Plane of nutrition x tick burden interaction in cattle: effect on fecal composition.

Effective tick management on grazing animals is facilitated by accurate noninvasive detection methods. Fecal analysis provides information about animal health and nutrition. Diet affects fecal composition; stress may do likewise. The constituents in feces that may be affected by tick burdens and in turn affect near-infrared spectra have not been reported. Our objective was to examine the interaction between plane of nutrition and tick burden on fecal composition in cattle. Angus cross steers (n = 28; 194 ± 3.0 kg) were assigned to 1 of 4 treatments (n = 7 per group) in a 2 × 2 factorial arrangement: moderate (14.0 ± 1.0% CP and 60 ± 1.5% TDN) vs. low (9.0 ± 1.0% CP and 58 ± 1.5% TDN) plane of nutrition and control (no tick) vs. tick treatment [infestation of 300 pair of adult Lone Star ticks (Amblyomma americanum) per treated animal]. Fecal samples were collected at approximately 0700 h on d -7, 0, 7, 10, 14, 17, and 21 relative to tick infestation. Fecal constituents measured were DM, OM, pH, Lactobacillus spp., Escherchia coli, acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, IgA, and cortisol. Experimental day affected (P < 0.05) all constituents measured. Plane of nutrition affected (P < 0.05) DM, OM, VFA, and IgA. Tick treatment numerically (P = 0.13) reduced cortisol. A multivariate stepwise selection model containing cortisol and E. coli values on d 10 and d 14 accounted for 33% of the variation in daily adult female tick feeding counts across both planes of nutrition (P < 0.07). Within the moderate plane of nutrition, a model containing only cortisol on d 10 and d 14 described 59% of the variation in the number of feeding ticks (P < 0.02). Similarly, a model including cortisol, propionate, isovalerate, and DM at d 10 and d 14 d described 95% of the variation in total feeding ticks in the low plane of nutrition. Of the constituents measured, fecal cortisol offers the best possibility of noninvasively assessing stress by way of a single assay but the presence of ticks would still need to be confirmed visually. Although several constituents measured in this study should exist in sufficient quantity to directly affect near-infrared spectra, none stood out as a clear descriptor of prior observed differences in fecal spectra between tick-treated versus non-tick-treated animals. There were, however, groups of fecal constituents related to daily adult female tick feeding numbers (as a visual estimation of tick stress).

Plane of nutrition by tick-burden interaction in cattle: effect on growth and metabolism.

Ticks are external parasites, which pose a significant economic burden to domestic animal agriculture. The effects of ticks on grazing animals may be exacerbated during periods of low nutrition, such as those encountered during drought. It is not completely understood how plane of nutrition and tick burden interact to affect metabolism in cattle. The objective of the current research was to examine the plane of nutrition by tick-burden interaction in cattle and determine the effects of this interaction on physiological indicators of growth and metabolism. Eight-month-old Angus cross steers (n = 28, 194 ± 3.0 kg) were stratified by pretrial BW and DMI into 1 of 4 groups (n = 7/group) in a 2 × 2 factorial arrangement. Categories were: moderate (14.0 ± 1.0% CP, 60 ± 1.5% TDN) vs. low (9.0 ± 1.0% CP, 58 ± 1.5% TDN) plane of nutrition and control (no tick) vs. tick treatment (300 pair of adult Amblyomma americanum per treated animal). Steers were individually fed their respective experimental diets ad libitum and feed intake was monitored for 35 d before and 21 d after the start of tick infestation (d 0). Blood samples were harvested via coccygeal venipuncture on d -7, 0, 7, 8, 9, 10, 11, 13, 17, and 21. Plasma cortisol and IGF-I were determined by RIA. Metabolic indicators were determined by colorimetric assay. Steers weighed 195 ± 6 kg on d -35, but on d -7 and d 21, the moderate steers weighed more than the low steers (244.1 ± 8.7 vs. 227.7 ± 8.4 kg, P < 0.07; and 283.4 ± 8.0 vs. 244.0 ± 7.9 kg, P < 0.001, respectively). Cortisol was affected by plane of nutrition and treatment (P < 0.08). Insulin-like growth factor-I was greater (P < 0.01) in moderate than in low and control animals (P < 0.02), compared with tick-treated animals. Tick treatment had no effect (P > 0.05) on any of the metabolites measured in this study. Plane of nutrition affected (P < 0.02) albumin, blood urea nitrogen, and glucose in that values from the moderate group animals were greater than those from the low group. Although cortisol was related to both tick treatment and nutritional status in the current study, with respect to the combination of parasitism and suboptimal nutrition, IGF-I was the most highly indicative constituent measured. Tick burden affected various characteristics of growth and metabolism in these growing cattle and the effects were exacerbated by a low plane of nutrition.

