Cryptosporidium muris in dairy cattle in Brazil

A total of 580 fecal samples from 30 cows and their calves from three dairy farms in S?o Paulo State, Brazil, was collected monthly over a period of 1 year (April 1994 to March 1995). A combination of water-ether centrifugal sedimentation technique followed by sucrose centrifugal flotation was used for neonatal samples and sucrose centrifugal flotation for the remainder of the samples. Cryptosporidium muris was found in calves from all farms, although the parasite was not detected in the dams. C. muris oocysts were excreted by 14 of the 30 calves, on at least one occasion during the year. Of the 307 calf fecal samples examined, 53 (17.3%) were positive for C. muris. The mean persistency of oocyst shedding in feces was 4 +/- 3 months. Sixty-four per cent of the positive calves excreted few oocysts, while 36% discharged many oocysts for a longer period (P < 0.05). Oocysts were first detected at the mean age of 3 +/- 1 months. The age of the positive calves ranged from 6 weeks to 14 months.     

Incidence and prevalence of lameness in dairy cattle

A survey was made of 37 dairy farms in Wirral, mid-Cheshire, mid-Somerset and Dyfed, Wales, to assess the incidence and prevalence of lameness in the cows between May 1989 and September 1991. The incidence was obtained from records made whenever a cow was examined for lameness or received preventive foot-trimming. The mean annual incidence was 54.6 new cases per 100 cows with a range from 10.7 to 170.1 and the mean values during summer and winter were 22.9 and 31.7, respectively. The prevalence of lameness was measured by regular visits at which locomotion was scored on a scale of 1 to 5, and the prevalence of lameness was calculated for each visit as the proportion of cows with scores of 3 or more. The mean annual prevalence over the whole period was 20.6 per cent with a range from 2.0 to 53.9 per cent for the 37 farms. The mean prevalences during summer and winter were 18.6 and 25.0 per cent, respectively. The prevalence measured at a single visit in midsummer or midwinter was significantly correlated with the mean prevalence over the whole corresponding period and may be useful as an assessment of the extent of lameness in a herd and the efficacy of control measures. There was evidence that training farmers to recognise early cases of lameness and request veterinary treatment resulted in a marked reduction in the duration of cases of lameness.     

The detection of oestrus in dairy cattle

A survey attempted to determine the extent to which cows are being inseminated when not in oestrus. The method used to check the farmers' diagnoses of oestrus was based on peripheral plasma progesterone concentrations analysed by radioimmunoassay. Of 141 cows examined in this way, a total of 30 (21-28 per cent) showed abnormalities of the progesterone levels. The fertility within this group was very poor with only two of the cows being known to have conceived to the service in question.     

Aetiology and Pathogenesis of abomasal displacement in dairy cattle

A clinical chemical survey is given of the complex of factors which are involved during development of clinically manifest hypotony or atony of the abomasum prior to abomasal displacemnts. The importance of a change in the acid-base balance of the animals is especially stressed as a predisposing factor. The further pathogenesis of abomasal displacement is supposed to follow different ways, according to the feeding and to prevailing periods of indigestion.     

The relationship between the number of spermatozoa inseminated and the reproductive efficiency of individual dairy bulls

The semen of 20 mature, evaluated bulls was split-sample diluted and contained 2.1 x 10(6) to 17.3 x 10(6) total spermatozoa per 0.25-ml French straw. The number of viable inseminated spermatozoa ranged from 1.1 x 10(6) to 11.8 x 10(6). Each bull had 2430 to 5330 first or second inseminations performed. The nonreturn rate at 56 d after AI was estimated for every dilution. The daily nonreturn rates to 180 d were used to estimate conception and calving rates at a given concentration. The relationship was determined between these estimations and the number of spermatozoa that were actually inseminated. The bulls differed significantly in their maximal nonreturn rate at high sperm numbers per AI and in the rate at which they approached this maximum. There was no correlation between the maximum nonreturn at high sperm numbers and the rate of approach, which implies that the ranking of the bulls for nonreturn rate 56 d after AI changes with the number of spermatozoa inseminated. Multiphasic analysis of reproductive efficiency revealed bull differences in estimated conception and calving rates. The estimated calving rate after conception was 82 to 90% and was independent of the number of spermatozoa that were inseminated. The sperm numbers needed to obtain 95% of the maximal conception rate ranged from 1 x 10(6) to 11 x 10(6).     

