The relationship between compost bedded pack performance,management, and bacterial counts

The objective of this study was to assess the relationships among temperature, moisture, carbon-to-nitrogen (C:N) ratio, space per cow, and bacterial counts from bedding material collected from compost bedded pack (CBP) barns. A field survey of 42 routinely aerated CBP barns was conducted in Kentucky between October 2010 and March 2011. Two bedding material samples of 1,064.7 cm³ each were collected during a single site visit from 9 evenly distributed locations throughout each barn and thoroughly mixed to create a composite sample representative of the entire CBP. Bacterial counts were determined for coliforms, Escherichia coli, streptococci, staphylococci, and Bacillus spp. University of Kentucky Regulatory Services (Lexington) laboratory personnel performed nutrient analyses to determine moisture, carbon, and nitrogen contents. Surface and 10.2-cm pack depth temperatures were collected for each of the 9 evenly distributed locations and the mean calculated to produce a composite temperature. Space per cow was calculated as the total CBP area divided by number of cows housed on the CBP. The GLM procedure of SAS (SAS Institute Inc., Cary, NC) generated models to describe factors affecting bacterial counts. Bacterial counts were 6.3 ± 0.6, 6.0 ± 0.6, 7.2 ± 0.7, 7.9 ± 0.5, and 7.6 ± 0.5 log₁₀ cfu/g of dry matter for coliform, Escherichia coli, streptococci, staphylococci, and Bacillus spp., respectively. Composite temperature, CBP moisture, C:N ratio, and space per cow had no effect on coliform counts. Escherichia coli reached a peak concentration when the C:N ratio was between 30:1 and 35:1. Staphylococci counts increased as ambient temperature increased. Streptococci counts decreased with increased space per cow and composite temperature and increased with increasing ambient temperature and moisture. Streptococci counts peaked at a C:N ratio ranging from 16:1 to 18:1. Bacillus spp. counts were reduced with increasing moisture, C:N ratio, and ambient temperature. Mastitis-causing bacteria thrive in similar conditions to that of composting bacteria and microbes, making elimination of these at higher temperatures (55 to 65°C) difficult in an active composting environment. Producers must use recommended milking procedures and other preventative practices to maintain low somatic cell count in herds with a CBP barn.     

Feeding strategies on certified organic dairy farms in Wisconsin and their effect on milk production and income over feed costs

The purposes of this study were (1) to analyze and categorize certified organic Wisconsin dairy farms based on general farm characteristics and feeding strategies during the course of 2010, and (2) to evaluate herd milk production and income over feed costs (IOFC). An on-site survey containing sections on farm demographics, feeding, grazing, and economics was conducted on 69 farms (12.6% survey response rate). A nonhierarchical clustering method using 9 variables related to general farm characteristics, feed supplementation, and grazing was applied to partition the farms into clusters. A scree plot was used to determine the most appropriate number of clusters. Dry matter intake was approximated based on farmer-reported total amounts of feed consumed (feed offered less refusals). Milk production was evaluated using reported milk rolling herd averages (RHA). Income over feed costs was calculated as milk sales minus feed expenses. The farms in clusters 1 (n = 8) and 3 (n = 32), the large and small high-input farms, respectively, included more feed ingredients in their lactating cow diets and relied more heavily on concentrates than farms in other clusters. Cows on these farms were predominantly Holstein. Clusters 1 and 3 had the highest RHA (6,878 and 7,457 kg/cow per year, respectively) and IOFC ($10.17 and $8.59/lactating cow per day, respectively). The farms in cluster 2 (n = 5) were completely seasonal, extremely low-input farms that relied much more heavily on pasture as a source of feed, with 4 out of the 5 farms having all of their operated land in pasture. Farms in cluster 2 relied on fewer feeds during both the grazing and nongrazing seasons compared with farms in the other clusters. These farms had the lowest RHA and IOFC at 3,632 kg/cow per year and $5.76/lactating cow per day, respectively. Cluster 4 (n = 24), the partly seasonal, moderate-input, pasture-based cluster, ranked third for RHA and IOFC (5,417 kg/cow per year and $5.92/lactating cow per day, respectively). Breeds other than Holstein were used more prevalently on farms in clusters 2 and 4. Results indicated extreme variation in animal breed, structure, and feeding strategies among Wisconsin organic dairy farms. Feeding strategies appeared to be major determinants of RHA and IOFC. These findings may serve current organic and transition farmers when considering feeding management changes needed to meet organic pasture rule requirements or dealing with dietary supplementation challenges.     