Host selection by questing female Amblyomma maculatum Koch, to cattle with feeding male ticks in southern Texas.

The feeding associations among male and female Gulf Coast ticks, Amblyomma maculatum Koch, were examined using archived data obtained from untreated free-ranging cattle pastured on native rangeland. There was significant evidence of a relationship between male and female tick presence on hosts (p-value <0.0001), suggesting that A. maculatum females will more frequently be attracted and attach to grazing cattle with feeding males than those without. Seasonal data were tested to develop prediction models that estimate the number of female (F) ticks parasitizing cows relative to the number of male (M) ticks present for both early (F=0.090+0.162 M) and late season (F=2.098+0.337 M). These equations could be used to optimize the scheduling of surveillance and control efforts for Gulf Coast tick adults and may establish baseline dosage for pheromone applications.

Effects of a lone star tick (Amblyomma americanum) burden on performance and metabolic indicators in growing beef steers.

We examined the response of selected animal performance, endocrine, immune, and metabolic factors from 13 steers (254+/-6.1 kg) with and without a lone star (Amblyomma americanum) tick burden during progressive days of the tick feeding cycle. Steers were randomly assigned to either non-treated controls or treated with 300 adult pair of A. americanum per animal. Animals were weighed and blood sampled on days -7, 0, 10, 14, 21, 28, and 35 relative to tick treatment. Tick treatment did not affect (P<0.1) animal performance. Experimental day did (P<0.05) affect body weight gain and dry matter intake. Tick treatment did not affect (P<0.1) metabolic indicators. Experimental day affected (P<0.05) IGF1 and lactate, tended to affect cortisol (P<0.07), but did not affect (P<0.1) glucose concentrations. Tick treatment did not significantly (P<0.1) affect growth hormone receptor (GHR) mRNA in liver, but liver tissue from treated animals had numerically lower GHR mRNA than did tissue from control animals. Day had a significant (P<0.05) effect on liver GHR mRNA. There was a significant treatment by day interaction (P<0.05) for liver IGF1 gene expression, as IGF1 mRNA was reduced in tick-treated cattle versus control cattle on day 35. Overall, liver IGF1 gene expression was lower (P<0.05) in tick than in control animals while there was no effect (P>0.1) due to day. Within the tick-treated group, correlations were found between quantitative female tick feeding characteristics and host metabolic indicators. Feeding by adult female lone star ticks did cause acute stress in growing beef steers on a moderate plane of nutrition as indicated by some physiologic indicators. In particular there may be longer term effects on the somatotrophic axis in the liver which could affect subsequent (i.e. feedlot) performance. It is not known how these observed effects would be manifest under a lower plane of nutrition, as is common and may become more so within the current native range of A. americanum. Other acute effects due to tick feeding may have been masked by the effects of handling and invasive sampling. Non-invasive experimental procedures are called for in order to study the effects of a stressor such as arthropod infestation on grazing animals. Future research efforts will be aimed at non-invasively elucidating the effects of tick stress on grazing animals under various nutritional environments.

Genetic variation in 12S and 16S mitochondrial rDNA genes of four geographically isolated populations of Gulf Coast ticks (Acari: Ixodidae).

Single-strand conformation polymorphism (SSCP) analysis was examined in a 303-bp region of the 16S and 12S mitochondrial rDNA genes to study haplotype frequencies among populations of Gulf Coast ticks collected from Refugio Co., TX, Payne Co., OK, and two sites in Osage Co., KS. Seven haplotypes were identified from the 16S rDNA gene fragment, whereas only two haplotypes were detected from the 12S fragment. Only the results from the 16S rDNA fragment are discussed. Haplotype diversity was greatest in Kansas (site 1), where three of the four haplotypes detected were unique to this site. All Gulf Coast tick populations shared the fourth haplotype. Two haplotypes were determined for Texas and Oklahoma populations, one of which appeared only in Texas, whereas the other was shared. Nei's haplotype diversity (h) indicated that the Texas population was relatively homogeneous (15%), whereas the remaining populations were heterogeneous (42-59%), although the Bonferroni confidence interval found no significant differences (P < 0.05). Nucleotide sequencing of the seven haplotypes and subsequent phylogenetic analysis using neighbor joining showed a monophyletic relationship among these haplotypes. One haplotype, shared by both Oklahoma and Kansas (site 2), was basal to the remaining haplotypes and formed a distinct clade. Two haplotypes, both from Kansas (site 1), formed a unique clade, whereas the remaining four haplotypes were unresolved polytomies.

