Increase In Intramuscular Fat Research Articles

Effects of nutritional level on pork quality and gene expression of μ-calpain and calpastatin in muscle of finishing pigs

The study was designed to investigate the effects of nutritional level (control diet (CD), 14.19% crude protein, 13.81MJ of DE/kg; low nutritional level diet (LND), 11.08% crude protein, 12.55MJ of DE/kg) on pork quality and gene expression of mu-calpain and calpastatin in muscle of finishing pigs. The LND treatment increased drip loss (P<0.05), had a trend to increase intramuscular fat (IMF) content (P=0.09), decreased Warner-Bratzler shear force (WBSF) of pork (P<0.05), improved mRNA level of mu-calpain (P<0.05) in skeletal muscle, but had no effect on gene expression of calpastatin, compared with the CD treatment. These data suggest that a moderately reduced energy and protein diet increased pork tenderness and intramuscular fat. The increase in tenderness by LND treatment may be partly due to increased gene expression of mu-calpain in muscle.

Evidence for a new allele at the SERCA1 locus affecting pork meat quality in part through the imbalance of Ca2+ homeostasis

Sarcoendoplasmic reticulum Ca2+-ATPase 1 (SERCA1) as a Ca2+ release channel plays a key role in the relaxation of skeletal muscle through pumping cytosolic Ca2+ into the SR (sarcoplasmic reticulum). In this study, a novel single nucleotide polymorphism (SNP) in exon 8 (C > T) was detected by tetra-primer ARMS-PCR and the tissue expression pattern of SERCA1 was analyzed in eleven tissues. A model of primary skeletal muscle cells in vitro exposed to dexamethasone (DEX, a synthetic corticosteroid) was also employed to determine whether stress hormones cause an increase in intracellular Ca2+ concentration that is associated with alteration in SERCA1 and in turn subsequently affect meat quality. The results showed that the CC genotype has lower content intramuscular fat and higher water than pig carrying the genotype CT and CC. In addition, the additive effects were both significantly (P < 0.05) and allele T seemed to be associate with increase in intramuscular fat, while decrease in water content. Accompanied with previous studies, the high abundance of porcine SERCA1 was found in skeletal muscle tissue. DEX markedly down-regulated the expression of SERCA1, leading to Ca2+ overload. Furthermore, the imbalance of Ca2+ homeostasis up-regulated the transcription level of Calpain1. Taken together, we demonstrated a novel mechanism that the changes in expression of SERCA1 potential disturb the normal Ca2+ channel as well as the balance of Ca2+ homeostasis and which in turn finally activated Ca2+-dependent proteases such as Calpain1 which could affect meat quality.

Effect of weight and sex on intramuscular fat amounts in relation to the formation of selected carcass cuts in pigs

The objective of this study was to examine the influence of weight and sex on fat amounts in relation to the formation of selected carcass cuts in final hybrid pigs commonly kept in the Czech Republic. During the experiment 123 hybrid pigs of various genotypes were tested. The pigs were slaughtered at an average weight of 120.4 kg and dissected in detail. The tested pigs were divided into 5 weight categories, while the tissue composition of ham, joint, shoulder and neck was monitored with emphasis on the assessment of IMF content. A decrease in the lean meat proportion was shown, as well as an increasing fat proportion with increasing weight: for the joint the difference was 4.19%, for the ham 3.9%, shoulder 3.0%, and neck 2.31%. With increasing weight, a moderate increase in intramuscular fat occurred, whereas the differences between group 1 and 5 were: 1.68% for the ham, 0.58% (shoulder), 0.4% (joint) and 0.37% (neck). Concerning the influence of sex, barrows had statistically insignificant intramuscular fat content compared with gilts (excluding the neck). As for the protein content in the monitored carcass cuts, no influence of live weight and sex was recorded.

