Aggression and Nearest Neighbour Distances in Female Reindeer during the Rut

Data on nearest neighbours and aggressive behaviour were collected within rutting groups of semi-domesticated reindeer (Rangifer t. tarandus L.) in a 1300-ha pasture in Finnish Lapland, and wild forest reindeer (Rangifer t. fennicus Lönnb.) in a 15-ha enclosure in Central Finland. Adult cows of forest reindeer charged yearling males, yearling females and calves in that order of decreasing frequency. Semi-domesticated reindeer cows rushed yearling females more often than they did one another. One suggested influence of antagonism by cows were the observed intragroup associations of yearling females. Cows were tolerant toward their own yearling females, but not toward their own yearling males. Although no maternal aggression toward calves was found, male calves moved away more often from their mothers than did female calves during the post-rut period.     

The influence of ambient temperature on metabolism and body temperature of newborn and growing reindeer calves (Rangifer tarandus tarandus L.)

Thermoregulatory capacities of 51 reindeer calves (Rangifer tarandus tarandus L.) aged 1-35 days were studied at -26.5 to +35.0 degrees C ambient temperatures at Kaamanen reindeer research station, Finland (69 degrees 10' N) during calving periods in May 1981 and May-July 1982. The newborn calves aged 1-4 days maintained a high body temperature (Tre) (mean +40.2 degrees C) even at the lowest experimental temperature of -22.5 degrees C by increasing their metabolic rate five-fold above the level at +11.0 degrees C. Heat production of the new-born calves was largely based on the metabolism of brown adipose tissue, stimulated by cold-induced discharge of the sympathetic nervous transmitter, noradrenaline (NA). Sensitivity of the calves to exogenous NA disappeared during the first 3-4 weeks of life. Thermal conductance of the calves was low at low ambient temperatures, but rose strongly as Ta increased above +10 degrees C. The extensive peripheral cooling, especially in the feet, was demonstrated in the calves aged 1-10 days. The lowest foot temperature (+10.5 degrees C) was measured in a 4-day-old calf at -14.5 degrees C. Slight shivering thermogenesis was recorded in the calves aged 1-4 days and occasionally in the older calves at low values of Ta. Shivering appears to be a reserve mechanism against severe cold. At about +20 degrees C and above the calves increased their Tre (approximately 1 degree C), oxygen consumption and heart rate. In the newborn calves oxygen consumption rose four- to five-fold and in 1-month-old calves about two-fold. Fast growing calves (maximum 400 g/day) appear to be more stressed by heat than by cold exposure.     

Performance and plasma metabolites of dairy calves fed starter containing sodium butyrate, calcium propionate or sodium monensin

This study was conducted to examine the influence of supplementation of sodium butyrate, sodium monensin or calcium propionate in a starter diet on the performance and selected plasma metabolites (plasma glucose, non-esterified fatty acids and β-hydroxybutyrate) of Holstein calves during pre- and post-weaning periods. Twenty-four newborn Holstein calves were housed in individual hutches until 10 weeks of life, receiving water free choice, and fed four liters of milk daily. Calves were blocked according to weight and date of birth, and allocated to one of the following treatments, according to the additive in the starter: (i) sodium butyrate (150 g/kg); (ii) sodium monensin (30 mg/kg); and (iii) calcium propionate (150 g/kg). During 10 weeks, calves received starter ad libitum, while coast cross hay (Cynodon dactylon (L.) pers.) was offered after weaning, which occurred at the 8th week of age. Weekly, calves were weighted and evaluated for body measurements. Blood samples were taken weekly after the fourth week of age, 2 hours after the morning feeding, for determination of plasma metabolites. No differences were observed among treatments for starter or hay intake, BW and daily gain of the animals. Mean concentrations of selected plasma metabolites were similar in calves fed a starter supplemented with sodium butyrate, sodium monensin and calcium propionate. There was significant reduction in the concentrations of plasma glucose as calves aged. The inclusion of sodium butyrate, calcium propionate or sodium monensin as additives in starter feeds resulted in equal animal performance, before and after weaning, suggesting that sodium monensin may be replaced by organic acid salts.     

