Estimates of phenotypic and genetic parameters for birth weight of Brown Swiss calves in Turkey using an animal model

A study was conducted to assess the influence of genetic and environmental factors on Brown Swiss calf birth weight, and to estimate variance components, genetic parameters, and breeding values. Data were collected on 1,761 Brown Swiss calves born from 1990 to 2005 in the Konuklar State Farm in Turkey. Mean birth weight for all calves was 39.3 ± 0.09 kg. Least squares mean birth weights for male and female Brown Swiss calves were 40.3 ± 0.02 and 39.0 ± 0.02 kg, respectively. Variance components, genetic parameters, and breeding values for birth weight in Brown Swiss calves were estimated by restricted error maximum likelihood (REML)-best linear unbiased prediction(BLUP) procedures using an MTDFREML (multiple trait derivative free restricted maximum likelihood) program employing an animal model. Direct heritability (h(d)(2)), maternal heritability (h(m)(2)), total heritability (h(T)(2)), r(am) and c(am) estimates were 0.12, 0.09, 0.23, -0.58, and -0.06, respectively. The estimated maternal permanent environmental variance expressed as a proportion of the phenotypic variance (c(2)) was 0.05. Breeding values were estimated for the trait and used to evaluate genetic trends across the time period investigated. The genetic trend linear regression was not different from zero. No genetic trend for birth weight was expected, since there had been no direct selection pressure on the trait. Absence of a trend confirms that there was no change due to selection pressure on correlated traits. Genetic and environmental parameter estimates were similar to literature values indicating that effective selection methods used in more developed improvement programs would be effective in Turkey as well.

Implications of proposed changes in bulk tank somatic cell count regulations

Several changes in bulk tank SCC (BTSCC) regulations were proposed at the 1998 annual meeting of the National Conference of Interstate Milk Shippers (NCIMS) by the National Mastitis Council and other proponents. Proposals included 1) using a geometric mean BTSCC in place of the arithmetic mean, reducing the current limit for BTSCC from 750,000 to 400,000, and modifying current regulatory protocols. The purpose of this research was to evaluate possible impacts of proposed changes upon producers in warm climates. Data were monthly BTSCC values, provided by state regulatory agencies in West Texas, Louisiana, and Mississippi. Fifty producers from each state were selected by lot, and all 1998 monthly records were included (n = 1602). Computer simulation was used to compare regulatory actions that would have resulted under current and proposed regulations. Possible regulatory actions were 1) notification of noncompliance and 2) suspension of permits to sell milk. At the 750,000 BTSCC limit, both programs resulted in 41 regulatory actions, but the proposed program had a higher rate of suspensions to notices. A twofold increase in regulatory actions per 100,000 incremental decrease in BTSCC limit below 750,000 resulted under both programs. Actual results could be lower due to the assumption that no management adjustments were made by producers in response to changes in regulations. However, the magnitude of increased actions against producers indicated that lowering limits quickly could be disruptive if producers failed to adjust management quickly and effectively to comply with lower limits.

Rapid assessment of the bacteriological quality of raw milk using ATP bioluminescence

Research was conducted to assess the practical use of an ATP bioluminescence assay to evaluate the bacteriological quality of raw milk. Filtration was used to precondition samples before ATP determination, which was measured in relative light units (RLUs). The Lumac ATP bioluminescence assay results were compared with standard plate counts (SPCs) of samples to estimate the microbial load for 246 raw milk samples that were split and either tested immediately or subjected to two preliminary incubation temperatures, 12.8 and 15.6 degrees C, for 18 h. Linear regression analysis procedures were used to analyze the data. Preincubation treatments were analyzed separately. For all treatments, linear regression coefficients were significantly different from zero (P < 0.01). The R2 values calculated using log10-transformed SPC and log10-transformed RLUs for samples tested immediately and samples preliminarily incubated at 12.8 and 15.6 degrees C were 0.58, 0.78, and 0.80, respectively. The R2 for all samples combined was 0.78. Differences in regressions among treatments were tested using a multiple slope and intercept model. Treatment intercepts and slopes were significantly different (P < 0.01). A linear regression equation was used to predict SPC from ATP values. Comparison of predicted values with actual SPCs indicated that ATP could be useful in predicting SPC in raw milk.

Efficacies of chlorine dioxide and lodophor teat dips during experimental challenge with Staphylococcus aureus and Streptococcus agalactiae

We tested two postmilking teat dips for efficacy against Staphylococcus aureus and Streptococcus agalactiae using experimental challenge procedures recommended by the National Mastitis Council. The chlorine dioxide teat dip that contained 0.7% sodium chlorite reduced the number of new intramammary infections (IMI) caused by Staph. aureus by 86.6% and reduced new IMI caused by Strep. agalactiae by 88.4%. The 0.5% iodophor teat dip reduced the number of new IMI caused by Staph. aureus by 92.9% and reduced the number of new IMI caused by Strep. agalactiae by 43.4%. Teat skin and teat end conditions were evaluated before and after the study, and no deleterious effects were noted among dipped quarters compared with undipped control quarters for either teat dip.

