Variation in meat quality characteristics between Sanga (Bos taurus africanus) and Sanga-derived cattle breeds and between Sanga and Brahman (Bos indicus)

Cattle breeds indigenous to Africa (Sanga) compare favourably to Bos indicus breeds with regard to adaptation to harsh environments. This study compared the meat quality of three Sanga breeds (Nguni, Tuli and Drakensberger), a Sanga-related breed (Bonsmara) and a B. indicus breed (Brahman) and supported these results with biochemical and histological measurements on the M. longissimus lumborum. Twelve young grain-fed steers of each breed were slaughtered and carcasses were electrically stimulated. All Sanga (and related) breeds, with the exception of the Tuli, had lower Warner-Bratzler shear force (SF) values at 2 and 21 days post mortem compared with the BR (P < 0.05). Measurements related to the calcium-dependent protease system and myofibrillar fragmentation explained the bulk of the variation among breeds, whereas variation in fibre type, sarcomere length and connective tissue properties gave less convincing support. With the exception of the Tuli, Sanga and Sanga-related breeds produced more tender (according to SF) meat than BR, mainly due to favourable calpain-to-calpastatin ratios. Small differences in colour, drip loss and cooking properties were found among breeds (P < 0.05).     

The effects of the bont tick, Amblyomma hebraeum, on milk production of Sanga and Sanga x Brahman cattle

Abstract. The effects of adults of the bont tick, Amblyomma hebraeum on the milk production of Sanga and Sanga x zebu (Brahman) cattle were measured over a period of 11 weeks in the lowveld of Zimbabwe in the summer of 1986. Four groups of lactating cows, consisting of two breeds, each divided into a high and low tick treatment, were exposed to very low or high challenges of ticks and their milk production measured by weighing their calves before and after suckling. The liveweight gains (LWG) of the calves were also measured.
Tick burdens on the infested groups averaged around fourteen engorging females of A.hebraeum per day, which amounted to infestations of about 150 adult ticks. That is greater than most observed field infestations. This caused no significant reduction in milk yield or calf growth over the whole period, provided the teats of the dams had not been damaged by ticks. Mismothering occurred when teats were damaged. No breed differences were observed so all data was pooled for further analysis. Average calf LWGs of the high tick groups were reduced by 2.2kg (P < 0.01) during one 4-week period but overall the 3.9 kg difference in LWG of the tick treatment groups was not quite significant (P < 0.10). Although there was a poor relationship between tick numbers and reduced milk yield or calf LWG, the effects were always in the direction expected. The effects averaged 6 ± lOg reduction of milk and 2.6 ± 1.8g loss of LWG of calves for every female tick that engorged. It was concluded that milk production is not an important consideration when estimating the losses in production caused by A.hebraeum on Brahman x Sanga or Sanga breeds of cattle. Losses due to teat or udder damage could be much more important and need to be quantified.     

Genetic Diversity and Relationship of Yunnan Native Cattle Breeds and Introduced Beef Cattle Breeds

In this study, random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic diversity and relationship in 134 samples belonging to two native cattle breeds from the Yunnan province of China (DeHong cattle and DiQing cattle) and four introduced beef cattle breeds (Brahman, Simmental, MurryGrey, and ShortHorn). Ten primers were used, and a total of 84 bands were scored, of which 63 bands (75.0%) were polymorphic. The genetic distance matrix was obtained by proportions of shared fragment. The results indicate that the Yunnnan DeHong cattle breed is closely related to the Brahman (Bos indicus), and the Yunnan DiQing cattle breed is closely related to the Simmental, ShortHorn, and MurryGrey (Bos taurus) breeds. Our results imply that Bos indicus and Bos taurus were the two main origins of Yunnan native cattle. The results also provide the basic genetic materials for conservation of cattle resources and crossbreeding of beef cattle breeds in South China.     

