Reproduction In Dairy Cattle Research Articles

Effect of Using Progesterone Releasing Intravaginal Device with Ovsynch Program on Reproduction in Dairy Cattle during Summer Season

Sixty postpartum lactating Friesian cows in 3 treatments at a commercial dairy farm were used to study the effect of using progesterone supplementation with GnRH and PGF2a synchronization with and without timed Al on fertility during summer. Cows in treatment1(Tr 1 ) and treatment2 (Tr 2 ) were fitted with progesterone releasing intravaginal device (PRID) device and injected with 10 g GnRH agonist on 51′3 d postpartum (pp). Seven days later, PRID was removed and cows received 25 mg PGF2a. Two days later, Tr 1 cows received another injection of 10 g GnRH and timed Al 16-20 h later. Control cows received only 25 mg PGF2a 58′3 d pp. Tr 2 and control cows were AI at detected estrus. Serum progesterone for all cows was determined on days of injection, Al and 21, 23 and 28 d postinsemination. Pregnancy rates from first Al based on serum P4 concentrations on d 21, 23 and 28 postinsemination (50, 40 and 35%) and that based on rectal palpation 40-45 d postinsemination (30, 15 and 15% for Tr 1 , Tr 2 and control cows, respectively) did not differ among the three groups. Whereas, pregnancy rate at 120 d pp for Tr 1 (65%) was higher (p<0.05) than that in Tr 2 (30%) or control (30%). The overall pregnancy rate was not significantly different (90, 90 and 75% for Tr 1 , Tr 2 and control, respectively). Days open for cows in Tr 1 (100.3′9) was less (p<0.03) than that in Tr 2 (130.9′9) or control (135.1′10). Results indicate that using PRID device with Ovsynch program had significantly increased pregnancy rate and decreased days open compared to AI at detected estrus after synchronization with GnRH, PRID and PGF2a or synchronization with one injection of PGF2a. (Asian-Aust. J. Anim. Sci. 2003.

Air emissions from sour-gas processing plants and dairy-cattle reproduction in Alberta, Canada

The dispersion of air pollutants from all 231 licensed sour-gas processing plants in Alberta, Canada, was modeled on a monthly basis over a 10-year period (1985–1994). Exposure estimates for sulfur dioxide (SO 2—used as a surrogate for exposure to combusted emissions) then were assigned to 1382 provincial dairy farms using a geographical-information system. Individual average and peak exposure for periods prior to each of 15 months of age and conception (four exposure-averaging periods for each of two dispersion models) were estimated for 163,988 primiparous female dairy-cattle between 1986 and 1994. Monthly or annual average farm-site exposure estimates likewise were assigned to associated herd-level data sets for the biologically relevant period of interest for each of three additional reproductive outcomes: monthly herd-average calving interval, stillbirth risk, and twinning risk. In one of the main-effects models, the maximum (i.e., peak) monthly sour-gas exposure experienced by individual-animals from birth to conception was associated with an increased time to first-calving in the very-highest exposure category (hazard ratio=0.86, 95% CI=0.80, 0.92). This equates to a decreased hazard ( λ) of calving (in each month subsequent to 22 months of age) for the highest-exposure animals ( λ=0.170) versus the zero-exposure animals ( λ=0.198) in a model with referent values for agro-ecological region and season of birth. The dose-response was not consistent across the full range of exposure categories. There was significant ( P=0.003) interaction of emissions with agro-ecological region. After accounting for the interaction, a more-consistent dose-response was evident for some (but not all) agro-ecological regions. This suggests that any effect of emissions on dairy-heifer reproduction is subject to modification by features of soil type, vegetative cover, and/or climate. The increase in monthly herd-average calving interval on farms exposed to the very-highest levels of emissions appeared quite small and of limited practical importance within the range of expected exposures. There was no association between exposure and the risk for twinning. Herds exposed to higher emissions exhibited a slight decrease in risk for stillbirth.

