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PubMed1989

Ovarian responses to intramuscular or intravenous administration of prostaglandin F2 alpha in control and FSH-treated beef heifers.

Sixty Simmental crossbred heifers 18 to 20 mo of age were detected in estrus and assigned at random to a 2 x 2 factorial design study with 30 controls, and 30 given FSH. Half of each group was given prostaglandin F2 alpha (PGF) i.v. and the rest i.m. Injections of follicle-stimulating hormone were started on d 7 to 14 of an estrous cycle and continued for 5 d or until ovariectomy; PGF was administered either i.v. or i.m. at 48 (25 mg) and 60 (15 mg) h after the initial FSH injection. Control females received a similar PGF treatment on a day between d 9 and 15 of the estrous cycle. Blood samples were collected from all animals immediately before PGF administration and every 12 h thereafter until ovariectomy. Within each of the four experimental subgroups, ovariectomies were performed at either 24, 48 or 72 h (five/time group) after initial PGF injection. Ovarian and corpus luteum (CL) weights were recorded as well as number and size of follicles and number of ovulations. Regression of the CL was slower (P less than .05) after administration of PGF i.v. than i.m. (CL weight was 2.6 vs 3.3 +/- .2 g for i.m. and i.v. groups, respectively). Exogenous FSH increased estradiol-17 beta (E2) concentrations, and FSH-treated heifers had more (P less than .05) early ovulations than control heifers did. Ovulations in FSH-treated heifers had begun to occur by 24 h after i.v. and i.m. PGF injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Treatment of noncyclic lactating dairy cows with progesterone and estradiol or with progesterone, GnRH, prostaglandin F2 alpha, and estradiol.

The efficacy of two programs for treating noncyclic cows was compared. In trial 1, 478 cows in five herds were randomly divided into two groups. Cows in one group (C group) were treated with an intravaginal progesterone device for 8 d followed in 48 h by 1 mg of estradiol benzoate to cows that had not been detected in estrus since device removal. Those in the other group (CGP group) were treated with progesterone and estradiol as for the C group plus 10 micrograms of a GnRH agonist (buserelin) at device insertion and 25 mg of PGF2 alpha 7 d after device insertion. In trial 2 with 729 cows in nine herds, the treatments were similar to those in trial 1 except that the duration of progesterone treatment was 7 d. No significant difference was found between trials and results from both trials were combined. Compared with C group cows, CGP group cows had a greater estrous response rate (93.2 vs. 89.1%), a greater conception rate to first artificial insemination (AI, 47.1 vs. 29.4%), marginally lower conception rate to second AI (52.9 vs. 59.7%), lower nonpregnancy rate (8.3 vs. 11.1%), and shorter intervals from the start of breeding to conception by AI (9.8 vs. 15.3 d) or by AI or natural mating (21.6 vs. 26.3 d). The treatment protocol used for the CGP group achieved better reproductive performance than that used for the C group.

Animals↗

PubMed2002

Ovarian structures and circulating steroids in heifers and lactating cows in summer and lactating and dry cows in winter.

Two experiments compared follicular and luteal development and circulating steroid concentrations from induced luteolysis to ovulation in lactating Holstein cows (n = 27; 40.0 +/- 1.5 kg milk/day) vs. nulliparous heifers (n = 28; 11 to 17 mo-old) during summer (Experiment 1), and in lactating (n = 27; 45.9 +/- 1.4 kg milk/d) vs. dry cows (n = 26) during winter (experiment 2). All females received PGF2,, 6 d after ovulation and were monitored until next ovulation by daily ultrasound and assay of serum progesterone (P4) and estradiol (E2). Every female was used two or three times. In Experiment 1, lactating cows had high incidence of multiple ovulation (63.5%) compared with heifers (1.3%). Among single ovulators, there was no difference in maximal size of ovulatory follicles between lactating cows and heifers (15.8 vs. 16.5 mm, respectively). However, lactating cows had lower peak serum E2 (8.6 vs. 12.1 pg/ml), took longer to ovulate after luteolysis (4.6 vs. 3.8 d), developed more luteal tissue volume (7,293.6 vs. 5,515.2 mm3), and had lower serum P4 on d 6 after ovulation (2.0 vs. 3.0 ng/ml) than heifers (data included multiple ovulators). In experiment 2, multiple ovulations were similar between lactating and dry cows (17.9 vs. 17.2%, respectively). Peak serum E2 was also similar between lactating and dry cows (7.6 vs. 8.5 pg/ml) although lactating cows had larger ovulatory follicles (18.6 vs. 16.2 +/- 0.4 mm). Lactating cows took longer to ovulate (4.8 vs. 4.2 d), developed more luteal tissue (7,599 vs. 5,139 +/- 468 mm3), but had similar serum P4 (2.2 vs. 1.9 ng/ ml) compared with dry cows. Therefore, lactating cows had similar or lower circulating steroid concentrations than dry cows or heifers, respectively, despite having larger ovarian structures.

