P. Melendez

The association between lameness, ovarian cysts and fertility in lactating dairy cows

The objective of this observational study was to evaluate the association between lameness, ovarian cysts, and fertility in lactating dairy cows. Data analysis of historical records from a 3000 Holstein farm was conducted. Sixty-five cows that became lame within 30 days postpartum were used as cases, and 130 nonlame cows served as controls. The outcome variables were incidence of ovarian cysts (OC, %), conception rate at first service (CRFS, %), overall pregnancy rate (PR, %), and calving to first service interval (CFSI, day), Incidence of OC and CRFS were analyzed by logistic regression, PR by survival analysis and CFSI by ANOVA. Lame cows had a lower CRFS (17.5% versus 42.6%) and higher incidence of OC (25.0% versus 11.1%) than controls (P<or=0.05). Calving to first service interval was not different between lame and control cows (P>0.05). There was a multicollinearity relationship between lameness and ovarian cysts. The results show that cows that became lame within the first 30 days postpartum were associated with a higher incidence of ovarian cysts, a lower likelihood of pregnancy, and lower fertility than control cows. Because this is an observational study it is not possible to conclude a cause-effect relationship.

Association between CARD15/NOD2 gene polymorphisms and paratuberculosis infection in cattle

Paratuberculosis represents a major problem in farmed ruminants and at the present is considered a potential zoonosis. The disease is caused by Mycobacterium avium subsp. paratuberculosis, and susceptibility to infection is suspected to have a genetic component. Caspase recruitment domain 15 (CARD15) gene encodes for a cytosolic protein implicated in bacterial recognition during innate immunity. Crohns disease (CD) is an idiopathic inflammatory bowel disease in humans comparable in many features to bovine paratuberculosis involving an abnormal mucosal immune response. The association between mutations in the CARD15 gene and increased risk of Crohns disease has been described. The objective of this candidate gene case-control study was to characterize the distribution of three polymorphisms in the bovine CARD15 gene and test their association with paratuberculosis infection in cattle. Three previously reported single nucleotide polymorphisms (E2[-32] intron 1; 2197/C733R and 3020/Q1007L) were screened for the study population (431 adult cows). The statistical analysis resulted in significant differences in allelic frequencies between cases and controls for SNP2197/C733R (P<0.001), indicating a significant association between infection and variant allele. In the analysis of genotypes, a significant association was also found between SNP2197/C733R and infection status (P<0.0001); cows with the heterozygous genotype were 3.35 times more likely to be infected than cows with the reference genotype (P=0.01). Results suggest a role for CARD15 gene in the susceptibility of cattle to paratuberculosis infection. These data contribute to the understanding of paratuberculosis, suggest new similarities with Crohns disease and provide new information for the control of bovine paratuberculosis.

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

Paratuberculosis (Johnes 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). Fishers 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.

Effect of high somatic cell counts on reproductive performance of Chilean dairy cattle

The objectives were to evaluate the effect of high linear somatic cell counts (LNSCC > or =4.5) during early lactation on reproductive performance and to estimate their association with the risk of abortion in a population of central-southern Chilean dairy cattle. The analysis included records from a population of 157 farms and considered 1,127,405 test-day records including 101,944 lactations that began between 1997 and 2006. After data edits, the analyses of calving to first service and calving to conception intervals consisted of 88,633 and 70,877 lactations, respectively. Once controlling for significant variables, time to first breeding was 21.8 d longer in cows with at least 1 high LNSCC before the first breeding compared with controls. Cows with at least 1 high LNSCC before the fertile breeding had an increment in time to conception of 48.7 d and required, on average, 0.49 more services to conceive. The odds of conception at first service in cows with a high LNSCC within 30 d before [after] breeding were 0.85 (0.81 to 0.89; 95% confidence interval ) [0.82 (0.78 to 0.87; 95% confidence interval)] times the odds of conception for cows without a high LNSCC during that period. The Cox proportional hazard model indicated that after correction by calving year, lactation number, and milk yield standardized to 305 d, the risk of pregnancy decreased by 44% if a high LNSCC occurred before breeding. Cows registering a high LNSCC during the first 90 d of gestation had an increased risk of abortion, being 1.22 (1.07 to 1.35; 95% confidence interval) times more likely to abort than nonaffected cows. It is concluded that subclinical mastitis, measured as LNSCC >/=4.5, had a significant effect on reproductive performance in Chilean dairy cattle.