Performance and metabolic responses of young dairy calves fed diets supplemented with chromium tripicolinate

Forty-two Holstein calves were used to study performance and metabolic responses when milk replacer and then postweaning starter were supplemented with 1 ppm of Cr as Cr-tripicolinate. From birth through 8 wk of age, supplemental Cr tended to improve the growth performance of bull calves but not of heifer calves. Starter intake and feed efficiency were not affected by supplemental Cr. From 1 to 5 wk of age, plasma cortisol concentrations sampled just prior to feeding decreased, and concentrations of insulin-like growth factor-I increased. All calves appeared to become less sensitive to insulin as they aged. From 1 to 5 wk of age, plasma glucose and insulin concentrations gradually diverged for all calves; glucose concentrations decreased, and insulin concentrations increased. In addition, glucose clearance rate, measured by i.v. glucose tolerance tests, was more rapid when calves were 2 wk of age than when calves were 8 wk of age. The glucose clearance rate was greater in heifer calves than in bull calves but was not affected by supplemental Cr. Entry of plasma glucose following an i.v. propionate load was also greater in heifer calves than in bull calves but was not affected by supplemental Cr. Plasma nonesterified fatty acids were lower in calves fed milk replacer or starter supplemented with Cr than in control calves, although this effect diminished as calves aged. This finding was considered to be indirect evidence of enhanced insulin sensitivity in calves fed milk replacer or starter supplemented with Cr. Overall, data suggested that supplemental Cr-tripicolinate had minor effects on the metabolism and growth performance of conventionally managed dairy calves. The most notable effects occurred during the initial few weeks of life.

Germicidal activity of a chlorous acid-chlorine dioxide teat dip and a sodium chlorite teat dip during experimental challenge with Staphylococcus aureus and Streptococcus agalactiae

Three postmilking teat dips were tested for efficacy against Staphylococcus aureus and Streptococcus agalactiae in two separate studies using experimental challenge procedures that were recommended by the National Mastitis Council. The first study evaluated a barrier teat dip product containing chlorous acid-chlorine dioxide as the germicidal agent, and the second study evaluated a sodium chlorite product with a barrier component as well as a sodium chlorite product without a barrier component. The chlorous acid-chlorine dioxide teat dip reduced new intramammary infections (IMI) caused by Staph. aureus by 91.5% and reduced new IMI caused by Strep. agalactiae by 71.7%. The barrier dip containing sodium chlorite reduced new IMI caused by Staph. aureus and Strep. agalactiae by 41.0 and 0%, respectively. The nonbarrier dip containing sodium chlorite reduced new IMI caused by Staph. aureus by 65.6% and reduced new IMI caused by Strep. agalactiae by 39.1%. Teat skin and teat end conditions were evaluated before and after the second study; no deleterious effects among dipped quarters compared with control quarters were noted for the two sodium chlorite products.

Sex ratio variation between ejaculates within sire evaluated by polymerase chain reaction, calving, and farrowing records

Ejaculates from sires were examined by polymerase chain reaction to determine percentage of sperm bearing the Y chromosome. Results were verified by examining the percentage of male calves per ejaculate used in artificial insemination (AI) and the percentage of male piglets per litter from a controlled mating program. Spermatozoal DNA was amplified by polymerase chain reaction with specific primers for the Y chromosome. Image analysis measured the fluorescent intensity of the 194-bp band. Ejaculates were compared with a pooled standard of spermatozoal DNA equated to a 50% Y-bearing sperm ejaculate. Calving data were obtained from information collected for the National Association of Animal Breeders for dystocia evaluation of cows bred to AI bulls. Breeding data were obtained from AI technician receipts. Calving and breeding data were merged on cow, sire, calving date, and breeding date. The percentage of males were calculated per sire, ejaculate, and herd combination. Farrowing data were evaluated for the percentage of male piglets per litter. Ejaculates within bulls contributed to variation (24 +/- 9.8% to 84 +/- 9.8%) in the percentage of sperm bearing the Y chromosome. Ejaculates from the same bull contributed to variation in the percentage of male calves (16.1 to 72.3%). Ejaculates from the same boar contributed to variation in the percentage of male piglets that ranged from 7.8 to 94.7%. These percentages and the results obtained by polymerase chain reaction analysis of ejaculates suggested that spermatozoa bearing X and Y chromosomes were unequally represented in ejaculates. The use of ejaculates screened by polymerase chain reaction could enhance production of the desired sex of calf.