The seasonal variation of thermophilic campylobacters in beef cattle, dairy cattle and calves

The epidemiology of clinical cases of campylobacter in temperate climates shows a striking seasonality. In the search for a seasonal environmental reservoir changes in the carriage rate and population size of campylobacters in bovine hosts with time have been measured. Most probable number (MPN) methodology was used to enumerate thermophilic campylobacters in samples taken from the small intestines of beef cattle at slaughter and the fresh faeces of four dairy herds and new-born calves. Statistical analyses revealed significant evidence for seasonal periodicity in the data from dairy herds (P = 0.044). Not only was there a departure from constancy within a 12-month interval but these data revealed a true seasonality, that is, the same periodicity in numbers from one year to the next. Each herd had two peaks per year, in approximately spring and autumn. Peaks coincided in herds on neighbouring farms but those on farms in the north preceded those on farms in the south by 2 and 1 months, respectively (P = 0.0057). Intestinal carriage by beef cattle at slaughter was 89.4% (n = 360) with an average MPN campylobacters per gram fresh weight (MPN gfw-1) of 6.1 x 10(2). Average MPN gfw-1 in faeces from the dairy herds and calves were 69.9 (S.D. 3) and 3.3 x 10(4) (S.D. 1.7 x 10(2)). There was no evidence of seasonal periodicity in the size of the campylobacter population in beef cattle at slaughter. Calves were campylobacter free at birth but became colonized with a few days.     

Genetic analysis of clinical lameness in dairy cattle

Scores for clinical lameness from two separate studies were combined, and genetic parameters were estimated based on linear and threshold models. Cows were from 24 herds in Minnesota, Wisconsin, and Virginia. To evaluate clinical lameness, cows were observed walking and were assigned a score between 0 and 4 (where 0 = no observable problems to 4 = inability to walk). Data included 1624 records on 1342 cows. The models included fixed effects of herd visit, parity, and stage of lactation. Random effects were additive genetics, permanent environment to account for repeated records, and residual. Estimates of heritability were 0.10 and 0.22 from the linear and threshold models, respectively. The correlation between ETA from linear and threshold models based on all animals was 0.974. Deregressed ETA of sires and REML were used to estimate genetic correlations between clinical lameness and conformation traits. Among the type traits, foot angle, rear legs (rear view), and rump width had strongest associations with clinical lameness; absolute values for genetic correlations between these traits and clinical lameness were approximately 0.65. Low foot angle, hocking in, and wide rumps were associated with increased clinical lameness. Correlations with strength and body depth ranged from 0.20 to 0.43, indicating that heavier cows were more prone to clinical lameness.     

Generalized linear mixed models in dairy cattle breeding

Fitness and fertility traits of dairy cattle are of increasing importance and are often measured on a discrete scale. The development and application of generalized linear mixed models to the genetic analysis of these traits are reviewed. Because current genetic evaluation systems are predominantly based on animal models, the inferential challenges of highly parameterized generalized linear mixed models are discussed. Development and adoption of new methods for drawing appropriate inferences on dispersion parameters are essential. Recent hierarchical extensions have been proposed for generalized linear mixed models, allowing for complex dispersion patterns that accommodate heteroscedasticity and outlier robustness. Steady advances in available computing power have facilitated multiple-trait analyses involving continuous and discrete measures. Full Bayesian inference via the development of Markov Chain Monte Carlo methods will continue to allow even greater generality and dimensions in the genetic model.     

Adrenal cortex response to adrenocorticotropic hormone in dairy cattle

Adult dairy cows were treated with a range of doses (0.0125mg to 0.4mg) of synthetic ACTH1-24 and the plasma cortisol response was measured. Peak response was independent of dose. Higher doses of ACTH had a more prolonged effect such that the integrated response was dose dependent. Dose response curves were examined by regression analyses. Individual cows had a significant effect on y-axis intercept but not on the slope of the regression lines examined. A dose rate of 0.05mg ACTH iv was identified as a suitable dose rate for use in clinical assessment of adrenal cortex function, with 0, 50 and 120 min following ACTH being critical sampling times to identify the response.     

Short- and long-term production losses and repeatability of clinical mastitis in dairy cattle

Between 1985 and 1990, a study of 5313 lactations of 2477 Black and White cows was carried out. A stepwise least squares method was used to obtain unbiased estimates of milk, fat, and protein losses that were due to clinical mastitis and the carry-over effect from the previous lactation. Logistic regression was used to estimate the probability that a cow would have clinical mastitis in the next month. The effect of clinical mastitis on production within one lactation was estimated at 527 kg of milk (8.1%), 22.7 kg of fat (8.0%), and 13.7 kg of protein (6.2%) for > or = 3 cases of clinical quarters in the second lactation. One or 2 cases of clinical quarters in a lactation did not significantly affect the production in the next lactation. The negative carry-over effect of > or = 3 cases of clinical quarters was estimated at 381 kg of milk (5.9%), 23.7 kg of fat (8.4%), and 10.1 kg of protein (4.6%) up to and including mo 8 of the second lactation. The fat content in milk produced after the onset of mastitis decreased, and the protein content increased. The risk of clinical mastitis infection in the following month was influenced by month of lactation (a higher risk early in lactation), lactation number (risk increased with lactation number), production level (higher risk for high producing cows), number of clinical quarters in the previous lactation, number of clinical quarters in the previous months of the current lactation, and occurrence of clinical mastitis in the current month.     

