A third-generation esterase inoculant alters fermentation pattern and improves aerobic stability of barley silage and the efficiency of body weight gain of growing feedlot cattle

This study investigated the effects of a mixed bacterial inoculant possessing ferulic acid esterase (FAE) activity on silage fermentation characteristics, aerobic stability, and growth performance of growing feedlot steers. Whole-crop barley (Hordeum vulgare L.) forage (35% DM) was chopped and ensiled without a silage inoculant (UN) or with a mixed bacterial culture containing 1.0 × 10(11) cfu/g of Lactobacillus buchneri LN4017 that produces FAE, 2.0 × 10(10) cfu/g of Lactobacillus plantarum LP7109, and 1.0 × 10(10) cfu/g of Lactobacillus casei LC3200 at a combined rate of 1.3 × 10(5) cfu/g of fresh forage (IN) in mini and Ag-Bag (Ag-Bag Int. Ltd., Warrenton, OR) silos. Silages from the mini silos were assessed for the effect of inoculation on fermentation characteristics and aerobic stability, whereas silages from Ag-Bags were used to formulate 2 barley silage-based total mixed rations (UN and IN) that were fed to growing feedlot steers for 112 d. The IN silage exhibited a homolactic fermentation during the first 7 d of ensiling as reflected by an increased (P ≤ 0.02) lactic acid concentration and an accelerated rate (P < 0.01) of pH decline. Thereafter, fermentation of IN silage became more heterolactic, resulting in greater concentrations of acetic acid (P < 0.01) and pH (P < 0.01) but less (P < 0.01) lactic acid than UN silage. Inoculation did not affect DM losses (P = 0.52) from mini silos. The IN silage remained stable during 21 d, but temperature and yeasts counts in the UN silage increased after 5 d of aerobic exposure. Growing steers fed the IN silage diet had superior (P = 0.03) feed conversion efficiency compared with those fed UN silage. Inoculation of whole-crop barley silage with a mixed culture of homolactic lactic acid-producing bacteria and FAE-producing L. buchneri at ensiling changed fermentation from a homolactic to a heterolactic form during ensiling and improved aerobic stability of the silage and efficiency of BW gain of growing feedlot steers.     

Effects of establishment method and fall stocking rate of wheat pasture on forage mass, forage chemical composition, and performance of growing steers

Stocking rate is a fundamental variable for managing pastures, and there is a distinct relationship between stocking rate and animal performance for each forage type. This research was conducted to determine the effects of fall stocking rate (SR) and method of establishment of wheat pasture planted into dedicated crop fields on animal performance during the fall and subsequent spring. There was a factorial arrangement of tillage methods used in the establishment of wheat pasture and fall stocking rates. Tillage treatments included 1) CT, seed sown into a prepared seedbed, 2) RT, a single pass with a light disk followed by broadcasting of seed, or 3) NT, direct seeding into the undisturbed stubble of the grazed-out wheat pasture from the previous year. The fixed SR during the fall were 1.9, 2.5, and 3.7 growing beef steers (Bos taurus L.)/ha. In the spring all pastures were grazed at the same fixed SR by steers for graze out. Data were analyzed using the mixed procedure of SAS as a randomized complete block design with field as the experimental unit and year as the block. Forage mass, forage nutritive composition, and animal performance during the fall or spring were not affected (P ≥ 0.14) by tillage method. During the fall grazing season, with increasing SR there were linear (P < 0.01) decreases in BW of steers upon removal from pasture, BW gain per steer, and ADG, whereas grazing-day per hectare and BW gain per hectare increased linearly (P < 0.01) with increasing SR. The carryover effects of fall SR into the spring grazing season decreased (P< 0.01) grazing-day per hectare and tended (P ≤ 0.09) to produce quadratic changes in BW upon removal from pasture and BW gain per hectare. Across the fall and spring grazing seasons, grazing-day per hectare increased linearly (P < 0.01) with greater SR, and BW gain per hectare increased quadratically (P = 0.02) with increased fall SR. A tillage treatment by fall SR interaction (P = 0.10) indicates that although there was no difference (P ≥ 0.12) due to tillage treatment in BW gain per hectare at 1.9 or 2.5 SR, NT fields produced (P ≤ 0.04) more BW gain per hectare than CT or RT at the 3.7 SR. Although increasing SR of growing steers leads to reduced animal performance in the fall and reduced carrying capacity in the spring, NT appears to be capable of withstanding greater fall SR with less impact on total production per hectare than CT or RT.     