Animals↗

PubMed2003

Concentrations of progesterone in milk of cows administered an intravaginal progesterone insert.

Milk from pregnant cows contains concentrations of progesterone (P4) considered safe for human consumption. The objective of this study was to determine if concentrations of P4 in milk during administration of an intravaginal progesterone insert (CIDR insert) are less than concentrations of P4 in milk associated with pregnancy. Results have implications for human use of milk from cows receiving CIDR inserts. Holstein cows (N = 64; > 40 and < 150 d after calving) were administered 25 mg of PGF2alpha i.m. (study d 0) and 20 cows detected in estrus from 2 to 4 d later were assigned randomly to either control (N = 10; no further treatment) or CIDR insert (N = 10; 1.38 g of P4) inserted on study d 17 (14 +/- 1 d after estrus) and removed 7 d later. Composite milk samples were collected contemporaneously from each of the 20 estrous cycling cows and from 10 pregnant cows (> or = 60 and < or = 220 d of gestation) twice daily from study d 17 to 27. Concentrations of P4 in defatted milk samples were quantified using a validated radioimmunoassay. Mean logs of areas under the curve of concentrations of P4 from the afternoon on study d 17 through the afternoon on study d 27 were 3.05 ng day/ml for control, 3.33 ng day/ml for CIDR insert, and 3.81 ng day/ml for pregnant cows. Therefore, increased P4 due to pregnancy was 0.76 ng day/ml (3.81-3.05), whereas the increase in P4 due to CIDR insert was only 0.28 ng day/ml (3.33-3.05). Applying a 95% confidence interval to 0.28 ng day/ml provided an upper value of 0.70 ng day/ml, lower than the increase due to pregnancy. Because milk from pregnant cows is considered safe for human consumption, it follows that milk from cows administered CIDR inserts should also be considered safe, based on concentrations of P4.

Administration, Intravaginal↗

PubMed2004

Production and health of pasture-fed dairy cattle following oral treatment with the ionophore lasalocid.

The aim of the study was to evaluate the effect of feeding the ionophore lasalocid on the productivity and health of seasonally calving, pasture-fed dairy cows. Dairy cows (n = 1020) from 4 herds were enrolled in a split-herd, prospective intervention study. Cows were blocked by breed and age, ranked on previous production, and then assigned to 2 treatment groups. Treatment cows were each exposed to 300 to 350 mg of lasalocid/d commencing 3 wk before and ending 18 wk after the start of the seasonal calving period. Milk production was determined on 3 occasions for each cow at approximately monthly intervals (herd tests 1 to 3), body condition score was determined fortnightly, and all disease occurrences were recorded. Lasalocid treatment increased milk volume milk protein and milk fat production by approximately 2%, without altering milk composition. Fewer lasalocid-treated cows than control cows (7.3 vs. 11.6%, respectively) were diagnosed with clinical mastitis. Lasalocid treatment of pasture-fed dairy cows resulted in reduced mastitis incidence and increased milk production without changes in body condition or negative effects on metabolic processes as monitored by metabolite concentrations.

3-Hydroxybutyric Acid↗

PubMed1976

Prenancy diagnosis in dairy cattle by progesterone concentration in milk.

Concentration of progesterone in whole milk was used to diagnose pregnancy in lactating dairy cows. Milk samples were taken 21 to 22 days postbreeding and analyzed for progesterone by radioimmunoassay. Progesterone in milk greater than 11 ng/ml, 8 to 11 ng/ml, and less than 8 ng/ml was used classify animals as pregnant, questionable, and not pregnant. In this classification for 123 cows, 67 were classified pregnant, 7 questionable, and 49 not pregnant. A comparison of progesterone diagnosis with actual calving results showed agreement of 73 and 98% for the cows classified as pregnant and not pregnant. Thirteen of 19 animals, in which there were discrepancies between diagnoses by milk progesterone and calving results, were not detected in estrus within 30 days after breeding. One animal classified not pregnant by milk progesterone was pregnant.

Animals↗

PubMed1979

Pregnancy rate in dairy cows inseminated on the basis of electronic probe measurements.

