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PubMed1997

Prolonged increased concentrations of 17beta-estradiol associated with development of persistent ovarian follicles do not influence conception rates in beef cattle.

Objectives were to evaluate conception rates and time to estrus following cessation of treatments designed to either cause prolonged elevated concentrations of 17beta-estradiol associated with development of persistent ovarian follicles or to inhibit elevated concentrations of 17beta-estradiol and development of persistent ovarian follicles. Beef heifers (n = 80) and 2-yr-old nonlactating cows (n = 39) were stratified by age, blocked by estrual status (previously exhibited estrus or anestrus) and assigned to receive either 1) four norgestomet implants (4 Norg; n = 59) for 9 d (d 0 = treatment initiation) or 2) one norgestomet implant from d 0 to 7 and three additional norgestomet implants from d 7 to 9 (1 + 3 Norg; n = 60). All animals received PGF2alpha on d 0 to lyse corpora lutea. All implants were removed on d 9 followed by estrus detection every 6 h for 7 d following implant removal. Females exhibiting estrus were artificially inseminated 6 to 12 h after detection of estrus. A treatment x day interaction (P < .01) for concentrations of 17beta-estradiol from d 0 to 9 of the experiment with elevated 17beta-estradiol occurring in females treated with 1 + 3 Norg implants. The interval from treatment withdrawal to estrus was longer (P < .01) in females treated with 1 + 3 Norg (105 h) than in those treated with 4 Norg (61 h). Synchrony of estrus among anestrous females was greater (P < .10) in females treated with 4 Norg (97%) than in females treated with 1 + 3 Norg (67%) but was similar in estrual females. Conception rates (number conceiving to AI/number bred by AI) did not differ (4 Norg = 67%; 1 + 3 Norg = 72%; P > .10). Pregnancy rates (number conceiving to AI/number in treatment group) also did not differ between treatment groups of either estrual or anestrous females. Conception rates are not compromised in females that develop persistent ovarian follicles and have prolonged elevated concentrations of 17beta-estradiol when persistent ovarian follicles are not allowed to ovulate.

Animals↗

PubMed1991

Relationships among milk yield, metabolism, and reproductive performance of primiparous Holstein cows treated with somatotropin.

Thirty-two primiparous Holsteins were assigned to receive 0, 5.15, 10.3, or 16.5 mg/d recombinant bST. Treatment began between 28 and 35 d postpartum and continued until 60 d prior to next expected calving or 400 d postpartum. Metabolic hormones and metabolites were measured in blood weekly during the first 10 wk of treatment, and progesterone was measured in milk twice weekly to assess ovarian activity until conception. Milk production (305 d, actual) was 8350 +/- 562, 8348 +/- 515, 9571 +/- 515, and 9070 +/- 515 for cows given 0, 5.15, 10.3, or 16.5 mg/d and did not differ statistically. Insulin, glucose, NEFA and blood urea nitrogen were not influenced by dose of bST. However, insulin-like growth factor-I increased linearly with dose of bST. Days from parturition to first detected estrus, days open, and services per conception did not differ among groups; however, days from parturition to first service increased with dose of bST. Rate of detection of estrus decreased with dose of bST, resulting in a longer interval to first insemination. The lower rate of detection of estrus in bST-treated cows may have been associated with reduced expression of estrus. Additional statistical analyses were conducted to determine the relationship between metabolism, milk production, and reproduction over all doses of bST. There was a negative correlation between 305-d milk yield and glucose (r = -.44) and insulin (r = -.46) concentrations during 30 to 100 d postpartum. In stepwise regression analyses, insulin accounted for 21% of the variance in 305-d milk yield. Glucose and NEFA accounted for 18% of the variance in days open, and there was a negative correlation (r = -.32) between glucose and days open. Days open and milk production were not correlated.

Animals↗

PubMed1983

Factors affecting reproductive performance of dairy cows first inseminated after five weeks postpartum.

