Dietary tryptophan effects on plasma and salivary cortisol and meat quality in pigs

Four experiments were conducted to determine the effects of supplemental Trp on meat quality, plasma and salivary cortisol, and plasma lactate. Experiment 1 was a preliminary study to measure plasma cortisol concentrations in 4 barrows (50 kg of BW) that were snared for 30 s at time 0 min. Pigs were bled at -60, -30, -15, 2, 4, 6, 8, 10, 15, 20, 25, 30, 45, 60, 90, and 120 min. Plasma cortisol was near maximum 10 min after the pigs were snared. In Exp. 2, 20 barrows (50 kg of BW) were allotted to a basal corn-soybean meal diet or the basal diet with 0.5% supplemental l-Trp for 5 d. After the 5-d feeding period, pigs were snared for 30 s and bled at -10, 0, 2, 4, 6, 8, 10, 15, 20, 25, 30, 45, 60, 90, and 120 min after snaring. Pigs fed the diet with supplemental Trp had a lower (P < 0.01) mean plasma cortisol than pigs fed the basal diet. Plasma lactate also was decreased (P < 0.07) by supplemental Trp. In Exp. 3, the same pigs and treatments were used as in Exp. 2, but 5 pigs were snared and 15 pigs adjacent to those being snared were bled to determine if pigs are stressed when they are adjacent to pigs being snared. For pigs adjacent to snared pigs, the area under the curve (P < 0.06) and mean for plasma cortisol was lower (P < 0.01) in pigs fed Trp relative to those fed the basal diet. In Exp. 4, 90 barrows (initial BW of 106 kg) were allotted to 6 treatments in a 3 x 2 factorial arrangement. Three diets with Trp (basal diet, basal supplemented with 0.5% Trp for 5 d, or pigs fed the basal diet with a 0.1 g/kg of BW Trp bolus given 2 h before slaughter) were combined with 2 handling methods (minimal and normal handling). Dressing percent, 24-h pH, and 24-h temperature were reduced in the minimally handled pigs (P < 0.10) compared with the normally handled pigs. Pigs fed Trp in the diet relative to those fed the basal diet had increased 45-min temperature, Commission Internationale de l'Eclairage (CIE) redness (a*) and yellowness (b*) values, and drip and total losses (P < 0.10). Tryptophan in bolus form decreased 45-min pH in the minimally handled pigs but increased 45-min pH in the normally handled pigs (handling x Trp bolus interaction, P = 0.08). Tryptophan in the diet increased CIE lightness (L*) in minimally handled pigs but decreased CIE L* in the normally handled pigs (handling x Trp diet interaction, P = 06). No other response variables were affected by handling method or Trp. Results indicate that Trp decreases plasma cortisol but has no positive effect on meat quality.     

Economic values for meat quality traits in pigs.

The aim for this study was to derive economic values for meat quality traits. Meat quality experts from 10 slaughter and retail companies in Switzerland were asked to give an interview in which they indicated their willingness to pay different prices for carcasses from different quality classes. Economic values for the seven meat quality traits color (L*), drip loss, intramuscular fat content, iodine value, pH1 (45 min after slaughtering), pH2 (24 to 30 h after slaughtering), and proportion of premium cuts were derived from the answers. For each trait, a weighted mean of these economic values was calculated using the number of pigs slaughtered by a company per year as a weighting factor. Population mean and standard deviation of the investigated traits were taken from station test results of Swiss Large White pigs (intramuscular fat content, iodine value, pH1, pH2, and proportion of premium cuts) and from the literature (color and drip loss). Weighted means (range among companies) of economic values per slaughter pig on the basis of one phenotypic standard deviation of the trait in Swiss Francs (SFr.) were -22.92 (0 to -62.46) for color, -10.27 (0 to -43.64) for drip loss, 10.84 (0 to 29.43) for intramuscular fat content, -29.90 (-15.54 to -43.58) for iodine value, 11.50 (.67 to 19.79) for pH1, 0 (0) for pH2, and 10.92 (-2.30 to 33.67) for proportion of premium cuts.     