A new vaginal probe with two pairs of parallel electrodes 90 degrees apart was designed with a switching arrangement so that electrical resistance (ohms) of the dorsal and the ventral areas of the anterior vagina could be monitored separately during the estrous cycle. Three inseminators probed cows during February--April, 1977, in nine herds in stanchion barn housing. Cows not seen in estrus by 40 to 60 dyas after calving were probed every 3rd day. At each dairyman's option normal cows with a low porbe reading were inseminated. Controls consisted of cows seen in estrus by the dairyman and reported for insemination in the routine manner. The diagnosed pregnancy rate for 86 first service controls was 49% versus 52% for 58 cows not seen in estrus, but identified by low probe readings. Cows varied in electrical resistance at breeding, but the fact that pregnancy rates were equivalent in the two groups is interpreted to mean that the probe was as effective in identifying cows suitable for insemination as was visual observation of estrus by dairymen.

Animals↗

PubMed1979

Relationship of the estrous cycle to milk composition.

The relationship of the estrous cycle to milk composition was examined in 15 Holstein cows in first lactation which were approximately 45 days postpartum. Composite milk samples were collected twice daily and analyzed for progesterone, fat, protein, total solids, sodium, potassium, magnesium, calcium, and somatic cells. Milk progesterone was minimal (less than ng/ml) from day -1 to day 2 (day 0 = estrus) of the estrous cycle and then increased at a relatively constant rate through day 15. Milk yield and sodium and magnesium concentrations of the milk varied with days of the estrous cycle. Mean milk yield was highest and sodium and magnesium concentrations were lowest on day 1. However, sodium concentration of the milk was the only component that varied significantly during the 3 days centered on estrus (days -1, 0, and 1). No other milk component changed significantly during the estrous cycle. Although milk yield and composition varied during the estrous cycle, none of these components appeared to be a practical indicator of estrus.

Animals↗

PubMed1980

Accuracy of predicting stages of bovine estrous cycle by gross appearance of the corpus luteum.

Four readily identifiable changes in appearance of corpora lutea (Stages I to IV) occur during a bovine estrous cycle. Accuracy of estimating the stage of an estrous cycle by appearance of corpora lutea was determined in a double-blind study. One investigator observed estrus in a group of heifers while another with no prior knowledge of reproductive histories of the heifers estimated stage of the estrous cycle by visual inspection of their corpora lutea. Stage of the estrous cycle (Stage I, days 1 to 4; Stage II, days 5 to 10; Stage III, days 11 to 17; Stage IV, days 18 to 20) was estimated correctly in 41 of 48 heifers. The correlation between estimated and actual days of the estrous cycle was .81. In addition, concentrations of progestins and weights of corpora lutea during estimated stages of the estrous cycle were similar to many other investigations. Stages of the estrous cycle in heifers can be estimated from appearance of corpora lutea.

Animals↗

PubMed1984

Estrus-related odors in body fluids of dairy cows.

Six experiments were to test for estrus-associated odors in 1) swabs of the vulva and vestibule, 2) fluids from deep in the vagina, 3) naturally voided urine, 4) urine obtained from the bladder by catheter, 5) milk, and 6) blood plasma. Tests were with dogs trained to identify vaginal fluids from estrous cows. In the tests, dogs were walked along lines of seven sample bottles consisting of samples from two estrous cows, two luteal-phase cows, one vaginal swab from estrous cows used as a standard, and two blank sample bottles. Correct responses to fluids from estrous cows averaged 97, 86, 96, 97, 99, and 94% for the six fluids listed. Incorrect responses to fluids from luteal-phase cows were 2, 1, 1, 1, 1, and 8%. Responses to blank samples were usually zero. Results indicate that odors associated with estrus are spread throughout the cow's body fluid.

Animals↗

PubMed1984

Onset of estrus in dairy cows maintained indoors year-round.

During 6 mo two active testosterone-treated females fitted with chin-ball markers and paint were used to ascertain the time of onset of estrus in 56 cows of three genetic lines and at various stages of lactation. The two treated females were rotated every 24 h, and two colors of paint were used, one color for night, 1800 to 0600 h, and the other for day, 0600 to 1800 h. The incidence of behavioral signs of estrus, standing, mounting activity, and mucus discharge, also was recorded. More cows (65%) came into estrus during the night, and only 78% of the total marked cows, assumed to be in estrus, were observed standing by the herdsman, indicating that 22% of the cows would not have been observed in estrus by early morning and late afternoon observation by the herdsman. Similarly, of the marked cows a mucus discharge was observed for 60% and mounting activity by 62%. Neither parity nor days postpartum affected either time of onset of estrus or other overt signs of estrus. Differences among the genetic lines for standing and mounting activity were unexplained.

