Plasma mineral and energy metabolite concentrations in dairy cows fed an anionic prepartum diet that did or did not have retained fetal membranes after parturition

OBJECTIVE: To compare plasma total calcium, phosphorus, magnesium, nonesterified fatty acids (NEFA), beta hydroxy butyrate (BHB), and glucose concentrations in parturient dairy cows that were fed an anionic prepartum diet between those with and without retained fetal membranes (RFM) at 24 hours after parturition. ANIMALS: 152 Holstein cows that calved during October through December of 1997 PROCEDURE: All cows were fed an anionic prepartum diet. Blood sample was taken within 6 hours after parturition from randomly selected cows. Thirty-nine cows had a diagnosis of RFM at 24 hours after parturition; 113 were not affected with RFM. At calving, body condition score (BCS; 1 [thin] to 5 [obese]), parity, and calving difficulty score were recorded. Plasma calcium, phosphorus, magnesium, NEFA, BHB, and glucose concentrations were compared between cows with or without RFM. RESULTS: Cows with RFM had significantly lower plasma calcium concentration soon after calving, compared with cows without RFM. Cows with a parity of > or = 3 had significantly lower plasma concentrations of calcium and higher concentrations of magnesium, compared with cows with a parity of 1 or 2. Cows with a BCS of > or = 3.25 at calving had significantly higher plasma concentrations of BHB than cows with a BCS of 2.75 to 3.0. Cows with dystocia had significantly higher plasma concentrations of glucose, compared with cows without dystocia. CONCLUSIONS AND CLINICAL RELEVANCE: In parturient cows fed a prepartum anionic diet, those with RFM have lower plasma calcium concentrations than cows without RFM, although this association does not prove a cause-effect relationship.     

Constraints on dairy cattle productivity at the smallholder level in the Philippines

Survey data on dairy cattle production were gathered in two sites [Site I (three-year survey) and Site II (two-year survey)] in Southern Luzon, Philippines. Crossbred (Holstein-Friesian x Sahiwal) dairy cows (n = 122) managed by smallholder farmers belonging to five primary cooperatives under the federation of dairy farmers, were monitored monthly for milk production, feed intake and availability, and reproduction and health status. The purpose of the survey was to identify constraints to productivity. The reproductive status of the cows was monitored by measuring milk and plasma progesterone concentrations by radioimmunoassay and rectal palpation of the ovaries. Plasma concentrations of selected metabolites [beta-hydroxybutyrate (BHB), inorganic phosphorus, albumin, globulin, urea] were also measured at one month before calving and at one month and 2-3 months postpartum, to determine if these could serve as biochemical indicators of nutritional stress. A long calving interval (CI = > 400 days) was identified as the major constraint to productivity of dairy cattle on smallholder farms. The three main problems related to this reproductive constraint were: (1) poor breeding management, in particular lack of accurate estrus detection; (2) repeat breeding, i.e. three or more services were required before conception; and (3) poor ovarian function, shown by some cows with lose progesterone levels. An important cause of these problems was undernutrition, particularly at critical periods of the cow's reproductive life, reflected in the slow recovery from loss in body weight and condition score during the early postpartum period and the increased plasma BHB values at peripartum period in some cows, indicative of negative energy balance, and the flat lactation profile. These findings are useful and relevant as a database in the development of an appropriate management scheme aimed toward improving dairy cattle production and productivity at smallholder level. It highlights the importance of estrus detection, good breeding management and the use of a practical strategic nutritional supplementation, particularly during stressful periods in the cows's reproductive life.     

