Genetic and environmental parameters for steer ultrasound and carcass traits

Carcass measurements for weight, longissimus muscle area, 12-13th-rib fat thickness, and marbling score, as well as for live animal measurements of weight at the time of ultrasound, ultrasound longissimus muscle area, ultrasound 12-13th-rib fat thickness, and ultrasound-predicted percentage ether extract were taken on 2,855 Angus steers. The average ages for steers at the time of ultrasound and at slaughter were 391 and 443 d, respectively. Genetic and environmental parameters were estimated for all eight traits in a multivariate animal model. In addition to a random animal effect, the model included a fixed effect for contemporary group and a covariate for measurement age. Heritabilities for carcass weight, carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound weight, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.48, 0.45, 0.35, 0.42, 0.55, 0.29, 0.39, and 0.51, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, carcass marbling score and ultrasound-predicted percentage ether extract, and carcass and ultrasound weight were 0.69, 0.82, 0.90, and 0.96, respectively. Additional estimates were derived from a six-trait multivariate animal model, which included all traits except those pertaining to weight. This model included a random animal effect, a fixed effect for contemporary group, as well as covariates for both measurement age and weight. Heritabilities for carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.36, 0.39, 0.40, 0.17, 0.38, and 0.49, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, and carcass marbling and ultrasound-predicted percentage ether extract were 0.58, 0.86, and 0.94, respectively. The high, positive genetic correlations between carcass and the corresponding real-time ultrasound traits indicate that real-time ultrasound imaging is an alternative to carcass data collection in carcass progeny testing programs.     

The influences of weaning age and weight on carcass traits and meat quality of pigs

The purpose of this study was to establish the effects of weaning age and weight on pigs, and their interaction with carcass traits and meat quality. A total of 468 piglets were obtained from 57 sows and four boars and grouped by age at weaning (D21, 18–24 days; D28, 25–32 days). Each weaning group was subdivided into three weight groups (L, M and H) according to weaning weight. The D28 group had heavier carcass weight, redness and yellowness, but had lower marbling scores and less drip loss than the D21 group (P < 0.05). The pigs with a light weight at weaning had higher carcass weights and lower yellowness than did pigs with a medium or heavy weight at weaning (P < 0.05). Weaning age was found to have a negative correlation with drip loss, while weaning weight was negatively correlated with carcass weight and drip loss (P < 0.05). We concluded that carcass and meat quality traits in pigs were significantly related to their age and weight at weaning. Therefore, we find that piglet weaning age and weight are no less important than post‐weaning growth performance and behavior, with regard to carcass traits and meat quality.     

Effect of dietary phosphorus on finishing steer performance, bone status, and carcass maturity.

Yearling crossbred steers (n = 60; 386 kg) were individually fed in a completely randomized experimental design to determine their P requirement. Treatments were in a factorial arrangement with two levels of Ca (.35 or .70% of DM) and five concentrations of P (.14, .19, .24, .29, or .34% of DM). The finishing diet consisted of 34.5% dry-rolled corn, 22.5% brewers grits, 22.5% corn bran, 7.5% ground corncobs, 5% molasses, 3% fat, and 5% supplement. Supplemental P was provided as monosodium phosphate and Ca as limestone. Ash content was determined on the first phalanx bone from the lower front legs following slaughter, and rib bone breaking strength was determined with an Instron Universal Testing Machine. Carcass maturity and shear force were also evaluated on wholesale rib cuts. Because no interactions between Ca and P levels were detected, only main effects are presented. Daily gain, DMI, and feed efficiency were not affected by dietary P concentration or P intake. Bone ash (g or g/100 kg BW) and rib bone breaking strength were also unaffected by dietary P. Feeding .7% Ca decreased (P<.06) ADG and efficiency compared with feeding .35% Ca. Neither dietary Ca nor P had a significant effect on tenderness (shear force), skeletal maturity, or overall maturity. These results indicate that the P requirement for finishing yearlings is .14% of diet DM or less and that supplementing P above levels supplied by basal ingredients in many grain-based finishing diets is not necessary.     

