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PubMed2003

Effects of butyrate on apoptosis in the pig colon and its consequences for skatole formation and tissue accumulation.

Evidence exists that butyrate inhibits apoptosis of colon crypt cells in vivo so that less tryptophan from cell debris is available for skatole formation by microbes in the pig colon. In this study, potato starch containing a high proportion of resistant starch was fed to test the hypothesis that increased butyrate formation will occur in the colon and contribute to reduced epithelial cell apoptosis, thus leading to reduced skatole formation and absorption. Two groups of six barrows were provided with catheters in the jugular vein and fed either a ration with pregelatinized starch (high ileal digestibility; controls) or potato starch (low ileal digestibility; PS) as the main carbohydrate. All pigs were fed 31 MJ of metabolizable energy and 381 g of crude protein per day. The controls were fed for 19 d. The PS group received the same control ration for 10 d, and then changed to the PS ration. The total feeding period of PS consisted of a 5 d adaptation period followed by another 19 d. In the continously sampled feces, pH, short chain fatty acids, and skatole were determined. Skatole was additionally measured in blood plasma that was sampled daily. After killing barrows at the end of the feeding period, fat tissue for skatole measurement and colon tissue for histological quantification of mitosis and apoptosis were obtained. Feeding potato starch led to a rapid 2.2 fold increase of fecal butyrate when compared both with the control period of the PS group and the control group (P < 0.001). PS feeding resulted in a decrease in pH from 7.3 to 5.3 (P < 0.001) and apoptosis from 2.06 cells/crypt to 0.90 cells (P < 0.01), whereas there was no change in mitosis. Consequently, skatole decreased both in feces (controls vs PS group: 120.0 vs 1.9 microg/g; P < 0.001) and in blood plasma (1.6 vs 0.2 ng/mL; P < 0.001). The mean concentration of skatole in fat tissue was 167 ng/g tissue in controls, and below the detection limit (0.8 ng/g) in the PS group (P < 0.001). It is concluded that butyrate-dependent inhibition of apoptosis in the colon due to potato starch feeding efficiently inhibits skatole production in barrows. Because of the depressed skatole levels, improved sensory quality of pork is possible.

Animal Feed↗

PubMed1988

Interactions of aflatoxin and the antioxidant butylated hydroxytoluene in two-week-old chicks.

Two-week dietary administration of 2500 ppb aflatoxin was sufficient to cause a decrease in bursal weights and a reduction in the number of splenic leukocytes in chicks. No significant effects on weight gain or feed efficiency were evident. The chicks also had elevated heterophil-to-lymphocyte ratios, suggesting a heightened reaction to stress. This effect could be blocked by dietary administration of the antioxidant butylated hydroxytoluene (BHT) at a concentration eight-fold over that normally present to preserve control feed. The BHT treatment increased the activities of the enzymes glutathione-S-transferase, aniline hydroxylase and O-demethylase, which metabolize aflatoxins in the liver.

Administration, Oral↗

PubMed1991

Macronutrient intake and utilization by rats: interactions with type I adrenocorticoid receptor stimulation.

Corticosterone-free (adrenalectomized, ADX) and intact rats were offered experimentally compounded diets in which 65% of available calories were supplied by a single macronutrient (single-diet study). ADX impaired the intake, weight gain (especially as body fat), and efficient utilization of high-protein and high-fat diets. In contrast, no behavioral, metabolic, or compositional changes could be found among ADX rats maintained on a diet high in carbohydrates. When ADX rats were given separate sources of macronutrients (self-selection study) they did not self-select a high-carbohydrate diet. Instead, they displayed a strong fat avoidance and a relative increase in protein intake, the macronutrient they utilize least efficiently. Separate groups of ADX animals were continuously infused with 25 or 125 micrograms.kg-1.day-1 aldosterone, a specific type I adrenocorticoid receptor agonist. Type I receptor stimulation eliminated all ADX-related deficiencies found in the single-diet and self-selection studies: caloric intake, feeding efficiency, carcass composition, and macronutrient preferences were restored to or beyond the corresponding values of adrenal-intact rats. The normal rat's ability to ingest and utilize macronutrients optimally is dependent on corticosterone's stimulation of type I receptors.

Adrenal Glands↗

PubMed1990

Influence of dietary supplementation with Streptococcus faecium M-74 on broiler body weight, feed conversion, carcass characteristics, and intestinal microbial colonization.