Various factors influencing reproduction of 307 Holstein cows were evaluated. Sources of variation of several measures were estrous certainty, time of day of detected estrus and insemination, method of thawing semen, ease of cervix penetration, presence of clear mucus at insemination, service number, service sire, inseminator, age of cow, maximum ambient temperature on the service date, and milk yield. Interval to first service of older cows was longer than of younger cows and shorter for cows with higher milk yield. Conception rate was higher for inseminations before noon than after noon and tended to be lower at inseminations when milk yield was at the extremes (low or high). Rate of conception was similar for cows whether inseminated at early or later postpartum intervals. More services were required by cows that were inseminated when milk yield was at the extremes (low or high). Fewer days open were associated with fewer total services and younger age at conception. Cows inseminated with semen thawed in hot (65 degrees C, 7 to 10 s) or warm (35 degrees C, 30 s) water conceived earlier postpartum than did those inseminated with semen thawed in the cow. Submitting cows for insemination after detection of standing estrus, mounting activity, or less certain symptoms of estrus had no adverse effect on fertility or days open.

Animals↗

PubMed2002

Use of estradiol cypionate in a presynchronized timed artificial insemination program for lactating dairy cattle.

Experiment 1 evaluated pregnancy rates when estradiol cypionate (ECP) was used to induce ovulation as part of a timed artificial insemination (TAI) protocol in comparison to Ovsynch for lactating dairy cows in Florida (n = 371) and Texas (n = 321). Cows were presynchronized with two injections of PGF2, (25 mg, im) given 14 d apart with TAI protocols beginning 14 d after the second injection of PGF20. The TAI protocols consisted of an injection of GnRH (100 microg, im) followed by PGF2alpha 7 d later. Then, cows either received an injection of GnRH (Treatment I, Ovsynch) at 48 h after PGF2alpha and inseminated 16 to 24 h later or received an injection of ECP (1 mg, i.m.) at 24 h after PGF2alpha, (Treatment II; Heatsynch) and inseminated 48 h later. In Florida, pregnancy rates after TAI were 37.1 +/- 5.8% for Ovsynch compared with 35.1 +/- 5.0% for Heatsynch. In Texas, pregnancy rates were 28.2 +/- 3.6% for Ovsynch and 29.0 +/- 3.5% for Heatsynch. Overall pregnancy rates did not differ between Ovsynch and Heatsynch treatments. In Experiment 2, estrus and ovulation times were determined in lactating dairy cows submitted to the Heatsynch protocol. Frequencies of detected estrus and ovulation after ECP were 75.7% (28/37) and 86.5% (32/37), respectively. Mean intervals to ovulation were 55.4 +/- 2.7 h (n = 32) after ECP and 27.5 +/- 1.1 h (n = 27) after onset of estrus. Estrus occurred at 29.0 +/- 1.8 h (n = 28) after ECP. It is recommended that any cow detected in estrus by 24 h after ECP injection be inseminated at 24 h and all remaining cows be inseminated at 48 h because 75% (n = 24/32) of the ovulations occurred between > or = 48 h to < or = 72 h after ECP. Synchronization of ovulation and subsequent fertility indicated that estradiol cypionate could be used to induce ovulation for successful timed insemination.

Animals↗

PubMed2001

Effects of postweaning dietary energy source on reproductive traits in primiparous sows.

An experiment was conducted to study the effects of major dietary energy source fed from weaning to ovulation or from ovulation to d 35 of pregnancy on reproductive traits in primiparous sows. Dietary energy sources were used to manipulate the plasma insulin concentration. One hundred thirteen sows were used in a split-plot design. From weaning to ovulation sows were fed at two times maintenance either a diet with tallow (Fat) or maize starch plus dextrose (Starch) as the major energy source. From ovulation onward, sows within each dietary group were alternately reassigned to either the Fat or the Starch diet and were fed at 1.25 times maintenance. Estrus detection was performed three times a day from d 3 to 9 after weaning and sows were inseminated each day of standing estrus. On d 35 of pregnancy, the sows were slaughtered and their reproductive tracts were removed. Plasma insulin concentration was higher in sows fed the Starch-rich diet than in sows fed the Fat-rich diet on d 4 after weaning (1.30 vs 0.97 ng/mL, P = 0.08) and on d 32 of pregnancy (1.20 vs 0.51 ng/mL, P < 0.001). Plasma glucose and IGF-I concentration on d 4 after weaning and d 32 of pregnancy did not differ between sows on the two dietary energy sources. The percentage of sows exhibiting estrus within 9 d after weaning was 52 and 67% for the Fat and Starch diet before ovulation, respectively (P = 0.11), whereas the weaning-to-estrus interval was 134 vs 123 h, respectively (P = 0.12). Survival analysis showed that sows fed the Fat-rich diet had a 1.6 times higher risk to remain anestrous until d 9 after weaning than sows fed the Starch-rich diet (P = 0.04). No effect of dietary energy source, either before or after ovulation, on uterine, placental, or embryonal development on d 35 of pregnancy was found. It can be concluded that the dietary energy source provided after weaning can affect the risk of sows to remain anestrous but does not affect uterine, placental, or embryonic traits.