果胶酶对肉仔鸡生长性能及屠体性状的影响

试验选用 1日龄商品艾维茵肉仔鸡 4 32只。完全随机分为 2 4圈 ,每圈 18只 ,地面平养 5 4天。试验分为 4个处理 ,每个处理 6圈 ,分别饲喂 4种不同的日粮 ,即对照组 (基础日粮组 )、添加金霉素 5 0mg/kg日粮组、添加果胶酶 5 0 0mg/kg日粮组、添加果胶酶 10 0 0mg/kg日粮组。试验结果表明 ,果胶酶在肉仔鸡饲养前 2 1日龄的促生长效果显著 ,平均日增重 (ADG)和平均日采食量 (ADFI)均比对照组有显著增加 (P <0 .0 5 ) ,饲料转化率显著提高 (P <0 .0 5 ) ,与抗生素效果相当 ;2 1～ 4 2日龄时仅 5 0 0mg/kg果胶酶组出现ADFI比对照组显著增加 (P <0 .0 5 ) ,但饲料转化率较其它各组显著降低 (P <0 .0 5 )。 4 2～ 5 4日龄时 5 0 0mg/kg果胶酶组ADG显著高于抗生素组 (P <0 .0 5 ) ,饲料转化率显著提高 (P <0 .0 5 )。饲养全期 ,添加抗生素或果胶酶组ADG与对照组差异显著 (P <0 .0 5 ) ,ADFI仅5 0 0mg/kg果胶酶组与对照组有显著差异 (P <0 .0 5 )。     

Chromium propionate improves performance and carcass traits in broilers

There is evidence to suggest that poultry may have a dietary requirement for metabolically available chromium (Cr) that exceeds the amount provided through wheat soybean meal diets. The objective of the present study was to investigate the effects of dietary supplemental organic Cr from Cr propionate at different dose levels (control = 0 μg/kg, T1 = 200 μg/kg, T2 = 400 μg/kg) on the growth performance, carcass traits, and meat quality of broilers. Weight gain and feed intake of each treatment were recorded at the start and after 14, 28 and 35 d, and feed conversion ratios (FCR) were calculated accordingly. At 35 d of age, birds were randomly selected and euthanized for carcass evaluation. Results of the first trial indicate that both Cr propionate treatments increased final body weight (P < 0.05), feed efficiency (P < 0.05) and body weight gain (P < 0.0001). Furthermore, Cr propionate supplementation improved (P < 0.0001) all carcass characteristics. Interestingly, with increased Cr dosage, carcass yield, dressing percentage and breast meat yield increased linearly (P < 0.0001). The second study reveals that the feed intake in the control group was significantly higher compared to both Cr propionate supplemented groups (T1 & T2). Furthermore, the Cr propionate supplemented T2 group displayed a significantly lower FCR than the control and T1 group (P = 0.027). Finally, Cr propionate supplementation increased the dressing percentage compared to control birds (P < 0.0001). In the third experiment, Cr propionate supplementation (T1 & T2) increased final body weight and decreased FCR compared with the control treatment. These effects were highly significant (P < 0.0001) throughout all feeding phases of the trial. Cr propionate supplementation also increased (P < 0.0001) carcass yield, dressing percentage, breast meat yield, leg and thigh weights compared with the control treatment. In conclusion, growth performance, feed conversion, carcass yield, breast and leg meats of broiler birds can be significantly improved by dietary inclusion of Cr propionate. Cr propionate can be supplemented to broiler birds from 1 d old of age at a level that provides 200 or 400 μg/kg organic Cr and can increase the efficiency of broiler production.     

