Detection and characterization of estrus in dairy cattle with an electronic heatmount detector and an electronic activity tag.

The length and onset of estrus was studied in 71 lactating dairy cows using an electronic heatmount sensor (HeatWatch; DDx Inc., Boulder, CO, DeForest, WI) and an electronic activity tag (Heat Seeker, Boumatic, Madison, WI). Three methods were used to determine estrus: 1) the electronic heatmount system, 2) an increased activity ratio algorithm determined by the Heat Seeker, and 3) an increased activity count algorithm calculated for each estrous period. Mounting and physical activity variables were characterized, and the effects of synchrony, parity, and weather on these variables were determined with data from two different trials. Cows in trial 1 were not synchronized, while cows in trial 2 were synchronized. The results of the study were consistent as follows: mean numbers of mounts were 6.70 +/- 0.7 and 5.42 +/- 0.80 for trials 1 and 2, respectively; each mount lasted 3.20 +/- 0.19 s (trial 1) and 3.36 +/- 0.42 s (trial 2). Total mounting activity averaged 5.83 +/- 0.78 h per estrous period in trial 1 and 5.57 +/- 1.02 h in trial 2. Estrus identified by the increased activity count algorithm corresponded more closely to standing mount activity (determined by the HeatWatch System) than did the increased activity ratio algorithm. Synchrony, parity, and weather did not have a direct effect on physical activity. Hot weather decreased the duration of standing mount activity significantly, but did not affect the number or duration of individual mounts. All three methods of estrus detection employed improved the efficiency of detection over visual observation.

Variability and reliability of real-time milk conductivity data.

The profile of milk conductivity values that were collected using an automated data acquisition system was evaluated for errant values. Conductivity values were recorded from 35 cows for three milkings. Conductivity values that were collected at 2-s intervals were extremely variable. They contained erroneously low values because of the nature of the electronic measuring system. The variability was reduced, but not eliminated, by increasing the interval to 6 s. Erroneously low values were removed by calculating a point estimate representing a mean of the 10 highest values recorded at 6-s intervals.

Automated electronic activity measurement for detection of estrus in dairy cattle.

Two trials were conducted to characterize the performance of an automated electronic activity tag system as an aid for detection of estrus in dairy cattle. In trial 1, activity tags were attached to the rear leg of 24 cows at approximately 35 d postpartum and remained attached until pregnancy. Data collection included 66 periods of predicted estrus (cyclic periods of 18 to 24 d prior to the date of pregnancy). A summary of the data recorded in the activity tags was transmitted telemetrically to a personal computer at each milking via stationary antenna in the milking parlor. An electronic flag used an increased activity ratio to determine the ratio of activity in a test period of the previous 12 h to activity in the same 12 h during the 2 d previous to the test period, thus indicating estrus. Activity patterns were characterized from data recorded on the tags at 2-h intervals. The tag detected 74% of predicted periods of estrus versus 58% reported by herders. An increased activity ratio for at least 4 consecutive h reduced false-positive designations. In trial 2, activity tags were attached to front and rear legs on five cows, and activity patterns from the two sites were compared for 2 mo. Patterns of activity were similar from tags attached at either site, and the sites were not different in their discrimination between periods in which estrus did or did not occur. The activity tag system was an effective practical tool to detect estrus.

New technologies and decision making in high producing herds.

New technologies have evolved for improved management of on-farm records and their use in decision making. Computerized on-farm record systems, coupled with automated monitoring of individual animal performance and electronic transfer of data between the on-farm database and mainframe systems, have enhanced the capability for herd management. Electronic aids for decision making may be embedded into on-farm management programs to allow more detailed data to be available with ease and convenience. Technological advances and their application toward improved operational decisions concerning production monitoring, reproductive management, genetic improvement, feeding, and health in a 300-cow dairy herd are presented as examples. Substantial advances have been made in technologies that improve management and decision making. Evolving technologies promise to enhance further the capabilities for improved management and decision making in high producing herds.

Lactation potential as a criterion for strategy of feeding total mixed rations to dairy cows.