Growth and reproductive development from weaning through 20 months of age among breeds of bulls in subtropical Florida

To determine the effect of breed on growth and reproductive development, weaned bulls in each of 2 yr were managed as a single group for approximately a year. In Year 1, the study group consisted of 24 Angus, 24 Brahman, 20 Hereford and 14 Senepol bulls, while in Year 2, it contained 25 Angus, 17 Brahman. 13 Romosinuano and 9 Nellore x Brahman bulls. Body and testicular growth measurements were recorded at 6-wk intervals. At approximately 1 yr of age and quarterly thereafter (4 periods), bulls were evaluated for libido, pubertal status, and GnRH-induced LH and testosterone secretion. Significant breed-by-age interactions occurred for most growth measurements. Brahman bulls (Bos indicus ) were (P < 0.05) older and heavier at puberty than Angus, Hereford, Senepol and Romosinuano bulls (Bos taurus ). Libido scores were lowest for Brahman and Nell ore x Brahman bulls (Bos indicus ). highest for Angus and Hereford bulls (temperate Bos taurus breeds) and intermediate for Senepol and Romosinuano bulls (tropical Bos taurus breeds; P < 0.05). Differences were not consistent among breeds or between years for GnRH-induced LH secretion. In both years, basal testosterone concentrations and areas under the GnRH-induced testosterone curve were higher (P < 0.05) for Angus and Hereford bulls (temperate breeds) than for Brahman, Senepol, Romosinuano and Nellore x Brahman bulls (tropical breeds). In conclusion, reproductive development of Senepol and Romosinuano bulls (tropical Bos taurus breeds) was more similar to Angus and Hereford bulls (temperate Bos taurus breeds) than to Brahman and Nellore x Brahman bulls (Bos indicus ).     

Resistance to Boophilus microplus (Canestrini) in genetically different types of calves in early life.

Tick resistance and blood composition were studied in British (1/2 Shorthorn x 1/2 Hereford) and zebu (1/2 Brahman x 1/2 British) calves from birth to 33 days of age in a tropical grazing area in which B. microplus is endemic. Calves of the 2 breeds were either naturally infested or were, in addition, artificially infested with 5,000 larvae at 2 and 9 days of age. Total numbers of mature female ticks carried from either type of infestation were significantly lower (P less than 0.01) on zebu than on British calves. In the artificially infested calves of both breeds, the total number of ticks maturing between 20 to 26 days of age was significantly higher (P less than 0.01) than the number maturing between 27 to 33 days of age emphasizing that a major component of resistance is acquired. However, in the naturally infested calves, breed differences in the numbers of ticks maturing during these 2 periods suggested the presence of genetic differences in innate resistance. Within breeds, total tick numbers carried during the study were negatively correlated with calf weight gain and with the concentrations of serum albumin, total protein, and cholesterol.     

Effect of alfaprostol, lasalocid, and once-daily suckling on postpartum interval in Brahman and Brahman crossbred cattle

Brahman cows (n = 49) and primiparous heifers (n = 11), Brahman x Hereford primiparous F1 heifers (n = 86) and Simmental x Brahman primiparous F1 heifers (n = 13) were randomly allotted by breed, age and date of calving to one of eight treatment groups: 1) control; 2) once-daily suckling; 3) lasalocid (200 mg/hd/d); 4) alfaprostol (5 mg intermuscular injections on Days 21 and 32 post partum); 5) lasalocid + once-daily suckling; 6) alfaprostol + once daily suckling; 7) alfaprostol + lasalocid; 8) alfaprostol + lasalocid + once daily suckling. All animals received 2.3 kg/hd/d of a concentrate (6 corn : 1 cottonseed meal) and lasalocid was mixed and fed in the concentrate. Body weights and condition scores were taken on Day 1 post partum and every 28 d thereafter. All animals were maintained with sterile marker bulls with Brahman and Simmental x Brahman cattle artificially inseminated at first estrus. Blood samples were collected at weekly intervals starting on Day 21 post partum until estrus and at nine to twelve days post estrus when the ovaries were palpated for corpora lutea. After the first postpartum estrus with a corpora lutea, cows were placed with fertile bulls. Mean serum progesterone concentrations were below 0.5 ng/ml prior to treatment. Calf weight gains to 90 d were not affected by age (P > 0.10) but were lower in the once-daily suckling group (P < 0.05). Treatment did not affect cow weight or condition score (P > 0.10). Cows had a shorter postpartum interval (P < 0.0001) than heifers. Once-daily suckling shortened postpartum interval (P < 0.0001) and positively influenced the cumulative frequency of return to estrus by 40 d post partum (P < 0.02). Alfaprostol did not affect postpartum interval (P > 0.10) but did increase the cumulative frequency of return to estrus by 90 d post partum (P < 0.03). Lasalocid did not affect postpartum interval or cumulative frequency of return to estrus (P > 0.10). Both once-daily suckling and alfaprostol were effective in increasing the numbers of animals inseminated by 90 d post partum. The once-daily suckling + alfaprostol treatment resulted in the shortest postpartum interval.     