生长肥育猪性别对甲基吡啶铬使用效果的影响

选择 48头平均体重为 30.7kg± 3.1kg的三元杂交健康生长猪，按单因子随机区组设计分为两个处理，分别饲喂未加甲基吡啶铬的日粮和添加 0.05％甲基吡啶铬的日粮。试验结果显示：同对照组青年母猪相比，试验组青年母猪的平均日增重（ ADG）（ P=0.27）、饲料转化效率（ FCR）（ P=0.08）和瘦肉率（ P=0.20）得到不同程度的提高和改善；同对照组阉公猪相比，试验组肥育阉公猪的 ADG和 FCR受到显著（ P=0.04）抑制，瘦肉率表现出降低的趋势（ P=0.27）。结论：性别是影响生长肥育猪对甲基吡啶铬使用效果的一个重要因素。     

淮猪杂交育肥及胴体性能测定

分别选取4窝长白猪×淮猪(长淮组)、大约克猪×淮猪(大淮组)和淮猪(淮猪组)进行育肥和胴体性能测定。试验结果表明,试验猪的日增重差异不显著(P>0.05),但大淮猪平均日增重(626.13±76.82)g(65.24%)、长淮猪平均日增重(587.00±59.58)g(54.91%)均有高于淮猪(378.93±67.74)g的趋势。长淮猪料肉比(3.04)比淮猪(4.54)降低了49.34%,大淮猪料肉比(3.27)比淮猪降低了38.84%。试验猪的平均屠宰率都在70%以上,各组差异不显著(P>0.05)。大淮猪的胴体斜长(74.50±1.91)cm显著长于淮猪(68.50±3.70)cm,(P<0.05)。长淮猪的眼肌面积(36.45±4.80)cm2显著大于淮猪(21.02±4.23)cm2,(P<0.01)。大淮猪后腿比例(31.08±1.97)%有高于淮猪(28.74±1.24)%的趋势。瘦肉率长淮猪(56.69±1.79)%和大淮猪(53.13±1.41)%均极显著(P<0.01)高于淮猪(44.89±2.15)%。淮猪皮(14.10±1.55)%比长淮猪(7.81±0.56)%和大淮猪(8.39±0.81)%高出5个百分点以上,且差异极显著(P<0.01)。3组猪的肉质性状指标都在正常值范围内,肉质优良,未发现有PSE或DFD等劣质肉。     

Effects of dibutyryl cAMP on growth performance and carcass traits in finishing pigs

This study was designed to investigate the effects of dietary supplementation with N⁶, 2′-O-dibutyryl adenosine 3′,5′-cyclic monophosphate (dbcAMP) on growth performance, carcass traits, histochemical characteristics and serum constituents in finishing pigs. Seventy-two Duroc × (Landrace × Large White) barrows (57.3 ± 0.6 kg) were randomly allotted to 3 treatments with 6 replicate pens/treatment (4 pigs/pen). The pigs were fed diets containing 0, 10 and 20 mg dbcAMP/kg, respectively, until the final slaughter weight of approximately 90 kg. There were no differences in growth performance among dietary treatments. Leaf fat proportion and first rib backfat thickness were reduced (P < 0.05), whereas tenth rib backfat thickness tended to decrease (P = 0.10), in pigs fed 10 mg dbcAMP/kg. Lean percentage was greater (P < 0.05) and longissimus muscle area tended to increase (P = 0.10) in pigs fed 10 mg dbcAMP/kg when compared to the control group, but hot carcass weight was not affected by dbcAMP. Growth rate of fat-free lean tissues tended to increase (P = 0.09) in dbcAMP-supplemented pigs. Dietary dbcAMP decreased (P < 0.05) adipocytes diameter in subcutaneous fat, whereas longissimus muscle fiber diameter tended to increase (P = 0.06) with dbcAMP supplementation; however, no difference in longissimus muscle cell density was detected among treatments. Serum concentrations of total protein and 3′,5′-cyclic adenosine monophosphate increased (P < 0.05) in response to dbcAMP, but concentrations of triglycerides, total cholesterol, glucose and urea in serum did not differ among dietary treatments. These results indicate that dbcAMP had a positive effect on carcass traits. Addition of 10 mg dbcAMP/kg to the diet was beneficial for growth performance and lean percentage, as well as improving protein and fat metabolism.     