A retrospective study on the association between different lengths of the dry period and subclinical mastitis, milk yield, reproductive performance, and culling in Chilean dairy cows

The objective of this study was to determine the association between different dry period lengths and somatic cell counts, milk yield, reproductive performance, and risk of early culling during the subsequent lactation of Chilean dairy cows. The length of the dry period was classified into 5 categories: 0 to 30 d, 31 to 52 d, 53 to 76 d, 77 to 142 d, and 143 to 250 d. Generalized mixed models were used and included herd as random effect. Time-to-event analyses were performed for evaluation of reproductive performance and culling risk. The odds of subclinical mastitis (log linear score, LNSCC≥4.5) during early lactation increased with extended dry periods (143 to 250 d) during first, second, and third test day compared with the reference dry period of 53 to 76 d [odds ratio (OR)=1.27, 1.16, and 1.31, respectively]. Short (0 to 30 d) and extended dry periods had a detrimental effect on early lactation and 305-d milk yield compared with the reference dry period. Longer dry periods were associated with increased number of days for calving-to-first service interval and calving to conception interval. Average calving-to-first service interval for short and extended dry period were 83 d and 89.4 d, respectively. Average days to conception were 127.8 d and 131.4 d for a dry period of 31 to 52 d and extended dry period, respectively. Similarly, the number of services per conception increased with length of previous dry period from 1.62 (31 to 52 d) to 2.44 (143 to 250 d). Cows with previous short and extended dry period had higher odds of culling when compared with cows in the reference group (OR=2.20 and 1.57, respectively). Compared with the reference group, cows in the dry period category 77 to 142 d had the highest odds of death followed by the category 143 to 250 d (OR=1.27 and 1.18, respectively).When death and live culling were combined, the highest odds of combined death and culling were for cows in the categories 0 to 30 d and 143 to 250 d (OR=1.63 and 1.44, respectively). We conclude that extended dry periods (143 to 250 d) increase the odds of subclinical mastitis occurrence during early lactation and have a negative association with reproductive performance. Short and extended dry periods were negatively associated with early lactation and 305-d milk yield and were related to increased overall culling when compared with the reference dry period.

Effect of calcium-energy supplements on calving-related disorders, fertility and milk yield during the transition period in cows fed anionic diets

The objective of this study was to determine the effect of a calcium-energy supplement at calving on the incidence of calving-related disorders (CRD), fertility, BCS and milk yield in cows fed anionic diets and to establish any associations among outcome variables. In Florida, from October to December 1997, 479 cows were assigned to three groups and treated at calving as follows: Group 1: 160 nontreated cows; Group 2: 158 cows, treated orally with 60g Ca as CaCl2; Group 3: 161 cows, treated orally with 110g Ca as calcium propionate (510g) plus propylene glycol (400g). No treatment effect was detected for any of the outcome variables. An association was found between dystocia and age and retained fetal membranes (RFM). Age and RFM were associated with metritis. RFM and displacement of the abomasum were associated with ketosis. Ketosis and age were related to displacement of the abomasum. Parity, BCS, ovarian cysts, RFM and metritis were associated with fertility.

Seroprevalence estimation and management factors associated with high herd seropositivity for Babesia bovis in commercial dairy farms of Puerto Rico.

