Genome-wide association and genomic prediction for a reproductive index summarizing fertility outcomes in U.S. Holsteins

Subfertility represents one major challenge to enhancing dairy production and efficiency. Herein, we use a reproductive index (RI) expressing the predicted probability of pregnancy following artificial insemination (AI) with Illumina 778K genotypes to perform single and multi-locus genome-wide association analyses (GWAA) on 2,448 geographically diverse U.S. Holstein cows and produce genomic heritability estimates. Moreover, we use genomic best linear unbiased prediction (GBLUP) to investigate the potential utility of the RI by performing genomic predictions with cross validation. Notably, genomic heritability estimates for the U.S. Holstein RI were moderate (h2 = 0.1654 ± 0.0317-0.2550 ± 0.0348), while single and multi-locus GWAA revealed overlapping quantitative trait loci (QTL) on BTA6 and BTA29, including the known QTL for the daughter pregnancy rate (DPR) and cow conception rate (CCR). Multi-locus GWAA revealed seven additional QTL, including one on BTA7 (60 Mb) which is adjacent to a known heifer conception rate (HCR) QTL (59 Mb). Positional candidate genes for the detected QTL included male and female fertility loci (i.e. spermatogenesis and oogenesis), meiotic and mitotic regulators, and genes associated with immune response, milk yield, enhanced pregnancy rates, and the reproductive longevity pathway. Based on the proportion of the phenotypic variance explained (PVE), all detected QTL (n = 13; P ≤ 5e - 05) were estimated to have moderate (1.0% < PVE ≤ 2.0%) or small effects (PVE ≤ 1.0%) on the predicted probability of pregnancy. Genomic prediction using GBLUP with cross validation (k = 3) produced mean predictive abilities (0.1692-0.2301) and mean genomic prediction accuracies (0.4119-0.4557) that were similar to bovine health and production traits previously investigated.

Factors associated with the time and magnitude of the nadir body condition score in early lactation and its subsequent effects on fertility of Holstein cows

The objective of this study was to identify variables associated with the time and magnitude of nadir BCS (nBCS) during early lactation and to characterize the effects of these two measurements on the subsequent pregnancy at first artificial insemination (P/AI1) and pregnancy loss of Holstein cows. A retrospective observational study was completed using data collected from 12,042 lactations in 7,626 Holstein cows calving between April 2019 and January 2022 in a commercial dairy operation located in Colorado, USA. Scores generated by an automated BCS camera system at dry-off (BCSdry), calving (BCS1), nadir (nBCS; defined as the lowest daily BCS from calving to 100 DIM), and 21 d post nadir were selected for the analyses and subsequently categorized into quartiles (Q1 = lower nBCS). Changes in BCS were calculated from dry-off to calving (multiparous cows); from calving to nadir; and from nadir to 21 d post nadir and assigned into quartile categories considering Q1 as the 25% of cows with greater loss (pre nadir) or smaller gain (post nadir) of BCS. Data were examined using logistic regression, ANOVA, and time to event analyses. Initial univariable models were followed by multivariable models that considered parity category, calving season, BCS1, and average milk yield up to 30 DIM (M30) as covariables. Sick cows and high producing cows had increased DIM at nadir, while lower BCSdry, greater M30, and occurrence of disease were associated with lower nBCS. Cows that conceived at AI1 had their nBCS earlier (45.1 ± 0.32 d) than cows that remained open after first AI (46.4 ± 0.35 d). On the contrary, DIM at nBCS did not differ by pregnancy loss status. The logistic regression analyses reported smaller odds of P/AI1 in cows in the lower nBCS categories. Likewise, cows with larger loss in BCS between calving and nadir had smaller odds of P/AI1. Although cows that lost their pregnancy had lower nBCS, this association was not consistent across the analyses. The time to and magnitude of nBCS, together with the ∆BCS from calving to nadir could be useful measures to evaluate the transition and early lactation status of dairy cows.

Associations of automated body condition scores at dry-off and through early lactation with milk yield of Holstein cows

The objective of this study was to analyze the associations of body condition score (BCS) and BCS change (∆BCS) during the dry period and the first 100 d of lactation with daily milk yield. Examining the involvement of health status in the associations between BCS and milk yield was a secondary objective of this research. Data included 12,042 lactations in 7,626 Holstein cows calving between April 2019 and January 2022 in a commercial dairy operation located in Colorado, USA. BCSs were generated daily by an automated BCS camera system located at the exit of the milking parlor. The assessment points selected for this study were dry-off (BCSdry), calving (BCS1), 7 DIM (BCS7), 14 DIM (BCS14), 21 DIM (BCS21), and nadir (nBCS; defined as the lowest daily BCS from calving to 100 DIM). Subsequently, these BCS were categorized considering quartiles (Q1 = 25% lowest BCS; Q4 = 25% greatest BCS), separately for primiparous and multiparous cows. Changes in BCS were calculated from dry-off to calving (multiparous); and from calving to 7 DIM, 14 DIM, 21 DIM, and nadir and assigned into quartile categories considering Q1 as the 25% of cows with the greatest decrease of BCS. Lactations were classified based on the number of health events before nadir as healthy, affected by one event, or having multiple events. Data were examined in primiparous and multiparous cows separately using ANOVA. The least square means for daily milk at 60 DIM and 305 DIM were calculated by category of BCS and ∆BCS at multiple time points and time periods. Subsequently, lactation curves were created by BCS and ∆BCS categories and by health status. Multivariable models included calving season and BCS1 as covariables. The largest differences in milk yield among categories of BCS and ∆BCS were identified for BCS originated at nadir and for the ∆BCS between calving and nadir. The differences in average daily milk yield between cows in the lowest and the greatest nBCS category (Q1 vs. Q4) were 3.3 kg/d (60 DIM) and 3.4 kg/d (305 DIM) for primiparous cows and 2.4 kg/d (60 DIM) and 2.1 kg/d (305 DIM) for multiparous cows. During the period from calving to nadir, primiparous cows in Q1 (greatest decrease of BCS) produced 4.3 kg/d (60 DIM) and 3.8 kg/d (305 DIM) more than cows in Q4. For multiparous cows, the differences were 3.0 kg/d (60 DIM) and 1.9 kg/d (305 DIM) in favor of Q1 cows. Overall, the associations between BCS and ∆BCS categories and milk yield were not consistent across time and they depended on the parity category. Nonetheless, as the assessment of BCS and ∆BCS approached the nadir, the association between greater milk yield and lower BCS or greater reduction in BCS became more evident.