Technical note: stocking equivalents and stocking rate-gain relationships for steers and cow-calf pairs grazing oversown bermuda grass.

Grazing experiments may use steers or cow-calf pairs for measuring animal performance on pasture treatments, but the validity of extrapolation between these classes of cattle has not been verified. A grazing study was conducted in the spring and summer of both 1988 and 1989 to determine stocking equivalents and stocking rate-weight gain relationships for steers and cow-calf pairs grazing Coastal bermuda grass (Cynodon dactylon [L.] pers.) oversown with rye (Secale cereale L.) and ryegrass (Lolium multiflorum Lam.). Average daily gain and stocking rate (SR; 3.2, 4.2, 6.2, and 7.4 animals per hectare for steers and 1.7, 2.5, 3.7, and 4.9 pairs per hectare for cow-calf pairs) were both adjusted so that comparisons could be made on an equal BW basis. Disk meter height readings were used as measurements of forage accessibility. Disk meter height responses to SR did not differ (P greater than .10) between steer and cow-calf paddocks. There was a linear (P less than .001) decrease in ADG as SR increased, but this decline was steeper (P less than .001) for steers than for cows or suckling calves. Steers tended to be more productive than calves at low SR but less productive at high SR. Disk meter heights for the range of SR used in the study did not differ (P greater than .10) for steers and cow-calf pairs at equivalent BW per hectare. Our study suggests that live BW is a reasonable basis for determining forage requirements of steers and cow-calf pairs under grazing conditions, but extrapolation of production between classes of livestock will not be reliable.     

Effects of a growth hormone-releasing factor analogue and an estradiol-trenbolone acetate implant on somatotropin, insulin-like growth factor I, and metabolite profiles in growing Hereford steers.

Hereford steers (290 +/- 6 kg of BW) were implanted (n = 4) with 140 mg of trenbolone acetate (TBA) and 28 mg of estradiol-17 beta (E2 beta) or nonimplanted (controls, n = 4). In Trial 1, effects of a single i.v. injection of 0, 20, 40, or 80 micrograms of a growth hormone-releasing factor (1-29 NH2) analogue (GRFa) on release of endogenous somatotropin (ST) were evaluated in a double 4 x 4 Latin square design. Plasma samples (n = 21) were obtained from -20 to 240 min after GRFa injection. Area under the ST response curve (AUC) increased (P = .009) in a dose-dependent manner (.2, 2.6, 3.6, 4.3 mg.min-1.mL-1, respectively). Mean ST concentration was not affected (P = .238) by implant but AUC was greater (P = .009) in implanted than in control steers. There was no interaction (P = .460) between dose of GRFa and presence of implant. In Trial 2, 80 micrograms of GRFa was administered at 12-h intervals to the same eight steers. Response of ST (AUC) to the first and last (13th) i.v. injection of GRFa was similar and not affected by implant. Before GRFa administration, plasma insulin-like growth factor I (IGF-I) concentrations were greater (P = .039) in implanted than in control steers (272 vs 164 ng/mL). Administration of GRFa increased plasma IGF-I (P = .0001), decreased plasma urea N (PUN) (P = .0001), and did not alter plasma glucose (P = .447) in both control and implanted steers. Data indicate that effects of GRFa and TBA/E2 beta on plasma IGF-I and PUN concentrations were additive in this study.     

Effect of inoculants on whole-crop barley silage fermentation and dry matter disappearance in situ

