Breeding Herd Research Articles

Emergence of Brachyspira species and strains: reinforcing the need for surveillance.

This short review discusses the increasing complexity that has developed around the understanding of Brachyspira species that infect pigs, and their ability to cause disease. It describes the recognition of new weakly haemolytic Brachyspira species, and the growing appreciation that Brachyspira pilosicoli and some other weakly haemolytic species may be pathogenic in pigs. It discusses swine dysentery (SD) caused by the strongly haemolytic Brachyspira hyodysenteriae, particularly the cyclical nature of the disease whereby it can largely disappear as a clinical problem from a farm or region, and re-emerge years later. The review then describes the recent emergence of two newly described strongly haemolytic pathogenic species, “Brachyspira suanatina” and “Brachyspira hampsonii” both of which appear to have reservoirs in migratory waterbirds, and which may be transmitted to and between pigs. “B. suanatina” seems to be confined to Scandinavia, whereas “B. hampsonii” has been reported in North America and Europe, causes a disease indistinguishable from SD, and has required the development of new routine diagnostic tests. Besides the emergence of new species, strains of known Brachyspira species have emerged that vary in important biological properties, including antimicrobial susceptibility and virulence. Strains can be tracked locally and at the national and international levels by identifying them using multilocus sequence typing (MLST) and comparing them against sequence data for strains in the PubMLST databases. Using MLST in conjunction with data on antimicrobial susceptibility can form the basis for surveillance programs to track the movement of resistant clones. In addition some strains of B. hyodysenteriae have low virulence potential, and some of these have been found to lack the B. hyodysenteriae 36 kB plasmid or certain genes on the plasmid whose activity may be associated with colonization. Lack of the plasmid or the genes can be identified using PCR testing, and this information can be added to the MLST and resistance data to undertake detailed surveillance. Strains of low virulence are particularly important where they occur in high health status breeding herds without causing obvious disease: potentially they could be transmitted to production herds where they may colonize more effectively and cause disease under stressful commercial conditions.

Body size estimation of new born lambs using image processing and its effect on the genetic gain of a simulated population

In this study the possibility of body size estimation of new born lambs using image processing and its effect on the genetic gain of a simulated population has been investigated. The body size of 158 new born lambs of Zandi sheep was evaluated via appraisal method, digital image processing and metric methods. The correlation coefficients between metric lamb size with quantities were calculated from image processing method and appraisal method were 0.88 and 0.48, respectively (P < 0.01). In the next step, two populations were randomly simulated using R2.15 programming environment, and two different scenarios based on two lamb size measurement methods were studied. In the first scenario, it was assumed that the animal body size is determined using image processing technique in continuous values, while in the second scenario it was assumed that the body size is determined via appraisal method in discrete values. As results, the accuracies of breeding value estimations in the first and second scenario were 0.89 and 0.78, and the genetic trends were 0.46 and 0.28, respectively (P < 0.01). The results showed that determination of lamb size based on proposed image processing method is feasible, and replacement of this new method instead of human appraisal method could increase the genetic gain in the breeding herds.

Relationships between day one piglet serum immunoglobulin immunocrit and subsequent growth, puberty attainment, litter size, and lactation performance.

Colostrum affects gut and uterine gland development in the neonatal piglet, suggesting that subsequent growth and reproductive performance may be affected. Measuring immunoglobulin in piglet serum using the immunoglobulin immunocrit on Day 1 of age provides a simple, inexpensive indication of the amount of colostrum acquired by the piglet in the first day of life. Relationships between serum immunoglobulin immunocrit measures and subsequent growth rates, age at puberty, incidence of puberty failure, litter size, and lactation performance were examined in pigs born and subsequently farrowing between 2009 and 2013. Immunoglobulin immunocrit measures were collected on 16,762 piglets on Day 1 of age. Of these piglets, BW measurements were available from 15,324 (7,684 males and 7,640 females) piglets at a range of ages from weaning to 200 d of age, allowing an assessment of growth rates. Age at puberty was recorded from a subset of 2,857 of the females after observing them for estrous behavior from approximately 170 to 250 d of age. To examine relationships between d 1 immunocrit and puberty failure, gilts with immunocrit measures that failed to reach puberty (n = 119) were matched with littermate gilts with immunocrit measures that achieved puberty (n = 167). Similarly, number born alive was collected on a subset (n = 799) of females from first to fourth parities for which d 1 immunocrits were measured on them as neonates. Finally, d 1 immunocrit effect on adult lactational competence was assessed by measuring litter average (offspring of 440 females) and litter average piglet preweaning growth rate (offspring of 774 females) in females where d 1 immunocrits were available from them as neonates. Results indicated that low d 1 immunocrits were subsequently associated with reduced growth (P < 0.01), increased age at puberty (P < 0.01), reduced number born alive (P < 0.05), reduced litter average immunocrit (P < 0.05), and reduced litter average preweaning growth rate during lactation (P < 0.05). This suggests that management efforts to improve the amount of colostrum ingested by neonatal piglets would result in beneficial changes in production efficiency, particularly for gilts destined for the breeding herd. It also suggests that the immunoglobulin immunocrit can be useful in monitoring colostrum ingestion to maximize the beneficial effects of colostrum on subsequent performance.