Individual variability in physiological adaptation to metabolic stress during early lactation in dairy cows kept under equal conditions

This study was conducted to investigate individual metabolic and endocrine adaptation to lactation under conditions of identical housing and feeding conditions in high-yielding dairy cows. Forty-five cows were studied on a research farm under standardized but practical conditions. From wk 2 before calving until wk 14 postpartum, blood samples were collected at weekly intervals and assayed for blood chemistry and various metabolites and hormones. Body weight, BCS, and backfat thickness were also recorded weekly. Milk yield, milk composition, and feed intake and energy balance were accordingly measured during the postpartum phase. The animals were retrospectively classified according to their plasma concentration of beta-hydroxybutyrate (BHB): cows in which a BHB threshold of 1 mM was exceeded at least once during the experiment were classified as BHB positive (BHB+); cows with BHB values consistently below this threshold were classified as BHB negative (BHB -). Using this classification, differences for NEFA and glucose concentrations were observed, but the mean calculated energy balance did not differ between the groups during the experimental period (-22.2 MJ of NE(1)/d +/- 4.7 for BHB+ and -18.9 MJ of NE(1)/d +/- 4.9 for BHB-). In BHB+ cows, the peripartum decrease (P < 0.05) of BW, BCS, and backfat thickness was more pronounced than in BHB- cows. Mean milk yields did not differ between groups. However, BHB+ cows had greater milk fat and lesser milk protein contents (P < 0.05), resulting in a greater (P < 0.05) fat:protein ratio than in BHB- cows. Thus, to some extent, cows were able to compensate for the negative energy balance by adjustments in performance. Milk acetone concentrations followed BHB concentrations in blood. Insulin-like growth factor-I and leptin concentrations were greater (P < 0.05) in BHB- cows during the time of observation than in the BHB+ cows. Comparing the reproductive variables recorded (first increase of progesterone, first service conception rate, number of services per conception, interval from calving to first AI, interval from first AI to conception, and days open) between the 2 groups yielded no significant differences. Our findings imply that despite comparable energy balance, there is considerable individual variation of the adaptive ability of cows during early lactation based on a variety of metabolic and endocrine variables.     

Fertility of dairy cows in Northern Ireland

A comprehensive database was established on the milk production and reproductive performance of dairy cows in 19 selected herds in Northern Ireland, varying in size, management system and genetic merit. Data were obtained for 2471 cows, 1775 of which calved in a second year, and 693 were culled from the herd for specific reasons. The estimated mean rate of heat detection (assessed by the interheat interval during the main breeding season) in all the herds was 71 per cent, with a range from 53 to 92 per cent The average conception rate to first insemination was 37.1 per cent (range 21 to 66 per cent). The average calving interval for the retained cows was 407.2 days (range 359 to 448 days). Twenty-eight per cent of the cows that calved were culled, with infertility being the largest single reason (26.8 per cent of the cows culled). There were major differences in reproductive performance between the herds, but heat detection rate, conception rate and calving interval did not appear to be affeded by a herd's genetic merit. The herds with shorter calving intervals were characterised by better heat detection efficiency (83 v 61 per cent, P<0.01), a shorter interval from calving to first insemination (74 v 97 days; P<0.05), a higher conception rate to first insemination (45 v 34 per cent, P>0.10) and a lower removal rate (23 v 37 per cent, P<0.01). Furthermore, the cows in these herds had lower body condition scores (BCS) in the dry period (3.0 v 3.3; P<0.05) but lost less body condition in early lactation (0.3 v 0.6 BCS units, P<0.05). These results show that dairy herd fertility in Northern Ireland is generally low and similar to that previously reported for England and the USA, but that in some herds changes in herd management practices improved the cows' fertility.     

Monitoring and testing dairy herds for metabolic disease.

Clinical impressions of metabolic disease problems in dairy herds can be corroborated with herd-based metabolic testing. Ruminal pH should be evaluated in herds showing clinical signs associated with SARA (lame cows, thin cows, high herd removals or death loss across all stages of lactation, or milk fat depression). Testing a herd for the prevalence of SCK via blood BHB sampling in early lactation is useful in almost any dairy herd, and particularly if the herd is experiencing a high incidence of displaced abomasum or high removal rates of early lactation cows. If cows are experiencing SCK within the first 3 weeks of lactation, then consider NEFA testing of the prefresh cows to corroborate prefresh negative energy balance. Finally, monitoring cows on the day of calving for parturient hypocalcemia can provide early detection of diet-induced problems in calcium homeostasis. If hypocalcemia problems are present despite supplementing anionic salts before calving, then it may be helpful to evaluate mean urinary pH of a group of the prefresh cows. Quantitative testing strategies based on statistical analyses can be used to establish minimum sample sizes and interpretation guidelines for all of these tests.     

