Pork belly quality variation and its association with fatness level.

Belly is a very popular pork cut composed of different layers of fat and muscle tissue. This work aims to investigate the effect of belly fatness on the morphological, mechanical (firmness) and compositional characteristics of fresh pork bellies and the distribution of the fat within the belly slice. A total of 182 bellies, selected to ensure variability of fatness, sexes and genotypes, were scanned by computed tomography (CT) to determine the fat content which, together with the genotype, led to the formation of 5 classes: F1 class below 26%, F2 class from 26% to 33.9%, and F3 class above 33.9% of fat content from common commercial crossbred pigs; F4 class with an average fatness of 47.3% from pure Duroc pigs; and last, F5 class with 62.6% average fat content from Iberian×Duroc pigs. The distribution of the fat in the central belly slice obtained by CT revealed important differences by region although the fat content was proportional to the overall fatness of the belly. Both belly weight and belly firmness increased with higher fatness. In bellies from common commercial pigs, an increase of SFA and MUFA and a decrease of PUFA as fatness increased was observed. This study highlights variations in belly characteristics among different fat classes, indicating considerable differences in the quality of bellies currently available in the market. This may influence producers and consumers acceptability such that fat content could be considered as a quality criterion to pre-classify bellies and better match the raw product with its final destination.

Effect of dietary supplementation with yeast cell wall extracts on performance and gut response in broiler chickens.

BACKGROUND: The dietary supplementation of yeast cell wall extracts (YCW) has been found to reduce pathogenic bacteria load, promote immunoglobulin production, prevent diseases by pro-inflammatory responses, and alter gut microbiota composition. This study evaluated growth and slaughter results, health, gut morphology, immune status and gut transcriptome of 576 male chickens fed two diets, i.e. C (control) or Y (with 250-500 g/t of YCW fractions according to the growth period). At 21 and 42 d the jejunum of 12 chickens per diet were sampled and stained with hematoxylin/eosin for morphometric evaluation, with Alcian-PAS for goblet cells, and antibodies against CD3+ intraepithelial T-cells and CD45+ intraepithelial leukocytes. The jejunum sampled at 42 d were also used for whole-transcriptome profiling. RESULTS: Dietary YCW supplementation did not affect final live weight, whereas it decreased feed intake (114 to 111 g/d; P ≤ 0.10) and improved feed conversion (1.74 to 1.70; P ≤ 0.01). Regarding the gut, YCW supplementation tended to increase villi height (P = 0.07); it also increased the number of goblet cells and reduced the density of CD45+ cells compared to diet C (P < 0.001). In the gut transcriptome, four genes were expressed more in broilers fed diet Y compared to diet C, i.e. cytochrome P450, family 2, subfamily C, polypeptide 23b (CYP2C23B), tetratricopeptide repeat domain 9 (TTC9), basic helix-loop-helix family member e41 (BHLHE41), and the metalloreductase STEAP4. Only one gene set (HES_PATHWAY) was significantly enriched among the transcripts more expressed in broilers fed diet Y. However, a total of 41 gene sets were significantly over-represented among genes up-regulated in control broilers. Notably, several enriched gene sets are implicated in immune functions and related to NF-κB signaling, apoptosis, and interferon signals. CONCLUSIONS: The dietary YCW supplementation improved broiler growth performance, increased gut glycoconjugate secretion and reduced the inflammatory status together with differences in the gut transcriptome, which can be considered useful to improve animal welfare and health under the challenging conditions of intensive rearing systems in broiler chickens.

Effect of breast myopathies on quality and microbial shelf life of broiler meat.

To evaluate the impact of emerging myopathies on meat quality and microbial shelf life, 48 normal, 48 white striped (WS), and 48 wooden breasts (WB) were stored for 11 d at 4°C aerobically and analyzed at 24, 72, 120, 168, 216, and 264 h post-mortem. Normal breasts showed lower (P < 0.001) redness index (-0.88 vs. -0.41 and -0.43) and cooking losses (22.0 vs. 23.8 vs. 26.9%) than those of WS and WB meat. Normal and WS breasts exhibited higher protein content than that in WB meat (23.9 and 23.2 vs. 21.4%; P < 0.001). Normal meat also had a lower ether extract content than that in WB meat (1.09 vs. 1.88%; P < 0.001), with intermediate values for WS meat. Normal breasts exhibited higher saturated fatty acid (FA) rate (31.3 vs. 28.0% of total FA on average) and lower unsaturated FA rate (68.7 vs. 72.0%) than those in WS and WB meat (P < 0.001). Differences were mainly due to polyunsaturated FA (30.5% in normal vs. 35.3 and 35.4% in WS and WB meat; P < 0.001). Normal breasts had higher initial total viable count (TVC) and a shorter TVC lag phase than those of WS and WB meat (46.3 vs. 85.2 and 77.8 h). The microbial shelf life threshold (7 log10 CFU TVC/g) was achieved first in normal (130 h) and then in WS (149 h) and WB (192 h) meat. TVC and Pseudomonas spp. counts were significantly higher in normal than those in the affected breasts between 72 and 216 h of storage. Enterobacteriaceae spp. and lactic acid bacteria counts were significantly higher in normal meat, lower in WB meat, and intermediate in WS meat until 216 h. All differences in microbial targets across meat types disappeared by 264 h of storage. Further studies are necessary to elucidate the factors and the mechanisms that may modulate microbial growth and composition during storage in broiler breast meat affected by myopathies.

