含双低菜粕的肉鸡日粮适宜能量水平研究

选1日龄艾维茵肉用仔鸡300羽,按体重相对一致的原则随机分成4组。各组中试验前期(0～3周)“华双3号”双低菜粕等氮替代日粮豆粕的比例为50%,试验后期(4～6周)替代比例为62.5%。每阶段各组试验日粮蛋能比保持一致,前期为3.3g/MJ,后期为3.78g/MJ。试验前期各试验组日粮代谢能值分别为11.27MJ/kg、11.7MJ/kg、12.12MJ/kg、12.54MJ/kg;后期代谢能值分别为11.7MJ/kg、12.12MJ/kg、12.54MJ/kg、12.96MJ/kg。39d的饲养结果表明:无论是在试验前期还是试验后期,第2、3、4组试验鸡的体增重都极显著高于日粮能量浓度最低的第1组(P<0.01),但2、3、4组试验鸡之间的体增重差异不显著。从全期的饲料利用率来看,第4组的饲料利用率最好,与试验1、2组相比差异极显著(P<0.01),也显著高于试验3组(P<0.05);同时第2、3组均极显著地优于第1组(P<0.01)。在经济效益方面,试验2组每只毛利分别比试验1、3、4组高1.03元、0.09元和0.12元。从本次试验来看,在肉鸡生长前期、后期以双低菜粕等氮替代日粮豆粕比例分别为50%和62.5%时,日粮适宜的代谢能值为0～3周龄12.12～12.54MJ/kg,4～6周龄12.12～12.54MJ/kg。     

杜洛克猪生长和胴体性状的遗传参数 表型参数 选择指数的研究

本文对杜洛克猪的主要生长和胴体性状作了遗传、表型参数的研究。生长测定805头猪,胴体测定279头猪,结果表明前期(25—6c千克阶段)日增重596克,后期(60—90千克阶段)787克,全期平均668克,三个阶段的饲料利用率分别为2.57,3.27和2.91。宰前体重90千克时,屠宰率71.42％,胴体长79.22厘米,皮厚0.20厘米。平均膘厚1.85厘米,瘦肉率62.0％,眼肌面积31.26厘米~2,后腿率32.59％。遗传力估测为:三个阶段日增重分剐为0.32,0.48和0.29,屠宰率0.51,胴体长0.68,平均瞟厚0.53,瘦肉率0.61,眼肌面积0.31,后腿率0.57。利用本次估计的参数制订两个综合选择指数,选择指数1包括日增重、背膘厚和瘦肉率三个性状;指数2还包括饲料利用率性状。并对两个指数的选择效果进行了估计。     

α-半乳糖苷酶对黄羽肉鸡生长性能和养分利用率的影响

本文旨在研究日粮中添加不同水平a-半乳糖苷酶对黄羽肉鸡生长性能和养分利用率的影响.选择500羽8 日龄快速生长型黄羽肉鸡,随机分为5个组,每组4个重复,每个重复25羽.试验分为前期(8～28 日龄)和后期(29～56日龄)2个阶段.试验I组饲喂正对照日粮(ME:前期11.92 MJ/kg,后期12.34 MJ/kg),试验Ⅱ组饲喂负对照日粮(ME:前期11.71 MJ/kg,后期12.13 MJ/kg),试验Ⅲ～V组分别饲喂在负对照日粮中添加100、150和200 mL/tα-半乳糖苷酶的试验日粮.结果表明:各组问肉鸡的平均日增重、日采食量、前期和全期料重比以及全期存活率均无显著差异(P>0.05),但添加α-半乳糖苷酶制剂的各试验组后期料重比均低于正对照组(P>0.05)和负对照组(P<0.05),全期料重比也都低于正、负对照组(P>0.05);3个加酶组的干物质、粗蛋白质、能量表观代谢率和表观代谢能与正、负对照组相比无显著差异(P>0.05);3个加酶组的缬氨酸、亮氨酸和赖氨酸表观消化率显著高于负对照组(P<0.05),但总氨基酸表观消化率各组间差异不显著(P>0.05).由此可知,在代谢能降低0.21 MJ/kg的玉米-豆粕-杂粕型日粮中添加α-半乳糖苷酶制剂可降低黄羽肉鸡后期料重比,提高郎分氨基酸表观利用率.     