A survey of dairy cattle worm control practices in southeast Brazil

A survey on the nematode control strategies utilized by dairy farmers in Southeastern Brazil, a region accounting for 46.4% of the national milk production, was conducted through interviews with farmers. To select the producers to be interviewed the region was split into 16 non-contiguous clusters, according to the level of milk production. A systematic sample was then selected in each of the clusters. The interview questionnaire consisted of one-way, multiple-choice and open-ended questions. Data collected were represented by numbers and digitized on a data base (Epi Info, version 5.01b) and analyzed. Out of the 89 farmers interviewed, 37.5% deworm their herd after clinical signs and 62.5% preventively. Generally, anthelmintics are applied from one to 12 times a year (average of 3.79 times a year) in all age categories of animals. Of the anthelmintics used in the last deworming, imidazothiazole was used exclusively by 17.1% of the farmers, benzimidazole by 9.8% and avermectin by 18.3%, while 55.8% used more than one anthelmintic class to deworm their animals. To choose the dosage, most farmers consult the product label (94.8%) and determine the volume to be applied, based on an estimate of the average body weight of each animal (62.9%). Improvements in the general appearance of the herd and weight gains of growing animals were observed by most farmers after deworming (87.3%). However, most of them (66.2%) recalled interrupting the use of some compound in the last few years, due to the detection of no improvement following treatment (32.7%), rising costs of the medication (28.6%), adverse reaction (8.2%), product not available at the time of purchase (4.1%) and decision to change the compound in use (10.2%). Most farmers (95.3%) intend to continue using the same control measures in the following year. Veterinarians play an important role in the farmer's choice to deworm their animals, as many seek advice from them. Therefore, programs aimed at technology transfer should include continuous updates on the subject, especially for veterinarians.     

Prediction of excretion of manure and nitrogen by Holstein dairy cattle

A compilation of N balance data (n = 1801) was partitioned into four groups to define the mean excretion of manure and N and to develop empirical equations to estimate these excretions from Holstein herds. Mean excretion of manure for cows that averaged 29 kg/d of milk production was 3 kg/d per 1000 kg of body weight (BW) more than the value for dairy cows reported by the American Society of Agricultural Engineers; N excretion was 0.09 kg/d per 1000 kg of BW higher than the value reported by the American Society of Agricultural Engineers. Mean excretion of manure and N for cows that averaged 14 kg/d of milk production and that for nonlactating cows were substantially lower than the values reported by the American Society of Agricultural Engineers. Growing and replacement cattle excreted 10 kg/d per 1000 kg of BW more manure and 0.11 kg/d per 1000 kg of BW more N than was reported by the American Society for Agricultural Engineers for beef cattle. Estimation of manure and N excretion was more accurate than mean values when using regression equations that included variables for milk production, concentration of crude protein and neutral detergent fiber in the diet, BW, days in milk, and days of pregnancy. Equations that contained intake variables did not significantly affect predictions of manure and N excretion, and the use of such equations is discouraged unless dry matter intake is measured and not estimated. Accurate estimates of excreta output could improve the planning of storage and handling systems for manure and the calculation of nutrient balances on dairy farms.     

Prevalence of Coxiella burnetii infection in dairy cattle with reproductive disorders

The prevalence of Coxiella burnetii infection in 207 cattle with reproductive disorders was studied by using an indirect immunofluorescence (IF) test, nested polymerase chain reaction (PCR) and isolation. IF antibodies to phase I and phase II antigens of C. burnetii were found in 122 (58.9%) and 125 (60.4%) of the sera, respectively, and PCR-positives were found in 8 (3.9%) of the sera and in 51 (24.6%) of the milk samples. In addition, C. burnetii was isolated from 51 (24.6%) of the milk samples by inoculating laboratory mice. The results indicate that the IF test plus PCR are useful in the diagnosis of bovine coxiellosis. It is difficult to deny that dairy cattle with reproductive disorders would be one of the important reservoirs of C. burnetii responsible for infection in both animal and human populations in Japan.     