A trial was conducted from freshening to 30 wk postpartum to evaluate assignment of cows into production potential groups based on early lactation performance to optimize the time for switching from high to medium nutrient concentration TMR. Cows received a TMR formulated for early lactation until wk 4 of lactation and a high nutrient concentration TMR until 13, 19, or 25; the high TMR was followed by a medium nutrient concentration TMR until the end of the trial. Cows were assigned to high, medium, or low potential groups separately for parities 1, 2, and > or = 3 based on daily 3.5% FCM production as a percentage of BW measured during wk 6 and 7 of lactation. Low potential cows tended to partition energy intake into BW gain earlier in lactation than medium and high potential cows. For low potential cows, an early transfer to medium TMR moderated BW gain with no negative effect on production. High potential cows maintained their BW on the high ration; however, early transfer negatively affected production. Classification of individual cows into potential groups based on early lactation performance can serve as a useful tool for TMR feeding strategy later in lactation.

Comparative responses of lactating cows to total mixed rations or computerized individual concentrates feeding.

A trial was conducted in a commercial dairy herd in which the concentrate part of the ration was fed individually to a group of cows through computerized self-feeders. Performance results were compared with those of a group fed TMR of 65 to 67% concentrates. Rationing of individual concentrates was according to parity, milk yield, milk yield potential, BW changes, and bunk feed-stuffs. Mean intake of concentrates per cow was about 1 kg/d lower in the individually supplemented cows. This was partly compensated for by a higher intake of bunk feedstuffs. Overall daily milk yield per cow was similar to those receiving a TMR in first parity cows, higher in second parity cows, and lower in third and greater parity cows. The higher performance of the second parity cows was achieved in all milk yield potential classes, and the lower yield in subsequent lactations was due to lower performance in low and high potential classes. The individually supplemented cows gained less BW than those in the TMR group. Milk yield per unit of BW was better than milk yield as a variable to refine individual cow supplementation strategy for allocation of concentrates. Results also suggest that the same criteria used for supplementation of concentrates can be beneficial to cows' assignments and movements among different TMR groups. Computerized dispensing of concentrates, when applied properly, can economize on consumption of concentrates when grouping and feeding different TMR are impossible.

Activity monitoring and an enzyme immunoassay for milk progesterone to aid in the detection of estrus.

The accuracy and efficiency of estrus detection using an electronic activity monitor tag in conjunction with an enzyme immunoassay for milk progesterone were studied during 55 observed estrous periods in 37 cows. At approximately 30 d postpartum, cows were equipped with an activity tag and visually observed for estrus, an activity tag with a flashing light-emitting diode, or both twice daily. Milk progesterone concentrations were determined from cows observed in estrus or with an activated tag. Mean daily activity was greater on the day of estrus than during any of the 3 d preceding or 3 d following estrus. Functioning activity tags correctly identified 55% of all visually observed estrous periods that coincided with low milk progesterone levels. The overall accuracy of a flag by the tag for identifying true estrus was 21%. The enzyme immunoassay for milk progesterone was in agreement with 98% of all visually observed estrous periods and false flags committed by the tags. Although the activity tags detected some cows in estrus, a more durable and reliable tag must be developed before it is of practical value to dairy producers.

Milk yield, parity, and cow potential as variables for computerized concentrate supplementation strategy.

A trial was conducted in a dairy of a cooperating kibbutz to investigate the cow's response to individual concentrate supplementation according to daily milk production when a feed mixture containing a 50:50 concentrate:forage offered in the bunk free choice. Concentrate supplementation was provided by computerized self-feeders for cows producing over 30 kg milk/d to a maximum of 10 kg/d concentrate (as fed) according to milk production. The results were compared with those cows fed, for ad libitum intake, a total ration of 73:27 concentrate: forage (high control) and 50:50 (low control). The performance variables of individually supplemented cows (milk yield, 4% FCM yield, and BW) were analyzed according to parity and milk yield potential. The results indicated that milk yield itself could not serve as the only variable for individual concentrate supplementation as applied in this experiment. Cows in different parities and with different milk yield potentials may respond differently to the concentrate supplementation strategy, and parity numbers, milk yield potential, and BW, in addition to daily milk yield, are possible variables to be considered when applying this feeding regimen in order to exploit its economic potential efficiently.

Preovulatory LH profiles of superovulated cows and progesterone concentrations at embryo recovery.