Association between body condition score fluctuations and pregnancy loss in Holstein cows

The objective of this study was to characterize the associations between body condition score (BCS) and BCS change (∆BCS), determined by an automated camera system during early lactation and close to artificial insemination (AI), and the subsequent pregnancy loss (PL) in Holstein cows. A secondary objective was to determine the impact of disease on PL, considering multiple time periods relative to AI. Data from 9,430 lactations in 6,884 Holstein cows in a commercial dairy operation located in Colorado, USA were included in this retrospective observational study. Cows were subject to first AI at about 80 DIM (primiparous) and 60 DIM (multiparous), following a double OvSynch protocol. Pregnancy diagnosis was performed via transrectal ultrasonography on day 32 ± 3 after AI and reconfirmed on day 80 ± 3 after AI. Cameras mounted on the sorting gate at each exit (n = 2) of the milking parlor generated BCS on a five-point scale with 0.1 increments. The BCS at calving (BCS1), 21 DIM (BCS21), 56 DIM (BCS56), AI resulting in pregnancy (BCSAI), and 90 d post AI (BCSAI90) were selected for the analyses and subsequently categorized as low (≤ lower quartile), moderate (interquartile range), and high (≥ upper quartile). Changes in BCS were calculated by periods of interest as change from calving to 21 DIM; change from calving to 56 DIM; change from 56 DIM to AI; and change from AI to 90 d post AI and assigned into categories to facilitate the analysis. Data were examined using logistic regression, considering parity category, season at calving and AI, DIM at AI, milk yield up to 60 DIM, and occurrence of disease as covariables. The logistic regression analyses indicated that the odds of PL were greater in cows in the low BCS category relative to cows in the high BCS category at 56 DIM (OR 95% CI = 1.41 [1.12-1.79]), AI (1.31 [1.05-1.65]), and 90 d post AI (1.38 [1.10-1.74]). Likewise, cows with large loss in BCS between calving and 21 DIM (1.46 [1.10-1.94]) and loss in BCS between AI and 90 d post AI (1.44 [1.15-1.81]) had greater odds of PL compared with cows with no loss of BCS within the same period. Occurrence of disease at all the time periods considered in the analysis had a consistent detrimental impact on maintenance of the pregnancy, supporting the concept that pre and postconceptional disease affects embryonic survival. Overall, low BCS, more pronounced reductions in BCS occurring closer to AI, and occurrence of disease resulted in greater PL in this Holstein population.

PSXII-1 CNV and Cnvr Detection from High-Density SNP Genotyping in Holstein Cattle

Copy number variation (CNV) represents an important source of genetic variation complementary to single nucleotide polymorphism (SNP) and provides valuable insights into the genetic architecture of complex traits in humans and livestock animals. However, many factors affect CNV detection, including sample size. Previous studies in Holstein cattle have only used hundreds of individuals. Therefore, in the present study, CNVs were identified from high-density genotype array data in 3,529 Holstein cows from 16 herds located in 7 U.S. states. CNVs were derived from 546,802 autosomal SNP markers with MAF &gt; 0.05 and call rate &gt; 0.90 using the intensity signals at each SNP position in a hidden Markov model implemented in PennCNV software. The log R ratio (LRR) values were corrected based on the guanine-cytosine content in the genomic regions located 500 kb upstream and downstream of each marker. After detection, CNVs presenting LRR ≤ 0.30, B allele frequency drift &lt; 0.01, waviness factor ≤ 0.05, number of SNPs &gt; 10 and length &gt; 1 kb were merged into CNV regions (CNVR) using CNVRanger. A total of 1,881 non-redundant CNV events spanning the entire genome were identified in 1,771 cows, with a mean of 10 CNVs per individual and ranging from 1 to 27. The highest percentage of CNV calls was located on BTA7 (16%), while only 9 CNVs were identified on BTA9. The CNV calls were grouped into 685 CNVRs covering 3.07% of the bovine autosomal genome. The number of CNVRs with copy loss and gain were 356 and 310, and both types were observed in 19 regions. The chromosomal distribution of CNVR revealed that BTA7 harbors 38 CNVRs, while only 2 were detected on BTA28. These results will support further research on the contribution of CNVs and CNVRs to the genetic architecture of complex traits in Holstein cattle.

