Biomedical subjects

K E Leslie

Publications and source records attributed to K E Leslie.

At least 19 recordsLinked to original sources

PubMed2007

Prevalence and risk factors for postpartum anovulatory condition in dairy cows.

The objectives of this research were to determine the prevalence of the anovulatory condition within a temperate region of North America and identify cow-level and herd-level risk factors for this condition. A total of 1,341 cows from 18 herds were classified as cycling or anovular based on skim milk progesterone concentration determined at 46 and 60 +/- 7 d in milk. Calving history, periparturient disease incidence, body condition score, milk ketone concentration in the first 2 wk of lactation, and first 305-d mature-equivalent milk projections were recorded. Reproductive and culling information was retrieved monthly from the Dairy Herd Improvement Association. The cow-level prevalence of anovulation was 19.5%, with a herd-specific range from 5 to 45%. Accounting for the effect of clustering at the herd level, cows experiencing a difficult calving, cows with twin calvings, displaced abomasum, and cows with subclinical ketosis in the first week after calving were at greater risk for diagnosis of anovulation. Anovular cows within herds using ovulation synchronization programs were inseminated at the same time postpartum with a 6-percentage point reduction in the probability of pregnancy relative to cycling herdmates (29.7 vs. 35.9%, respectively), whereas anovular cows in herds breeding based on observed estrus were inseminated 8 d later and suffered a 10-percentage point reduction in the probability of pregnancy at first insemination (20.3 vs. 30.5). Time to pregnancy was delayed in anovular cows by 30 d (156 vs. 126 d). Using survival analysis, the impact of anovulation decreased with time. The daily probability of pregnancy (hazard ratio) was similar to cycling cows by 165 d in milk. The results underline the important associations of peripartum health with reproductive function and performance.

Animals↗

PubMed2006

The effect of a progesterone releasing intravaginal device (PRID) on pregnancy risk to fixed-time insemination following diagnosis of non-pregnancy in dairy cows.

The objective was to compare the probability of pregnancy after fixed-time insemination in cows diagnosed as non-pregnant and re-inseminated following the Ovsynch protocol, with or without exogenous progesterone. Cows (n=415) used in this study originated from 25 farms. Upon diagnosis of non-pregnancy between 30 and 60 days after AI, cows were randomly assigned to receive either a progesterone releasing intravaginal device (PRID; n=208) or a placebo intravaginal device (PID; n=207). All cows received GnRH at enrollment (Day 0), PGF(2alpha) concurrent with intravaginal device removal 7 days later, GnRH on Day 9 and fixed-time insemination 16h later (Day 10). Cows observed in estrus prior to Day 7, had the device removed and were inseminated. Ovaries were examined by transrectal palpation at the time of enrollment and the prominent structures were assessed and recorded. Body condition score, lameness status, interval from previous insemination, and times bred at enrollment were recorded. At intravaginal device removal, the occurrence and intensity of vaginitis was determined according to the amount of debris on the device. Overall, the intravaginal device retention rate was 91%. A total of 5.2% of PID-treated cows and 2.9% of PRID-treated cows were detected in estrus within the 7 days treatment period. Pregnancy status was diagnosed between 30 and 56 days after insemination and all cows were followed for a minimum of 150 days after enrollment. Approximately 28% of cows had evidence of mild vaginitis in response to the intravaginal device, whereas 6% of cows had copious debris associated with the intravaginal device at removal. The probability of pregnancy after fixed-time insemination was 43.8% versus 34.9% in PRID-treated versus PID-treated animals. Exogenous progesterone provided through an intravaginal device to non-pregnant cows that had not displayed estrus improved the probability of pregnancy after fixed-time AI.

Administration, Intravaginal↗

PubMed2006

Test characteristics from latent-class models of the California Mastitis Test.

We evaluated (using latent-class models) the ability of the California Mastitis Test (CMT) to identify cows with intramammary infections on the day of dry-off. The positive and negative predictive values of this test to identify cows requiring dry-cow antibiotics (i.e. infected) was also assessed. We used 752 Holstein-Friesian cows from 11 herds for this investigation. Milk samples were collected for bacteriology, and the CMT was performed cow-side, prior to milking on the day of dry-off. At the cow-level, the sensitivity and specificity of the CMT (using the four quarter results interpreted in parallel) for identifying all pathogens were estimated at 70 and 48%, respectively. If only major pathogens were considered the sensitivity of the CMT increased to 86%. The negative predictive value of the CMT was >95% for herds with major-pathogen intramammary-infection prevalence <15%, so that selective dry-cow therapy might be reasonable for such herds if cows were screened with the CMT.