如何提高育肥猪出栏率

提高肉猪生产水平和生产效益的关键在于提高出栏率,力争使生长育肥猪在6～7月龄(育肥4～5月)体重达到95～120kg屠宰、上市,为此应采取一整套的科学饲养管理措施. 1 能量水平 在不限量饲养的条件下,肉猪有自动调节进食而保持进食能量守恒的能力,因而日粮能量浓度在一定范围内变化,对肉猪的生长速度、饲料利用率和胴体肥瘦程度的影响不明显.但当日粮能量浓度降至10.8MJ/kg消化能时,对肉猪增重、饲料利用率和胴体品质有较明显的影响,生长速度和饲料利用率降低,胴体瘦肉率提高,但育肥期延长.而提高日粮能量浓度,能提高增重速度和饲料利用率,但胴体较肥.     

日粮能量水平对产蛋高峰期蛋鸡生产性能的影响

为研究产蛋高峰期蛋鸡代谢能需要量,试验选择220只24周龄尼克粉鸡随机分为5组,分别饲喂代谢能水平为10.07,10.63,10.91,11.41,11.78 MJ/kg的日粮。结果表明:在试验前期(25～38周)、后期(39～51周)和全期(25～51周)随着日粮代谢能水平的升高,各组蛋重、产蛋率、产蛋量、能量采食量差异不显著(P>0.05);采食量、料蛋比逐渐降低;随着日粮代谢能水平的升高蛋鸡增重有增加的趋势,但组间差异不显著(P>0.05)。说明在10.07～11.78 MJ/kg能量浓度范围内,提高日粮能量水平可以降低蛋鸡采食量和料蛋比,但对能量采食量影响不大。     

日粮不同蛋能比水平对黄羽肉鸡器官指数和血清学指标的影响

为研究日粮不同蛋能比对黄羽肉鸡器官指数和血清学指标的影响,试验前期(1～25 d)选用1 d改良型岭南黄鸡2 000羽,后期(46～65 d)选用46 d黄鸡1 920羽,随机分成4组,分别饲喂四种蛋能比水平的日粮,结果表明:黄鸡前期胰腺指数第Ⅳ组比第Ⅰ组高16.1%(P<0.05),后期黄鸡活重、各器官重和指数各组差异不显著;黄鸡前期和后期免疫器官重与免疫器官指数各组均无显著性差异;黄鸡前期第Ⅲ组血清中总蛋白、球蛋白水平分别比第Ⅱ组高21.1%和30.1%(P<0.05),第Ⅱ组尿素氮显著升高(P<0.05),后期母鸡血清中谷草转氨酶活性第IV组显著高于第I、Ⅲ组(P<0.05).综合分析黄鸡日粮中的适宜蛋能比水平前期为16.95 g/MJ,后期公母鸡均为13.61 g/MJ.     

莱可多巴胺对育肥猪生长性能及胴体品质的影响

本试验研究了饲料中添加莱可多巴胺(Ractopamine,RAC)对育肥猪(60-90kg体重)生长性能、胴体品质和肉质的影响.试验动物为30头(公母各半)DVI系的二元杂交商品猪,随机分为3组,RAC的添加水平分别为0、10和20mg/kg.试验猪单栏饲养,自由采食和自由饮水.基础日粮含DE13.08MJ/kg、CP16.3%、赖氨酸0.94%.试验结果表明:RAC对猪的日增重、料肉比和胴体瘦肉率有显著改进.随着RAC添加水平的增加,改进幅度增大,以添加20mg/kg效果最佳,日增重比对照组提高15.7%(P<0.05),饲料转化效率提高17.7%(P<0.05),胴体瘦肉率提高5、5%(P<0.05).RAC的使用对肉质没有显著影响.     

