Virus and its relationship to the "poor performance" syndrome

Racehorses perform badly for many different reasons. Trainers often expect clinicians to determine the cause in individual cases and, more especially, where most of the immates of the stable are apparently affected by loss of form. Clinical examinations may reveal signs including fever, serous nasal discharge and the occasional cough. Haematology and blood biochemistry are commonly used aids to diagnosis in the field and may be helpful, but there is a need for facilities for virological investigations to be made readily available for use by clinicans as an adjunct to more commonplace laboratory techniques. This paper presents the background to a serious and widely publicised problem experienced by racing stables in the UK in recent years and, in discussing its epidemiology, lays emphasis on upper respiratory tract (URT) disease caused by viruses. It is suggested that, if the incidence of URT disease could be reduced, there would be a corresponding diminution of the "poor performance" syndrome. The inter-relationship of viral diagnosis, epidemiology and research is discussed in terms of methology, interpreting results and limits of present day knowledge.     

Age of calf at weaning of spring-calving beef cows and the effect on cow and calf performance and production economics

Over a 5-yr period, spring-calving cows were used in a carry-over design experiment to evaluate effects of calf age at weaning on cow and calf performance and production economics. Weaning management groups were early (n = 60, calf age 150 d, EW), traditional (n = 60, calf age 210 d, NW), and late (n = 60, calf age 270 d, LW). Cow body condition score (BCS) and weights at the last weaning date were different (P < .05) for EW (5.8, 583 kg), NW (5.5, 560 kg), and LW (5.2, 541 kg) management groups. Pregnancy rates among groups were similar. Days on feed for groups differed (P = .001) and was 247 for EW, 204 for NW, and 164 d for LW steers. Average daily gain in the feedlot differed (P = .01) among groups and averaged 1.5 kg for LW, 1.4 kg for NW, and 1.3 kg for EW steers. Dry matter intake while steers were in the feedlot was greater (P = .001) for LW than for NW and EW calves. Hot carcass weight was greater (P = .01) for EW (328 kg) and NW (332 kg) calves than for LW (321 kg) steers, and fat depth was greater (P = .05) for EW and NW steers than for LW steers. When carcass data for the NW and LW steers were adjusted to the fat depth of EW steers, carcass characteristics among groups were similar. Net income per steer at slaughter for the feedlot phase was greater (P < .001) for the EW ($75.36) and NW ($62.16) steers than for the LW ($10.09) steers. Again, when carcass data for the NW and LW steers were adjusted to the same fat depth of the EW steers, net income differences among groups were reduced. Replacement heifers were developed in a drylot and costs were higher (P < .001) for the EW than for NW and LW heifers. Annual cow costs were greater (P < .10) for the LW ($443.45) than for the EW ($410.09) and NW ($421.35) groups. Break-even for each system on a steer financial basis was not different between the NW and LW groups, and both the NW and LW groups had lower (P = .08) break-evens than the EW group. Age of the calf at weaning affects cow weight and BCS. Net income in each system is influenced by cow costs, month of the year that steer calves are purchased into the feedlot and finished steers are sold, month of the year cull cows are marketed, and replacement heifer development costs.     

代乳粉对犊牛生产性能的影响

用10头7～10日龄中国荷斯坦母犊牛分为2组,对照组犊牛按常规进食鲜牛奶,试验组犊牛进食代乳粉。60天的试验表明:饲喂代乳粉可提高犊牛的免疫力,减少犊牛的腹泻率;代乳粉对犊牛的生长发育没有不良影响;试验结束时犊牛的增重情况与哺乳的犊牛接近(P>0.05);使用代乳粉可节省大量鲜奶,降低生产成本。     

Subclinical mastitis in ewes and its effect on lamb performance.

Two studies were conducted to 1) assess the effectiveness of the California mastitis test (CMT) relative to direct microscopic somatic cell count (DMSCC) and(or) somatic cell count (SCC) procedures for detecting subclinical mastitis in ewes, 2) determine the incidence of subclinical mastitis based on repeated or single sample measures and organisms associated with the inflammation, and 3) assess the relationship between milk quality measures and lamb performance. The relationship between DMSCC and SCC scores was significant (P less than .01); 90% of the variation in DMSCC scores was accounted for by SCC scores. In contrast, CMT scores accounted for only 26% of the variation in DMSCC and 30 to 34% of the variation in SCC scores. Incidence of inflammation varied from 17 to 50% of ewes tested, depending on the study and the method of assessment. Staphylococcus species were cultured from 14/41 samples tested, with cultures of Streptococcus species (3/41) and Micrococcus species (1/41) also present. The effect of subclinical mastitis in ewes on lamb performance was minimal when assessed by regressing lamb weights on subclinical mastitis and milk quality scores. In conclusion, growth performance of lambs in a management system where they had access to supplemental feed was not influenced by the quality of milk produced by ewes, or by the degree of subclinical mastitic inflammation present when they suckled.     