Genetic parameters of ovarian and uterine reproductive traits in dairy cows

The objective of the study was to estimate genetic parameters of detailed reproductive traits derived from ultrasound examination of the reproductive tract as well as their genetic correlations with traditional reproductive traits. A total of 226,141 calving and insemination records as well as 74,134 ultrasound records from Irish dairy cows were used. Traditional reproductive traits included postpartum interval to first service, conception, and next calving, as well as the interval from first to last service; number of inseminations, pregnancy rate to first service, pregnant within 42 d of the herd breeding season, and submission in the first 21 d of the herd breeding season were also available. Detailed reproductive traits included resumed cyclicity at the time of ultrasound examination, incidence of multiple ovulations, incidence of early postpartum ovulation, heat detection, ovarian cystic structures, embryo loss, and uterine score; the latter was a subjectively assessed on a scale of 1 (little fluid with normal uterine tone) to 4 (large quantity of fluid with a flaccid uterine tone). Variance (and covariance) components were estimated using repeatability animal linear mixed models. Heritability for all reproductive traits were generally low (0.001–0.05), with the exception of traits related to cyclicity postpartum, regardless if defined traditionally (0.07; calving to first service) or from ultrasound examination [resumed cyclicity at the time of examination (0.07) or early postpartum ovulation (0.10)]. The genetic correlations among the detailed reproductive traits were generally favorable. The exception was the genetic correlation (0.29) between resumed cyclicity and uterine score; superior genetic merit for cyclicity postpartum was associated with inferior uterine score. Superior genetic merit for most traditional reproductive traits was associated with superior genetic merit for resumed cyclicity (genetic correlations ranged from −0.59 to −0.36 and from 0.56 to 0.70) and uterine score (genetic correlations ranged from −0.47 to 0.32 and from 0.25 to 0.52). Genetic predisposition to an increased incidence of embryo loss was associated with both an inferior uterine score (0.24) and inferior genetic merit for traditional reproductive traits (genetic correlations ranged from −0.52 to −0.42 and from 0.33 to 0.80). The results from the present study indicate that selection based on traditional reproductive traits, such as calving interval or days open, resulted in improved genetic merit of all the detailed reproductive traits evaluated in this study. Additionally, greater accuracy of selection for calving interval is expected for a relatively small progeny group size when detailed reproductive traits are included in a multitrait genetic evaluation.

Evidence that periweaning failure-to-thrive syndrome (PFTS) has a genetic predisposition

Genetic susceptibility or resistance to diseases is currently drawing increasing attention. This work describes two different breeding herds showing signs of periweaning failure-to-thrive syndrome (PFTS), an emergent swine disease. The...

Survival time of calves with positive BVD virus results born during the voluntary phase of the Irish eradication programme

