Effect of hay on performance of Holstein calves at suckling and post-weaning

The objective of this work was to evaluate the performance of Holstein calves in suckling and post-weaning phases, intensively managed during suckling in the absence or presence of hay. Twenty-four male Holstein calves, at an average age of 15 days and initial weight of 43 kg were used in the experiment. The experimental design was completely randomized, consisting of two treatments and six replications. The treatments were as follows: 1) suckling with milk substitute + initial concentrate for calves, ad libitum + temperate grass hay (oat/ryegrass), ad libitum; 2) suckling with milk substitute + initial concentrate for calves, ad libitum. No significant difference was found between treatments for weight gain and feed conversion. However, the supply of hay caused an increase in daily dry matter intake (2.127 vs 1.894 kg). The intake of hay promoted greater stimulus to consumption of concentrate and greater weight at weaning.

Evaluation of covering materials in individual shelters and its effects on physiological responses and performance of dairy calves

In Tropical regions, the animal performance is often affected by climate conditions. This study aimed to evaluate covering materials in individual shelters, normally used to house dairy calves, and its influence on the calves physiology and performance. The design used was completely randomized, with a 2x3 factorial arrangement to compare the averages of 5% through the Tukey's test, i.e., both genders- and three types of covering in the shelters (Z - zinc; AC - asbestos cement; and WPAC - white-painted asbestos cement). Parameters evaluated included daily weight gain (DWG), dry matter intake (DMI), feed conversion (FC), rectal temperature (RT), and respiratory frequency (RF). Results showed significant differences (P < 0.05) among males (1.04kg/day) and females (0.74kg/day) for DWG and interaction between gender and treatment (P < 0.05) for zinc covering (0.562kg/day for females and 1.120kg/day for males). Significant differences were also observed in FI of animals housed under shelters with the covering of zinc (48.35kgDM/day for females and 96.91 kgDM/day for males). There were no significant differences (P > 0.05) in the FC and the RT, and there were significant differences (P < 0.05) for RF in the Z treatments (56.9 mov.min-1), WPAC (62.2 mov.min-1) and FC (70.25 mov.min-1). It was concluded that different covering materials did not affect performance and dry matter intake of dairy calves. However, the animals' physiology of thermoregulation was altered by the different covering materials used in individual shelters.

Vaccination protocol and bacterial strain affect the serological response of beef calves against blackleg

The serological response of beef calves was evaluated with different vaccination regimens against blackleg, using an official strain (MT) and a field-collected strain of Clostridium chauvoei as antigens. Sixty calves were randomly allocated to four different groups and were submitted to distinct vaccination protocols with a commercial polyvalent vaccine. Group G1 was first vaccinated at four months of age and a booster shot was given after weaning, at eight months. Group G2 was given the first dose at eight months and a booster shot 30 days later. Group G3 was vaccinated only once at eight months and the control group was not vaccinated. These alternative vaccination regimens were proposed in an effort to adequately protect cattle under open-field farming conditions. Serological evaluations were made by Elisa at 4, 8, 9 and 10 months of age. Both groups receiving booster shots had a significantly increased serological response 30 days later. However, the serum IgG levels against C. chauvoei were significantly higher in the calves that were first vaccinated at four months. At 10 months, the two booster shot groups (G1 and G2) had similar serological responses, while the calves that were treated with a single dose of vaccine at weaning (G3) had a response that was similar to that of the control group. The serological response of the calves was significantly inferior at several of the evaluation times when the field strain of the bacteria was used as a challenge antigen instead of the official MT strain. The serological response of calves that are vaccinated twice was found to be satisfactory, independent of the first injection being made at four or eight months of age. It was also concluded that it would be useful to include local bacterial strains in commercial vaccine production.

Diagnostic value of copper parameters to predict growth of suckling calves grazing native range in Argentina

A study was conducted to evaluate the predictive diagnostic value of different copper (Cu) parameters as indicators of average daily gain (ADG) in growing calves. The effects in calves of cow Cu supplementation in the last one-third gestation period were also evaluated. Five supplementation trials, with a total of 300 calves, were carried out. Two groups of 30 calves were randomly assigned to each trial, one group was parenterally supplemented (SG) and the other was not supplemented (NSG). Trials began when calves were three-month-old and ended at weaning time. At each sampling calves were weighed and blood was taken to determine Cu concentrations in plasma, Whole Blood (WB), Red Cells (RC) and Packed Cell Volume (PCV). Liver samples from six animals of each group were taken both at the beginning and at the end of the trial. In two trials the mothers of the SG received Cu supplementation at the last one- third gestation period. Four of the five trials exhibited low ADG in the NSGs. In these groups, plasma Cu concentration decreased rapidly before low ADG was detected, which occurred with values remaining below 25µg/dl. The decrease of RC Cu concentration was considerably slow. WB showed an intermediate position. PCV in the SGs was higher than in the NSGs in all trials. Cow supplementation was insufficient to generate a liver storage able to last after calves reached the 3 months of age. These data could be useful to predict the risk of low ADG in grazing calves.

