTL locations (P<0.05), respectively, were detected on a genome-wide basis, in combined-sire or within-sire analyses. Seven QTL significant for organ weights were found at the proximal end of chromosome 2. This chromosome carries a variant myostatin allele (F94L), segregating from the Limousin ancestry, and this is a positional candidate for the QTL. Ten significant QTL for fat composition were found on chromosomes 19 and 26. Fatty acid synthase and stearoyl-CoA desaturase (SCD1), respectively, are positional candidate genes for these QTL. Two FA QTL found to be common to sire groups in both populations were for percentages of C14:0 and C14:1 (relative to all FAs) on chromosome 26, near the SCD1 candidate gene.

Vitamin A plays a critical role in many essential life processes. In herbivores, it is either derived from plant beta-carotene or directly as a dietary supplement. In cattle, vitamin A has the potential to influence various carcass traits that are sought by specific beef markets. A group of 20 Angus steers was removed from pasture and fed a low beta-carotene and vitamin A cereal-based ration on a feedlot for 308 days. Ten of the steers were supplemented with vitamin A (retinyl palmitate, 60 IU of vitamin A/100 kg body weight/day) and the other ten received no supplement. The results demonstrated that restriction of vitamin A intake changed intramuscular fat deposition without changing subcutaneous fat depots. Angus steers that had been depleted of vitamin A showed increased intramuscular fat in the longissimus thoracis et lumborum (LTL) by 35% (P < 0.026) and seam fat area at the quartering site by 33% (P < 0.0273), when compared with cattle supplemented with vitamin A. There were no changes in intramuscular fat in the semitendinosus. Visually assessed marbling scores were also higher (19%; P < 0.094) in the non-supplemented, depleted group. There was no effect of vitamin A depletion on cattle growth and other meat traits (eye muscle area, meat colour, pH, meat cut weight), meat eating attributes (tenderness, cooking loss) or muscle fibre diameter. The only difference (P < 0.0177) among the meat traits was fat colour where depleted animals had whiter fat than the controls. Moreover, the fat from the vitamin A depleted group was softer with a lower melting point. We conclude that the reduced vitamin A consumption, leading to vitamin A depletion, increases intramuscular fat. On the other hand, the vitamin A depletion did not increase subcutaneous fat depth or change other meat quality traits, suggesting that marbling and these other traits are not invariably related. (C) 2008 Elsevier B.V. All rights reserved.

A group of Angus beef cattle was removed from temperate pastures and fed a very low β-carotene cereal-based ration in a feedlot for over 300 d. Half the group was supplemented weekly with retinyl palmitate (at the rate of 60,000 IU vitamin A/100 live weight (LW)/day), sufficient to offset clinical vitamin A deficiency; the other half received no supplement. Blood was sampled from all animals at biweekly intervals to assess β-carotene and vitamin A status. Adipose tissue was sampled by biopsy on three occasions throughout the experimental period and at slaughter to assess FA composition. Muscle was sampled at slaughter to determine the intramuscular fat content. The mean plasma concentration of β-carotene of all animals fell from an initial value of 20.1 to 5.2 μg/mL at 14 d, to 1.4 μg/mL at 35 d, and to zero at 105 d. Mean vitamin A in plasma was not significantly different between the treatment groups initially. The values then rose to almost twice their initial values by 35 d, but subsequently fell to below initial values by day 119. Thereafter, plasma vitamin A of the supplemented group was significantly greater than that of the unsupplemented group (P<0.05). Muscle samples at slaughter from supplemented animals contained significantly (P<0.01) more intramuscular lipid (13.0 vs. 9.6%). Major changes occurred over time in FA composition in both groups. Saturated FA decreased as monounsaturated FA increased over the first 60 d. An index of desaturation of FA was significantly lower (P<0.001) in the vitamin A-supplemented group than in the nonsupplemented group. M.P. of the adipose tissue of nonsupplemented animals was 32.3°C, significantly less (P<0.05) than that of supplemented animals (34.1°C). Feeding vitamin A was associated with less intramuscular fat but with a less desirable (less unsaturated, more solid) FA profile.