“双低”菜籽饼等氮替代豆粕饲喂生长肥育猪试验

112头杜×湖断奶仔猪随机分成4组，1组为对照组，2、3、4组分别以“中双4号”“双低”菜籽饼等氮替代对照组中25％、50％及75％的豆粕，26—90kg期间进行饲养试验。结果表明，替代25％的2组平均日增重、饲料利用率、胴体品质及肌肉品质均达到或超过对照组，但差异不显著（P＞0.05）。替代50％的3组上述指标略低于对照组，但差异不显著（P＞0.05）。替代75％的4组平均日增重在试验前期极显著低于2组和1组（P＜O.01），显著低于3组（P＜O.05）；试验后期各组间差异不显著（P＞0.05）；胴体瘦肉率极显著低于2、1组（P＜O.01），显著低于3组（P＜0.05），但肌肉品质未受影响。各组背最长肌与肝脏均未检出ITC和OZT。     

限饲对商品肉猪生产性能影响的研究

采用２×３×２因子设计，研究了两种限饲方式，三种限饲幅度以及在不同限饲幅度下加粗料与否，对商品肉猪胴体瘦肉率、肉质、增重速度、饲料利用效率的影响。结果表明，两种限饲方式的胴体瘦肉率虽比对照组高，但差异不显著。前期以限饲７５％较好，后期限饲则以８５％为宜。饲粮中粗纤维水平超过１３％～１７％对提高瘦肉率降低背膘厚有利，但对增重与饲料利用率有损无益。氮沉积随体重的增加商下降，而在体重５０千克左右最高（３４％～３９％）。     

植物甾醇对肉鸡生产性能的影响

日粮中分别添加0、5、10、20、40和80 mg/kg植物甾醇,研究其对肉仔鸡生产性能的影响。结果表明,20、40 mg/kg植物甾醇添加组能提高前期(0~21 d)日增重,其中40 mg/kg组达显著水平(P<0.05);5、10、40和80 mg/kg组均能提高后期(22~42 d)和全期(0~42 d)日增重(P>0.05)。20、40 mg/kg组能提高前期平均重,其中40 mg/kg组达极显著水平(P<0.01);5、10、40和80 mg/kg添加组均能提高后期平均重(P>0.05)。40 mg/kg植物甾醇添加组有提高前期、后期及全期饲料转化效率的趋势(P>0.05)。各组间死淘率差异均不显著(P>0.05)。从增重和饲料转化效率来看,肉仔鸡饲料中添加40 mg/kg的植物甾醇效果最好。     

日粮代谢能和赖氨酸水平对AA肉鸡生长性能和屠宰性能的影响

为了研究日粮不同代谢能和赖氨酸水平对AA肉鸡生长性能和屠宰性能的影响,试验选用160只1日龄AA公雏,随机分为5个处理,每个处理32个重复,每重复1只鸡,实行单笼饲养。试验采用2因子(代谢能和赖氨酸)×2水平(低于和高于对照组)随机区组设计,设1个对照组(代谢能参照NRC,1994),2个代谢能水平分别为12.97、13.81MJ/kg;2个赖氨酸水平0～3周龄分别为1.0%、1.2%,4～6周龄分别为0.9%、1.1%,对照组代谢能水平0～6周龄为13.39MJ/kg,赖氨酸水平0～3周龄为1.1%,4～6周龄为1.0%。42日龄屠宰,试验结果表明:①日粮代谢能水平从12.97MJ/kg提高到13.81MJ/kg,肉鸡平均体重增加12.67%,饲料转化率升高7%(P<0.01);日粮赖氨酸水平提高20%,体重显著增加12.38%(P<0.05),饲料转化率升高3.84%(P<0.01);日粮代谢能和赖氨酸对饲料转化率有显著的互作效应(P<0.05);②随着代谢能水平的提高,屠体重、全净膛重、胸肌重、腿肌重、腹脂重和腹脂率相应提高,高能组显著高于中、低能组(P<0.05),赖氨酸水平对屠体重、全净膛重、胸肌重和胸肌率产生极显著的影响(P<0.01),与低赖氨酸组相比,高赖氨酸日粮组肉鸡屠体重增加12.33%、全净膛重增加12.62%、胸肌重增加28.53%、胸肌率提高3.11%,代谢能和赖氨酸水平对肉鸡腹脂重有显著的互作效应(P<0.05);③日粮代谢能水平为13.81MJ/kg,赖氨酸水平0～3周龄为1.2%、4～6周龄为1.1%时AA肉鸡获得最佳生产性能和屠宰性能,与实际生产中应用的NRC(1994)代谢能和赖氨酸水平相比,AA肉鸡多赢利1.44元/只。     