Passive immunity transfer and serum constituents of crossbred calves

Passive immunity transfer (PIT) evaluation is an essential tool for the maintenance of healthy calves during the first months of life. Since lactation number and breed have been proven to influence immunoglobulin levels in colostrum, the aim of this study was to evaluate PIT from primiparous and multiparous Canchim cows to their calves. Blood samples were collected from the calves before colostrum intake and 1, 2, 7, 15 and 30 days thereafter, while colostrum samples from the cows were taken immediately after parturition. Activities of gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), and concentrations of total protein, albumin, globulins, immunoglobulin A (IgA), immunoglobulin G (IgG), total and ionized calcium, inorganic phosphorus, magnesium, sodium and potassium were evaluated in calves' serum and activities of GGT and ALP and concentrations of total protein, IgA and IgG were assessed in cow's colostrum whey. Immunoglobulins concentrations were evaluated by electrophoresis in polyacrylamide gels. Serum biochemistry evaluations revealed an increase in gamma-glutamyl transferase and alkaline phosphatase activities and in total protein, globulins, immunoglobulin A and immunoglobulin G levels in calves' serum after colostrum intake. Only total protein and light chain immunoglobulin G levels in colostrum whey were affected by the cows' lactation number. Phosphorus and magnesium levels in blood serum increased after colostrum intake, while sodium and potassium levels oscillated in the experimental period. PIT was influenced by the cows' lactation number but was efficient in both groups.

Thermal efficiency of individual shelters for girolando calves in brazilian semi-arid regions

ABSTRACT The objective of this research was to evaluate the thermal efficiency of roofs used on individual shelters during milk-feeding stage of Girolando calves. The research was conducted at a farm located in a dry region of Pernambuco state, Brazil. The experimental design was completely randomized, with 27 Holstein × Gir dairy crossbred calves housed in shelters with three roofing materials (fibre cement tile, recycled tile, and thatched roofs). The recycled tiles and thatched roofs provided reductions of 18.7 and 14.6% in radiant thermal load, respectively. Regardless the roofing material, all animals increased their respiratory rate to maintain thermal equilibrium.

Evidence of mixed persistent infections in calves born to cows challenged with a pool of bovine viral diarrhea virus isolates

Pregnant cows infected with noncytopathic (NCP) isolates of bovine viral diarrhea virus (BVDV) between days 40 and 120 days of gestation frequently deliver immunotolerant, persistently infected (PI) calves. We herein report the characterization of PI calves produced experimentally through inoculation of pregnant cows with a pool of Brazilian BVDV-1 (n=2) and BVDV-2 isolates (n=2) between days 60 and 90 of gestation. Two calves were born virus positive, lacked BVDV antibodies, but died 7 and 15 days after birth, respectively. Six other calves were born healthy, seronegative to BVDV, harbored and shed virus in secretions for up to 210 days. Analysis of the antigenic profile of viruses infecting these calves at birth and 30 days later with a panel of monoclonal antibodies indicated two patterns of infection. Whereas three calves apparently harbored only one isolate (either a BVDV-1 or BVDV-2), co-infection by two antigenically distinct challenge viruses was demonstrated in three PI calves. Moreover, testing the viruses obtained from the blood of PI calves by an RT-PCR able to differentiate between BVDV-1 and BVDV-2 confirmed the presence/persistence of two co-infecting viruses of different genotypes (BVDV-1 and BVDV-2) in these animals. These findings indicate that persistent infection of fetuses/calves - a well characterized consequence of fetal infection by BVDV - may be established concomitantly by more than one isolate, upon experimental inoculation. In this sense, mixed persistent infections with antigenically distinct isolates may help in understanding the immunological and molecular basis of BVDV immunotolerance and persistence.