Two experiments were conducted to determine the influence of Streptococcus faecium M-74 supplementation of broiler diets. Mixed-sex or male only chicks were used in the experiments. Both experiments consisted of six dietary treatments and four replicates per treatment in a randomized block design. The S. faecium was fed alone for 21, 36, or 44 days or for 44 days with S. faecium supplemented in the water for the first 14 days. In another treatment, S. faecium was fed for 44 days, but the feed was restricted for Days 8 through 13. The S. faecium was also fed in combination with antibacterial products (AP) for 44 days. An additional diet was an unsupplemented basal, and another was supplemented only with AP. In Experiment 1, feed efficiency was significantly better with the basal and diets supplemented with S. faecium than with those diets supplemented with AP or AP and S. faecium. In Experiment 2, BW of broilers at 44 days of age were significantly heavier for broilers receiving S. faecium in the feed and also S. faecium in the water for the first 14 days as compared with broilers receiving AP or AP and S. faecium supplementation. There were no significant differences in carcass yield or composition characteristics. In Experiment 1, the scores representing S. faecium colonies found in the intestinal tract were not influenced by dietary treatment. The ceca had the highest S. faecium score of any of the intestinal tract locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed2004

Performance and carcass quality of steers fed different sources of dietary fat.

The hypothesis of this experiment was that increasing dietary fat through the use of whole oilseeds and altering the dietary ratio of PUFA:saturated fatty acids would alter carcass composition of finishing steers. Seventy-two steers (443.6 +/- 1.0 kg) were fed for 76 d one of four dietary treatments: a corn/ soybean meal-based diet (NOFAT); two diets containing 16% (DM basis) whole raw soybeans; and a corn/soybean meal-based diet containing choice white grease (CWG) equal to the fat addition supplied by the soybeans. Soybeans used in the diets were either a standard variety (NORM-SB) or a variety high in oleic acid content (HO-SB). The fatty acid profile of diets differed (P < 0.05) in the degree of saturation and content of palmitic, stearic, oleic, linoleic, and linolenic acids. There were no differences in ADG (1.73 kg/d), hot carcass weight (347 kg), longissimus muscle area (79.4 cm2), yield grade (3.31), or percentage of boneless retail cuts (48.8%). Contrasts revealed differences (P < 0.05) in G:F and marbling score with the addition of fat (0.126 vs. 0.137 and 4.66 vs. 4.91, respectively, for NOFAT vs. fat). The addition of fat tended (P < 0.10) to increase backfat, and feeding NORM-SB increased (P < 0.01) dressing percent compared with the HO-SB treatment. Loin samples taken from steers fed NOFAT, NORM-SB, and HO-SB did not differ in alpha-tocopherol content. Loins from the CWG treatment tended (P < 0.10) to have lower alpha-tocopherol content than did the soybean treatments (0.79 vs. 0.99 ppm, respectively). From main-effects analysis, HO-SB loin samples had the highest (F3,8 = 32.91; P < 0.01) concentration of gamma-tocopherol (0.33 ppm); this resulted in differences (P < 0.05) in gamma-tocopherol when comparing all contrasts. When comparing loin samples from NORM-SB-fed steers with those from HO-SB-fed steers, NORM-SB samples had a greater (P < 0.05) percentage oflinoleic acid and PUFA and a lower (P < 0.05) percentage of oleic acid and monounsaturated fatty acids. Furthermore, loin samples from soybean-fed steers tended (P < 0.10) to have a greater concentration of conjugated linoleic acid than samples from CWG-fed steers. These data suggest that the source of added dietary fat may affect overall carcass composition. Furthermore, dietary addition of soybeans or CWG can improve feed efficiency and marbling, whereas the addition of whole raw soybeans compared with CWG may increase unsaturation and total vitamin E content of beef.

Animal Feed↗

PubMed1975

Ensiled diet containing processed municipal garbage and sorghum forage for heifers.

Diets of similar proximate analysis formulated with a base of sorghum forage and primarily supplemented with equivalent dry matter of 18.4% of aerobically digested municipal garbage (garbage diet) or 17.5% of cottonseed hulls (control diet) were ensiled for 52 days and then individually and group fed to 16 dairy heifers for 56 and 35 days. Apparent digestibility of dry matter, crude protein, ether extract, crude fiber, and nitrogen-free extract in garbage and control diets averaged 54.2 and 47.4, 50.0 and 41.3, 62.0 and 65.1, 53.1 and 42.3, and 61.8 and 54.5% as determined by chromium oxide technique. Potential advantages from digestibility of the garbage diet appeared to be nullified by a 12% depression of dry matter intake and a consequent deterioration of feed efficiency. Dry matter intakes of garbage and control diets during the 56-day comparison were 1.98 and 2.25% of body weight and daily gains of .42 and .57 kg required 13.9 and 11.8 kg dry matter per kilogram of gain. Over the 91 days of combined comparison feeding, the .62 kg of average daily gain from control diet was 32% above the .47 kg from the garbage diet.