Efficacies of teat germicides containing 0.5% chlorhexidine and 1% iodine during experimental challenge with Staphylococcus aureus and Streptococcus agalactiae

Two germicides, one containing 0.5% chlorhexidine and one containing 1% iodine, were tested for efficacy against new intramammary infections (IMI) caused by Staphylococcus aureus and Streptococcus agalactiae. The model for the experimental challenge in the trials that were designed to test the efficacy of the two postmilking teat dips was recommended by the National Mastitis Council. The 0.5% chlorhexidine product reduced the number of new IMI caused by Staph. aureus by 73.2% and reduced the number of new IMI caused by Strep. agalactiae by 53.9%. The 1% iodine product reduced the number of new IMI caused by Staph. aureus by 75.6% and reduced the number of new IMI caused by Strep. agalactiae by 53.5%. In both trials, the incidence of clinical mastitis was also reduced in dipped quarters compared with control quarters. Use of the two teat dips over the trial periods had no effect on the condition of teat skin or teat ends.

Chromosome and sperm size of Holsteins with and without bovine leukocyte adhesion deficiency

The objective was to evaluate bull differences in chromosomal and spermatozoal areas related to the occurrence of the bovine leukocyte adhesion deficiency syndrome. Lymphocyte chromosomes from 30 Holstein bulls and 2 Holstein heifers were measured using image analysis and computer-enhanced video-microscopy. Spermatozoal head areas from 29 of the 30 bulls were measured. Autosomal rank was based on decreasing area. Average total autosomal areas were not the same across bulls. One group of bulls had significantly smaller average chromosomal areas than the others; this group carried bovine leukocyte adhesion deficiency syndrome. Area measures of spermatozoal heads showed that bulls with bovine leukocyte adhesion deficiency syndrome had significantly larger head areas than normal bulls. Lymphocyte chromosomes from 3 cattle that were homozygous for bovine leukocyte adhesion deficiency syndrome were significantly smaller than chromosomes from syndrome heterozygotes. Carrier identification was improved by the use of autosomal and sperm area measurements in addition to pedigree evaluation.

Distribution of clinical mastitis among quarters of the bovine udder

Clinical mastitis episodes occurring from 1962 through 1991 in the Louisiana State University Dairy Research Herd were studied to determine the distribution of clinical mastitis among quarters of the udder. Data were detailed records of all mastitis episodes that occurred during 1630 Holstein lactations. Incidence of episodes, categorized according to which quarters within a cow were clinical for a given case, were compared with mathematical expectations based upon the assumption that quarters were independent. Results indicated that quarters within a cow were more alike with respect to clinical mastitis than would be expected if quarters were independent. More episodes occurred in which either no quarters or all four quarters were clinical. Deviation of observed frequencies from expectation could have resulted from generalized cow differences, such as cow milk yield, immune competency, mammary type characteristics, and general health. Front quarters had less clinical mastitis than rear quarters when all episodes were considered. No difference was observed in incidence between front and rear quarters when only first episodes in first lactations were considered. No difference was observed between incidence in left and right quarters. Diagonal pairs occurred less often than expected and at about half the frequency of other pairs. Dependence between quarters should be taken into consideration when experiments are designed and analyzed.

Feeding practices and income over feed cost on pasture-oriented dairy farms in Louisiana

Monthly summary reports (n = 15,568) of Holstein herds enrolled in the Louisiana DHIA program from February 1984 through April 1990 were analyzed using multiple regression techniques to determine the relationships between feeding practices and income over feed cost on predominantly pasture-oriented dairy farms. Income over feed cost increased as silage and pasture quality score increased and decreased as hay and concentrate increased. Milk yield increased as silage and concentrate increased. Increased hay was associated with lower milk yield, but the overall difference was small. Comparison of feeding practices overall with the top 10% of herds based on income over feed cost indicated that most dairy farmers were not adjusting amount of concentrate to nutritional needs. Additional silage fed during late summer and fall, when permanent pastures were at lowest quality and winter pastures were not productive, improved income over feed cost and herd reproductive performance. Better utilization of concentrate by adjustment of amounts fed for milk yield, stage of lactation, and forage component of ration would increase milk yield and income over feed cost. Increased utilization of silage is suggested for better financial and productive performance of the pasture-oriented dairy farms studied.

Cytologic responses of Staphylococcus aureus-infected mammary glands of heifers to interferon gamma and interleukin-2 treatment

