Differences In Carcass Composition Research Articles

Differences in carcass composition and meat quality of conventional and slow-growing broiler chickens raised at 2 stocking densities

The fast growth rate of broiler chickens is a welfare concern that has increased consumer interest in chicken from slower growing (SG) broilers. Replacing conventional (CONV) broilers with SG broilers will reduce chicken supply and SG broilers require different management practices than CONV. This study evaluated the effects of 2 stocking densities on the carcass composition and meat quality of CONV broilers that reach market weight at 42 d and SG broilers that reach market weight at 63 d. Male broilers from each strain were exclusively stocked into 16 pens at a density of either 29 kg/m2 or 37 kg/m2. Live body, carcass without giblets (WOG), and part weights were recorded and used to calculate yield. Initial and 24-hour pH, color (L*, a*, and b*), cooking loss, and Warner Bratzler shear force of the breast and thigh muscles were measured. Birds from both strains reached similar live body and carcass WOG weights. CONV had 3.4%, 13.0%, and 2.8% greater (P ≤ 0.002), carcass WOG, breast, and tenderloin yields, while SG had 2.7%, 5.0%, 7.5%, and 1.2% greater (P < 0.0001) wings, leg quarters, frame, and skin yields, respectively. CONV breast 24-h pH and cooking loss were greater (P ≤ 0.04) than SG. While SG thigh shear force was greater than CONV (P = 0.008), breast shear force was the lowest for CONV stocked at 29 kg/m2 and the greatest for SG stocked at 37 kg/m2 (P = 0.04). SG had a paler breast than CONV, while CONV had a yellower breast than SG (P < 0.0001). While SG had a redder thigh than CONV (P = 0.002), SG stocked at 29 kg/m2 had a redder breast than SG stocked at 37 kg/m2, with both CONV groups intermediate (P = 0.04). These results indicate that differences in male broiler meat quality were affected more by strain than by stocking density. Compared with CONV, SG broiler meat quality was more affected by stocking density in this study.

Optimal Replacement of Soybean Meal with Fermented Palm Kernel Meal as Protein Source in a Fish Meal-Soybean Meal-Based Diet of Sex Reversed Red Tilapia (Oreochromis niloticus × O. mossambicus).

Simple SummaryReplacement effects of soybean meal (SBM) with fermented palm kernel meal (FPKM) as a protein source was investigated in sex-reversed red tilapia. The two-month-old fish were fed fish meal-SBM-based diets with replacement by FPKM at 25% (25FPKM), 50% (50FPKM), 75% (75FPKM) and 100% (100FPKM) for 12 weeks, while an FPKM-free diet (0FPKM) was used as a control. Based on growth performance, feed utilization, digestive enzyme activities, flesh quality, carcass composition, hematological parameters and liver histoarchitecture, the 50% replacement level of SBM by FPKM support this alternative. Findings from the current study support the use of FPKM in aquafeed production, providing a low-cost diet for tilapia farming.The solid-state fermentation by effective microorganisms (containing photosynthetic bacteria, lactic acid bacteria, nitrogen-fixing bacteria, yeast and Bacillus sp.) improved the nutritive values of palm kernel meal (PKM). Increased crude protein (20.79%), nitrogen-free extract (40.07%) and gross energy (19.58%) were observed in fermented PKM (FPKM) relative to raw PKM while crude lipid (15.65%), crude fiber (36.45%) and ash (29.54%) were decreased. Replacement of soybean meal (SBM) with FPKM as a protein source was investigated for its effects in sex-reversed red tilapia (Oreochromis niloticus × O. mossambicus). The two-month-old fish (14.85 ± 0.28 g initial weight) were fed fish meal-SBM-based diets with replacement by FPKM at 25% (25FPKM), 50% (50FPKM), 75% (75FPKM) and 100% (100FPKM), while an FPKM-free diet (0FPKM) was used as a control. The five treatments, comprising triplicate cement ponds and forty fish each, were conducted in a recirculating system over 12 weeks. At the end of the feeding trial, fish fed the 50FPKM diet were superior in growth performance, while the feed utilization parameters were similar across all five treatments. Physiological adaptation of the protein-digesting (pepsin and trypsin) and lipid-digesting (lipase) enzymes was detected at all protein replacement levels (except for 25FPKM), as well as of the enzyme for cellulose digestion (cellulase), but not of the carbohydrate-digesting enzymes (amylase). Protein synthesis capacity in flesh was improved in fish fed the 50FPKM diet, while the quality of the main flesh proteins, actin and myosin, showed no significant differences across the five treatments. No differences in carcass composition and no negative effects on hematological parameters or liver histoarchitecture at the 50% replacement level of SBM by FPKM also support this alternative. Findings from the current study indicate the low-cost FPKM-containing diet for tilapia in comparison with control diet.