Animal Feed↗

PubMed2003

Effect of conjugated FA on feed intake, body composition, and liver FA in mice.

CLA is a generic term describing different isomers of linoleic acid with two conjugated double bonds. Various metabolic effects have been demonstrated following administration of CLA, including a change in body composition in animals. However, the effects of pure CLA isomers are not fully understood. In addition, conjugated octadecatrienoic acids such as calendic acid have not been extensively investigated. In this study, male and female ICR mice were fed pure CLA isomers (cis9,trans11 or trans10,cis12) or calendic acid (trans8,trans10,cis12) as their ethyl esters for 6 wk. Body protein content was significantly increased after feeding CLA isomers, either as pure isomers or as a mixture. Calendic acid significantly decreased body fat content in males. CLA (pure isomers or a mixture) significantly decreased body fat in both males and females, with the trans10,cis12 isomer being the most effective. The effect of the cis9,trans11 isomer was more pronounced in females than in males. It was concluded that the trans10,cis12 CLA isomer was mainly responsible for the decrease in fat content in mice, without a significant modification of feed efficiency, and that it was more effective than calendic acid.

Animals↗

PubMed1982

Dietary phosphorus requirement of channel catfish.

Two experiments were conducted to reevaluate the dietary phosphorus requirement of fingerling channel catfish. Basal diets containing either casein with supplemental inorganic phosphorus and 0.5% total calcium or egg albumin with supplemental inorganic phosphorus and 0.75% total calcium yielded similar requirement data. Eleven-week growth, feed efficiency, serum phosphorus, bone ash, bone calcium and bon phosphorus data indicate that 0.33% apparent available dietary phosphorus is adequate for maximum growth and bone mineralization. Based on these data and previous findings, we would suggest a value of 0.4% apparent available phosphorus be used in formulating catfish feeds. The apparent availability of phosphorus from soybean meal, as determined by the chromic oxide indicator method, was 29% for channel catfish.

Animals↗

PubMed1991

Evaluation of sometribove in a prolonged-release system in lactating dairy cows--production responses.

Primiparous (n = 105) and multiparous (n = 136) Holstein cows were used to evaluate efficacy of sometribove (n-methionyl bovine somatotropin, bST) in a dose titration study. Cows were fed TMR for ad libitum intake, were milked twice daily, and were allocated randomly within parity (1 vs. 2+) to treatments of 0, 250, 500, or 750 mg bST/14 d in a prolonged-release formulation. Subcutaneous injections commenced 60 +/- 3 d postpartum and continued throughout lactation. During a standardized treatment period of 252 d, treatment with increasing dosages of bST increased 3.5% FCM yield in a dose-dependent manner for both primiparous (2.5 kg/d, 10.2%; 3.5 kg/d, 14.3%; and 5.9 kg/d, 24.1%) and multiparous cows (3.1 kg/d, 12.1%; 3.9 kg/d, 15.2%; and 6.8 kg/d, 26.5%). Milk content of fat, protein, lactose, ash, Ca and P, and SCC were not affected by treatment. Over the 252-d treatment period, voluntary intake of energy was increased in bST-treated cows such that BW gain, body condition score, and net energy balance did not differ among treatment groups. Productive efficiency (milk per unit NEL intake corrected for BW change) over the treatment period was significantly increased in a dose-dependent manner for multiparous cows (4.1, 6.8, and 11.0%). Results demonstrated that bST administered in a prolonged-release formulation was efficacious in enhancing milk production and feed efficiency.

Animals↗

PubMed2001

Source and level of energy supplementation for yearling cattle fed ammoniated hay.

