M. L. Bauer

Comparative effect of direct-fed microbials on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle.

The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.

Effects of distillers dried grains with solubles on growing and finishing steer intake, performance, carcass characteristics, and steak color and sensory attributes

Seventy-two crossbred and purebred beef steers (296 +/- 9 kg initial BW) were used in a completely randomized design to determine effects of 30% distillers dried grains with solubles (DDGS; 29.2% CP, 9.7% fat, DM basis) inclusion during the growing or finishing period on DMI, performance, carcass, and meat quality traits. The resulting treatments were 0:0, 30:0, 0:30, and 30:30 (diet DDGS percentage fed during growing and finishing periods, respectively). Steers were individually fed a growing diet (65% concentrate) for 57 d, then acclimated to and fed a finishing diet (90% concentrate) for 80 or 145 d. Dietary ingredients included dry-rolled corn, corn silage, grass hay, concentrated separator by-product, and supplement. Diets included 27.5 mg/kg of monensin and 11 mg/kg of tylosin and were formulated to contain a minimum of 12.5% CP, 0.70% Ca, and 0.30% P. During the growing period, DMI was not different (P >or= 0.63; 10.22 +/- 0.23 kg/d; 2.42 +/- 0.06% of BW). Steer performance, including ADG (1.75 +/- 0.05 kg/d) and G:F (174.1 +/- 6.8 g/kg), was not affected (P >or= 0.14) by treatment during the growing period, and final BW at the end of the growing period was not different (425 +/- 7 kg; P = 0.99). During the finishing period, DMI was not different (P >or= 0.54; 8.47 +/- 0.66 kg/d; 1.57 +/- 0.09% BW). During the finishing period, no differences (P >or= 0.22) were observed for ADG (1.54 +/- 0.07 kg/d) or G:F (202.4 +/- 28.3 g/kg). As a result, final BW was not different (P >or= 0.28; 551 +/- 15 kg). Longissimus muscle area (77.8 +/- 3.3 cm(2)), 12th-rib fat thickness (1.26 +/- 0.10 cm), and KPH (2.48 +/- 0.16%) were not different (P >or= 0.16). There were no differences (P >or= 0.35) in yield grade (3.33 +/- 0.17) or marbling (431 +/- 21; Small(0) = 400). Results from the trained panel indicated no differences (P >or= 0.16) in tenderness, which averaged 6.03 +/- 0.16 (8-point hedonic scale); however, steaks from steers fed 0:30 or 30:30 tended (P = 0.10) to be juicier and more flavorful than steaks from steers fed 0:0 or 30:0 (6.01 vs. 5.83 +/- 0.11; 6.02 vs. 5.89 +/- 0.08, respectively). Inclusion of 30% DDGS in the growing period tended to reduce L (P = 0.08; 48.6 vs. 48.9 +/- 0.2) and b (P = 0.01; 8.24 vs. 8.65 +/- 0.18) of steaks. Feeding DDGS during growing or finishing reduced b (P = 0.02; 8.35 vs. 8.74 +/- 0.18) compared with 0:0. Feeding DDGS during the finishing period reduced a (P < 0.001; 20.1 vs. 22.0 +/- 0.24) of steaks. Furthermore, feeding DDGS during growing or finishing reduced a (P < 0.001; 20.9 vs. 21.7 +/- 0.24) compared with 0:0. Feeding 30% DDGS did not affect any performance or carcass characteristics but did influence steak sensory attributes and color.

Effect of selenium supplementation and plane of nutrition on mares and their foals: foaling data.