The effect of feed restriction, sex and age on the carcass composition and meat quality of nutrias (Myocastor coypus)

The objective of the study was to evaluate the effect of quantitative feed restriction on the carcass composition and physical, chemical, histochemical and sensory properties of meat from male and female nutria at the end of the feed restriction and fattening period. In the experiment, from two to eight months of age, males and females were divided into two groups: one group was fed ad libitum throughout the experiment, and the second group was restricted to two weeks (from 11 to 12 weeks of age). The restricted nutrias received 75% ad libitum feeding. The significant interaction among feed restriction, sex and age was revealed only in the cross-sectional area of all muscle fiber types. Age was the main factor affecting carcass composition and meat quality characteristics. Sex-related differences in carcass composition and some sensory attributes and feed restriction-related differences in carcass composition were observed.

Slaughter Characteristics of Feedlot-Finished Premium South African Lamb: Effects of Sex and Breed Type.

This study compared the carcass characteristics of ram and ewe lambs from South African wool, dual-purpose, meat, and fat-tailed sheep types, reared to produce premium lamb carcasses. The lambs were reared on a feedlot diet (10.41 MJ ME/kg feed and 19.06% crude protein) from weaning (30 kg live weight) until they attained a back-fat depth of ~4 mm, measured using ultrasound. After slaughter, the carcasses were assessed for retail cut yields, composition, and physical meat quality. Later, maturing lambs attained heavier carcass weights than early maturing breeds (~20.7 kg vs. 16.9 kg, respectively; p ≤ 0.05), and differences in carcass composition and retail cut yields were ascribed to differences in the frame size and pattern of fat deposition of the respective breeds. Small differences in physical meat quality were observed, with meat from Dormer and Namaqua lambs having notably higher shear-force values (~46 N) than that from Meatmaster carcasses (~34 N). These differences though are expected to have little influence on the perceived quality of the meat.

Age-related changes in the carcass composition and meat quality of fallow deer (DAMA DAMA L.)

The present study investigated the possible differences in carcass composition as well as texture, structure and percentage of different muscle types of the most valuable muscles (BF – biceps femoris, SM – semimembranosus, and L – longissimus) from fallow deer (Dama dama L.) bucks shot in the forest farm in north-western Poland at four different ages: 18, 30, 42 and 54 months. It was found that carcasses of young fallow deer (18–30 months), compared to older animals, were characterised by a higher dressing proportion, a higher percentage of the most valuable commercial cuts (the saddle, haunch and shoulder), high meat yield with the lowest percentage of bones and a lower percentage of skin and head. Their muscles, compared with older animals, were characterised by a lower percentage of red fibres, lower muscle fibre area, thinner perimysium and endomysium, lower amount of intramuscular fat and as a consequence lower hardness, springiness, cohesiveness, as well as a higher pH and lower thermal drip.

Differences in carcass composition of males and females of two turkeys hybrids

DOI: 10.15414/afz.2014.17.03.72–74 Received 7. May 2014 ǀ Accepted 27. May 2014 ǀ Available online 27. August 2014 The objective of this study was to evaluate the effect of hybrid and sex on carcass composition in turkeys. A total of 240 turkeys (males and females) of two different hybrids (BUT Big 6 and Converter) were used in experiment. Birds were housed in housing conditions suitable for turkeys. Turkeys were fed ad libitum with commercial feed mixture for given category of turkeys. Six males and six females of each genotype were slaughtered at 17 th weeks of age. Live weight and carcass composition were determined. The significant interactions between hybrid and sex were detected in live weight (P≤0.001), carcass weight (P≤0.001) and liver percentage (P≤0.006). The highest live weight and carcass weight was observed in Converter males (17410 g, 13360 g, respectively), while the lowest was detected in Converter females (12115 g, 9390 g, respectively). Converter females had the highest liver share (1.47%), whereas the lowest liver share was noted in BUT Big 6 females (1.20%). The significant effect of hybrid was found in live weight, carcass weight and thigh percentage. The significantly higher live weight (P≤0.003), carcass weight (P≤0.002) and share of thigh (P≤0.010) was detected in BUT Big 6 compare to Converter. Males had significantly higher (P≤0.001) live weight, carcass weight and share of thigh than females. Keywords: turkeys, hybrids, sex, carcass traits