Risk factors associated with reproductive performance in small-scale dairy farms in Mexico

Several studies suggest that reproductive performance in small-scale dairy farms is low reducing the farms’ profitability. Therefore, identifying risk factors associated with low reproductive performance is a key step to implement an improved reproductive management program. Accordingly, the aim of the present study was to identify the main risk factors affecting the reproductive performance of cows in small-scale dairy farms. Ninety-six dairy farms were incorporated into this study, and data from 1263 lactations were collected with different events as potential risk factors. Logistic regression models were used to assess the association (odds ratio, OR) and impact (population attributable fraction, PAF) between the potential risk factors and the reproductive variables. The main risk factors associated with assisted calving were male calf and primiparous cows (OR?=?1.7, PAF?=?0.315 and OR?=?1.5, PAF?=?0.131, respectively), while for retained fetal membranes (RFM) were assisted calving and abortion (OR?=?4.5, PAF?=?0.440 and OR?=?8.1, PAF?=?0.239, respectively). The main risk factors for days to first service over 70 days in milk were low body condition score at calving (BCS?≤?2.5) and primiparous cows (OR?=?2.2, PAF?=?0.285 and OR?=?1.4; PAF?=?0.096, respectively), while for days open over 110 days in milk were low BCS at calving (BCS?≤?2.5) and primiparous cows (OR?=?1.7, PAF?=?0.213 and OR?=?1.4; PAF?=?0.096, respectively) The main risk factor for non-pregnant cows at first service was RFM (OR?=?1.7; PAF?=?0.059). In conclusion, assisted calving, male calf, BCS?≤?2.5 and RFM were the main risk factors associated with reduced reproductive performance in small-scale dairy farms in tropical and subtropical regions of Mexico.

     

Bovine Subclinical Ketosis in Dairy Herds in Iran

Subclinical ketosis (SCK) is defined as elevated concentrations of ketone bodies in the absence of clinical signs of ketosis. It is an important metabolic disease in dairy cattle during early lactation and is associated with losses in milk production and several other periparturient diseases. Limited information is available regarding the prevalence of SCK in dairy herds in Iran. The objectives of this study were (i) to determine the incidence of SCK in the dairy herds in Kerman province of Iran using serum beta-hydroxybutyrate (BHB) concentrations, and (ii) to investigate the relationship between serum concentrations of BHB and glucose of cows with SCK. In the present study, 90 multiparous Holstein cows (4-6 years old) from 11 commercial dairy herds were evaluated 3-4 weeks after calving. The distribution of blood BHB concentrations seemed to suggest a cut-off point of 1200 micromol/L between cows with and without SCK. At this cut-off point, 14.4% of tested cows (13/90) were classified as subclinically ketotic, with the prevalence rate within herd ranging from 10% to 20%. Cows with SCK were detected in all the investigated dairies except one. Blood glucose concentrations in cows with SCK were significantly lower (p < or = 0.05) than in cows without SCK, and serum BHB and glucose concentration were inversely correlated (r = -0.43, p < or = 0.05). The results suggest that, using a cut-off of 1200 micromol/L, BHB concentrations can be used during early lactation for diagnosis and to make management decisions for prevention and treatment.     

Postpartum anestrus in dairy cattle--a review

In modern high-yielding dairy herds fertility is of major economic importance. In order to gain maximum profit, calving intervals should not exceed 365 days. The achievement of a 365-day calving interval requires an early resumption of ovarian activity, an excellent oestrus detection, and a high first-service conception rate. Especially the inability to detect oestrus and to mate the cows by 60 to 80 days after calving is a common problem among dairy farmers nowadays. In this article a review is given about the occurrence, causes, treatment and prevention of post-partum anoestrus in dairy cows.     

