The relationship between composition of gain and circulating hormones in growing beef bulls fed three dietary crude protein levels

Twenty-one Simmental crossbred bulls (311 +/- 11 kg, 9 mo of age) were used to determine the effect of feeding 10, 12 or 14% CP on concentration of hormones in blood and the relationship of these hormones to composition of gain. Six bulls were slaughtered on d 0 to provide an estimate of initial carcass composition (9-11 rib section). Remaining bulls were assigned to dietary treatments. Blood samples were collected every 30 min from 0800 to 2000 on d 0, 66, 136 and 202 of treatment; bulls were slaughtered on d 203. Across all treatments, growth hormone (GH) declined (P less than .05) from d 0 to d 202. Free insulin-like growth factor I (IGF-I) was lowest (P less than .05) on d 0. In four randomly selected bulls, IGF-I fluctuated during the 12-h sampling periods. Within each treatment group, insulin was greatest on d 202 (P less than .05). Testosterone (T) increased from d 0 to d 66, then declined. Cortisol (C) was lowest on d 66. Thyroid hormones increased (P less than .05) after d 0. Growth hormone and IGF-I were correlated negatively with carcass fat percentage, fat accretion rate and fat thickness. IGF-I concentrations were correlated positively with percentage of carcass protein. Testosterone:cortisol ratio was not related to composition, but high T coupled with low C may be related to carcass leanness (mean carcass fat = 24.4%). These data suggest that GH and IGF-I are the hormones most related to composition of gain in growing beef bulls.     

不同粗蛋白水平对乳鸽生长后期增重的影响

将300只14日龄乳鸽随机分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ五个组进行试验,分别饲喂代谢能恒定为12.94MJ/kg,粗蛋白为16%、18%、20%、22%、24%五个水平的日粮。结果表明:日粮中不同的粗蛋白水平对乳鸽增重和饲料转化率均有显著的影响。随着日粮蛋白质水平的提高,乳鸽增重呈上升的趋势。Ⅰ组乳鸽的日增重显著低于其它组(P<0.05或P<0.01),Ⅱ组低于Ⅲ组、Ⅳ组,差异显著(P<0.05),但Ⅱ组与Ⅴ组、Ⅲ组与Ⅳ组之间,差异不显著(P>0.05);Ⅰ组的饲料转化率低于其它组,差异显著(P<0.05),其它组之间差异不显著。     

Influence of chlortetracycline and dietary protein level on visceral organ mass of growing beef steers

Thirty-two beef steers (285 +/- 3 kg BW) were used to determine the effects of chlortetracycline and dietary protein level on visceral tissue mass, chemical composition, intestinal morphology, and proliferation rate indices. Steers were allotted randomly by weight to a factorial arrangement of dietary treatments consisting of either 10 or 13% CP diets top-dressed with a corn meal carrier (500 g/d) containing either 0 or 350 mg of chlortetracycline. After 84 d, steers were slaughtered and visceral organs removed and separated. Rinsed wet tissue mass was recorded; total RNA, total DNA, tissue DM, and tissue N content were determined; and tissue sections were prepared for immunohistochemical analysis. Thin tissue sections were evaluated to determine crypt depth and villus height as well as proliferation rate by immunohistochemical detection of the nuclear antigen Ki67. Rumen and abomasum weights and small intestinal length were greater (P < 0.04) in steers fed the 13% CP diet than in those fed the 10% CP diet on both an absolute weight basis and a percentage of empty BW. Chemical composition of the small intestinal and ruminal segments were largely unaffected by increased dietary protein. Increasing the dietary CP also increased the villus height in duodenal (P = 0.02) and the crypt depth of jejunal (P = 0.03) sections. Dietary administration of chlortetracycline decreased (P < 0.01) small intestinal weight both on absolute and empty BW bases. Nitrogen and RNA concentrations of the small intestinal segments were unaffected (P > 0.1) by dietary administration of subtherapeutic levels of chlortetracycline; however, because of increases (P < 0.05), or tendencies for an increase (P < 0.1), in the tissue content of DNA, the ratio of N to DNA was decreased (P < 0.05) or tended to be decreased (P < 0.1) in the small intestinal segments of the chlortetracycline-treated animals. The observed decrease in small intestinal epithelial mass does not appear to be due to alterations in cell proliferation rate but rather cell size. Consistent with this finding, cell proliferation, as determined by Ki67 antigen staining, was not affected by dietary treatment. Chlortetracycline administration decreased small intestinal mass that may be a result of decreased cell size.     