A retrospective case–control study was undertaken to investigate the temporal pattern of, and factors associated with, the survival of BVD virus-positive calves, identified between January and July 2012 during the voluntary phase of the Irish national eradication programme. Potential statuses for case and control calves consisted of: alive in birth herd; slaughtered; sold; dead (due to culling or death from natural causes and termed ‘involuntary removal’).An initial comparison of cases and controls found significant differences between the outcomes for cases and controls and also between cases in relation to herd type (beef, dairy, dual purpose), sex, age and test status (BVDPOS – no confirmatory test; BVDPI – positive on confirmatory test). Key differences included a higher level of case animals still alive in, or slaughtered from, beef herds, a greater proportion of BVDPI animals being retained relative to those with a BVDPOS status and a significantly lower slaughter weight (89kg) for case animals relative to controls.Separate multivariable models were constructed for dairy and beef cases. In the final dairy model breed (Jersey or non-Jersey), county and BVD status were retained, with the last two found to be time-varying covariates with significant changes in hazard ratios (HR) over time. In the beef model, herd size, county and BVD status were retained, with the HR for the last two factors again varying significantly over time. With the exception of the addition of the number of BVD positive calves in the herd to the dairy model, the same factors were identified when models were restricted to the first 90 days following the birth of case animals.A greater knowledge and understanding of all of these factors will allow refinement of programme communications and incentives to encourage prompt removal of PI calves from all sectors of the Irish breeding herd during the compulsory phase of the national eradication programme.

Важнейшие стресс-адаптивные реакции в системе «мать – плод» у коров

Рассмотрены некоторые причины снижения результатов воспроизводства стада и предложены мероприятия по своевременному выявлению тех или иных отклонений при получении слабого приплода в животноводстве.

A Farm Transmission Model for Salmonella in Pigs, Applicable to E.U. Member States.

The burden of Salmonella entering pig slaughterhouses across the European Union is considered a primary food safety concern. To assist E.U. member states with the development of national control plans, we have developed a farm transmission model applicable to all member states. It is an individual-based stochastic susceptible-infected model that takes into account four different sources of infection of pigs (sows, feed, external contaminants such as rodents, and new stock) and various management practices linked to Salmonella transmission/protection (housing, flooring, feed, all-in-all-out production). A novel development within the model is the assessment of dynamic shedding rates. The results of the model, parameterized for two case study member states (one high and one low prevalence) suggest that breeding herd prevalence is a strong indicator of slaughter pig prevalence. Until a member state's' breeding herd prevalence is brought below 10%, the sow will be the dominant source of infection to pigs raised for meat production; below this level of breeding herd prevalence, feed becomes the dominant force of infection.

Current strategies for reproductive management of gilts and sows in North America.

Many advances in genetic selection, nutrition, housing and disease control have been incorporated into modern pork production since the 1950s resulting in highly prolific females and practices and technologies, which significantly increased efficiency of reproduction in the breeding herd. The objective of this manuscript is to review the literature and current industry practices employed for reproductive management. In particular the authors focus on assisted reproduction technologies and their application for enhanced productivity. Modern maternal line genotypes have lower appetites and exceptional lean growth potential compared to females of 20 yr ago. Thus, nutrient requirements and management techniques and technologies, which affect gilt development and sow longevity, require continuous updating. Failure to detect estrus accurately has the greatest impact on farrowing rate and litter size. Yet, even accurate estrus detection will not compensate for the variability in the interval between onset of estrus and actual time of ovulation. However, administration of GnRH analogs in weaned sows and in gilts after withdrawal of altrenogest do overcome this variability and thereby synchronize ovulation, which makes fixed-time AI practical. Seasonal infertility, mediated by temperature and photoperiod, is a persistent problem. Training workers in the art of stockmanship is of increasing importance as consumers become more interested in humane animal care. Altrenogest, is used to synchronize the estrous cycle of gilts, to prolong gestation for 2–3 d to synchronize farrowing and to postpone post-weaning estrus. P.G. 600® is used for induction of estrus in pre-pubertal gilts and as a treatment to overcome seasonal anestrous. Sperm cell numbers/dose of semen is significantly less for post cervical AI than for cervical AI. Real-time ultrasonography is used to determine pregnancy during wk 3–5. PGF2α effectively induces farrowing when administered within two d of normal gestation length. Ovulation synchronization, single fixed-time AI and induced parturition may lead to farrowing synchronization, which facilitates supervision and reduces stillbirths and piglet mortality. Attendance and assistance at farrowing is important especially to ensure adequate colostrum consumption by piglets immediately after birth. New performance terminologies are presented.