Breed and other effects on reproductive traits and breeding soundness categorization in young beef bulls in Florida

Yearling, grass-fed, beef bulls at the USDA Subtropical Agricultural Research Station, Brooksville, Florida, were assessed for physical and semen traits in January, April, July and October of 1991 (Trial 1) and 1992 (Trial 2). Bulls were given a breeding soundness evaluation (BSE) using revised semen and scrotal circumference (SC) criteria. In Trial 1, the bulls consisted of Angus (n = 15), Brahman (n = 14), Hereford (n = 15) and Senepol (n = 14). In Trial 2, the breeds were Angus (n = 15), Brahman (n = 16), Romosinuano (n = 13) and Nellore x Brahman (n = 9). Trial bulls generally showed delayed growth compared with grain-fed bulls in temperate environments. Breed influenced semen traits (percentage sperm motility, normal spermatozoa and those with primary abnormalities) in both trials. Temperate Bos taurus breeds (Angus, Hereford) were generally superior to Bos indicus breeds (Brahman, Nellore x Brahman). Tropically-adapted Bos taurus breeds (Senepol, Romosinuano) were intermediate for those traits tested. In general, tropically-adapted Bos taurus breeds were more similar in reproductive development to temperate Bos taurus than to Bos indicus breeds. Breed by test period interactions occurred and were mainly influenced by delayed sexual maturity of Bos indicus bulls. Qualitative semen traits increased with bull age, particularly from 12 to 18 mo. Scrotal circumference development was slower in the Bos indicus breeds. Bulls of satisfactory BSE status at 18.1 to 22 mo of age were 73.9% in Trial 1 and 58.5% in Trial 2. Brahman bulls had the least satisfactory BSE scores in both years (Trial 1, 44.4%; Trial 2, 22.2%). Most bulls failed to achieve satisfactory BSE status due to a small SC relative to age (Trial 1, 66%; Trial 2, 72%). The most efficacious use of the BSE was > or = 15 mo in Bos taurus bulls and > 18 mo for Bos indicus bulls. Although the BSE has proven to be useful for the assessment of young, pasture-raised bulls in semi-tropical environments, use of SC thresholds linked more with growth traits than with calendar age would improve comparisons of relative reproductive development in such bulls, particularly those of Bos indicus derivation.     

Distribution and Seasonal Abundance of Trematode Parasites (Trematoda: Allocreadiidae: <Emphasis Type="Italic">Crepidostomum</Emphasis> spp.) in burrowing-mayfly nymphs (Ephemeroptera: Ephemeridae: <Emphasis Type="Italic">Hexagenia</Emphasis> spp.) from Connecting Rivers of the Laurentian Great Lakes