Effect of a 2-step probiotic program on digestive health and performance of Holstein heifer calves

Managing the composition of the bacterial communities in the digestive tract with the use of probiotics that enhance protective microflora could result in positive effects on health and performance of calves. The objective of this study was to evaluate a 2-step probiotic program (added to colostrum and milk) on the digestive health and growth of preweaning Holstein heifers. A randomized clinical trial was conducted from July to October 2020 in a calf rearing facility in Colorado. Calves were housed in pairs sharing the same treatment in 2 polyethylene hutches within a common area of 4.50 m². A total of 232 calves were enrolled at birth and randomly allocated into 2 treatment groups [control (CTR) = 116; treatment (PB) = 116] and followed until weaning (64 ± 3 d). Treatment consisted of 2 formulations of a multistrain bacterial-based probiotic added in colostrum (PBF1) and milk (PBF2). Treatment calves received 2 g of PBF1 added to each colostrum feeding, and 1 g of PBF2 added to the milk at the morning feeding 3 times per week up to weaning. Calf weight was collected at birth, at 30 d of age, and at weaning. Serum total protein was determined at age 3 ± 1 d and a health assessment was completed 3 times per week. Statistical analyses were performed using SAS, with calf considered the experimental unit clustered by housing pair. Cox proportional hazard analysis and time to event analysis were used to compare time to the first diarrhea event and time to recovery between treatment groups. The total number of diarrhea events and culling were assessed by Poisson regression and logistic regression analysis, respectively. Linear regression was performed to evaluate differences in average daily gain by treatment group. Overall, the mean (± standard error) temperature humidity index (THI) was 75 (± 0.44) units during the study period, which resulted in continuous exposure to heat stress in the day hours. No difference between treatment groups was observed in serum total protein. The overall incidence of diarrhea was 96.6% (CTR = 99%, PB = 95%); no differences were determined in the hazard of a first diarrhea episode or in the median time to the first diarrhea event (11 d in both groups). Similarly, no differences were found in the likelihood of recovery or in the median time to recovery from diarrhea (7 d in both groups). Likewise, treatment group was not associated with the number of diarrhea events, mean (± standard error, g/d) average daily gain from birth to weaning [CTR = 562.5 (13.9); PB = 570.8 (13.5)], or with the odds of culling. The most prevalent pathogen isolated from feces was Clostridium, which tended to be more frequent in CTR calves than PB calves. In conclusion, the probiotic program did not affect the incidence of enteric disease or the growth of preweaning heifer calves.

Evaluation of Contamination in Milk Samples Pooled From Independently Collected Quarters Within a Laboratory Setting

The primary objective of this observational study was to evaluate the prevalence of contamination from independently collected quarter-level milk samples pooled in a laboratory and subjected to bacterial culture. To address this objective, weekly quarter-level milk samples were collected longitudinally from a cohort of 503 primiparous cows from five organic dairy farms during the first 5 weeks after calving. Individual quarter milk samples were pooled in a laboratory using aseptic technique (“lab-pooled”) and subjected to bacterial culture. In the sample set of 2,006 lab-pooled milk samples, 207 (10.3%) were classified as contaminated using a standard definition (i.e., growth of three or more distinct microorganisms). Subsequent culturing of corresponding quarter-level milk samples revealed that many of the contaminated lab-pooled sample results (i.e., 46.7%) were the result of intramammary infections with different pathogens across the quarters, rather than actual contamination within any single quarter (i.e., “true contamination”). The odds of true contamination were lower when the lab-pooled sample exhibited growth of three microorganisms compared to more than 3 microorganisms. Our findings suggest that pooling of quarter samples within a laboratory setting may yield lower rates of contamination compared to those previously reported from samples composited on-farm, but that current cut-offs to define contamination may need to be evaluated for use with lab-pooled samples. Further investigation of use of lab-pooled samples may be warranted to reduce costs while still providing useful scientific insight.

Effect of peripartal administration of mycobacterium cell wall fraction on health and fertility of Holstein cows under organic-certified management

The main objective of this study was to evaluate the effect of peripartal administration of a commercially available nonspecific immune stimulant (mycobacterium cell wall fraction; MCWF [Amplimune, NovaVive Inc., Napanee, ON, Canada]) on the incidence of disease during early lactation and subsequent fertility of dairy cows. A second objective was to characterize the dynamics of circulating white blood cells (WBC) and metabolic markers following treatment administration. Cows in an United States Department of Agriculture (USDA) organic-certified dairy herd were blocked by parity and, based on sequential calving dates, randomly assigned to receive two injections (5 mL s.c.) of either a placebo (saline solution) as a control (CON; n = 71) or MCWF (n = 65) at enrollment (7 d before expected calving) and within 24 h after calving. Blood samples were collected from a subsample of the study population (MCWF = 16; CON = 18) for WBC count at enrollment, at day 2 post enrollment, and at days 1, 3, 7, and 14 after calving. Serum fatty acids, beta-hydroxybutyrate, and Ca concentrations were determined at days 1 and 7 postpartum (MCWF = 21; CON = 21). Main outcome variables included incidence risk of peripartal and early lactation health disorders and pregnancy at first artificial insemination (AI), at 100, and at 150 days in milk (DIM). In addition, the average daily milk yield up to 90 DIM and death and live culling before 305 DIM were compared. Treatment effects were assessed using multivariable logistic regression, time-to-event analyses, and repeated measures analysis of variance (ANOVA). A treatment effect on the incidence risk of some of the health disorders in the study was established. Incidence risk of metritis and clinical mastitis <28 DIM was smaller in MCWF than in CON cows (36.9% vs. 50.7% and 6.3% vs. 19.7%, respectively). On the contrary, the incidence risk of respiratory disease <28 DIM was smaller in CON (0%) than in MCWF (7.7%). Reproductive performance of multiparous cows was affected by MCWF administration: pregnancy at first AI and pregnancy at 100 and 150 DIM were greater in MCWF than in CON (35.6% vs. 19.2%; 51.1% vs. 25.0%; and 64.4% vs. 40.4%, respectively). Overall, median intervals from calving to pregnancy were 90 vs. 121 d in MCWF and CON cows, respectively. No treatment effects on the dynamics of circulating WBC or in postpartum metabolic status were established. No differences for milk yield or for the proportion of cows that survived up to 305 DIM were determined, although cows in MCWF left the herd earlier than cows in CON. In conclusion, incidence risks of metritis and mastitis in early lactation were smaller in cows receiving MCWF, whereas the incidence risk of respiratory disease was smaller in CON. Fertility significantly improved in MCWF compared with CON cows. As this study was performed in an organic-certified dairy, specific health and reproductive management practices may affect the external validity of the current findings.

