M.L. Looper

BOARD-INVITED REVIEW: St. Anthony's Fire in livestock: Causes, mechanisms, and potential solutions

After a brief history of ergot alkaloids and ergotism, this review focuses on the metabolism and mechanisms of action of the ergot alkaloids. The authors provide models of how these alkaloids afflict grazing livestock under complex animal-plant/endophyte-environmental interactions. Alkaloid chemistry is presented to orient the reader to the structure-function relationships that are known to exist. Where appropriate, the medical literature is used to aid interpretation of livestock research and to provide insight into potential modes of action and alkaloid metabolism where these are not known for livestock. In closing the paper, we discuss management of ergot alkaloid intoxication in livestock and future research needs for this field of study.

Bacteriophage isolated from feedlot cattle can reduce Escherichia coli O157:H7 populations in ruminant gastrointestinal tracts.

Escherichia coli O157:H7 can live undetected in the gut of food animals and be spread to humans directly and indirectly. Bacteriophages are viruses that prey on bacteria, offering a natural, nonantibiotic method to reduce pathogens from the food supply. Here we show that a cocktail of phages isolated from commercial cattle feces reduced E. coli O157:H7 populations in the gut of experimentally inoculated sheep. A cocktail of phages was used in order to prevent the development of resistance to the phages. In our first in vivo study we found that our cocktail of phages reduced E. coli O157:H7 populations in the feces of sheep (p < 0.05) by 24 hours after phage treatment. Upon necropsy, populations of inoculated E. coli O157:H7 were reduced by phage treatment in both the cecum (p < 0.05) and rectum (p < 0.1). In our second in vivo study, several ratios of phage plaque-forming units (PFU) to E. coli O157:H7 colony-forming units (CFU) were used (0:1, 1:1, 10:1, and 100:1 PFU/CFU) to determine the most efficacious phage dose. A 1:1 ratio of phage to bacteria was found to be more effective (p < 0.05) than either of the higher ratios used (10:1 or 100:1). Ruminal levels of E. coli O157:H7 were not significantly reduced (p > 0.10) in any of the studies due to relatively low inoculated E. coli O157:H7 ruminal populations. Our results demonstrate that phage can be used as a preharvest intervention as part of an integrated pathogen reduction scheme.

Variation in the faecal shedding of Salmonella and E. coli O157:H7 in lactating dairy cattle and examination of Salmonella genotypes using pulsed‐field gel electrophoresis

Aims:  To examine the variability in faecal shedding of Salmonella and Escherichia coli O157:H7 in healthy lactating dairy cattle and to evaluate the genetic relatedness of Salmonella isolates.

Antimicrobial susceptibility and factors affecting the shedding of E. coli O157:H7 and Salmonella in dairy cattle.

Aims: To examine factors affecting faecal shedding of the foodborne pathogens Escherichia coli O157:H7 and Salmonella in dairy cattle and evaluate antimicrobial susceptibility of these isolates.

Hemodynamics are altered in the caudal artery of beef heifers fed different ergot alkaloid concentrations.

Doppler ultrasonography was used to compare blood flow characteristics in the caudal artery of heifers fed diets with endophyte (Neotyphodium coenophialum) noninfected (E-, 0 microg of ergovaline/g of DM), a 1:1 mixture of endophyte-infected and E- (E+E-; 0.39 microg of ergovaline/g of DM), or endophyte-infected (E+, 0.79 microg of ergovaline/g of DM) tall fescue (Lolium arundinaceum) seed. Eighteen crossbred (Angus x Brangus) heifers [345 +/- 19 kg (SD)] were assigned to individual pens and fed chopped alfalfa hay plus a concentrate that contained E- tall fescue seed for 7 d during an adjustment period. A 9-d experimental period followed with feeding treatments of chopped alfalfa hay plus a concentrate with E+, E-, or E+E- seed being assigned randomly to pens. Doppler ultrasound measurements (caudal artery luminal area, peak systolic velocity, end diastolic velocity, mean velocity, heart rate, and flow rate) and serum prolactin were monitored during the adjustment (3 baseline measures) and during the experimental period (7 measures). Statistical analyses compared proportionate differences between baseline and responses at 3, 27, 51, 75, 171, and 195 h from initial feeding of the experimental diets. Serum prolactin concentrations for E+ and E+E- diets were less (P < 0.001) than baseline concentrations beginning at 27 and 51 h, respectively, from initial feeding of the diets. Although baseline measures were taken when ambient temperatures were likely below thermoneutrality, caudal artery luminal cross-sectional area in E+ heifers had declined (P = 0.004) from baseline by 27 h and remained less (P < 0.02) until 195 h, and caudal artery luminal area declined (P = 0.004) in E+E- heifers from baseline by 51 h and remained less (P < 0.07) until 171 h. Blood flow rate was slower than the baseline rate at 51 h for E+ (P = 0.058) and E+E- (P = 0.02 heifers, but blood flow remained slower in E+E- heifers for 48 h, whereas it remained slower in E+ heifers for 96 h. Adjustments in artery luminal area and blood rate with the 3 diets appeared to parallel the increases in ambient temperature. Heifers fed a diet containing a larger amount of ergot alkaloids had less of a response to ambient temperature than heifers consuming the diet with less or no ergot alkaloids.