生长猪日粮中添加虫肽蛋白对肉质和风味的影响

本试验选用保育出栏的杜×长×大三元杂交小猪96头,随机分成两个组,试验组日粮中添加5％虫肽蛋白．对照组饲喂常规日粮（玉米豆粕型）。经过105d的饲喂试验．结果表明：试验组日增重比对照组提高2．24％;饲料转化率比对照组提高0．75％。通过屠宰猪对肉质和风味进行观察和品尝．试验组猪肉比较鲜红、肉味口感爽滑、肥肉肥而不腻、清煮肥肉汤中油腻甚少、肉质细嫩、甘香可口：对照组猪肉色泽暗红、口感有渣、含酸味、有肉膻味。     

Effects of dietary soy isoflavones on growth, carcass traits, and meat quality in growing-finishing pigs

Two experiments were conducted to determine the effect of soy isoflavones on growth, meat quality, and carcass traits of growing-finishing pigs. In Exp. 1, 36 barrows (initial and final BW, 26 and 113 kg, respectively) were used and each treatment was replicated four times with three pigs each. The dietary treatments were 1) corn-soybean meal (C-SBM), 2) corn-soy protein concentrate (low isoflavones, C-SPC), or 3) C-SPC + isoflavones (isoflavone levels equal to those in C-SBM). Daily gain and ADFI were increased (P < 0.10) in pigs fed the C-SPC relative to pigs fed the C-SPC + isoflavone diet in the late finishing period; otherwise, growth performance was not affected (P > 0.10) by diet. Longissimus muscle area, 10th-rib fat depth, percentage muscling (National Pork Producers Council), 24-h pH and temperature, color, firmness-wetness, marbling, drip loss, and CIE L*, a*, and b* color values were not affected (P > 0.10) by diet. Dressing percentage, carcass length, weight and percentage of fat-free lean in ham and carcass, lean gain per day, lean:fat, and ham weight were increased (P < 0.10), and ham fat and percentage fat in ham and carcass were decreased (P < 0.10) in pigs fed the C-SPC + isoflavone diet compared with pigs fed the C-SPC diet. Pigs fed the C-SPC + isoflavone diet had similar (P > 0.10) carcass traits as pigs fed the C-SBM diet, except carcass length, percentage ham lean and thaw loss were greater (P < 0.10), and total ham fat was less (P < 0.10) in pigs fed the C-SPC + isoflavone diet. In Exp. 2, 60 gilts (initial and final BW, 31 and 116 kg, respectively) were used, and each treatment was replicated five times with four pigs per replicate. The treatments were 1) C-SBM, 2) C-SBM + isoflavone levels two times those in C-SBM, and 3) C-SBM + isoflavone levels five times those in C-SBM. Daily feed intake was linearly decreased (P < 0.10) in the growing phase and increased (P < 0.10) in the late finishing phases as isoflavone levels increased; otherwise, growth performance was not affected (P > 0.10) by diet. Diet did not affect (P > 0.10) carcass traits; however, CIE a* and b* color scores and drip loss were decreased (P < 0.06) as isoflavone levels increased. Soy isoflavones decreased fat and increased lean in barrows when fed within the dietary concentrations found in typical C-SBM diets but not when fed to gilts at concentrations above those present in C-SBM diets.     

不同肉质改良剂在肉猪肥育阶段的试验效果

随着国民经济发展和人民生活水平不断提高 ,人们对畜产品质量的要求也越来越高 ,对优质无公害放心肉的需求量越来越大 ,这种趋势将会持续增长。随着我国规模化养猪业的发展 ,在高产、高效的同时 ,如何生产符合国家有关标准和确保消费者健康安全的优质猪肉是养猪者所面临的重要问题。各科研单位开发研制的肉质改良剂 ,正是在国家安全生产猪肉的有关政策法规基础上生产出的高科技产品 ,对发展安全、高效、优质的放心肉和促进养猪业可持续发展都具有重要的现实意义。肉质改良剂具有促进生长、降低料耗、提高肉的持水性和改善肉色、提高饲料利用…     