Current attitudes of veterinarians and producers regarding the use of local and systemic analgesia in beef and dairy cattle in the United States

OBJECTIVE

To survey cattle producers and veterinarians about the use of analgesia on US cattle operations.

SAMPLE

1,187 members of the following database, electronic mailing lists, and social media groups: FarmProgress master file, American Association of Bovine Practitioners, Academy of Veterinary Consultants, National Milk Producers Federation Farm Evaluators, Dairy Moms Facebook group, and Dairy Girl Network Facebook group.

PROCEDURES

An online survey was developed to gather information about the frequency of local and systemic analgesia use for common painful procedures and diseases in cattle < 2, 2 to 12, and > 12 months old. Respondents also rated their extent of agreement with each of 10 statements related to pain management in cattle. The survey was available from June 11 to August 10, 2018. Descriptive data were generated. Logistic regression was used for comparisons among cattle age groups and respondents on the basis of their industry role.

RESULTS

In general, frequency of analgesia use increased as cattle age increased, regardless of the procedure or disease. The odds of analgesia use were lower for men, compared with women, and greater for veterinarians, compared with producers. Many respondents indicated they were cognizant of the benefits of analgesia use in cattle but perceived federal regulations and drug costs as impediments to the implementation of pain mitigation protocols on cattle operations.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provided insight into current perceptions and use of analgesia in cattle, which can be used to guide implementation of pain mitigation protocols on US beef and dairy cattle operations.

Incidence and risk factors for reproductive disorders in organic certified dairies

The objective was to determine the lactational incidence risks of reproductive disorders (RD) including dystocia (DYS), retained fetal membranes (RFM), puerperal metritis (PM), clinical endometritis (CE), pyometra (PYO), late pregnancy loss (LPL), and culling due to reproductive reasons (CRR) in large organic certified dairies with predominant use of Holstein genetics. In addition, potential risk factors for RD, including parity category, milk yield in the previous lactation, season of dry-off, access to grazing at dry-off, length of the dry period (DPL), length of the close-up period (CUPL), calculated gestation length (CGL), season of calving, access to grazing at calving, concurrent health conditions, and total number of artificial inseminations were analyzed. A retrospective study was performed using information from 8 organic certified herds located in northern Colorado and west Texas, ranging from 900 to 6,000 milking cows. Cow information consisted of finalized lactations starting with calvings occurring between January 1, 2016, and December 31, 2018. Data were analyzed using time-to-event analyses and multivariable logistic regression. Clinical endometritis had the greatest lactational incidence risk (incidence risk = 10.1%; 95% CI = 9.8-10.3%), followed by DYS (8.8%; 8.5-9.1%), PM (4.9%; 4.7-5.1%), PYO (4.0%; 3.8-4.1%), LPL (3.6%; 3.4-3.7%), and RFM (2.0%; 1.8-2.1%). The incidence risk of CRR was 7.5% (7.3-8.7%), representing 29.1% (28.4-30.0%) of all culling reasons. Median time from calving to diagnosis of PM, CE, PYO, and LPL were 6, 23, 111, and 228 d, respectively. Median time for CRR was 391 d. The main risk factors for RD were DPL, CGL, and CUPL. Season of dry-off was a risk factor for RFM, PM, CE, LPL, and PYO. Short DPL (<30 d) was associated with increased odds (95% CI) of RFM [2.1 (1.6-2.7)], PM [1.4 (1.2-1.7)], and LPL [2.5 (1.5-4.2)]. Shortened CGL (<270 d) increased the odds of DYS [1.5 (1.3-1.8)], RFM [3.2 (2.4-4.1)], and PM [2.4 (1.7-3.3)], whereas extended CGL (>285 d) increased the odds of DYS [1.5 (1.4-1.7)], PM [1.5 (1.2-2.0)], CE [1.5 (1.1-2.0)], and CRR [1.2 (1.10-1.4)]. Shortened CUPL was associated with increased odds of all the RD. Cows spending less than 7 d in the close-up groups had greater odds of DYS [1.4 (1.1-1.8)], RFM [2.1 (1.8-2.4)], PM [1.9 (1.6-2.1)], PYO [1.5 (1.2-1.8)], LPL [2 (1.7-2.3)], and CRR [1.4 (1.04-1.8)] compared with cows spending more than 14 d in the close-up group. Season of calving was associated with the odds of PM [summer = 1.13 (1.01-1.2)], PYO [summer = 1.7 (1.1-2.5)], and LPL ([fall = 0.8 (0.6-0.96)] compared with winter calving. Other risk factors affecting RD were parity number, total number of artificial inseminations, and concurrent health conditions. Overall, lactational incidence risks of reproductive diseases were comparable with those reported in conventional herds. The identified risk factors for RD open opportunities for interventions, especially focused in precalving management, estimation of due dates, and closer monitoring of pregnancies from natural services in large organic certified dairy herds.