Brahman x British crossbred steers were used in growth and digestion trials to evaluate the response of source (corn, sugar cane molasses, or soybean hulls) and feeding rate (0, 1.4, or 2.8 kg DM per steer daily in the growth trials; 0, 15, or 30% of the ration DM in the digestion trial) of energy supplementation in cattle fed ammoniated (4% of forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Cattle on all treatments were fed 0.5 kg cottonseed meal daily. In the growth trials, steers grazed dormant bahiagrass (Paspalum notatum) pasture. Increasing the levels of supplementation decreased hay intake but increased total dietary intake for all diets (P < 0.07). Daily gain and feed efficiency of steers were improved (P < 0.03) with supplementation. Steers supplemented with corn or soybean hulls at 2.8 kg DM/d had a higher ADG (0.92 kg) and gain/feed (0.103) than steers supplemented with molasses (0.78 kg, 0.08, respectively) at the same level. Seven crossbred steers (200 kg) were used in a five-period digestion trial to evaluate apparent OM, NDF, ADF, and hemicellulose digestibility. Apparent OM digestibility of all diets increased linearly (P = 0.02) as the level of supplementation increased. Apparent NDF and ADF digestibility decreased (P < 0.03) as the level of supplementation with corn or molasses increased, whereas increasing the level of soybean hulls in the diet increased (P < 0.06) apparent NDF and ADF digestibility. Four ruminally fistulated crossbred steers (472 kg) were used in a 4 x 4 latin square design to investigate ruminal characteristics with energy supplementation at 30% of ration DM. Ruminal pH in steers supplemented with soybean hulls or corn declined after feeding. Ruminal pH decreased more rapidly with corn supplementation and remained below 6.2 for a longer period of time than with the other diets. Ruminal pH did not change within 24 h after feeding for steers fed the control or molasses diets. No change in total VFA concentration was observed in steers fed molasses or corn. Total ruminal VFA concentration in steers supplemented with soybean hulls increased initially after feeding and then declined within 24 h after feeding. Soybean hulls produced fewer negative associative effects than corn when fed with ammoniated stargrass hay at 2.8 kg DM/d. The reduced gain/feed of steers supplemented with molasses compared to soybean hulls or corn indicates that molasses was not utilized as efficiently as the other energy sources.

Ammonia↗

PubMedDate not supplied

Antioxidant defense mechanisms in the male rat: interaction with alcohol, copper, and type of dietary carbohydrate.

The activities of enzymes participating in cellular protection against free radical reactions were measured in hepatic tissues from copper-adequate and copper-deficient rats fed fructose or starch-based diets. Half of the rats consumed 20% ethanol in their drinking water. The consumption of ethanol depressed growth rate, reduced hematocrit, and hepatic copper concentration. Feed efficiency was greatly depressed by ethanol. Mortality due to copper deficiency occurred in fructose-fed rats and in starch-fed rats that drank ethanol. Ethanol had no effect on superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), or catalase. In contrast, copper deficiency reduced SOD and fructose feeding depressed catalase activity. GSH-Px was not affected by either the type of dietary carbohydrate, copper, or ethanol. Taken together, these data suggest that additional mechanisms to antioxidant defense systems are responsible for the metabolic changes that occur during the interactions between ethanol low copper and dietary carbohydrates.

Animals↗

PubMed2004

Isoleucine requirement for late-finishing (87 to 100 kg) pigs.

Three pig trials were carried out to determine the true digestible Ile requirement for maximal weight gain and minimal plasma urea nitrogen (PUN) of late-finishing (87 to 105 kg) pigs. In Exp. 1, an Ile-deficient basal diet was developed and confirmed to be markedly deficient in Ile, yet fully efficacious when fortified with surfeit Ile. This diet contained corn and dried red blood cells (RBC) as Ile sources, and was analyzed to contain 10.5% CP, 0.25% Ile, and 0.63% lysine; ME was calculated to be 3,475 kcal/kg. True digestibility of Ile in the basal diet was 88% based on previous digestibility trials in ileal-cannulated pigs and cecectomized roosters. Experiment 2 was a growth trial that involved five graded levels of crystalline Ile supplementation (0.02%) to generate five dose levels of true digestible Ile (0.25 to 0.33%), Diets 1 through 5, respectively. Gain and feed efficiency showed a linear response to incremental doses of Ile (P = 0.003 and 0.036, respectively), with an apparent plateau at 0.31% true digestible Ile. In Exp. 3, a replicated 5 x 5 Latin square, five barrows (Square 1) and five gilts (Square 2) were used in five 4-d feeding periods, with five levels of true digestible Ile (0.22 to 0.30%). Using feed intake as a covariate, a linear decrease in PUN occurred in gilts (8.9, 8.6, 8.0, 7.0, and 5.5; P = 0.004) and in gilts and barrows combined (9.5, 9.2, 9.2, 8.5, and 7.6; P = 0.006) as Ile increased incrementally. The PUN results for barrows (10.5, 10.0, 10.2, 9.9, and 9.7) were not affected by dietary Ile (P = 0.417). The results of these experiments suggest that the factorial requirement estimate of 0.30% true digestible Ile for high-lean, late-finishing pigs suggested by the NRC Subcommittee on Swine Nutrition is accurate.