Brachyspina syndrome in a Holstein calf.

A stillborn premature Holstein calf was necropsied. The calf had severely reduced body weight and shortening of the vertebral column. The limbs appeared long and thin. Radiography and computer tomography scanning were performed, demonstrating malformation of the vertebral column. In addition, malformation of the kidneys, testicles, and heart was found at necropsy. Histologically, absence or incomplete development of intervertebral discs and complete or partial fusion of the epiphyses of adjacent vertebrae were found. In some areas, diaphyses of adjacent vertebrae were fused due to absence of epiphyses and intervertebral discs. Disturbed ossification of epiphyses in the appendicular skeleton was also present. The etiology of this syndrome was not identified. An inherited cause is possible due to a close relationship between the parents.     

Calving performance and calf mortality

The most important maternal factor influencing calving performance is parity. Among calf factors, birth weight seems the most important. There are large differences between breeds and, generally speaking, heavier beef and dual-purpose breeds present more problems than smaller cattle. Variation in calving performance and stillbirth may be attributed to characters of both the calf and the dam. Genetic variation in calving performance and stillbirth at first calving has been demonstrated in several investigations for both the direct (calf) and the maternal character.In a Swedish investigation a heritability of 10% was found for both the direct and the maternal character. For stillbirth values were on average 3%. A strong genetic relationship was found between calving performance and birth weight as direct characters (r_GD = 0.98) but for the maternal characters it was considerably weaker (r_GM = 0.60). Correlations between stillbirth rate and birth weight were generally weaker, because the relationship was non-linear. Estimations of the genetic correlations between direct and maternal effects gave values between zero and ?0.5 for the characters investigated, indicating an antagonistic relationship between the genetic make-up of the cow and the calf. This implies that, in the long run, selection will not be as effective as the heritabilities suggest.A substantial improvement in calving performance and calf mortality can be achieved, however, through selection within breeds, optimal organization of breeding structures, choice of appropriate beef breeds for cross-breeding on heifers and cows, respectively, and timing calving to occur at favourable ages and in favourable seasons.     

Isolation of a subgroup two adenovirus from calf with weak calf syndrome.

A viral agent, designated Id-1, was isolated from the buffy coat of a calf suffering from weak calf syndrome. The virus replicated on bovine salivary gland cells and caused cytopathic effect within four days after infection-Cytopathic effect was characterized by rounding and clumping of cells. Stained preparations of infected monolayers revealed multiple intranuclear inclusions. The agent was found to be resistant to chloroform, ether, trypsin, sodium desoxycholate, oxytetracycline and a pH range of three to nine. The virus was sensitive to 5-iodo-2'-deoxyuridine and to a temperature of 70 degrees C. Cross neutralization tests with Id-1 antiserum and bovine adenovirus type 7 (strain Fujuroi) antiserum resulted in complete neutralilation of both viruses with four or less antibody units of homologous or heterologous antiserum.     

Studies on effect of lighting on "Sudden death syndrome" in broiler chickens.

Broiler chicken flocks were studied to determine the mortality from sudden death syndrome occurring in the flocks. The difference in the incidence of the syndrome in pullets and cockerels, and the age at which the most birds are affected were also studied. The weight of sudden death syndrome birds was compared with the flock average and the effect of continuous lighting as opposed to intermittent lighting was examined.The results suggest that; continuous lighting produces more sudden death syndrome deaths than intermittent lighting; that the incidence of sudden death syndrome is higher in cockerels than pullets; that the highest death rate occurred during the third and fourth weeks of life, and that sudden death syndrome birds on the average were heavier than the flock average.     

Neonatal immune development in the calf and its impact on vaccine response.

In this article we cover the immunologic response as it develops, the components of passive immunity, and the immune response of young calves. We discuss interference from maternal immunity in the development of specific immunity and vaccine strategies for developing protection against pathogens in calves.     