Forty-two Holstein cows were randomly assigned to three superovulatory treatment groups of 14 cows each. Cows in Group I received follicle stimulating hormone (FSH; 50 mg i.m.); those in Group II received FSH (50. mg i.m.) along with GnRH (250 ug in 2 % carboxymethylcellulose s.c.) on the day of estrus; and cows in Group III were infused FSH (49 mg) via osmotic pump implants. FSH was administered over a 5-d period for cows in Groups I and II (twice daily in declining doses). Cows in Group III received FSH over a 7-d period (constantly at a rate of 7 mg/day). All cows received 25 mg PGF(2)alpha (prostaglandin F(2)alpha) 48 hours after initiation of the FSH treatment. Blood samples were collected from seven cows from each group at 2 hour intervals on the fifth day of superovulation for serum luteinizing hormone (LH) concentration analysis by radioimmunoassay, and blood samples were collected from all cows on the day of embryo recovery for plasma progesterone determination. The LH profile was not altered (P>0.05) by either GnRH administration or by the constant infusion of FSH as compared to FSH treatment alone. Plasma progesterone concentrations were highly correlated with the number of corpora lutea (CL) palpated (r=0.92; P<0.01) and with the number of ova and/or embryos recovered (r=0.88; P<0.01). The accuracy of predicting the number of recoverable ova and/or embryos by the concentration of plasma progesterone was 86%.

Electrical conductivity of reproductive tissue for detection of estrus in dairy cows.

The pattern of temporal measurements of electrical conductivity obtained from electrodes that had been surgically implanted in the mucosa of the vagina or in the submucosa of the vulva in each of five dairy cows was evaluated for changes associated with the occurrence of estrus. Tissue conductivity was monitored at 6-h intervals during and around estrus by hard-ware devices operating at either 16 or 100 kHz. Blood samples were taken at time of conductivity measurement for progesterone determination and at 2-h intervals during estrus for LH determination. Vaginal and vulvar biopsies were performed during diestrus and estrus to measure tissue hydration. Conductivity increased significantly at estrus relative to a nonestrus base period in both vaginal and vulvar tissue. Both electrical frequencies were found to be satisfactory for characterizing changes in tissue conductivity associated with estrus. Peak concentrations of luteinizing hormone, increases in tissue hydration, and patterns of blood progesterone were consistent with the occurrence of estrus during the time of elevated tissue conductivity.

Effects of GnRH treatment on superovulatory responses of dairy cows.

Twenty-eight Holstein cows were randomly divided into two groups. Group received 50 mg of FSH-P intramuscularly in declining doses for five days. Cows in group II received the same treatment as those in Group I but were also administered 250 ug of GnRH on the day of expected estrus. Neither the mean number of corpora lutea palpated nor the mean number of embryos recovered nonsurgically was different (P0.05) between treatments. However, administration of GnRH resulted in a higher fertilization rate and recovery of more developing embryos.

Comparison of electrical conductivity of milk with other indirect methods for detection of subclinical mastitis.

Efficacy of detecting subclinical mastitis by electrical conductivity of milk was compared with that of other indirect methods including chloride, sodium, potassium, lactose, bovine serum albumin, and somatic cell count of milk. Quarter samples of foremilk, strippings, and bucket milk were obtained from 75 cows at the afternoon milking over 8 wk. Infection of quarters was ascertained by bacteriological analysis. Electrical conductivity, chloride, and sodium content of milk were more accurate for predicting infection status of quarters than were other variables. Most variables were more accurate in predicting infection when measures were in strippings rather than in foremilk or bucket milk. For measures in strippings, misclassifications by electrical conductivity were 11.2 and 15.5% for false positives and false negatives. The accuracy of the electrical conductivity of milk for detection of subclinical mastitis compared favorably with all indirect methods. Accuracy of detection and adaptability to both manual and automatic cow-side mastitis detection systems indicate that the method has considerable potential as a screening test for subclinical mastitis.

Effects of milking interval on selected milk constituents from normal and infected quarters.

