J. L. Aalhus

The effect of conjugated linoleic acid on fat to lean repartitioning and feed conversion in pigs

The repartioning effect of CLA was evaluated using 108 pigs (54 gilts and 54 barrows) fed from 61.5 to 106 kg liveweight. Pigs were fed a cereal-based basal diet containing either 2% CLA or 2% sunflower oil (a rich source of α-linoleic acid). Irrespective of gender, pigs fed CLA tended to have reduced feed intakes (−5.2%, P = 0.07), improved feed conversion efficiences (−5.9%, P = 0.06) and similar rates of gain relative to sunflower oil fed pigs. In addition, pigs fed CLA deposited less subcutaneous fat (−6.8%, P = 0.01) and gained more lean (+2.3%, P = 0.03) than pigs fed sunflower oil. These data suggest CLA can be used as a repartioning agent in pigs and that further research to optimize the repartitioning effect is warranted. Key words: Pig, pork, swine, conjugated linoleic acid, CLA, repartioning

Residual feed intake and body composition in young growing cattle

Crossbred steers (n = 176), 7–8 mo of age and from the five BeefBooster strains (M1, M2, M3, M4 and TX), were used to determine the relationships between residual feed intake (RFI) and growth rate, body composition and heat production (HP), and to quantify differences in RFI independent of differences in body composition. Animals with different RFI levels were also characterized for growth, carcass and body compositional traits. Steers from each genetic strain were selected at random and serially slaughtered on 5 pre-selected days of the finishing period. Steers grew at 1.52 (SD = 0.22) kg d-1 and had dry matter intake (DMI) of 8.5 (SD = 1.0) kg d-1 during the last 71 to 183 d before slaughter. Metabolic mid-point weight, average daily gain (ADG), gain in empty body fat and gain in empty body water accounted for 67.9, 8.6, 3.9 and 1.1%, respectively, of the variation in actual feed intake. Similarly, metabolic mid-point weight (68.5%), ADG (8.2%), gain in ultrasound backfat thickness (1.8%), gain in ultra...

Distributions of conjugated linoleic acid (CLA) isomers in tissue lipid classes of pigs fed a commercial CLA mixture determined by gas chromatography and silver ion-high-performance liquid chromatography

Pigs were fed a commercial conjugated linoleic acid (CLA) mixture, prepared by alkali isomerization of sunflower oil, at 2% of the basal diet, from 61.5 to 106 kg live weight, and were compared to pigs fed the same basal diet with 2% added sunflower oil. The total lipids from liver, heart, inner back fat, and omental fat of pigs fed the CLA diet were analyzed for the incorporation of CLA isomers into all the tissue lipid classes. A total of 10 lipid classes were isolated by three-directional thin-layer chromatography and analyzed by gas chromatography (GC) on long capillary columns and by silver-ion high-performance liquid chromatography (Ag+-HPLC); cholesterol was determined spectrophotometrically. Only trace amounts (<0.1%; by GC) of the 9,11–18∶2 cis/trans and trans, trans isomers were observed in pigs fed the control diet. Ten and twelve CLA isomers in the diet and in pig tissue lipids were sepatated by GC and Ag+-HPLC, respectively. The relative concentration of all the CLA isomers in the different lipid classes ranged from 1 to 6% of the total fatty acids. The four major cis/trans isomers (18.9% 11 cis, 13 trans-18∶2; 26.3% 10 trans, 12 cis-18∶2; 20.4% 9 cis, 11 trans-18∶2; and 16.1% 8 trans, 10 cis-18∶2) constituted 82% of the total CLA isomers in the dietary CLA mixture, and smaller amounts of the corresponding cis,cis (7.4%) and trans,trans (10.1%) isomers were present. The distribution of CLA isomers in inner back fat and in omental fat of the pigs was similar to that found in the diet. The liver triacylglycerols (TAG), free fatty acids (FFA), and cholesteryl esters showed a similar patterns to that found in the diet. The major liver phospholipids showed a marked increase of 9 cis,11 trans-18∶2, ranging from 36 to 54%, compared to that present in the diet. However, liver diphosphatidylglycerol (DPG) showed a high incorporation of the 11 cis,13 trans-18∶2 isomer (43%). All heart lipid classes, except TAG, showed a high content of 11 cis,13 trans-18∶2, which was in marked contrast to results in the liver. The relative proportion of 11 cis,13 trans-18∶2 ranged from 30% in the FFA to 77% in DPG. The second major isomer in all heart lipids was 9 cis,11 trans-18∶2. In both liver and heart lipids the relative proportions of both 10 trans,12 cis-18∶2 and 8 trans,10 cis-18∶2 were significantly lower compared to that found in the diet. The FFA in liver and heart showed the highest content of trans,trans isomers (31 to 36%) among all the lipid classes. The preferential accumulation of the 11 cis,13 trans-18∶2 into cardiac lipids, and in particular the major phospholipid in the inner mitochondrial membrane, DPG, in both heart and liver, appears unique and may be of concern. The levels of 11 cis,13 trans-18∶2 naturally found in foods have not been established.