What happens with cow behavior when replacing concrete slatted floor by rubber coating: a case study

An enhanced productive life cycle and improved animal welfare are aims pursued in dairy husbandry. This study assesses experimental observations on floor-associated behavior during the stepwise replacement of concrete slatted flooring by rubber mats. For this purpose, estrus (mounting) and hygiene behavior (licking while standing on 3 legs and caudal licking) within a herd of 50 loose-housed Brown Swiss dairy cows were analyzed by video observation before and after floor reconstruction. Still photographs and pedometers were used to asses step length and number of steps, representing walking behavior. Compared with the concrete floor surface, rubber coating led to an increase in step length (58 ± 1 vs. 70 ± 1 cm; n = 35) and in steps per day (4,226 ± 450 vs. 5,611 ± 495; mean ± SEM; n = 9). Mounting was higher on the flooring covered with rubber mats (23 vs. 112). Collapsing or slipping during mounting only occurred on concrete slatted flooring (in 19 out of 23 mounting actions). Licking while standing on 3 legs and caudal licking increased up to 4-fold (105 vs. 511 observations). In conclusion, improvements were found in behavior when rubber-coated slatted floor surfaces were used in dairy cattle housing in transition from concrete flooring. Disorders in estrus and hygiene behavior were associated with the flooring of the barn and were relatively easy to investigate within the framework of farm welfare assessments.     

The impact of cooling ponds in North Central Texas on dairy farm performance

The objective of this study was to determine whether measurable differences existed between farms with and without cooling ponds. Data from Dairy Herd Improvement records for 1999 through 2002 were obtained on 42 herds located in North Central Texas. Nineteen herds had installed cooling ponds, whereas 23 herds had not. Monthly somatic cell counts for each herd were obtained from the Federal Milk Market Administrator. Data were analyzed using the PROC MIXED regression model of SAS. Within and across herd groups, milk production from June to October was significantly lower compared with milk production for the rest of the year. Although there was numerically higher average milk production per cow per day throughout the year for herds that used cooling ponds, differences between herd groups that used or did not use cooling ponds were significant only for August production. Herds without a cooling pond had 4.8 kg/d per cow lower production in August than in the cool-season months of November to May (26.4 ± 0.6 vs. 31.2 ± 0.5 kg/d), whereas the difference in August production was only 2.9 kg/d per cow in herds that used cooling ponds (29.0 ± 0.7 vs. 31.9 ± 0.6 kg/d). Differences caused by seasonal use of a cooling pond in culling, days to first service, days open, percentage of estruses observed, and somatic cell counts were not significant. Bulk tank milk samples cultured for 10 different bacteria showed no difference between cooling pond and noncooling pond herds in 2002. Also, there was no difference in incidence of violations from the Texas Department of Health for herds that used or did not use cooling ponds. However, herds with cooling ponds did have a lower percentage of successful breedings, fewer days dry, and a higher percentage of cows in milk compared with dairy herds that used other forms of cooling. Such differences may or may not be attributed to seasonal use of a cooling pond. Therefore, cooling ponds may provide relief from heat stress without adversely affecting most important measures of herd performance.     

Prevalence of mastitis pathogens in Ragusa, Sicily, from 2000 to 2006

The objective of this study was to report the prevalence of intramammary infections (IMI) in Ragusa, Sicily, from milk samples (n = 18,711) collected between October 2000 and June 2006 from 101 dairy herds. Milk samples were collected at 9,747 cow sampling events from 5,285 individual cows. Samples were individual quarter (92.8%) or composite samples (7.2%) from an individual cow. Logistic regression was used to examine the prevalence of IMI at the level of milk sample and at the level of cow, controlling for year and season of collection, type of sample (individual quarter or composite), and type of housing and bedding of the cow at the time of collection. Bedding and housing types were as follows, respectively (number of herd groups): bedding: none (61), organic [51 (straw, 50; sawdust, 1)], and sand (3); housing: bedded pack (37), free stalls (57), tie stalls (4), and paddock (17). Raw prevalence of cow IMI for a sample event was as follows (percentage of cow samples): no growth, 47.4%; coagulase-negative staphylococci, 22.6%; Staphylococcus aureus, 20.6%; other Streptococcus spp., 11.1%; Streptococcus agalactiae, 2.3%; coliform bacteria, 2.9%; and other organisms, 5.8%. Prevalence of IMI differed by bedding type for Staph. aureus (none, 24.5%; organic, 12.7%; sand, 12.3%) and coagulase-negative staphylococci (none, 13.1%; organic, 27.4%; sand, 26.9%) but not for Streptococcus spp. or coliform bacteria. Prevalence of Streptococcus spp. IMI differed by housing type (tie stalls, 22.2%; bedded pack, 12.8%; free stalls, 8.4%; paddock, 7.1%). Housing was not associated with the prevalence of IMI for other bacteria. Herd monthly prevalence of Staph. aureus and Streptococcus spp. IMI was associated with decreased mean milk production (Staph. aureus, −1.42 kg/d per cow, SEM 0.51; Streptococcus spp., −1.31 kg/d per cow, SEM 0.64) and increased mean linear score (Staph. aureus, 1.01 units/d per cow, SEM 0.16; Streptococcus spp., 0.59 units/d per cow, SEM 0.22). Herds (n = 11) with a mean linear score (MLS) less than 3.3 units had the lowest prevalence of Staph. aureus IMI and monthly MLS and the greatest monthly mean milk production compared with other herds grouped by MLS [MLS 3.31 to 3.99 (n = 20), MLS 4.00 to 4.46 (n = 20), MLS >4.46 (n = 17), and MLS not available (n = 33)]. Implementation of a milk quality program to control gram-positive organisms is important for Ragusa.     