Whole-crop barley harvested at the mid-dough stage was ensiled in 3-L laboratory silos either directly (at 30.7% DM) or after wilting (37.8% DM), and with or without application of Inoculant A, B, or D. Each inoculant contained multiple strains of Lactobacillus plantarum and Enterococcus faecium. Two silos per treatment were opened on d 1, 3, 7, 15, and 47 for silage analysis. Wilted silages had higher (P < 0.05) pH than unwilted silages, and Inoculant B (unwilted crop) and Inoculants A, B, and D (wilted crop) decreased (P < 0.05) silage pH compared to the controls. Reducing sugars concentration was 36% lower (P < 0.05), on average, in the wilted than in the unwilted silages. Silages prepared with Inoculants B or D had lower (P < 0.05) concentrations of reducing sugars than the control. Wilting of the barley crop further increased the difference between inoculated and control silages (wilting x inoculation P < 0.05). Neither wilting nor silage inoculants affected concentrations of nonprotein N, ammonia N, or free amino acid N in silage. Wilting did not affect the concentration of lactic acid bacteria (LAB) in the silages. Across DM levels, inoculant-treated silages had larger (P < 0.01) populations of LAB than did the uninoculated controls (7.1 x 10(9) vs 2.3 x 10(9) cfu/g silage DM). Wilting resulted in lesser (P < 0.05) silage lactic acid concentration than the directly ensiled crop. At both DM levels, lactic acid concentration was higher (P < 0.001) in inoculated silages than in controls. The in situ soluble and potentially degradable fractions of silage DM were not affected by wilting or inoculant treatment. The rate of degradation of the potentially degradable silage DM was 35% lower (P < 0.05) in wilted than in unwilted silage. As a result, the calculated effective degradability of silage DM was lower (P < 0.001) in wilted than in unwilted silage. Inoculants did not influence the rate of degradation or effective degradability of silage DM in the rumen. Whole-crop barley ensiled at approximately 30% DM (without wilting) contained higher concentrations of soluble sugars and lactic acid and had higher ruminal degradability of DM than wilted silage (38% DM). Although inoculants did not improve DM degradability of barley silage, lower terminal pH and increased concentrations of lactic acid may improve aerobic stability upon feed-out.     

Intake, digestion, and N metabolism in steers fed endophyte-free, ergot alkaloid-producing endophyte-infected, or nonergot alkaloid-producing endophyte-infected fescue hay

A digestion and N balance trial was conducted to compare effects of traditional endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte infected (NE; MaxQ; Pennington Seed, Inc., Madison, GA) Jesup tall fescue (Festuca arundinacea Schreb.) hay on digestion and N retention in steers. Hay composition (DM basis) was as follows: E+ (10.8% CP, 59.9% NDF, and 29.4% ADF), E- (11.8% CP, 58.5% NDF, and 28.4% ADF), and NE (11.6% CP, 58.6% NDF, and 28.3% ADF). Eight Polled Hereford steers (initial BW 240 +/- 9 kg) were used in a replicated, 3 x 3 Latin square design, with an extra steer allotted to each square. Steers were fed ad libitum for 14 d, followed by a 9-d adaptation to restricted intake (based on the animal with the lowest ad libitum intake for the square) and a 5-d fecal and urine collection. Water intake (20.2 L/d) and urine output (7.40 L/d) did not differ (P > 0.10) during the collection period. Plasma prolactin concentration was less (P < 0.05) for steers on the E+ hay (8.83 ng/mL) than for those on the E- hay (18.03 ng/mL) and intermediate for steers on the NE hay (12.65 ng/mL). Endophyte-infected hay differed (P < 0.05) from E- and NE in ad libitum DMI (5.02 vs. 5.62 and 5.61 kg/d, respectively) and ad libitum DMI as a percentage of BW (1.86 vs. 2.06 and 2.06%, respectively). Restricted DMI during the fecal and urine collection was lower (P < 0.05) for E+ hay than for E- (5.04 vs. 5.24 kg/d), and NE was intermediate (5.19 kg/d). Dry matter digestibility was lower (P < 0.05) for E+ compared with E- and NE (62.3 vs. 67.0 and 65.9%, respectively). Digestibility of ADF was lower (P < 0.05) for E+ than for E-, and was intermediate for NE (61.5, 66.0, and 63.9%, respectively). There were no differences for NDF, cellulose, or hemicellulose digestibilities among hay types. Crude protein digestibility was higher (P < 0.05) for E- and NE than for E+ (54.3 and 52.5 vs. 48.1%, respectively). Nitrogen retention was lower (P < 0.01) for E+ than for E- or NE (15.6 vs. 22.7 or 23.0 g/d, respectively). Hay type did not influence plasma urea N, urine urea N output, or urine urea N as a percentage of urinary N. Results from this study indicate that E+ tall fescue hay was lower in ad libitum DMI, DM digestibility, and N retention than NE or E- hays with similar chemical composition. Hay from NE and E- fescue had nearly identical composition, and did not differ for any variable measured.     