不同净能水平和赖氨酸净能比的低蛋白日粮对肥育猪生长性能和胴体品质的影响

选用61.08 kg杜×长×大三元杂交猪540头,随机分为9个处理,每处理6个重复,每重复10头猪,公、母各半。采用3×3两因素设计,日粮蛋白水平降低4个百分点,净能为9.83、10.04、10.25 MJ/kg,赖氨酸净能比为0.76、0.84、0.91 g/MJ,研究净能和赖氨酸净能比对肥育猪生长性能和胴体品质的影响。结果表明:在60~100 kg阶段,10.04 MJ/kg净能组的ADG显著高于9.83 MJ/kg组的(P<0.05);赖氨酸净能比为0.84 g/MJ组的ADG显著高于0.76 g/MJ组(P<0.05);二者互作不影响生长性能和胴体品质(P>0.05),综合评定在60~100 kg阶段,猪的低蛋白日粮净能水平和赖氨酸净能比分别为10.04 MJ/kg和0.84 g/MJ为宜。     

Effect of liquid feeding weaned pigs on growth performance to harvest

Four experiments were undertaken to examine the effect of feeding postweaning diets as dry pelleted feed, fresh liquid feed, acidified liquid feed, and fermented liquid feed on pig performance from weaning (26 d) to harvest. In Exp. 1 (n = 12 replicates) and 2 (n = 10 replicates), the treatments were 1) dry pelleted feed and 2) fresh liquid feed. In Exp. 1, 2 kg of starter diet (16.7 MJ of DE/kg and 1.6% lysine) per pig and 5 kg of transition diet (16.7 MJ of DE/kg and 1.5% lysine) per pig followed by a weaner diet (14.0 MJ of DE/kg and 1.36% lysine) were offered to 27 d after weaning. In Exp. 3 (n = 8 replicates), the treatments were 1) dry pelleted feed, 2) fresh liquid feed, and 3) acidified liquid feed. In Exp. 4 (n = 8 replicates), the treatments were 1) dry pelleted feed, 2) acidified liquid feed, and 3) fermented liquid feed. In Exp. 2, 3, and 4, 3 kg of starter diet (16.1 MJ of DE/kg and 1.74% lysine) per pig and 6 kg of transition diet (15.3 MJ of DE/kg and 1.5% lysine) per pig followed by a weaner diet (14.0 MJ of DE/kg and 1.36% lysine) was offered to 27 d after weaning. All treatments were balanced for boars and gilts and diets were offered for ad libitum consumption. Acidified liquid feed was produced by adding lactic acid to the liquid feed so that its pH was decreased to 4.0. Fermented liquid feed was produced by adding an inoculum of Lactococcus lactis subsp. cremoris 303 (1.3%, vol/wt) to the first mix. In Exp. 1, ADG from weaning to d 27 after weaning was 338 and 286 g/d (SEM = 10; P < 0.01) and DM gain/feed in the same period was 888 and 594 g/kg (SEM = 23.1; P < 0.001) for dry pelleted feed and fresh liquid feed, respectively. In Exp. 2, ADG was 391 and 352 g/d (SEM = 6.4; P < 0.01) and DM gain/feed was 856 and 642 g/kg (SEM = 9.9; P < 0.001) for dry pelleted feed and fresh liquid feed, respectively, during the period from weaning to d 27 after weaning. In Exp. 3, ADG was 408, 416, and 433 g/d (SEM = 12.7; P > 0.05) and DM gain/feed was 865, 755, and 789 g/ kg (SEM = 14.5; P < 0.001) for dry pelleted feed, fresh liquid feed, and acidified liquid feed, respectively. In Exp. 4, ADG was 361, 389, and 347 g/d (SEM = 13.2; P = 0.11) and DM gain/feed was 888, 749, and 733 g/ kg (SEM = 15.8; P < 0.001) for dry pelleted feed, acidified liquid feed, and fermented liquid feed, respectively, during the period from weaning to d 27 after weaning. It is concluded that although feeding acidified liquid feed may have some merit in the first 27 d after weaning, this benefit is lost in the subsequent period. No benefit arose from feeding fresh liquid feed or fermented liquid feed. Growth performance from d 28 after weaning to harvest was not improved by any liquid feed treatment.     