Udder health of cows changing from tie stalls or free stalls with conventional milking to free stalls with either conventional or automatic milking

Udder health and milk production were monitored in cows transferred from tie stalls or loose housing with conventional milking to loose housing with either automatic or conventional milking. Data were collected from 182 Finnish farms from September 1999 to February 2006. Data from the first year before and first year after the changes were compared. A total of 88 herds changed from conventional milking (CM herds) to automatic milking (AM herds), 29 of which were housed in tie stalls and 59 of which were housed in a loose housing barn before the change. Additionally, 94 CM herds milked in loose housing barns that had been housed in tie stalls before the change were included. Milk record data consisted of annual herd size, parity, breed, calving dates, test day data [date, milk yield, and cow somatic cell count (SCC)] and records for treatments of clinical mastitis. Calculations were made for energy-corrected milk yield and logarithmic SCC (logSCC), proportion of cows at risk that experienced an SCC >200,000 cells/mL for the first time (highSCC), and number of treatments of clinical mastitis within a herd. Cows in tie stalls had higher milk yield (28.5 ± 0.29 vs. 26.5 ± 0.46 kg/d) and a lower logSCC (4.86 ± 0.01 vs. 4.95 ± 0.02) than cows in loose housing barns before the change. After the change, CM herds had slightly better udder health than AM herds because the proportion of cows at risk for highSCC was larger in AM herds (3.3 vs. 2.1%). The change in milking and housing systems caused a decline of 0.8 ± 0.25 kg/d per cow in energy-corrected milk yield, a slight increase in cow logSCC (from 4.88 ± 0.01 to 4.93 ± 0.01), and an increase of 0.6% in the proportion of cows having highSCC (from 2.5 to 3.1). The impact was clearer on herds that began automatic milking. Based on the results, the increase in bulk milk SCC of herds milked automatically in Finland was probably due to reduced separation of mastitic milk in AM herds.     

Risk factors associated with short-term post-treatment outcomes of clinical mastitis

The objectives of this study were to characterize 60-d outcomes after treatment of mild (abnormal milk) and moderate (abnormal milk and abnormal udder) cases of clinical mastitis (CM) occurring in a single quarter of cows on Wisconsin farms (n = 4) and to determine risk factors associated with those outcomes. Duplicate milk samples were collected from the affected quarter of each cow for microbiological analysis at the onset of CM (PRE) and 21 d later (POST). Cows were treated only in the affected quarter using an intramammary product containing 125 mg of ceftiofur. Bacteriological cure was defined as absence of pathogens in the POST sample obtained from the enrolled quarter. Recurrence was defined for the cow when CM occurred after the milk-withholding period for the enrolled case of CM. Retention in the herd was defined when a cow was retained within the herd for the 60-d follow-up period. Somatic cell count reduction (SCCR) was defined at the cow level as somatic cell count (SCC) below 200,000 cells/mL at the Dairy Herd Improvement Association test day occurring between 21 to 55 d post-treatment. The effects of farm, days in milk, parity, severity, microbiological diagnosis at PRE, previous milk yield, previous SCC, previous occurrence of CM and treatment duration on selected post-treatment outcomes were assessed using Chi-squared analysis and logistic regression. Microbiological results at PRE were distributed as: Escherichia coli (n = 14), Klebsiella spp. (n = 11), Enterobacter spp. (n = 8), Serratia spp. (n = 7), other gram-negative species (n = 3), Streptococcus spp. (n = 25), coagulase-negative staphylococci (n = 4); Staphylococcus aureus (n = 1); Streptococcus agalactiae (n = 1), other gram-positive species (n = 9), and culture negative (n = 60). Treated quarters were more likely to experience bacteriological cure when the cow experienced CM for the first time in the lactation and when no pathogen was recovered from PRE milk samples obtained from the enrolled quarter. Parity and bacteriological cure were associated with the probability of recurrence. Greater milk yield at previous Dairy Herd Improvement test was the most important predictor for retention within the herd. When SCC before CM was >200,000 cells/mL the probability of having SCCR after treatment was decreased. When the case experienced bacteriological cure, the cow was less likely to experience recurrent cases and was more likely to have SCCR below 200,000 cells/mL. Post-treatment outcomes, such as recurrence and SCCR, are strongly associated with bacteriological cure and, when monitored, can be used to help determine if a treatment has been successful. Information about the etiology of CM, history of clinical and subclinical mastitis, and parity are useful to review when making strategic treatment decisions.     