Comparison of Two Estrus Synchronization Programs in a Large, Confinement-Housed Dairy Herd

Estrus synchronization programs have been used to manage reproduction in dairy cattle for many years. These programs involve various protocols for administration of a single hormone or combinations of hormones, but results have varied among programs and herds. Several synchronization programs use injections of prostaglandin F2a (PGF2a).1-3 A commonly used PGF2a program includes per rectal palpation to identify a corpus luteum (CL). Cattle with a CL are injected with PGF2a, observed for estrus, and inseminated only after estrus is detected. This program depends on the palpator's ability to detect a prostaglandin-receptive CL and may not be the most effective way to evaluate CL activity. Other programs that use PGF2a include the administration of 2 injections of PGF2a at selected intervals (usually 12 to 14 days) and insemination at a predetermined time or after cattle are detected in estrus. Both of these programs have resulted in the highest conception rates when cattle were inseminated after being detected in estrus, rather than inseminating at a predetermined time without detection of estrus.4&#x0D; A new ovulation synchronization program5-11 does not require estrus detection. This program (Ovsynch) uses gonadotropin-releasing hormone (GnRH) and PGF2a to synchronize ovulation, which may not be accompanied by detectable signs of estrus. In the Ovsynch program, an initial dose of GnRH is used to synchronize waves of follicles and PGF2a is used to lyse the CL in groups of cattle and synchronize estrus. A second injection of GnRH induces ovulation of the dominant follicle in 85 to 95% of the synchronized cattle.5&#x0D; Pregnancy rates often drop during seasons with high ambient temperature.7 This may be related to heat stress, rather than problems with estrus or ovulation synchronization, because conception rates typically decrease during periods with high ambient temperature.12

Role of selenium and vitamin E in mastitis and reproduction of dairy cattle

The literature would suggest that the selenium requirement for most species of livestock is between 0.05-0.3 ppm (mg/kg) of dietary dry matter. The current requirement for all classes of dairy cattle is 0.30 ppm. Selenium requirements are affected by dietary vitamin E intake, by disease process being prevented, and by the concentration of dietary antagonists including sulfur, iron, copper, and calcium.

The effects of excess rumen degradable protein in ewes on ovulation rate, fertilization and embryo survival in vivo and during in vitro culture.

In a review of the effects of protein nutrition on reproduction in dairy cattle, Ferguson and Chalupa (1989) expressed concern at the low conception rates to first insemination in high-producing dairy cows and suggested that a contributory factor may be an excess of rumen-degradable protein leading to toxic effects of ammonia and its metabolites on gametes and/or the embryo. More recently Elrod and Butler (1993) have provided data suggesting that degradable protein intakes which were 50% above the requirements for maximum microbial protein synthesis reduced embryo survival in dairy heifers. The objective of the present study was to investigate the effect in ewes of varying the amount of rumen degradable protein during the pre-ovulatory progesterone priming phase and the first four days thereafter on ovulation, fertilization, early in vivo and subsequent in vitro ovum development.

Season and Lactation Number Effects on Milk Production and Reproduction of Dairy Cattle in Arizona

Records representing 19,266 Holstein cows from Arizona DHIA data over a 5-yr period were analyzed to determine the effects of season and lactation number on milk production and reproduction. Seasons were winter (December, January, and February), spring (March, April, and May), summer (June, July, and August), and fall (September, October, and November). Traits analyzed by least squares ANOVA were 305-d FCM, complete lactation milk, calving interval, and services per conception. All sources of variation were significant except the interaction between lactation number and season of calving for complete lactation milk. Milk production was depressed for cows calving in summer and fall. First lactation cows had lowest milk production, and highest production occurred in either lactation 4 or 5. Cows calving in spring and summer had reduced reproductive performance, as measured by calving interval and services per conception. First lactation cows had lowest values for both reproductive traits. Previous days dry was negatively related to milk production for spring calvings but was positively related for all other seasons. Cows with higher milk production had reduced reproductive performance. Partial regression coefficients for calving interval and services per conception were 12 d and .25 services per conception per 1000kg of 305-d FCM, respectively. Despite the negative effects of thermal stress, milk production and fertility in this study were not depressed as severely as in previous research reported from Arizona. Calving schedules may be adjusted to minimize the adverse effect of heat stress.