Relationship of texture profile analysis and Warner-Bratzler shear force with sensory characteristics of beef rib steaks.

Cyclical texture profile analysis (TPA) parameters measured using a star-shaped probe with two cycles of 80% penetration and Warner-Bratzler shear force (WBS) were compared as predictors of objective tenderness and subjective sensory characteristics of rib steaks from 52 beef loins. The TPA parameters of hardness, cohesiveness and chewiness were negatively correlated (P<0.05) with trained panel sensory characteristics of initial tenderness (r=-0.64, -0.41, -0.62, respectively), amount of connective tissue (r=-0.57, -0.27, -0.55, respectively), overall tenderness (r=-0.68, -0.39, -0.64, respectively) and overall palatability (r=-0.56, -0.37, -0.53, respectively). These sensory characteristics were also negatively correlated (P<0.05) with WBS (r=-0.61, -0.49, -0.60, -0.56, respectively). Stepwise regression analysis generated prediction equations that included the TPA parameters of hardness and adhesiveness, which accounted for 47, 36, 51 and 38% of the variation in initial tenderness, amount of connective tissue, overall tenderness and overall palatability, respectively. Prediction equations using WBS accounted for 37, 24, 36 and 31% of the variation in initial tenderness, amount of connective tissue, overall tenderness and overall palatability, respectively. Hence, TPA explained more of the variation in subjective sensory tenderness of the rib steaks than WBS.

The effects of feeding conjugated linoleic acid on subsequent pork quality

Feeding conjugated linoleic acid (CLA) has recently been shown to repartition fat to lean in pigs. The present study was undertaken to determine if feeding CLA affects pork quality. Pigs were fed a cereal-based diet containing either 2% CLA or 2% sunflower oil. Fifty-four pigs (27 gilts and 27 barrows) were fed per diet, and diets were fed from 61.5 to 106 kg liveweight. Diet did not affect postmortem longissimus thoracis (LT) glycogen utilization, lactate accumulation, or pH decline. Conjugated linoleic acid fed pigs had slightly higher LT temperatures at 3 h postmortem (+1.15 °C; P < 0.05), but subsequent LT shear force, drip loss and soluble protein levels were unaffected. Diet did not affect subjective LT scores for structure or color, but objective color measurements indicated LT from CLA-fed pigs had slightly higher chroma (color saturation) values (+0.84; P < 0.05). Longissimus thoracis from CLA-fed pigs also had increased subjective marbling scores (P < 0.01) and increased petroleum-ether-extracta...