Effects of stocking and nitrogen fertilization rates on steers grazing dallisgrass-dominated pasture

To compare the performance of steer calves managed under different stocking rates (SR; 3.7, 6.2, 8.6, and 11.1 steers/ha for 140 d; chi(I1)) and N fertilization rates (112, 224, and 336 kg of N/ha; chi(I2)) in May 1996, 1997, and 1998, 72 steer calves (BW = 231 +/- 2.5 kg) were assigned randomly to one of 12 0.81-ha dallisgrass (51%)/common bermudagrass (32%) pastures. One-third of the fertilizer was applied in the form of ammonium nitrate in May, June, and August to achieve the prescribed totals. Treatments were separated using a polynomial regression equation: gammai = beta0 + beta1chi(I1) + beta2chi(I2) + beta(11)chi2(I1) + beta(12)chi2(I2) + beta(12)chi(i1)chi(i2) + epsilonI, with years as replicates. Within the range of the data, ADG and BW gain per steer were greatest at a stocking rate of 3.7 steers/ha and 336 kg/ha of N. Body weight gain per hectare peaked at 701 kg when cattle were stocked at 8.9 steers/ha and the pasture was fertilized with 336 kg/ha of N. The least cost of production was at a stocking rate of 3.7 steers/ha, with 112 kg/ha of fertilizer N applied, and the greatest cost of production was at a stocking rate of 11.1 steers/ha with 336 kg/ha of fertilizer N applied. Fertilization at 336 kg/ha of N produced the most profitable stocking rate at 7.3 steers/ha and returned 355.64 dollars. The optimal stocking rate for net return was 79, 81, and 82% of that for maximum BW gain per hectare for 112, 224, and 336 kg/ha of N, respectively. Under the assumptions made in the financial analysis, these data show that the economically optimal carrying capacity of similar pastures can be increased with N fertilizer up to at least 336 kg/ha annually.     

Effects of ruminal and postruminal infusion of starch hydrolysate or glucose on the microbial ecology of the gastrointestinal tract in growing steers

Forty crossbred steers were used to determine the effects of carbohydrate supply site on the indigenous bacteria of the gastrointestinal tract. Steers were fitted with ruminal and abomasal infusion catheters and assigned randomly to one of eight groups in a complete randomized block design. The experimental period was 36 d. Treatments included: 1) a pelleted basal diet fed at 0.163 Mcal ME x (kg BW(0.75)) x 1 x d(-1) (LE); 2) the basal diet fed at 0.215 Mcal ME x (kg BW(0.75)) (-1) x d(-1) (HE); 3) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with ruminal infusion of starch hydrolysate (SH) (RSH); 4) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with abomasal infusion of SH (ASH); and 5) the basal diet fed at 0.163 Mcal ME x (kg BW(0.75))(-1) x d(-1) with abomasal infusion of glucose (AG). The total volume ofinfusate (5 kg x site(-1) x d(-1)) was equalized across treatments and infusion sites by infusion of water. Glucose and SH were infused at rates of 14.35 and 12.64 g x (kg BW(0.75)) x d(-1), respectively. Ruminal, cecal, and fecal samples were obtained on d 36. Ruminal pH was low (5.79) in LE steers and unaffected (P > 0.10) by increased energy intake or carbohydrate infusion. Cecal and fecal pH were 6.93 and 7.00, respectively, for LE steers. Increasing energy intake (P < 0.10) and the rate of carbohydrate infusion (P < 0.01) significantly decreased cecal and fecal pH compared with LE. Ruminal counts of anaerobic bacteria in LE steers were 8.99 log10 cells/g and abomasal carbohydrate infusion had no affect (P > 0.10) on these numbers. However, ASH and AG steers had approximately 1.5 log10 cells/g more (P < 0.01) cecal and fecal anaerobic populations. Ruminal, cecal, and fecal aerobic bacterial counts were 40, 22, and 23%, respectively, lower than anaerobic counts. Generally, aerobic counts responded similarly to the anaerobic counts. Less than 1% of the anaerobic bacteria enumerated in the rumen, cecum, and feces were coliforms, and 97% of the coliforms were Escherichia coli. Carbohydrate infusions resulted in only numerical increases in fecal coliform and E. coli concentrations (P > 0.10). Fecal E. coli were highly acid sensitive in all steers, with less than 1% surviving a 1-h exposure to low pH (2.0). This suggests that cecal or fecal pH is not a good indicator of acid resistance, and it supports the concept that there are other factors that may induce acid resistance.     