Technical note: A comparison of 2 methods of assessing lameness prevalence in tiestall herds

We compared 2 methods for identifying lame cows and estimating the prevalence of lameness in tiestalls. Cows (n = 320) in 9 tiestall herds were scored as lame both by the presence of limping while walking and by stall lameness scores (SLS). The SLS was based on the number of the following behaviors that the cow showed while standing in the tiestall: weight shifting, standing on the edge of the stall, uneven weight bearing while standing, and uneven weight bearing while moving from side to side. Two observers watched video-recordings of the cows. Intraobserver agreements for the 4 SLS behaviors ranged from 92 to 100%, and interobserver agreement ranged from 81 to 100%. The overall prevalence of lameness based on an SLS of ≥2 was similar to that of limping (39 vs. 40%). The sensitivity of the classification based on the SLS was 0.63 and the specificity was 0.77 in identifying cows with a limp; accuracy varied across farms from 62.2 to 80.4%, with a mean of 71.7%. A cow with an SLS of ≥2 had 4.88 times the odds of limping than a cow with an SLS of <2. The prevalence of lameness on farms based on SLS was highly correlated with the prevalence of limping (Pearson correlation = 0.88; n = 9), and prevalence estimates from the 2 methods diverged most when the mean herd prevalence was lower. The SLS method provides an estimate of the prevalence of lameness in tiestall herds comparable with traditional gait scoring, but does not require that the cows be untied. The SLS method could be used to improve lameness detection on tiestall farms and obtain estimates of lameness prevalence without the need to walk the cows.     

Behavior of cows during and after peak feeding time on organic and conventional dairy farms in the United Kingdom

The behavior of groups of housed, lactating dairy cattle was observed over 2 winter housing periods on 20 organic farms and 20 conventional farms in the United Kingdom. Three methods were used: (1) 6 video-clips of 10 min duration were captured of cows feeding at sections of the feed-bunk face during the peak feeding period (0 to 90 min) and continuously observed for aggressive interactions among cows; (2) the proportion of cows at the feed-bunk face was scanned every 15 min for 4.5 h to include the peak feeding period (0 to 255 min); and (3) all nonfeeding behaviors were scanned every 15 min for 2.5 h after the peak feeding period (120 to 255 min). The latter scans were analyzed post hoc for measures of cow comfort (freestall farms only). Management and health data were collected on each farm. On farms with open-fronted feed-bunk faces, a greater number of aggressive interactions occurred at the feed-bunk face at peak feeding time on organic farms than on conventional farms (organic = 36.3 ± 4.4; conventional = 29.1 ± 3.0). Higher proportions of cows were at the feed-bunk face at peak feeding on organic farms than on conventional farms (organic = 0.58 ± 0.04; conventional = 0.48 ± 0.03). Housing type (freestall versus straw pen) explained most differences in postfeeding behavior (proportion of ruminating cow in alleyways: freestalls = 0.16 ± 0.06 vs. straw-pen = 0.08 ± 0.03), with few differences between organic and conventional herds. On freestall farms, the proportions of cows on organic farms lying down postfeeding was smaller than in conventional herds (organic = 0.38 ± 0.09 vs. conventional = 0.43 ± 0.07). Differences in behavior around peak feeding time could be associated with the reduction in food “quality” on organic farms compared with the energy requirement of the cows, with cows on organic farms being highly motivated to feed. A correlation was observed between farms that had high amounts of lying and farms that had high lameness prevalence (R² = 55.3), suggesting a complex relationship between comfort and pain. Overall, the behavior of dairy cows on organic farms was not different from that of conventionally reared cows, and the results suggest that most behavioral welfare problems relating to housing could be alleviated by management practices.     

Benchmarking cow comfort on North American freestall dairies: Lameness,leg injuries,lying time,facility design,and management for high-producing Holstein dairy cows