Effects of milking interval on electrical conductivity, chloride, sodium, potassium, lactose, and somatic cell counts of milk were determined. Quarter samples of foremilk, primary milk, and strippings were obtained from 12 cows after 3, 6, 9, 12, and 15-h milking intervals. The preceding interval to all experimental intervals was standardized at 12 h. Infection status of quarters was ascertained by bacteriological analysis. Effect of milking interval was significant on all variables measured. Highest conductivity, chloride, sodium, and cell counts were at the 3-h interval but declined to their lowest at the 9-h interval. Conductivity, chloride, and sodium then steadily increased from 9 to 15 h. Lactose followed the opposite trend and was highest at the 9-h interval. Trend was similar in samples from both uninfected and infected quarters; however, changes were more pronounced in the latter. Change of conductivity from infection varied with type of sample and milking interval with strippings being the most sensitive. All samples were least sensitive to these changes at the 9-h interval. Conductivity measurements on strippings will be more sensitive for detecting mastitis than measurements from foremilk or primary milk, especially measured following short milking intervals.

Influence of the estrous cycle on selected biochemical and cytologic characteristics of milk of cows with subclinical mastitis.

The purpose in this experiment was to determine the relationship between subclinical mastitis and the estrous cycle. Subclinical mastitis was defined as a quarter in which milk had a somatic cell concentration greater than 500,000/ml and was bacteriologic culture-positive on 2 consecutive examinations. Normal quarters were defined as quarters from which milk had a somatic cell concentration less than 500,000/ml and was bacteriologic culture-negative on 2 consecutive examinations. Selected biochemical and cytologic characteristics of milk from 10 cows with subclinical mastitis were measured at 5-day intervals during the estrous cycle. Milk and blood progesterone concentrations were determined. Analysis of variance of dependent variables was performed, using a model with the following factors: cows, treatments, days of estrous cycle, and interaction of treatment with day of the estrous cycle. Treatment consisted of comparison of normal and subclinically mastitic quarters. Clinical signs of mastitis tended to occur more often during estrus (days 0 and 20) than during diestrus (day 10). Day of the estrous cycle was a significant source of variation for bovine serum albumin concentrations in milk. Somatic cell concentrations, electrical conductivity, milk bacterial concentrations, and log10 milk bacterial concentrations did not vary significantly during days of the estrous cycle. A significant treatment-by-day interaction occurred for milk progesterone concentrations; blood progesterone concentrations were not similarly affected. Milk progesterone concentrations for mastitic and normal quarters were similar at estrus (days 0 and 20) and metestrus (day 5). Milk progesterone concentrations for mastitic quarters were significantly decreased on day 15 of the estrous cycle, compared with values from normal quarters.

Diagnosis and treatment of acute mastitis in a large dairy herd.

In a 270-cow dairy herd, milk samples from all cows with acute mastitis were cultured during a 12-month period. Of 119 isolates (from 166 quarters), 49% were gram-positive organisms, 39% were gram-negative organisms, and 12% were yeasts. Of all samples from cows with acute mastitis, 40% failed to produce colonies on culture media. Recovery of the common gram-positive pathogens, Staphylococcus aureus (11% of isolations) and Streptococcus agalactiae (1% of isolations), was rather low. However, S epidermidis (14% of isolations) and streptococci other than Str agalactiae (9% of isolations) were recovered more frequently than expected, particularly in recently calved cows. Coliform organisms accounted for 35% of the total isolates and were the single most important cause of acute mastitis. Of 42 cows with coliform mastitis, 6 died despite intensive antibiotic and electrolyte therapy. There was no death loss among cows with mastitis caused by gram-positive organisms. Antimicrobial susceptibilities of 95 isolates to 11 antimicrobials was determined by standardized methods. Organisms were most often susceptible to chloramphenicol, cephalothin, and gentamicin. A treatment regimen consisting primarily of oxytetracycline and/or sulfonamides systemically in conjunction with intramammary infusions of cephapirin was evaluated. Treatment response in 37 quarters was determined by culturing before treatment and at 4 or more days after treatment. Of 23 quarters initially culture-positive, 22 were negative on reculture. Treatment response appeared to agree with the results of the susceptibility testing.

Milk progesterone for pregnancy diagnosis in dairy goats.