Animal Feed↗

PubMed1998

Factors affecting reproductive performance in Ontario dairy herds.

Data were collected on reproductive, health and production events in 45 dairy herds in southwestern and eastern Ontario, Canada, from July 1990 to July 1993. Mean and median days in milk at first estrus, at first service, and at conception were 85.1 and 83.9, 94.0 and 88.9, and 126.3 and 115.5 d, respectively. The mean estrus detection rate was 48.3%, with a minimum of 28.4% and a maximum of 64.2%. The mean overall conception rate was 46.7%, with a minimum of 29.8% and a maximum of 70.7%. The most commonly used used therapeutic agents were GnRH (11.5% lactational incidence risk) and PG (13.1% lactational incidence risk). Estrus management accounted for the largest portion of PG use in the herds studied (69.4%). Results of a two sample t-test indicated no significant difference in reproductive performance among herds housed in free-stall compared with those housed in tie-stall barns. Multivariate linear regression models of 3 reproductive performance measures indicated that cows with ovarian cysts and/or increased peak milk production had significantly longer calving-to-first estrus and calving-to-conception intervals as well as lower conception rates than average producing cows without cysts. Cows with metritis were found to have significantly shorter calving-to-conception intervals but no detectable difference in conception rate or calving-to-first estrus interval than their herdmates. As lactation number increased reproductive performance improved. Cows that were observed in estrus earlier conceived earlier. Animals receiving uterine infusions had significantly longer calving-to-conception intervals and lower conception rates than their herdmates. There was no detectable difference in reproductive performance for cows treated with GnRH or PG compared with the nontreated cows. An increased estrus detection rate was associated with shorter calving-to-conception intervals and lower conception rates. Based on the range of performance in the study herds, the factors with the greatest potential influence on calving-to-conception interval in the average herd were the estrus detection rate and conception rate.

Animals↗

PubMed1987

Economic evaluation of fourteen methods of estrous detection.

Costs of 14 methods to detect estrus were compared under simulated commercial dairy situations using artificial insemination. Alternative methods were twice or thrice daily visual observation and factorial combinations with various estrous detection aids [teaser bull, heat mount detector, and tail paint (also in combination with visual observation only during routine chores), estrous synchronization by prostaglandin F2 alpha, estrous synchronization plus heat mount detector]. A sensitivity analysis was used to compare tail paint and heat mount detector methods. Total costs for labor and other inputs were estimated for alternative 120-cow dairy herds with cumulative conception rate greater than or equal to 90% by considering five labor wage rates, four first-service conception rates, and three detection rates for each estrous detection method. Heat mount detector and tail paint methods with visual observation only during routine dairy chores always had lowest cost when average wage rate exceeded @2.25/h. To make heat mount detectors competitive, corresponding detection rate would have to be at least 10% higher than for the tail paint method. Unaided visual observation with two checks/d was less expensive than heat mount detector methods when labor had few alternative demands and cost less than $2.25/h. These methods were generally less than half as costly as teaser bull and prostaglandin alternatives.

Animal Husbandry↗

PubMed1985

Fertility trial in Zebu cattle after a natural or controlled estrus with prostaglandin F2 Alpha, comparing natural mating with artificial insemination.