Burrowing-mayfly nymphs such as Hexagenia spp. have been used extensively in North America and Europe as a biomonitoring tool to indicate mesotrophic water quality, yet infestation by associated parasites has not been well documented. We performed laboratory analysis of archived samples of Hexagenia spp. nymphs collected in 1985 and 1986 to provide base-line data on the distribution (1985) and seasonal infestation (1986) of the trematode parasite Crepidostomum spp. in Hexagenia spp. nymphs in connecting rivers between Lakes Superior and Erie of the Laurentian Great Lakes. In May and June 1985, frequency of occurrence of metacercariae was widely distributed throughout the connecting rivers (63% of 203 stations with nymphs), except in areas where nymph densities were relatively low (i.e.,≤69 nymphs/m²). Distribution was probably underestimated in the present study because of low probability (mean = 31%, range = 0–57%) of detecting infestation in a small number of collected nymphs ( ≤10) at nymph densities ≤69/m². In 1986, seasonal infestation between April and October occurred in 3.3% (627) of 18696 nymphs. Overall prevalence, mean intensity, and mean abundance of parasites at one station in the St. Marys River indicate parasite transmission occurred between June and September. This period of transmission is dependent on the life-cycle of the parasite. In addition, the life-cycle of Hexagenia spp. determines which annual cohort of nymphs is infested and therefore, the duration of infestation. Although, no impacts of infestation on Hexagenia spp. nymphs were observed in the present study, infestation intensities were high enough (≥25 metacercariae per nymph) at one station in the St. Marys River to potentially cause tissue damage in a high proportion (53%) of infested nymphs.     

Effect of herbivory by Teleonemia scrupulosa on the performance of Longitarsus bethae on their shared host, Lantana camara

Herbivory by insects may change the characteristics of nutrients and secondary plant chemicals of the foliage, thereby altering the acceptability and suitability of the plant for oviposition, feeding and development for subsequent herbivores. In the current study, the effect of herbivory by the sap-sucking lace bug, Teleonemia scrupulosa Stäl (Heteroptera: Tingidae), on the suitability of Lantana camara L. (Verbenaceae) for the root-feeding flea beetle, Longitarsus bethae Savini & Escalona (Chrysomelidae: Alticinae), was investigated under laboratory conditions. Preference of adult L. bethae was not influenced by the intensity of feeding damage caused by T. scrupulosa adults. However, high densities of T. scrupulosa nymphs and their feeding damage caused L. bethae adults to emigrate and colonize less infested or uninfested plants. Oviposition by L. bethae was significantly reduced at high densities of T. scrupulosa nymphs. While low infestation of T. scrupulosa had no effect the survival of L. bethae, moderate and high infestations caused significant reduction in percentage survival of L. bethae. The number of T. scrupulosa nymphs was negatively correlated with the percentage survival of L. bethae. Neither the duration of development nor the body size of L. bethae was influenced by the intensity of T. scrupulosa infestation. Overall, undamaged or slightly damaged plants that allowed better survival of L. bethae were often chosen as oviposition sites in preference to those that were highly infested, and on which survival was poor. Although the present study indicates the likelihood of inter-specific competition between L. bethae larvae and T. scrupulosa, this is likely to be mitigated by female flea beetles choosing to oviposit on less infested or uninfested plants in the field.     

Development and feeding of <Emphasis Type="Italic">Tetraphleps galchanoides</Emphasis>, a predator of the hemlock woolly adelgid

Tetraphleps galchanoides Ghauri (Hemiptera: Anthocoridae) nymphs were collected from hemlock woolly adelgid (HWA) Adelges tsugae Annand (Hemiptera: Adelgidae) infested Tsuga sp. in Baoxing, Sichuan, China. First and second stage nymphs collected from foliage shipped from China; were reared to adults and tested for feeding rates and host preferences. They were reared at 5, 8, 12, and 15 ± 1 °C from November to December, January to March, April, and May to June, respectively, in the quarantine laboratory at Virginia Polytechnic Institute and State University. At 8 °C, development time was 15, 20, and 40 days for the N-III, IV, and V nymphal stages, respectively. Adult males lived 83 days with a range of 21–147 days. A single adult female lived for 21 days. At 5 °C, second stage T. galchanoides nymphs consumed 0.8 HWA nymphs per day, and 2.0 HWA nymphs per day at the N-V stage. At 8 °C, consumption of HWA nymphs ranged from 1.3 to 3.4 nymphs per day for the N-III to N-V stages, respectively. Adult T. galchanoides consumed more HWA eggs than HWA adults, pine bark adelgid (PBA) Pineus strobi (Hartig) (Hemiptera: Adelgidae) adults, and eggs in no-choice tests. In choice tests with HWA eggs and PBA eggs, more HWA eggs were eaten. Adult and nymph body measurements are presented for determination of nymphal instars.     