Effect of pre-weaning concentrate supplementation on peripheral distribution of leukocytes, functional activity of neutrophils, acute phase protein and behavioural responses of abruptly weaned and housed beef calves

Background  

The effect of pre-weaning concentrate supplementation on peripheral distribution of leukocytes, functional activity of neutrophils, acute phase protein response, metabolic and behavioural response, and performance of abruptly weaned and housed beef calves was investigated. Calves were grazed with their dams until the end of the grazing season when they were weaned and housed (day (d) 0) in a concrete slatted floor shed, and offered grass silage ad libitum plus supplementary concentrates. Twenty-six days prior to weaning and housing, 20 singled suckled, pure-bred Simmental male (non-castrated), (n = 10, m) and female (n = 10, f) calves were assigned to one of two treatments (i) concentrate supplement (CS: n = 10 (5 m and 5 f), mean age (s.d.) 201 (12.8) d, mean weight (s.d.) 258 (20.2) kg) or (ii) no concentrate supplement (controls) (NCS: n = 10, (5 m and 5 f), mean age (s.d.) 201 (13.4) d, mean weight (s.d.) 257 (19.6) kg) pre-weaning.     

紫苏、白苏的抑菌实验

用不同溶剂浸泡或处理紫苏后,进行抑菌实验,结果表明：１０％以上浓度的紫苏水浸液,１２．５％水煎液和乙醇提取液对白色念球菌、新型隐球菌以及红色毛癣菌、石膏样小孢子癣菌、絮状表皮癣菌有较好的抑菌效果。紫苏、皱紫共、白苏对真菌均有抑菌作用,但皱紫苏对绿脓杆菌、白苏对克柔氏念球菌、白色念球菌以及绿脓杆菌效果更为明显。     

Monoclonal antibodies that react with Leishmania (Viannia) naiffi

Monoclonal antibodies were raised against Leishmania (Viannia) naiffi, which recently has been characterized as a new species. BALB/c mice were immunized with membrane-enriched fractions of a mixture of L. (V.) naiffi isolates. Subsequent fusion of immunized splenocytes with NS-1 myeloma cells resulted in the production of 5 Mabs (N1-N5). Screening by ELISA and indirect immunofluorescence against an extensive cross-panel of Leishmania strains revealed that N3 was species-specific and could thus be used to identify L. (V.) naiffi. N2 and N5 reacted only with strains of L. (V.) naiffi and Leishmania (Viannia) braziliensis, and therefore could be used in conjunction with N3 to identify L. (V.) braziliensis parasites. These species-specific Mabs will therefore be useful additions to the panel of antibodies already available for the identification of Leishmania species. N1 and N4 were found to recognize a small, glycosylated molecule present on all L. (V.) naiffi and L. (V.) braziliensis isolates that is related to the GIPL family of membrane glycophospholipids previously described for Leishmania (Leishmania) major.     

Influence of prenatal photoperiod on postnatal prolactin secretion in red deer (Cervus elaphus).

Plasma prolactin concentrations were higher (P < 0.001) in newborn red deer calves whose mothers had been maintained for the last 14 weeks of gestation in long days (18 h light) (group L, n = 9) than in those whose mothers had been kept over the same period in short days (6 h light) (group S, n = 5). After transfer of all hinds and suckled calves on the day of birth to constant intermediate daylength (12 h light), prolactin concentrations decreased exponentially (P < 0.001) in group L calves, but not in group S, during the first 21 days. Thereafter, prolactin fell to a nadir in group L calves and rose to peak values in group S calves at 8-12 weeks post partum (P = 0.003), before converging again by 14 weeks. The pattern of prolactin secretion over the first 14 weeks of life was therefore significantly affected by prenatal photoperiod. Plasma prolactin concentrations in the adult hinds were higher (P < 0.001) in group L than group S at 4-10 weeks before parturition; they were similarly high around parturition and fell thereafter to baseline values after 7 weeks. These results provide evidence that deer fetuses respond to photoperiodic information, thereby acquiring a photoperiodic history in utero that influences postnatal responses to photoperiod.     

Muscle fibre growth in undernourished reindeer calves (Rangifer tarandus tarandus L.) during winter.