To investigate the maternal plane of nutrition and role of Se yeast on foaling variables and passive transfer of IgG, 28 Quarter Horse mares were used in a study with a randomized complete block design. Mares were blocked by expected foaling date and assigned randomly within block to dietary treatments. Dietary treatments were arranged as a 2 x 2 factorial with 2 planes of nutrition, pasture or pasture + grain mix (fed at 0.75% of BW on an as-fed basis) and 2 concentrations of Se yeast (0 or 0.3 mg/kg of DMI). This resulted in 4 treatments: pasture (PA), pasture + Se (PS), pasture + grain mix (PG), and pasture + grain mix + Se (PGS). Assuming DMI at 2% of BW, the mares fed PA and PS received approximately 100% of the calculated NRC (2007) DE requirements, whereas PG and PGS received 120%. Selenium supplementation began 110 d before the estimated foaling date, and all dietary treatments were terminated at parturition. At parturition, foaling variables were recorded. Additionally, placental weight was recorded and 2 samples from each placenta were collected for analysis of DNA, RNA, and protein. Colostrum was obtained for fat, protein, milk urea N, somatic cell count, and IgG analyses. Foal blood samples were collected at 0, 6, 12, 18, and 24 h after parturition for IgG analysis. There was no effect (P >or= 0.21) of Se or plane of nutrition on foaling variables; however, foal BW as a percentage of mare BW tended (P = 0.10) to be reduced in foals from mares on grain mix (PG and PGS; 7.6%) compared with mares not fed grain mix (PA and PS; 8.0%). There was also no effect (P >or= 0.20) of Se or plane of nutrition on placental cell number (mg of DNA/g), potential cellular activity (RNA:DNA), expulsion time, or weight. However, mares fed supplemental Se (PS and PGS) had decreased (P = 0.02) placental cell size (24.1 mg of protein/mg of DNA) compared with mares not fed supplemental Se (PA and PG; 32.5 mg of protein/mg of DNA). There was also no effect (P >or= 0.18) of Se or plane of nutrition on colostral fat, protein, milk urea N, or somatic cell count. However, mares fed grain mix (PG and PGS) had less (P = 0.03) colostral IgG (76.5 g/L) compared with mares not fed grain mix (PA and PS; 126.6 g/L). Foals from mares fed grain (PG and PGS) tended (P = 0.06) to have less overall serum IgG (13.6 g/L) compared with foals from mares not fed grain (PA and PS; 15.3 g/L). These data indicate that the maternal diet during the last one-third of gestation affects placental efficiency and colostral IgG.

Fecal shedding of Escherichia coli O157:H7 in North Dakota feedlot cattle in the fall and spring.

Cattle are an important reservoir of Escherichia coli O157:H7, which can lead to contamination of food and water, and subsequent human disease. E. coli O157:H7 shedding in cattle has been reported as seasonal, with more animals shedding during summer and early fall than during winter. North Dakota has relatively cold weather, especially in winter and early spring, compared with many other regions of the United States. The objective was to assess fecal shedding of E. coli O157:H7 in North Dakota feedlot cattle over the fall, winter, and early spring. One hundred forty-four steers were assigned randomly to 24 pens on arrival at the feedlot. Samples of rectal feces were obtained from each steer four times (October and November 2003, and March and April 2004) during finishing. On arrival (October 2003), 2 (1.4%) of 144 cattle were shedding E. coli O157:H7. The shedding increased significantly to 10 (6.9%) of 144 after 28 days (November 2003), to 76 (53%) of 143 at the third sampling (March 2004), and dropped significantly to 30 (21%) of 143 at the fourth (last) sampling (March 2004) before slaughter. Unfortunately, we were unable to sample the cattle during winter because of the extreme weather conditions. Sampling time significantly (P < 0.0001) influenced variability in E. coli O157:H7 shedding, whereas herd (P = 0.08) did not. The prevalence of E. coli O157:H7 shedding in North Dakota steers in fall and early spring was comparable to what has been reported in other parts of the United States with relatively warmer weather. Further research into E. coli O157:H7 shedding patterns during extreme weather such as North Dakota winters is warranted in order to fully assess the seasonal effect on the risk level of this organism.

A longitudinal study of Salmonella shedding and antimicrobial resistance patterns in North Dakota feedlot cattle.

Salmonella is one of the most frequent causes of foodborne illness worldwide, and transmission involves foods of animal origin such as beef. The objective of this study was to monitor the prevalence of Salmonella fecal shedding in feedlot cattle during the finishing period and to assess the antimicrobial resistance patterns of the isolated salmonellae. On arrival at the feedlot, 1 (0.7%) of the 144 steers was shedding Salmonella in its feces. After 28 days on feed, shedding was detected in 8 (5.6%) of the 144 steers. At the third sampling, 19 (13%) of 143 steers were shedding, and the number of shedders continued to increase to 89 (62%) of 143 at the last sampling. Salmonella shedding was significantly influenced (P < 0.0001) by sampling time but not by herd of origin. All Salmonella isolates identified belonged to serotype Typhimurium serovar Copenhagen, a type commonly isolated from Salmonella infections in humans. Antimicrobial resistance testing of the isolates revealed five multidrug resistance patterns, two of which accounted for 104 (95.4%) of 109 of the isolates. All the isolates were susceptible to ceftiofur, and all were resistant to spectinomycin, sulfathiazole, tiamulin, florfenicol, ampicillin, penicillin, chlortetracycline, oxytetracycline, and clindamycin. Data from this study indicate that a high prevalence of antimicrobial-resistant Salmonella strains can sometimes be found in feedlot cattle in North Dakota. These data will contribute to risk assessment of Salmonella shedding by cattle in feedlots and highlight the need to continue preharvest monitoring for this organism.

Comparison of two sampling methods for Escherichia coli O157:H7 detection in feedlot cattle.