Predicting the carcass chemical composition and describing its growth in live pigs of different sexes using computed tomographys.

The aims of this study were (1) to evaluate the ability of computed tomography (CT) to predict the chemical composition of live pigs and carcasses, (2) to compare the chemical composition of four different sex types at a commercial slaughter weight and (3) to model and evaluate the chemical component growth of these sex types. A total of 92 pigs (24 entire males (EM), 24 surgically castrated males (CM), 20 immunocastrated males (IM) and 24 females (FE)) was used. A total of 48 pigs (12 per sex type) were scanned repeatedly in vivo using CT at 30, 70, 100 and 120 kg and slaughtered at the end of the experiment. The remaining 44 were CT scanned in vivo and slaughtered immediately: 12 pigs (4 EM, 4 CM and 4 FE) at 30 kg and 16 pigs each at 70 kg and 100 kg (4 per sex type). The left carcasses were CT scanned, and the right carcasses were minced and analysed for protein, fat, moisture, ash, Ca and P content. Prediction equations for the chemical composition were developed using Partial Least Square regression. Allometric growth equations for the chemical components were modelled. By using live animal and carcass CT images, accurate prediction equations were obtained for the fat (with a root mean square error of prediction (RMSEPCV) of 1.31 and 1.34, respectively, and R 2=0.91 for both cases) and moisture relative content (g/100 g) (RMSEPCV=1.19 and 1.38 and R 2=0.94 and 0.93, respectively) and were less accurate for the protein (RMSEPCV=0.65 and 0.67 and R 2=0.54 and 0.63, respectively) and mineral content (RMSEPCV from 0.28 to 1.83 and R 2 from 0.09 to 0.62). Better equations were developed for the absolute amounts of protein, fat, moisture and ash (kg) (RMSEPCV from 0.26 to 1.14 and R 2 from 0.91 to 0.99) as well as Ca and P (g) (RMSEPCV=144 and 71, and R 2=0.76 to 0.66, respectively). At 120 kg, CM had a higher fat and lower moisture content than EM. For protein, CM and IM had lower values than FE and EM. The ash content was higher in EM and IM than in FE and CM, while IM had a higher Ca and P content than the others. The castrated animals showed a higher allometric coefficient for fat and a lower one for moisture, with IM having intermediate values. However, for the Ca and P models, IM presented higher coefficients than EM and FE, and CM were intermediate.

Divergent selection for intramuscular fat content in rabbits. II. Correlated responses on carcass and meat quality traits.

Correlated responses on carcass and meat quality characteristics after 3 generations of divergent selection for intramuscular fat (IMF) content were assessed by comparing the high and low lines. Selection was based on the phenotypic value of IMF content of LM, measured in 2 full sibs of the first parity. Traits measured were: BW, HCW, commercial carcass weight (CCW), reference carcass weight (RCW), scapular (SF) and perirenal fat (PF) content, meat-to-bone ratio (M:B) of the hind leg, pH of LM, color (lightness, L*; redness, a*; and yellowness, b*) of the carcass and of a LM section, protein content, and fatty acid (FA) composition of LM. A total of 174 records was used to estimate the correlated selection response. Data were analyzed using Bayesian methodology. We considered one-third of the phenotypic SD of a trait as a relevant value for the difference between lines. Then, the probability of the difference being greater than a relevant value (PR) was calculated. A low PR implies that the lines compared are similar. Carcass weights (PR between 0.24 and 0.31) and M:B of the hind leg (PR = 0.15) were not modified by selection for IMF content. There was a slight negative correlated response for BW, although evidence of its relevance was low (PR = 0.48). Scapular fat content was similar between lines (PR = 0.03). There were differences for PF content, although there was low evidence for showing its relevance (PR = 0.47). Color traits of the carcass were not affected by selection (PR between 0.04 and 0.30). In muscle, L* was also similar between lines (PR = 0.26). There were differences for a* and b*, although there was little evidence of their relevance (PR = 0.35 and 0.40, respectively). There was a positive correlated response on muscle pH and differences could be relevant (PR = 0.77). Protein content of LM was similar between lines (PR = 0.13), whereas FA composition was affected by selection. There were relevant differences between lines for MUFA (PR = 0.99), n-3 (PR = 0.95), and n-6 (PR = 0.98) percentages. For individual FA, differences were relevant for C18:1n-9 (PR = 0.97) and C20:5 n-3 (PR = 0.98). In conclusion, selection for IMF content may modify carcass quality by increasing PF content. Moreover, it led to some modifications in pH and FA composition of LM.