Cytologic and bacteriologic responses, and changes in cytokine activity were evaluated in secretions of Staphylococcus aureus-infected mammary glands after treatment of heifers with recombinant bovine interferon gamma (rbIFN gamma) or interleukin 2 (rbIL-2). Two groups of 4 heifers each, experimentally infected with 10(7) colony-forming units (CFU) of S aureus, were injected in 2 quarters via the teat canal, with 10(5) U of rbIFN gamma (trial 1) or 7.5 x 10(5) U of rbIL-2 (trial 2) 2 weeks after experimentally induced infection; control quarters received phosphate-buffered saline solution. Mammary secretion samples were taken on days 0, 1, 2, 3, 4, 7, and 14 after cytokine infusion. Secretions were diluted 1:10 and used to perform somatic cell counts (SCC), differential cell counts, and CFU enumerations, and to determine the number of leukocytes expressing major histocompatibility complex class-II (MHC II) antigens. In addition, mammary secretion samples taken on days 0, 1, and 2 were processed to obtain skimmed milk for evaluation of rbIFN gamma- and rbIL-2-like activities. Treatment with rbIFN gamma did not influence SCC, or differential or bacteria counts, or the number of leukocytes expressing MHC II antigens. However, rbIL-2 stimulated leukocytosis, which may have reduced bacteria counts early in the trial; treatment with this cytokine also increased the neutrophil, macrophage, lymphocyte, and eosinophil counts in secretions. Similarly, numbers of MHC II-positive leukocytes were greater in rbIL-2-treated quarters vs controls. Compared with day 0, IFN-gamma-like activity was increased on only day 1 in both trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Histologic response of the heifer mammary gland to intramammary infusion of interleukin-2 or interferon-gamma

The histologic and cytologic responses of heifer mammary glands infected with Staphylococcus aureus were studied after infusion of interleukin-2 or interferon-gamma. Two groups of 4 heifers each, which were infected experimentally with S. aureus in all 4 mammary quarters, were infused in diagonal quarters with 7.5 x 10(5) units of interleukin-2 or 10(5) units of interferon-gamma; remaining quarters received PBS. Heifers in both trials were slaughtered 14 d after cytokine infusion, and mammary tissues were collected for histological examination. Uninfected quarters from 2 additional heifers were left untreated to compare infected with uninfected tissues for both trials. Morphologic evaluation and leukocyte infiltration scores were performed on tissue sections stained with hematoxylin and eosin, and plasma cells were quantified on sections stained with immunoperoxidase. Infected quarters had lower percentages of alveolar epithelial and luminal areas and higher percentages of stromal area than did uninfected quarters in the interleukin-2 trial, but no differences were observed between infected quarters that had been treated with PBS or interleukin-2. Likewise, interferon-gamma treatment had no effect on mammary parenchymal components in the infected quarters. Interleukin-2 treatment significantly elevated leukocytosis into the mammary gland parenchyma compared with infected quarters treated with PBS and uninfected quarters. Among the leukocyte types evaluated, eosinophilic infiltration was elevated in interleukin-2 quarters over that of PBS controls. In both trials, concentrations of plasma cells bearing Ig were elevated in infected versus uninfected quarters. Plasma cell concentrations also were higher in cytokine than PBS controls, especially in interleukin-2 quarters. Results suggested that neither cytokine influenced the histology of infected mammary tissues, but both interleukin-2 and interferon-gamma increased, although insignificantly, the prevalence of all isotypes of plasma cells bearing Ig, suggesting enhancement of the local immune response to IMI.

Evaluation of a gel teat cleaning and sanitizing compound for premilking hygiene

A gel was developed and tested for cleaning and sanitizing cows teats for milking. Thirty lactating Holstein cows were divided into three groups of 10 each and assigned to three premilking hygiene treatments for 10 wk as follows: 1) cleaning teats with gel, allowing 30 s of contact time, and wiping residual gel off with paper towel; 2) washing teats with water and drying them with paper towel; 3) washing teats with water, drying with paper towel, predipping with .5% iodophor solution, allowing 30 s of contact time, and drying with paper towel. Individual cow composite milk and teat end swab samples were collected. The gel and predip treatments resulted in less bacterial contamination of milk and teat ends. The gel treatment had an advantage over wash and predip treatments in lower SCC and reduced mastitis. Parlor throughput was greatest for gel and wash treatments. The wash treatment group had highest SCC, bacteria in milk and on teat ends, and mastitis. Milk iodine content was low and similar for the three treatments. Daily milk production and fat and protein percentages were not affected by treatments. The gel treatment was effective, efficient, and provided good hygiene.

Early pregnancy associated thrombocytopenia as an initial response to pregnancy in cattle

This study was conducted to determine if early pregnancy-associated thrombocytopenia exists in cattle as has been demonstrated in mice and in humans. Three experiments were designed to compare peripheral platelet counts in pregnant versus nonpregnant animals. In Experiment 1 heifers (n = 25) were artificially inseminated 12 h after the onset of estrus. Peripheral platelet counts in 19 pregnant versus 6 nonpregnant heifers did not reveal any significant differences between groups after insemination. In Experiment 2 embryos were collected nonsurgically from superovulated cows (n =18) on Days 6 to 7 after estrus. Platelet counts were monitored every 12 h after the first insemination until 60 h after the second insemination. Platelet counts and the number of embryos collected nonsurgically from these superovulated donors did not show any significant correlations (P>0.05). Ten recipient heifers synchronized to donor animals received either an unfertilized ovum or a good quality embryo via nonsurgical transfer into the uterus. There were no significant reductions in platelet counts after transfer. In Experiment 3 platelet counts were monitored daily in four pregnant and five nonpregnant recipient heifers between Day 0 and Day 30 after embryo transfer on Day 8 of the cycle. The platelet counts did not reveal any significant differences between the pregnant and nonpregnant groups throughout Days 0 to 30. These results indicate that early pregnancy-associated thrombocytopenia cannot be demonstrated in cattle. Peripheral platelet counts cannot be used as an indicator of early pregnancy in cattle.