A randomized controlled clinical trial on the effect of acupuncture therapy in dairy cows affected by pyometra

Pyometra (PYO) is a reproductive disease characterized by the accumulation of purulent or mucopurulent material within the uterine lumen, in the presence of an active corpus luteum (CL). As the CL continues secreting progesterone, PYO would develop following endometritis. Due to prohibited use of artificial luteolytic hormones in US certified organic dairies, conventional therapies consisting of administration of prostaglandin F2α, are not applicable. The objective of this study was to evaluate the efficacy of two acupuncture procedures on the treatment of persistent CL in cows with PYO. We hypothesized that acupuncture would reduce CL diameter and serum progesterone (P4) concentrations, leading to regression of PYO. Holstein cows with PYO, at an USDA certified organic dairy farm in Northern Colorado, were enrolled in a randomized controlled clinical trial and assigned to 1 of 3 treatments: (1) control pyometra (CP; no treatment; n = 17); (2) electroacupuncture (EAP; n = 15); and (3) laser acupuncture (LAP; n = 15). Each cow received three 9-min (EAP) or 20-min (LAP) acupuncture sessions in alternate days. All study cows had blood samples collected for determination of serum progesterone concentration at d0, and at d2, d4, d11, d18, and d25 after first treatment. The ovaries were scanned by transrectal ultrasonography at -3d, d0, d2, d4, d11, and d18 to determine the diameter of the CL. The effect of treatment in the outcome variables was evaluated by ANOVA and by repeated measures analyses, accounting for baseline data (CL diameter and progesterone serum concentration). Average ± SE change in CL diameter from d0 to d18 were 0.94 ± 1.0 mm, 0 ± 1.0 mm, and - 0.33 ± 1.0 mm for CP, EAP, and LAP, respectively. The repeated measures analysis indicated no significant differences for CL diameter among groups. None of the study cows had serum progesterone values <1 ng/ml by the end of the monitoring period (d25) and average ± SE change from d0 to d25 were - 4.0 ± 1.97 ng/ml, -0.76 ± 2.1 ng/ml, and 3.24 ± 1.9 ng/ml for CP, EAP, and LAP, respectively. The repeated measures analysis indicated no significant differences for serum progesterone concentrations among groups. On farm cow records reviewed 150 d after treatment indicated that 2 cows in EAP and 1 cow in LAP conceived 38 d, 68 d, and 38 d, after treatment completion. In conclusion, acupuncture was not an effective treatment for persistent CL in cows with PYO, during the monitoring period.

Efficacy of non-antibiotic treatment options for digital dermatitis on an organic dairy farm

The objective of this study was to evaluate the efficacy of two non-antibiotic treatment options for digital dermatitis (DD) on an organic certified dairy farm. A randomized clinical trial was conducted using 70 multiparous Holstein cows with an early DD lesion at a USDA certified organic dairy farm in Northern Colorado, USA. Cows were enrolled in the study based on the presence of early DD lesions (scores M1 and M2) and randomly assigned to one of three treatments: (1) topical application of copper sulfate and iodine (CUI); (2) topical application of honey and iodine (HOI); and (3) control subject to no treatment (CON). Cows were evaluated at enrolment and on days 3, 12, 28, and 120 post treatment for pain and lesion size and received a locomotion and a lesion score. Cure was defined as the transition from active to non-active stages (M1/M2 to M0 or M4). The formulations had variable effects on the treatment of DD. The cure rate was numerically higher for CUI on all follow up days. The proportion of cows experiencing pain on d3 after treatment was greater in CON, followed by HOI and CUI. However, this proportion increased in HOI during the follow up period. The CUI group had a greater reduction in lesion size and larger lesions persisted in HOI. Non-antibiotic treatment formulations were partially effective in the treatment of DD in organic dairy cows: The two non-antibiotic formulations resulted in an earlier transition to mature lesions compared with the control group. The CUI combination was the most effective treatment in reducing lesion size, pain, and lameness in affected cows. However, this combination had short-term efficacy, which did not persist throughout the duration of the study. The HOI combination produced only transient reduction in lesion size.

Relationships among quarter milk leukocyte proportions and cow and quarter-level variables under different intramammary infection statuses

The use of milk leukocyte differential (MLD) test has been proposed as a complement to somatic cell count (SCC) to assess the presence and the severity of intramammary infection. However, detailed information regarding the behavior of MLD under different physiological or pathological stages of the cow is nonexistent. The objective was to analyze the association between milk leukocyte proportions provided by a commercial automated MLD test and multiple cow and quarter-level variables. The study population consisted of 104 Holstein cows (32 primiparous and 72 multiparous) in one farm. Cows were categorized by days in milk as early (<50 DIM; n=29), middle (50–250 DIM; n=25), and late lactation (>250 DIM; n = 50). Milk from 416 quarters was collected and analyzed for lymphocytes (LYM), neutrophils (NEU), and macrophages (MAC) counts using an automated milk fluorescence microscopy system. Concurrently, a sterile composite milk sample was collected from each cow for pathogen identification through microbiological culture. Culture results were classified as no growth (NOG), gram-negative (GN), gram-positive (GP), or other (OTH). Milk leukocyte proportions varied depending on the level of total leukocyte counts (TLC; P < 0.001). Similarly, leukocyte ratios (NEU:LYM, NEU:MAC, and phagocyte:LYM) were different for multiple TLC categories (P < 0.05). There was no association between parity number and MLD; however, cows in early lactation had the greatest proportions of NEU and LYM. Leukocyte ratios varied depending on parity number and stage of lactation. Cows in the medium milk-yield category had the smallest proportions of NEU and LYM, and there was significant variation in leukocyte ratios, depending on the level of milk yield. In healthy quarters, MLD were not associated with quarter position; however, the NEU:MAC ratio was greater in rear quarters than in front quarters. In quarters with TLC >100,000, NEU% was greater in rear quarters than in front quarters (P = 0.03). For quarters with pathogen growth, TLC was greatest for GN followed by OTH and GP (P < 0.001). Milk LD depended on the isolated pathogen group, although the magnitudes of the differences were small. Although the changes in the proportions of leukocytes in milk were associated with categories of TLC, levels of milk yield, and mastitis-causing pathogen groups, the deviations were small in magnitude. Additional research is necessary to determine the potential applications for this methodology.