In this paper, we describe a novel approach to corporate involvement in on-farm assessment, driven by the desire to provide a service for dairy producers and to create a vehicle for engagement on issues of dairy cow welfare. This program provides producers with feedback on animal-based (including gait score, leg injuries, and lying time) and facility-based (including freestall design, bedding practices, feed bunk design and management, and stocking density) measures that can be used to better address their management goals. The aim of this paper is to describe variation in the prevalence of lameness and leg injuries, lying behavior, facility design, and management practices for high-producing cows on freestall dairy farms in 3 regions of North America: British Columbia (BC; n = 42); California (CA; n = 39); and the northeastern United States (NE-US; n = 40). Prevalence of clinical lameness averaged (mean ± SD) 27.9 ± 14.1% in BC, 30.8 ± 15.5% in CA, and 54.8 ± 16.7% in NE-US; prevalence of severe lameness averaged 7.1 ± 5.4% in BC, 3.6 ± 4.2% in CA, and 8.2 ± 5.6% in NE-US. Overall prevalence of hock injuries was 42.3 ± 26.2% in BC, 56.2 ± 21.6% in CA, and 81.2 ± 22.5% in NE-US; prevalence of severe injuries was 3.7 ± 5.2% in BC, 1.8 ± 3.1% in CA, 5.4 ± 5.9% in NE-US. Prevalence of swollen knees was minimal in CA (0.3 ± 0.6%) but high (23.1 ± 16.3%) in NE-US (not scored in BC). Lying times were similar across regions (11.0 ± 0.7 h/d in BC, 10.4 ± 0.8 h/d in CA, 10.6 ± 0.9 h/d in NE-US), but individual lying times among cows assessed varied (4.2 to 19.5 h/d, 3.7 to 17.5 h/d, and 2.8 to 20.5 h/d in BC, CA, and NE-US, respectively). These results showed considerable variation in lameness and leg injury prevalence as well as facility design and management among freestall farms in North America. Each of the 3 regions had farms with a very low prevalence of lameness and injuries, suggesting great opportunities for improvement on other farms within the region.     

Stocking density,milking duration,and lying times of lactating cows on Canadian freestall dairy farms

Lying time is an important measure of cow comfort, and the lying behavior of dairy cattle can now be recorded automatically with the use of accelerometers. To assess the effect that stall stocking density and the time that cows spend away from the home pen being milked has on the lying behavior of Holstein cattle, a total of 111 commercial freestall dairy farms were visited in Canada. Accelerometers were used to automatically record the lying behavior of 40 focal cows per farm. Total duration of lying, lying bout frequency, and the mean duration of lying bouts were calculated. Pen population was the total number of cows in the pen. To calculate stall stocking density (%) the number of cows in the pen and the number of useable stalls were counted and multiplied by 100, and the length × width of the pen was divided by the number of cows in the pen to calculate area/cow (m²). Time away from the pen per day was recorded from when the first cow in each pen was taken out of the home pen for milking until the last cow returned to the home pen after milking, and this time was multiplied by daily milking frequency. The median value for lying duration at the farm level was 10.6 h/d, with 10.5 lying bouts/d, and a median lying bout duration of 1.2 h. Stall stocking density ranged from 52.2 to 160.0%, with very few farms (7%) stocking at greater than 120%. Although stall stocking density was not significantly correlated with lying behavior, the results showed that no farm with stocking density greater that 100% achieved an average herd lying duration of 12 h/d or higher, whereas 21.6% of farms with a stocking density of 100% or less did achieve the target lying time of ≥12 h/d, as recommended by the Canadian Code of Practice (χ² = 4.86, degrees of freedom = 1). Area/cow (m²) was not correlated with any aspect of lying behavior, but regardless of space per cow, pen population was correlated with daily frequency and duration of lying bouts. As the number of cows in the pen increased, lying daily bout frequency increased (correlation coefficient = 0.24) and lying bout duration decreased (correlation coefficient = −0.30). Lying behavior was affected by the time the cows were away from the pen being milked. When cows were away from the pen for longer than 3.7 h/d, no farm achieved the recommended herd median lying time of 12 h/d or longer. These results suggest that providing 1 stall for each cow in the pen and minimizing time away from the pen are important factors if cattle are to achieve the recommended daily lying duration of 12 h/d.     

Short communication: Genetic variation in estrus activity traits

Genetic variation in estrus traits derived from hourly measurements by electronic activity tags was studied in an experimental herd of Holstein (n = 211), Jersey (n = 126), and Red Dane (n = 178) cows. Both virgin heifers (n = 132) and lactating cows in the first 4 parities (n = 895 cow parities) were used, giving a total of 3,284 high-activity episodes indicating estrus. The first estrus after calving was predicted to occur on average, at 39, 44, and 45 d in milk for Red Danes, Holsteins, and Jerseys, respectively. Genetic variance was detected for the trait days to first high activity with a heritability of 0.18 ± 0.07. The heritability for the period of increased activity was small (0.02 to 0.08) and of similar magnitude as that for the level of activity (0.04 to 0.08). Compared with fertility traits based on artificial insemination field data, activity traits have higher heritability than traditional fertility traits, and could therefore be helpful in selection for improved fertility.     