Breed effects on crossbred cow-calf performance

Effects of seven breeds of cow's sire and 12 breeds of cow's maternal grandsire on preweaning performance of crossbred cows and their calves were examined in data from two experiments conducted at the Roman L. Hruska U.S. Mean Animal Research Center. Data included 1,836 records over three to five parities for 516 cows by 143 sires and by 307 maternal grandsires. The statistical model fitted effects of calf sex, parity, cow birth-breeding year or cow-calf birth year, the breed effects and their interactions. Deviations of breed of sire or equivalent grandsire effects on each trait from the mean for Hereford x Angus cows ranged from -1.6 to 5.5 kg (P less than .001) for calf birth weights, -15 to 1% (P less than .001) for calving difficulty, nonsignificant for preweaning calf mortality and -2 to 27 kg (P less than .001) for calf weaning weight. Deviations were nonsignificant for conception rate and calves weaned per cow exposed to breeding, but -2 to 40 kg (P less than .001) for calf weight weaned per cow exposed for breeding, -7 to 78 kg (P less than .001) for cow weight and -20 to 2% (P less than .001) for body condition score. The advantages of Holstein and Brahman cross over Hereford x Angus cows of 23 and 13% in weight of calf weaned/cow-breeding exposure must be compared with the expected greater feed requirements from 7 or 8% heavier cows and at least 50% higher milk production, which emphasizes the need to include input measures and costs in breed evaluation schemes.     

Effects of energy intake, implantation, and subcutaneous fat end point on feedlot steer performance and carcass composition

The purpose of this experiment was to evaluate the effects of energy intake, implantation, and fat end point on feedlot performance and carcass composition of steers. Three hundred eighty-four yearling crossbred steers (368 +/- 23.1 kg) were allotted in a completely randomized design. Treatments were arranged in a 2 x 3 x 2 factorial experiment. Main effect factors were two levels of intake, three implant strategies, and two compositional fat end points at slaughter. The levels of intake were ad libitum (AL) and restricted (RS) intake (90% ad libitum). The three implant strategies were Revalor-S (REV) (120 mg trenbolone acetate, 24 mg estradiol), Synovex-Plus (SYN) (200 mg trenbolone acetate, 28 mg estradiol benzoate), and no implant (control). The compositional target end points were 1.0 and 1.4 cm s.c. fat cover over the 12th and 13th rib. Restricted-intake steers consumed 9.2% less (P < .01) DM than AL steers. Ad libitum-intake steers gained weight 15.5% more rapidly (P < .01) than RS-intake steers. Steers implanted with REV tended (P < .07) to gain faster than SYN steers, who in turn gained 15.2% more (P < .01) than control steers. Ad libitum-intake steers were 4.8% more (P < .01) efficient than RS steers. Steers fed to a targeted 1.4 cm s.c. backfat cover were 2.9% less (P < .05) efficient than steers fed to 1.0 cm, and steers implanted with either REV or SYN had similar (P = .47) feed efficiencies, whereas control steers had lower (P < .01) feed efficiencies. Steers fed to a targeted compositional fat end point of 1.4 cm had 1.3% higher (P < .01) dressing percentage (DP) than steers fed to 1.0 cm. Control and SYN steers had similar (P = .13) DP; however, REV steers had 6.1% greater (P < .01) DP than SYN steers. Steers fed to 1.4 cm s.c. fat end point had higher (P < .01) numerical yield grades than steers fed to 1.0 cm (3.34 vs 2.71). There was an interaction (P < .01) for intake level and implant for marbling score. Marbling scores were lower (P < .05) for RS x SYN and AL x REV than in other treatments. Steers on the RS x REV treatment were intermediate in marbling to all treatments except AL control, which was higher (P < .01) than RS x SYN, AL x REV, and RS x REV. No interaction for dry matter intake level and anabolic implants was observed for growth performance. The depression in carcass quality resulting from implanting is reduced as backfat increases from 1.0 to 1.4 cm at slaughter.     