Energy metabolites in pre- and postpartum dairy cattle as predictors of reproductive disorders

This study aimed to determine values for selected energy metabolites (non-esterified fatty acid [NEFA], β-hydroxybutyrate [BHB], urea or urea:BHB ratio), together with a body condition score, associated with an increased risk of cows developing a reproductive disorder and to investigate temporal relationships between predictors and reproductive outcome. A cohort of 98 cows on one farm was monitored weekly from four weeks before to 10 weeks after calving; 89 cows provided sufficient data to calculate commencement of luteal activity (C-LA). Cows with high NEFA × urea (Nu; product of NEFA and urea) values one and three weeks after calving were twice as likely to develop cystic ovarian disease (risk ratio 2). Cows that developed endometritis had high NEFA values one (P=0.02) or four weeks (P=0.04) before calving, or low urea:BHB ratios two weeks before calving, at calving or three weeks after calving (P=0.024, P=0.031 and P=0.001, respectively). Cows that had delayed C-LA had high NEFA values one week after calving (P=0.05) or low urea:BHB ratios three or four weeks after calving (P=0.004 and P=0.003, respectively).     

Correlation between energy balance and fertility in Finnish dairy cows.

The effect of serum glucose, ASAT and urea on reproductive performance was studied in 45 Finnish dairy cows from 8 different herds. Blood samples were taken a month before calving as well as 2 weeks and 2 months after calving. Serum urea, ASAT and glucose were used as indicators of metabolic and energy balance. Glucose and ASAT concentrations were significantly correlated with fertility 2 weeks after calving, but not before calving or 2 months after calving. Antepartum, 60% of the cows had a low urea level; at 2 weeks and at 2 months postpartum 89% and 65%, respectively had low levels of urea. The cows were divided into groups as follows: low or high (greater than or equal to 2.9 mmol/l) glucose level and low or high (greater than or equal to 2.5 mmol/l) urea level. Low levels of glucose and/or urea in puerperium were associated with poor fertility. The intervals from calving to first insemination and conception were shorter in the group with high glucose and high urea than in the group with low values. The cows with the shortest intervals from calving to first insemination and conception showed adequate metabolic balance (high levels of urea and glucose). Clinical ketosis had an adverse affect on intervals from calving to first insemination and on conception. Intervals from calving to first insemination and to conception were significantly (p less than 0.01) longer in ketotic cows than in non-ketotic ones. Liver damage, reflected as elevated activity of ASAT, was associated with poor fertility. If shorter calving intervals are desired, adequate energy balance in puerperium is essential.     

Metabolic profiles in five high-producing Swedish dairy herds with a history of abomasal displacement and ketosis

Background

Body condition score and blood profiles have been used to monitor management and herd health in dairy cows. The aim of this study was to examine BCS and extended metabolic profiles, reflecting both energy metabolism and liver status around calving in high-producing herds with a high incidence of abomasal displacement and ketosis and to evaluate if such profiles can be used at herd level to pinpoint specific herd problems.

Methods

Body condition score and metabolic profiles around calving in five high-producing herds with high incidences of abomasal displacement and ketosis were assessed using linear mixed models (94 cows, 326 examinations). Cows were examined and blood sampled every three weeks from four weeks ante partum (ap) to nine weeks postpartum (pp). Blood parameters studied were glucose, fructosamine, non-esterified fatty acids (NEFA), insulin, β-hydroxybutyrate, aspartate aminotransferase, glutamate dehydrogenase, haptoglobin and cholesterol.

Results

All herds had overconditioned dry cows that lost body condition substantially the first 4–6 weeks pp. Two herds had elevated levels of NEFA ap and three herds had elevated levels pp. One herd had low levels of insulin ap and low levels of cholesterol pp. Haptoglobin was detected pp in all herds and its usefulness is discussed.