Treatment practices and quantification of antimicrobial drug usage in conventional and organic dairy farms in Wisconsin

The objective of this study was to develop a method to quantify antimicrobial drug usage and treatment practices on conventional and organic dairy farms that had been recruited to represent a broad spectrum of potential exposure to antimicrobial drugs. Data on disease prevalence and treatment practices of organic (n = 20) and conventional (n = 20) farms were obtained during a farm visit using a survey instrument. A standardized estimate of antimicrobial drug usage was developed using a defined daily dose (DDD) of selected compounds. Density of antimicrobial drug usage was expressed as the number of DDD per adult cow per year. Differences in prevalence and management of selected diseases between conventional and organic farms were identified. The overall estimated prevalence of selected diseases was greater for conventional farms compared with organic farms. Organic farmers reported use of a variety of nonantimicrobial compounds for treatment and prevention of disease. Conventional farmers reported that penicillin was the compound most commonly used for dry cow therapy and cephapirin was most commonly used for treatment of clinical mastitis. On conventional farms, the estimated overall exposure to antimicrobial drugs was 5.43 DDD per cow per year composed of 3.58 and 1.85 DDD of intramammary and parenteral antimicrobial drugs, respectively. Of total intramammary antimicrobial drug usage, treatment of clinical mastitis contributed 2.02 DDD compared with 1.56 DDD attributed to the use of dry cow therapy. Of total parenteral treatments, the distribution of exposure was 0.52 (dry cow therapy), 1.43 (clinical mastitis treatment), 0.39 (treatment of foot disease), 0.14 (treatment of respiratory disease), and 0.32 (treatment of metritis) DDD. For treatments of foot infections (0.33 DDD), respiratory infections (0.07 DDD), and metritis (0.19 DDD), the mean density of ceftiofur usage was significantly greater compared with other compounds.     

Herd-level risk factors for lameness in high-producing holstein cows housed in freestall barns

The objective of this study was to investigate the association of some herd-level factors with the prevalence of lameness in 53 high-production groups of Holstein cows housed on 50 commercial dairy farms having freestall barns in Minnesota. Cows in the high-production group (n = 5,626) were scored for locomotion (score of 1 to 5, where 1 = normal and 5 = severely lame) to estimate prevalence of lameness (locomotion score ≥3) in the group. Herd-level variables were used to explain the variation in prevalence among groups. Among the variables tested, herd size, pen space per cow, type and size of milking parlor, total mixed ration content of crude protein and neutral detergent fiber, feeding frequency, linear feedbunk space per cow, type of feed barrier, and use of footbath did not show any association with the prevalence of lameness in the univariate analysis screening test and were not included in the multivariate model. Pen stocking density (cows per 100 stalls), total daily distance between pen and milking parlor, number of cows per full-time employee equivalent, cud chewing index, and pen type were eliminated from the multivariate model in the backwards stepwise procedure. Daily time away from the pen for milking was positively associated with the prevalence of lameness, whereas cow comfort quotient was negatively associated with prevalence of lameness. Prevalence of lameness was greater when farms performed hoof trimming only when the manager decided cows needed it because of hoof overgrowth or lameness compared with farms on which the feet of all cows were trimmed on a maintenance schedule once or twice annually. Brisket board height of more than 15.24 cm and presence of the area behind the brisket board filled with concrete were associated with greater prevalence of lameness. Most of these herd-level factors could be managed to reduce lameness prevalence in commercial dairy farms.     

Sex-sorted semen for dairy heifers: Effects on reproductive and lactational performances

The objectives of this study were to evaluate the effects of using sex-sorted semen for first AI of heifers on health and productivity during first lactation. Holstein heifers (herd A = 227 and herd B = 1,144) received first artificial insemination (AI) with sex-sorted semen (SX; n = 343) or conventional semen (CS; n = 1,028), and all heifers that displayed estrus after first AI were reinseminated with conventional semen up to 11 times before being culled. Age at first AI was 13.1 ± 0.1 and 13.8 ± 0.1 mo for SX and CS heifers, respectively, in herd A and 12.9 ± 0.1 mo for both SX and CS heifers in herd B. Pregnancy per AI after first AI was greater for CS heifers than for SX heifers (51.8 vs. 40.2%). From heifers initially enrolled, 70.2% calved in herds A (n = 188) or B (n = 774) and first-lactation data were collected. Interval from first AI to calving was greater for SX heifers than for CS heifers (10.2 ± 0.1 vs. 9.9 ± 0.1 mo). Among heifers conceiving to first AI, SX heifers were more likely than CS heifers to deliver a female calf (85.7 vs. 47.7%), but because SX heifers were more likely to deliver a dead calf (8.8 vs. 3.4%), the difference in proportion of SX and CS heifers delivering a live female calf was smaller than expected (SX = 79.1%; CS = 47.2%). Rearing cost from first AI to calving was greater for SX heifers than for CS heifers ($775.3 ± 6.7 vs. $750.0 ± 5.9), but calf revenue tended to be greater for SX heifers ($142.0 ± 7.2 vs. $126.7 ± 6.4) and cost per female calf produced was smaller for SX heifers than for CS heifers ($−809.4 ± 10.8 vs. $−1,249.7 ± 10.9). Treatment did not affect calving difficulty, proportion of heifers needing assistance, and incidence of retained fetal membranes or metritis. Among heifers that conceived to first AI, however, SX heifers were more likely to be culled within 30 DIM (3.3 vs. 1.6%) and tended to be more likely to be culled within 60 DIM (5.5 vs. 3.4%) than CS heifers, but overall replacement cost was not different ($136.8 ± 13.4). Total milk yield (9,245.5 ± 84.7 kg) and income over feed cost ($554.7 ± 5.1) were not different. Overall economic return was greater for SX heifers than CS heifers ($−83.7 ± 36.7 vs. −175.3 ± 33.4). Use of sex-sorted semen for first insemination of virgin heifers reduced the cost per female calf produced and increased the economic return during the first lactation.     