枯草芽孢杆菌对肉仔鸡生长性能、肠道形态和菌群数量的影响

本试验旨在研究枯草芽孢杆菌(Bacillus subtilis)对肉仔鸡生长性能、屠宰性能、肠道形态和菌群数量的影响。试验选取健康、体重相近的1日龄爱拔益加(AA)肉仔鸡公雏320只,随机分为4个组,每组8个重复,每个重复10只。对照组饲喂基础饲粮,试验组在基础饲粮中分别添加500 mg/kg枯草芽孢杆菌(Bacillus subtilis,BS组)、20 mg/kg硫酸黏杆菌素(colistin sulfate,CS组)和500 mg/kg枯草芽孢杆菌+10 mg/kg硫酸黏杆菌素(BS+CS组)。试验期6周。结果表明:1)与对照组相比,BS组、CS组能显著提高42日龄肉仔鸡体重(P0.05),提高后期(22~42日龄)平均日增重,显著降低后期和全期(1~42日龄)料重比(P0.05);BS+CS组未对各试验阶段肉仔鸡的生长性能产生显著影响(P0.05)。2)各试验组肉仔鸡的屠宰性能未见显著变化(P0.05)。3)与对照组相比,BS组可显著提高肉仔鸡十二指肠绒毛高度和十二指肠绒毛高度/隐窝深度(P0.05)。4)与对照组相比,BS组、CS组、BS+CS组均能显著提高肉仔鸡42日龄时盲肠乳酸杆菌数量(P0.05),BS组和BS+CS组可显著提高42日龄时盲肠中乳酸菌/大肠杆菌(P0.05)。可见,枯草芽孢杆菌可改善肉仔鸡肠道形态,增加肠道中乳酸杆菌数量,促进肉仔鸡生长。综合考虑以上因素,枯草芽孢杆菌效果优于硫酸黏杆菌素,但联合使用效果不佳。     

Effect of Candida tropicalis,Bacillus subtilis and Lactobacillus Combination on Quality and Aerobic Stability of Sugarcane Tops Silage

The assay was aimed to investigate the effect of different microbial inoculant combinations of Candida tropicalis (CT),Bacillus subtilis (BS),Lactobacillus plantarum (LAP) and Lactobacillus buchneri (LAB) on the quality and aerobic stability of sugarcane tops silage.There were 10 groups:Sugarcane tops silages with no additives served as control group (C);GroupsⅠ1,Ⅰ2 and Ⅰ3 were treated with CT+BS at 10,20 and 30 mL/kg,respectively;Groups Ⅱ1,Ⅱ2 and Ⅱ3 were treated with CT+BS+LAP at 10,20 and 30 mL/kg,respectively;Groups Ⅲ1,Ⅲ2 and Ⅲ3 were treated with CT+BS+LAB at 10,20 and 30 mL/kg,respectively.Each treatment was treated with 0.5% fresh forge urea.The results showed that:①Compared to control group,CT+BS treatment groups had significantly higher levels of pH and acetic acid (P< 0.05),dry matter recovery (DMR) and lactic acid content were significantly decreased (P< 0.05),and the aerobic stability was lower.②Compared to control group,CT+BS+LAP treatment groups had significantly higher levels of pH and lactic acid (P< 0.05),and the aerobic stability was lower.③In CT+BS+LAB treatment groups,the levels of acetic acid were significantly higher and DMR was significantly lower than control group (P< 0.05),and the CP content and aerobic stability were highest in all groups.So the quality of sugarcane tops silage was lower in CT+BS treatment groups and CT+BS+LAB treatment could improve the quality and aerobic stability of sugarcane tops silage.     