Conclusion

NEFA was the parameter that most closely reflected the body condition losses while these losses were not seen in glucose and fructosamine levels. Insulin and cholesterol were potentially useful in herd profiles but need further investigation. Increased glutamate dehydrogenase suggested liver cell damage in all herds.     

Risk factors for postpartum endometritis and the effect of endometritis on reproductive performance in dairy cows in Korea

The objectives of this study were to determine the risk factors for postpartum endometritis by evaluating several reproductive factors in individual cows, and to determine the effect of endometritis on the subsequent reproductive performance in dairy herds in Korea. The data, including health status, parity and body condition score (BCS) of cows, and calving date, were collected from 320 cows in eight dairy herds calving from January 2001 to October 2002. We used logistic regression to evaluate the effects of these factors on endometritis. A stepwise procedure, used to obtain the appropriate model with alpha=0.05, revealed that retained placenta, metabolic disorders and parity are the important risk factors for endometritis. The mean intervals from calving to first service and conception were prolonged (P<0.01) by 23 and 36 days, respectively, in the endometritis group compared to the non-endometritis group. The first service conception rate was lower (P<0.05) in the endometritis group (47.6%) than in the non-endometritis group (62.6%). The number of services per conception was higher (P<0.05) in the endometritis group (1.9) than in the non-endometritis group (1.6). We conclude that retained placenta, metabolic disorders and cow parity are strongly correlated with the development of postpartum endometritis, which decreases reproductive performance in dairy herds in Korea.     

Risk factors and the economic impact of ovarian cysts on reproductive performance of dairy cows in Korea

The objectives of this study were to determine the risk factors for development of postpartum ovarian cysts by evaluating several reproductive factors in individual cows, and to determine the economic impact of ovarian cysts on subsequent reproductive performance in dairy herds in Korea. The data, including cow parity, abnormal puerperium, endometritis, body condition score (BCS), and breeding status were collected from 634 cows in 9 dairy herds. We used logistic regression to evaluate the effects of these factors on ovarian cysts. A stepwise procedure, used to obtain the appropriate model with alpha=0.05, revealed that cow parity was the most important risk factor for ovarian cyst development within 8 weeks postpartum, while development of endometritis and BCS loss>or=1 from the dry period to 8 weeks postpartum were the most important risk factors for ovarian cyst development beyond 8 weeks postpartum. The occurrence of ovarian cysts beyond 8 weeks postpartum prolonged (P<0.01) the mean intervals from calving to first service (27 days) and conception (77 days), and increased (P<0.05) the culling rate (7.8%), while ovarian cyst development within 8 weeks postpartum did not affect (P>0.05) the mean intervals from calving to first service and conception or the culling rate. The economic loss resulting from the occurrence of ovarian cysts was estimated at approximately 823,996 won ($687) due to effects on the cost of nutrition, average growth of calves, labor and medical costs, and culling. These results suggest that cow parity is correlated with the development of ovarian cysts within 8 weeks postpartum, and endometritis and BCS loss>or=1 from the dry period to 8 weeks postpartum are correlated with the development of ovarian cysts after 8 weeks postpartum, which decreases reproductive performance and results in economic loss in dairy herds in Korea.     

Paratuberculosis sero-status and milk production,SCC and calving interval in Irish dairy herds

The objective of this study was to investigate the impact of paratuberculosis sero-status on milk yield, fat, protein, somatic cell count and calving interval in Irish dairy herds. Serum from all animals over 12 months of age (n = 2,602) in 34 dairy herds was tested for antibodies to Mycobacterium avium subsp. paratuberculosis using an ELISA. Herds were categorised by sero-status into positive, non-negative and negative, where a positive herd contained two or more positive cows, a non-negative herd contained only one positive cow and a negative herd contained no positive cows. Data at animal, parity and herd-level were analysed by multiple regression using general linear models. Positive herds (mean herd size = 129 cows) and non-negative herds (81 cows) were larger than negative herds (72 cows) (P < 0.01). Negative herds had the highest economic breeding index (EBI), while positive herds had the highest estimated breeding value (EBV) for milk yield. There was no significant effect of paratuberculosis sero-status at animal, parity or herd-level on milk yield, milk fat or protein production, somatic cell count score (SCCS) or calving interval. Negative herds tended to have a lower SCCS than positive and nonnegative herds (P = 0.087). This study only examined the effects of paratuberculosis sero-status but did not examine the clinical effects of Johne's disease at the farm or dairy industry levels.     