Short communication: Comparison of 2 methods of assessing calf birth weights in dairy calves

The collection of calf birth weight on US dairies is not a common practice. Calf birth weight was collected on 3 dairies (2 Holstein herds and 1 Jersey herd) over a 6-wk period. All calf birth weights were collected less than 2 h after birth. A total of 872 calves were weighed by a spring scale and their weight was also estimated using a hoof circumference tape, with both weights and sex recorded. The general linear models procedure (PROC GLM; SAS Institute Inc., Cary, NC) was used to estimate least squares means for spring scale birth weight along with sex of the calf and dairy. Calf spring scale versus hoof circumference-estimated birth weight was compared using the regression procedure (PROC REG; SAS Institute Inc.). Calf birth weight was also broken down into increments, and spring scale versus hoof circumference-estimated birth weight was compared by t-test. Bull calves had a heavier birth weight compared with heifer calves [36.7 ± 0.4 kg (n = 450) vs. 34.6 ± 0.4 kg (n = 422), respectively]. The dairy on which calves were born had a significant effect on calf birth weight [dairy 1: 36.8 ± 0.4 kg (n = 204); dairy 2: 39.5 ± 0.2 kg (n = 463); dairy 3: 25.9 ± 0.4 kg (n = 205)]. When the spring scale calf birth weight was linearly regressed by hoof circumference-estimated birth weight, a significant relationship was observed, with an R² value of 0.91. For calves weighing less than 31.3 kg, the hoof circumference tape overestimated calf birth weight compared with the spring scale. However, for calves that weighed between 31.3 and 44.9 kg, no significant difference was observed between spring scale and hoof circumference tape-estimated birth weight. For calves weighing greater than 44.9 kg, the hoof circumference tape underestimated birth weight compared with the spring scale. Collection of calf BW by spring scale or estimated by hoof circumference tape appeared to be comparable for most calves because most calves weighed between 31 and 45 kg, but caution should be used for calves with a light or heavy birth weight.     

Evaluation of solids, nitrogen, and phosphorus excretion models for lactating dairy cows

Monitoring or accurately predicting manure quantities and nutrient concentrations is important for dairy farms facing strict environmental regulations. The objectives of this project were to determine the daily out-flow of manure nutrients from a free-stall barn using mass balance and to compare results with published excretion models. The project was conducted at the free-stall facility housing the lactating cow herd of the Virginia Tech Dairy Center in 2005. The herd consisted of 142 (±8.9) Holstein and Jersey cows with a mean body weight of 568 (±6.2) kg and average milk yield of 29.8 (±1.7) kg/d with 3.18% (±0.07) true protein and 3.81% (±0.13) milk fat on 18 sampling days. The intakes of dry matter (DM), N, and P were estimated from the formulated ration. Daily consumption averaged 21.7 (±0.27) kg of DM with 17.7% (±0.26) crude protein and 0.46% (±0.03) P. Approximately 110 (± 27.9) kg/d of sawdust was used as bedding; its contribution to manure flow was subtracted. The alleys in the free-stall barn were flushed every 6 h with recycled wastewater, and the slurry was collected. On 18 sampling days the volumes and constituents of the flushwater and the flushed manure were determined for a 6-h flush cycle and extrapolated to daily values. Net daily flow of solids and nutrients in manure were calculated as the differences between masses in flushed slurry and flushwater. Nitrogen and P excretion were also calculated from dietary inputs and milk output. The flow was compared with the American Society of Agricultural Engineers’ (ASAE) standards. Each cow produced 5.80 kg/d of total solids (remainder after drying at 105°C). The ASAE standard predicted DM (remainder after drying at 60°C) excretion of 8.02 to 8.53 kg/d per cow. Recovery of P amounted to 74.8 g/d per cow. Overall, 102% of intake P was recovered; 75.1% in the manure outflow and 26.9% in milk. About 285 g/d and 148 g/d of N per cow were recaptured in manure and milk, respectively; 182 g/d was presumably volatilized. All models of N excretion appeared to underestimate N excretion. Volatilization rate of N amounted to 18.1%/h for the 6-h flush interval. Measured outflow of manure-P from the facility was similar to excretion predictions. Presentation of excreted solids as both total solids and DM is warranted. We conclude that using excretion prediction equations is useful for predicting excretion and outflow of P in a lactating cow facility, but N excretion predictions exhibited bias and have to be used prudently for predicting N outflow and N volatilization.     