Effect of two superovulation treatments on subsequent fertility in the confined dairy cow

During a 13-month period, 64 lactating dairy cows of 2 genetic lines, Holstein and crossbred, housed indoors year-round were subjected to 2 superovulations and embryo collections within 112 days post partum. Half of the follicle stimulating hormone (FSH) treatments were given in a descending dosage regimen (Treatment A; 6.5 mg, 5.5 mg, 4.5 mg, and 3.5 mg, twice a day, total 40 mg) over 4 days; the remaining half of the treatments were administered in a constant dosage regimen (Treatment B) of 5 mg twice a day over 4 days. There were no significant differences due to treatment in the number of cows stimulated (more than 2 corpora lutea) nor in the number of ova/embryos collected. However, embryos were obtained from more cows (P<0.05) when treated with the descending dosage regimen. More cows (P<0.05) were stimulated by the superovulatory treatment during the first period than during the second period regardless of the regiment used, treatment A or B. More embryos (P<0.05) were obtained from the Holstein line than from the crossbred line. Fifty-two cows were inseminated at least once after the second embryo collection. Overall, 41 cows (79%) became pregnant after the second collection, requiring up to 4 services. These results suggest that the reproduction of dairy cattle housed indoors year-round is not adversely affected by 2 superovulation treatments and embryo collections within 112 days post partum. The question as to whether the administration of FSH is more efficacious in a descending dosage regimen or a constant dosage regimen was not resolved.

Effects of Late Gestation Heat Stress on Postpartum Milk Production and Reproduction in Dairy Cattle

Carry-over effects of late gestation heat stress on postpartum productive and reproductive traits were estimated from DHI records using 341 lactations from six sites in Mississippi. Climatological data were gathered from records of weather stations near the sites. Using multiple linear regression analyses, predictor variables for lactations were age at calving, lactation number, maximum degree-days (above 32.2°C) during the periods 30 and 60 d prepartum, and precipitation 30 and 60 d prepartum. Months and sites were indicator variables. Dependent variables included milk and fat production during early, mid, and late lactation; days to peak lactation; days open; services per conception; and body weight. Age at calving affected milk and fat production in mid and late lactation and services per conception. Degree-days for 60 d prepartum had the greatest negative influence on production variables; its statistical significance was shown in predictions of milk and fat production in early and midlactation. Days open were higher for July than for cows calving in August or September. Sites had effects on many milk and fat measurements and some reproductive traits. These results indicate that heat stress in the last 60 d of gestation has negative effects on some production variables.

Effects of heat stress on production, health and reproduction of dairy cattle

The combined effects of high ambient air temperature, relative humidity, and solar radiation have profound effects on milk yield, growth, reproduction, and cow health. In the lactating cow, total body heat load is significantly escalated by an increase in metabolically-derived heat associated with milk production. Whenever heat gain is greater than heat loss body temperature rises, heat stress results and performance is proportionally reduced.

Impact of Intensive Integrated Reproductive Management Education Programs upon Dairy Producers in Maryland

The objective was to determine if participants in an intensive dairy cattle reproduction workshop learned the desired knowledge and if the DHI management variables concerning herd reproductive efficiency were changed for participants. Sixteen workshops were held across Maryland in 1895 and 1986 for over 200 participants representing 171 herds. Knowledge tests were given at the conclusion of workshops to determine if producers had learned the desired material. The DHI records of participant herds from nine counties were evaluated. Days open, services per conception, days in milk at first service, calving interval, number of cows, percent days in milk, average days in milk, and rolling herd average were collected for each herd. Reproductive performance of participants’ herds was initially improved after the workshop. However, the benefits to workshop participation were transitory, demonstrating the need for continued educational programs. The primary benefit to producers of workshop participation was in the area of improved efficiency in detection of estrus. Producers were also able to learn the desired material, leading to the beneficial effects on herd reproductive efficiency. The need for further educational programs concerning reproduction in dairy cattle was demonstrated, especially in the areas of estrous detection efficiency, interpretation of DHI reproductive records, and retained placenta.