Ruminant tissues and products contain conjugated linoleic acids (CLA) due to biohydrogenation in the rumen.We hypothesize that kangaroos would have higher concentrations of CLA compared to lambs due to incomplete biohydrogenation of fatty acids in the kangaroo foregut.Fatty acid composition of adipose tissue (including cis 9, trans 11 CLA) from lambs and kangaroos were signifi cantly different.The concentrations of CLA and its precursor trans vaccenic acid (TVA) in the adipose tissue of kangaroos were approximately four and fi ve times that of lambs.Kangaroo fat was signifi cantly less saturated and had a lower melting point.

Studies of the desaturation of saturated fatty acids in animals may help explain conflicting reports of the response of coronary heart disease (CHD) to beta-carotene in humans. A negative relationship exists between desaturation and adipose beta-carotene in cattle when they consume different quantities of beta-carotene. Opposing this finding, however, is a positive relationship between desaturation and adipose beta-carotene when cattle are fed the same quantity of beta-carotene. The reason for this apparent contradiction appears to be due to differences in consumption, or variability in the metabolism of beta-carotene. Animals that efficiently metabolize beta-carotene to vitamin A have low desaturation but high antioxidant potential. These results in animals show some similarity between the consumption of the antioxidant beta-carotene and the risk of coronary heart disease where the oxidation of low-density lipoproteins (LDL) is believed to play a role in the development of atherosclerotic plaque. Genetic differences in carotenoid metabolism in humans, similar to those in animals, would assist in explaining differences in lipoprotein oxidation in humans and variation in the risk of coronary heart disease.

Animal GeneticsVolume 35, Issue 2 p. 163-163 Physical mapping of the stearoyl-CoA desaturase (SCD) locus in sheep H. Kuchel, H. Kuchel Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorB. D. Siebert, B. D. Siebert Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorC. D. K. Bottema, C. D. K. Bottema Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorG. C. Webb, G. C. Webb Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorA. M. Crawford, A. M. Crawford AgResearch, Molecular Biology Unit, Biochemistry Department, University of Otago, Box 56, Dunedin, New ZealandSearch for more papers by this authorS. J. Duncan, S. J. Duncan AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New ZealandSearch for more papers by this authorP. A. McDonald, P. A. McDonald AgResearch, Molecular Biology Unit, Biochemistry Department, University of Otago, Box 56, Dunedin, New ZealandSearch for more papers by this authorJ. C. McEwan, J. C. McEwan AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New ZealandSearch for more papers by this authorW. S. Pitchford, W. S. Pitchford Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this author H. Kuchel, H. Kuchel Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorB. D. Siebert, B. D. Siebert Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorC. D. K. Bottema, C. D. K. Bottema Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorG. C. Webb, G. C. Webb Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this authorA. M. Crawford, A. M. Crawford AgResearch, Molecular Biology Unit, Biochemistry Department, University of Otago, Box 56, Dunedin, New ZealandSearch for more papers by this authorS. J. Duncan, S. J. Duncan AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New ZealandSearch for more papers by this authorP. A. McDonald, P. A. McDonald AgResearch, Molecular Biology Unit, Biochemistry Department, University of Otago, Box 56, Dunedin, New ZealandSearch for more papers by this authorJ. C. McEwan, J. C. McEwan AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New ZealandSearch for more papers by this authorW. S. Pitchford, W. S. Pitchford Animal Science, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, AustraliaSearch for more papers by this author First published: 17 March 2004 https://doi.org/10.1111/j.1365-2052.2004.01114.xCitations: 4 W. S. Pitchford ([email protected]) Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume35, Issue2April 2004Pages 163-163 RelatedInformation