Ecology and impact of Allorhogas sp. (Hymenoptera: Braconidae) and Apion sp. (Coleoptera: Curculionoidea) on fruits of Miconia calvescens DC (Melastomataceae) in Brazil

Two fruit-feeding insects, a gall wasp, Allorhogas sp. (Hymenoptera: Braconidae), and a beetle, Apion sp. (Coleoptera: Curculionoidea), were evaluated in their native habitat in Brazil as potential biological control agents of Miconia calvescens DC (Melastomataceae). Allorhogas sp. occurred at two out of three field sites with native populations of M. calvescens, and Apion sp. occurred at all three sites. Both species exhibited aggregated distributions among M. calvescens trees sampled at each site. Allorhogas sp. infested 9.0% and 3.8% of fruits at each of two sites. The number of larvae and pupae of Allorhogas sp. and/or an unidentified parasitoid (Hymenopetera: Eulophidae: Tetrastichinae) ranged from one to five per infested fruit. Fruits infested with Allorhogas sp. were 20% larger and had 79% fewer seeds than healthy fruits. Although adults of Apion sp. were found on leaves and inflorescences of M. calvescens at all three sites, larvae and pupae were found in fruits at only one site, where a maximum of 1.4% of fruits were infested. Fruits infested by Apion sp. contained only one larva or pupa, and were 15% smaller and had 62% fewer seeds than healthy fruits. While a variety of apionids have been used for biological control in the past, this is the first time a braconid wasp has been considered for biological control of a weed.     

Biological control ofAphis pomi [Hom.: Aphididae] ofAphidoletes aphidimyza [Dip.: Cecidomyiidae]; a predator-prey model

Predation ofAphis pomi DeGeer [Hom.: Aphididae] byAphidoletes aphidimyza (Rondani) [Dipt.: Cecidomyiidae] was simulated in Michigan apple orchards using a computer and output validated against field data collected from sleeve cages enclosing aphid infested apple terminals. Lower and upper temperature thresholds for development were 2.9 and 35°C for nymphs ofA. pomi with a mean immature developmental period of 162.3 heat units. Median survivorship of adultA. pomi was 364.3 heat units with an average fecundity of 60.7 offspring per female.A. aphidimyza egg and larval lower threshold and developmental periods were 10.5 and 25.5, 8.1°C and 65.5 heat units, respectively. Larval functional response showed Type II behavior with a y-asymptote of 45 aphids killed per predator. Multiple generation model runs performed under different initial predator: prey densities indicated that current critical predator: prey ratios used in the field for control decisions may underestimate predator efficacy.      

The roles of birds, lizards, and rodents as hosts for the western black-legged tick Ixodes pacificus.