Ethological activities, ruminal parameters and weight gain of calves supplemented with different amounts of sodium chloride

The daily weight gain, behavioral activities (grazing, ruminating and water consumption) and the number of rumen protozoa, pH, NH3, and the osmolarity of rumen fluid was evaluated for four groups of six calves HPB/Zebu submitted to daily intake of 15, 30, 60 and 90g of NaCl during 135 days (9th Jan. to 24th May 2008).Throughout the experimental period the calves were in perfect health condition and did not show any signs suggestive of chronic sodium poisoning. There was no significant difference in average daily gain of the calves as the intake of NaCl increased. No significant behavioral changes were observed in the activities of grazing and rumination. However, there was a noticeable change in the frequency of water consumption in the calves that ingested 90g/d of NaCl; they went more often to the trough and drank more water than the group that ingested only 15g sodium chloride/d. The osmolarity of ruminal liquid was higher in the group of calves fed 90g of NaCl/d. The pH, NH3 concentration and number of rumen protozoa was within the normal range.

Study on the growth promoting capacity of calf and fetal bovine serum for animal cells "in vitro" II: electrophoretic study and survey on the antiproteolytic activity of pools of calf and fetal bovine serum

Calf serum and fetal bovine serum present great variability as to its growth promoting efficiency (GPE). As supplement of culture media to cultivate cells of animal origin they stimulate the "in vitro" multiplication and maintain cell viability. When fourteen lots of calf sera of variable GPE had the total protein contents as well as the percentages of serum fractions determined, no significant differences that could possibly explain the variability of the GPE were observed. Evaluation of the antiproteolytic activity of nineteen lots of calf serum and eighteen serum lots of younger calves showed that the former exhibited lower antiproteolytic titers (1:40 to 1:80) than the latter (1:80 to 1:160). Twelve lots of fetal bovine serum studied in parallel, showed the highest concentration of antiproteolytic factors, with titers equal to 1:320. Sera of bovine origin, but not fetal sera, are usually heat-inactivated, what was demonstrated to be responsible for the decrease of the antiproteolytic activity of 75% of the lots tested. This could explain the inability of certain heat-inactivated sera in promoting multiplication of some cells "in vitro", as verified with primary monkey kidney cells. The results obtained in this study indicated the convenience of submiting each lot of serum to be introduced in cell culture to previous determination of its characteristics, such as growth promoting efficiency, antiproteolytic activity and also toxicity, absence of extraneous agents, etc., in order to minimize the possibility of using serum lots of questionable quality, thus preventing not only the loss of cell lines, but also undesirable and sometimes expensive delays.

Origin of samples of Cannabis sativa through insect fragments associated with compacted hemp drug in South America

Origin of samples of Cannabis sativa through insect fragments associated with compacted hemp drug in South America. Insects associated with a seizure of Cannabis sativa L. may indicate the origin of the illicit drug. Nevertheless, no work regarding this subject has been previously published for South America. In the present investigation, seven kilograms of vegetal material (C. sativa) were inspected for insect fragments. Three species were identified and used to test the origin of the seizure of cannabis plant material: Euschistus heros (Fabricius, 1794), Thyanta perditor (Fabricius, 1794) (Heteroptera, Pentatomidae), and Cephalotes pusillus (Klug, 1824) (Hymenoptera, Formicidae). These insect species restricted the geographic origin of the drug to the Neotropical region, and their distribution patterns showed an overlap of the State of Mato Grosso (Brazil), Argentina, and Paraguay. Based on this information, two of the three major C. sativa growing areas in South America were excluded: (1) the Colombian territory and (2) northeastern Brazil.

"Cara inchada" of cattle, an infectious, apparently soil antibiotics-dependant periodontitis in Brazil