Animals↗

PubMed2006

Bovine whey proteins inhibit the interaction of Staphylococcus aureus and bacteriophage K.

AIMS: To understand the potential use of bacteriophage K to treat bovine Staphylococcus aureus mastitis, we studied the role of whey proteins in the inhibition of the phage-pathogen interaction in vitro. METHODS AND RESULTS: The interaction of bacteriophage K and S. aureus strain Newbould 305 was studied in raw bovine whey and serum. Incubation of S. aureus with phage in whey showed that the bacteria are more resistant to phage lysis when grown in whey and also bovine serum. Whey collected from 23 animals showed a wide variation in the level of phage-binding inhibition. The role of the protein component of milk whey in this inhibition was established; treatment of the whey by heat, proteases and ultrafiltration removed the inhibitory activity. Brief exposure of S. aureus cells to whey, followed by resuspension in broth, also reduced phage binding. Microscopy showed the adhesion of extracellular material to the S. aureus cell surface following exposure to whey. Chromatographic fractionation of the whey demonstrated that the inhibitory proteins were present in the high molecular weight fraction. CONCLUSIONS: The adsorption of whey proteins to the S. aureus cell surface appeared to inhibit phage attachment and thereby hindered lysis. The inhibitory whey proteins are of high molecular weight in their native form and may sterically block phage attachment sites on the cell surface. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings have implications for any future use of phage therapy in the treatment of mastitis, and other diseases, caused by S. aureus. This pathogen is predicted to be much more resistant to phage treatment in vivo than would be expected from in vitro broth culture experiments.

Animals↗

PubMed2006

Efficacy and pharmacokinetics of bacteriophage therapy in treatment of subclinical Staphylococcus aureus mastitis in lactating dairy cattle.

Bovine mastitis is an inflammation of the udder caused by microbial infection. Mastitis caused by Staphylococcus aureus is a major concern to the dairy industry due to its resistance to antibiotic treatment and its propensity to recur chronically. Growing concerns surrounding antibiotic resistance have spurred research into alternative treatment methods. The ability of lytic S. aureus bacteriophage K to eliminate bovine S. aureus intramammary infection during lactation was evaluated in a placebo-controlled, multisite trial. Twenty-four lactating Holstein cows with preexisting subclinical S. aureus mastitis were treated. Treatment consisted of 10-ml intramammary infusions of either 1.25 x 10(11) PFU of phage K or saline, administered once per day for 5 days. The cure rate was established by the assessment of four serial samples collected following treatment. The cure rate was 3 of 18 quarters (16.7%) in the phage-treated group, while none of the 20 saline-treated quarters were cured. This difference was not statistically significant. The effects of phage intramammary infusion on the bovine mammary gland were also studied. In healthy lactating cows, a single infusion of either filter-sterilized broth lysate or a CsCl gradient-purified phage preparation elicited a large increase in the milk somatic cell count. This response was not observed when phage was infused into quarters which were already infected with S. aureus. Phage-infused healthy quarters continued to shed viable bacteriophage into the milk for up to 36 h postinfusion. The phage concentration in the milk suggested that there was significant degradation or inactivation of the infused phage within the gland.

Animals↗

PubMed2006

Major advances in disease prevention in dairy cattle.