To study whether moderate under-nutrition causes muscle wasting, reindeer (Rangifer tarandus tarandus L.) calves were fed either pelleted reindeer feed ad libitum (n=8) or restricted amounts of lichens (n=8). The restricted amount was 60% of ad libitum intake of lichens, and the feeding period was 6 weeks preceded by a 2-week adjustment period. Biopsy samples from the middle gluteal muscle (M. gluteus medius) for the analysis of fibre composition and area, as well as for the activity of cathepsin B were taken before the restriction period in November and January, and after the restriction period in April. In all calves the muscle fibre composition remained unchanged during the winter. In the lichen group, the fibre size also remained unchanged, whereas in control calves the cross sectional area of type I and type IIA fibres increased significantly from November to April. Cathepsin B activity decreased in all calves from November to January and remained at that low level for the rest of the study period, which suggests an attenuated rate of protein degradation. These results can be taken as an indication that moderate under-nutrition causes no muscle wasting in reindeer calves, and the decreased availability of nitrogen is partially compensated for by adaptive decrease in protein degradation. Interestingly the adaptive changes in protein metabolism are equally well seen in the well-fed controls as in the undernourished lichen-fed reindeer.     

Sites of attachment and density assessment inAmblyomma americanum (Acari: Ixodidae) on nursing beef calves

Primary attachment sites of male, female, and nymphalAmblyomma americanum (L.) on nursing beef calves were the axillary, inguinal and perianal areas of the body. About 50% of all larvae fed on the ears.A density assessment method which uses the number ofA. americanum on 5 body areas to predict the total number of ticks (tick burden) on the left side of a calf is presented. Estimates of tick burden for male, female, nymphal and larvalA. americanum each require examination of the axillary, inguinal, and perianal body areas. In addition, to estimate larval and maleA. americanum, the neck, dewlap and brisket require examination as do the ears for estimates of nymphs and larvae. Mean tick burden in a herd of calves can be estimated by an examination of from 14 to 100% of all calves depending on the level of precision required for the estimate.     

Conception dates in relation to age and condition in two populations of Red deer in Scotland

The conception dates of wild Red deer ( Cervus elaphus L .) in two parts of Northern Scotland (the Isle of Rhum in the Inner Hebrides, and Glen Feshie in the Central Highlands) were estimated from foetus weights and from the known birth dates of calves. In both localities, the conceptions were spread over periods of about 100 days from late September to late December with a peak in October. The median conception date was seven to ten days earlier on Rhum than at Glen Feshie.
The conception data from shot hinds showed distinct patterns in relation to age, whether or not the hinds had current year's calves, and to body condition. Body condition may be the most important "secondary factor" influencing the time of conception; hinds in poor condition tended to conceive later than those in good condition. Body condition could also account for year to year fluctuations in the time of breeding; hinds tended to breed earlier in years when they were in better condition.     

Effects of treatment with LH or FSH from 4 to 8 weeks of age on the attainment of puberty in bull calves

A transient increase in gonadotropin secretion between 6 and 20 weeks of age is critical for the onset of puberty in bull calves. To try and hasten the onset of puberty, bull calves were treated (s.c.) with 3 mg of bLH (n = 6) or 4 mg of bFSH (n = 6) once every 2 days, from 4 to 8 weeks after birth; control calves received saline (n = 6). At 4 and 8 weeks of age, mean LH concentrations were higher (P < 0.05) in bLH-treated (2.3 +/- 0.04 ng/ml and 1.20 +/- 0.04 ng/ml) as compared to control calves (0.50 +/- 0.1 ng/ml and 0.70 +/- 0.10 ng/ml). Mean serum FSH concentrations at 4 and 8 weeks of age, were higher (P < 0.05) in bFSH-treated (1.60 +/- 0.20 ng/ml and 1.10 +/- 0.2 ng/ml) as compared to control calves (0.38 +/- 0.07 ng/ml and 0.35 +/- 0.07 ng/ml). The age at which scrotal circumference (SC) first reached > or = 28 cm, occurred earlier (P < 0.05) in bFSH-treated calves as compared to saline-treated calves (39.3 +/- 1.3 and 44.8 +/- 1.3 weeks of age, respectively). Based on testicular histology at 56 weeks of age, treatment with bFSH resulted in greater (P < 0.05) numbers of Sertoli cells (5 +/- 0.2, 6 +/- 0.3 and 5 +/- 0.3 in bLH-, bFSH- and saline-treated calves, respectively); elongated spermatids (42 +/- 2, 57 +/- 8 and 38 +/- 5 in bLH-, bFSH- and saline-treated calves, respectively) and spermatocytes (31 +/- 3, 38 +/- 3 and 29 +/- 2 in bLH-, bFSH- and saline-treated calves, respectively) per seminiferous tubule. We concluded that treatment of bull calves with bFSH from 4 to 8 weeks of age increased testicular growth (SC); hastened onset of puberty (SC > or = 28 cm); and enhanced spermatogenesis.     