The objective of this review on the investigation of "cara inchada" in cattle (CI), pursued over the last 30 years, was to elucidate the pathogenicity of the disease and come to proper conclusions on its etiology. CI has been widely considered to be of nutritional origin, caused primarily by mineral deficiency or imbalance. However, the disease consists of a rapidly progressive periodontitis, affecting the periodontal tissues at the level of the premolars and molars during the period of tooth eruption generally starting in young calves. The disease led to great economic losses for farmers in central-western Brazil, after the occupation of new land for cattle raising in the 1960s and 1970s. The lateral enlargement of the maxillary bones of affected calves gave the disease the popular name of "cara inchada", i.e., swollen or enlarged face. The enlargement was found to be due to a chronic ossifying periostitis resulting from the purulent alveolitis of CI. Black-pigmented non-saccharolytic Bacteroides melaninogenicus, always together with Actinomyces (Corynebacterium) pyogenes, were isolated in large numbers from the periodontal lesions. B. melaninogenicus could be isolated in small numbers also from the marginal gingiva of a few healthy calves maintained on CI-free farms. "In vitro"-assays showed that streptomycin and actinomycin, as well as the supernatants of cultivates of actinomycetes from soils of CI-prone farms, applied in subinhibitory concentrations to the bacteria tested, enhanced significantly (up to 10 times) the adherence of the black-pigmented B.melaninogenicus to epithelial cells of the bovine gingiva. The antibiotics are apparently produced in large quantities by the increased number of soil actinomycetes, including the genus Streptomyces, that develop when soil microflora are modified by cultivating virgin forest or "Cerrado" (tree-savanna) for the first time for cattle grazing. The epidemiology of CI now provides strong evidence that the ingestion with the forage of such antibiotics could possibly be an important determinant factor for the onset and development of this infectious periodontitis. The antibiotic enhanced adherence of B.melaninogenicus to the sulcus-epithelium of the marginal gingiva, is thought to allow it to colonize, form a plaque and become pathogenic. There is experimental evidence that this determinant factor for the development of the periodontitis is present also in the milk of the mothers of CI-diseased calves. It has been shown that the bacteria isolated from the periodontal CI-lesions produce enzymes and endotoxins capable of destroying the periodontal tissues. The epidemiology of CI, with its decline in incidence and its disappearance after several years, could be explained by the fact that the former equilibrium of the microflora of the once undisturbed virgin soil has been reached again and that the number of antibiotic producing actinomycetes has been anew reduced. By this reasoning and all the data available, CI should be considered as a multifactorial infectious disease, caused primarily by the anaerobic black-pigmented non-saccharolytic Bacteroides melaninogenicus, always together with the micro-anaerobic Actinomyces pyogenes. Accordingly, the onset and development of the infectious periodontitis is apparently determined by ingestion with the forage of subinhibitory concentrations of antibiotics produced in recently cultivated virgin soils. This hypothesis is supported by the recent observation of renewed outbreaks of CI-periodontitis in former CI-prone areas, following fresh cultivation after many years. The infectious nature of CI is confirmed by trials in which virginiamycin was used efficiently for the oral treatment of CI-diseased cattle. Previously it has been shown, that spiramycin and virginiamycin, used as additives in mineral supplements, prevented CI-periodontitis.

Comparative pathogenicity of bovine herpesvirus 1 (BHV-1) subtypes 1 (BHV-1.1) and 2a (BHV-1.2a)

The study aimed to examine the capacity of two bovine herpesvirus type 1 (BHV-1) isolates of different subtypes (EVI 123/96, BHV-1.1; SV265/98, BHV-1.2a) to induce respiratory disease in calves. These two isolates are representative of the BHV-1 subtypes prevalent in Brazil. Viral subtypes were confirmed by monoclonal antibody analysis and by restriction enzyme digestion of viral genomes. The viruses were inoculated intranasally into seven 3 months old calves (four with BHV-1.1, three with BHV-1.2a). Three other calves of identical age and condition were kept as uninfected controls. In both groups of infected calves, the clinical signs observed were consistent with typical infectious bovine rhinothracheitis (IBR), including pyrexia, apathy, anorexia, nasal and ocular mucopurulent discharges, erosions on the nasal mucosa, conjunctivitis, lachrymation, redness of nasal mucosa, dyspnoea, coughing, tracheal stridor and enlargement of retropharingeal, submandibular and cervical lymphnodes. No significant differences were observed between the clinical scores attributed to both groups. Virus shedding in nasal and ocular secretions were also similar, apart from a significant difference in nasal virus shedding on day 1 to 3 post-inoculation, which was higher for BHV-1.1 than for BHV-1.2a. Following corticosteroid induced reactivation of the latent infection, recrudescence of clinical signs was also observed, with no significant differences on both groups. It was concluded that both subtypes BHV-1.1 and BHV-1.2a were able to induce clinically undistinguishable respiratory disease in calves, either subsequent to a primary infection or following reactivation.

Experimental poisoning by Senecio brasiliensis in calves: quantitative and semi-quantitative study on changes in the hepatic extracellular matrix and sinusoidal cells