Influence of pressed beet pulp and concentrated separator by-product on intake, gain, efficiency of gain, and carcass composition of growing and finishing beef steers

The objectives of this experiment were to determine a NE value for pressed beet pulp and the value of concentrated separator by-product (de-sugared molasses) as a ruminal N source in growing and finishing diets for beef cattle. One hundred forty-four cross-bred beef steers (282 +/- 23 kg of initial BW) were used in 2 experiments (growing and finishing). A randomized complete block design was used, with a 3 x 2 factorial arrangement of treatments (level of pressed beet pulp and inclusion of concentrated separator by-product) for both studies. Steers were blocked by BW and allotted randomly to 1 of 6 treatments. In the growing study, the control diet contained 49.5% corn, 31.5% corn silage, 10.0% alfalfa hay, and 9.0% supplement (DM basis). Pressed beet pulp replaced corn at 0, 20, or 40% of dietary DM, and concentrated separator by-product replaced corn and urea at 10% of dietary DM. The growing study lasted for 84 d. Initial BW was an average of 2-d BW after a 3-d, restricted (1.75% of BW) feeding of 50% alfalfa hay and 50% corn silage (DM basis), and final BW was an average of 2-d BW after a 3-d, restricted (1.75% of BW) feeding of 31.5% corn silage, 10.0% alfalfa hay, 25.0% dry-rolled corn, 20.0% pressed beet pulp, 5.0% concentrated separator by-product, and 8.5% supplement (DM basis). After the growing study, the steers were weighed (415 +/- 32 kg), rerandomized, and allotted to 1 of 6 finishing diets. The control diet for the finishing study included 45% dry-rolled corn, 40% high-moisture corn, 5% brome hay, 5% pressed beet pulp, and 5% supplement. Pressed beet pulp replaced high-moisture corn at 5.0, 12.5, and 20.0% of the dietary DM, and concentrated separator by-product replaced high-moisture corn and supplement at 10.0% of diet DM. Steers were slaughtered on d 83 or 98 of the study. In the growing study, the addition of pressed beet pulp to growing diets linearly decreased (P = 0.001) DMI and ADG and inclusion of 10% concentrated separator by-product decreased (P = 0.001) G:F. Increased levels of pressed beet pulp in the finishing diets caused a linear decrease (P = 0.001) in ADG and tended (P = 0.06 and 0.07 for kg/d and % of BW, respectively) to quadratically decrease DMI, whereas addition of concentrated separator by-product increased (P = 0.02 and 0.001 for kg/d and % of BW, respectively) DMI. Apparent NEg of pressed beet pulp was 94.2% of that of corn in the growing study and 81.5% of that of corn in the finishing study.     

日粮粗蛋白质水平对羊养分瘤胃降解率的影响

为了研究日粮粗蛋白质水平对羊养分瘤胃降解率的影响,为优化羊日粮蛋白质水平提供依据,试验采集小尾寒羊瘤胃液,借助体外模拟培养技术,对4种粗蛋白质水平(12%、14%、16%、18%)日粮的养分瘤胃降解率进行研究。结果表明:日粮粗蛋白质水平对DM降解率没有显著影响,但对CP、NDF和ADF降解率影响显著。结果提示,提高羊日粮的粗蛋白质水平有利于营养物质在瘤胃中降解,日粮粗蛋白质水平为16%时对提高羊的养分瘤胃降解率较为适宜。     

Effects of body weight, frame size and rate of gain on the composition of gain of beef steers