Comparisons of carcass and meat quality among rabbit breeds of different sizes, and hybrid rabbits

The aim of the present study was to evaluate the differences in carcass composition, meat quality characteristics, and muscle fibre characteristics among rabbits of different sizes and of different breeds. The present study was performed using 96 rabbits (12 rabbits per group) at the age of 90 days, including seven pure breeds and one commercial hybrid. The included rabbit breeds were as follows: the giant breed Moravian Blue (MB); the medium breeds Czech White (CW), Czech Spotted (CS), Czech Solver (CSo), and Moravian White of Brown Eye (MW); the small breeds Czech Black Guard Hair (CB) and Czech Gold (CG); and the hybrid Hyplus rabbits (PS 19×PS 39). The slaughter weights were significantly (P<0.001) affected by the breed. Comparisons of the dressing out percentage showed significant differences (P<0.001) among groups, and the lowest dressing out percentage was observed in the small breed CB (56.7%). The lowest values for the hind part percentage, hind leg percentage and hind leg meat percentage were in the medium breed CS (50.1%, 28.2% and 21.6% respectively). The results of the loin chemical composition assay revealed differences among the groups in crude protein (P<0.001), fat (P<0.001) and cholesterol (P<0.05) contents and in the hind leg meat differences in crude protein (P<0.001) and fat contents (P<0.05). The highest (P<0.05) loin cholesterol contents (53.4mg/100g), hind leg fat (3.59%) values were observed in the medium breed CS, which corresponded with the highest perirenal fat content (2.98%). For both types of muscle fibres (βR and αW), the smallest (P<0.001) cross-sectional areas, diameters and perimeters were found in Hyplus rabbits. Good results of CW rabbits in carcass composition show that this breed might be used for commercial production.

Carcass composition of Namaqua Afrikaner, Dorper and SA Mutton Merino ram lambs reared under extensive conditions

This study evaluated the differences in the muscle-fat-bone yield of Namaqua Afrikaner (NA), Dorper (D) and SA Mutton Merino (SAMM) ram lambs. The breeds constituted an indigenous, hardy and late maturing, fat-tailed breed (NA), an early maturing, commercial meat breed (D) and a late maturing commercial dual-purpose breed (SAMM). Lambs were slaughtered at 35 (± 8) days post weaning. Carcasses were cooled for 24 h, separated into retail cuts (leg, loin, rib, and shoulder), weighed and deboned. Meat and fat were separated after deboning and weighed to calculate the muscle-fat-bone yield per cut. Least-square means were computed for the respective breeds, using slaughter age as covariate. Results for percentage meat indicate that, with exception of the rib, retail cuts from the NA breed contained a lower percentage of meat than D and SAMM breeds, particularly in the valuable loin and leg cuts. The shoulder of the NA had a lower percentage meat than that of the D. The percentage fat in retail cuts did not differ between breeds for any of the cuts. In comparison with both D and SAMM, NA contained a higher percentage bone in all cuts. Dorper and SAMM carcasses did not differ in terms of the percentage of bone, fat or muscle for any of the retail cuts. The lower meat yield, particularly in the more expensive loin and leg of the NA, when compared to the commercial meat breed (D) could make the former less preferred for meat production. However, the NA compared more favourably than the dual-purpose SAMM. Differences in carcass composition could be attributed to the fact that the NA is an unimproved and late maturing sheep breed.