牛至油对育肥猪生长性能和肉品质的影响

文章旨在研究不同浓度的牛至油对肥育猪生长性能和肉质特性的影响。试验选择32头阉割公猪和32头后备母猪随机分成4个组,对照组饲喂基础日粮,试验组分别在基础日粮中添加0.2、0.4和0.8mg/kg牛至油,试验共开展5周。试验结束后禁食12h,称重后屠宰。经过一夜的冷却,从屠体上取50cm的腰肌(每组8头,4头公猪、4头母猪)。日粮中添加牛至精油对生长猪末重、日增重、屠宰率均无显著差异(P>0.05),同时各组最长肌嫩度、屠宰后45min和24h后的pH、肉色及感官特性也无显著差异(P>0.05)。此外,脂质氧化试验结果显示,日粮添加牛至油对肌肉无明显的抗氧化作用(P>0.05)。综上所述,由于胴体和肉质属性均无显著变化,说明本试验中日粮添加不同水平牛至油对猪的肉质参数没有影响。     

营养水平对鲁农2号生长猪屠宰性能和肉品质的影响

试验选用108头鲁农2号生长猪(49.58±1.49)kg,随机区组,分为3个处理组,每处理4个重复,每重复(圈)9头猪,在保持日粮消化能/粗蛋白质比例不变的情况下,分为高、中、低3个营养水平组,研究日粮不同消化能和粗蛋白质水平对鲁农2号生长猪屠宰性能和肉品质的影响。试验分50～80 kg和80～100 kg两个体重阶段饲养,当试验猪平均体重达到100 kg时进行屠宰,测定屠宰性能和肉品质。结果表明:3个处理组的背膘厚、眼肌面积、后腿重、后腿比例、脂肪率、屠宰率和瘦肉率均差异不显著(P>0.05);除大理石纹外,3个处理组的肉品质差异也不显著(P>0.05)。这预示着低能量和粗蛋白质日粮饲喂鲁农2号生长猪可以获得与高能量粗蛋白质日粮相近的屠宰性能和肉品质。     

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background

Highly automated cage-rearing systems are becoming increasingly popular in China. However, a high stocking density can cause oxidative stress and decrease broiler performance. The tryptophan (TRP) derivative 5-hydroxytryptophan (5-HT) has been shown to preserve membrane fluidity in birds suffering from oxidative stress. Therefore, this experiment was conducted to determine the effects of dietary TRP supplementation on performance, breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density.

Methods

Female Arbor Acres broilers (25-d-old, n = 144) were randomly allocated to 1 of 4 treatments. The birds were fed a diet based on corn, soybean meal, cottonseed meal and corn gluten meal containing either 0.18 or 0.27% TRP and were housed with stocking densities of 11 or 15.4 birds/m² in a 2 × 2 factorial experiment. Broiler performance was evaluated from d 25 to 42. Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices.

Results

A higher stocking density tended to be associated with reduced weight gain (P < 0.10), and significantly increased plasma glutamic-pyruvic transaminase (GPT) activity (P < 0.001). Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma (P < 0.01), reducing drip loss of breast muscle (P < 0.10) and improving feed efficiency (P < 0.10).

Conclusions

An increase in dietary TRP, 1.5-fold higher than the standard supplementation level, can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.     

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background:Highly automated cage-rearing systems are becoming increasingly popular in China.However,a high stocking density can cause oxidative stress and decrease broiler performance.The tryptophan(TRP) derivative5-hydroxytryptophan(5-HT) has been shown to preserve membrane fluidity in birds suffering from oxidative stress.Therefore,this experiment was conducted to determine the effects of dietary TRP supplementation on performance,breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density.Methods:Female Arbor Acres broilers(25-d-old,n=144) were randomly allocated to 1 of 4 treatments.The birds were fed a diet based on corn,soybean meal,cottonseed meal and corn gluten meal containing either 0.18 or 0.27%TRP and were housed with stocking densities of 11 or 15.4 birds/m2 in a 2 × 2 factorial experiment.Broiler performance was evaluated from d 25 to 42.Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices.Results:A higher stocking density tended to be associated with reduced weight gain(P0.10),and significantly increased plasma glutamic-pyruvic transaminase(GPT) activity(P0.001).Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma(P0.01),reducing drip loss of breast muscle(P0.10) and improving feed efficiency(P0.10).Conclusions:An increase in dietary TRP,1.5-fold higher than the standard supplementation level,can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.     