An experiment examined Δ9 desaturase activity and FA composition in subcutaneous adipose tissue in two differing breeds of cattle. Jersey-sired cattle had significantly higher rates of desaturase activity than Limousin-sired cattle (1.55 vs. 0.75 nmol/mg protein/min). This difference was also demonstrated by a lower concentration of individual (e.g. 18∶0) and total saturated FA (38.3 vs. 45.1 wt%), and a higher concentration of individual (e.g., 16∶1) and total monounsaturated FA (58.2 vs. 52.7 wt%) in the Jersey animals. Other indices of desaturation calculated from the FA composition showed this same difference. The slip point of adipose tissue of Jersey cattle (36.8°C) was significantly lower than that of Limousin cattle (39.2°C), but Jersey adipose tissue had a greater content of β-carotene. The positive relationship between adipose tissue β-carotene and desaturation opposes the negative relationship between dietary β-carotene and desaturation determined elsewhere. These results, however, lead to the hypothesis that some cattle have a reduced capacity to metabolize β-carotene to various forms of vitamin A, a compound that can reduce Δ9 desaturase enzyme activity. In addition, the higher level of intramuscular fat in Jersey cattle (6.97 vs. 3.82%) is possibly related to a lack of inhibition of the adipocyte differentiation genes by vitamin A.

SUMMARY The aim of this study was to investigate the relationships between various estimates of marbling in Jersey and Limousin crossbred steers with intramuscular fat percentage (IMF%) as determined by solvent extraction. The correlations between IMF% and various marbling scores ranged from 0.67 to 0.79. AUS-MEAT, MSA or USDA scoring systems were correlated, and ranked animals similarly. However, the best correlation with IMF% was found to be with the AUS-MEAT marbling score. When the range of IMF% was assigned to different scores within each system, the AUS-MEAT and USDA systems were similar whereas MSA scores had a higher concentration of fat per score and a broader range of concentrations. The only factors influencing assessment of marbling were IMF% and breed. Other traits, such as loin temperature, eye muscle area, melting point, fat colour and meat colour were not significant. Jersey cross steers had higher marbling scores (1.9 vs 0.8) and IMF% (6.4 vs 4.4%) than Limousin cross. A breed by sire interaction in marbling was also detected.

Mature Hereford cows (766) were mated to 97 sires from seven breeds (Jersey, Wagyu, Angus, Hereford, South Devon, Limousin, and Belgian Blue), resulting in 1,215 calves born over 4 yr (1994 to 1997). These cattle comprised Australia's 'Southern Crossbreeding Project." Heifers were slaughtered at an average of 16 mo with hot standard carcass weight of 219 kg and 9 mm fat over the rump. Steers were slaughtered at an average of 23 mo with carcass weight of 319 kg and 13 mm fat over the rump. Meat and fat samples were taken from the carcass on the day after slaughter for subsequent laboratory analysis of i.m. fat content and fatty acid composition. Data were analyzed using uni- and bivariate animal models containing fixed effects of cohort, management group, birth month, and sire breed. March-born calves had fat with a 0.5 degrees C lower melting point, 0.6% higher total monounsaturated fatty acids, and 0.7% higher fatty acid desaturation index than calves born in April. Steers born in 1997 were the only cohort finished on pasture, and they had much more yellow fat than the other cohorts. Four heavy breed crosses (Angus, South Devon, Limousin, and Belgian Blue) averaged 284 kg carcass weight, followed by purebred Hereford (268 kg), Wagyu (244 kg) and Jersey (236 kg). Angus had the greatest fat depth (14.3 mm), ahead of Hereford and Wagyu (11.9 mm), Jersey (10.7 mm), South Devon and Limousin (9.9 mm) and Belgian Blue (8.0 mm). Jersey, Wagyu, and Angus had themost i.m. fat (4.6%), followed by Hereford and South Devon (3.8%), and Limousin and Belgian Blue (3.1%). The highly marbled Jersey and Wagyu had softer fat (6% lower fat melting point) than the other breeds. Angus were more highly marbled, similar to Jersey and Wagyu, but had harder fat similar to the leaner breeds. Heritabilities for all traits were low to moderate (16 to 36%). Genetic correlations between fatty add composition and carcass traits were not significant, indicating little evidence of antagonisms between traits that would prevent genetic progress in both production and quality.