Animal Husbandry↗

PubMed1986

Relationships of sexual activities in estrous cows to different frequencies of observation and pedometer measurements.

Sexual activities were observed continuously for 120 h in Holstein dairy cows during moderate climate. Pedometer measurements of motor activity were correlated with total activities initiated, total activities received, mounts received, and time in estrus. Twelve of 14 individual sexual activities also were correlated on a within-cow basis with pedometer-measured increases in motor activity; disoriented mounts and licking front were not correlated to pedometer increases. Although observations of four 1-h and four or six 30-min observations accounted for greater variation, pedometer increases in activity accounted for as much variation in total sexual activities as periodic observations of 30 min or 1 h for 1 to 3 X /d. Combining periodic observations with pedometer measurements resulted in greater coefficients of determination for analyses of sexual activities than with each individual factor. Sexual activities and pedometer increases also were correlated positively with body condition score and day postpartum, and they were correlated negatively with milk production and body weight change since calving. Although mounting and total sexual activities were shifted significantly from expected on a quartile basis, shifts were probably not of practical significance and provided little evidence for more frequent occurrence of estrous activity during nocturnal periods. Rather, the most marked decrease in mounting and total sexual activities occurred at milking and feeding times, indicating that dairy farmers should be more concerned with disruptions of activities by management practices rather than nocturnal occurrence of estrus.

Animals↗

PubMed1988

On-farm milk progesterone tests.

Results from milk progesterone assays can provide ovarian information, making it possible to monitor the reproductive status of the cow. Rapid, simple, and accurate on-farm milk progesterone tests are commercially available. Procedures for performing milk progesterone tests are specific for each test; however, principles of testing are similar. On-farm tests are designed to determine the relative progesterone concentration ("high" or "low") rather than obtaining a precise concentration. Evaluation of results is based on either a color or agglutination reaction with comparison to known standards. Potential uses of progesterone testing in a reproductive management program are: 1) identifying errors in detection of estrus, 2) predicting time of estrus, 3) assisting in pregnancy diagnosis, 4) differentiating types of ovarian cysts, and 5) evaluating response to endocrine therapy.

Animal Husbandry↗

PubMed1990

Double insemination and gonadotropin-releasing hormone treatment of repeat-breeding dairy cattle.

Our objective was to determine if double inseminations during the same estrous period of dairy cattle eligible for their third or fourth service (repeat breeders) would improve pregnancy rates equivalent to injections of GnRH given at the time of AI. Repeat-breeding, lactating cows from six herds (five herds in the San Joaquin Valley of central California and one herd in northeast Kansas) were assigned randomly to four treatment groups when detected in estrus: 1) single AI plus no injection, 2) single AI plus 100 micrograms GnRH at AI, 3) double AI plus no injection, or 4) double AI plus 100 micrograms of GnRH at AI. Inseminations were performed according to the a.m.-p.m. rule. The second AI for the double AI treatment was given 12 to 16 h after the first AI. Injections of GnRH were given intramuscularly immediately following the single AI or the first AI of the double AI. Pregnancy rates of cows given a single AI and hormone injection were numerically higher in all six herds than those of their herdmates given only a single AI. In five of six herds, the pregnancy rates of cows given a double AI and hormone injection were numerically higher than pregnancy rates of their herdmates given only a double AI. Overall pregnancy rates for the four treatments were 1) 112/353 (32.1%), 2) 165/406 (41.6%), 3) 119/364 (33.5%), and 4) 135/359 (37.5%). Gonadotropin-releasing hormone increased pregnancy rates of repeat breeders compared with controls given only a single AI. No further benefit beyond the single AI was accrued from the double AI treatment, with or without concurrent hormone administration.

Animals↗

PubMed1994

A demonstration project of interdisciplinary dairy herd extension advising funded by industry and users. 3. Impact on management practices.

The objectives of this 24-herd, demonstration project of integrated problem solving and extension advising were 1) to evaluate dairy production management practices, 2) to formulate recommendations for guiding producers to correct management deficiencies, and 3) to measure the rate of practice adoption. Management evaluations focused on herd nutrition and forage crops, mastitis control and milking equipment, reproduction, and herd health. Sixty-eight management practices or milking equipment components were evaluated on each farm. A total of 216 recommendations were made in nutrition and forage crops as follows: calf and heifer management, 89; forage crops, 73; dry cows, 26; lactating cows, 19; and general, 9. The least adopted suggestions for nutrition and crops were for forage crop management. A total of 283 recommendations were made in mastitis management or milking equipment as follows: milking practices, 90; milking equipment, 90; general mastitis control, 61; environment, 32; calf management, 9; and stray voltage, 1. Producers most resisted updating and maintaining milking equipment within the milking management area. Detection of estrus was the focus of reproductive management advising. A total of 80 practices were recommended as follows: one person responsible, 24; specific location, 24; specific time, 24; and regular veterinary visits, 10. Designation of a specific site was the least adopted of these recommendations. Overall, 419 of 581, or 72%, of all recommendations were adopted.