Energy concentration of gain (EG) is an inherent component in beef cattle feeding systems. The National Research Council (NRC) uses equations based on body weight, rate of gain and cattle type to predict EG and, in turn, to calculate dietary energy requirements. From EG, fat and protein deposition can be calculated directly. A dynamic computer growth model also can be used to estimate EG. In both the NRC and the computer model, EG increases from about 3 to 6 Mcal/kg as body weight increases from 200 to 500 kg if daily gain is 1 kg. Both NRC and the model predict EG of calves to be about .3 Mcal/kg greater than a previous NRC system. In contrast to the NRC, model-predicted EG of yearlings is lower at lighter and greater at heavier body weights. Rate of gain affects estimates of EG more for the dynamic model than for the NRC systems. When predicted EG was compared with observed EG for 46 pens of feedlot steers in comparative slaughter trials, NRC estimates exhibited a narrow range compared with observed values with correlation coefficients of r = .38 and r = .71 (previous NRC). Model estimates of EG were closer (r = .85). The NRC predictions of EG systematically erred with initial body composition, diet metabolizable energy and length of feeding period (P less than .01) and with initial body weight and rate of gain (P less than .05). No systematic errors in model-predicted EG were detected. Enhanced model sensitivity to compensatory growth and rate of gain should reduce both EG and body weight gain prediction errors.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of dietary fiber level on nutrient digestibility in growing pigs

The objective of this study was to investigate the effects of total dietary fiber level on nutrient digestibility and the relationship between apparent total tract digestibility of total dietary fiber, and soluble dietary fiber, insoluble dietary fiber and available energy. Sugar beet pulp was as the only fiber source. The experiment was designed as a 6 × 6 Latin square with an adaptation period of 7 d followed by a 5-d total collection of feces and urine. Feed intake tended to decrease (P =0.10) as total dietary fiber level increased. The apparent total tract digestibility of dry matter, crude protein and gross energy decreased (P <0.01) when total dietary fiber increased but the digestibility of soluble dietary fiber and insoluble dietary fiber increased (P <0.01). The digestible energy and metabolizable energy content of diets decreased (P <0.01) as the total dietary fiber increased.     

The use of endogenous nitrogen for microbial crude protein synthesis in the rumen of growing bulls

The objective of this study was to quantify endogenous nitrogen (N) recycled for microbial protein synthesis in the rumen. Four growing bulls (Schwarzbuntes Milchrind; bodyweight: 240–310 kg) with duodenal T‐shaped cannulas were fed diets containing four levels of crude protein content (200, 156, 102 and 63 g/kg dry matter, respectively). The diets were based on wheat, barley, tapioca meal, soybean extracted meal, dried beet pulp, meadow hay and straw. The diets had an energy level of 11.1, 10.9, 10.2 and 9.6 MJ metabolizable energy/kg dry matter. Faeces and urine were collected in four 7‐day balance periods. Duodenal flow rate was estimated by TiO₂, pelleted with grain, as a marker. The relationship between urine N excretion, the amount of microbial N reaching the duodenum, ruminal N balance and N retention were examined and the amount of endogenous N available for microbial protein synthesis without negative effects on the N retention was determined. It can be concluded that up to 16% of the microbial N supply could be covered by recycled endogenous N, but N retention should not be decreased by more than 1.5 residual standard deviations of maximal N retention.     

The effects of dietary fiber level on nutrient digestibility in growing pigs

The objective of this study was to investigate the effects of total dietary fiber level on nutrient digestibility and the relationship between apparent total tract digestibility of total dietary fiber, and soluble dietary fiber, insoluble dietary fiber and available energy. Sugar beet pulp was as the only fiber source. The experiment was designed as a 6 x 6 Latin square with an adaptation period of 7 d followed by a 5-d total collection of feces and urine. Feed intake tended to decrease （P =0.] O） as total dietary fiber level increased. The apparent total tract digestibility of dry matter, crude protein and gross energy decreased （P 〈0.0]） when total dietary fiber increased but the digestibility of soluble dietary fiber and insoluble dietary fiber increased （P 〈0.01）. The digestible energy and metabolizable energy content of diets decreased （P 〈0.01） as the total dietary fiber increased.     

Effects of dietary crude protein and tannic acid on nitrogen excretion,urinary nitrogenous composition and urine nitrous oxide emissions in beef cattle