Predictors of beef calf temperament at weaning and its impact on temperament at breeding and reproductive performance

Two experiments were conducted to determine (i) factors influencing calf temperament at weaning, (ii) association between heifer–calf temperament at weaning and temperament at breeding and (iii) effect of heifer–calf temperament on pregnancy rate per artificial insemination (P/AI). In experiment 1, beef cows and their calves (n = 285) from three farms were used. Sire docility estimated progeny difference (EPD) score, birth type (normal or assisted), calf gender, calf behaviour (during 1st 4 weeks) and calf health status (until weaning) were recorded. Cows and calves were assigned a temperament score (0—calm; 1—excitable), and all cows were given a body condition score (BCS, 1–9; 1—emaciated; 9—obese) at weaning. Calf's illness (p < .05), low sire docility EPD score (p < .05), altered gait (p < .05), altered resting behaviour (p < .01), reduced/no play behaviour (p < .05) and cow excitable temperament (p < .001) increased calf excitable temperament at weaning. In experiment 2, replacement heifer–calves (n = 758) from 12 farms were assigned a temperament score at weaning and later at breeding. Blood from 40 calves at weaning and 31 heifers at initiation of synchronization (same animals) was collected by coccygeal venipuncture for determination of circulating cortisol and substance P concentrations. Heifers were assigned a BCS and reproductive tract score (RTS, 1–5; 1—immature, acyclic; 5—mature, cyclic), synchronized for fixed time AI, observed for oestrus and were artificially inseminated. Cortisol concentrations were increased in excitable heifer–calves compared to calm heifer–calves at weaning (p < .05), and substance P was increased in excitable compared to calm females both at weaning and breeding (p < .05). Low sire EPD docility score (p < .01), heifer–calf excitable temperament at weaning increased excitable temperament at breeding (p < .01). Controlling for BCS categories (p < .01), oestrous expression (p < .0001) and temperament at breeding by oestrous expression (p < .05), the calf's excitable temperament at weaning (p < .001) reduced P/AI (Calm, 62.7 (244/389) vs. Excitable, 53.4% (197/369); p < .01). In conclusion, selection of docile cows and sires with greater docility EPD score should be given consideration to reduce calf excitement. Temperament in beef female can be detected earlier in their life and could be used as a tool in the selection process and to improve their performances.     

"Shaker" calf syndrome: a newly recognized inherited neurodegenerative disorder of horned Hereford calves

The clinical and pathological features of a newly recognized, inherited neurodegenerative disorder in horned Hereford calves are described. The disorder is expressed in newborns by tremulous shaking of the head, body and tail, difficulty in rising, a wobbly spastic gait, and aphonia. Transient improvement is followed by deterioration and progressive spastic paraplegia. Generalized tremors can be induced easily by a variety of stimuli, and spinal reflexes may be exaggerated or depressed. The major pathological finding is an excessive accumulation of neurofilaments within neurons of the central, peripheral, and autonomic nervous systems. The involvement of multiple systems of neurons and the similarity with some forms of human motor neuron disease and spinocerebellar degeneration suggest that this unique bovine disease may serve as a suitable animal model for these human neurodegenerative disorders.     

Atypical hypoplastic left ventricular syndrome in a calf.

An 8-day-old male Angus calf was presented to the University of Illinois, Veterinary Teaching Hospital, Urbana, IL, for lethargy, weakness, and poor suckle reflex. Clinical evaluation revealed a strong left-sided heart murmur and a split S2 sound. The calf died within 48 hours. Necropsy revealed a combination of the following cardiac defects: left ventricular hypoplasia, high ventricular septal defect, left auricular atresia with mitral valve aplasia, patent foramen ovale, patent ductus arteriosus, and pulmonary trunk atresia. Mild suppurative pneumonia with pulmonary edema and congestion were also present. This combination of defects appears to be similar to the hypoplastic left heart syndrome in humans and is reported here for the first time in cattle.     

Mastitis in beef cows and its effects on calf weight gain.