Calcium propionate supplementation improves development of rumen epithelium in calves via stimulating G protein-coupled receptors

In the present study, calcium propionate (CaP) was used as feed additive in the diet of calves to investigate their effects on rumen fermentation and the development of rumen epithelium in calves. To elucidate the mechanism in which CaP improves development of calf rumen epithelium via stimulating the messenger RNA (mRNA) expression of G protein-coupled receptors, a total of 54 male Jersey calves (age=7±1 days, BW=23.1±1.2 kg) were randomly divided into three treatment groups: control without CaP supplementation (Con), 5% CaP supplementation (5% CaP) and 10% CaP supplementation (10% CaP). The experiment lasted 160 days and was divided into three feeding stages: Stage 1 (days 0 to 30), Stage 2 (days 31 to 90) and Stage 3 (days 91 to 160). Calcium propionate supplementation percentages were calculated on a dry matter basis. In total, six calves from each group were randomly selected and slaughtered on days 30, 90 and 160 at the conclusion of each experimental feeding stage. Rumen fermentation was improved with increasing concentration of CaP supplementation in calves through the first 30 days (Stage 1). No effects of CaP supplementation were observed on rumen fermentation in calves during Stage 2 (days 31 to 90). Supplementation with 5% CaP increased propionate concentration, but not acetate and butyrate in calves during Stage 3 (days 91 to 160). The rumen papillae length of calves in the 5% CaP supplementation group was greater than that of Con groups in calves after 160 days feeding. The mRNA expression of G protein-coupled receptor 41 (GPR41) and GPR43 supplemented with 5% CaP were greater than the control group and 10% CaP group in feeding 160 days calves. 5% CaP supplementation increased the mRNA expression of cyclin D1, whereas did not increase the mRNA expression of cyclin-dependent kinase 4 compared with the control group in feeding 160-day calves. These results indicate that propionate may act as a signaling molecule to improve rumen epithelium development through stimulating mRNA expression of GPR41 and GPR43.     

The diurnal habitat used by red deer (Cervus elaphus L.) in the Haute Ardenne

We describe diurnal habitat used by red deer (Cervus elaphus L.) in two representative forests of Haute Ardenne. We captured 17 calves and 13 adults and fitted them with VHF transmitters (ear tags or collars). Each animal was radio-tracked at least once per week during the daylight hours and relocated by triangulation. To determine habitat use, we used compositional analysis. We defined use for each animal as the proportion of relocations in each vegetation association. Each relocation was weighed according to its accuracy (i.e., based on the confidence ellipse computation). We defined availability as the proportion in the area of each vegetation association within its home range (i.e., minimum convex polygon). Red deer calves preferred edges in open areas (e.g., clear-cuts) during their first 3 months of life. Adults used open coniferous [e.g., natural regeneration of spruce (Picea abies)] stands and edges between coniferous stands and other vegetation associations. Closed coniferous stands were preferred during winter and deer usually used the edges of habitat patches rather than the core areas, except in winter for coniferous stands. The deciduous stands [e.g., old growth stands of beech (Fagus sylvatica)] were usually avoided, except in winter when the edges of deciduous stands were used. The availability of coniferous stands and edges partly determined the size of the diurnal home ranges.     

Monitoring the bovine fetus during stage II of parturition using pulse oximetry

Measurement of oxygen saturation using pulse oximetry is an established method of continuous monitoring of the well-being of the human fetus during parturition. In veterinary medicine, pulse oximetry has been used almost exclusively in intensive care and anesthesiology. The goal of the present study was to investigate the physiological changes in oxygen saturation of the bovine fetus during stage II of parturition and to determine whether the findings can be used to predict postnatal acidosis. The correlation between the oxygen saturation (SpO(2)) measured via pulse oximetry and the oxygen saturation (SaO(2)) of arterial blood measured via blood gas analysis was determined in 23 newborn calves. In addition, the oxygen saturation was monitored continuously via pulse oximetry (FSpO(2)) in 33 bovine fetuses during stage II of parturition. Correlations between the FSpO(2) values during the last 30 and 5min of stage II of parturition and the postpartum values for pH, partial pressures of oxygen and carbon dioxide, bicarbonate concentration, BE, SaO(2) and lactate concentration in arterial blood were determined. There was a high correlation between SpO(2) and SaO(2) postpartum (r=0.923). The FSpO(2) values correlated moderately with the pH and BE and weakly with the lactate concentration postpartum; calves with a pH<7.2, a BE<-3mM/L or a lactate concentration of >5.4mM/L had significantly lower FSpO(2) values than non-acidotic calves. FSpO(2) values <30% for a period of at least 2min had the highest predictive value for a calf born with a pH<7.2. Pulse oximetry is a novel method of monitoring the bovine fetus during parturition; however, technical modifications are required to improve its usefulness.     