Animal Feed↗

PubMed2000

Preliminary toxicity study on the individual and combined effects of Citrullus colocynthis and Nerium oleander in rats.

The toxicity of diet containing 10% of Citrullus colocynthis fruits or 10% of Nerium oleander leaves or their 1:1 mixture (5%+5%) for rats treated for 6 weeks was determined. Dullness, ruffled hair, decreased body weight gains and feed efficiency, and enterohepatonephropathy characterised treatment with C. colocynthis and N. oleander given alone. Diarrhoea was a prominent sign of C. colocynthis poisoning. Organ lesions were accompanied by leucopenia, anaemia and alterations in serum AST, ALT and ALP activities and concentrations of total protein, albumin, urea, bilirubin and other serum constituents. Feeding the mixture of C. colocynthis and N. oleander caused more marked effects and death of rats.

Animals↗

PubMed1999

The effect of monochromatic light on broiler growth and development.

Artificial illumination, including light quality, is crucial in modem broiler management. In the present study, a new, highly efficient, monochromatic light system has been developed for broilers. One hundred and eighty male broiler chicks (Anak) were divided into four light treatment groups (n = 45) in three replicates each. All birds were housed in a single room previously divided by wooden bars into 12 sealed cells of 1 m2. Feed and water were provided for ad libitum consumption. Light intensity was 0.1 W/m2 at the height of birds' heads and was scheduled for 23 h of light and 1 h of dark during the entire experimental period. Light treatments were: control white (mini-incandescent light bulbs), blue (480 nm), green (560 nm), and red (660 nm). Body weight was recorded periodically, feed consumption was measured daily, and feed efficiency was calculated. Blood samples were taken at 1, 9, and 32 d of age and plasma testosterone was determined. Two necropsies were conducted, at 23 and 35 d of age, and selected glands and organs were weighed. In the group reared under green light, a significant enhancement in weight gain was observed as early as 3 d of age; this gain was maintained during the entire experimental period. Broilers reared under blue light had a later onset of growth enhancement and were significantly heavier than those reared under white and red light at 20 d of age. Plasma testosterone levels were significantly higher in birds reared under blue light. Breast muscle weights were significantly higher in the birds reared under green light at 23 and 35 d of age. These results suggest that green and blue light stimulate growth.

Aging↗

PubMed1999

Evaluation of sorghum ergot toxicity in broilers.

Three experiments evaluated the performance of broilers fed sorghum ergot consisting of sphacelia/sclerotia of Claviceps africana present in tailings removed by conditioning of seed from grain sorghum hybrid seed production fields near Uvalde (Experiments 1 and 2) and Dumas (Experiment 3), Texas. Percentage sphacelia/sclerotia and total alkaloid content, respectively, in sorghum ergot tailings were 8% and 11.3 ppm for Uvalde and 75% and 235 ppm for Dumas. Sorghum ergot and control sorghum diets were based on the NRC (1994) requirements for starting broilers. In Experiment 1, neither growth nor feed efficiency were significantly reduced in male broilers fed sorghum ergot from hatch to 3 wk of age, but liver weights were significantly greater than those in the control. In Experiment 2, straight-run broilers were raised to 6 wk of age in floor pens using a three-phase feeding program. Sorghum ergot significantly reduced gain in 4-wk-old broilers and cumulative body weight at 5 wk. Feed conversion was significantly reduced during all three phases of feeding. In Experiment 3, control sorghum and the 75% ergot tailings were added to corn-soy basal diets at rates of 2.5, 5, and 10% by weight and fed to male broilers from hatch to 3 wk of age. Sorghum ergot did not significantly reduce growth, but, during Weeks 2 and 3, feed-to-gain ratios were higher. Neither type nor concentration of sorghum ergot significantly affected relative liver weights. We did not observe significant mortality or obvious symptoms of ergot toxicity, such as necrotic lesions of the feet or vesicular dermatitis of the comb, in any of the three experiments.