Impact of Site of Inseminate Deposition and Environmental Factors That Influence Reproduction of Dairy Cattle

Uterine body and cornual inseminations (n = 2127) were evaluated over a 3-yr period in Holstein and Jersey cattle. For cornual insemination one-half of each semen dose was deposited approximately 2.5cm into each uterine horn. Conception rate was lower for cervical insemination (39.4%) than uterine body (48.1%) or cornual (49.3%) inseminations. Pregnancy site distribution was equal for both insemination techniques but cervical insemination resulted in 60% right horn pregnancies. Primary housing, service number, inseminator, lactation number, and sire affected conception rate. Older cows were least fertile (31.4%), second service conception rate was lowest (42.6%), and barn housed cattle had a 39.7% conception rate. Days open was affected by primary housing, service number, sire, site of semen placement, and twinning. Twinning increased days open by 10 d. Optimum time for insemination of lactating cows was between 6 and 12h after the initial observation of estrus. From this study we conclude that shallow cornual insemination is as effective as uterine body insemination, and conception rate is optimized when estrus is positively assessed.

The effect of season on reproduction in dairy cattle.

A survey was carried out in North West Tasmania to compare the breeding performance of 2,068 cows in 27 dairy herds--15 herds calving in spring and 12 in autumn. The percentage of cows submitted to artificial insemination for the first time in the first 24 days of the mating period was 87% for the spring calving group and 75% for the autumn calving group. Figures for non-return-to-service rate over the subsequent 21 days were 72% and 55%, respectively. The difference in breeding performance associated with time of calving was not attributable to age, calving to mating interval or on cow condition or daily milk fat yield at 3 weeks (+/- 1 week) after the start of mating.

Reproduction in dairy cattle: Effect of age, cow condition, production level, calving-to-first-service interval and the ‘male’

A study was conducted to determine the effect of various factors on the reproductive performance of approximately 1700 cows in 12 seasonally calving dairy herds in North Western Tasmania. Submission rate (percent of cows submitted for service for the first time in the first 24 days of the mating season) rose from 60% to 97% as cow condition score improved from 3 to 5.5. There was no effect on non-return rates (percent of cows submitted for service for the first time in the first 24 days of mating which did not return to service in the subsequent 21 days), provided condition score was 3.5 or over. Milk fat yield was positively correlated to both submission and non-return rate until milk fat yield exceeded 1.0 kg/day when both fell (from 79% to 71% and from 73% to 38%, respectively). Non-return rate was 46% when the calving-to-first-service interval was less than 40 days after which it rose to a more normal 65%. Submission rates were unaffected by calving-to-first-service interval. There was a significant positive correlation between age and non-return rate, but not between age and submission rate, although submission rate also tended to be higher in older cattle. The proportion of cows having short cycles (less than 18 days) was 18%. In contrast to reports in other species, the presence of the male did not improve oestrous detection or non-return rate of cows in the immediate post-partum period.

Specific Infectious Diseases that Limit Bovine Reproduction

The purpose of this paper is to present a brief overview of the major infectious diseases that limit reproduction in dairy cattle. In addition, a more detailed discussion of 4 reproductive diseases causing much concern among dairymen and practitioners will be presented. These 4 reproductive diseases are leptospirosis, ureaplasma, mycoplasma, and chlamydia. Evidence was presented to show that L. hardjo does not lower conception rate. Evaluation of dairymen's records suggests that conception rate drops during the acute phase of urea plasma granular-vulvitis. Controlled trials using experimental inoculation of ureaplasma, mycoplasma, andchlamydia organisms at the time of breeding are needed to more clearly define the role of these organisms onconception rate.&#x0D;