后备荣昌母猪适宜消化能和赖氨酸需要量研究

旨在探讨研究35～55 kg后备荣昌母猪适宜日粮消化能(DE)与表观可消化赖氨酸(ADLys)水平。选用(34.45±4.53)kg后备荣昌母猪216头,随机分为12个处理,每个处理6个重复,每个重复3头。采用3×4因子设计,日粮DE分别为11.72、12.34和12.97 MJ/kg,ADLys分别为0.43%、0.53%、0.63%和0.73%。结果表明:随着日粮DE水平的提高,试验猪日增重显著提高(P0.05),饲料增重比显著降低(P0.05),P2背膘厚显著增加(P0.01),母猪发情率呈现上升趋势(P0.1)。日粮Lys水平提高使血清尿素氮含量呈现上升趋势(P0.1)。在本试验条件下,35～55 kg后备荣昌母猪适宜日粮DE和ADLys水平分别为12.97MJ/kg和0.43%。     

Effect of apparent ileal digestible lysine to energy ratio on performance of finishing pigs at different dietary metabolizable energy levels

A study with a total of 96 crossbred barrows and gilts fed ad libitum in a body weight range of 56-110 kg was carried out in order to investigate whether the optimum ratio of apparent ileal digestible lysine : energy (ME) depends on the energy density of the diet. Dietary treatments were ratios of 0.34, 0.42, 0.50 and 0.58 g digestible lysine/MJ ME either at an energy density of 13 or 14 MJ ME. Body weight gain as well as feed and ME conversion rate were improved when lysine : ME ratio increased from 0.34 to 0.50, whereby all parameters showed a significant ratio x sex interaction. Feed intake and feed conversion rate were higher at a dietary energy density of 13 MJ ME than at an energy density of 14 MJ ME but energy density did not influence daily growth rate, ME intake and ME conversion rate. Fat area above eye muscle and meat : fat ratio were lower and eye muscle area and lean percentage were higher at a ratio of 0.42 compared with a ratio of 0.34. Daily feed intake, body weight gain, feed conversion rate and parameters of fatness were higher in barrows than in gilts. Conversely, gilts had higher eye muscle area and lean percentage. Optimum ratio for body weight gain, feed and ME conversion rate calculated by exponential regression analysis were 0.42-0.43 in barrows. In gilts, feed and ME conversion rate were optimized at a ratio of 0.53 and 0.54. Because growth showed a linear response to increasing digestible lysine : ME ratios, optimum ratio for daily gain in gilts is considered to be at least 0.58.     