Tolerance and compensatory response of rice to sugarcane borer (Lepidoptera: Crambidae) injury.

A 3-yr field experiment was conducted to evaluate the tolerance and compensatory response of rice (Oryza sativa L.) to injury caused by sugarcane borer, Diatraea saccharalis (F.), as affected by cultivar (Cocodrie, Francis, and Jefferson), stage of crop growth during which the injury occurred (third tiller stage, panicle differentiation stage, and heading stage), and sugarcane borer density. The proportion of rice tillers with sugarcane borer injury (leaf and leaf sheath injury and/or stem injury) was lower when injury occurred at the third tiller stage (0.05) than at panicle differentiation (0.19) and heading (0.18). When injury occurred at the two latter stages, both the proportion of tillers with injury and the proportion of tillers with stem injury were negatively correlated with rainfall. Rainfall resulted in dislodgement and mortality of sugarcane borer eggs and larvae before the larvae entered the stems. Rice plant density in this study (111.1 plants/m2) was higher than recorded for previous research on rice compensation using potted rice or conducted in low-density hill production systems (26.7-51.3 plants/m2). Two mechanisms of within-plant tolerance/compensation were observed. Stem injured plants produced approximately 0.69 more tillers than uninjured plants, whereas tillers with leaf and leaf sheath injury produced larger panicles, up to 39.5 and 21.0% heavier than uninjured tillers, when injury occurred at third tiller stage and at panicle differentiation, respectively. Rice yield was not reduced with up to 23% injured tiller and up to 10% injured stems at the third tiller stage, 42% injured tillers and 17% injured stems at panicle differentiation, and 28% injured tillers and 14% injured stems at heading. Significant between-plant compensation was not detected, suggesting competition between adjacent plants is not significantly reduced by injury. Our results suggest that rice can tolerate and/or compensate for a level of stem borer injury previously considered to be economically damaging.

Mating success of two geographically distinct populations of Gulf Coast ticks, Amblyomma maculatum Koch.

Gulf Coast ticks collected from Refugio Co., TX and Osage Co., KS are reproductively compatible despite differences in genetic haplotypes, geographic separation and seasonal phenologies. Two heifers per mating combination (TX males x TX females, KS males x KS females, TX males x KS females, KS males x TX females) were each infested with 360 pairs of Gulf Coast ticks. Only mean pre-oviposition and mean egg conversion efficiency index for the Texas male-Kansas female mating were significantly different (p<0.05) from other mating treatments. These females began oviposition 1-day later and used 4% less body mass toward egg production when compared to site-specific matings. However, the overall trend in reproductive performance of reciprocal tick matings was slightly lower than that of site-specific matings. There appear to be no pre-zygotic barriers to mating among Gulf Coast ticks from these Texas and Kansas populations.

Feeding predilection of Gulf Coast tick, Amblyomma maculatum Koch, nymphs on cattle.

Gulf Coast tick nymphs successfully attached and fed on cattle after being freely released. Six Hereford heifers were each infested with approximately 2000 Gulf Coast tick nymphs, three with a strain originating from Refugio Co., TX, and three with ticks from Osage Co., KS by free release on the head and legs to simulate field acquisition of questing nymphs. Two re-infestations were conducted, the first at 7 days and the second at 28 days. Nymph dispersal was estimated by daily inspection of 22 body areas and removal of engorging ticks from the third to the fifth days post-infestation. Total recovery of engorging Texas nymphs was 3.0, 10.2, and 0% and Kansas nymphs was 21.5, 3.3, and 0% for infestations one, two and three, respectively. Immunological resistance to tick infestation expressed as cellular hypersensitivity was evident against Kansas nymphs in the second infestation and against both tick strains in the third infestation. Ticks removed from the withers, midline, and tail-head areas accounted for 68% of the total nymphs recovered in the first two infestations. Within these areas, nymphs were observed to aggregate in small spots where the hair was less dense or naturally parted and the remainder were found scattered in dense hair.