We compared the infestation by ixodid ticks of lizards, rodents, and birds collected simultaneously within areas representing common habitat types in Mendocino County, CA. Lizards were infested only by Ixodes pacificus Cooley and Kohls, birds by I. pacificus and Haemaphysalis leporispalustris (Packard), and rodents by I. pacificus, I. spinipalpis Hadwen and Nuttall, I. woodi Bishopp, Dermacentor occidentalis Marx, and D. variabilis (Say). Infestation by I. pacificus larvae and nymphs of lizards (Sceloporus occidentalis Baird and Girard; Elgaria spp.) and western gray squirrels (Sciurus griseus Ord) (means of 9-35 larvae and 5-6 nymphs per animal) was several times greater than for Neotoma fuscipes Baird woodrats, Peromyscus spp. mice, and birds (means of 0.9-3.5 larvae and 0-0.3 nymphs). Overall, Borrelia-refractory lizards accounted for 84% of I. pacificus larvae and 91% of nymphs collected from animals in dense woodlands. Bird species frequently utilizing tick-questing substrates such as leaf litter (guild I birds) were more heavily infested by I. pacificus subadults (5.2 larvae and 1.0 nymphs per bird) than guild IV birds with minimal perceived contact with tick-questing substrates (0.08 larvae and 0.06 nymphs per bird). Notably, guild I birds carried similar larval loads and at least 20-fold higher nymphal loads relative to woodrats and mice. Only guild IV birds carried as few I. pacificus nymphs as did these rodents. The ratios of larvae to nymphs suggest that, relative to birds, lizards, and squirrels (infested by 1.3-6.0 larvae per nymph), nocturnally active ground-dwelling rodents such as woodrats and mice are underutilized by the nymphal stage (69 to >100 larvae per nymph). The western gray squirrel and guild I-II birds (e.g., the dark-eyed junco, Junco hyemalis [L.]) were the only potential reservoirs of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner (the causative agent of Lyme disease in North America) that were frequently infested with both I. pacificus larvae and nymphs and commonly utilized dense woodland habitats.     

Seasonal occurrence of the bont tick (Amblyomma hebraeum) in the southern lowveld of Zimbabwe

The seasonal occurrence of the bont tickAmblyomma hebraeum was recorded over 2 years on 20 Brahman cattle held in a 240-ha paddock at Mbizi in southeastern Zimbabwe. The cattle were infested with all life cycle stages throughout the study period, and no clearly defined seasonal patterns were recorded. Males remained attached for up to about 6 months, and consequently accumulated on the cattle and outnumbered females considerably. The cattle did not acquire resistance toA. hebraeum and the abundance of the adults increased steadily over the 2 years of sampling. The occurrence of adults and nymphs on hosts appeared to be largely independent of weather, and these stages were active over the entire range of temperature and relative humidity recorded during the study period. It was concluded that unfed adults and nymphs are able to engage in host-seeking irrespective of weather conditions as they do not await hosts on the vegetation but emerge from protected microhabitats in response to specific stimuli from hosts, notably, carbon dioxide and the aggregation-attachment pheromone emitted by attached males. This behavior may explain the reported absence of a consistent pattern of seasonal occurrence ofA. hebraeum at different locations in southeastern Africa.     