This paper describes some of the major points of progress and challenges in health management of dairy cattle in the last 25 yr. A selection of the leading contributors in the field is acknowledged. Specific advances in the areas of transition cow management, epidemiology, udder health, applied immunology, housing design, calf health, and health-monitoring tools are described. The greatest advances in dairy health in the last 25 yr have been the shifts to disease prevention, rather than treatment, as well as from focus on individual animals to groups and herds. A fundamental advancement has been recognition of the multifactorial nature of almost all diseases of importance in dairy cattle. Epidemiology has been a critical new tool used to describe and quantify the interconnected risk factors that produce disease. Another major advance has been redefining disease more broadly, to include subclinical conditions (e.g., subclinical mastitis, ketosis, rumen acidosis, and endometritis). This expansion resulted both from improved technology to measure function at the organ level and, just as importantly, from the evolution of the health management paradigm in which any factor that limits animal or herd performance might be considered a component of disease. Links between cattle and people through consideration of environmental or ecosystem health are likely to further expand the concept of disease prevention in the future. Notable successes are decreases in the incidence of milk fever, clinical respiratory disease in adults, contagious mastitis, and clinical parasitism. There has also been improved protection through vaccination against coliform mastitis and bovine virus diarrhea. Since 1980, average herd size and milk production per cow have increased dramatically. Despite these increased demands on cows' metabolism and humans' management skills, the incidence of most common and important diseases has remained stable. Great progress has been made in understanding the biology of energy metabolism and immune function in transition dairy cows, the time at which the majority of disease occurs. Coupled with an emerging understanding of how best to provide for dairy cows' behavioral needs, transition cow management promises to be the foundation for progress in maintenance and enhancement of the health of dairy cows in the next 25 yr.

Animal Nutritional Physiological Phenomena↗

PubMed2006

Effects of prepartum intramammary antibiotic therapy on udder health, milk production, and reproductive performance in dairy heifers.

Preparturient heifers (n = 561) from 9 herds in 6 US states and 1 Canadian province were enrolled in a study to test the hypothesis that prepartum intramammary therapy would cure existing intramammary infections (IMI) and lead to increased milk production, reduced linear somatic cell count (LSCC), and improved reproductive performance. Mammary secretions were collected 10 to 21 d before expected calving from each quarter. Heifers were then assigned by identification number to receive intramammary therapy consisting of infusion of one tube per mammary quarter of a lactating cow commercial antibiotic preparation containing cephapirin or to a nontreated control group. Overall, 34.1% of mammary quarters were infected with a mastitis pathogen before parturition and 63.4% of heifers had at least one mammary quarter infected. The coagulase-negative staphylococci (CNS) caused the majority (74.8%) of prepartum IMI. Coagulase-positive staphylococci, environmental streptococci, and coliforms accounted for 24.5% of prepartum infections. Treatment had a significant effect on the cure rate of infected mammary quarters. Mammary quarters that were infected prepartum and treated with antibiotics had a 59.5% efficacy of cure rate and the percentage reduction in heifers with IMI was 51.9. Control quarters had a spontaneous cure rate of 31.7%. Treatment did not significantly affect milk production or LSCC in the first 200 d of lactation; however, there was a significant treatment by herd interaction for milk production. Quarters cured of either CNS or major pathogens had a lower LSCC in the first 200 d of lactation. No significant effect on services per conception or days open between treatment and control groups was observed. This trial demonstrated that prepartum intramammary antibiotic therapy did reduce the number of heifer IMI postpartum. Milk production, LSCC, and reproductive performance during the first 200 d of the first lactation were not significantly affected by treatment. Given these results, use of prepartum intramammary antibiotic therapy in heifers as a universal strategy to increase milk production in first-lactation dairy cows may not be warranted.

Animals↗

PubMed2006

Efficacy of two hydrogen peroxide teat disinfectants against Staphylococcus aureus and Streptococcus agalactiae.

An experimental teat dip containing 0.5% hydrogen peroxide as the active ingredient was compared with a teat disinfectant also containing 0.5% hydrogen peroxide that is commercially available throughout North America. The study was conducted under conditions of experimental challenge with a positive control following the guidelines recommended by the National Mastitis Council. The efficacy of the test product and the positive control product were compared in 45 cows, with 89 total teats receiving each product after milking during a 10-wk study period. There was no significant difference between the experimental hydrogen peroxide product and the positive control in new intramammary infections caused by Staphylococcus aureus (27.0 and 18.0% in the treatment groups, respectively). Additionally, there was no significant difference between the experimental product (6.7%) and the positive control groups (4.5%) in new intramammary infections caused by Streptococcus agalactiae. Traditional analysis of teat skin condition changes supported improved teat skin condition with the test disinfectant. After accounting for the correlation of teats within cow, significant differences were also observed between the treatment groups for teat skin condition. The experimental hydrogen peroxide-based teat disinfectant provided efficacy similar to that of the positive control teat disinfectant, with significant improvement in teat skin condition and no adverse effects on teat end condition.