Genetic diversity in selected stud and commercial herds of the Afrikaner cattle breed

The Afrikaner is one of three indigenous cattle breeds found in South Africa. Afrikaner cattle were originally extensively used for crossbreeding purposes and breed development. The objective of this study was to determine the genetic diversity of selected stud and commercial herds from the whole South African Afrikaner population, as well as to determine the genetic structure among these herds. Assignment methods (based on STRUCTURE software) revealed a real structure consisting of four genetic populations (K = 4). Estimates of genetic diversity did not support the hypothesis of significant loss of genetic diversity in any individual Afrikaner herd. Heterozygosity estimates ranged from 0.456 - 0.737 within individual populations, with an overall heterozygosity estimate of 0.568 for the Afrikaner breed. The average number of alleles per locus was regarded as being 2.67 - 7.78, with an average of 5.18 alleles per locus. It could be concluded that a moderate to high degree of variation is still present within the Afrikaner cattle breed, despite the recent decline in numbers of this indigenous breed.Keywords: Bos taurus africanus, heterozygosity, inbreeding, microsatellite markers

Assessment of temperament in Rusa timorensis and its relationship to stress.

The delayed domestication of may be associated with their poor temperament and to date there is no published information on the temperament of the farmed Understanding of the temperament and selection program for its evaluation in a breeding herd is important not only for farming but also to other types of animal production. We investigated the temperament of ( = 17) raised in the tropics and determined its relationship with stress. A distance of 13.2 m was fixed for the measurement of flight times. hinds with rapid speed are considered temperamental. Each hind was earmarked for a crush test score between 1 and 5; 1 represents calm and 5 represents highly agitated . Stress was determined by measuring plasma cortisol using a cortisol RIA kit and live weight gain was determined by weighing the animals weekly. The hinds were aged using their date of birth records. We found a strong negative correlation between flight time, crush score, and plasma cortisol concentration ( < 0.05). Animals with very poor temperament have elevated plasma cortisol level and lower weight gain ( < 0.05). It was concluded that flight time, crush score, and plasma cortisol concentration could be used for selecting hinds based on temperament for the breeding herd. This method is quick and easy to implement on a farm; therefore, it remains the test choice for selecting animals based on temperament for the breeding herd.

Previous infection of sows with a “mild” strain of porcine epidemic diarrhea virus confers protection against infection with a “severe” strain

Porcine epidemic diarrhea virus (PEDv) infected approximately 50% of the US swine breeding herds from July 2013 to July 2014 as estimated by the Swine Health Monitoring Project. In the absence of effective vaccines or standard control protocols, there is an urgent need for evidence of cross-protective immune countermeasures. Here, we evaluated the response of 3-day-old piglets born to sows exposed seven months earlier to a mild strain of PEDv to challenge with a virulent PEDv isolate. Piglet survival to one week of age was 100% compared to 67% in piglets born to sows not previously exposed, and morbidity was 43% compared to 100%, respectively. At necropsy at 7 days of age, the PEDv Ct value was 23.6 (range 16.6–30.6) in intestinal contents, compared to 17.2 (range 15.9–18.5) (p<0.06) in litters from sows with no previous exposure to PEDv. The findings indicated that durable lactogenic immunity was present in sows previously exposed to a mild strain of PEDv and this immunity induced cross-protection to representative virulent PEDv. Thus, a naturally attenuated form of PEDv provided significant passive immune protection for seven months against piglet challenge with virulent PEDv.

Adverse effects of Influenza A(H1N1)pdm09 virus infection on growth performance of Norwegian pigs - a longitudinal study at a boar testing station.

BackgroundInfluenza A(H1N1)pdm09 virus infection in Norwegian pigs was largely subclinical. This study tested the hypothesis that the infection causes negligible impact on pigs’ growth performance in terms of feed conversion efficiency, daily feed intake, daily growth, age on reaching 100 kg bodyweight and overall feed intake. A sample of 1955 pigs originating from 43 breeding herds was classified into five infection status groups; seronegative pigs (n = 887); seropositive pigs (n = 874); pigs positive for virus at bodyweight between 33 kg and 60 kg (n = 123); pigs positive for virus at bodyweight between 61 kg and 80 kg (n = 34) and pigs positive for virus at bodyweight between 81 kg and 100 kg (n = 37). Each pig had daily recordings of feed intake and bodyweight from 33 kg to 100 kg. Marginal effects of the virus infection on the outcomes were estimated by multi-level linear regression, which accounted for known fixed effects (breed, birthdate, average daily feed intake and growth phase) and random effects (cluster effects of pig and herd).ResultsThe seropositive and virus positive pigs had decreased (P value<0.05) growth performance compared to seronegative pigs even though feed intake was not decreased. Reduced feed conversion efficiency led to lower average daily growth, additional feed requirement and longer time needed to reach the 100 kg bodyweight. The effects were more marked (P value<0.03) in pigs infected at a younger age and lasted a longer period. Despite increased feed intake observed, their growth rates were lower and they took more time to reach 100 kg bodyweight compared to the seronegative pigs.ConclusionOur study rejected the null hypothesis that the virus infection had negligible adverse effects on growth performance of Norwegian pigs.