Two consecutive trials were carried out to study the effects of dietary crude protein (CP) and tannic acid (TA) on nitrogen (N) metabolism of beef cattle and consequently, the N₂O emissions from the urine of cattle. In Trial I, eight growing castrated cattle were used as the experimental animals. Two levels of dietary CP (110.6 and 135.7 g/kg dry matter [DM]) and two levels of TA (0 and 16.9 g/kg DM) were allocated in a replicated 2 × 2 crossover design. In Trial II, the N₂O emissions from the urine of cattle collected from Trial I were determined using the static incubation technique. An interaction between dietary CP and TA on the urinary N excretion (p < .05) was found but not on the N₂O‐N emission of cattle urine. Increasing dietary CP level from 110.6 g/kg DM to 135.7 g/kg DM increased the total N excretion (p < .001), the N retention (p < .05) and the ratio of urinary urea‐N/urinary N (p < .01), did not affect the N use efficiency (NUE; p > .05) and shifted the N excretion from faeces to urine. Increasing the dietary CP level increased the N₂O‐N emission of cattle urine. Dietary addition of TA decreased the urinary excretions of urea (p < .001) and shifted the N excretion from urine to faeces, did not affect the NUE of beef cattle (p > .10), and decreased the N₂O‐N emission of cattle urine. Pyrogallol and resorcinol of the TA metabolites were detected in urine with dietary addition of TA. Feeding beef cattle with relatively low CP level and adding TA in rations are effective approaches to mitigate the N₂O‐N emissions from cattle urine.     

日粮粗蛋白质水平对育肥湖羊瘤胃微生物组成和发酵参数的影响

为研究日粮粗蛋白质水平(crude protein, CP)对育肥湖羊瘤胃微生物、pH及VFA含量的影响,选取54只4月龄[(32.25±2.50) kg]湖羊公羔,采用完全随机分组设计,将试验羊分为3个处理组,每个处理组18个重复,每个重复1只羊,3个处理组日粮CP水平分别为11.5%、14.0%、16.5%,试验期共70 d,包括7 d预试期,63 d正试期。试验期结束后,每组选择10只试验羊进行屠宰,测定屠宰性能并采集瘤胃内容物,用于瘤胃微生物DNA提取。结果表明:1)不同CP处理组对宰前活重、胴体重、屠宰率、瘤胃总重、瘤胃组织重及尾脂重无显著影响(P> 0.05)。2) 11.5%CP组瘤胃液氨态氮显著低于14.0%CP及16.5%CP组(P <0.001),但14.0%CP组与16.5%CP组无显著差异(P>0.05)。瘤胃液p H随日粮蛋白水平的增加有增加的趋势(P <0.1)。3)总挥发性脂肪酸(total volatile fatty acids, TVFA)浓度不受日粮中CP水平的影响(P> 0.05),其中乙酸、丙酸、异丁酸、丁酸、戊酸...     

日龄、性别、蛋白质沉积和日粮赖氨酸效率对快速生长肉鸡的赖氨酸需求的影响

通过氮平衡试验,可以根据粗蛋白质(Crude Protein,CP)沉积量和日粮赖氨酸利用率,评估不同性别和日龄的快速生长型肉鸡(科宝500)的赖氨酸需要量.试验分为3个日龄段(第1日龄段10～25日龄,第2日龄段30～45日龄;第3日龄段50～65日龄),每个日龄段各72羽试验鸡(公母各36羽).试验日粮由高蛋白质(High Protein,HP)-豆粕、小麦蛋白质和结晶氨基酸(L-苏氨酸(Thr)、DL-蛋氨酸(Met)、L-精氨酸(Arg)]组成,共设6个级别的粗蛋白质水平,从而使得赖氨酸(4.30gLys/100gCP)成为日粮的第一限制性氨基酸[Lys:(Met Cys):Thr:Arg=1:1.01:0.91:1.14].由于应用了非线性氮利用率模型,将氮维持需要量(Nitrogen Maintenance Requirement,NMR)和每日氮日沉积的理论最大值(Theoretical Maximum for day Nitrogen Retention,NRmax T)确定为模型参数,以便能进一步评估依赖于日龄、性别和每日粗蛋白质沉积量的赖氨酸需要量.例如,按每日粗蛋白质沉积量理论潜能的60%计算得到的日粮赖氨酸需求水平(10～25日龄:赖氨酸含量1.10%,日采食量60g;30～45日龄:赖氨酸含量1.03%,日采食量140 g;50～65日龄:赖氨酸含量0.96%,日采食量170g)与已报道的结果完全一致.然而,当氨基酸需要量水平确定后,采食量预测值就成为最重要的影响因子之一.而作为影响氨基酸需要量重要因素的每日粗蛋白质沉积量和日粮氨基酸的利用效率,在今后的氨基酸需要量研究中还需作进一步的研究.     