The feeding of ad libitum dietary protein to organic growing-finishing pigs

The effects of three dietary protein levels on growth, meat, and carcass traits were studied in organic pigs fed a three-phase diet. Assuming lysine was the first limiting amino acid, feeds were formulated to ileal digestible (ID) lysine content, with the ID lysine:crude protein ratio set at a constant of 4%. Feeds were also formulated to an isocaloric rate (net energy: 9.4 MJ/kg during the first feeding phase, 9.25 MJ/kg during the second feeding phase and 9.1 MJ/kg during the finisher phase), with a high (HP), a medium (MP) or a low (LP) protein content ranging from 20% to 14% crude protein (CP). ID lysine content of the LP and MP feed was, respectively, 80% and 90% of the ID lysine content of the HP feed. The nutrient formulation of the HP feed was similar to nutrient levels commonly used in conventional Belgian pig farming. From 20 to 40 kg liveweight, the pigs showed better feed conversion ratios, with an increasing dietary protein concentration (r(2)=0.84). This effect was not observed in the second and third phases, although a significant effect of protein concentration on voluntary feed intake in the second phase did occur (P=0.018), probably as a compensation for the lower protein concentration in the LP diet. Analysis of the carcasses showed a lower meat percentage with lower protein concentration (P<0.05), whereas influences on meat quality were limited. It was concluded that whereas during the first phase of growth, higher protein concentration leads to better performance, from the second phase onwards (45 kg), at least with isocaloric diets, a decrease in protein content (corresponding to a 10% reduction in dietary ID lysine levels compared to conventional pig fattening) may be used in organic growing-finishing pig nutrition.     

日粮能量蛋白质与赖氨酸水平对5～10周龄扬州鹅生长性能的影响

试验旨在研究日粮不同能量蛋白质水平和赖氨酸水平对5~10周龄扬州鹅生长性能的影响。试验采用3×4二因子设计,3个能量蛋白质水平分别为:10.83 MJ/kg、15%,11.29 MJ/kg、16%,11.75 MJ/kg、17%,其蛋白质能量比均约为14 g/MJ,4个赖氨酸水平分别为:0.65%、0.80%、0.95%和1.10%。结果表明:①日粮能量蛋白质水平对6、8、10周龄扬州鹅体重没有显著影响(P>0.05),日粮赖氨酸水平显著影响扬州鹅6、8、10周龄体重(P<0.05),但能量蛋白质水平和赖氨酸水平对其没有显著交互作用(P>0.05);②日粮能量蛋白质水平显著影响5~10周龄扬州鹅的平均日采食量和料重比(P<0.05),赖氨酸水平显著影响平均日增重和平均日采食量(P<0.05),能量蛋白质水平和赖氨酸水平对其没有显著交互作用(P>0.05);③中能蛋水平和最低赖氨酸水平下,5~10周龄扬州鹅可获得较佳生长性能。试验认为5~10周龄扬州鹅能量蛋白质和赖氨酸适宜需要量分别为11.29 MJ/kg、16%和0.65%。     

Interrelationships between dietary lysine, sex, and porcine somatotropin administration on growth performance and protein deposition in pigs between 80 and 120 kg live weight

Sixty male and 60 female crossbred pigs were allocated to an experiment to investigate the effects of porcine somatotropin (pST) administration (0 or 6 mg/d) and dietary lysine content on growth performance, tissue deposition, and carcass characteristics over the live weight range of 80 to 120 kg. Pigs receiving pST were given diets containing 6.9, 7.8, 8.8, 9.7, 10.6, or 11.5 g lysine/kg, whereas control pigs received diets containing 4.8, 5.8, 6.9, 7.8, 8.8 or 9.7 g lysine/kg. These dietary levels ranged from 0.40 to 0.70 g available lysine/MJ of DE for pST-treated pigs and from 0.28 to 0.58 g available lysine/MJ of DE for control pigs. Pigs were individually housed in pens, and there were five replicates of each treatment. All diets contained 14.5 MJ of DE/kg and were offered for ad libitum consumption to pigs between 80 and 120 kg live weight. Growth rate increased exponentially and food conversion ratio (FCR) decreased exponentially with increasing levels of lysine. In addition, there was a significant sex x pST interaction such that pST reduced the sex difference in FCR. Growth rate was faster in boars than in gilts and was increased by pST at the higher levels of dietary lysine. Similarly, FCR was lower for boars than for gilts and was decreased by pST at the higher dietary lysine levels. The optimum growth rate and FCR were defined as the lysine level at which growth rate and FCR were 95% and 105%, respectively, of the lysine plateau. The optimum growth rate and FCR were achieved at similar dietary lysine contents and were approximately 0.35 and 0.52 g available lysine/MJ of DE for control and pST-treated pigs, respectively. Protein deposition in the carcass increased exponentially with increasing dietary lysine level, was higher in boars than in gilts, and was increased by pST at the higher dietary lysine contents. Sex had no effect on dietary lysine required to maximize protein deposition. The dietary lysine contents required to ensure 95% of plateau protein deposition of 104 and 153 g/d were 0.39 and 0.55 g available lysine/MJ of DE for control and pST-treated pigs, respectively. The increase in lysine requirement with pST seems to be commensurate with the increase in protein deposition.     