Efficacy of intramammary treatment in unbred and primigravid dairy heifers

A total of 73 breeding-age and primigravid Jersey heifers in 4 herds was randomly allotted to treatment and control groups according to expected calving date. Thirty-five heifers were injected intramammarily with a nonlactating cow product containing penicillin/streptomycin. Thirty-eight heifers served as untreated controls. Of the 35 treated heifers, 34 (97.1%) were infected at time of treatment. In the untreated control group, all 38 heifers (100%) were infected at treatment time. At parturition, prevalence of intramammary infection in treated heifers decreased to 40%, whereas in the control group, prevalence remained about the same (97.4% of heifers). Prevalence of Staphylococcus aureus mastitis in treated heifers was reduced from 17.1% to 2.9% after treatment. In the control group, prevalence of S aureus mastitis decreased from 26.3% to 15.8%. Heifers treated during the second trimester of pregnancy had the greatest reduction in prevalence of mastitis and in somatic cell count at parturition, compared with controls. Findings indicated that intramammary treatment during pregnancy in primigravid heifers was effective in reducing prevalence of mastitis and somatic cell counts at parturition.

Videomicroscopic comparison of bull sperm and leukocyte chromosome areas as related to gender

Chromosomal areas from metaphase spreads of male bovine leukocytes were digitized and sex chromosomes identified using videomicroscopy. Autosomal areas were ranked in descending order within a cell and assigned to two categories based on alternating rank. X and Y chromosome areas were assigned to respective categories. Areas were divided by 4 to make their sum equivalent to sperm DNA content. Data were analyzed before and after inclusion of sex chromosomal areas. Before X and Y inclusion, rank contributed to difference in chromosomal areas. Rank by category interaction and category effects did not contribute to area variation. After X and Y inclusion, area variation was due to rank by category interaction, rank, and category. Differences between sums of chromosomal areas across categories was 3.57%. Head areas of morphologically normal sperm with intact acrosomes were digitized using the same optics as chromosomal areas. Sum of corrected chromosomal areas per category was used in discriminant analysis to assign sperm head areas to two categories with .5 prior probabilities. Assignment resulted in 1037 sperm in one category and 1177 in the other. Difference between largest sperm head area classes across categories was 3.2%. Discrimination of sperm head areas, based on sum of chromosomal area and measured with computerized videomicroscopy, may be used to evaluate sex of bovine spermatozoa.

Histopathology of staphylococcal mastitis in unbred dairy heifers

Histologic observations of mammary tissue samples from unbred heifers revealed that secretory parenchyma from uninfected quarters was undeveloped, exhibiting small alveoli with a limited luminal area and a large interalveolar stromal area. Tissues from quarters infected with Staphylococcus aureus were less developed, exhibiting less alveolar epithelial and luminal areas and more interalveolar stroma compared with tissues from uninfected quarters. Such quarters also demonstrated minimal secretory activity. Macroscopic and microscopic abscesses were observed in one quarter with S. aureus intramammary infection. Staphylococcus aureus-infected quarters showed greater leukocyte infiltration into mammary parenchymal components and cistern lining compared with uninfected quarters. Quarters infected with non-aureus staphylococci also exhibited greater leukocyte infiltration and greater percentages of interalveolar stroma compared with uninfected controls. Results demonstrated that presence of infection increased leukocytosis into the mammary gland and reduced secretory activity in heifers, suggesting a deleterious effect on future milk production.

An efficient procedure for manual platelet counting

Blood samples were collected by jugular venipuncture from 15 dairy heifers and the blood platelets were counted by manual methods. The platelets were found to be uniformly distributed across the rows, columns and sides of a Neubauer haemocytometer, and it was shown that counting any 10 squares on either side of the haemocytometer and multiplying by a constant factor would accurately predict the total platelet count. This procedure would greatly reduce the time required to count large numbers of platelets per sample, and reduce errors due to the fatigue associated with counting large numbers of samples.