虫草真菌发酵中草药培养基对生长肥育猪生产性能和胴体品质的影响

随机选择65日龄、均重25.0kg的杜长大生长猪160头,随机分为4组,研究虫草真菌液体发酵中草药培养基对生长肥育猪生产性能和胴体品质的影响。结果表明,日粮中添加100mg/kg、200mg/kg和300mg/kg虫草真菌液体发酵中草药培养基后,与对照组相比,生长肥育猪的日增重分别提高了7.64%、9.23%和11.19%(P≤0.05或P≤0.01),采食量分别提高了2.72%、1.37%和2.10%(P≥0.05),料肉比分别降低了4.58%、7.19%和8.17%(P≤0.05或P≤0.01),屠宰率分别提高了2.95%、5.66%和8.53%(P≤0.05或P≥0.05),瘦肉率分别提高了0.60%、2.67%和6.64%(P≥0.05),背膘厚分别降低了4.29%、5.71%和8.29%(P≤0.05或P≥0.05)。结论:虫草真菌液体发酵中草药培养基可明显提高生长猪生产性能,改善育肥猪胴体品质。     

复合维生素添加剂对肉猪肥育性能、胴体性状和肌肉品质的影响

<正>国内外先进养猪技术的应用,使猪胴体瘦肉率、生长速度和饲料报酬有了较大幅度的提高,这种提高却是以猪肌肉品质下降为代价的,因此如何利用营养     

Influence of dietary protein concentrations on performance and nitrogen repletion in stressed calves

Three trials were conducted to determine the influence of dietary CP concentration on health and performance of market-transport-stressed feeder calves (Exp. 1 and 2) and on repletion of nutrients lost during a 3-d feed and water deprivation period in steers fed at maintenance energy intake (Exp. 3). In Exp. 1 (84 calves) and 2 (256 calves), feeder calves averaging 184 kg were transported from Tennessee to Texas. In Exp. 1, calves were fed receiving diets containing either 12 or 16% CP. In Exp. 2, calves were fed diets containing 12 or 16% CP and .8 or 1.3% potassium in a 2 x 2 factorial arrangement of treatments. In Exp. 3, four Hereford steers averaging 253 kg were used in an N balance trial. Steers were deprived of feed and water for 3 d and then were limit-fed (1 x maintenance energy requirements) diets calculated to meet 100, 120, 140 or 160% of CP maintenance requirements for 14 d in a 4 x 4 Latin square design. In Exp. 1, calves fed the 16% CP diet had faster (P less than .05) daily gains and higher (P less than .10) feed consumption than calves fed the 12% CP diet during the first 14 d. In Exp. 2, calf performance was not affected by diet CP or K content. Calves fed the 16CP-1.3K diet had lower (P less than .10) mortality than calves on the remaining treatments. In Exp. 3, N balance and serum urea N increased linearly (P less than .05) with increasing dietary CP. Results of these studies are interpreted to indicate that the CP requirement (g/d) of market-transport-stressed feeder calves is similar to requirements of nonstressed calves; however, the CP concentration of the diet of stressed calves may need to be increased when feed intakes are low.     

Effects of increasing dietary niacin on growth performance and meat quality in finishing pigs reared in two different environments