On-farm characteristics and biosecurity protocols for small-scale swine producers in eastern Australia

Pigs are considered high risk for the introduction and spread of foot and mouth disease (FMD) in Australia. Facilities where animals from different origins are commingled, such as saleyards, pose a high risk for disease spread. Sound on-farm management practices and biosecurity protocols are the first line of defence against a potential on-farm disease outbreak. This study evaluated the practices of 104 producers (vendors who sold pigs and purchasers of live pigs for grow-out) who traded pigs at 6 peri-urban and rural saleyards in eastern Australia. Specifically, management and on-farm biosecurity practices were assessed using an in-depth questionnaire. Univariable and multivariable logistic regression analyses were used to investigate (1) producer associations: producer type, State, motivation to keep pigs, farm type, gender, years having owned pigs, and the acquisition of formal livestock qualifications; and (2) pig associations: herd size, housing, management (husbandry and feeding) practices and biosecurity (including pig movement) practices. Backyard operations (<20 sows) were undertaken by 60.6% of participants, followed by small-scale pig operations (28.8%; 21–100 sows). Few producers (16.3%) reported residing in close proximity (<5km) to commercial operations; however, less rural producers had neighbouring hobby pig operations within 5km of their property (P=0.033). Motivation for keeping pigs was significantly associated with a number of biosecurity practices. Producers who kept pigs for primary income were more likely to provide footwear precautions (P=0.007) and ask visitors about prior pig contacts (P=0.004). Approximately 40% of backyard and small-scale producers reported not having any quarantine practices in place for incoming pigs, compared to only 9.1% among larger producers. The main reasons cited for not adopting on-farm biosecurity practices in this study included having no need on their property (43.1%) and a lack of information and support (by the industry and/or authorities; 18.5%). Up to three-quarters of all producers maintained an open breeding herd, regularly introducing new pigs to the main herd. Saleyards are an important source of income for backyard and small-scale producers as well as an important risk factor for the introduction and dissemination of endemic and emerging animal diseases. Differing management and biosecurity practices as well as the motivations of these producers keeping pigs in small numbers and trading pigs at saleyards need to be taken into account in the development of successful biosecurity extension programmes for this sector of the Australian pork industry.

Detection of porcine reproductive and respiratory syndrome virus in the ovary of gilts culled due to reproductive disturbances

Replacement gilts are a major source of introducing the porcine reproductive and respiratory syndrome (PRRS) virus into the swine breeding herd. The objective of the present study was to determine the prevalence of PRRS virus antigen by detection in the ovary of gilts culled due to reproductive disturbances. Ovarian tissues were collected from 100 Landrace x Yorkshire crossbred slaughtered gilts in Thailand. PRRS virus antigen in the ovarian tissues were detected by using immunohistochemistry. On average, the gilts were culled at 277 days of age at a body weight of 148 kg. Of these gilts, 75 had attained puberty and 25 had not attained puberty. PRRS virus antigens were detected in the macrophages within the ovary. The histological morphology of macrophages containing the PRRS virus in ovarian tissue was similar to that found in the lung tissue. Of all the ovarian tissues (n = 100), the PRRS virus was detected in 70 (70.0 %) ovaries. The detection frequency of the PRRS virus in the ovarian tissue of gilts did not differ significantly among the culling reasons (P = 0.496). The gilts that had exhibited standing oestrus had a lower PRRS virus detection than those that had never exhibited standing oestrus (62.8 versus 92.0 %, respectively, P = 0.005). Gilts with a body weight of 151–160 kg had a higher frequency of PRRS virus detection (89.5 %) than gilts with a body weight of ≤130 kg (52.9 %, P = 0.025) and 131–140 kg (50.0 %, P = 0.032). The ovulation rate in the ovary containing the PRRS virus tended to be lower than the ovary without the PRRS virus (14.8 and 16.7 corpora lutea (CL), respectively, P = 0.196). These findings indicated that the natural exposure to PRRS virus in the replacement gilts caused an existence of the virus in the ovarian tissues and may subsequently influence the ovarian function.