Use of every ten-day criteria for metabolic profile test after calving and dry off in dairy herds

The traditional metabolic profile test cannot be applied to peripartum dairy cows, because these cows are in a state of physiological abnormality making it difficult to interpret their blood components. This study aimed at establishing and evaluating the practicability of interpreting a metabolic profile test every 10 days (Ten-day criteria) during the dry and lactation periods in herds with high and no incidence of peripartum diseases. Data from 29,043 cows in 1,130 commercial dairy herds were used to establish standard values every 10 days, mean +/- 1.0 standard deviation for the metabolic profile test. The practicability of these criteria was evaluated in herds with peripartum diseases. In the ten-day criteria, the body condition score, albumin, blood urea nitrogen, glucose, total cholesterol, nonesterified fatty acids, gamma-glutamyl transpeptidase and aspartate aminotransferase, fluctuated during the dry and early lactation periods and there were very big changes in packed cell volume, blood urea nitrogen, total cholesterol and magnesium just after calving. The ten-day criteria were able to detect overconditioned cows, low levels of albumin, total cholesterol and magnesium, and high nonesterified fatty acids in herds with a high incidence of peripartum diseases. In conclusion, the ten-day criteria can be successfully applied to peripartum cows, and is recommended because it is able to detect metabolic abnormalities not only in the herd, but also in individual cows.     

Effects of sodium monensin on reproductive performance of dairy cattle. I. Effects on conception rates, calving-to-conception intervals, calving-to-heat and milk production in dairy cows

SUMMARY A total of 1061 lactating dairy cows in six different herds were randomly allocated to treatment and control groups. One herd was lot-fed on total mixed rations; three herds were fed on pasture with significant amounts of supplementary concentrates, and two herds were primarily pasture fed. Treated cows received a slow-release, intraruminal capsule containing 32 g sodium monensin within 7 days of calving. Conception rates at first service, days to first oestrus and calving-to-conception interval did not differ significantly between untreated and monensin-treated cows in the 5 herds, 3 herds and 4 herds, respectively, in which these outcomes were examined. Treatment of lactating cows immediately after calving may not be the optimal method to achieve fertility responses with capsules containing sodium monensin. Monensin treatment significantly increased milk yield in one of the six herds. Milk fat or milk protein production was not significantly affected by treatment.     

Calving patterns in seasonal dairy herds

Two field studies examined the calving patterns of cows in seasonal dairy herds in the Waikato (Field Study 1) and South Taranaki regions (Field Study 2). The first study examined patterns for cows commencing their second or subsequent lactation in herds which had used an inseminating service during the previous season. The second study included first lactation heifers only in 15 herds where animals had been naturally mated, and in 15 herds in which they had been synchronised and then artificially inseminated at the synchronised oestrus. The parameters describing calving patterns were based on the date for each herd's planned start of calving (PSC), which was 282 days from the date on which breeding commenced in the preceding season. The average interval from PSC to mean calving date for the 35 herds in Field Study 1 was 22 days, with individual herds ranging from 15 to 30 days. In herds with heifers which had been naturally mated (Field Study 2), it was 17.6 days compared to 11.0 days for previously synchronised animals. Calculating the intervals from PSC to median calving date and separately for the last two quartiles more effectively described a herd's calving pattern. The duration for the last quartile of the calving pattern was influenced by the extent and timing of induced calving. In Field Study 1, 88.6% of the 35 herd owners induced premature parturition in at least one cow. In these herds, 11.3% of cows were treated and calved prematurely. Only 61.7% of heifers which had previously been naturally mated calved by 3 weeks after PSC. Their calving dates were not evenly distributed over this 3-week period, with 9.8% in the first week and 25.6% in the third week. The calving pattern for heifers which had been previously synchronised showed several distinct peaks. Calvings to the synchronised mating were completed 15 days after PSC, by which time 64.7% of animals had calved. By 3 weeks after PSC, 72.9% of these heifers had calved. The results showed that there was considerable variation in calving patterns in seasonal dairy herds. This variation would have been due to differences in conception pattern, and the way induced calving had been applied. The calving pattern in heifers which had been naturally mated was less concentrated than had been expected. Synchronisation can significantly concentrate the calving pattern of these first lactation animals. The parameters used to describe calving patterns may be less applicable in herds in which a high proportion of animals is induced to calve prematurely, or where a whole herd is synchronised. Nonetheless, they do serve as an illustrative example of the variation in calving patterns among herds.     