The influence of slaughter weight and level of feeding on growth rate,feed conversion and carcass composition of bulls

168 Red Danish bulls were used in a 7 × 4 factorial experiment with seven slaughter weights (180, 240, 300, 360, 420, 480, 540 kg live weight) and four feeding levels (100%, 85%, 70%, and 55% of the feeding level practiced at the Egtved progeny test station).The maximum daily gain of live weight, carcass weight, lean and fat occurred at 270, 300, 275 and 480 kg live weight respectively. Maximum daily gain of bone occurred before 200 kg live weight. By reducing the level of feeding, the daily gain of fat was reduced more than that of lean and bone. This was especially so at the heavier slaughter weights.Feed conversion efficiency was better at the 85% feeding level than at the 100% level. This is contrary to what would be expected from the recommended energy feeding standards of many countries. The increase in energy requirement with increasing liveweight was higher than most recommended energy standards.At the lower slaughter weight, carcass composition was little influenced by feeding level. At the heavier weights the relative weights of lean and bone increased and fat decreased when the feeding levels were reduced.The relative weight of forerib + shoulder + neck (cut II) and especially the flank + brisket + flat ribs + foreshank (cut I) increased with increasing slaughter weight and the relative weight of the pistol (cut III) decreased. The relative weight of cut I, which was the fattest, increased with increasing feeding level. The relative weight of the pistol cut was independent of feeding level.40 muscles or muscle groups were dissected from the left side of 48 carcasses and weighed. The occipital muscles were the latest to develop and those in the legs the earliest. The muscles in the lumbar and abdominal region developed at a moderate rate. The feeding level affected the relative growth of some muscles.     

日粮不同蛋白质水平对育肥羔羊增重效果的影响

本研究选用宣化种羊场2月龄左右、体重相近的健康陶赛特♂×小尾寒羊♀杂交一代羔羊30只,按体重、性别对等的原则,随机分成3组,每组10只,试验3组蛋白质水平分别是18%、17%、16%,研究日粮不同蛋白质水平对育肥羔羊增重效果的影响。试验结果表明:试验1组和试验2组的试验末重、日均增重以及试验期净增重都显著高于试验3组(P0.05);试验1组和试验2组间差异不显著(P0.05)。羔羊宰前活重、胴体重试验1组、试验2组与试验3组差异显著(P0.05),而各组的屠宰率差异不显著(P0.05)。羔羊育肥阶段补饲精饲料选用17%蛋白水平的日粮最好。     

Effects of dietary protein level and clinoptilolite on the weight gain and liver mineral response of growing lambs to copper supplementation

Growing male Synthetic I (1/2 Finnish Landrace x 1/4 Dorset x 1/4 Rambouillet) lambs were used in two experiments (64 lambs in Exp. 1 and 63 in Exp. 2) to test the hypothesis that dietary CP level (9 or 14% of diet as fed) and(or) clinoptilolite (clino; 0 or 2% of diet) affects growth and tissue mineral concentrations of growing lambs fed supplemental Cu. Lambs were individually fed their respective diets ad libitum and killed after 12 wk (Exp. 1) or 16 wk (Exp. 2) to obtain carcass measurements, organ weights and liver mineral concentrations. In Exp. 1, 20 ppm added Cu (as CuSO4.5H2O) increased mortality and depressed BW gain (P less than .01) and daily feed intake (P less than .05) in the presence or absence of clino and at both levels of CP. Liver Cu concentration was greater (P less than .01) in lambs fed added Cu than in those not fed Cu (408 ppm vs 110 ppm, respectively). Neither CP nor clino affected liver Cu concentration. Clinoptilolite increased daily gain of lambs fed high CP but not low CP (P less than .01). In Exp. 2, clino in the diet had no effect on daily gain or daily feed, but 20 ppm Cu addition depressed daily gain (P less than .01) and gain/feed (P less than .07). Organ weights and levels of trace elements other than Cu in the liver generally were not affected by diet in either experiment. It is concluded that high dietary CP or 2% dietary clino did not protect against toxic signs of Cu when Cu was added to the basal diet (10 ppm Cu) at 10 or 20 ppm.     

Effects of crude protein and undegradable intake protein on growth performance,nutrient utilization,and rumen fermentation in growing Thai-indigenous beef cattle

Tropical Animal Health and Production - The objective of this study was to investigate growth performance, nutrients apparent digestibility, nitrogen utilization, rumen fermentation, and rumen...