Sow Productivity on Commercial Pig Farms in the Republic of Macedonia

Abstract The objectives of the present study were to determine the production performances of sows on commercial pig farms in the Republic of Macedonia, to compare the differences in sow productivity data between small and large farms and to examine interrelationships of key production parameters among farms with different sizes. The study was retrospectively based and included the annual (2012) analyses of the sow productivity data in small (&lt;200 sows, n=4) and large (200-1000 sows, n=5) commercial pig farms. The data was statistically evaluated and compared with the known literature. Sows productivity was greater on the small farms compared to the large ones. The small farms had larger litter per sow (PBL), more pigs born alive (PBA), higher weaning weight (WW) and more pigs weaned per sow per litter (PWSL) than the large ones (p&lt;0.001). Small farms also had greater farrowing rate (FR) (p&lt;0.01). Higher replacement rate (RR), lower average parity (AP), greater number of litters per sow per year (LSY) and higher sow death rate (SDR) were observed in large farms (p&lt;0.001). The large farms also had less non-productive days (NPD) than the small farms (p&lt;0.001). Different intensity of correlations also were observed for several productive parameters among the farm groups. The data obtained in this study show that sow productivity on Macedonian pig farms is lower than in EU countries. Small herds are more efficient than the large herds. Despite all limitations, our study provides information for veterinarians regarding reproductive parameters of sows and their interrelationships on Macedonian pig farms. Further investigation should be made in order to identify whether specific management factors have effect on the productivity of the breeding herd.

The effects of season and moderate nutritional restriction on ovarian function and oocyte nuclear maturation in cycling gilts

The fertility of female pigs is impaired during summer and in response to restriction of feed intake, resulting in reduced productivity of the breeding herd. This study determined the effect of season and moderate nutritional restriction on ovarian function and oocyte developmental competence of cycling gilts. Eighty prepubescent gilts were used across two seasons—summer (S: January to March) and winter (W: June to August)—and received either a high (2.5× maintenance) or a moderately restricted (1.5× maintenance) feeding level for the first 19 days of their second estrous cycle. On Day 19, ovaries were collected post-slaughter. Diameters of all surface follicles over 1 mm were measured. All follicles ≥4 mm were aspirated and cumulus–oocyte complexes underwent in vitro maturation for ∼44 hours to assess oocyte developmental competence on the basis of metaphase II (MII) attainment. Moderate dietary nutrition reduced daily liveweight gain but did not affect the ovarian follicle population or oocyte developmental competence. The number of large follicles (≥6 mm) was lower during summer (S: 10.7 ± 1.74 vs. W: 15.5 ± 1.15, P < 0.05), as was the proportion of oocytes at the germinal vesicle stage of meiosis (S: 0.06 ± 0.02 vs. W: 0.08 ± 0.02, P < 0.05). However, the proportion of oocytes attaining MII was similar in summer and winter (S: 0.72 ± 0.04 and W: 0.69 ± 0.06, P > 0.05). Intrafollicular concentrations of luteinizing hormone were higher in summer (S: 43.05 ± 6.44 vs. W: 12.05 ± 5.12 ng/mL, P < 0.001), whereas estradiol was lower (S: 1.27 ± 0.36 vs. W: 27.52 ± 5.59 ng/mL, P < 0.001). In conclusion, our data demonstrated that in summer, follicle growth beyond 6 mm is impaired during the periovulatory period, without affecting oocyte meiotic competence. Importantly, these data also demonstrated that ovarian follicle growth and the capacity of oocytes to reach MII in vitro appear unaffected by moderate nutritional restriction during the preceding estrous cycle.