Effect of dietary protein level on carcass traits and meat properties of Cinta Senese pigs

The aim of this study was to test the effect of various dietary protein contents (CP) on the carcass traits and the meat quality of Cinta Senese pigs. A total of 60 Cinta Senese pigs were equally distributed in four dietary groups that were balanced for sex (barrows and gilts) and live weight. The animals in the groups were fed one of four diets (80CP, 100CP, 130CP and 160CP) containing different CP contents (80, 100, 130 and 160 g/kg, respectively). The diets were administered to the pigs during the entire growing–fattening period in a controlled dose of 90 g/kg W0.75, to a maximum of 2.5 kg/day per animal. The duration of the trial was ~250 days, ending when the animals reached the target slaughter weight of 145 kg. The 80CP diet produced fatter carcasses than did the other diets; no differences in carcass composition were found among the animals fed the other three diets (total lean cuts: 57.4%, 61.4%, 60.8% and 61.3% for 80CP, 100CP, 130CP and 160CP diet, respectively). The sample joint composition confirmed the highest fatness and the lowest meatiness of pigs fed 80CP. This same pattern was evident for the composition of the muscle (Longissimus lumborum) containing the largest amount of i.m. fat, and the lowest protein content in the 80CP group. Moreover, the 80CP diet resulted in the lightest and yellowest meat with the highest cooking loss. A principal component analysis of the physical and chemical traits of the meat revealed three first factors that explained 56% of the total variance. Among them, only the intersection of Factor1, which combined mainly lower pH at 24 h postmortem and higher drip loss, cooking loss, lightness and yellowness, with Factor2, which associated higher toughness, higher protein and lower fat content, graphically appeared to discriminate the 80CP diet from the other ones. In conclusion, a diet with 80 g/kg of CP content was inadequate for this local breed, while, in consideration of the cost of protein feed and the need to reduce N pollution, the 100CP diet would be an optimal compromise for the growth–fattening of Cinta Senese pigs.

SKLAD TUSZKI I JAKOSC MIESA KUROPATWY SZAREJ (PERDIX PERDIX L.)

The aim of the study was to determine the body weight, dressing percentage, carcass composition and physico-chemical and sensory properties of meat from grey partridge (Perdix perdix L.). At the age of 32 weeks, male and female grey partridge had similar body weight (301.4 g vs 299.5 g), carcass weight (218.2 g vs 216.0 g) and dressing percentage (72.4% vs 72.1%). Dissection analysis showed non- significant differences in carcass composition between males and females. The carcasses of males contained more leg muscles (17.4%), skin with subcutaneous fat (5.5%) and neck (3.4%), but less breast muscles (30.7%) and wings (8.8%) compared to the carcasses of females (17.0%, 5.3%, 3.3%, 31.1% and 10.7%, respectively). Compared to males, the breast muscles of females were characterized by significantly higher water holding capacity. In addition, females showed significantly (P 0.05) lower values of lightness (L*), yellowness (b*) and tenderness of breast muscles compared to males.

Is ability to hepatic steatosis influenced by age at the beginning of the overfeeding period in Muscovy and Pekin ducks?

The aim of this study was to analyse the effects of species (Muscovy and Pekin ducks) and age at the beginning of the overfeeding period on fatty liver production, carcass composition and lipid and moisture content of the liver and breast muscle. We reared four groups of 40 ducks per species for the study, starting at 2-week intervals in order to have four different ages together at the beginning of the overfeeding period (10, 12, 14 and 16 weeks). At the end of the overfeeding period, all ducks were slaughtered. Our results confirmed the high levels of difference in carcass composition and lipid content in the plasma, liver and breast muscle between Muscovy and Pekin ducks at all ages. Pekin ducks were not able to develop a high degree of hepatic steatosis, but had increased lipid storage in peripheral adipose and muscle tissues than Muscovy ducks. However, the fatty liver weight of Pekin ducks increased with age, with lipid deposition in the liver and peripheral tissues. The ability of Muscovy ducks to produce fatty livers remained unchanged with age in line, with lipid deposition in the liver and peripheral tissues. The sites of lipid deposition thus depend on species and not on the physiological maturity of ducks.