Extracellular matrix plays an important role in chronic hepatic lesions and has been studied in experimental intoxication models. However in cattle, studies on chronic disease have focused on the hepatocellular damage and extracellular matrix (ECM) changes are usually overlooked. There are no specific studies on the hepatic ECM in either normal or chronically damaged bovine liver. Thus an experimental model of hepatic toxicity model using Senecio brasiliensis poisoned calves was designed. Senecio brasiliensis contains pyrrolizidine alkaloids which cause either acute or chronic progressive dose dependent liver damage. Five calves were orally fed with 0.38g of dry leaves of S. brasiliensis/kg/day for 24 days. Liver needle biopsy specimens were obtained every 15 days for 60 days. Clinical signs of digestive complications appeared at 3rd week. One calf died on 45th day and four were evaluated up to 60th day. Biopsy samples were processed for routine light microscopy, immuno-histochemistry and transmission electron microscopy. From 30th day on progressive liver damage characterized by hepatocellular ballooning, necrosis, apoptosis and megalocytosis, centrilobular, pericellular and portal fibrosis were seen by light microscopy. Quantitative and semi-quantitative measurements of hepatic ECM components were performed before and after the onset of lesions. Morphometric analysis of total collagen and elastic fiber system was conducted. Total collagen and I and III collagen types progressively increased in throughout the liver of affected calves. Changes in location, amount and disposition of the elastic fiber system were also observed. Then numbers of Kupffer cells were significantly increased at 30th day and total numbers of sinusoidal cells were significantly increased at 45th and 60th days. Liver damage was progressive and irreversible even after the exposure to the plant was discontinued. Severe fibrotic lesions occurred mainly in portal tracts, followed by veno-occlusive and pericellular fibrosis. Collagen types I and III s were present in every normal and damaged liver, with predominance of type I. In affected calves the increase of total collagen and elastic fibers system paralleled the number of total sinusoidal cells.

A recombinant bovine herpesvirus 5 defective in thymidine kinase and glycoprotein E is attenuated and immunogenic for calves

Bovine herpesvirus 5 (BoHV-5) is an important pathogen of cattle in South America and efforts have been made to produce safer and more effective vaccines. In addition to afford protection, herpesvirus vaccines should allow serological differentiation of vaccinated from naturally, latently infected animals. We previously reported the construction and characterization in vitro of a double mutant BoHV-5 (BoHV-5gE/TK Δ) lacking the genes encoding thymidine kinase (tk) for attenuation, and glycoprotein E (gE) as the antigenic marker, as a vaccine candidate strain (Brum et al. 2010a). The present article reports an investigation on the attenuation and immunogenicity of this recombinant in calves. In a first experiment, 80 to 90-day-old seronegative calves (n=6) inoculated intranasally with the recombinant (titer of 10(7.5)TCID50) shed virus in low to moderate titers in nasal secretions for up to 6 days, yet did not develop any respiratory, systemic or neurological signs of infection. At day 30 post-infection (pi) all calves had BoHV-5 specific neutralizing (VN) antibodies in titers of 4 to 8 and were negative for anti-gE antibodies in a commercial ELISA test. Administration of dexamethasone (0.1mg/kg/day during 5 days) to four of these calves at day 42 pi did not result in virus shedding or increase in VN titers, indicating lack of viral reactivation. Secondly, a group of 8-month-old calves (n=9) vaccinated intramuscularly (IM) with the recombinant virus (10(7.5)TCID50/animal) did not shed virus in nasal secretions, remained healthy and developed VN titers from 2 to 8 at day 42 post-vaccination (pv), remaining negative for gE antibodies. Lastly, 21 calves (around 10 months old) maintained under field conditions were vaccinated IM with the recombinant virus (titer of 10(7.3)TCID50). All vaccinated animals developed VN titers from 2 to 16 at day 30 pv. A boost vaccination performed at day 240 pv resulted in a rapid and strong anamnestic antibody response, with VN titers reaching from 16 to 256 at day 14 post-booster. Again, serum samples remained negative for gE antibodies. Selected serum samples from vaccinated animals showed a broad VN activity against nine BoHV-5 and eight BoHV-1 field isolates. These results show that the recombinant virus is attenuated, immunogenic for calves and induces an antibody response differentiable from that induced by natural infection. Thus, the recombinant BoHV-5gE/TKΔ is an adequate candidate strain for a modified live vaccine.

Renal cortex copper concentration in acute copper poisoning in calves

The aim of this study was to estimate the diagnostic value of renal cortex copper (Cu) concentration in clinical cases of acute copper poisoning (ACP). A total of 97 calves that died due to subcutaneous copper administration were compiled in eleven farms. At least, one necropsy was conducted on each farm and samples for complementary analysis were taken. The degree of autolysis in each necropsy was evaluated. The cases appeared on extensive grazing calf breeding and intensive feedlot farms, in calves of 60 to 200 kg body weight. Mortality varied from 0.86 to 6.96 %, on the farms studied. The first succumbed calf was found on the farms between 6 and 72 hours after the susbcutaneous Cu administration. As discrepancies regarding the reference value arose, the local value (19.9 parts per million) was used, confirming the diagnosis of acute copper poisoning in 93% of the analyzed kidney samples. These results confirm the value of analysis of the cortical kidney Cu concentration for the diagnosis of acute copper poisoning.