热带假丝酵母、枯草芽孢杆菌与乳酸菌组合对甘蔗尾青贮品质和有氧稳定性的影响

试验旨在研究热带假丝酵母(CT)、枯草芽孢杆菌(BS)、植物乳杆菌(LAP)、布氏乳杆菌(LAB)不同微生物添加剂组合对甘蔗尾青贮品质和有氧稳定性影响。本试验设置了10个组。对照组(C)不添加微生物添加剂;Ⅰ1、Ⅰ2、Ⅰ3组分别添加10、20和30 mL/kg的CT+BS菌液;Ⅱ1、Ⅱ2、Ⅱ3组分别添加10、20和30 mL/kg CT+BS+LAP菌液;Ⅲ1、Ⅲ2、Ⅲ3组分别添加10、20和30 mL/kg CT+BS+LAB菌液。添加0.5%尿素作为氮源。结果显示:①与对照组相比,CT+BS处理组pH、乙酸含量显著升高(P< 0.05),乳酸含量、干物质回收率(DMR)显著降低(P< 0.05),有氧稳定性有所降低;②与对照组相比,CT+BS+LAP处理组pH、乳酸含量显著升高(P< 0.05),且可降低青贮有氧稳定性;③与对照组相比,CT+BS+LAB处理组乙酸显著上升,DMR显著降低(P< 0.05),但粗蛋白质(CP)含量、有氧稳定性是所有处理组中最高的。因此,CT+BS处理青贮甘蔗尾品质较差,而CT+BS+LAB能改善甘蔗尾青贮品质,提高有氧稳定性。     

乳酸杆菌抑制致病菌及生物保鲜发酵剂特性评价

以15株乳酸杆菌为研究对象,动物双歧杆菌乳亚种BB-12作为对照,研究它们对肠道致病菌的抑菌特性.结果表明:9株菌对5株指示菌均有较好抑制作用,2株菌对金黄色葡萄球菌、肠炎沙门氏菌、大肠杆菌和蜡样芽孢杆菌均有抑制作用;以抑菌效果、凝乳状态、产酸性能为指标,筛选出4株菌,与嗜热链球菌ST-21组合制备生物保鲜发酵剂;通过...     

Administration of estradiol, trenbolone acetate, and trenbolone acetate/estradiol implants alters adipogenic and myogenic gene expression in bovine skeletal muscle

Twenty crossbred yearling steers (421 kg) were used to evaluate the effects of implanting with trenbolone acetate (TBA; 120 mg), estradiol-17β (E(2); 25.7 mg), and a combination (120 mg of TBA and 24 mg of E(2)) on adipogenic and myogenic mRNA concentrations. Animals were blocked by BW and within each block were assigned to 1 of 4 treatments. Animals were housed and fed in individual pens with 5 animals per treatment. All animals were weighed weekly, and muscle biopsy samples were taken from the LM of each steer on d 0 (before implantation), 7, 14, and 28. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure the quantity of C/EBPβ, PPARγ, stearoyl CoA desaturase (SCD), myogenin, and 3 isoforms of bovine myosin heavy chain (MHC) mRNA. Total BW gain from the 28-d period was adjusted to d 0 by use of covariant analysis, and steers in the implant groups tended (P = 0.09) to have increased BW gain compared with nonimplanted control steers. Analysis of the gene expression of MHC showed that neither implant nor day (P > 0.20) had a significant effect on the expression of type I or IIX MHC mRNA There was also no treatment effect (P > 0.20) on MHC-IIA and myogenin, but increasing days on feed increased (P = 0.05) the expression of MHC-IIA mRNA. Relative mRNA abundance of C/EBPβ, PPARγ, and SCD increased (P < 0.05) during days of feed but PPARγ decreased (P < 0.05) with the treatment of combined TBA/E(2) implant. Results of this study indicate that implanting with TBA, E(2), or both increased BW gain and decreased adipogenic gene expression of finishing steers without significantly affecting the concentration of type I, IIA, or IIX MHC mRNA. Increasing days on feed increased both MHC-IIA and adipogenic gene expression in bovine skeletal muscle biopsy samples. We conclude that administration of steroidal implants had no effect on the proportion of the 3 MHC mRNA isoforms but decreased C/EBPβ, PPARγ, and SCD mRNA in bovine skeletal muscle.     

Influence of thyroid status regulation and Synovex-S implants on growth performance and tissue gain in beef steers.