Host range nodulation and adaptation in frenchbean rhizobia

The host range nodulation efficiency of four genetically marked frenchbean rhizobial strains (HURR-3, Raj-2, Raj-5 and Raj-6) was studied with five legume hosts namely, frenchbean (Phageolus vulgaris L.), pigeonpea [Cajanus cajan (L.) Millsp.], mungbean [Vigna radiata (L.) Wilezek.], urdbean [Vigna mungo (L.) Hepper.] and soybean [Glycine max (L.) Merril.]. Except soybean and pigeonpea, all other legume hosts were nodulated by two or more frenchbean rhizobial strains tested. Rhizobia were isolated from nodules produced by strains, HURR-3 and Raj-5, on main (frenchbean) and different (mungbean and urdbean) hosts. There was marked improvement in host range nodulation and nitrogen fixation efficiency of rhizobial strains, HURR-3 and Raj-5. after their isolation from chance nodules on different hosts. This is clearly evident from the ability of such isolates to form nodules on pigeonpea besides mungbean and urdbean, and higher nodulation in all the above three different hosts. The phage-susceptibility pattern and intrinsic antibiotic resistance (used as markers) of the two strains did not change after their passage through different hosts. The results indicate that frenchbean rhizobia had undergone some modification in symbiotic behaviour to adapt to wide host range during their passage through different (alternate?) hosts.     

Effect of naloxone on the secretion of LH in infantile and prepubertal Holstein bull calves

Administration of naloxone (100 mg i.v.; approximately 1.21 mg/kg body weight0.75) to 10 intact calves (24 weeks of age) caused an acute release of LH that was similar in amplitude and duration to spontaneous discharges of LH that occur at the same age. The naloxone-induced release of LH was abolished in 9/10 calves (intact and castrated) treated with oestradiol-17 beta. To determine the ontogeny of opioid control of secretion of LH, 12 calves were randomly assigned to receive saline or naloxone (1.21 mg/kg body weight0.75, i.v.) at 3, 5, 7, 9, 11, 13, 17 and 21 weeks of age. At each age, blood was collected at 10-min intervals for 4 h and saline or naloxone was administered (i.v.) after collection of the 120-min sample. Before administration of naloxone, plasma LH values increased with age (P less than 0.01) but did not differ between the control and naloxone groups (age x treatment, P greater than 0.05). Administration of naloxone caused concentrations of plasma LH to increase at 3, 11, 13, 17 and 21 weeks of age (treatment x time, P less than 0.001). Concentrations of LH (saline vs naloxone, ng/ml) reached a maximum within 20 min after treatment at Weeks 3 (0.3 vs 1.2), 11 (0.6 vs 2.6), 13 (0.6 vs 3.7), 17 (1.1 vs 2.6), and within 40 min after treatment at Week 21 (1.0 vs 3.5).(ABSTRACT TRUNCATED AT 250 WORDS)     

Survival of Oocysts of Eimeria alabamensis on Pastures under Different Climatic Conditions in Sweden

The extent to which oocysts of the coccidian parasite Eimeria alabamensis can survive the winter and cause clinical coccidiosis in different parts of Sweden was investigated. Fecal samples were collected between May and July 1993 from calves on 59 farms where calves had grazed the same pasture for at least 5 consecutive years. The farms were situated in 9 regions of Sweden with different climatic conditions in the winter. On each farm, 5 samples of feces were collected from the floor of the calf-house before the calves were turned out in the spring, and again from the pasture on days 4 or 5, 8 or 9 and 10 or 11 after they were turned out. Overwintering of oocysts of E. alabamensis was considered to have occurred if an increase in the excretion rate of oocysts of this species could be demonstrated 8 to 11 days after calves had been turned out to pastures that had not been grazed since the previous autumn. Oocysts were shown to have overwintered on 27 farms, representing all 9 regions. Samples from 20 (34%) of the farms representing all the climatic regions contained more than 850000 oocysts per g of feces. This was comparable with the numbers found in animals with clinical coccidiosis due to E. alabamensis. Delaying turnout until the beginning of July did not affect the infection rate of the calves. However, calves which were turned out to pastures that had been grazed by older cattle or horses, either earlier in the spring or in previous years, excreted significantly fewer oocysts than calves which were turned out to pastures that had been grazed only by calves. A questionnaire answered by 321 dairy farmers revealed that of the 298 farmers who turned their first-season grazing cattle out to traditional pastures, 179 (60%) had used the same pasture for at least 5 years. These 179 farmers had experienced a significantly higher incidence of diarrhoea in their calves during the first 2 weeks at pasture than those farmers who had used different pastures.     