Effect of weaning status and implant regimen on growth, performance, and carcass characteristics of steers

One hundred forty-three Angus x Simmental crossbred steers (initial BW = 155.1 +/- 4.5 kg) were used in a 2-yr study (yr 1, n = 67; yr 2, n = 76) to determine the effects of weaning age, implant regimen, and the weaning age x implant regimen interaction on steer growth and performance, organ mass, carcass characteristics, and cooked beef palatability. Steers were early-weaned at an average age of 108 d (EW) or normally weaned at an average age of 202 d (NW) and allotted by weight to an aggressive or nonaggressive implant regimen. On their respective weaning dates, EW and NW steers were penned individually and fed a grain-based diet until they were slaughtered at a final BW of 546 kg. A subsample of steers (n = 2 per treatment) were slaughtered at 254 kg. At 254 kg, EW steers implanted with the aggressive implant regimen had 64% greater backfat depth than those implanted with the nonaggressive implant regimen; conversely, NW steers implanted with the aggressive implant regimen had 52% lower backfat depth than those implanted with the nonaggressive implant regimen (weaning status x implant regimen interaction; P < 0.01). A similar interaction was observed for empty visceral organ weights. Early-weaned steers were younger (354.7 vs 372.4 d; P < 0.01) at final slaughter but were in the feedlot longer (246.5 vs 169.6 d; P < 0.01) than NW steers, whereas the aggressive implant regimen decreased days fed (203.3 vs 212.7; P < 0.07) compared to the nonaggressive implant regimen. Overall ADG was greater for EW than for NW steers (1.61 vs 1.50 kg/d; P < 0.01) and for the aggressive compared with the nonaggressive implant regimen (1.59 vs 1.52 kg/d; P < 0.02). Early-weaned steers consumed less DM per day (7.4 vs 8.5 kg/d; P < 0.01) and were more efficient (0.217 vs 0.208 kg/kg; P < 0.02) but consumed more total DM (1,817 vs 1,429 kg; P < 0.01) than NW steers while in the feedlot. Implant regimen did not affect DMI (P > 0.37) or feed efficiency (P > 0.15). Weaning status did not affect carcass characteristics (P > 0.14), final empty body composition (P > 0.25), or final longissimus muscle composition (P > 0.18); however, steaks from EW steers had higher (P < 0.05) taste panel tenderness and juiciness ratings than steaks from NW steers. The aggressive implant regimen decreased yield grade (P < 0.02), but did not affect quality grade (P > 0.86) compared to the nonaggressive implant regimen. Placing early-weaned steers on an aggressive implant regimen is a viable management option.     

Maternal breed of sire effects on postweaning performance of heifer and steer progeny: postweaning growth and carcass characteristics.

Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)     

日粮精粗比对山羊生长性能和屠宰性能的影响

本试验旨在研究日粮精粗比对山羊生长发育和屠宰性能的影响。18只青年关中奶山羊随机等分为3组;分别饲喂精粗比为31∶69(低)、54∶46(中)和65∶35(高)的3种日粮,各日粮粗蛋白含量相同。结果表明,日增重随精粗比的增加而提高(P<0.05﹚,高精粗比日粮显著提高饲料利用效率(P<0.05﹚,精粗比不影响胃黏膜总重﹑瘤胃和小肠黏膜重量以及胴体重和屠宰率(P>0.05﹚,中等精粗比日粮显著提高皱胃重量(P<0.05﹚。     