Divergent selection for intramuscular fat content in rabbits. I. Direct response to selection.

The aim of this study was to evaluate the selection response on intramuscular fat (IMF) content of LM after 3 generations of divergent selection. Heritability and genetic means for IMF content were also analyzed. Selection was based on the phenotypic value of IMF content measured in 2 full sibs of the first parity. Selection pressure on females was 13% in the base generation and 26% for the next generations. Males were selected within sire families to reduce inbreeding. Line size was 13 males and 83 females in the base population and approximately 8 males and 40 females for high (High) and low (Low)lines in the next generations. A total of 668 records were used to estimate the selection response on IMF. The pedigree file used to estimate heritability and genetic means contained 1,332 animals. Data were analyzed using Bayesian methodology. Differences between lines for IMF were 0.08, 0.10, and 0.09 g/100 g muscle in the first, second, and third generation, respectively. These differences represent a direct and cumulative selection response of 9% of the mean, of which 6.8% was obtained in the first generation. Heritability of IMF content was moderate to high (0.37) with a probability of 97% of being greater than 0.20. The response to selection estimated using an animal model was 0.033, 0.052 and 0.054 g/100 g muscle in line High and -0.032, -0.046, and -0.051 g/100 g muscle in line Low in the first, second, and third generation, respectively. Results of the present experiment confirmed that IMF content can be improved through selection in rabbits.

Application of NIRS for predicting fatty acids in intramuscular fat of rabbit.

The aim of this study was to evaluate the use of near infrared reflectance spectroscopy (NIRS) for predicting fatty acid content in intramuscular fat to be applied in rabbit selection programs. One hundred and forty three freeze-dried Longissimus muscles (LM) were scanned by NIRS (1100-2498nm). Modified Partial Least Squares models were obtained. Equations were selected according to standard error of cross validation (SECV) and coefficient of determination of cross validation (R(2)(CV)). Residual predictive deviation of cross validation (RPD(CV)) was also studied. Accurate predictions were reported for IMF (R(2)(CV)=0.98; RPD(CV)=7.57), saturated (R(2)(CV)=0.96; RPD(CV)=5.08) and monounsaturated FA content (R(2)(CV)=0.98; RPD(CV)=6.68). Lower accuracy was obtained for polyunsaturated FA content (R(2)(CV)=0.83; RPD(CV)=2.40). Several individual FA were accurately predicted such as C14:0, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1 n-9, C18:2 n-6 and C18:3 n-3 (R(2)(CV)=0.91-0.97; RPD(CV)>3). Long chain polyunsaturated FA and C18:1 n-7 presented less accurate prediction equations (R(2)(CV)=0.12-0.82; RPD(CV)<3).

Influence of genetic line on lipid metabolism traits of rabbit muscle.

The effects of genetic line on intramuscular fat content, perirenal fat content, and activity of some enzymes involved in lipid metabolism were studied. One hundred twenty animals from 3 synthetic lines, A and V selected for litter size at weaning and R selected for growth rate between weaning and slaughter, were used in this experiment. One-half of the rabbits were slaughtered at 9 or 13 wk of age, and perirenal fat content (PF) and 2 muscles, LM and semimembranosus proprius (SP), were studied. Semimembranosus proprius muscle showed greater lipogenic [glucose-6-phosphate dehydrogenase (G6PDH) and fatty acid synthase (FAS)] and oxidative enzyme activities [ß-hydroxyacyl-CoA dehydrogenase (HAD) and citrate synthase (CS)] compared with LM. Longissimus muscle had less lipogenic and more glycolytic activity (lactate dehydrogenase (LDH)] than SP. Enzymatic activity and lipid content were affected by age. Lipogenic and glycolytic enzyme activity increased from 9 to 13 wk of age in SP muscle. In LM, lipogenic activity remained stable, but glycolytic activity increased and lipolytic and oxidative activity decreased with age. Genetic line had an influence on lipogenic, lipolytic, and oxidative enzyme activities, which was related to differences in muscle lipid content (IMF). Line A showed greater lipogenic (G6PDH and malic enzyme) and lipolytic activity (neutral lipase), which was associated with a greater IMF in this line. In SP muscle, line R showed a greater HAD activity than lines A and V, and CS activity was greater in lines R and A than in line V. In LM, no differences between lines were found for oxidative enzymes. The relationship between IMF and PF was different between lines, with lines A and V showing positive correlation values (r = 0.56 and r = 0.70, respectively) and line R no relationship between both traits (r = 0.06). Results from this study showed that lipogenic and oxidative enzyme activity are related to muscle lipid deposition. Genetic line had an effect on metabolic enzyme activity and, consequently, on IMF deposition.