Effect of feeding gossypol in cottonseed meal on growth, semen quality, and spermatogenesis of yearling Holstein bulls

Yearling Holstein bulls were fed a corn silage ration supplemented with either cottonseed meal with gossypol or soybean meal in two trials to evaluate the effect of feeding gossypol on reproductive characteristics. In Trial 1, roughage to concentrate ratio was 88:12 and was fed for 60 d. In Trial 2, roughage to concentrate ratio was 50:50 and was fed for 42 d. Cottonseed meal concentrate had 3.03 g total gossypol/kg DM. Cottonseed meal concentrate was fed to provide 6 and 30 mg total gossypol/kg BW per d in Trials 1 and 2. Ejaculates were collected twice weekly via artificial vagina and critiqued for quantity and quality before and after thawing and after postthaw incubation. Leptotene spermatocytes to Sertoli cell ratio in stage 1 tubules was used to evaluate spermatogenesis. Growth characteristics and tissue total gossypol concentrations were also evaluated. No gossypol was found in plasma taken before, during, or after Trial 1 or from body organs or plasma taken during or after Trial 2. No signs of gossypol toxicity were observed, and growth characteristics were similar on both rations. Gossypol in cottonseed meal fed at low to moderate concentrations was not deleterious to seminal quantity or quality, and spermatogenesis was unaffected by treatment.

Effect of disc moistening method on Bacillus stearothermophilus disc assay zone diameters

Effect of disc moistening method on the Bacillus stearothermophilus disc assay zone size was studied. Pasteurized homogenized milk was subdivided and three levels of US Pharmacopeial reference standard penicillin G were added. Disc assay filter paper discs were moistened using the standard capillary action procedure and a method incorporating the use of a 90-microliters micropipetter. Amount of milk sample absorbed by discs prepared by the capillary action method was correlated with disc mass. Variation in amount of milk absorbed by discs was significantly greater when discs were prepared by capillary action. Zone diameter means and standard errors across all penicillin G concentrations tested were not significantly different for the two methods. The 90-microliters micropipetter method is recommended as an alternative to the capillary action method.

Effect of plate preincubation on Bacillus stearothermophilus disc assay zone diameters

Effect of plate preincubation on the Bacillus stearothermophilus disc assay zone size was studied. Each of three raw milk samples were subdivided and treated with five levels of US Pharmacopeial reference standard penicillin G. Freshly prepared, 2.5- and 5-d old seeded disc assay culture plates were preincubated at 64 degrees C for 0 (control), 20, 40, 60, 80, 100, and 120 min prior to placement of discs on the medium surface. Plate age did not have a significant effect on the size of the zone diameter. Following 20 and 40 min of plate preincubation, zone diameters were in some, but not all, cases significantly different from the control. Plate preincubation of 60 min or greater always significantly decreased zone diameter. Routine preincubation of B. stearothermophilus plates is not recommended. In situations where time is a critical factor, plates should be preincubated no longer than 40 min.

Use of linear semen quality score for classification and decision making in evaluation of individual ejaculates of Holstein bulls

Four hundred seven ejaculates from 15 Holstein bulls collected from December 1984 to June 1985 were evaluated postthaw for viability characteristics (percent progressive motility at 0 h and after 3 h at 37 degrees C incubation, percent intact acrosomal membrane after 3 h at 37 degrees C incubation) and abnormal morphological characteristics [percent head (primary), midpiece, and tail (secondary) abnormalities]. Weighting coefficients for combining viability and abnormality characteristics were generated from between-bull and within-bull variance and covariance matrices. Two hundred ninety-eight additional ejaculates collected from July 1985 to February 1986 were added. Linear quality scores for 705 ejaculates (24 bulls) were the sum of the product of each quality characteristic and weighting coefficients. Univariate analysis yielded significant bull effects for viability and abnormality characteristics and linear quality score. Significant correlations existed between all seminal quality characteristics except primary and secondary abnormalities. A t test with preassigned critical value was used to evaluate each ejaculate to determine rejection from the population. Percent of ejaculates rejected was lower when linear quality score was used than when five independent tests were used. Use of linear quality score to critique semen based on each ejaculate's innate quality could compensate for the loss of bull fertility estimates from declining number of technician-based AI programs.

Effect of serum sources and colostral whey on bovine semen quality and spermatozoa immunoglobulin G immunofluorescence

Heifer, bull, fetal calf sera, and colostral whey were used to evaluate the influence of protein concentrations on percent progressive motility, head-to-head agglutination, acrosomal integrity, and immunoglobulin G immunofluorescence of bovine spermatozoa using ejaculates from 10 bulls. In the first experiment, 10% (vol/vol) addition of undiluted colostral whey resulted in the highest head-to-head agglutination, acrosomal integrity, and immunoglobulin G immunofluorescence. Ten percent (vol/vol) addition of whey diluted to a protein concentration equivalent to fetal calf serum produced significantly lower agglutination, acrosomal integrity, and immunoglobulin G immunofluorescence. Fetal calf serum was unable to produce agglutination and immunoglobulin G immunofluorescence of bovine spermatozoa. Heifer and bull sera produced similar responses for all seminal measurements. In Experiment 2, unheated whey and heifer serum resulted in higher response for all variables than heat inactivated whey and heifer serum. Whey treatment produced greater spermatozoal motility, agglutination, acrosomal integrity; and immunoglobulin G immunofluorescence than treatment with heifer serum. Spermatozoal immunofluorescence indicated antibodies in normal whey, bull, and heifer serum bound to spermatozoal membranes at the acrosomal region. Colostral whey was an effective source of agglutinin factor. Normal unheated whey and heifer serum did not cause sperm damage or immobilization.