Effects of pyriproxyfen on off-host water-balance and survival of adult lone star ticks (Acari: Ixodidae).

Newly engorged nymphs of the lone star tick, Amblyoma americanum (L.), were continuously exposed to 4 microg/cm2 of pyriproxyfen residues in glass vials. Treatment of engorged nymphs (n = 285) resulted in significant molting inhibition, with more than one-fourth (26.7%, n = 76) of nymphs dying before or during ecdysis. Treatment effects were evident among ticks that molted to the adult stage, with 26.7% (n = 76) of females, and 17.9% (n = 51) of males exhibiting moribund physical characteristics (i.e., lethargy; dull, discolored and desiccated cuticles; lacking full locomotor competency). A few molted adult ticks (10 males, four females) were dead upon inspection. Only 11.2% of pyriproxyfen treated, emergent females (n = 32), and 11.5% of treated emergent males (n = 25) from 285 ticks treated as engorged nymphs, exhibited normal physical appearance and possessed a full range of locomotor activity. Treated adult ticks maintained within a desiccating environmental chamber at 0% RH and 23 degrees C, had significantly accelerated whole-body water loss rates in comparison to untreated males and females maintained under the same environmental conditions. Additionally, treated adult ticks maintained under optimal environmental conditions (23 degrees C and >95% RH) sustained 100% mortality within 32 d following assignment to these conditions (or 79 d posttreatment as engorged nymphs), whereas untreated ticks had 0% mortality for the same duration of time. Results demonstrate that continuous exposure of nymphs to pyriproxyfen disrupted molting, and accelerated both whole-body water loss and subsequent mortality among emergent adult ticks.

Utilization of soy protein isolate and konjac blends in a low-fat bologna (model system).

Low-fat bologna formulations (LFBMS, <2.0% fat) were manufactured in a model system with two levels (0.5 or 1%) of two konjac blends (KB; KSS=konjac flour/starch and KNC=konjac flour/carrageenan/starch), and three levels (0, 2.2, 4.4%, DWB) of prehydrated soy protein isolate (SPI) to replace 0, 2 and 4% of the meat protein, respectively. Compared to 0.5% KB, the 1% level reduced (p<0.05) protein solubility (PS), vacuum purge (VP, %) and texture profile analysis (TPA) hardness. LFBMS containing KNC had higher (p<0.05) cooking yields, TPA fracturability and shear stress, but lower (p<0.05) expressible moisture (EM), VP values and TPA cohesiveness than KSS. Replacement of 4% meat protein with SPI increased (p<0.05) pH and yellowness (b*), but decreased (p<0.05) redness (a*), PS, EM and most textural characteristics, whereas no differences (p>0.05) were observed between 0 and 2% of meat protein replacements with SPI for most characteristics.

Survival and water-balance characteristics of unfed adult Amblyomma cajennense (Acari: Ixodidae).

Off-host survival, water balance, and cold tolerance of unfed adult, Cayenne ticks, Amblyomma cajennense (F.), were examined to evaluate species characteristics important to zoogeography and off-host ecology. Survivorship decreased when males and females were subjected to progressively drier constant environmental conditions. Average maximum survival was 641.2 and 682.5 d at 85% RH and 23 degrees C (2.98 mm Hg) for males and females, respectively. Mean survival in both sexes was progressively less variable in drier conditions. Slopes of log-linear models of survival days based on saturation deficit (mm Hg) were significantly different between males and females at 50%, but not at 25 or 0%. Whole-body water loss rates for 4-wk-old adults were measured at 0% RH and 23 degrees C until ticks became nonambulatory. The mean whole-body water loss rate of females, 0.06128% h-1, was 11.3% less than for males, 0.06914% h-1. Although nonambulatory ticks appeared dead, >1/2 of the individuals from each sex regained ambulatory status after they were removed from 0% RH and exposed to 96% RH for 24 h. Among these, male ticks averaged 0.44 more recuperative (ambulatory) cycles than females, although, the duration encompassing all recuperative cycles was generally longer for females and on average, females gained 8.16% more weight than males upon each rehydration. Estimates of the mean critical equilibrium activity for males and females were 0.74 av and 0.79 av, respectively. A. cajennense adults were found to be less tolerant to -12.5 degrees C than adult lone star ticks, Amblyomma americanum (L.), whose distribution encompasses more temperate regions. Although A. cajennense exhibit little host preference and are capable of extended off-host survival, the establishment of populations beyond this species zoogeographic distribution may be constrained by an intolerance to cold.