Animal Feed↗

PubMed1994

Effectiveness of short-term cooling and vitamin E for alleviation of infertility induced by heat stress in dairy cows.

Four experiments were performed to determine whether cooling cows during final maturation of oocytes and early embryonic development or injection of vitamin E at AI prevented adverse effects of heat stress on pregnancy rates in lactating Holstein dairy cows. In Experiment 1, cows were placed in a cooling facility containing sprinklers and forced ventilation or received shade only from 2 to 3 d before until 5 to 6 d after breeding. Although cooling had no effect on detection of estrus, pregnancy rates were increased slightly for cooled cows (8 of 50 cows; 16.0%) compared with those for cows exposed to shade only (2 of 32 cows; 6.2%). In Experiments 2 through 4, cows were administered 3000 IU of vitamin E or placebo i.m. at AI during two consecutive summers and one winter in Florida. Administration of vitamin E had no consistent beneficial effect on pregnancy rates during summer or winter. Short-term cooling improved pregnancy rates slightly in heat-stressed cows, but administration of vitamin E had no beneficial effects on pregnancy rates during heat stress. Further improvements in cooling schemes during early pregnancy and delineation of antioxidant effects are necessary before such systems become practical for improvement of fertility in heat-stressed dairy cows.

Animals↗

PubMedDate not supplied

Exposure of thawed frozen bull sperm to a synthetic peptide before artificial insemination increases fertility.

We evaluated the effect on fertility of in vitro exposure of thawed frozen bull sperm to synthetic FertPlus peptide prior to artificial insemination (AI). The peptide represented a 60-amino acid sequence within rat prosaposin. Commercial cryopreserved semen was from three Holstein bulls. Onset of estrus in groups of Holstein nulliparous heifers was synchronized via injection of prostaglandin F2-alpha, and heifers were scheduled for AI 8-24 hours after estrus was detected. Semen was thawed, diluted to 2.4 x 10(6) sperm/ml with buffer, and split to provide control and exposed aliquots (0 or 30 microM peptide) that were incubated at 37 degrees C for 10 minutes and then were held at 32 degrees C. The two aliquots of semen then were used on an alternate basis 2-65 minutes later to inseminate females. Each AI (one per female) involved the deposit of approximately 250,000 sperm into each uterine horn. This procedure for AI was used to reduce the pregnancy rate with control semen to below the maximum value for a given bull and to facilitate detection of any beneficial effect of the peptide. For each bull, approximately 32 heifers were inseminated with control semen, and approximately 32 heifers were inseminated with peptide-exposed semen. Pregnancy was evaluated ultrasonically approximately 60 days after AI. After excluding one group of heifers with unusually low fertility, averaged across all animals, a 29% increase in pregnancy rate resulted from exposure of sperm to peptide (P < 0.04; one-tailed chi-square test; means were 48 vs. 62%). Pregnancy rates for the three bulls for control and peptide-exposed semen, respectively, were 42 and 62%, 44 and 64%, and 56 and 61%; means in the first two pairs of values tended to differ (P approximately equal to 0.10). These observations should be confirmed with sperm from other bulls used in a more conventional manner. However, with insemination of a limiting number of cryopreserved sperm, brief exposure of the thawed bull sperm to FertPlus peptide appeared to improve fertility dramatically.

Animals↗

PubMed1976

[Vaginal cytology studies on the determination of the onset of estrus cycle post partum in sheep].

State of vaginal cells and arborisation grade of cervical mucus were studied in 364 Merino ewes of meat type from the 7. day ante partum. The Pundel modified Shorr-straining method and the Papanicolaou-straining method were used for differentiation of the cells (casal-, parabasal-, intermediate-and superficialcells). Near the 44., 54. and 70. day post partum a maximum of superficialcells and simultaneously a high grade of cervical mucus arborisation in elongating cyclic intervals can be observed in lactating ewes. In conclusion an early weaning of lambs between the 40. and 50. day post partum is considered to be in aggreement with cyclus.

Animals↗