Quarter milk samples from 51 purebred (Angus, Polled Hereford, and Simmental) and 69 crossbred (Angus x Simmental x Charolais three-way cross) beef cows were collected aseptically at three times during lactation to determine the prevalence of intramammary infection, milk somatic cell counts (SCC), and effects of infection on calf weight gain. Quarter infection prevalence was 13.1, 14.9, and 27.5% in early, mid, and late lactation; corresponding cow infection prevalence was 25.8, 29.2, and 54.4%. Staphylococcus aureus was isolated from 2.9, 2.7, and 3.2% of quarters in early, mid, and late lactation, respectively. Corynebacterium bovis, generally regarded as a minor pathogen, was isolated from 4.0, 7.6, and 18.2% of quarters at the three respective times. Geometric SCC means (10(3) cells/ml) were 1,522, 344, and 509 for S. aureus-infected quarters; 344, 899, and 221 for Staphylococcus hyicus-infected quarters; 65, 36, and 86 for C. bovis-infected quarters; and 20, 17, and 18 for uninfected quarters in early, mid, and late lactation, respectively. Adjusted 205-d weight gain for calves with S. aureus-infected dams was 9.6 kg less (P less than .05) than for calves with uninfected dams. Adjusted 205-d weight gain for calves with dams infected with any mastitis pathogen did not differ significantly from that of calves with uninfected dams. At weaning half of the infected cows and half of the uninfected cows were given an intramammary infusion product containing 300 mg of cephapirin benzathine in each quarter; the remaining cows were untreated controls. Quarter samples were collected aseptically from all cows 14 to 28 d after subsequent calving. Quarter prevalence of infection after calving was lower (P less than .05) in treated (8.2%) than in control (22.4%) cows. Significantly more infections present at weaning were eliminated in treated than in control cows, but the new infection rate during the dry period and early lactation did not differ between the two groups.     

Infectivity of bovine adenovirus type 5 recovered from a polyarthritic calf with weak calf syndrome.

Bovine adenovirus type 5, isolated from newborn calves with a polyarthritic disease known as "weak calf syndrome" caused a mild, self-limiting illness in susceptible calves. The induced illness was characterized by marked pyrexia and occasionally by mild diarrhea. It was concluded that the virus may contribute to morbidity and mortality associated with the weak calf syndrome by adding to the stress and debilitation caused by cold wet weather and by bovine viral diarrhea (BVD) virus, which has also been isolated from tissues of calves affected with weak calf syndrome.     

The effect of body condition, live weight, breed, age, calf performance, and calving date on reproductive performance of spring-calving beef cows.

Data from 321 spring-calving cows (mean calving date March 27) were used to assess the effects of body condition, live weight, cow age (from 4 to 13 yr), and breed (237 Hereford x Friesians and 84 Blue-Greys) and time of calving on the proportion of cows that became pregnant, the number of days from the start of mating to pregnancy, and calving interval. Mating started at turn-out to pasture in mid-May and lasted 9 to 10 wk. Body condition at calving and breed were the most significant animal factors affecting reproductive performance. Cows calving in higher body condition had shorter (P less than .001) calving intervals (11.2 d per unit of body condition at calving). Blue-Grey cows became pregnant in a higher proportion (90%) and calving interval was shorter (364 d) than in Hereford x Friesians (83%; 374 d). Body condition at the start of mating was less important and body condition at the end of mating had no effect. Live weight at calving and changes in live weight from calving to the start of mating and during the mating period had no significant effect. The proportion of cows becoming pregnant decreased significantly with age in Hereford x Friesian cows older than 7 yr. The variance in calving interval accounted for by calving date, body condition at calving, breed, and age was 42%.     

Neonatal respiratory distress syndrome in the calf

Thirty-five calves were delivered by caesarean section near to term. During the operation amniotic fluid was collected for determination of the lecithin/sphingomyelin (L/S) ratio. Clinical examination of the calves and analysis of blood gas concentration (venous blood) were carried out within the first hour of life. Fifteen out of 35 calves under examination did not show clinical or blood gas disorders in the course of the first hour of life. In these calves, the L/S ratio, which represents a measure for the maturity of the surfactant system, averaged 2.6. The other 20 calves, however, developed a respiratory distress syndrome together with a progressive respiratory and metabolic acidosis within the first hour of life. The L/S ratio in the animals affected with respiratory distress syndrome reached an average value of 1.5 which was significantly below that of the calves not suffering from respiratory distress. Eleven of the 20 calves which developed respiratory distress syndrome died within the first 60 hours of life. The most striking findings in the post mortem examinations of these animals were intracranial haemorrhages and pulmonary lesions (hyaline membranes, interstitial and alveolar oedema). On the basis of the significantly lower L/S ratio and the post mortem findings, it is to be assumed that the respiratory distress syndrome in calves, equally with that in infants, is attributable to a surfactant deficiency.