Evaluation of milk components as diagnostic indicators for rumen indigestion in dairy cows

OBJECTIVE To identify milk component alterations that might be useful for detecting cows with rumen indigestion. DESIGN Prospective case-control study. ANIMALS 23 Holstein cows with rumen indigestion (cases) and 33 healthy cohorts (controls) from 1 herd. PROCEDURES Cases were defined as cows between 30 and 300 days postpartum with a > 10% decrease in milk yield for 2 consecutive milkings or > 20% decrease in milk yield from the 10-day rolling mean during any milking, abnormally decreased rumen motility, and no other abnormalities. Each case was matched with 2 healthy cows (controls) on the basis of pen, parity, days postpartum, and mean milk yield. Some cows were controls for multiple cases. All cows underwent a physical examination and collection of a rumen fluid sample for pH measurement at study enrollment. Individual-cow milk yield and milk component data were obtained for the 16 milkings before and after study enrollment. Rumen motility and pH and milk components were compared between cases and controls. RESULTS Rumen motility for cases was decreased from that of controls. Cases had an abrupt increase in milk fat percentage and the milk fat-to-lactose ratio during the 2 milkings immediately before diagnosis of rumen indigestion. Receiver operating characteristic analyses revealed that a 10% increase in the milk fat-to-lactose ratio had the highest combined sensitivity (57%) and specificity (85%) for identifying cows with rumen indigestion. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that a positive deviation in the milk fat-to-lactose ratio might be useful for identifying cows with rumen indigestion.

Effect of housing type on health and performance of preweaned dairy calves during summer in Florida

The objective was to evaluate the effect of housing type on health and performance of preweaned dairy calves. One hundred calves, Holsteins (HO) or Holstein-Jersey crosses (HJ), were randomly assigned to a Calf-Tel (L. T. Hampel Corp., Germantown, WI) polyethylene hutch exposed to direct sun light (n=25 for both HO and HJ) or a wire hutch with a plywood shade located under trees (n=24 and 26 for HO and HJ, respectively). Calf rectal temperature, respiratory rate, health scores, and weaning weight were compared by housing type. Rectal temperatures were higher in calves in Calf-Tel hutches compared with calves in wire hutches at 1500 h, at 40.1±0.28 and 39.1±0.22°C, respectively. Similarly, respiratory rates were higher in calves in Calf-Tel hutches compared with calves in wire hutches at 1500 h, at 90±15 and 65±10 breaths per minute, respectively. Frequencies of calves presenting abnormal ear scores did not differ between calves in Calf-Tel or wire hutches. Abnormal eye scores were less likely to occur for calves in the wire hutches. Frequencies of calves with signs of respiratory disease, such as nasal discharge and coughing, were higher in the wire hutches compared with the Calf-Tel hutches. No differences were noted in the incidence and time of first diarrhea event in calves between hutch types. Calves in wire hutches had 5.47 greater odds of receiving veterinary treatment compared with calves in the Calf-Tel hutches. Weaning weights were not different for calves in Calf-Tel or in wire hutches. The lower frequency of calves with abnormal health scores and receiving veterinary treatment in Calf-Tel hutches and the lack of difference in weight gain suggests that this housing system adapted well to the specific environmental conditions of this study.

Lymphatic fluid for the detection of Mycobacterium avium subsp. paratuberculosis in cows by PCR, compared to fecal sampling and detection of antibodies in blood and milk

Johne's disease (JD), caused by Mycobacterium avium subsp. paratuberculosis (MAP), can cause considerable economic losses in affected herds. Early diagnosis of JD is hampered by the chronic nature of the disease with a slow subclincal progression. The aim of the present study was to challenge the hypothesis that lymphatic fluid is of diagnostic value in the early stages of the disease. Lymphatic fluid from 122 animals was collected and tested for MAP by nested PCR for IS900 and compared to the results of testing for MAP in feces (culture), blood and milk (ELISA) in 110 of these samples. MAP was detected by PCR in 27.1% of the lymph samples. Agreement between the tests was poor: 6.9% of the lymph positive cows were also positive in all other tests applied, and 69.0% had negative results in fecal culture, blood and milk ELISA. Resampling of 25 cows after 8 to 12 and 16 to 20 months revealed 20.0% lymph positive animals at the first, 5.5% at the second and 27.8% at the third sampling, respectively. Only one cow showed positive lymph-PCR results at more than one sampling date. Lymph-positive cows had a 7.2 times greater likelihood of being culled within 8 to 12 months after sampling, compared to negative cows, mainly due to other health issues than JD. It can be concluded, that lymphatic fluid might be promising for the detection of early MAP-infection in cows, but further studies to elucidate the potential of this diagnostic approach are needed.

Dynamics of culling for Jersey, Holstein, and Jersey × Holstein crossbred cows in large multibreed dairy herds

The objective of this observational study was to describe and compare the dynamics of reason-specific culling risk for the genetic groups Jerseys (JE), Holsteins (HO), and Jersey × Holstein crossbreds (JH), considering parity, stage of lactation, and milk yield, among other variables, in large multibreed dairy herds in Texas. The secondary objective was to analyze the association between survival and management factors, such as breeding and replacement policies, type of facilities, and use of cooling systems. After edits, available data included 202,384 lactations in 16 herds, ranging from 407 to 8,773 cows calving per year during the study period from 2007 to 2011. The distribution of lactation records by genetic group was 58, 36, and 6% for HO, JE, and JH crosses, respectively. Overall culling rates across breeds were 30.1, 32.1, and 35.0% for JH, JE, and HO, respectively. The dynamics of reason-specific culling were dependent on genetic group, parity, stage of lactation, milk yield, and herd characteristics. Early lactation was a critical period for "died" and "injury-sick" culling. The risk increased with days after calving for "breeding" and, in the case of HO, "low production" culling. Open cows had a 3.5 to 4.6 times greater risk for overall culling compared with pregnant cows. The odds of culling with reason "died" within the first 60 d in milk (DIM) were not significantly associated with genetic group. However, both JE and JH crosses had lower odds of live culling within the first 60 DIM compared with HO cows (OR=0.72 and 0.82, respectively). Other cow variables significantly associated with the risk of dying within the first 60 DIM were cow relative 305-d mature equivalent (305ME) milk yield, parity, and season of calving. Significant herd-related variables for death included herd size and origin of replacements. In addition to genetic group, the risk of live culling within 60 DIM was associated with cow-relative 305ME milk yield, parity, and season of calving. Significant herd-related variables for live culling included herd-relative 305ME milk yield, herd size, type of facility, origin of replacement, and type of maternity. Overall, reason-specific culling followed similar patterns across DIM in the 3 genetic groups.