Requirement of true ileal digestible threonine of growing and finishing pigs

Ninety-six crossbred barrows and gilts were used to investigate the optimum supply of true ileal digestible threonine for growing (approximately 35-65 kg body weight) and finishing (approximately 65-110 kg body weight) pigs. For this purpose, according to a bifactorial arrangement in the grower as well as in the finisher phase four dietary threonine levels were combined with two dietary levels of lysine. Measurement criteria were body weight gain, feed intake, feed conversion rate and carcass characteristics. In the grower stage at the lower lysine level daily gain increased numerically (p < 0.1) and the feed to gain ratio decreased significantly with an increasing dietary true ileal digestible threonine concentration. Increasing the true ileal digestible lysine concentration of the diet from 7.8 to 9.2 g/kg increased average daily gain in the grower stage significantly from 815 to 855 g and decreased the feed to gain ratio significantly. In finishing pigs, daily gain and feed to gain ratio were significantly improved by an increasing dietary true ileal digestible threonine concentration from 821 to 902 g and from 3.14 to 2.94 kg/kg, respectively, but not by the differing lysine supply. As in the grower stage, barrows consumed more feed than gilts at similar growth rates and this resulted in a significantly reduced feed to gain ratio in gilts compared with barrows. The requirements of true ileal digestible threonine for optimize both, daily gain and feed to gain ratio, as derived by the broken-line model were 10.3 g/animal and day for growing and 10.7 g/animal and day for finishing pigs respectively.     

Effect of dietary lysine level and environmental temperature during the finishing phase on the intramuscular fat content of pork

This study was designed to investigate the effects of dietary lysine level on the intramuscular fat content of the longissimus in finishing pigs reared at two environmental temperatures. Seventy-two hybrid gilts were individually penned and given ad libitum access to either a diet formulated to meet their lysine requirement (6.4 g/kg lysine) or a lysine-deficient diet (4.8 g/kg). Pigs were held at one of two environmental temperatures (thermoneutral [18 degrees C] or hot [32 degrees C]). The study was carried out between approximately 90 and 126 kg live weight; pigs in the thermoneutral and hot environments were on test for 5 and 7 wk, respectively. There were no interactions between dietary lysine level and environmental temperature. Dietary lysine content did not influence feed intake or average daily gain; however, pigs on the lysine-deficient diet had a poorer gain:feed ratio than those fed to requirement (P < .01). High environmental temperature decreased feed intake (P < .001) and average daily gain (P < .01) but improved gain:feed ratio (P < .01). Backfat at the 10th rib was increased and loin eye area and estimated percentage lean in the carcass were decreased for pigs on the lysine-deficient diet. The higher environmental temperature resulted in an increase in carcass length but had no effect on other carcass measurements or intramuscular fat. Feeding the lysine-deficient diet resulted in an increase of .55 percentage unit in longissimus intramuscular fat content (P < .01); however, there was no difference in subjective marbling scores between the diets. Warner-Bratzler shear force values were not affected by dietary lysine level or environmental temperature. Results from this study suggest that feeding of lysine-deficient diets at the end of the finishing period can increase intramuscular fat deposition under thermoneutral and hot conditions.