Environmental and genetic sources of variation for seminal quality in mature Holstein bulls

Various environmental and genetic factors that influence seminal quality were evaluated for 149 Holstein bulls used extensively in nine artificial insemination organizations (studs). These bulls were sons of 16 sires. Seminal quality was measured by percent progressive motility immediately postthaw and after incubation at 3 h, 37 degrees C, percent intact acrosomal membrane after incubation at 3 h 37 degrees C, and percent primary and secondary abnormalities. Semen was thawed at 37 and 24 degrees C. Spermatozoal concentration was counted with a hemocytometer. Bull age and season of collection were determined. Interaction of stud X thaw existed for both motility assessments and intact acrosomes, but 37 degrees C thaw resulted in higher motility and acrosomal integrity across all studs. Motility at zero hour was affected by season. Secondary abnormalities were influenced by season and stud X season. Interaction of thaw X season existed for incubated motility, which also was influenced by concentration and age. Age influenced secondary abnormalities. Heritabilities and repeatabilities (%) were .21, 44; .40, 34; .81, 74; and .31, 50 for 0-h motility, intact acrosomes, primary abnormalities, and secondary abnormalities. Genetic correlations were 0-h motility with acrosomal integrity and primary and secondary abnormalities, .88, -.70, -.93; acrosomal integrity with primary and secondary abnormalities, -.90, -.05; primary with secondary abnormalities, -.12. Selection for semen quality could improve fertility of bulls.

Relationship between final temperature, thaw rate, and quality of bovine semen

Relationships between thaw rate, thaw bath time, and initial bath and final seminal temperature with coefficients of determination .99 and .97 were: bath time = -.01 + 220.25(1/thaw rate); initial bath temperature = final seminal temperature - 7.29 + 390.05 (1/bath time). Ejaculates from 10 bulls were split and processed in egg yolk-citrate-glycerol, egg yolk-Tris-glycerol, and whole milk-glycerol. All semen was packaged and frozen in .5-ml French straws at -196 degrees C. Sixteen thaw treatments consisted of factorial combinations of four final seminal temperatures and four thaw rates. Treatments were assessed by post-thaw acrosomal integrity after 3-h 37 degrees C incubation. Seminal quality improved with increasing final seminal temperature up to 31 degrees C and did not differ between 31 and 44 degrees C for any of the extenders. A slow thaw rate (3 degrees C/s) resulted in inferior quality for all extenders, and rates 11, 19, and 27 degrees C/s resulted in similar quality for citrate and milk extended semen. Acrosomal integrity was most for 19 degrees C/s in Tris extended semen. A significant factorial interaction existed for Tris and milk extended semen. Predicted acrosomal response of 57.7% across all extenders was at optimum final seminal temperature and thaw rate 37 degrees C and 18 degrees C/s. Bath temperature and bath time determine optimum thaw rate and final temperature of semen packaged in French straws and thus maximize seminal quality.

Thawing optimums for bovine spermatozoa processed by three methods and packaged in Continental and French straws

A modified two-dimensional central composite rotatable design was used to study the effect of thaw bath temperature and time on acrosomal integrity in Continental (.3 ml) and French (.5 ml) straws. Ejaculates from 18 bulls were packaged in both containers. Semen from 6 of the 18 bulls was processed by each of three methods: 6 bulls for egg yolk-Tris-glycerol, 6 bulls for egg yolk-citrate-glycerol, and 6 bulls for skim milk-glycerol. Thaw bath temperatures ranged from 18 to 92 degrees C, and thaw times ranged from 4.5 to 50 s. Interaction of thaw bath temperature with thaw time was detected within each processing procedure and package. Maximum cell quality, measured by intact acrosomes after incubation of semen 3 h at 37 degrees C for .3-ml and .5-ml straws, was predicted to be achieved by thaw bath temperatures and times (degrees C/s) as follow: egg yolk-Tris-glycerol 40/32, 49/16; egg yolk-citrate-glycerol 43/30, 37/19; skim milk-glycerol 50/24, 36/24. Thawing procedures to maintain best acrosomal retention, regardless of processing method, were 44 degrees C for 29 s for .3-ml straws and 40 degrees C for 20 s for .5-ml straws.