English

The present study was conducted at the Sahelian Experimental Station in Toukounous Niger, on three herds of Azawak zebu breed in order to evaluate antimicrobial susceptibility of a total of 43 Staphylococcus aureus isolated from 164 milk samples of cows with subclinical mastitis from 2010 to 2012. The highest frequency of resistance was observed for the β-lactam family: penicillin (46%) followed by oxacillin (12%). Twenty isolates were sensitive to all tested antibiotics, 12 were resistant to one of them and 11 were multi-resistant (2 to 5 antibiotics). The resistance percentage to oxacillin, enrofloxacin and clindamycin varied significantly over the 3 years (p <0.05) but not to the other antibiotics. Moreover, 90% of S. aureus isolates resistant to penicillin detected by in vitro disk diffusion possessed the blaZ gene. In conclusion, the isolates from cases of mastitis at Toukounous are more resistant to the antibiotics frequently used for treatments at the station than to other antibiotics. Key words: Mastitis, Staphylococcus aureus, antibiotic resistance, Azawak zebu, Niger.

Tick burden and prevalence of Theileria parva infection in Tarime zebu cattle in the lake zone of Tanzania.

This study was carried out to assess the distribution, abundance of different tick genera and prevalence of Theileria parva infection in Tarime zebu cattle kept in selected wards of Serengeti and Tarime districts in Mara region. Adult ticks were identified and counted from half body parts of 360 animals which were extensively managed in communal land with natural pastures. Concurrently, blood samples were collected and thereafter DNA extracted and a nested polymerase chain reaction (nPCR) was done using primers specific for p104 gene to detect the presence of T. parva DNA. Ticks were identified into four groups: Amblyomma genus, Boophilus sub-genus of Rhipicephalus genus, other species of Rhipicephalus, and Hyalomma genus. Rhipicephalus genus accounted for 71.8 % of the total ticks, whereas Amblyomma, Boophilus sub-genus of Rhipicephalus genus and Hyalomma constituted 14.1, 14.0 and 0.1 %, respectively. There were more animals (p < 0.05) infested with ticks in Tarime district (96.1 %) than in Serengeti (61.7 %). The average counts of ticks were higher in adult animals (p < 0.05) than in young animals. The overall prevalence of T. parva was 27.7 % and was higher (p < 0.05) in Serengeti (38.3 %) than in Tarime district (16.7 %). However, all animals tested positive for T. parva did not show any clinical signs of East Coast fever (ECF), suggesting the existence of subclinical infection in Tarime zebu. These results suggest that Tarime cattle can tolerate ECF infection and are likely to serve as potential carriers of T. parva to other less-tolerant cattle breeds in mixed herds. Since Tarime cattle are preferred by most farmers with mixed herds, routine screening for T. parva is highly recommended to minimize introduction of infected cattle into an immunologically naive population.

Genetic effects on first antler growth in relation to live-weight of red deer farmed in New Zealand

Deer farmed in New Zealand for venison production are a composite of Cervus elaphus subspecies. Venison production systems target supply of yearling males for slaughter at live-weights of ≥95kg between 8 and 12 months of age when first antler development is occurring. If the antlers exceed 110mm they must be removed before the animal can be transported for slaughter which adds handling and costs which some producers consider unnecessary. We hypothesised that there are associations between live-weight and first antler development that are heritable and it would be possible to select sires on the basis of delayed antler development relative to live-weight of their progeny. Antler and live-weight measurements were recorded on 1033 male progeny from three elite recorded red deer breeding herds, DNA pedigree tested as sired by 106 different stags. Spline models were fitted to the antler length and live-weight data over time. Day-of-the-year was read off these splines to define traits of live-weight when antler length reached 50mm (WA50) or 80mm (WA80), and antler length when live-weight reached 95kg (AW95). The predicted traits were analysed using a single-trait animal model incorporating the extended pedigree of the animals involved to calculate three estimated breeding values (EBVs) WA50, WA80 and AW95. The three antler traits had high heritability estimates of 0.67–0.81 with standard errors of 0.10, and were moderately-highly correlated with weaning and yearling live-weight traits. The phenotypic standard deviation of WA80 of 8.35kg or 8.6% of the mean predicted live-weight and a genetic standard deviation or 6.86kg indicated good variation within the population, providing scope for genetically improving the current New Zealand breeding herd for delayed antler growth relative to live-weight. Such selection could reduce the number of rising yearling males requiring velvet antler removal prior to slaughter.