Correlated Responses to Selection for Increased Intramuscular Fat in a Chinese Quality Chicken Line

The correlated response in traits encompassing meat quality, carcass, sexual maturity, egg production, and egg quality traits arising from selection for increased intramuscular fat (IMF) content of breast muscle were investigated in the fifth generation of a selection experiment including a line (F) selected for increased IMF and a randombred control line (C). The results showed that breast muscle IMF content in the F line (4.25%) was significantly higher (P < 0.001) than that in the C line (3.80%) after 5 generations of selection. The same trend was observed in IMF content in thigh muscle (20.03 vs. 19.41%, P < 0.05). The shear force of breast muscle in the F line was lower than that in the C line (1.82 vs. 2.12 kg, P < 0.01), whereas increases occurred in BW (P < 0.05), carcass weight (P < 0.05), breast muscle weight (P < 0.001), breast muscle percentage of live weight (P < 0.05), abdominal fat weight (P < 0.001), ovarian weight at 90 d of age (P < 0.05), and egg weight (P < 0.05) in the F line, relative to the C line. Age at first lay in the F line was 4.84 d earlier than that in the C line (P < 0.001). No differences were found between the 2 lines (P > 0.05) in the following traits: drip loss, meat color (L*, a*, and b*), carcass percentage, thigh muscle weight, thigh muscle percentage, abdominal fat percentage, first egg weight, egg number (until 43 wk), Haugh units, shell thickness, and egg shape. The results of the present study demonstrated that selection for breast muscle IMF leads to desirable changes in meat quality, carcass, sexual maturity, and egg production traits.

Effect of maternal dietary restriction during pregnancy on lamb carcass characteristics and muscle fiber composition1

Two experiments were conducted to determine whether the decreased proportion of fast muscle fibers seen previously in 2-wk-old lambs from ewes that were dietary restricted from d 30 to 70 of gestation are still evident in older lambs and what the consequences may be in terms of growth rates and carcass composition. Throughout both experiments, ewes were fed on an individual basis according to the recommended dietary allowance throughout pregnancy relative to metabolic BW (BW(0.73)). Control groups were fed as above, and the treatment groups had their nutrient supply reduced to 50% of this recommended allowance from d 30 to 70 (Exp. 1) or d 30 to 85 (Exp. 2) of gestation, after which they were returned to the same level of nutrition as the control group. All twin lambs were kept with their dams, and at 2 wk were given access to creep. After weaning, lambs were individually housed and fed ad libitum to 24 or 17 wk of age for Exp. 1 and 2, respectively. Although not significant (P = 0.18), growth to 24 wk (Exp. 1) resulted in a small decrease in the protein content and therefore an increase in the fat:lean ratio in the carcass of lambs subjected to maternal dietary restriction. This was not apparent when animals were slaughtered at 17 wk (Exp. 2; P > 0.68). Few significant effects of maternal dietary restriction on the fiber type composition of muscles were observed. In Exp. 1 the number of fast fibers increased (P < 0.008) with no effect on slow fiber number in LM. In Exp. 2 an increase in the total number of fibers in male lambs and an increase in type II (A and B) fibers in female lambs were observed in the LM, and an increase in IIB fiber number was observed in semitendinosus (ST) muscle from male lambs. Prenatal maternal dietary restriction during the time of muscle differentiation demonstrated an increase in type IIB muscle fibers and increase in intramuscular fat; although significant, effects on subsequent carcass quality of lambs were relatively small. These data suggest that the lambs adapted to changes in muscle fiber composition previously observed at 2 wk. However, lambs in this study were well fed during postnatal growth. Whether offspring would still have been able to compensate if they had received poor nutrition postnatally and whether that failure to compensate would have influenced carcass composition remain to be determined.

Influence of dietary oils and protein level on pork quality. 1. Effects on muscle fatty acid composition, carcass, meat and eating quality

This study evaluated the effects of three dietary oils – palm kernel (PKO), palm (PO) and soyabean (SBO) – and two protein levels – high (HP) and low (LP) in a 3 × 2 factorial design involving 60 pigs on growth performance, muscle fatty acid composition and content, carcass, meat and eating qualities. Oil type did not have a significant effect on growth and carcass quality. PKO significantly reduced the polyunsaturated (PUFA) to saturated (SFA) fatty acid (P:S) ratio in longissimus muscle ( P < 0.001). PKO increased the concentrations of lauric (12:0), myristic (14:0), palmitic (16:0) and stearic (18:0) fatty acids and decreased linoleic acid (18:2). The LP diet increased intramuscular fat (IMF) from 1.7 g/100 g muscle in HP to 2.9 g/100 g ( P < 0.001), increased tenderness by 0.6 units ( P < 0.01) and juiciness by 0.5 units ( P < 0.01) on the 1–8 scale, but at the expense of lower daily weight gain ( P < 0.01), lower feed conversion efficiency ( P < 0.01), reduced P:S ratio ( P < 0.001) and increased lipid oxidation ( P < 0.01). The results suggest that PKO and PO could be used in tropical developing countries as cheaper alternatives to SBO for the production of good quality and healthy pork, but their limits of inclusion need to be determined.