Ticks collected on birds in the state of São Paulo,Brazil

The present study reports a collection of Amblyomma spp. ticks in birds from several areas of the state of São Paulo, Brazil. A total of 568 tick specimens (404 larvae, 164 nymphs) were collected from 261 bird specimens. From these ticks, 204 (36%) specimens (94 larvae, 110 nymphs) were reared to the adult stage, being identified as Amblyomma longirostre (94 larvae, 90 nymphs), Amblyomma calcaratum (13 nymphs), Amblyomma nodosum (2 nymphs), and Amblyomma cajennense (5 nymphs). Additionally, 39 larvae reared to the nymphal stage and 8 nymphs that died before reaching the adult stage were identified as A. longirostre according to peculiar characters inherent to the nymphal stage of this species: scutum elongate, and hypostome pointed. The remaining 271 larvae and 46 nymphs were identified as Amblyomma sp. Ticks were collected from 51 species of birds distributed in 22 bird families and 6 orders. The order Passeriformes constituted the vast majority of the records, comprising 253 (97%) out of the 261 infested birds. Subadults of A. longirostre were identified from 35 species of Passeriformes, comprising 11 families (Cardinalidae, Dendrocolaptidae, Fringillidae, Furnariidae, Parulidae, Pipridae, Thamnophilidae, Thraupidae, Turdidae, Tyrannidae, and Vireonidae), and from 1 species of a non-passerine bird, a puffbird (Bucconidae). Subadults of A. calcaratum were identified from 5 species of Passeriformes, comprising 5 families (Cardinalinae, Conopophagidae, Pipridae, Thamnophilidae and Turdidae). Subadults of A. nodosum were identified from 2 species of Passeriformes, comprising two bird families (Thamnophilidae and Pipridae). Subadults of A. cajennense were identified from 2 species of non-passerine birds, belonging to 2 different orders (Ciconiiformes: Threskiornithidae, and Gruiformes: Cariamidae). Birds were usually infested by few ticks (mean infestation of 2.2 ticks per bird; range: 1–16). Currently, 82 bird species are known to be infested by immature stages of A. longirostre, with the vast majority [74 (90%)] being Passeriformes. Our results showed that Passeriformes seems to be primary hosts for subadult stages of A. longirostre, A. calcaratum, and A. nodosum. However, arboreal passerine birds seem to be the most important hosts for A. longirostre whereas ground-feeding passerine birds seem to be the most important for both A. calcaratum and A. nodosum. In contrast, the parasitism of birds by subadults of A. cajennense has been restricted to non-passerine birds.     

Host plant changes produced by the aphid Sipha flava: consequences for aphid feeding behaviour and growth

Induced plant responses may affect the behaviour and growth of the attacking herbivore insect. The aphid Sipha flava (Forbes) produces reddish spots on the infested leaf of its host plant Sorghum halepense (L.). In order to assess the consequences on the aphid of this presumptive induced plant response, we studied the feeding behaviour and growth of S. flava on previously infested and non-infested leaves of S. halepense. Considering that the reddish pigment could play a defensive role, its effect on aphid survival was determined in artificial diets. In addition, changes in the histology of the leaf and the chemical nature of the induced pigment were also studied. Aphids devoted a significantly shorter total time to non-penetration activities in infested than in non-infested leaves. Time before the first phloem ingestion tended to be shorter in infested leaves. The mean relative growth rate of S. flava nymphs was significantly higher on infested than on non-infested leaves. Survival of aphids on diet containing the reddish extract was not significantly different from that on the control diet. Infestation of S. halepense by S. flava produced a reddish coloration in the leaf, which was identified as an anthocyanin by UV-visible spectrometry. Light microscopy showed that only mesophyll cells of previously infested plants presented swelled, dispersed, and heterogeneously stained chloroplasts with a higher accumulation of starch granules, no grana arranged in stacks, and reduction in the amount of inner membranes (thylakoids), relatively to chloroplasts of non-infested leaves. Scanning electron micrographs of leaf surface revealed reduced presence of crystalline epicuticular waxes of epidermal cells in infested leaves as compared to non-infested ones. The main conclusion is that the attack of S. flava to S. halepense leaves induced plant susceptibility where aphid feeding behaviour and growth were both enhanced on previously infested leaves.     

Evidence for the utility of the Bm86 antigen from Boophilus microplus in vaccination against other tick species

The Bm86 antigen, as originally identified in Boophilus microplus, is the basis of commercial tick vaccines against this tick species. The potential for using this antigen or homologues of the antigen in vaccination against other tick species has been assessed. We have conducted vaccine trials in cattle using the B. microplus-derived recombinant Bm86 vaccine (TickGARD) using pairs of vaccinated calves and control calves. These were infested with B. microplus and Boophilus decoloratus larvae simultaneously. For both species, the numbers of engorged female adult ticks, their weight and egg-laying capacity were all reduced, leading to a reduction in reproductive capacity of 74% for B. microplus and 70% for B. decoloratus. Hyalomma anatolicum anatolicum ticks were fed both as immatures as well as adults on vaccinated calves and non-vaccinated controls. There was an overall 50% reduction in the total weight of nymphs engorging on vaccinated calves, and a suggestion of a subsequent effect on feeding adults. For Hyalomma dromedarii there was a 95% reduction in the number of nymphs engorging and a further 55% reduction in weight of those ticks surviving. Rhipicephalus appendiculatus and Amblyomma variegatum ticks were fed simultaneously both as immatures and subsequently as adults. There was no evidence for a significant vaccination effect. Finally, the amino acid sequence of a Bm86 homologue found in H. a. anatolicum unequivocally demonstrated the conservation of this molecule in this species. Our strategy for the development of multivalent anti-tick vaccines is discussed in relation to these findings.     