We conducted two experiments to determine the effects of added dietary niacin on growth performance and meat quality in finishing pigs. Pigs were blocked by weight and assigned to one of six dietary treatments in both experiments. Dietary treatments consisted of a corn-soybean meal-based control diet (no added niacin) or the control diet with 13, 28, 55, 110, or 550 mg/kg of added niacin. In Exp. 1, pigs were housed at the Kansas State University research from with two pigs per pen (six pens per treatment per sex). In Exp. 2, pigs were housed with 26 pigs per pen (four pens per treatment per sex) in a commercial research barn. In Exp. 1, 144 pigs (initially 51.2 kg) were fed diets in two phases (d 0 to 25 and 25 to 62) that were formulated to 1.00 and 0.75% lysine, respectively. In Exp. 2, 1,248 pigs (initially 35.9 kg) were fed diets in four phases (d 0 to 28, 29 to 56, 57 to 84, and 85 to 117), with corresponding total lysine concentrations of 1.25, 1.10, 0.90, and 0.65% lysine, respectively. Added fat (6.0%) was included in the first three phases. In Exp. 1, average daily feed intake tended (quadratic, P < 0.07) to increase then return to values similar to control pigs as dietary niacin increased. Longissimus muscle (LM) 24-h pH (longissimus of pigs fed added niacin) tended to increase (control vs niacin, P < 0.06) for pigs fed added niacin. In the commercial facility (Exp. 2), increasing added niacin improved gain:feed (quadratic, P < 0.01) and subjective color score, and ultimate pH (linear, P < 0.01). Added niacin also decreased (linear, P < 0.04) carcass shrink, L* values, and drip loss percentage. Results from these two studies show that 13 to 55 mg/kg added dietary niacin can be fed to pigs in a commercial environment to improve gain:feed. It also appears that pork quality, as measured by drip loss, pH, and color, may be improved by higher concentrations of added dietary niacin.     

Effect of dietary Rhodobacter capsulatus on cholesterol, triglycerides concentration, and meat quality of finishing pigs

The study was designed to investigate the effect of Rhodobacter capsulatus on serum and meat cholesterol, fatty acid composition in meat, as well as meat quality of finishing pigs. A total of 16 120-day-old Landrace female pigs of about 60 kg initial body weight were randomly assigned into two groups. The pigs were fed a supplemented diet with 0.04% dietary R. capsulatus or a control diet for 60 days. Total cholesterol and low density lipoprotein-cholesterol concentration in serum was significantly lowered ( P  < 0.05) in the pigs fed the R. capsulatus supplemented diet compared to the control diet. Carcass weight, carcass length, shoulder fat, back fat and loin fat thickness, longissimus muscle (LM) area, and color score did not differ significantly between the pigs fed the R. capsulatus supplemented diet and control diet. Among the nutrient composition of LM meat, neutral fat and triglyceride concentration were significantly ( P  < 0.05) reduced in the finishing pigs by dietary supplementation of R. capsulatus . The proportions of n-6 PUFA were higher ( P  < 0.05) in the pigs fed the R. capsulatus supplemented diet than in the pigs fed the control diet. The supplementation of dietary R. capsulatus to finishing pig diet played important roles in reducing serum cholesterol and meat triglycerides, as well as in increasing polyunsaturated fatty acid content in LM meat.     

中草药饲料添加剂及不同饲粮类型对生长肥育猪肉脂品质的影响

选取胎次、日龄、体重相近的长白ד苏黑”生长肥育猪60头,随机分为6组,每组10头,公母各半。采取纯中草药制剂、中草药VE/Se合剂、抗生素三种不同添加剂和全植物性饲粮、含鱼粉饲粮两种不同饲粮类型,进行饲养试验和屠宰测定,并对背最长肌、背部脂肪进行采样,测定分析其肉脂品质。结果表明,应用纯中草药制剂和中草药VE/Se合剂,采取全植物性饲粮,能改善生长肥育猪的肉脂品质。     