Calving traits of crossbred Brahman cows are associated with Heat Shock Protein 70 genetic polymorphisms

Stress proteins and their genetic polymorphisms have been associated with decreased male and female fertility. Objectives were to: (1) identify single nucleotide polymorphisms (SNP) located in the promoter region of the bovine heat shock protein 70 (Hsp70) gene, and (2) evaluate associations between Hsp70 SNP, Julian calving date, and calving rates of crossbred Brahman cows. Specific primers were designed for PCR amplification of a 539 base segment of the bovine Hsp70 promoter (GenBank accession number M98823). Eleven single nucleotide polymorphisms were detected; one deletion at base position 895 (n=37), seven transitions (G1013A, n=2; G1045A, n=8; C1069T, n=4; A1096G, n=14; G1117A, n=12; T1134C, n=7; and T1204C, n=56), and three transversions (A1125C, n=53; G1128T, n=51; and C1154G, n=11). Cows that were homozygous for the minor allele at transversion site A1125C or G1128T had lesser (P<0.05) calving percentages than cows that were homozygous for the primary allele (48 vs. 75%). Homozygous and heterozygous deletion of cytosine at base 895 resulted in lower (P<0.05) calving percentages than homozygous cytosine cows (8, 50, 82%; respectively). In addition, homozygous deletion cows had the latest (P<0.05) Julian calving date. Eighteen Hsp70 promoter haplotypes were deduced, and seven of those haplotypes (n=37) included the deletion at base 895. Thirty-two cows had the haplotype consistent with the GenBank sequence and the remaining 30 cows had a SNP other than the deletion. Cows with deletion haplotypes had a lesser (P<0.05) calving percentage, and the latest (P<0.05) Julian calving date when compared with cows having other SNP haplotypes. Results from the present study suggest that the promoter region of the bovine Hsp70 gene is polymorphic and may be useful in selecting cows with a greater fertility.

Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls

Sixteen (mean age = 1.1 +/- 0.1 yr; mean BW = 478 +/- 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P < 0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 +/- 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P < 0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P < 0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P < 0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P < 0.06) in August than July. Concentrations of cortisol and testosterone were not (P > 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.

Endocrine factors and ovarian follicles are influenced by body condition and somatotropin in postpartum beef cows.

Multiparous beef (1/4 to 3/8 Bos indicus; n = 99) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine (b) ST on the number of follicles, diameter of largest follicle, and serum concentrations of IGF-I, triiodothy-ronine (T3), thyroxine (T4), and prolactin. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg, s.c.) on d 32, 46, and 60 postpartum. On d 60, all cows received a controlled internal drug-releasing (CIDR) device for 7 d and PGF(2alpha) at CIDR removal (CIDR-PGF(2alpha)). Blood samples (7 mL) were collected at each bST treatment and d 39 and 67 postpartum. Ultrasound was performed 1 d after CIDR-PGF(2alpha) to determine the number of small (2 to 9 mm) and large (>/=10 mm) follicles and the diameter of largest follicle. Cows treated with bST in low BC had increased (P < 0.05) IGF-I vs. low-BC non-bST-treated cows on d 39, 46, 60, and 67 postpartum. Prolactin and T3 were greater (P < 0.05) in moderate-BC than in low-BC cows on all sample dates. Thyroxine was greater (P < 0.001) in moderate-BC cows on d 46, 60, and 67 compared with low-BC cows. On d 67, bST-treated cows had greater (P < 0.05) T4 compared with non-bST-treated cows. Diameter of the largest follicle 1 d after CIDR-PGF(2alpha) was greater (P < 0.01) in anestrous cows treated with bST than for non-bST-treated anestrous cows. Diameter of the largest follicle was correlated with concentrations of IGF-I (r >/= 0.18; P </= 0.08), T3 (r >/= 0.17; P </= 0.10), and prolactin (r >/= 0.20; P </= 0.06). Treatment with bST increased IGF-I in low-BC cows, and IGF-I was correlated with the diameter of the largest follicle 1 d after CIDR-PGF(2alpha). Undernutrition of cattle may be communicated to the hypothalamic-pituitary-ovarian axis via metabolic hormones including IGF-I, thyroid hormones, or prolactin.

Examination of heat stress and stage of lactation (early versus late) on fecal shedding of E. coli O157:H7 and Salmonella in dairy cattle.

Mature, healthy lactating dairy cattle were sampled on two farms in the southwestern United States to examine the effects of heat stress (Experiment I) and stage of lactation (Experiment II) on the fecal shedding of E. coli O157:H7 and Salmonella. To examine the effects of heat stress, fecal samples were collected from 45 cows at 7:00 AM (coolest part of the day) and 5:00 PM (hottest part of the day) in August 2002 on a 250 cow dairy. The study was replicated one month later (n = 170 total samples). A temperature-heat index (THI) was calculated for each sampling time. In Experiment II, stage of lactation was examined by sampling lactating dairy cattle early [< 60 days in milk (DIM)] and late (> 150 DIM) in the lactation cycle in the summer of 2001. The study was replicated the following summer (60 cows/group/replicate; n = 240 total samples). For Experiment I, THI averaged 75 and 82 for the AM and PM samplings, respectively, indicating the cows were beginning to experience heat stress in the morning and by afternoon were in severe heat stress. The shedding of E. coli O157:H7 tended to be higher (p = 0.09) in the afternoon sampling of the first replicate, however was not different in the second replicate or when both replicates were pooled (p > 0.10). Salmonella shedding was not different (p > 0.10) at any sampling time with nearly 100% of the cows positive. Stage of lactation had no effect on the number of cows shedding E. coli O157:H7 (p > 0.10). Salmonella shedding tended to be higher (p = 0.09) in early lactation cows in the first replicate, while in the second replicate more late lactation cows were shedding Salmonella (p < 0.05); however, there were no differences due to stage of lactation when replicates were pooled (p > 0.10). While further research is needed, results of this research highlight the variability in pathogen shedding in healthy dairy cattle and indicate that environmental factors and/or production demands may influence shedding patterns of E. coli O157:H7 and Salmonella.

Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue1

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.