Animals↗

PubMed2006

An evaluation of two indirect methods of estimating body weight in Holstein calves and heifers.

Monitoring the growth of replacement heifers is a useful management tool to assist producers in achieving a reasonable goal for age at first calving. Standard growth curves have been established, and heart girth tapes are widely available to estimate body weight (BW). Probably the easiest, and undoubtedly the most accurate, means of determining the actual BW of heifers is by using a calibrated electronic scale. However, if an electronic scale is not available, indirect methods of BW estimation are required. The hipometer is a new indirect tool that uses the external width between the greater trochanters of the left and right femurs to estimate BW. The purpose of this observational study was to evaluate the hipometer and the heart girth tape to estimate the BW of Holstein heifers, as compared with their actual weight recorded by an electronic scale. A total of 311 Holstein heifers in 4 research herds, ranging in age from 1 wk old to immediately prior to calving (24 mo), were used in this comparison. The mean BW of all heifers was 261 +/- 124 kg. The Pearson values of the correlation between the scale and hipometer weights, and the scale and tape weights were 0.92 and 0.94, respectively. The concordance correlations of scale weight with hipometer and tape weights were 0.98 and 0.99, respectively. The agreement among the 3 methods, as assessed by the kappa statistic, was substantial for heifers aged 3 to 15 mo. However, poor to no agreement was observed in heifers younger than 3 mo, as well as at 15 mo of age or greater (kappa 0 to 0.18). This is of particular concern because these groups represent the age when dairy heifers would be weaned (< 3 mo) and the age when breeding would normally commence (> 15 mo). We concluded that the hipometer is an easy and useful alternative method of estimating the BW of Holstein heifers, particularly in heifers aged 3 to 15 mo.

Animals↗

PubMed2006

Effects of rumen-protected choline and monensin on milk production and metabolism of periparturient dairy cows.

Choline and monensin may be supplemented during the transition period with the objectives of aiding in fat metabolism and improving energy balance, respectively. The objectives of this study were to determine the effects of supplementing rumen-protected choline (RPC) and monensin in a controlled-release capsule (CRC) on metabolism, dry matter intake, milk production, and liver function in transition dairy cattle. Three weeks before expected calving, 182 Holsteins were randomly assigned to receive one of the following: a monensin CRC, 56 g/d of RPC until 28 d in milk, CRC + RPC, or neither supplement (control). Blood samples were collected at enrollment, 1 wk before calving, and in the first and second weeks after calving. Liver biopsies were obtained from multiparous cows randomly selected from each treatment group within 24 h and again 3 wk postpartum. Daily milk production was recorded through 60 d in milk. There were no interactions of the effects of RPC and CRC on any of the outcomes measured. Overall, cows that received RPC produced 1.2 kg/d more milk in the first 60 d of lactation, but this effect was attributable to an increase in milk production of 4.4 kg/d among cows with a body condition score > or =4 at 3 wk before calving; fat cows that received RPC ate 1.1 kg of DM/d more from wk 3 before calving through wk 4 after calving. Monensin supplementation significantly increased serum concentrations of glucose and urea, lowered concentrations of beta-hydroxybutyric acid and aspartate aminotransferase in the peripartum period, and increased liver glycogen content at 3 wk into lactation. The metabolic effects of CRC are consistent with previous studies, and the effects on liver are novel. The mechanism by which RPC increased milk production was not revealed in this study and merits further research.

Animal Feed↗

PubMed2005

Risk factors associated with Neospora caninum abortion in Ontario Holstein dairy herds.