斜发沸石添加水平对育肥期苏淮猪生长性能、屠宰性能和肉品质的影响

本试验研究基础日粮中添加不同水平的斜发沸石对育肥期苏淮猪生长性能、肉品质的影响,旨在获得苏淮猪育肥期斜发沸石的适宜添加量。选择体重相近(50 kg左右)、健康的苏淮阉公猪40头,随机分为对照组、试验Ⅰ组、试验Ⅱ组、试验Ⅲ组共4个处理组,每组10头。预试期10 d,所有猪自由采食对照组基础日粮;正试期64 d,对照组饲喂基础日粮,试验Ⅰ至Ⅲ组分别在基础日粮中添加0.5%、1.0%和2.0%的斜发沸石。于试验结束屠宰全部试验猪,用于屠宰测定和肉质检测。结果表明:1)第1阶段(体重56~68 kg)和第2阶段(体重83~98 kg),终末体重、平均日增重、料重比均无显著差异;但斜发沸石水平对第1阶段和第2阶段平均日采食量影响显著(P<0.05)并呈线性(P=0.02,P=0.047)二次方升高趋势(P=0.01)。2)对照组、试验Ⅰ组、Ⅱ组和Ⅲ组苏淮猪的生长曲线拐点分别是:第50.26天86.06 kg、第40.22天87.15 kg、第38.27天89.69 kg和第45.98天89.02 kg;最大日增重分别是0.702、0.743、0.814和0.855 kg/d,说明在饲料中添加斜发沸石后,可延长育肥猪到达生长曲线拐点体重。3)斜发沸石水平对眼肌面积和肌内脂肪影响显著(P<0.05),眼肌面积随斜发沸石添加水平的升高,呈二次方(P=0.01)变化;肌内脂肪呈线性(P=0.01),二次方(P=0.03)升高;胴体重和系水力分别随斜发沸石添加水平的升高,呈线性(P=0.07,P=0.09)升高趋势。试验表明:苏淮育肥猪采食量、胴体重和肌内脂肪随日粮斜发沸石添加水平增加呈线性升高,系水力呈线性升高趋势,但眼肌面积随斜发沸石添加水平的升高,呈二次方变化,先升高后降低。因此,添加2%斜发沸石有利于采食量、胴体重和肌内脂升高,有助于系水力降低;但从增加眼肌面积的角度考虑,斜发沸石的适宜添加比例为1%。     

Effect of dietary excess of branched‐chain amino acids on performance and serum concentrations of amino acids in growing pigs

Depressed performance and availability of some amino acids (AA) in pigs fed excess Leu diets appear to be related to lower feed intake. Surplus Ile and Val may help to overcome this effect. An experiment was conducted with 24 pigs (31.8 ± 1.2 kg initial BW) to evaluate the effect of dietary excess of either Leu alone or with surplus Ile and Val on performance and serum concentration (SC) of essential AA. Treatments were as follows: T1, basal diet; T2, basal plus 0.43% L‐Leu (excess Leu); T3, basal added with 0.43% L‐Leu, plus 0.20% L‐Ile and 0.25% L‐Val (excess LIV). The basal diet was formulated to contain 0.90% standardized ileal digestible Lys and added with crystalline L‐Lys, L‐Thr, DL‐Met, L‐Trp, L‐Leu, L‐Ile, L‐His and L‐Val to create essential AA:Lys ratios close to an ideal protein for growing pigs. All pigs were fed the same amount of feed twice a day (average, 3.42× the requirement of NEm). Blood samples were collected at 2.5 (absorptive) and 11.0 h (post‐absorptive) post‐prandial to analyse SC of AA. Excess of either Leu or LIV did not affect growth rate nor feed conversion. Excess Leu increased Leu SC and decreased Ile and Val SC (p < 0.05) at both absorptive and post‐absorptive phases, but excess LIV restored the SC of Ile and Val. The SC of other essential AA was not affected by excess of either Leu or LIV. The SC of all AA during absorptive, on average, was about two times higher than that of post‐absorptive phase. These results suggest that the reduced availability (SC) of Ile and Val in pigs consuming excess Leu diets is attributed to a reduced absorption and increased cellular degradation rates of them.     

Detection and characterization of quantitative trait loci for meat quality traits in pigs.

In an experimental cross between Meishan and Dutch Large White and Landrace lines, 785 F2 animals with carcass information and their parents were typed for molecular markers covering the entire porcine genome. Linkage was studied between these markers and eight meat quality traits. Quantitative trait locus analyses were performed using interval mapping by regression under two genetic models: 1) the line-cross approach, where the founder lines were assumed to be fixed for different QTL alleles and 2) a half-sib model where a unique allele substitution effect was fitted within each of the 38 half-sib families. The line-cross approach included tests for genomic imprinting and sex-specific QTL effects. In total, three genome-wide significant and 26 suggestive QTL were detected. The significant QTL on chromosomes 3, 4, and 13, affecting meat color, were only detected under the half-sib model. Failure of the line-cross approach to detect the meat color QTL suggests that the founder lines have similar allele frequencies for these QTL. This study provides information on new QTL affecting meat quality traits. It also shows the benefit of analyzing experimental data under different genetic and statistical models.     