Herd-level relationship between antimicrobial use and presence or absence of antimicrobial resistance in gram-negative bovine mastitis pathogens on Canadian dairy farms

Concurrent data on antimicrobial use (AMU) and resistance are needed to contain antimicrobial resistance (AMR) in bacteria. The present study examined a herd-level association between AMU and AMR in Escherichia coli (n = 394) and Klebsiella species (n = 139) isolated from bovine intramammary infections and mastitis cases on 89 dairy farms in 4 regions of Canada [Alberta, Ontario, Québec, and Maritime Provinces (Prince Edward Island, Nova Scotia, and New Brunswick)]. Antimicrobial use data were collected using inventory of empty antimicrobial containers and antimicrobial drug use rate was calculated to quantify herd-level AMU. Minimum inhibitory concentrations (MIC) were determined using Sensititre National Antimicrobial Resistance Monitoring System (NARMS) gram-negative MIC plate (Trek Diagnostic Systems Inc., Cleveland, OH). Isolates were classified as susceptible, intermediate, or resistant. Intermediate and resistant category isolates were combined to form an AMR category, and multivariable logistic regression models were built to determine herd-level odds of AMR to tetracycline, ampicillin, cefoxitin, chloramphenicol, trimethoprim-sulfamethoxazole combination, sulfisoxazole, streptomycin and kanamycin in E. coli isolates. In the case of Klebsiella species isolates, logistic regression models were built for tetracycline and sulfisoxazole; however, no associations between AMU and AMR in Klebsiella species were observed. Ampicillin-intermediate or -resistant E. coli isolates were associated with herds that used intramammarily administered cloxacillin, penicillin-novobiocin combination, and cephapirin used for dry cow therapy [odds ratios (OR) = 26, 32, and 189, respectively], and intramammary ceftiofur administered for lactating cow therapy and systemically administered penicillin (OR = 162 and 2.7, respectively). Use of systemically administered penicillin on a dairy farm was associated with tetracycline and streptomycin-intermediate or -resistant E. coli isolates (OR = 5.6 and 2.8, respectively). Use of cephapirin and cloxacillin administered intramammarily for dry cow therapy was associated with increasing odds of having at least 1 kanamycin-intermediate or -resistant E. coli isolate at a farm (OR = 8.7 and 9.3, respectively). Use of systemically administered tetracycline and ceftiofur was associated with cefoxitin-intermediate or -resistant E. coli (OR = 0.13 and 0.16, respectively); however, the odds of a dairy herd having at least 1 cefoxitin-intermediate or -resistant E. coli isolate due to systemically administered ceftiofur increased with increasing average herd parity (OR = 3.1). Association between herd-level AMU and AMR in bovine mastitis coliforms was observed for certain antimicrobials. Differences in AMR between different barn types and geographical regions were not observed.     

Risk factors for lameness and hock injuries in Holstein herds in China

The objective was to investigate the association between herd-level management and facility design and the prevalence of lameness and hock injuries in high-producing dairy cows on commercial freestall farms in China. Housing and management measures, such as stall design, bedding type, and milking routine were collected for the high-producing pen in 34 farms in China. All cows in the pen were gait scored using a 5-point scale, and evaluated for hock injuries using a 3-point scale. Measures associated with the proportion of clinically (score ≥3) or severely (score ≥4) lame cows, and the proportion of cows having at least a minor hock injury (score ≥2) or severe injury (score = 3) at the univariable level were submitted to multivariable general linear models. The prevalence [mean ± SD (range)] of clinical and severe lameness were 31 ± 12 (7–51) and 10 ± 6% (0– 27%), respectively, and the prevalence of cows with at least a minor hock injury and with severe injuries was 40 ± 20 (6 – 95) and 5 ± 9% (0 – 50%), respectively. The prevalence of clinical lameness and severe lameness decreased with herd size (estimate = −0.35 ± 0.09% for a 100-cow increase for clinical lameness; estimate = 0.15 ± 0.06% for a 100-cow increase for severe lameness). Prevalence increased with barn age >9 yr (estimate = 12.73 ± 4.42% for clinical lameness; estimate = 5.79 ± 2.89% for severe lameness). These 2 variables combined explained 49% of the variation in clinical lameness and 30% of the variation in severe lameness. The prevalence of all hock injuries and severe hock injuries decreased with deep bedding (estimate = −20.90 ± 5.66% for all hock injuries; estimate = −3.65 ± 1.41% for severe hock injuries) and increased with barn age >9 yr (estimate = 16.68 ± 7.17% for all hock injuries; estimate = 6.95 ± 1.75% for severe injuries). These 2 variables explained 52 and 58% of the variation, respectively. In conclusion, large variation existed across farms in prevalence of lameness and hock injuries. Changes in housing and management may help control the prevalence of lameness and hock injuries in the emerging dairy industry in China.