Studies of the transition cow under a pasture-based milk production system: metabolic profiles

This study describes the effect of parity (multiparous versus primiparous) and body condition score (BCS) at calving (<3 or > or =3; scale 1-5) on variations of BCS, body weight (BW) and metabolic profiles in Holstein cows grazing on improved pastures. Forty-two cows were studied (21 multiparous and 21 primiparous) from 2 months before to 3 months after calving. BCS, BW and milk production were measured every 2 weeks. Blood samples were taken every 2 weeks to determine total protein, albumin, urea, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), cholesterol, aspartate aminotransferase (AST), calcium, phosphorus and magnesium. Primiparous cows had lower BCS during the early postpartum (PP) period and produced less milk than multiparous. In primiparous cows NEFA concentrations were higher during the early postpartum period; BHB levels were similar in both categories during this period. Primiparous cows showed a more unbalanced metabolic profile than multiparous cows, reflecting that they are recovering from the loss of BCS after calving with less success.     

The use of an indirect Ostertagia ostertagi ELISA to predict milk production response after anthelmintic treatment in confined and semi-confined dairy herds

An indirect Ostertagia ostertagi ELISA was used in late lactation milk samples from cows in confined and semi-confined dairy herds to determine if it could predict milk production response after endectocide treatment at calving. Holstein cows from 9 dairy farms from Prince Edward Island (PEI), 5 from central Nova Scotia and 16 from southern Ontario that were participating in a clinical trial of endectocide treatment around calving were used in this study. The cows were randomly treated with either eprinomectin pour-on endectocide or a placebo solution. Milk samples were obtained from cows late in the lactation before treatment was applied. These samples were tested for antibodies to gastrointestinal nematodes (GIN) using the indirect ELISA with the results expressed as optical density ratios (ODR). Production records were obtained from a computerized database of dairy herd improvement data. Pre-calving ODR showed a seasonal pattern. They were higher in the summer and fall and lower during the winter months. Older animals had higher pre-calving ODR values compared with younger cows. Similarly, cows from semi-confined herds had higher parasite antibody levels compared with cows from confined herds. The endectocide treatment did not affect the milk production response in the overall study population. However, the interaction effect between treatment and pre-calving ODR on milk production response after endectocide treatment was significant (P = 0.02), with some evidence of positive treatment response in cows with an ODR > 0.4. The relationship between pre-calving ODR and production response appeared to be quadratic rather than linear.     

Effect of factors associated with insemination on calving rate in dairy cows

The results of 7569 inseminations performed on 6007 cows in 94 dairy herds were used to investigate the relative importance of time of insemination, bull and inseminator on calving rates in dairy cows. Although the time of insemination in relation to the first observation of oestrus was shown to have some effect, the effect was minimal during the first 24 hours. The maximum difference in expected calving rates between cows served with semen from groups of bulls with a history of either low or high fertility was 20 per cent, and the maximum difference in expected calving rate between cows inseminated by groups of inseminators who had consistently achieved either low or high fertility was 13 per cent.