生长育肥猪胴体品质和肉质演变规律的研究

以长×荣杂交猪为对象 ,研究营养水平和性别对生长育肥猪胴体品质和肉质演变规律的影响。设高低两个营养水平 ,分别为 2 0、35、5 0、80、10 0kg进行屠宰试验 ,测定了公母猪肌肉水分、肌间脂肪、失水率、肉色、肌纤维面积、胶原蛋白、次黄嘌呤随体重的变化规律。试验结果证明 ,2 0～5 0kg阶段 ,高低水平组间水分、失水率、肌间脂肪差异不显著 (P >0 .0 5 ) ,5 0～ 10 0kg阶段出现分化 ,到 10 0kg屠宰时 ,高低水平组水分、失水率差异显著 (P <0 .0 5 ) ;肌间脂肪差异极显著 (P <0 .0 1) ;肌纤维面积生长规律呈“S”型 ,35～ 5 0kg时生长速度最大 ,5 0～ 80kg时下降 ,80～ 10 0kg又上升 ;胶原蛋白、次黄嘌呤随体重增加而升高 ,到 80kg时含量趋于稳定 ,高低水平间无显著差异(P >0 .0 5 ) ;全期高低水平间肉色差异不显著 (P >0 .0 5 ) ;性别对肌间内脂肪和失水率影响较大 ,10 0kg时 ,失水率公母间差异极显著 (P <0 .0 1) ,肌间脂肪差异显著 (P <0 .0 5 )。     

Evaluation of Duroc- vs. Pietrain-sired pigs for carcass and meat quality measures

Crossbred progeny sired by either Duroc or Pietrain boars, normal for the ryanodine receptor gene, were evaluated for carcass composition and meat quality. Boars from each breed were mated to Yorkshire or F1 Yorkshire-Landrace females. A total of 162 off-spring was evaluated for carcass and meat quality traits at a common age (approximately 26 wk of age). Duroc-sired progeny had heavier (108.0 vs. 103.0 kg, P < 0.001) and longer carcasses (86.9 vs. 84.8 cm, P < 0.01), whereas Pietrain-sired pigs had less backfat at the first rib (44.6 vs. 47.7 mm, P < 0.01), last lumbar vertebrae (20.9 vs. 23.0 mm, P < 0.05), and 10th rib (23.0 vs. 25.5 mm, P < 0.01). No difference between Pietrain and Duroc progeny was detected for fat depth at the last rib (27.8 vs. 28.8 mm, respectively). Pietrain progeny had a higher percentage of lean at slaughter (52.6 vs. 50.7, P < 0.05) and higher dressing percentage (74.0 vs. 73.1, P < 0.01). Primal cut weights were collected with Pietrain progeny having a greater percentage of carcass as ham (23.0 vs. 22.4, P < 0.01) and loin (21.6 vs. 21.2, P < 0.05), whereas Duroc progeny had a higher percentage of belly weight (12.0 vs. 11.7, P < 0.05). Percentages of Boston butt (8.8 vs. 9.0) and picnic shoulder (9.9 vs. 9.9) were similar for Duroc vs. Pietrain progeny. Total weight of these five primal cuts, as a percentage of carcass weight, was higher for Pietrain progeny (75.2 vs. 74.3, P < 0.01). With heavier carcass weight, Duroc progeny had greater primal cut weights as a function of age. Subjective meat quality scores for color, marbling, and firmness (1 to 5 scale) were more favorable for Duroc-sired progeny. Furthermore, chops from Duroc progeny had higher 24-h pH (5.53 vs. 5.48, P < 0.001) and Minolta a* (17.33 vs. 17.04, P < 0.05) with less percentage drip loss (2.88 vs. 3.80, P < 0.001). No differences were detected between Duroc- and Pietrain-sired progeny for Minolta L* (54.77 vs. 55.37) or b* (7.58 vs. 7.58) objective color scores, percentage cooking loss (28.63 vs. 29.23), or Warner-Bratzler shear force (6.94 vs. 7.11 kg). Both sire breeds have beneficial traits that can be utilized in commercial pork production and merit further study.