The objective of this epidemiological study was to identify risk factors for Neospora caninum-related abortions in Ontario Holstein dairy herds. A total of 88 herds, consisting of 5080 cattle, and utilizing Dairy Herd Improvement (DHI) services, were divided into three groups. Case (n = 30) and first control (n = 31) herds were selected from 1998 and 1999 fetal abortion submissions to the Animal Health Laboratory, University of Guelph, that were histopathologically positive or negative, respectively, for N. caninum. A second control group (n = 27) was selected from multiple sources of herds sampled within the previous 4 years that had a low seroprevalence (<7%) to N. caninum. Between May and December 1999, all available cows on all farms, in parity one or greater, were blood sampled. The sera were then analyzed for antibody to N. caninum using a kinetic ELISA. A survey administered at the time of sampling recorded information on housing, animal species present, manure management, reproduction, biosecurity practices, wildlife observations, peri-parturient cow management, herd disease history and nutrition. Production and other herd parameters were obtained from DHI records. Logistic regression indicated that the following parameters were positively associated with a N. caninum abortion in a herd: the N. caninum herd seroprevalence (OR = 1.1), the total number of dogs on a farm (OR = 2.8), the frequency that dogs were observed defecating in mangers (OR = 2.8), the number of horses on a farm (OR = 3.1), the observed annual rate of retained fetal membranes (OR = 1.2) and the observed annual rate of cows returning to estrus after pregnancy confirmation (OR = 1.2). Factors negatively associated were the frequency of stray cats and wild canids observed on a farm (OR = 0.4 and OR = 0.7, respectively) and the housing of heifers on loafing packs (a housing pen divided into feed manger, scrape alley and bedded pack areas, OR = 0.1).

Abortion, Veterinary↗

PubMed2005

Effect of presynchronization using prostaglandin F2alpha and a milk-ejection test on pregnancy rate after the timed artificial insemination protocol, Ovsynch.

The objective of this research was to determine if PGF2alpha-induced milk letdown (ML) is an accurate indicator of luteolysis, allowing cows to be synchronized to begin the Ovsynch protocol (GnRH-7d-PGF2alpha-2d-GnRH-24h-AI) at the most beneficial time of the estrous cycle (days 5-9), and determine if this would improve pregnancy rate (PR). Lactating Holstein cows between 55 and 70 days in milk were used to evaluate the ML test and PR after the Ovsynch protocol, when initiated on the basis of the test result (PROSYNCH). PROSYNCH cows (n = 60) had one teat cannulated to test for ML and were treated with 500 microg cloprostenol, PGF2alpha analogue (PG). Cows with ML were started on Ovsynch 10 days later, and those without started 3 days later. Cows in the control group (OVSYNCH, n = 64) were injected with physiological saline and observed for ML. This group was started on Ovsynch 10 days after saline treatment. Milk samples were collected thrice weekly to determine progesterone concentrations. ML indicated luteolysis with a sensitivity of 98% and a specificity of 60%. The positive and negative predictive values were 83 and 92%, respectively. Pregnancy rates were 48% for PROSYNCH and 52% for OVSYNCH (P = 0.72). When data from both groups were combined, PR was greater in cows that started the Ovsynch protocol in stage 2 of the estrous cycle (days 5-9, 67%) than all other stages (stage 1: days 1-4, 35%; stage 3: days 10-16, 45%; stage 4: days 17-21, 42%; P < 0.01). The proportion of animals with ovulation after GnRH#1, luteolysis after PGF2alpha, and ovulation after GnRH#2 were all greater in the PROSYNCH group (77% versus 55%, P < 0.02; 83% versus 66%, P < 0.03; 97% versus 84%, P < 0.03, respectively). Therefore, the ML test indicated luteolysis with sufficient precision to time the initiation of the Ovsynch protocol between days 5 and 9 of the cycle, however, this did not alter PR compared to starting the protocol randomly throughout the cycle. Initiating the Ovsynch protocol between days 5 and 9 of the cycle increased PR, and improved the efficacy of each injection.

Animals↗

PubMed2005

The effect of a single administration of cephapirin or cloprostenol on the reproductive performance of dairy cows with subclinical endometritis.