Optimum thawing temperature and time for bovine semen processed by three methods and packaged in 1 ml ampules

A central composite rotatable design was used to determine optimum temperature and time for thawing semen which was processed in egg yolk-tris-glycerol (ETG), egg yolk-citrate-glycerol (ECG) and skim milk-glycerol (SMG) diluents. Percentage of progressive motility (PPM) and percentage of intact acrosomes (PIA) immediately after thawing (0-hr) and after 3-hr incubation at 37 degrees C were measured. The optimum conditions for temperature and time (C/sec) to sustain maximal PIA response after 3-hr incubation (PIA) were: ETG 42 degrees 121 , ECG 33 degrees 175 , and SMG 38 degrees 128 . Average conditions predicted to be "shared" by all three processing methods were 35 degrees C for 150 sec. Final seminal temperature (FST) was measured at each of these points for ETG, ECG and SMG. Each of the above conditions has a FST above 30 degrees C. A strip plot design was used to compare the optimum and predicted "shared" (35 degrees C 150 sec ) conditions with recommended method (35 degrees C 65 sec ) presently in use, denoted as "present". The predicted "shared" thawing conditions resulted in greater (P<0.01) cell viability (PPM and PIA) than did the "present" thawing method both before and after 3-hr incubation. The viability of semen thawed by the predicted "shared" method did not differ (P<0.05) from that resulting from the optimum thawing condition for each processing method (ETG, ECG and SMG) at 0-hr or 3-hr incubation. Cell viability of skim milk-glycerol processed semen degraded faster over the 3-hr incubation period that did that of ETG or ECG processed semen.

Effects of premilking udder preparation on environmental bacterial contamination of milk

Premilking udder preparations varied wetness and cleanliness of udders and teats at machine attachment. In Experiment I, in a prep stall with manual drying of teats only, udder surface drainage during milking increased standard plate counts compared to preparations with dryer udder surfaces at machine attachment. In Experiment 2, use of prep stall only and no udder and teat preparation had higher standard plate counts than preparations by prep stall with manual drying of udder and teats and by wet paper towels in wetting and cleaning and dry paper towels in drying teats. No preparation of udder and teats had higher standard plate count attributed to soiled teats at machine attachment. Udder surfaces should be dry, and teats should be clean and dry at machine attachment. Premilking udder preparations can affect milk quality as measured by milk bacterial count.

Effects of vacuum and pulsation ratio on udder health

Effects of vacuum and pulsation ratio on udder health were studied for 36 first parity animals in a 60-day trial. Treatments consisted of vacuum at 33.3, 41.6, and 50 kPa at pulsation ratios of 50:50, 60:40, and 70:30 at 60 pulsations per min. All teats were exposed to a culture broth of Staphylococcus aureus after machine removal. Numbers of intramammary infections and somatic cells were determined. Analysis for number of intramammary infections indicated no significant differences among treatments for number of infected available quarters. Trend for intramammary infections was that as pulsation ratio widened, the number of infected available quarters increased, especially at the ratio 70:30. As vacuum increased, number of infected available quarters increased. Least squares means of Wisconsin Mastitis Test scores were 6.29, 5.57, and 6.68 for 33.3 kPa; 12.18, 3.82, and 7.86 for 41.6 kPa; and 9.11, 6.40, and 15.02 for 50 kPa at pulsation ratios 50:50, 60:40, and 70:30. There were significant differences among treatments for vacuum and pulsation ratio. Wisconsin Mastitis Test data indicated an interaction between vacuum and pulsation ratio. Optimum predicted vacuum and pulsation ratio based on Wisconsin Mastitis Test data were 27.2 kPa and 62:38.

Development of the conceptus in the bovine

Growth of fetuses, fetal membranes, and fetal fluids was characterized by least squares analysis for 254 conceptuses ranging from 25 to 278 days of gestation. Prior to 100 days of gestation, increases in allantoic fluid volume and chorio-allantoic membrane weight preceded those of fetal weight, amnio-allantoic membrane weight, and amniotic fluid volume. The relative rate of growth of components suggests a prerequisite of chorio-allantoic membrane expansion for subsequent fetal growth. Male fetuses were heavier than female fetuses as early as 100 days of gestation. Rate of growth of all fetuses was maximal at 230 days of gestation with a peak rate of greater than 200 g/day. Growth rate then declined to less than 100 g/day by term.

Detection and characterization of differences in plasma corticoid response to treatments

Ten experiments involving 3013 observations and 103 animals were studied to characterize variation associated with bovine plasma corticoid concentrations (ng/ml). Total corticoids, corticosterone, or cortisol were measured by competitve protein binding assay. Animals were noncystic or cystic, and measurements were made to establish basal concentrations or to estimate response to stimulation by adrenocorticotrophic hormone injection. Data were analyzed by least squares with the nested model: treatment regimen, animal in treatment, sample in animal in treatment, and sampling time to the highest order of regression (up to seventh) which was statistically significant (P less than .05). Estimates of error variances ranged from .31 for basal cortisol in cystic animals to 233.27 for total corticoids in noncystic, stimulated animals. Coefficients of variation among experiments ranged from 33 to 87% with mean 61%. In most analyses, estimates of experimental error were large indicating need for careful attention to experimental design to insure efficient least-cost experimentation. Use of the power function for nested analysis of variance to accomplish this is demonstrated.