Bull selection and use in northern Australia. 4. Calf output and predictors of fertility of bulls in multiple-sire herds

On 10 northern Australian properties, the number of calves sired (calf output) by individual bulls in multiple-sire matings was measured by DNA typing for paternity. There were 235 bulls (92 Santa Gertrudis, 25 5/8 Brahman and 119 Brahman) from 37 multiple-sire mating groups. Number of bulls in groups ranged from 2 to 25 and ages of bulls ranged from 2 to 5 years. Mating periods were for 3-12 months and bull mating percentages were 2.5-6%. In all, there were 4251 calves tested and the resolution of paternity ranged from 92.5 to 100% and averaged 97.7% across all sites. This included 9.9% of calves with no potential sires in any of the mating groups. Of the 235 bulls mated, 58% sired 10% or less calves in each of their respective mating groups with 6% not siring any calves. In contrast, 14% sired over 30% of the calves in each of the respective mating groups. When bulls were mated in groups of 8-24, the maximum percent of calves sired by individual bulls was 26+/-7% (mean+/-S.D.) with a range 11-36%. However, when bulls were mated in groups of 2-7, the maximum percent of calves sired by individual bulls was 59+/-19% with a range 24-94%. Calf output of bulls was moderately repeatable across years at four of five sites. Multiple regression models relating pre-mating measures of physical, seminal and behavioural traits to calf output were developed for the three breed groups. In all, only 138 of the 235 bulls were included in the models (40 Santa Gertrudis, 24 5/8 Brahman and 74 Brahman). Sheath and testicular traits, such as scrotal circumference and testicular tone, were generally not related to calf output, the exceptions being sheath depth in Brahman bulls which was negatively related (P<0.05) and scrotal circumference in 5/8 Brahmans which was positively related (P=0.08) to calf output. Dominance was only included in the 5/8 Brahman model but there was no significant relationship between dominance hierarchy and calf output. Semen motility was only related (P<0.05) to calf output in 5/8 Brahmans. However, measures of semen quality based on spermatozoa morphology were important contributors to calf output in the Santa Gertrudis and Brahman models where percent normal spermatozoa was positively related (P<0.01) to calf output. In Santa Gertrudis and Brahman bulls, measures of sexual behaviour in the serving capacity test were related to calf output. In Santa Gertrudis, these were for the number of displays of sexual interest (P<0.05), and mounts (P<0.01), but not number of serves, whilst in Brahman bulls, libido score was positively related to calf output (P<0.05). The models only explained 35-57% of the variation in calf output.     

Detection of Cryptosporidium circulating antigens in human and calf sera.

Cryptosporidium-specific circulating antigens were detected in sera of experimentally infected calves and AIDS patients by an enzyme-linked immunosorbent assay. Antigenemia was detectable from 2 to a minimum of 22 days post-infection (d.p.i.) in calves whose feces were parasitologically positive from 2-10 d.p.i. Antigenemia was detected in AIDS patients showing no a sero-conversion to immunoglobulin (Ig) M or to IgG. The detection of circulating antigens in humans allows early diagnosis of cryptosporidiosis, even in immunosuppressed patients.     

Economic effects of horn fly (Diptera: Muscidae) populations on beef cattle exposed to three pesticide treatment regimes.

Horn flies could not be maintained below 50 per animal with sprays or dusts during a 21-wk study. However, weights of cows and calves and condition scores of cows were not influenced by suppression of Haematobia irritans (L.) populations. Results show that cattle in northwest Florida can tolerate average populations of greater than or equal to 200 flies for 70 d with no adverse economic effects. Spray treatments providing the best fly control were Lintox-D and Ra-Vap. The most economical products for use were Del-Tox, Lintox-D, and Ra-Vap.