The separate and combined effects of Synovex-S (SYN) ear implants and thyroxine (T4)-5'-monodeiodinase inhibition (Trial 1) and T3 injection to create a mild elevation in circulating T3 concentrations (Trial 2) on BW gain and composition of gain were studied. Trial 1 used 24, 285-kg Angus steers in two experimental phases. Low-level feeding of propylthiouracil (PTU, 1.5 mg/kg BW daily) was used to achieve inhibition of T4-5'-monodeiodinase activity (TMA). Twelve steers received neither treatment (control) and 12 received SYN+PTU (hypothesized to maximize weight gain) from 0 to 56 d (phase 1) in a single factor treatment comparison. Subsequently, PTU was fed to six control steers and not fed to six of the original SYN+PTU steers from 56 to 175 d (phase 2) in a 2 x 2 arrangement of treatments. Trial 2 used 24, 302-kg Angus-Hereford steers. Treatments were without or with SYN and without or with sc injections of T3 in polyethylene glycol (2 micrograms/kg BW every 48 hr) in a 2 x 2 factorial arrangement of treatments. In both trials, all steers were individually fed a diet of a corn-based concentrate and silage mixture at an equal metabolizable energy intakes per unit of metabolic body weight (.25 Mcal/kg BW.75). Measurements of daily dry matter intakes, weekly BW, 28-d estimates of empty body components (measured by urea dilution), final TMA (trial 1) and plasma thyroid hormone concentrations were obtained. In both trials, SYN increased BW gain and protein accretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of feeding polyclonal antibody preparations on rumen fermentation patterns, performance, and carcass characteristics of feedlot steers

In a previous study, preparations of polyclonal antibodies (PAP) against Fusobacterium necrophorum (PAP-Fn) or Streptococcus bovis (PAP-Sb) were successful in decreasing ruminal counts of target bacteria and increasing ruminal pH in steers fed high-grain diets. The objective of this study was to evaluate the effects of feeding PAP-Fn or PAP-Sb on performance, carcass characteristics, and ruminal fermentation variables of feedlot steers. In Exp. 1, during 2 consecutive years, 226 or 192 Angus and Angus crossbred steers were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. When measured on a BW basis, steers fed only PAP-Sb had a greater G:F (P < 0.05) than those fed no PAP. Nevertheless, when both PAP were fed, feed efficiency was similar (P > 0.10) to steers fed no PAP or only PAP-Sb. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased (P < 0.05) dressing percentage. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased severity of liver abscess (P < 0.05). No differences (P > 0.10) were observed in any other carcass characteristics. In Exp. 2, sixteen ruminally cannulated Angus crossbred steers (BW = 665 +/- 86 kg) were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. Feeding only PAP-Fn or PAP-Sb for 19 d decreased (P < 0.05) ruminal counts of S. bovis when compared with steers fed both or no PAP. The ruminal counts of F. necrophorum in steers fed PAP-Fn alone or in combination with PAP-Sb were decreased by 98% (P < 0.05) after 19 d, when compared with the counts in control steers. Mean daily ruminal pH was greater (P < 0.05) in steers fed both PAP when compared with feeding either or no PAP. Ruminal pH in the first 4 h after feeding was greater (P < 0.05) for steers receiving PAP-Fn alone or in combination with PAP-Sb. Steers receiving either PAP alone or in combination had less (P < 0.05) ruminal NH(3)-N concentrations in the first 4 h after feeding when compared with those of control steers. Polyclonal antibody preparations against S. bovis were effective in enhancing G:F of steers fed high-grain diets, but dressing percentage was decreased. Mechanisms of enhancement of G:F remain unknown but may be related to changes in ruminal counts of target bacteria and associated effects on ruminal fermentation products.     

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.     

Effect of dietary vitamin A restriction on marbling and conjugated linoleic acid content in Holstein steers