Animal Feed↗

PubMed2003

Identification of three single nucleotide polymorphisms in the chicken insulin-like growth factor 1 and 2 genes and their associations with growth and feeding traits.

The chicken insulin-like growth factor (IGF)1 and IGF2 genes have been partially sequenced in six individuals of each of two chicken strains of the Black Penedesenca breed (PN and MN). These two strains are genetically diverse for growth traits. Sequence alignment revealed the existence of three single nucleotide polymorphisms (SNP) (IGF1-SNP1, IGF2-SNP2, and IGF2-SNP3). These three SNP and a fourth IGF1 polymorphism (IGF1-SNP4) were typed in 60 individuals from each strain by using PCR-RFLP or primer extension analysis. No significant associations among these four SNP, growth traits, and plasma IGF1 concentration were identified. In contrast, suggestive associations (P < or = 0.05) were found between IGF1-SNP1 and average daily gain at 107 d and feed efficiency at 44, 73, and 107 d. However, these associations were not simultaneously found in both strains suggesting that they might have been produced by linkage disequilibrium with another mutation located in the IGF1 locus or another linked gene. Since the PN and MN strains differ very markedly on their feed intake, the chicken leptin gene was included in the sequence analysis. Unfortunately, attempts to amplify several regions of this gene were unsuccessful. Even when primers complementary to highly conserved regions were used, the PCR consistently failed. Other authors have reported similar problems when trying to amplify avian leptin sequences.

Animals↗

PubMedDate not supplied

Effects of Thymus vulgaris L. as feed additive in piglets and against haemolytic E. coli in vitro.

The aim of the study was to test Thymi herba (1.66% v/w essential oil with 39% p-cymene and 32% thymol) in the rearing period of piglets as feed additive. Therefore, two feeding trials were performed with piglet groups ranging from 17 to 22 animals each. Either 10 g of Thymi herba/kg feed (Thymi herba group), 10 mg flavophospholipol/kg feed (flavophospholipol group) or nothing (control group) was added to the animals' feed. No significant differences in the performance parameter daily weight gain among any groups were recorded. No differences concerning feed efficiency or isolation of haemolytic E. coli serotypes were shown. In addition, the antibacterial activity of the essential oil of Thymi herba against 39 haemolytic E. coli isolates from the same weaners was investigated in vitro by disk diffusion, minimum inhibitory concentration and bactericidal concentration testing. In contrast to the feeding results, the essential oil of the thyme batch fed showed antibacterial activity against all haemolytic E. coli investigated. This interesting antibacterial potential of Thymi herba prompts further investigations as to its value as feed additive.

Animal Feed↗

PubMed1995

Endogenous proteolytic enzymes in chicken muscles. Differences among strains with different growth rates and protein efficiencies.

The theory that net muscle growth is, at least partly, regulated by catabolic factors has been tested in order to set up an animal model to study meat aging and post-mortem tenderization. Male and female chickens of a layer strain (White Leghorn), a commercial broiler strain (Ross), and two experimental broiler lines (designated GL and FC) were used to estimate differences in proteolytic enzyme activities in the breast muscles. The GL and the FC lines were selected for high body weight gain and high feed efficiency, respectively. At 6 wk of age the birds were slaughtered and the activities of endogenous proteinases and their specific inhibitors in breast muscles measured. The Leghorns showed significant differences in all traits compared with the three broiler genotypes. Within the broiler types, FC birds tended in the direction of the Leghorns and GL birds in the opposite direction. Ross birds were intermediate between FC and GL birds. All types and sexes differed significantly in slaughtering weight. Feed conversion ratio and protein conversion ratio were highest for Leghorns. The FC birds showed the lowest feed conversion. Ross and GL birds showed intermediate values. The Leghorns showed higher calpain activities and lower calpastatin activity than the three broiler genotypes. The FC broilers showed intermediate calpain and calpastatin activities but higher cathepsin H and total cystatin values. The GL broilers showed lower cathepsin B, D, and H activities. In all cases the Ross broilers showed intermediate values. From these figures it is concluded that the strains of birds used in this study can be used as a natural source of variability to study the mechanisms involved in post-mortem proteolytic degradation and thus in the study of muscle tenderization and meat aging. It is also concluded that it could be very interesting to study the behavior of the different proteolytic systems more carefully in relation to muscular growth characteristics and compare them to anabolic factors involved in muscle growth.

Animals↗