Advances in Reproduction in Dairy Cattle

In 1956, Willett (185) reviewed developments in reproductive physiology and artificial insemination. His review dealt principally with dairy cattle, but it also encompassed relevant work with other species and summarized the state of the art at that time. Since 1956, many advances have occurred in our understanding of physiological processes that control reproduction. The purpose of this paper is to review those advances and to suggest new developments that may occur in the near future. In the early 1950's, two discoveries provided a basis for much of the research in the past 25 yr. In 1951, researchers at the University of Wisconsin demonstrated that exogenous progesterone could be used to manipulate the estrous cycle in cattle (176). At about the same time, procedures were developed for freezing and long storage of spermatozoa (131). Thus, research emphasis in the 1960's was directed toward understanding both reproductive processes in the cow and factors affecting quanti ty and quality of sperm production by bulls. During the 1960's and early 70's, radioimmunoassay procedures were developed for measuring concentrations of hormones in blood and tissue. This single development launched a broad effort toward characterizing endocrine relationships in both the male and female. In the 1970's, two discoveries provided additional impetus for research in reproduction. First, discovery of the structure of two hypothalamic hormones (thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone (GnRH) set the stage of major studies of the brain as an endocrine organ. Second, research in reproduction led to the discovery of the role of prostaglandins in luteolysis. The mid 1970's saw an upswing-in research on the early embryo, with particular emphasis on embryo transfer, culture, and storage and embryouterine relationships in maternal recognition of pregnancy. Technological advances during the past 25 yr provided tools that allowed research in reproductive physiology to move forward rapidly. Procedures for transmission and scanning electron microscopy provided for new insights into ultrastructural relationships within and between cells. Development of procedures for preparing radioactive compounds with high specific activity, coupled with developments in immunology and cytology, provided methods for measuring extremely small quantities of hormones, hormone receptors, and biological messengers in blood, tissues, and individual ceils. Techniques for in vitro culture of living cells provided systems for precisely controlling various factors that influence development and function of ova, embryos, and hormonesecreting cells. Furthermore, new techmques for separation and purification of products produced by cells allowed for identification of hormones and biological messengers that were not known in the early 1950's. Finally, advances in technology of computers made data storage, retrieval, and handling a simpler task than in the early 1950's when nearly all data were handled manually.

Managing Reproduction in Dairy Cattle: III. Changes in Culling Patterns with Increased Reproduction

The effects of a management system on changes in culling patterns were determined with observations from 1182 lactations. From 1968 to 1972, 307 of 471 cows were culled. Management was synchronization of estrus of lactating dairy cattle by administration of a progestogen, melengestrol acetate, at 1 mg/head per day usually for 14 days, beginning between 14 and 55 days postpartum. The rate of culling in the lactation coincident with treatment was less for treated than for control cows (16% versus 25%). Of the treated cows culled in the lactation of treatment, 22% were removed for failure to reproduce, contrasted to 31% of the control cows culled for the same reason. Of the control cows, 20% were removed for low milk production, contrasted to 42% of the treated cows which were removed for the same reason. Culling for other reasons (dairy sale, death, injury, etc.) and for mastitis or poor udder were similar for treated (18% and 18%) and control cows (24% and 25%). Administration of melengestrol acetate for several lactations had no detrimental effects. Culling of treated cows for reproduction remained below that for control cows. Culling for milk production of treated cows decreased and culling for mastitis or poor udder increased slightly. Cows which were culled in the first year following complete removal of melengestrol acetate had a culling pattern similar to that for the control cows. Overall the progestogen system for managing reproduction shifted cause of culling from reproduction to milk production.