A cross-sectional study was conducted to determine individual cow seroprevalence of Babesia bovis in adult lactating dairy cattle of Puerto Rico (PR), to assess the associations of farm management factors on herd seroprevalence, and to document the species of ticks infesting cattle within these farms. Antibody activity against B. bovis was determined using an indirect fluorescent antibody test (IFAT). Serum samples were obtained from 2,414 adult lactating dairy cattle from 76 randomly selected commercial dairy farms. Herd seroprevalence ranged from 0 to 51% with an overall individual cow seroprevalence for B. bovis of 26%. Ticks were collected from animals on 7 (9%) of the 76 participating commercial dairy farms. All collected ticks (n = 87) were Rhipicephalus (Boophilus) microplus. Factors associated with high herd seropositivity were dairy farms with calf but not heifer raising facilities (OR = 16, 95% CI = 3.0-86), having more than 4 neighbors with cattle (OR = 17, 95% CI = 1.6-178), same producer owning more than one farm (OR = 7.2, 95% CI = 1.6-32), and use of government services to apply amitraz on cattle (OR = 5.5, 95% CI = 1.5-20).

Induction of ovulation in nonlactating dairy cows and heifers using different doses of a deslorelin implant

The objective of this study was to evaluate ovarian function after inducing ovulation with a deslorelin implant in nonlactating dairy cows and heifers. Cattle received GnRH on Day -9, and PGF2alpha on Day -2. On Day 0, in Experiment 1, cows received either 100 microg GnRH (Control), a 750 microg (DESLORELIN 750) or 1000 microg (DESLORELIN 1000) deslorelin implant. On Day 0, in Experiment 2, cows received 100 microg of GnRH or a 450 microg (DESLORELIN 450) deslorelin implant. In Experiments 1 and 2, cows received PGF2alpha on Day 16. Ultrasonography and blood sampling for plasma progesterone (P4) were used to monitor ovarian activity. On Day 0, in Experiment 3, heifers received either 100 microg of GnRH or 750 microg (DESLORELIN 750) deslorelin implant. On Day 16, all heifers received PGF2alpha. Blood samples were collected on Days 7, 13 and 16. In Experiments 1-3, deslorelin implants did not elevate plasma concentrations of P4 in a systematic manner during the late luteal phase. In Experiments 1 and 2, deslorelin implants decreased the size of the largest follicle and the number of Class II and III follicles. In Experiments 1 and 2, deslorelin-treated cows failed to ovulate by Day 28. In conclusion, deslorelin implants induced ovulation, stimulated development of a normal CL, and delayed follicular growth during the subsequent diestrus period. For future applications, the dose of the deslorelin implant will have to be adjusted, and if used for timed-inseminations, nonpregnant cows will have to be resynchronized to minimize delayed returns to estrus and ovulation.

Diagnostic accuracy of methods for detecting Anaplasma marginale infection in lactating dairy cattle of Puerto Rico

Bovine anaplasmosis (BA) is a hemoparasitic disease of great importance in cattle within the tropical and subtropical regions of the world. Control programs for BA require accurate diagnostic assays but validation can be challenging because the true disease status of all animals is frequently not known with certainty. The objective of this study was to estimate the accuracy of assays for detection of Anaplasma marginale infection in lactating dairy cattle of Puerto Rico using Bayesian methods without a perfect reference test. There were 2,331 cattle with complete diagnostic results sampled from 79 herds, and the prevalence of BA was estimated as 22% (95% probability interval [PI]: 19–25%). The sensitivity (Se) and specificity (Sp) of a major surface protein 5 competitive enzyme-linked immunosorbent assay (MSP-5 cELISA) were estimated as 99% (95% PI: 96–100%) and 89% (95% PI: 87–92%), respectively. The Se and Sp of a quantitative polymerase chain reaction (qPCR) were 67% (95% PI: 60–74%) and 99% (95% PI: 99–100%). The Se and Sp of a card agglutination test were 34% (95% PI: 29–39%) and 99% (95% PI: 99–100%). Area under the receiver-operating characteristic curve for the MSP-5 cELISA was 0.748 (95% PI: 0.71–0.79). The MSP-5 cELISA appears to be the test of choice for screening cattle for subclinical BA based on the high estimated Se, rapidity of results, relative low cost, and ease of standardization.