Two sampling methods (rectoanal swabs and rectal fecal grabs) were compared for their recovery of Escherichia coli O157:H7 from feedlot cattle. Samples were collected from 144 steers four times during the finishing period by swabbing the rectoanal mucosa with cotton swabs and immediately obtaining feces from the rectum of each individual steer. The number of steers with detectable E. coli O157:H7 increased from 2 of 144 (1.4%) cattle on arrival at the feedlot to 10 of 144 (6.9%) after 1 month, 76 of 143 (52.8%) after 7 months, and 30 of 143 (20.8%) at the last sampling time before slaughter. Wilcoxon signed-rank tests indicated that the two sampling methods gave different results for sampling times 3 and 4 (P < 0.05) but not for sampling time 2 (P = 0.16). Agreement between the two sampling methods was poor (kappa < 0.2) for three of the four sampling times and moderate (kappa = 0.6) for one sampling time, an indication that in this study rectoanal swabs usually were less sensitive than rectal fecal grabs for detection of E. coli O157:H7 in cattle. Overall, the herd of origin was not significantly associated with E. coli O157:H7 results, but the weight of the steers was. Further investigation is needed to determine the effects of potential confounding factors (e.g., size and type of swab, consistency of feces, site sampled, and swabbing technique) that might influence the sensitivity of swabs in recovering E. coli O157:H7 from the rectoanal mucosa of cattle.

Influence of dry-rolled corn processing and increasing dried corn distillers grains plus solubles inclusion for finishing cattle on growth performance and feeding behavior

Sixty-four yearling steers (345 ± 4.2 kg BW) were used to study the effects of degree of dry-rolled corn processing and corn dried distillers grains plus solubles (DDGS) inclusion on feeding and ruminating behavior, G:F, and carcass characteristics. Steers were assigned randomly to 1 of 4 experimental treatments (n = 16 per treatment): 1) coarse-rolled (2.68 mm) corn and 20% DDGS, 2) coarse-rolled corn and 40% DDGS, 3) fine-rolled (1.46 mm) corn and 20% DDGS, and 4) fine-rolled corn and 40% DDGS. Final BW and ADG were not affected by corn processing or DDGS. Dry matter intake (kg/d and % of BW) decreased (P < 0.001) and G:F increased (P < 0.001) with increasing inclusion of DDGS. Meal number increased (P ≤ 0.05) and meal size decreased (P < 0.001) with finer dry-roll corn processing and with increasing inclusion of DDGS. Drinking time decreased (P = 0.03) with finer dry-rolled corn processing and tended to increase (P = 0.06) with increased inclusion of DDGS. Rumination time while standing decreased (P = 0.03) with increased inclusion of DDGS. Increasing inclusion of DDGS from 20 to 40% decreased intake, increased G:F, and altered feeding behavior of finishing steers consuming a 90% concentrate diet without affecting carcass quality. Increasing the degree of dry-roll corn processing did not impact growth performance and did not interact with increasing inclusion of DDGS in finishing diets.

Effect of feeding rolled flaxseed on milk fatty acid profiles and reproductive performance of dairy cows

The objectives were to study the effects of feeding rolled flaxseed (FLX) to early-lactation dairy cows on milk yield, milk components, and milk fatty acid profiles as well as on measures of cow reproduction. Lactating Holstein cows, on 3 commercial dairies, were fed either an early-lactation ration (CON) or a ration that was similar in protein, energy, and fat content but that included FLX (0.85 kg of DM/cow per day). Within each dairy, cows were allocated alternately to breeding pens upon leaving the fresh pen (approximately 10 ± 5 d postpartum). Pens (n = 4 to 5 pens/dairy) were randomized to treatment (n = 2 to 3 pens/treatment per dairy). Pen (CON, n = 6; FLX, n = 7) was considered the experimental unit and data were analyzed as a split plot with pen as the whole-plot error term. Cows fed FLX had greater (P ≤ 0.06) proportions of cis-9, trans-11 C18:2, C18:3n-3, and C20:0 fatty acids in milk fat and a lesser (P = 0.03) proportion of C20:3n-6 fatty acid when compared with cows fed the CON diet. Treatment did not affect (P ≥ 0.24) milk yield, milk protein, protein yield, milk fat, or milk fat yield. No interactions (P ≥ 0.52) were found between treatment and season of the year or parity, or between treatment and days open, pregnancies per AI at first or second service, or pregnancy loss. In conclusion, feeding FLX at 0.85 kg/cow per day (DM basis) altered the fatty acid profile of milk, but milk yield, milk composition, and reproductive performance of dairy cows were not affected.

Effects of increasing field pea (Pisum sativum) level in high-concentrate diets on growth performance and carcass traits in finishing steers and heifers.