Effects of 35% corn wet distillers grains plus solubles in steam-flaked and dry-rolled corn-based finishing diets on animal performance, carcass characteristics, beef fatty acid composition, and sensory attributes

Fifty-four individually-fed Hereford-Angus cross steers (initial BW = 308 ± 9 kg) were used in an unbalanced randomized block design with a 2 × 2 factorial treatment arrangement to determine effects of corn processing method and corn wet distillers grains plus solubles (WDGS) inclusion in finishing diets on animal performance, carcass and beef characteristics, and sensory attributes. Dietary treatments included steam-flaked corn- (SFC) and dry-rolled corn (DRC)-based finishing diets containing 0 or 35% WDGS (DM basis; 0SFC and 35SFC, 0DRC and 35DRC, respectively). Yellow grease was used to equilibrate fat content of diets. Steers were fed 174 d, and were harvested on a single date when the mean ultrasound fat thickness was estimated to be 1.30 cm. No interactions between corn processing and WDGS were observed for performance or carcass characteristics (P ≥ 0.11). Final BW (556 ± 14 kg) and ADG (1.43 ± 0.06 kg) were not affected (P ≥ 0.25) by dietary treatment. Steers fed SFC-based diets consumed less feed, and were 10.6% more efficient (P < 0.01) than those fed DRC-based diets. Including WDGS in finishing diets improved feed efficiency of steers consuming both SFC- and DRC-based diets (P ≤ 0.04). Dietary treatment did not affect HCW, dressing percentage, fat thickness, or yield grade (P ≥ 0.27). Including WDGS in finishing diets decreased the concentration of 16:1cis-9, 18:1cis-9, and 18:1cis-11 fatty acids, and tended (P ≤ 0.10) to increase total fat concentration of steaks compared with diets without WDGS. A corn processing method by WDGS interaction was detected for 18:1trans-11 where steaks from 0DRC diets had decreased concentrations compared with other diets. There were no dietary effects on palatability attributes (P > 0.20). Livery-organy aromatics (P = 0.03) and sweet basic tastes (P = 0.01) in steaks from the 35SFC treatment were more intense than in other treatments, but were barely detectable. Thiobarbituric acid reactive substances tended to be greater in steaks from steers fed WDGS after 5 d of storage (P = 0.10), and were greater after 7 d. (P < 0.01). Inclusion of WDGS used in this experiment improved G:F with minimal impacts on carcass characteristics. Both WDGS inclusion and corn processing method impacted fatty acid composition. However, diet had minimal impacts on palatability attributes. When compared with diets fat-equilibrated with yellow grease, the primary concern with incorporating WDGS appears to be decreased shelf-life after 5 d of storage.

Events occurring during the previous lactation, the dry period, and peripartum as risk factors for early lactation mastitis in cows receiving 2 different intramammary dry cow therapies

The objective of this study was to investigate the association between mastitis events occurring during the previous lactation, the dry period, and the peripartum period on the incidence of early lactation mastitis in cows receiving ceftiofur hydrochloride or penicillin dihydrostreptomycin as intramammary dry cow antibiotic therapy. Cows (n=402) from 2 large dairy farms in Central Florida were enrolled in the study at the time of dry-off processing and were randomly assigned to 1 of 2 dry cow therapies: ceftiofur hydrochloride or penicillin dihydrostreptomycin. Composite milk samples were collected at dry-off and after calving for bacteriological examination and somatic cell count. Peripartal health disorders were monitored during the first 30 d of lactation and included calving difficulty, metritis, ketosis, and left displaced abomasum. Milk production and individual somatic cell scores (SCS) were recorded monthly by the Dairy Herd Improvement Association. The main outcome variables were the risk of clinical mastitis during the first 30 and 60 d of lactation, and the risk of subclinical mastitis at the first 2 monthly Dairy Herd Improvement Association tests after calving (up to 70 d in milk). Additionally, the SCS and the presence of mastitis pathogens in milk at dry-off and at calving were analyzed. Explanatory variables consisted of events occurring during the previous lactation, at dry-off and during the dry period, at calving, and within the first 30 d after calving. Multiple events occurring during the previous lactation had a significant effect on the incidence of mastitis in the subsequent lactation. These events included low milk yield, intermediate lactation length, clinical mastitis, and lactation SCS average. Similarly, intramammary infections with environmental bacteria at dry-off increased the chances of clinical mastitis the first month after calving. Dry-off therapy had a significant effect on mastitis incidence; cows treated with ceftiofur hydrochloride had lower odds of having clinical and subclinical mastitis in the subsequent early lactation compared with cows treated with penicillin dihydrostreptomycin.