To determine the effect of duration of dietary vitamin A restriction on site of fat deposition in growing cattle, 60 Holstein steers (BW = 218.4 +/- 6.55 kg) were fed a diet based on high-moisture corn, with 2,200 IU of supplemental vitamin A/kg of DM (control) or no supplemental vitamin A for a long (243 d; LR) or short (131 d; SR) restriction before slaughter at 243 d. The SR steers were fed the control diet for the first 112 d. Steers were penned individually and fed for ad libitum intake. Jugular vein blood samples for serum retinol analysis were collected on d 1, 112, and 243. Carcass samples were collected for composition analysis. Subcutaneous fat samples were collected for fatty acid composition. Fat samples from the i.m. and s.c. depots were collected to measure adipocyte size and density. Feedlot performance (ADG, DMI, and G:F) was not affected (P > 0.05) by vitamin A restriction. On d 243, the i.m. fat content of the LM was 33% greater (P < 0.05) for LR than for SR and control steers (5.6 vs. 3.9 and 4.2% ether extract, respectively). Depth of back-fat and KPH percentage were not affected (P = 0.44 and 0.80, respectively) by vitamin A restriction. Carcass weight, composition of edible carcass, and yield grade were similar among treatments (P > 0.10). Liver retinol (LR = 6.1, SR = 6.5, and control = 44.7 microg/g; P < 0.01) was reduced in LR and SR vs. control steers. On d 243, LR and SR steers had similar serum retinol concentrations, and these were lower (P < 0.01) than those of control steers (LR = 21.2, SR = 25.2, and control = 36.9 microg/dL). Intramuscular adipose cellularity (adipocytes/mm2 and mean adipocyte diameter) on d 112 and 243 was not affected (P > 0.10) by vitamin A restriction. Restricting vitamin A intake for 243 d increased i.m. fat percentage without affecting s.c. or visceral fat deposition, feedlot performance, or carcass weight. Restricting vitamin A intake for 131 d at the end of the finishing period appears to be insufficient to affect the site of fat deposition in Holstein steers.     

Inoculants for ensiling low-dry matter corn crop: a midlactation cow perspective

In many regions, optimum dry matter (DM) content of corn crop pre-ensilage cannot be ensured for management, agronomical and climatic reasons. Under such conditions, corn crops are harvested at low DM, and are easily exposed to unfavourable fermentation pathways and plant spoilage and wastage. Thus, it is a major question for dairy agriculturists whether certain microbial inoculants application to low-DM corn crop pre-ensilage affects silage quality and cow performance. The objective was to determine effects of adding microbial inoculants to low-DM corn crop at ensiling on silage quality, rumen fermentation and milk production of eight Holstein cows fed the treated silages. Whole corn plant was harvested at milk stage of maturity with 204 g DM/kg of fresh crop, cut to a theoretical particle length of 2 cm, filled in 60 t bunker silos, and treated layer by layer with either no inoculant (control), inoculant 'E' (100 000 cfu/g of fresh crop) containing mainly Lactobacillus plantarum, inoculant 'B' (100 000 cfu) containing mainly Pediococcus pentosanus, Lactobacillus plantarum and Propionibacter freudenreichii or a mixture of inoculants 'E' and 'B' (200,000 cfu). Inoculants were mixed with water and sprayed on thin layers of corn chops layer by layer followed by rolling to ensure proper oxygen outage and even microbial distribution throughout the plants. Eight multiparous lactating Holstein cows at 100 ± 20.5 days in milk were used in a replicated 4 × 4 Latin square design with four 20-day periods including 14 days of adaptation and 6 days of sampling. Dietary treatments were mixed rations containing corn silages with or without the inoculants. The basal diet contained 32.9% corn silage, 14.3% alfalfa hay and 52.8% concentrate on a DM basis. Inoculants did not affect silage pH or content of DM, CP, lactate, acetate, ash and total volatile fatty acids (VFA). Applying 'B' to corn crop resulted in higher water soluble carbohydrates (47.7 g/kg vs 29.8 g/kg) and lower neutral detergent fibre (494.1 g/kg vs 464.0 g/kg) compared with control. The combined inoculants increased silage butyrate relative to other treatments. The mixture of 'E + B' and 'B' moderately decreased rumen pH, when compared to 'E'. The 'E + B' increased rumen VFA concentrations relative to 'E' and control silage. Dry matter intake increased when corn crop was ensiled with 'E' than with control and 'E + B', but this had little impact on milk production or its energy concentrations. Milk energy yield tended to decrease when 'B' but not 'E' was applied alone, compared with control and 'E + B'. The estimated proportion of the consumed energy secreted in milk increased when inoculants were applied together compared with when they were used separately. Results suggest positive effects of Lactobacillus plantarum containing inoculant on feed intake, some effects on corn silage water soluble carbohydrates, fibre and butyrate contents, rumen pH and VFA concentrations; but no significant effects on total tract nutrient digestibility or productivity of Holstein cows fed diets with 329 g corn silage/kg of diet DM.