Effects of ad libitum and restricted feeding on early production performance and body composition of Yorkshire pigs selected for reduced residual feed intake

Residual feed intake (RFI), defined as the difference between observed and expected feed intake based on growth and backfat, has been used to investigate genetic variation in feed efficiency in cattle, poultry and pigs. However, little is known about the biological basis of differences in RFI in pigs. To this end, the objective of this study was to evaluate the fifth generation of a line of pigs selected for reduced RFI against a randomly selected Control line for performance, carcass and chemical carcass composition and overall efficiency. Here, emphasis was on the early grower phase. A total of 100 barrows, 50 from each line, were paired by age and weight (22.6 ± 3.9 kg) and randomly assigned to one of four feeding treatments in 11 replicates: ad libitum (Ad), 75% of Ad (Ad75), 55% of Ad (Ad55) and weight stasis (WS), which involved weekly adjustments in intake to keep body weight (BW) constant for each pig. Pigs were individually penned (group housing was used for selection) and were on treatment for 6 weeks. Initial BW did not significantly differ between the lines (P > 0.17). Under Ad feeding, the low RFI pigs consumed 8% less feed compared with Control line pigs (P < 0.06), had less carcass fat (P < 0.05), but with no significant difference in growth rate (P > 0.85). Under restricted feeding, low RFI pigs under the Ad75 treatment had a greater rate of gain while consuming the same amount of feed as Control pigs. Despite the greater gain, no significant line differences in carcass composition or carcass traits were observed. For the WS treatment, low RFI pigs had similar BW (P > 0.37) with no significant difference in feed consumption (P > 0.32). Overall, selection for reduced RFI has decreased feed intake, with limited differences in growth rate but reduced carcass fat, as seen under Ad feeding. Collectively, results indicate that the effects of selection for low RFI are evident during the early grower stage, which allows for greater savings to the producer.

Influence of housing type and age in female pigs. 2. Effects on biochemical indicators of fat metabolism and the fatty acid profile of belly fat and back fat depots

Weaning pigs into deep-litter (D) housing systems and then moving them into conventional (C) housing facilities affects the growth paths of the pigs and can result in differences in carcass composition which may be explained by altered fat metabolism. To examine this proposition experimentally, 160 female Large White × Landrace pigs were obtained at 3 weeks of age, average liveweight 5.5 ± 0.08 kg and were stratified by weight to four treatments. The treatments consisted of two housing treatments, C or D, across two growth periods: (i) early (3–13 weeks of age); and (ii) late (13–24 weeks of age). At ~13 weeks of age eight pigs per experimental treatment (n = 32) were slaughtered and the remaining pigs (n = 128) moved to new pens where they were housed until slaughter at ~24 weeks of age. To 13 weeks of age, the effect of housing type on lipogenesis did not reach significance (P &gt; 0.05). At 24 weeks of age there were some treatment differences in fatty acid profile (P ≤ 0.05) and the concentration of plasma glycerol (P = 0.002) and non-esterified fatty acids (P = 0.019). There were trends for lipogenic enzyme activity to differ between treatments also (P &lt; 0.100). Results suggested fat deposition was lower in D-finished pigs compared with C-finished pigs, rejecting the hypothesis that D-finished pigs would be fatter. However, most of the differences in the biochemical measurements were explained by the significant reduction in growth that occurred when pigs changed housing environments, rather than as an effect of the housing environment itself. Indicators of lipogenesis suggested that lipogenic rate was lowest in pigs moved from C to D housing compared with other treatment groups that had remained within the same housing, C or D, throughout the experiment or had moved from D housing to C housing at 13 weeks of age.

The response of various muscle types to a restriction–re-alimentation feeding strategy in growing pigs