The collection of lymphatic fluid from the bovine udder and its use for the detection of Mycobacterium avium subsp. paratuberculosis in the cow

The objective of the current study was to evaluate the feasibility of lymph collection from the bovine udder and to investigate if the lymphatic fluid might be of diagnostic value in cows infected with Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of paratuberculosis. Lymph fluid collection was attempted from 58 cows, and the reactions of the cows as well as the level of difficulty of the procedure were recorded in 56 animals. Lymph samples (51 in total) were tested for the presence of MAP by nested polymerase chain reaction. Collection of the lymphatic fluid caused no or mild signs of discomfort in 94.6% of the cows; in 51.8% of cows, lymphatic fluid was attained on the first attempt, while sample collection was unsuccessful in 12.1%. Mycobacterium avium subsp. paratuberculosis was detected in 43.1% of all lymph samples. The bacterium was present in 66.7% of cows with clinical Johne’s disease, in 42.8% of asymptomatic cows with a positive or suspicious enzyme-linked immunosorbent assay (ELISA) result in blood, and in 38.7% of cows with a negative ELISA result in blood. The present study shows that the procedure was well tolerated by most cows and can easily be performed on farm. The current report of the isolation of MAP from lymph fluid suggests that the present approach could be used for the early detection of Johne’s disease in cattle.

Effect of days to conception in the previous lactation on the risk of death and live culling around calving

The objective was to quantify the effect of days to conception (days open) in the previous parity on the risk of death and live culling (excluding the disposal reasons "dairy purposes" and "death") in the proximity of a subsequent calving in Holstein cows enrolled in the Dairy Herd Improvement program. After edits, 2,075,834 observations of cows calving between 2001 and 2007 in herds located in 36 US states primarily east of the Mississippi river were available. The period at risk included the time between 14 d before expected calving to 60 d after calving. Days open were categorized in 6 periods: 0 to 45 d, 46 to 90 d, 91 to 150 d, 151 to 210 d, 211 to 300 d, and 301 to 600 d after calving in the previous parity. Other variables of interest included parity, length of the dry period before calving, relative last test-day milk yield before dry off before calving, season of calving, and the cow's relative 305-d mature equivalent (305ME) milk yield before calving. Control variables were calving year, herd size, and relative herd 305ME milk yield. All variables were categorized. Generalized mixed models were used and included herd as random effect. Interactions between days open and the variables of interest were included in the models. Least squares means for the risk of death between -14 and 60 d after calving were 2.5, 2.5, 2.9, 3.6, 4.4, and 5.8% for increasing categories of days open. Similarly, for the same categories, least squares means for the risk of live culling were 4.5, 5.0, 5.4, 6.1, 6.9, and 8.1%. The effect of days open on the risk of death was slightly greater for third-parity cows, for long dry periods, for cows with low test-day milk yield before dry off before calving, for spring calvings, and for intermediate relative 305ME milk yield before calving. Similar trends for these interactions were found for the risk of live culling, except for relative 305ME milk yield before calving, where the effect of days open was more pronounced for high-producing cows. In conclusion, increased days open in the previous parity were associated with a greater risk of death and live culling around calving.

Candidate gene polymorphisms (BoIFNG, TLR4, SLC11A1) as risk factors for paratuberculosis infection in cattle

Paratuberculosis (Johne's disease) imposes a significant problem to the world dairy and beef industries and today is considered a potential zoonosis. The disease is caused by Mycobacterium avium subsp. paratuberculosis and is characterized by progressive weight loss and profuse diarrhoea. Susceptibility to infection is suspected to have a genetic component, and moderated values for heritability of infection have been reported. Interferon gamma is an inducible cytokine with a crucial role in the innate host response to intracellular bacteria. Toll-like receptors are trans-membrane structures responsible for coordination of innate and adaptive immune responses. The solute carrier family 11 member 1 (SLC11A1, formerly NRAMP1) gene plays an important role in innate immunity, preventing bacterial growth in macrophages during the initial stages of infection. The objective of this candidate gene case-control study was to characterize the distribution of polymorphisms in three candidate genes related to the immune function; interferon gamma (BoIFNG), toll-like receptor 4 (TLR4), and SLC11A1 genes and to test their role as potential risk factors for paratuberculosis infection in cattle. The statistical analysis demonstrated significant differences in allelic frequencies between cases and controls for BoIFNG-SNP(1)2781 and SLC11A1 microsatellites, indicating a significant association between infection and variant alleles. In the analysis of genotypes, a significant association was also found between infection status and BoIFNG-SNP(1)2781 and SLC11A1-275-279-281 microsatellites. However, when variables such as breed and age were included in the multivariate logistic regression analysis, a tendency toward statistical significance for the effect of polymorphisms in the odds of infection was only found for alleles SLC11A1-275 and 279.

Association among results of serum ELISA, faecal culture and nested PCR on milk, blood and faeces for the detection of paratuberculosis in dairy cows

Paratuberculosis is a chronic, infectious disease of ruminants that entails a serious concern for the cattle industry. One of the main issues relates to the efficiency of diagnosis of subclinically infected animals. The objective of this field study was to analyse the association among results of a serum enzyme-linked immunosorbent assays (ELISA), faecal culture and nested PCR tests on milk, blood and faeces for Mycobacterium avium subsp. paratuberculosis detection in dairy cows. Faeces, blood and milk samples were collected from 328 lactating dairy cows in four known infected herds. Results were analysed to determine associations and levels of agreement between pairs of tests. A total of 61 animals (18.6%) tested positive when all the tests were interpreted in parallel. The agreement between results in different pairs of tests was poor, slight and fair in two, five and three of the 10 possible combinations respectively. Faecal culture and faecal polymerase chain reaction (PCR) resulted in the highest kappa coefficient (0.39; fair agreement), with the lowest agreement being for ELISA and blood PCR (-0.036; poor agreement). Fisher's exact test resulted in statistically significant associations (P < or = 0.05) between the following test pairs: ELISA : faecal culture; ELISA : faecal PCR; milk PCR : faecal PCR, blood PCR : faecal PCR and faecal culture : faecal PCR. Enzyme-linked immunosorbent assays showed the highest complementary sensitivity values for all the possible two-test combinations, followed by faecal PCR. The combined use of ELISA and faecal PCR has the potential to increase the overall sensitivity for the diagnosis of paratuberculosis infection.