This study examined the effect of a single administration of cephapirin iu or cloprostenol im on the reproductive performance of dairy cows with subclinical endometritis. Cows (n = 228) at 20-33 days in milk (DIM) from two commercial dairy farms, determined to be normal for clinical endometritis (based on absence of abnormal uterine discharge on vaginoscopic examination) were enrolled. At enrollment, a thorough reproductive examination was performed, including rectal palpation, ultrasonography (US) and endometrial cytology (EC). The case definition for subclinical endometritis was the presence of >18% neutrophils on EC examination or fluid in uterus (FIU) on US examination. All cows were randomly assigned to receive one of three treatments: 500 mg benzathine cephapirin iu, 500 microg cloprostenol im, or control (no treatment). Reproductive performance was monitored for a minimum of 8 months after treatment. Cows with subclinical endometritis treated with cephapirin or cloprostenol had a significantly increased relative pregnancy rate compared to control [hazard ratios 1.89 (P = 0.01) and 1.70 (P = 0.05), respectively]. In conclusion, a single treatment with cephapirin or cloprostenol at 20-33 DIM significantly improved the reproductive performance of cows with subclinical endometritis.

Animals↗

PubMed2005

Metabolic predictors of displaced abomasum in dairy cattle.

The objective of this field study was to identify metabolic tests available in clinical practice that identified cows at increased risk of left displaced abomasum (LDA). A technician visited 1044 cows in 20 herds weekly from 1 wk before expected calving until 1 wk postpartum. Cows were assigned a body condition score and samples were collected at each visit for measurement of serum nonesterified fatty acids (NEFA), cholesterol, beta-hydroxybutyrate (BHBA), glucose, urea, calcium, and phosphorus, and a milk sample was collected postpartum for measurement of BHBA. The probability of LDA was modeled with multivariable logistic regression accounting for clustering. There were 53 cases of LDA (incidence risk = 5.1%) and the median time of diagnosis was 11 d in milk. In cows with LDA, mean NEFA concentrations began to diverge from the mean in cows without LDA 14 d before calving, whereas mean serum BHBA concentrations did not diverge until the day of calving. Prepartum, only NEFA concentration was associated with risk of subsequent LDA. Between 0 and 6 d before calving, cows with NEFA concentration > or =0.5 mEq/L were 3.6 times more likely to develop LDA after calving. For prospective application, among samples taken 4 to 10 d before expected calving, the optimum NEFA cut-point remained 0.5 mEq/L. The sensitivity, specificity, and likelihood ratio (LR) were 46%, 82%, and 2.6, respectively. Between 1 and 7 d postpartum, retained placenta, metritis, and increasing serum concentrations of BHBA and NEFA were associated with increased risk of subsequent LDA. However, considered separately, postpartum serum BHBA was a more sensitive and specific test than NEFA concentration. The odds of LDA were 8 times greater in cows with serum BHBA > or =1200 micromol/L (LR = 3.5). Cows with milk BHBA concentration > or =200 micromol/L were 3.4 times more likely to develop LDA. Serum calcium concentration was not associated with LDA. Strategic use of metabolic tests to monitor transition dairy cows should focus on NEFA in the last week prepartum and BHBA in the first week postpartum.

3-Hydroxybutyric Acid↗

PubMed2005

Efficacy of an iodophore teat disinfectant against Staphylococcus aureus and Streptococcus agalactiae in experimental challenge.

A 1.0% iodophore teat disinfectant (Full-Bac) was evaluated in comparison with a positive control (Bovadine), a commercially available 1.0% iodophore teat disinfectant. The study was conducted under conditions of experimental challenge, following the guidelines recommended by the National Mastitis Council. The test product and a positive control were compared in 41 cows, with 82 teats receiving each product at milking, during a 10-wk study period. There were no differences between the test product and the positive control in new intramammary infections due to Staphylococcus aureus, which averaged 13.4% in each of the 2 treatment groups. Additionally, no statistical difference was seen between the test product and positive control in new intramammary infections by Streptococcus agalactiae, which averaged 8.5 and 6.1% for the Full-Bac and Bovadine groups, respectively. Teat skin and teat end condition scores were statistically evaluated at wk 1, 5, and 9 of the study, and no significant differences were observed between the treatment groups. The test teat disinfectant provided similar germicidal activity to that of the positive control teat disinfectant with no adverse effects on teat skin or teat end condition during the warm-season study period.

Animals↗

PubMed2005

The association of herd milk production and management with a return-over-feed index in Ontario dairy herds.