Muscle lipid concentration is known to influence pork eating quality. This study aimed at evaluating the effect of a restriction–re-alimentation feeding strategy on intramuscular fat deposition in pigs. A total of 70 Duroc × (Large White × Landrace) pigs (castrated males and females) were used. Ten pigs were first slaughtered at 30 kg live weight (LW) to determine initial body and muscle composition. From 30 to 80 kg LW (growing period), pigs were either fed ad libitum (AL) or restricted to 70% of the ad libitum intake of AL pigs (RA). From 80 to 110 kg LW (finishing period), both AL and RA pigs were fed ad libitum. In each group, pigs were slaughtered at 80 kg (n = 10) and at 110 kg (n = 20) LW. During the growing period, the growth rate of RA pigs was reduced by 30% (P < 0.001) compared with AL pigs. During the finishing period, RA pigs had a 7% (P = 0.09) higher growth rate than AL pigs due to compensatory feed intake (+14%). Plasma insulin-like growth factor-1 concentration was lower in RA pigs at 80 kg LW, but markedly increased after re-alimentation up to the level observed in AL pigs (P < 0.001). At 80 kg, the leaner carcasses of RA pigs resulted from a more pronounced reduction in fat than in lean tissue deposition rates. Re-alimentation of RA pigs increased fat tissue deposition (+160% for females, P < 0.01) but not lean deposition in the carcass, leading to limited differences in carcass composition between RA and AL pigs at 110 kg LW. Regarding tissue deposition rates, the response to feeding strategy differs between muscles. In the m. biceps femoris (BF), restriction affected lipid (−50%, P < 0.001) and protein (−25%, P < 0.001) deposition, whereas re-alimentation increased lipid (+62%, P < 0.05) but not protein deposition rates. At market weight, the extent of the difference in BF lipid concentration between RA and AL pigs was strongly reduced, but still significant. By contrast, in the m. longissimus, restriction decreased protein but not lipid deposition, whereas neither of them was modified during re-alimentation. Therefore, an increased muscle lipid concentration at 110 kg LW could not be reached in RA pigs. Modifications of onset and/or duration of restriction and re-alimentation periods should be tested to optimise effects on muscle lipid deposition and thereby achieve improved pork quality.

Diet-Induced Thermogenesis and Glucose Oxidation in Broiler Chickens: Influence of Genotype and Diet Composition

The main objectives of this study were to explore the role of diet-induced thermogenesis in the regulation of voluntary feed intake and to determine the glucose oxidation of broiler chicken strains, known to differ in glucose-insulin balance. From 2 to 7 wk of age, male broiler chickens of a fat and a lean line were reared on 1 of 2 isoenergetic diets with constant gross energy and carbohydrate levels but with substitutions between fat and protein. The low protein (LP/HF) diet contained 126 g of protein/kg and 106 g of fat/kg, whereas the low fat (LF/HP) diet contained 242 g of protein/kg and 43 g of fat/kg. There was no significant effect of the genetic background of the broilers on the glucose oxidation rate (as measured by stable isotope breath test) or protein oxidation (as measured by plasma uric acid levels). Considering the difference in carcass composition (fat content) of both lines, this leads to the hypothesis that the lines differ predominantly in fat metabolism. Although there was no line effect on plasma triglyceride and free fatty acid concentrations, it was hypothesized that there might be differences in fat oxidation or de novo lipogenesis, or both, between the genotypes. Diet-induced thermogenesis per metabolic body weight (kg of BW0.75) per 24 h, expressed per gram of feed intake, was not significantly influenced by genetic background or by diet composition. Therefore, a model linking feed intake to diet-induced thermogenesis, as postulated for adult mammals, could not be corroborated for growing broiler chickens.

Feedlot cattle diets based on barley or corn supplemented with dry corn gluten feed evaluated using the NRC and CNCPS beef models