Impact of piglet birth weight, birth order, and litter size on subsequent growth performance, carcass quality, muscle composition, and eating quality of pork

The objective of this study was to investigate the relationships among birth weight, birth order, or litter size on growth performance, carcass quality, and eating quality of the ultimate pork product. Data were collected from 98 pig litters and, with the addition of recording birth weight and birth order, farrowing and piglet management were according to normal barn practices. In the nursery and during growout, the pigs received the normal feeding program for the barn and, with the addition of individual tattooing, were marketed as per standard procedure. From 24 litters, selected because they had at least 12 pigs born alive and represented a range of birth weights, 4 piglets were chosen (for a total of 96 piglets) and sent to Agriculture and Agri-Food Canada-Lacombe Research Centre (Lacombe, Alberta, Canada) when they reached 120 kg for extensive meat quality and sensory analysis. Individual BW was measured at birth, on the day of weaning, 5 wk after weaning, at nursery exit, at first pull, and at the time of marketing. Litter sizes were divided into 3 categories: small (3 to 10 piglets), medium (11 to 13 piglets), and large (14 to 19 piglets). There were 4 birth-weight quartiles: 0.80 to 1.20, 1.25 to 1.45, 1.50 to 1.70, and 1.75 to 2.50 kg. Increased litter size resulted in reduced mean birth weight (P < 0.05), but had no effect on within litter variability or carcass quality (P > 0.05) when slaughtered at the same endpoint. Lighter birth-weight pigs had reduced BW at weaning, 5 and 7 wk postweaning, and at first pull and had increased days to market (P < 0.05). Birth weight had limited effects on carcass quality, weight of primal cuts, objective quality, and overall palatability of the meat at the same slaughter weight (P > 0.05). In conclusion, increased litter size resulted in decreased mean birth weight but no change in days to market. Lighter birth-weight pigs took longer to reach market. Despite some differences in histological properties, birth weight had limited effects on carcass composition or final eating quality of the pork when slaughtered at the same BW and large litter size resulted in more pigs weaned and marketed compared with the smaller litters. We concluded that based on the conditions of this study, other than increased days to market, there is no reason based on pig performance or pork quality to slow down the goal of the pork industry to increase sow productivity as a means to increase efficiency.

Protein Oxidation in Processed Meat: Mechanisms and Potential Implications on Human Health

Processed meats represent a large percentage of muscle foods consumed in the western world. Various processing steps affect the physicochemical properties of the meat, compromise its nutritional components, or produce some compounds that are of health concern. Hence, the impact of oxidation on human health and the aging process and the influence of diet on these harmful reactions are of growing interest. Past decades have seen more focus on lipid oxidation, microbial deterioration, and pathogenicity, as well as production of carcinogenic compounds during meat processing. The oxidation of protein, which is a major component in meat systems, has received less attention. Protein oxidation has been defined as a covalent modification of protein induced either directly by reactive species or indirectly by reaction with secondary by-products of oxidative stress. Not only are these modifications critical for technological and sensory properties of muscle foods, they may have implications on human health and safety when consumed. Cooking, for example, has been observed to increase free radical generation while it also decreases the antioxidant protection systems in meat, both of which contribute to protein oxidation. Many other meat processing techniques, as well as other emerging technologies, may significantly affect protein oxidation and protein overall quality. This paper explores the current understanding of meat processing techniques and their possible effects on the status of protein oxidation and nutritional value, as well as their possible implications on human health.

CONJUGATED LINOLEIC ACID-ENRICHED BEEF PRODUCTION

Canadian beef consumption is approximately 31 kg per annum, or a third of all meats consumed. Beef is a nutrient-rich food, providing good quality protein, vitamins B-6 and B-12, niacin, iron, and zinc. However, animal fats have gained the reputation of being less healthy. The identification of the anticarcinogenic effects of beef extracts due to the presence of conjugated linoleic acid (CLA) has heightened interest in increasing the amount of CLA deposited in beef. Beef cattle produce CLA and deposit these compounds in the meat; thus, beef consumers can receive bioformed CLA. Beef contains both of the bioactive CLA isomers, namely, cis-9, trans-11 and trans-10, cis-12. The relative content of these CLA isomers in beef depends on the feeds consumed by the animals during production. Feeding cattle linoleic acid-rich oils for extended periods of time increases the CLA content of beef. Depending on the type and relative maturity of the pasture, beef from pasture-fed cattle may have a higher CLA content than beef from grain- or silage-fed cattle. In feedlot animals fed high-grain diets, inclusion of dietary oil along with hay during both the growth and finishing phases led to an increase in CLA content from 2.8 to 14 mg/g beef fat, which would provide 77 mg CLA in an 85-g serving of beef. The CLAs appear to be concentrated in intramuscular and subcutaneous fat of beef cattle, with the CLA trans-10, cis-12 isomer being greater in the subcutaneous fat.