谷胱甘肽对肉羊生长性能、屠宰性能及肉品质的影响

选择东北细毛羊×德国肉用美利奴的杂交一代肉羊12只,分成对照组、试验Ⅰ组和Ⅱ组,每组4只,研究谷胱甘肽对肉羊生长性能、屠宰性能及肉品质的影响。试验期60 d。结果表明:与对照组相比,谷胱甘肽显著提高了肉羊的日增重(P<0.05),试验Ⅰ组、Ⅱ组分别提高了14.6%和11.4%;降低了肉羊的料重比(P<0.05),试验Ⅰ组、Ⅱ组分别降低了11.0%和8.1%。试验Ⅰ组的净肉率和GR值显著高于对照组(P<0.05),Ⅱ组的宰前活重显著高于对照组(P<0.05);试验Ⅰ组肉的剪切力显著低于对照组(P<0.05);试验Ⅰ组、Ⅱ组的滴水损失显著低于对照组(P<0.05),而熟肉率显著高于对照组(P<0.05),且两试验组间差异不显著(P>0.05);各试验组宰后45 min内肉的pH没有显著差异(P>0.05),但试验Ⅰ组24 h的pH极显著地高于其他2组(P<0.01)。     

Milk yield of primiparous beef cows from three calving systems and varied weaning ages

Primiparous beef cows produced in 3 calving systems were used in a 2-yr study with a completely random design to measure milk yield throughout a 190-d lactation (2002, n = 20; 2003, n = 24 per calving system). Calving occurred in late winter (average calving date = February 4 +/- 2 d), early spring (average calving date = March 30 +/- 2 d), and late spring (average calving date = May 26 +/- 1 d). Additionally, cows used in this study had been weaned at varied ages as calves, creating 6 dam treatments. Dam age at weaning was 140 (late spring), 190 (late winter, early spring, late spring), or 240 (late winter, early spring) d of age. Milk production was measured by using the weigh-suckle-weigh technique at an average of 20, 38, 55, 88, 125, 163, and 190 d in milk. Milk yield for the 190-d lactation period was calculated as area under the curve by trapezoidal summation. Data were analyzed with a model containing treatment, year, and their interaction. Orthogonal contrasts were used to separate effects when treatment was significant (P < 0.10). Total milk yield did not differ (P = 0.42) between cows in the late winter and early spring systems, but cows in the late spring system tended to differ (P = 0.09) from the average of the other 2 systems. Cows in the late spring calving system had increased milk yield in 2002 and lesser milk yield in 2003 compared with the other calving systems (treatment x year interaction, P < 0.001). Cows born in late spring that had been weaned at 140 d of age produced more (P = 0.05) total milk than those weaned at 190 d of age. Peak milk yield was affected (P < 0.001) by treatment and showed a treatment x year interaction (P = 0.006). Day of peak lactation differed among treatments (P = 0.002), with cows in the late winter system peaking later (P = 0.007) than early spring cows, and late spring cows peaking earlier (P = 0.004) than the average of late winter and early spring cows. The average date of peak lactation was May 4 for the late winter system, May 31 for the early spring system, and July 19 for the late spring system. Calf ADG differed (P < 0.001) for the late spring system compared with the average of the late winter and early spring systems, but the relationship interacted with year (P < 0.001). Cow BW and BW change differed among treatments (P < 0.004), with much of the difference associated with the amount of milk produced or the timing of peak lactation. Season of calving affects milk yield of primiparous cows grazing Northern Great Plains rangelands and ADG of their calves.     

Relationships among serum characteristics and performance and carcass traits in growing pigs

Twelve blood serum components were determined on 78 barrows and 66 gilts, serially slaughtered at six age groups, starting at 69 d, at 2-wk intervals. One-half of the animals were fed ad libitum and one-half were fed "time restricted". Partial correlations between production and carcass traits and serum components were calculated from the residuals of the least-squares analysis. Calcium, serum protein and albumin were highly (P less than .01) correlated with several production and carcass traits. Creatinine was positively correlated (P less than .05) with backfat, loin fat, and percent dissected muscle and bone. Alkaline phosphatase showed a positive relationship with average daily gain (P less than .05) and percent dissected bone (P less than .01). A stepwise regression analysis was used to examine simultaneously the relative predictive value of the blood serum components. The nitrogenous compounds, which included albumin, total protein, urea and creatinine, were the most important predictors of performance (avg daily gain, feed conversion) and carcass composition. However, most of the serum components were not related to the performance and carcass composition traits.     