Tracheal mucociliary transport rate in awake dogs.

To measure tracheal mucociliary transport rate (TMTR) in awake dogs, restrained in dorsal recumbency, 99mtechnetium-labeled macroaggregated albumin was administered by tracheal injection, and the cephalic movement of boluses containing the radiopharmaceutical was detected by a gamma camera positioned lateral to the dog's head and neck. The distance traveled by each bolus was measured, relative to external markers placed a known distance apart. Tracheal mucociliary transport rates were calculated by dividing the measured distance of radiopharmaceutical movement by elapsed time. The technique was efficient and well tolerated. Mean (+/- SD) TMTR was 35.3 +/- 15.9 mm/min. Significant (P = 0.029) difference in TMTR was found between males and females, but significant difference attributable to age of the dog was not detected. This method of measuring TMTR in awake dogs has potential for evaluation of clinical animal patients with suspected tracheal mucociliary abnormalities.

Use of orthopedic markers for quantitative determination of proximal radial and ulnar growth in foals.

Cortical bone screws were implanted into the proximal portion of the right and left radius and ulna of 6 newborn Quarter Horse foals as radiographic markers for measurement of growth. Distance between markers on a lateral radiographic view was measured. Radiographs were taken at 2-week intervals until the horses were 8 weeks old, at 4-week intervals until they were 48 weeks old, and at 12-week intervals until they were 72 weeks old. The proximal radius and ulna grew at similar rates during the 72-week period of evaluation, and growth continued throughout 72 weeks. The proximal radius grew 3.5 cm, and the ulna grew 3.4 cm. Although the rates of growth were similar, growth from the ulnar physis contributed only to the length of the olecranon; growth was not transmitted to the ulnar diaphysis distal to the cubital joint. The proximal radius slid distally in relation to the ulna as growth occurred at the proximal radial physis. These findings suggest that transfixing the ulna to the radius while growth is occurring at the proximal radial physis impedes the natural shifting process, and subluxation of the elbow can result. Severity of subluxation would be inversely related to the age of the horse at the time of transfixation.

Modeling embryo development and emergence of Boophilus annulatus (Acari: Ixodidae).

Guanine accumulation in Boophilus annulatus (Say) at 15 temperatures (3-42 degrees C) showed embryonic development from 9 to 42 degrees C. Guanine concentrations steadily increased over the period of development. Eggs at 17-36 degrees C achieved hatch (requiring 54-12 d, respectively), and eclosion dates were estimated for larvae developing at 12 degrees C (day 172) and 14 degrees C (day 154) using linear regression. Development rates from 12 to 36 degrees C are described by a six-parameter biophysical model for poikilothermic organisms which defines three temperature development phases characterized by low-temperature (TL, 284.7 degrees K or 11.7 degrees C) and high-temperature (TH, 307.7 degrees K or 34.7 degrees C) enzyme inactivation and a linear region (RHO25, 0.049 day-1) of no temperature inhibition. A model of emergence distribution was derived by fitting a Weibull function to a single distribution representative of the normalized emergence distribution at each temperature.

Effects of sequential infestations of Dermacentor albipictus and Amblyomma americanum (Acari: Ixodidae) on overwintering beef cows in west-central Texas.

Infestations of winter ticks, Dermacentor albipictus (Packard), observed on mature black Angus cows, reached peak levels in January and diminished through March. Infestations of adult lone star ticks, Amblyomma americanum (L.), began in mid-January and increased through May. Cows receiving Ectrin, Taktic, or Deltox treatments on 13 December and 21 February experienced significantly less weight loss and entered the subsequent breeding season with higher average body weight than untreated cows. In a separate study, lactating Brangus and Brangus-cross cows, equally infested by natural populations of these ticks, were provided five supplement treatment regimens, fed individually with quantities adjusted for body weight and condition score. Groups receiving supplementation highest in crude protein and digestible energy lost significantly less weight and experienced the least amount of deterioration in body condition. Performance among these groups was influenced by the amount of digestible energy and the period in which increased levels of digestible energy were fed. Cows receiving the supplement highest in protein coupled with an increase in digestible energy from 10 to 60 Mcal/kg W0.75 on 16 January experienced the smallest average change in condition score and weight parameters.