SummaryAdipose tissues from the 12th–13th rib interface were sampled at weaning (324 cattle) and slaughter (310 cattle). The animals were progeny from Hereford dams sired by Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu. Fatty acid composition of the triacylglycerol fraction at both stages was measured by gas‐liquid chromatography. Estimates of heritability and genetic and phenotypic correlations at weaning and slaughter were computed by restricted maximum likelihood using a sire model in both univariate and multivariate analyses. Results indicated that generally, there were strong, positive genetic correlations between fatty acids at weaning and slaughter (as high as 0.98). Phenotypic correlations were however, low and poor (0.04–0.44). Heritability (h2) estimates at weaning were low to moderate, ranging from 0–0.31. However, at slaughter, h2 estimates were generally higher than at weaning: Stearate, oleate and total monounsaturates had h2 estimates of 0.43, 0.37 and 0.40, respectively. Other carcass traits such as marbling score and melting point of fat had h2 estimates of 0.20 and 0.52, respectively. Significant breed, sex and location differences in fatty acid composition were also observed at weaning and slaughter.

Summary Subcutaneous adipose tissues were biopsied in purebred Jersey (n=17), purebred Limousin (n=17) and reciprocal F 1 Jersey × Limousin crossbred (n=33) calves at the age of 9–10 months. Triacylglycerol fatty acids were extracted and analysed for sex and breed differences. Heterosis, additive and maternal variances were estimated. All calves were pasture‐fed in a single management group and biopsied from the same anatomical site. Heifer calves had significantly higher proportions of palmitoleate, total mono‐unsaturated fatty acids, desaturation index and lower stearate than steer calves. Significant breed differences were observed in that Limousin calves had the highest proportions of palmitate and total saturated fatty acids, whereas Jersey calves had the most palmitoleate and desaturation index. Dominance effects were evident in the proportions of palmitate, stearate, desaturation and elongation enzyme indices due to the observed highly significant heterosis effect. Myristate, palmitate and total saturated fatty acids were considered heritable due to the observed highly significant additive genetic effect.

An experiment was conducted to determine if limiting the amount of β-carotene in a diet could increase the expression of the gene responsible for the desaturation of saturated fats in a ruminant. Two groups of lambs were raised on either a cereal grain/faba bean diet, or a pasture legume diet. The diets contained equal concentrations of protein and metabolisable energy, but the pasture legume diet contained at least 20 times more β-carotene than the cereal diet. The groups were fed so that they grew at very similar rates. After 14 weeks, a sample of subcutaneous fat was removed by biopsy. This demonstrated that newly deposited fat was distinctly different in composition between the groups. The animals were slaughtered after a further 4 weeks and internal body and subcutaneous fat was removed from the carcasses. Major differences were found in fatty acid composition and melting point of the fat. In particular, the lower β-carotene diet decreased C18:0 stearate (saturated) and increased C18:1 oleate (mono-unsaturated). Some other increases occurred C18:2 and a trans C18:1, probably as a result of the lipid present in corn. The melting point of the fat in animals fed low levels of β-carotene was almost 10°C less than that fed a high β-carotene diet. It is likely that one of the metabolites of β-carotene inhibits nuclear expression of the desaturase gene.