Effects of different grazing and feeding periods on performance and carcass traits of beef steers

Over three consecutive years, 180 (60/yr) fall-born steer calves were weaned in May (average initial BW = 238 kg, SD = 36.2 kg) and allocated to one of three groups: 1) calf-fed steers that entered the feedlot at weaning; 2) short yearlings that grazed irrigated pasture for another 4 mo and entered the feedlot in September; and 3) long yearlings that grazed with short yearlings during the summer, remained on annual California foothills range through the fall, winter, and spring, and entered the feedlot the following May. All steers were fed until the average group backfat (BF), determined by ultrasound, reached 11 to 12 mm. On pasture, short- and long-yearling steers gained weight in the summer; long yearlings then slightly lost weight in the fall and winter, and then gained weight again the following spring. Average days in the feedlot were 188, 158, and 94 (P < 0.10) for calves, short yearlings, and long yearlings, respectively. Feedlot DMI increased with age (and weight) at feedlot entry, with no difference among groups in gain:feed ratio. The gain of BF was nil on pasture, even when animals were gaining weight, and then increased rapidly when animals were placed on a high-energy diet. Final body weights were heaviest (P < 0.10) in long yearlings, followed by short yearlings and then calves, indicating that a prolonged growing period increases the apparent mature size of the animal. Moreover, total carcass fat contents and percentage of Choice or above were all lower (P < 0.10) in cattle that were older at feedlot entry (i.e., long yearlings) compared with the other groups. In conclusion, increasing the backgrounding period decreased time and total concentrate requirements in the feedlot of Angus-Hereford steers. Older cattle reached 10 mm of BF at heavier weights. Grazing animals gained weight without increasing BF; however, BF increased rapidly in the feedlot. Prolonged grazing may decrease quality grade, either by impairing the ability of the animal to deposit intramuscular fat or by decreasing the time during which dietary energy supply is adequate for intramuscular fat deposition to occur.     

Grass steer production system to improve carcass and meat quality

Three different production systems for autumn born dairy steers, managed more or less intensively, have been investigated. The aim of the production systems were to use a basic diet of grass, either grazed or conserved as silage or hay, combined in various proportions. The animals were slaughtered, aiming for the same degree of fattening, but at three ages. The intensive management aimed at slaughter in January–February at 26–28 months of age after indoor finishing with silage or hay. An “intensive out-of-season” management wished improve at slaughter at 28–30 months of age. Finally an extensive management with finishing at grazing resulted in slaughter in May–June at 30–33 months of age.

In three successive factorial experiments, 106 steers of two genotypes, Holstein and Montbéliard were reared to test the effects of the three production systems. The animals were evaluated for productive traits, carcass quality and biochemical characteristics of m. longissimus thoracis and m. rhomboideus thoracis.

For both breeds, the “extensive” animals produced heavier carcasses (+ 20 kg between “intensive” and “extensive”; P < 0.002). The carcass conformation evaluated by the EUROP classification did not differ between the production systems. The estimated percentage of adipose tissue of the carcass was significantly lower for the “extensive” steers (P < 0.05). The shear force measured on raw meat was not significantly affected by the production system, but after cooking, the shear force was higher for the extensive management as was the total collagen content. The haeminic iron content was always lowest in the intensive management. The results of these three series of experiments show that it is possible to produce steers with a feeding regime consisting mainly of grass (from 87% to 94% of the dry matter intake) grazed or harvested as hay or silage. To make the best use of the herbage resources of the farm and to limit the purchase of concentrates, the production of autumn born steers slaughtered at 32 months seems to be an attractive production system for dairy farmers.