Interactions between white mealybugs and red spider mites sequentially colonizing coffee plants

Plants under herbivore attack often respond defensively by mounting chemical and physical defences. However, some herbivores can manipulate plant defences to their own benefit by suppressing the expression of induced defences. These herbivore‐induced changes specific to the attacking herbivore can either facilitate or impede the colonization and establishment of a second herbivore. Although recent studies have focused on the effect of multiple herbivory on plant induced response and the third trophic level, few have examined the ecological relevance of multiple herbivores sharing the host. Here, we investigated whether herbivory by the white mealybug Planococcus minor (Maskell) (Hemiptera: Pseudococcidae) or the red spider mite Olygonychus ilicis (McGregor) (Acari: Tetranychidae), two herbivores that peak in coffee plantations during the dry season, may facilitate the colonization and establishment of the other species in coffee plants. Dual‐choice arena tests showed that white mealybugs preferred mite‐infested over uninfested coffee plants as hosts. Fifteen days after the release of 50 first‐instar P. minor nymphs, greater numbers of nymphs and adults were found on mite‐infested than uninfested plants, indicating superior performance on mite‐infested plants. On the other hand, female red spider mites did not show clear preference between uninfested and mealybug‐infested plants and deposited similar numbers of eggs on both treatments. In a no‐choice test, red spider mites performed poorly on mealybug‐infested plants with a smaller number of eggs, nymphs, females and males found in mealybug‐infested plants relative to uninfested plants. Thus, our results indicate that coffee plants are more likely to be infested by the red spider mite before white mealybug, rather than the inverse sequence (i.e. mealybug infestation followed by red spider mites). Our findings are discussed in the context of plant manipulation reported for pseudococcid mealybugs and spider mites.     

The assignment by linkage mapping of four genes from human chromosome 22 to bovine chromosome 5 and 17

Polymerase chain reaction oligonucleotides were designed to amplify bovine specific sequences for four genes that are located on human chromosome 22 (HSA22): crystallin beta A4 (CRY B A4), parvalbumin (PVALB), tissue inhibitor of metalloproteinase 3 (TIMP3) and matrix metalloproteinase 11 (MMP11). Single strand conformation analysis of these bovine gene fragments defined polymorphisms within a population of three large half-sib families of three F1 Charolais x Brahman sires and a composite herd comprising an equal proportion of Africander, Brahman, Hereford and Shorthorn breeds (CSIRO pedigree). The DNA marker genotypes were used to define linkage associations to other DNA markers already placed on the CSIRO linkage map. The genes TIMP3 and PVALB were assigned to BTA5 and CRYbetaA4 and MMP11 to BTA17.     

The effect of feeding immature Karoo paralysis ticksIxodes rubicundus (Acari: Ixodidae) on the metabolic rate of the rock elephant shrew

The effect of feeding immature Karoo paralysis ticks (Ixodes rubicundus) on the resting metabolic rate (RMR) of their principal natural host, the rock elephant shrew (Elephantulus myurus), was investigated under laboratory conditions. The elephant shrews were artificially infested with numbers of ticks simulating natural burdens. The RMR of the elephant shrews was quantified by measuring the oxygen consumption in an open through-flow system. The RMR of hosts infested only with larvae did not differ from that of the control group. Those infested with nymphs, or nymphs and larvae, had significantly lower RMR's compared to the control animals. There were no signs of paralysis in any of the infested hosts.