Variability in marbling in Angus steers and an evaluation of subjective marbling assessment

Currently there are no marbling grades within the New Zealand beef classification system, yet within some of our major markets (e.g., the United States and Japan) marbling is an important component of the grading system. This paper aims to examine the extent of marbling within Angus steers in New Zealand and relate these data to US and Japanese marbling grades. The amount of intramuscular fat (marbling) in the M. longissimus thoracis at the 12th rib site was estimated for samples from 259 Angus steers using NIRS. Carcass weight ranged from 220 to 540 kg and explained 66% of the variability in chemical fat. For carcasses in the 300 to 400 kg range, intramuscular fat content increased at average rate of 3.5 g kg−1 fresh weight of muscle for each 10 kg increase in carcass weight. Marbling was assessed in 118 ribeye steaks by 11 novice panellists using both the Japanese (JMGA) and United States (USDA) marbling grading standards and the scores obtained were compared against the predicted chemical fat content for each sample as estimated by NIR spectroscopy. Panellists assessed 8 to 13 steaks per session to determine between‐grader variability. Immediately after each session, steaks were re‐randomised and reassessed to determine within‐grader variability. There was sufficient between‐operator variability to indicate that graders should be trained or screened if carcasses are to be graded on the basis of marbling scores. The regression equations of mean panel scores on chemical fat content accounted for approximately 87% of the variation in panel means. Each unit increase in Japanese marbling score was equivalent to an increase in intramuscular fat content of 27 (±1.0) g kg−1. Each unit increase in USDA marbling score was associated with an increase in intramuscular fat of 30 (±1.1) g kg−1. Our results using novice graders differed substantially from earlier calibrations of intramuscular fat on marbling score using trained graders. The longissimus thoracis muscle of heavyweight Angus steers was estimated to contain intramuscular fat contents equivalent to JMGA marbling scores of up to 8 and USDA scores of 6, suggesting that New Zealand has cattle genotypes capable of producing well marbled beef.

Fattening heifers to heavy weights to enhance marbling: Efficiency of gain

Feedlot performance and carcass composition were measured in two studies to evaluate the use of common Canadian breeds and nutrition programs for production of highly marbled beef for the Japanese market. Weaned heifer calves (n = 221, initial weight 265 kg) of Angus, Hereford, and Hereford × Angus (HA) breeding were slaughtered at 500, 590, and 680 kg in exp. 1. In exp. 2, yearling heifers (n = 216, initial weight 395 kg, same breeds as exp. 1 but including Holstein) were slaughtered at 590 and 680 kg. Cattle were randomly assigned to either a high plane of nutrition (HP) until slaughter or a moderate plane of nutrition to 500 kg (exp. 1) or 550 kg (exp. 2), followed by a high plane to slaughter (MHP). Mean days on feed, percent carcass fat, and percent intramuscular fat in longissimus muscle were 347 d, 38.6%, and 8.50% in exp. 1, and 281 d, 37.5%, and 7.87%, respectively, in exp. 2. In exp. 1, Herefords produced the most economical gains but the fattest carcasses (P &lt; 0.05). In exp. 2, Holsteins had the most economical liveweight and lean carcass weight gains (P &lt; 0.05). The cost of a percentage increase in intramuscular fat was lowest for Angus in exp. 1 (P = 0.05), similar for the breeds in exp. 2 (P = 0.29), and not affected by slaughter weight group. HP cattle gained liveweight, carcass, lean carcass, and intramuscular fat more economically than did MHP cattle (P ≤ 0.0002). The rate of deposition of intramuscular fat did not appear to increase with maturity. Feeding cattle to extreme slaughter weights using conventional feedlot diets produced extremely fat carcasses but did not produce highly marbled beef. Key words: Beef cattle, carcass, growth, intramuscular fat, marbling