Factors affecting progesterone concentration in milk of lactating dairy goats and use of this milk for pregnancy diagnosis were studied. Radioimmunoassay was used to assay progesterone in milk. Mean milk progesterone (ng/ml) +/- standard errors of 6 pregnant does for first, composite, and last milk were 9.9 +/- 2.0, 18.2 +/- 3.5, and 21.7 +/- 4.1. Correlation between milk fat and progesterone in composite milk was low (.11). Composite milk samples from 4 nonpregnant does were obtained daily throughout the estrous cycle. Milk progesterone (ng/ml) was 1 to 2 at estrus, rose to 5 to 12 within 2 to 5 days, reached a plateau at 15 to 25 in the middle of the estrous cycle, and then dropped to low concentrations again at 3 to 5 days before the next estrus. Milk progesterone also was used to diagnose pregnancy in 72 does. Forty-two does were diagnosed pregnant by high progesterone; 36 of these does later produced kids, and 5 other does aborted in various stages of pregnancy. Of 21 does diagnosed not pregnant with low progesterone, 19 does were not pregnant by either return to estrus or lack of parturition in the spring. All three incorrectly diagnosed does were problem breeders. Nine does with intermediate milk progesterone were classified questionable. Milk progesterone can be used to provide an early indication of the pregnancy status of does.

Incidence and treatments of postpartum reproductive problems in a dairy herd.

Incidence of assisted births, retained fetal membranes (RFM), and metritis were recorded in one hundred dairy cows from parturition through 14 days post-calving. Manual removal of RFM was not attempted. All RFM were excised inside the vulva and observations of natural RFM expulsion were recorded. Fifteen of 100 cows (15%) had assisted births, 27 (27%) had RFM, 8 (8%) had primary metritis not associated with other postpartum reproductive problems, and 26 (26%) had secondary metritis. Uterine swabs for culture were collected during the study from cows with postpartum reproductive problems. E . coli was the most common organism isolated (69.4%). Sensitivities of all isolates to penicillin, tetracycline, and triple sulfa were 44.0%, 59.5%, and 36.9% respectively. One of two antibiotic treatments were administered to cows with these postpartum reproductive problems. Treated animals received either 5 g. tetracycline powder IU on day 1 of treatment plus 10.5 million units procaine penicillin G IM on days 1, 2, and 3; or 4 Sulfaurea boluses IU on day 1. Despite the antibiotic treatments, 26 of 34 cows having either assisted birth and/or RFM developed metritis (76%). Neither treatment regimen was superior to the other. The poor results of antimicrobial therapy suggested the futility of routine administration of therapeutic agents for postpartum reproductive problems. Treatment failure was attributed to ineffective drugs or inadequate dosage regimens.

Electrical conductivity of milk for detection of mastitis.

The potential value of electrical conductivity of milk as a screening test for subclinical mastitis was evaluated. Conductivity of foremilk and of postmilking strippings from 368 quarters of 92 cows was measured. Infection status of quarters was determined by bacteriological analysis of strict foremilk samples. Infections were classified as by primary or secondary pathogens, depending on the importance of the isolated organism as a mastitis pathogen. Somatic cells were counted on foremilk samples. Milk conductivity increased with infection. Conductivity of postmilking strippings was higher than that of foremilk in samples from quarters infected by primary pathogens. By thresholds which correctly classified at least 90% of normal quarters, accuracy of identifying primary pathogen infections by absolute conductivity was 62.8 and 96.2% with foremilk and postmilking strippings. Differential conductivity and combination of absolute and differential methods also were evaluated with the latter being the most effective. Number of quarters with elevated conductivity of postmilking strippings tended to be higher when somatic cell count was greater than 500,000/ml in both normal and infected groups. Conductivity of milk seems to hold promise as an indicator of subclinical mastitis.

Effect of length of milking interval and fat content on milk conductivity and its use for detecting mastitis.

Foremilk and strippings were obtained from 20 cows at the morning and evening milkings where the milking intervals were 14 h and 10 h. Infection status was determined by bacteriological analysis. Conductivity of foremilk and strippings was determined. Cows then were switched to 12 h milking interval, and conductance of foremilk and strippings from both milkings was determined. Conductance of foremilk samples increased after longer milking interval. Accuracy in detecting infections by primary pathogens via conductivity of foremilk was also greater following the long interval. Conductivity of foremilk from morning and evening milkings were, however, similar when the milking interval was even. Conductivity of strippings was affected less by milking interval. Conductance determination on quarter samples from 28 cows on both a whole and fat-free basis indicated an inhibitory effect of milk fat on conductivity. Conductivity of skimmed strippings samples was greater than that of skimmed foremilk samples, indicating higher electrolyte in strippings, and may explain why conductivity of strippings is not significantly lower than of foremilk in spite of the higher fat content in the former