Associations of herd milk production and management variables to a return-over-feed (ROF) herd profit index were examined among 95 dairy farms. The ROF index is derived from 2 important determinants of profit on dairy farms: milk income and feed cost. All producers were participants in the Dairy Herd Improvement (DHI) ROF program in Ontario, Canada during 2002. Nutrition, housing, health, and other management data were collected through a phone survey of herd managers. Herd milk production, milk component percentages, and somatic cell count data were obtained from the Ontario DHI database. The linear regression model accounting for significant variation in ROF with highest R2 (0.66) included standardized milk production, milk protein percentage, milk fat percentage, and use of monensin in lactating cow rations. A 1-kg increase in standardized milk production (kg/d per cow) or a 0.1 percentage unit increase in milk protein was associated with $0.35/d per cow or $0.26/d per cow increase, respectively, in the ROF of the dairy herd. However, a 0.1 percentage unit increase in milk fat was associated with a $0.10/d per cow decrease in ROF, probably because of a negative association of milk fat with milk yield. Use of monensin in lactating cow rations was associated with a $0.39/d per cow increase in ROF. In a separate model (R2 = 0.27) that examined management factors independent of production variables, herds using 3 times daily milking had a $1.25/d per cow higher ROF vs. herds using twice daily, whereas use of an Escherichia coli mastitis vaccine was associated with $0.59/d per cow higher ROF. Production-related variables accounted for more variation in the ROF index than management variables, and the latter, e.g., use of monensin, only marginally increased R2 of production-based regression models.

Animal Feed↗

PubMed2005

Effect of halofuginone lactate on the occurrence of Cryptosporidium parvum and growth of neonatal dairy calves.

Thirty-one Holstein bull calves were purchased at birth from 3 dairy farms in Eastern Ontario. Each calf was assigned at random to oral treatment with either 5 mg of halofuginone lactate in 10.0 mL of aqueous carrier solution (Halocur, base comprised 10 mg of benzoic acid, 100 mg of lactic acid, and 0.3 mg of tartrazine) or 10 mL of placebo (Halocur base minus the active ingredient, halofuginone lactate) administered 15 to 30 min after morning milk feeding for the first 7 d of life. Intakes of milk, calf starter, and water, and fecal consistency score were recorded daily for 56 d. Calf weights were recorded weekly for 56 d. Fecal samples were taken from all calves at approximately 2, 7, 14, 21, and 28 d of age for isolation of Cryptosporidium parvum oocysts. Logistic and linear regression analyses were used to assess the effect of treatment on the incidence of diarrhea and C. parvum infection status. The odds of C. parvum shedding among calves in the halofuginone lactate-treated group was 70% lower than the odds of shedding among calves in the placebo group. In calves treated with halofuginone lactate, no oocyst shedding occurred until 2 wk of age, whereas 12.5% of calves in the placebo group began shedding oocysts during wk 1. From all ages of placebo-treated calves, 31 of 73 samples (42.5%) were positive for C. parvum, whereas only 15 of 67 samples (22.4%) from all ages of halofuginone lactate-treated calves tested positive. The largest number of C. parvum-positive samples occurred in the third week of life. There was a significant delay of 3.1 d in the incidence of diarrhea among calves treated with halofuginone lactate. Intake of milk and starter, body weight gains, and age at weaning were not significantly different between treatment groups.

Animals↗

PubMed2004

Association of cow and quarter-level factors at drying-off with new intramammary infections during the dry period.

Our objective was to describe cow and quarter-level factors associated with drying-off, and to evaluate their impacts on new intramammary infections (IMI) during the dry period. Data from 300 cows in five research herds were collected starting 2 weeks prior to scheduled drying-off. Variables of interest included daily milk production, teat-end integrity, formation of the teat-canal keratin plug, and quarter-milk bacteriological culture results. Overall, 11% of quarters developed new IMI in the dry period; this varied by herd, parity and time of the study. Most new IMI were caused by environmental streptococci and coliform organisms (34 and 30%, respectively). Quarters that had a cracked teat-end had higher odds of developing new infections than those without cracks (15 and 10%, respectively). Quarters that formed a keratin plug early in the dry period had a lower odds than those that did not close (10 and 14%, respectively). After 6 dry weeks, 23% of quarters were still open. The hazard of quarters closing if milk production on the day prior to drying-off was >21 kg 1.8-times less.

Animals↗