A study was conducted to evaluate the effects of supplementing feedlot finishing corn diets with dry corn gluten feed (CGF). Animal performance and carcass traits were compared with those obtained by feeding a barley-based diet typical of diets fed commercially in western Canadian feedlots. The second objective of the experiment was to evaluate the diets using the 1996 National Research Council (NRC) Beef (level 1 and 2) and Cornell Net Carbohydrate and Protein System (CNCPS, version 5.0) models to determine how well the models predict animal response. Crossbred beef steers (248) weighing 423 ± 20.5 kg were allocated to 24 pens and then six pens were assigned to each of four diets: (1) barley grain (13.8% crude protein, CP), (2) corn grain (9.2% CP), (3) corn grain supplemented with a low level (7%, DM basis) of CGF (CGF-low, 9.7% CP), and (4) corn grain supplemented with a high level (23%) of CGF (CGF-high, 11.7% CP). The barley grain was steam-rolled and the corn grain was dry-rolled. All diets contained 8% barley silage (DM basis). The cattle were adapted from a backgrounding diet to the experimental diets over a period of 28 d and then fed for a period of 136 d. During the adaptation phase cattle fed unsupplemented corn grew slower (P &lt; 0.05) than the cattle fed the other diets (1.23 vs. 1.52 kg d-1). However, after day 42 of the study, cattle fed unsupplemented corn grew very rapidly such that gain for the entire feeding period was similar for cattle fed unsupplemented corn and barley diets (1.62 vs. 1.58, P &gt; 0.05). Furthermore, growth rate was higher (P &lt; 0.05) for cattle fed barley or unsupplemented corn than for cattle fed low or high levels of CGF (1.48 and 1.45 kg d-1, respectively). The dry matter intake (DMI) averaged 11.4 kg d-1 during the feeding period and was not affected (P &gt; 0.05) by diet. Feed:gain ratio (kg DM:kg gain) was similar (P &gt; 0.05) for cattle fed barley (7.09) and unsupplemented corn (7.38), but was higher (P &lt; 0.05) for cattle fed CGF-high (7.92), and intermediate (P &gt; 0.05) for those fed CGF-low (7.52). There were no differences in carcass composition between barley and corn-fed cattle, but those fed low and high levels of CGF had carcasses that were fatter with lower lean meat yield. The three models underestimated DMI of all four diets. When DMI was set to observed intake in the models, CNCPS accurately predicted ADG and F:G ratio for cattle fed corn diets, but all models underestimated ADG of cattle fed barley. All models correctly predicted that gain during the feeding period was not limited by protein supply. The results from this study indicate that rolled-corn diets containing about 9.5% CP, with 50% of the CP as DIP are adequate for feedlot cattle weighing more that 500 kg. Substituting dry CGF for corn grain reduces feed efficiency and gain due to the lower digestible energy content of CGF. Key words: Grain, barley, corn, corn gluten feed, feedlot cattle, protein, models

Growth and carcass composition of lambs of two breeds and their cross grazing ryegrass and clover swards

AbstractThe effects of sward, breed type and sex on lamb growth and carcass composition were measured at two degrees of maturity in live weight. The three breed types were Scottish Blackface (no. = 60), Suffolk (no. = 59) and their reciprocal crosses (no. = 60). The lambs grazed swards of either ryegrass, clover or a mixed sward intended to contain both. The proportion of the mixed sward as clover was only 0.014. Each lamb was scanned using X-ray computed tomography to measure the weights of fat, lean and bone in the carcass at two proportions of mature body weight (0.30 and 0.45). Live weights were recorded weekly. Average daily gains (ADG) in live weight and carcass tissues were calculated for each lamb between the 0.30 and 0.45 stages of maturity.At the 0-30 stage of maturity, breed type differences in carcass composition were small; the Scottish Blackface had 0.942 as much bone as the Suffolk lambs (P &lt; 0.001), with the cross lambs intermediate. At the 0-45 stage of maturity, Scottish Blackface lambs had less fat (0.749 times as much; P &lt; 0.001), more lean (1.065 times as much; P &lt; 0.001) and more bone (1.055 times as much; P &lt; 0-001) than did Suffolk lambs. The values for crossbred lambs were intermediate but closer to those of the Suffolk. Neither sward nor its interaction with breed type had any significant effect on carcass composition at either the 0-30 or 0-45 stage of maturity. The effect of sex on carcass composition was significant at the 0-45 stage of maturity when castrated male lambs had less fat (P &lt; 0.001) and more lean (P &lt; 0.001) than female lambs. There were breed type by sward interactions for ADG in live weight (P &lt; 0.05), in carcass weight (P &lt; 0.001), and in fat (P &lt; 0.001) and bone weights (P &lt; 0.05). The interactions were such that Suffolk lambs had higher growth rates than Scottish Blackface lambs on clover but not on ryegrass or the mixed sward. There were no significant differences between Suffolk and crossbred lambs in growth rates on any sward. In this, and in two other experiments, the extent to which growth rate declined as the nutritional environment became worse was greater (P &lt; 0.05) in Suffolk than in Scottish Blackface lambs; that is, Suffolk lambs expressed greater environmental sensitivity than the Scottish Blackface.