Managing Reproduction in Dairy Cattle. II. Response of Cows to Progestogen Treated Herdmates during the Postpartum Period

Sixty-eight lactating Holstein cows were handled as one unit but were either fed melengestrol acetate for 14 days or were contemporary controls. Cows that calved in a 21-day period were assigned to a treatment group. Those that calved during the subsequent 21 days served as controls and received no treatment. The alternating assignment was continued for 6 mo. Treated cows were between 14 to 35 days postpartum at the beginning of the feeding period. Data from all cows, combined, showed a decrease in days open (120 to 92) and services per conception (2.7 to 1.5) as compared with their previous year's record. The 34 control cows exhibited estrus over a period which coincided with that of 91% of the treated animals, with a slight delay in occurrence of first estrus. The observations suggest that control cows responded in some way to the treated cows in the early stages of the postpartum period.

Managing Reproduction in Dairy Cattle: I. Progestogens for Control of Estrus in Dairy Cows

Two experiments studied the effectiveness of medroxyprogesterone acetate (MAP) and melengestrol acetate (MGA) for control of estrus in normal and anestrous dairy cows. A third experiment investigated the use of MGA for controlling estrus during 17 successive 3-week breeding periods. In Experiment 1, 73 anestrous cows received MAP (180 mg/day) or a placebo for 10 days. Conception rate for first service, total conception rate, and services per conception were 59, 88,’ 1.7 and 54, 74, 1.8 for MAP and control groups. In Experiment 2, 232 cows in four herds were classified normal or anestrous according to estrous detection during the first 7 weeks postpartum. Beginning on Day 48 postpartum, some cows received MGA (1 mg/day) for 10 days while others served as controls. The mean interval from calving to first service, average days open for cows conceiving, and services per conception were 76, 107, 2.4; 76, 123, 2.5; 74, 98, 1.9 and 75, 107, 2.0 for MGA-normal, MGA-anestrous, control-normal and control-anestrous groups. Conception rates for first service were between 50 and 53% for normal cows and between 35 and 39% for anestrous cows irrespective of hormone treatment.In Experiment 3, 268 cows which calved in 17 successive 3-week periods in three herds were assigned to MGA or control groups. Some MGA cows received a single 14-day treatment (MGA-lX) while others received a double sequence (MGA-2X). Eighty-six per cent of the MGA cows and 60% of the controls were in estrus within 30 days following MGA withdrawal. Ninety-two per cent of the MGA cows were synchronized in two periods of 7 and 5 days. Cows which received the double sequence of MGA were synchronized to a greater degree than MGA-1X animals. The interval from calving to first service, average days open for cows conceiving, and services per conception were 80, 102, 1.8; 72, 102, 2.1 and 72, 97 and 1.9 for control, MGA-1 X and MGA-2X groups. The MGA reduced the variation among herds in interval from calving to first service and average days open. Progestogen administration did not affect milk yield. The system for controlling estrus in groups of cows could be beneficial as part of a total system to manage for a high reproductive rate in large herds.

Developments in the Physiology of Reproduction of Dairy Cattle and in Artificial Insemination

A study of the physiology of reproduction in animals and of other fields of natural science began with the dawn of man. His existence depended upon his skill in killing animals for food, and because of this critical necessity he developed hunting lore, which included knowledge of the mating and young-bearing habits of wild life. Observations of animals recorded on walls of caves, and undoubtedly wr i t i ngs on natural science that have been lost, antedate Aristotle (384-322 B.C.) by as much as Ar i s to t l e antedates our time. In spite of the antiquity of natural science, man has learned more about reproduction of the bovine E. L. Wil le t t during the past half-century than was learned in all previous ages. This statement applies as well specifically to artificial insemination as it does generally to reproduction. Actually, little information was available concerning reproduction of cattle at the time of the founding of the American Dairy Science Association in 1906. Scientists at that time, however, were beneficiaries of a rich heritage of fundamental information concerning reproductive processes. This paper, firstly, gives the reader a glimpse of this heritage, then outlines progress during the last half-century concerning knowledge of reproduction with special reference to the bovine, and lastly makes a few remarks and predictions.