Assessment of the chemical and cooking properties of the major beef muscles and muscle groups

Thirty-three muscles or muscle groups were separated from 25 Canada AA beef carcasses. Each of these muscles and muscle groups was subsampled, and the contents of moisture, fat, soluble hydroxyproline, insoluble hydroxyproline, and total hydroxyproline were determined. In addition, a 1-kg roast from each muscle or muscle group was used to determine thaw-drip losses, cooking times, and total cooking losses. Cooking times ranged from 51.0 to 111.3 min/kg (S.E.=2.90). Thaw-drip losses ranged from 1.26 to 10.05% (S.E.=0.40). Total cooking losses ranged from 21.51 to 33.26% (S.E.=0.70). Moisture content ranged from 666.4 to 761.8 mg/g (S.E.=0.23). Fat content ranged from less than 30 to 118.7 mg/g (S.E.=0.25). The amount of total hydroxyproline on a dry, defatted basis ranged from 17.8 to 117.4 μMol/g (S.E.=2.24). Insoluble hydroxyproline ranged from 15.2 to 101.9 μMol/g, (S.E.=1.70), and soluble hydroxyproline ranged from 2.1 to 30.9 μMol/g (S.E.=0.78). Percent soluble hydroxyproline ranged from less than 10 to more than 30% (S.E.=0.79). Such wide variation in cooking and chemical properties undoubtedly has a considerable impact on the palatability attributes and consumer acceptance of beef. However, greater understanding of the chemical composition of muscle will provide a basis for the development of technologies to enhance the palatability of individual muscles and muscles groups.

The effect of ractopamine on myofibre distribution and morphology and their relation to meat quality in swine

One hundred and twenty-eight purebred Lacombe pigs (equal number of barrows and gilts) were assigned to one of four treatments at 64 kg and fed a commercial grower-finisher diet ad libitum to which ractopamine (RAC) was incorporated (0, 10, 15 or 20 mg kg(-1)). Pigs were slaughtered at 100 kg. Histological samples were collected from the semimembranosus (SM) and the psoas major (PM) muscles from the 0 and 20 mg kg(-1) RAC groups. Meat quality and muscle composition data were collected for all pigs. A significant 3-way interaction for muscle weight involving treatment, muscle and gender (P = 0·01) indicated that for the SM, gilts appeared to respond to RAC at a lower level of incorporation (10 mg kg(-1)) than barrows. Despite these differences in response at the gross muscle level, responses were similar at the cellular level for both muscles. The proportion of red fibres did not change (P = 0·21), the proportion of intermediate fibres decreased (P = 0·01) and the proportion of white muscle fibres increased (P = 0·02) in the mg kg(-1) RAC group compared to the controls. In addition, when compared to controls, average fibre diameters in the 20 mg kg(-1) RAC group remained constant in the red fibres, and increased significantly in both the intermediate and white fibres (P = 0·01 and 0·02, respectively). Over both muscles Kramer Press values were significantly higher (P = 0·030 in the RAC-fed pigs than in the controls. Incorporation of RAC into the diet did not result in any changes to crude protein or total and soluble hydroxyproline levels. Crude fat tended to increase in the 15 mg kg(-1) RAC treatment in the SM and decreased in the 20 mg kg(-1) RAC treatment in the PM. The shift in fibre type, and the associated changes in fibre size, may contribute to the increased shear values found in RAC-fed pigs.