Selection for growth in brown trout increases feed intake capacity without affecting maintenance and growth requirements.

The correlated responses in feed intake and G:F ratio with selection for increased growth rate were evaluated by comparing selected (S) and control (C) brown trout (Salmo trutta) reared under conditions known to affect feed efficiency: feed restriction and periods of compensatory growth. Nitrogen and energy requirements for maintenance and growth were also measured. Trout were allotted at comparable BW (3.7+/-0.06 and 3.8+/-0.04 g, for C and S respectively) to triplicate groups per treatment. The experiment lasted a total of 198 d, during which animals were successively submitted to a 116-d feeding phase and fed 10, 30, 50, 70, 100, and 140% of their usual daily ration (UDR), a 35-d phase of food deprivation, and a 47-d refeeding phase. The G:F of C and S were comparable in all experimental conditions tested. During the feeding phase, S grew better than C only when fed 100 and 140% UDR (P < 0.001). This was explained by a higher feed intake capacity. The requirements for growth and maintenance were similar among the lines, which is in agreement with their comparable loss of weight (mean energy loss of -53 and -55 kJ/(kg x d) for C and S, respectively; P > 0.38) observed during the feed deprivation phase and the lack of differences in carcass composition (fat, P > 0.35; protein, P > 0.54). During the refeeding phase, growth performance and G:F were high in all groups. The daily growth coefficient was higher in S than in C (P < 0.001) because of a higher feed intake (P < 0.001). An increase in absolute individual variability in final BW and length was associated with the level of food restriction in both lines; however, it always remained lower in S than in C. In conclusion, fish selected for growth under ad libitum conditions will only exhibit growth superiority when fed diets close to ad libitum, and there was no evidence that selection was associated with an improvement in efficiency of maintenance nor in retention of body tissues.

Utilization of torula yeast (Candida utilis ) as a protein source in diets for tilapia (Oreochromis mossambicus Peters) fry

A 63 day–1 feeding trial was conducted under laboratory conditions to evaluate the effects of substituting animal protein with a mixture of plant feedstuffs including 25, 30, 35, 40 and 45% of the protein with torula yeast (Candida utilis), 20% with soybean meal and 15% with Alfalfa Leaf Protein Concentrate (ALC), in diets for tilapia (Oreochromis mossambicus Peters) fry. Feeding efficiency was compared against a diet with fish meal as the sole protein source. Diet nutritional quality was very similar independent of composition, with no differences in growth parameters, but fish fed with 30% yeast diet showed the best growth performance. Diet composition did not affect feed or protein utilization, with the best feed conversion ratio, protein efficiency ratio and apparent nitrogen utilization in the 25% yeast diet. Protein digestibility was above 80% for all diets, and no differences in carcass composition were observed. The best incidence cost was obtained with 25% yeast and the highest profit index with 30% yeast, but no statistical differences were observed with the other treatments. The results suggest that it is possible to replace up to 65% of animal protein with a mixture of plant proteins, including 30% from torula yeast, in tilapia fry diets without adverse effects on fish performance and culture profit.

Plasma Glucose and Insulin Levels in Genetically Lean and Fat Sheep

This study investigated whether genetically lean and fat sheep displayed differences in insulin and glucose statuses. Lean genotype sheep had significantly (P<0.05) greater basal glucose concentrations than fat genotype sheep (4.78 versus 4.52, SED=0.104 mmol/l), although basal plasma insulin was not significantly different (mean 304, SEM=37.3 pmol/l) between the genotypes. During glucose tolerance tests (GTT), carried out at 4 levels of injection: 0, 0.28, 1.39 or 2.78 mmol glucose/kg liveweight, the area under the plasma insulin curve was significantly (P<0.05) greater for fat than lean genotype sheep, although there were no differences in any glucose parameters. There were no significant differences between genotypes in insulin or glucose concentrations during or following glucose infusion (GINF) experiments at 0, 0.09, 0.46 or 0.93 mmol glucose/kg live-weight/h over 3 hours. Elevated plasma insulin concentrations after a glucose tolerance test are concluded to be associated with increased fatness in this genetically selected line of sheep. However, the differences in insulin and glucose levels between the lean and fat genotype sheep are minor, relative to the differences in carcass composition.