Three experiments were conducted to determine the effect of increasing field pea level in high-concentrate finishing cattle diets on ADG, DMI, G:F, and carcass traits, and to estimate the NE of field pea. In Exp. 1, 118 yearling heifers (417.9 +/- 2.4 kg initial BW) were blocked by initial BW and assigned randomly to 1 of 4 treatments (0, 10, 20, or 30% dry-rolled field pea, DM basis; 4 pens/treatment). In Exp. 2, 143 beef steers (433 +/- 19 kg initial BW) were blocked by BW and assigned randomly to 1 of 4 treatments (0, 10, 20, or 30% dry-rolled field pea, DM basis; 6 pens/treatment). In Exp. 3, 80 beef steers (372.4 +/- 0.4 kg initial BW) were assigned randomly to 1 of 4 treatments (0, 18, 27, or 36% cracked field pea, DM basis; 4 pens/treatment). Field pea replaced a portion of the grain (dry-rolled and high moisture corn, dry-rolled corn, and barley and barley sprouts; Exp. 1, 2, and 3, respectively) and protein supplement. In Exp. 1, field pea inclusion decreased DMI linearly (P = 0.03), whereas ADG and G:F were not affected by treatment (P > or = 0.17); however, dietary NE(g) increased quadratically with increasing field pea level (P = 0.04). Fat thickness responded quadratically (P = 0.008) where heifers fed 20% field pea had greatest fat thickness and 30% field pea inclusion the least. Marbling tended (P < or = 0.09) to respond quadratically as field pea increased. No differences (P > or = 0.17) were observed for HCW, LM area, or KPH. In Exp. 2, DMI, ADG, G:F, dietary NE(g), HCW, marbling, LM area, 12th-rib fat, and USDA yield grade (YG) were unaffected by dietary field pea inclusion (P > or = 0.12). In Exp. 3, marbling score increased linearly (P = 0.05), fat thickness increased quadratically (P = 0.01), and YG tended to increase (P = 0.07) quadratically as field pea increased. Field pea inclusion did not affect (P > or = 0.38) DMI, ADG, G:F, dietary NE(g), HCW, or LM area. These results indicate that field pea can be included successfully into rations at levels up to 36% of DM without negatively affecting growth performance and most carcass characteristics of finishing beef cattle; however, effects on marbling score were variable. These data also indicate the energy content of field peas is similar to cereal grains, such as corn and barley, when included in high-concentrate finishing diets.

Influence of supplementation with corn dried distillers grains plus solubles to growing calves fed medium-quality hay on growth performance and feeding behavior1

To determine the effect of increasing supplementation of corn dried distillers grains plus solubles (DDGS) on growth performance and feeding behavior, 70 steer calves (287 ± 10 kg of BW) were blocked by BW to 3 pens equipped with Insentec feeders. For 84 d, calves were fed medium-quality grass/legume hay offered for ad libitum intake and provided 1 of 3 dietary supplemental treatments (n = 7 or 8 steers per treatment within each pen; n = 23 or 24 per treatment): 1) nothing, 2) DDGS at 0.5% of BW daily (DM basis), and 3) DDGS at 1% of BW daily (DM basis). Hay intake (kg/d and % of BW daily) decreased linearly (P < 0.001) as DDGS supplementation increased. Total DMI (kg/d and % of BW) increased linearly (P < 0.001) with DDGS supplementation. Average daily gain and gain efficiency (G:F) responded quadratically (P ≤ 0.006) as G:F increased to a lesser extent when DDGS supplementation increased from 0.5 to 1% than from 0 to 0.5%. Meals (number per day) and time eating per meal for hay and total diet decreased linearly (P ≤ 0.006) with increasing DDGS supplementation. Time eating per day for hay responded quadratically (P < 0.001) and decreased to a greater extent when increasing from 0 to 0.5% DDGS supplementation than from 0.5 to 1% DDGS. Feed intake per minute (eating rate) for hay and total diet increased linearly (P ≤ 0.05) with increasing DDGS supplementation. On d 84, LM area, back fat thickness, and rump fat thickness increased linearly (P ≤ 0.006) with increasing DDGS supplementation. There were significant day × treatment interactions (P < 0.001) for plasma glucose and urea-N concentrations. Glucose did not change over the feeding period in control steers but increased in both supplemented groups. Urea-N decreased for control steers over the feeding period whereas urea-N increased in supplemented steers. In conclusion, supplementation of DDGS in amounts of 0.5 or 1% of BW daily can be used to reduce hay intake and improve ADG and G:F in growing steers fed medium-quality hay. Additionally, DDGS supplementation alters feeding behavior.