Genetic and economic responses for within-family marker-assisted selection in dairy cattle breeding schemes

Marker-assisted selection schemes that utilize information about quantitative trait loci to preselect progeny test bulls within a family are the most practical application of quantitative trait loci results in the short-term. Technical difficulties exist for across-family marker-assisted selection using BLUP procedures. Two within-family marker-assisted selection schemes were evaluated genetically and economically using stochastic simulation for a locus that explained 5% of phenotypic variance. The genetic and economic impacts of variation in the number of offspring per bull-dam were evaluated. The top down marker-assisted selection scheme identifies sires that are heterozygous for the locus based on the granddaughter design and uses the quantitative trait locus information in the preselection of grandsons entering progeny testing. The bottom up marker-assisted selection scheme identifies sires heterozygous for a quantitative trait locus based on the daughter design and uses the information in the preselection of sons entering progeny testing. The top down scheme with one progeny per bull-dam reduced the rate of genetic gain compared with that from a breeding scheme that ignored knowledge of the quantitative trait locus. The top down scheme with reproductive performance of 3 or 40 progeny per bull-dam increased genetic gain by 1 to 2%. The bottom up scheme increased the rate of genetic gain by 1.5, 3.5, and 5% for 1, 3, and 40 progeny per bull-dam, respectively. When the top down scheme was used on the maternal path and the bottom up scheme on the paternal path, increases were 9% with 40 progeny per bull-dam. The use of reproductive technologies on bull-dams is imperative to prevent gains from marker-assisted selection being eroded by the loss in polygenic selection differential that results when more bull-dams are required to enable preselection of sons using markers.     

Use of bovine myeloperoxidase as an indicator of mastitis in dairy cattle

We compared the metabolic response to peripheral intravenous nutrition (peripheral IVN) with the response to central IVN when given after major gastrointestinal surgery. Eighteen consecutive patients who had undergone upper-gastrointestinal surgery were randomly assigned to receive either peripheral IVN (75% nonprotein calories supplied as lipid, n = 9) or central IVN (n = 9). Each group received 0.50 +/- 0.03 g N.kg-1 fat-free mass.day-1 (mean +/- SD with 100:1 kcal:g N (0.42 MJ:1 g N). Metabolic studies were undertaken before IVN (2nd postoperative day) and after 10 days of IVN. Negative nitrogen balance was reversed with both treatments (p < 0.001). The significant net efflux of individual amino acids from peripheral tissue before IVN was reduced toward balance, and there were no significant differences between the groups. The postoperative response of the plasma proteins (fibronectin, prealbumin, and transferrin) was similar in both groups. Peripheral IVN decreased postoperative peripheral net uptake of glucose to a net balance. Central IVN resulted in decreased free fatty acid, glycerol, and beta-hydroxybutyrate concentration with increases in plasma insulin concentration and the net uptake of glucose and pyruvate in peripheral tissue. The effect of intravenous nutrition on the metabolic response to major surgery was similar when nonprotein calories were supplied wholly as glucose requiring a central delivery system or when 75% of nonprotein calories were given as lipid when a peripheral delivery system was used. This study supports the development of peripheral IVN feeding systems.     

Review: effect of protein nutrition on ovarian and uterine physiology in dairy cattle

Milk production and dry matter intake of dairy cows are stimulated in response to increased intake of dietary protein, but, unfortunately, decreased fertility is often associated with this nutritional strategy. Ruminally degradable protein or ruminally undegradable protein in excess of requirement can contribute to reduced fertility in lactating cows. Dietary protein nutrition or utilization and the associated effects on ovarian or uterine physiology have been monitored with urea nitrogen in plasma or milk; concentrations above 19 mg/dl have been associated with altered uterine pH and reduced fertility in dairy cows. The uterine pH changed dynamically and inversely with plasma urea nitrogen, signaling possible changes in the uterine milieu. Mechanisms for reduced fertility include exacerbation of negative energy balance and reduced plasma progesterone concentrations when cows were fed rations that were high in ruminally degradable intake protein. Alternatively, changes in uterine secretions that are associated with high protein intake and elevated plasma urea nitrogen might be detrimental to embryos. Bovine endometrial cells in culture respond directly to increasing urea concentrations with alteration in pH gradient but respond most notably with increased secretion of prostaglandin F2 alpha (PGF2 alpha). Increased uterine luminal PGF2 alpha interferes with embryo development and survival in cows, thus providing a plausible link between elevated plasma urea nitrogen concentrations and decreased fertility. Poor fertility in high producing dairy cows reflects the combined effects of a uterine environment that is dependent on progesterone and rendered suboptimum by the antecedent effects of negative energy balance or postpartum health problems and that is further compromised by the effects of urea resulting from intake of high dietary protein.