SummaryFatty acid composition, marbling score and melting point data collected between 1994 and 1996 were analysed. The data were from the adipose tissue of 764 Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu crossbred cattle slaughtered after lot‐feeding at 500 days of age. The aim was to investigate sire‐breed differences and to estimate heritability and genetic and phenotypic correlations. Significant breed differences were found: Jersey crosses had the highest marbling score and Belgian Blue crosses had the lowest. Limousin crosses had the highest melting point and Jersey crosses the lowest. South Devon crosses had the highest proportion of stearate and Jersey crosses the lowest. Desaturation indices in C16 and C18 fatty acids were highest in Jersey crosses and lowest in Limousin and South Devon crosses. In contrast, there were no breed differences in the proportions of palmitate, oleate, total saturated, total mono‐unsaturated fatty acids and elongation index. Heritability estimates of individual fatty acids and their summations, melting point and marbling were low to moderately low (0.05–0.27). Strong genetic correlations of melting point and desaturation index in C16 fatty acids (‐0.93), melting point and stearate (0.62), marbling and stearate (‐0.71) and marbling and desaturation index in C18 fatty acids (0.62) were observed. Phenotypic correlation were generally low. The results imply that fatty acids in the adipose tissue of lot‐fed cattle have a moderately low heritability, hence genetic progress might be slow.

SummaryLongissimus dorsi muscle tissue was biopsied between the 12th and 13th ribs of 96 purebred Jersey, purebred Limousin and Jersey × Limousin crossbred calves at the age of 9–10 months. Fatty acids of the phospholipid fraction were extracted and analysed for sex and breed differences. Heterosis, additive and maternal variances were estimated. All calves grazed pasture in a single management group and were biopsied from the same anatomical site. Steer calves had significantly higher proportions of the 14 : 0, 14 : 1, 18 : 2, 20 : 3 fatty acids and less of the 16‐di‐methyl‐acetal than heifer calves. Significant breed differences were observed: Limousin calves had the highest proportions of 16 : 0, 24 : 0 and saturated fatty acids (SFA), whereas Jersey×Limousin calves had the most 18 : 0 and elongation index. Dominant effects were evident in the proportions of 16 : 0, 18 : 0, SFA and elongation index. Additive genetic effects were significant in the proportions of 16 : 0, 18 : 0, 18 : 1n‐9, total SFA and desaturation and elongation indices. Combined maternal and additive effects were significant for long chain polyunsaturated fatty acids 18 : 2, 20 : 3 and 20 : 4.

The fat content of muscle and the fatty acid profile and melting point of subcutaneous fat was examined in the progeny of three years of crossbreeding Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu sires with Hereford cows. Significant cohort and sire breed effects were recorded for most traits. Heritability was moderate in most cases. As expected, significant breed differences were noted in the fat content of muscle, but also apparent was the difference in the degree of unsaturation in Jersey and Wagyu progeny. Angus, Hereford, Belgian Blue, South Devon and Limousin animals varied in some fatty acid measures. Jersey and Wagyu had fat with lower melting point (a function of fatty acid composition) and South Devon and Limousin had higher melting point than the remaining breeds.

We investigated the fatty acid composition of the phospholipid fraction of the shoulder muscle (triceps brachii) from Jersey and Limousin yearling steers, yearling heifers, and nonlactating cows. The aim was to study breed, sex, and age differences. Significant breed differences in some individual fatty acids were apparent between Jersey and Limousin cows. Limousin cows had more palmitate, vaccenate, arachidonate, and less gamma-linolenate and eicosapentanoate than Jersey cows. Age differences were significant: proportions of palmitate, stearate, and oleate decreased and linoleate, arachidonate, and total polyunsaturates increased with age. Most of the breed x age interactions were not significant. Also, phospholipids of Jersey and Limousin cows did not differ in total saturated, monounsaturated, and polyunsaturated fatty acids. Yearling data revealed significant sex differences in most of the fatty acids, including total monounsaturates and polyunsaturates. Yearling steers had more myristate, palmitoleate, stearate, and total monounsaturates and less linoleate, arachidonate, eicosapentanoate, and total polyunsaturates than heifers. Breed differences were also significant: Limousin yearlings had more di-homogamma-linolenate and erucate and less eicosapentanoate and nervonate than their Jersey counterparts. The sex x breed interaction was not significant for most of the fatty acids. These results imply that breed, age, and sex are important factors that influence the fatty acid composition of muscle phospholipids in cattle.