With the object of comparing reproductive efficiency obtained by natural mating and by artificial insemination (AI), not only following a natural estrus but also after an induced estrus with PGF2Alpha in Zebu cattle in the tropics, 244 adult cows were divided into 4 groups. Group I (N = 69) and Group III (n = 62) were injected with 25 mg of PGF2Alpha when a functional CL was found on rectal examination. Group I was inseminated and group III was served by natural mating, both groups within five days after injection. Groups II (n = 57) and IV (n = 56) were left untreated, group II being AI and group IV ran with a fertile bull for 22 days. Estrus detection was carried out only in the injected groups (I and III) for 15 minutes every three hours between 0600 and 1800. All information was analyzed by linear trigonometric models. The onset of estrus occurred on average 68.7 h after injection in group I and 59.5 h in group III. However only 46.3% and 54.8% of animals were detected in estrus in group I and III respectively, the difference being significant (P < 0.10). Conception rates were 18.6%, 29.8%, 19.3% and 33.9% for groups I, II, III, and IV respectively. A significant difference (P < 0.10) existed between the injected groups and the untreated ones.

Journal Article↗

PubMed2000

Milk progesterone profiles in various reproductive states in dairy buffaloes under field conditions.

Fifty-one dairy buffaloes in the last two months of gestation were selected at seven private peri-urban farms in the Peshawar district. Observations were recorded in buffaloes during normal (NBS, August to January) and low breeding seasons (LBS, February to July). After parturition, rectal examination of reproductive organs was carried out. Estrus detection was made through visual observation and the use of intact bull. Postpartum ovulation was confirmed by ovarian palpation per rectum and milk progesterone levels (MPL), determined through radio-immunoassay. MPL was higher (p < 0.01) at various intervals in NBS calves (1.97 +/- 0.30 ng/ml) as compared to LBS calves (0.68 +/- 0.08 ng/ml). During LBS, MPL remained < 0.30 ng/ml up to the third fortnight and started rising later, reaching a peak of 1.27 ng/ml during the sixth fortnight. During NBS, there was a sharp rise in MPL during the second fortnight, reaching 3.64 ng/ml during the sixth fortnight. MPL was significantly different on different experimental farms (p < 0.01). MPL reached the lowest levels on the day of estrus (0.10 ng/ml), reached it's peak on day 7 and started declining on day 17 of estrus. MPL showed two postpartum elevations. In true anestrus buffaloes, MPL remained consistently low. However, in the anestrus period, silent ovulations were also noted, as reflected by increasing MPL without estrus signs. In pregnant buffaloes, MPL remained > 1 ng/ml. Results of the study showed that the low postpartum reproductive performance in dairy buffaloes during LBS was primarily due to inadequate functioning of the corpus luteum in secreting optimum concentrations of progesterone. The higher incidence of silent estrus during LBS indicated improved management for the detection of estrus.

Anestrus↗

PubMed1990

Influence of gonadotropin-releasing hormone and timing of insemination relative to estrus on pregnancy rates of dairy cattle at first service.

The objective was to determine the influence of gonadotropin-releasing hormone on pregnancy rates of dairy cattle at first services, when both the timing of hormone injection and insemination were altered relative to the onset of estrus. Cows (n = 325) were assigned randomly to six groups making up a 2 X 2 X 2 incomplete factorial experiment; dose of GnRH (100 micrograms versus saline), timing [1 h (early) or 12 to 16 h (late) after first detected estrus] of AI, and timing of hormone injection (early versus late) were the three main effects. Cows were observed for estrus 4 times daily. Treatments and resulting pregnancy rates were: 1) hormone injection early plus AI early (35%), 2) hormone injection late plus AI early (34%), 3) saline injection early plus AI early (30%), 4) hormone injection late plus AI late (30%), 5) hormone injection early plus AI late (46%), and 6) saline injection late plus AI late (43%). Pregnancy rate in the first four groups (32%) was less than that in the latter two groups (44%). Concentrations of LH in serum were greater for cows given hormone or saline injections in early estrus than for cows injected with either hormone of saline during late estrus. Concentrations of LH in serum 2 h after GnRH were elevated above those of controls, whether GnRH was injected during early or late estrus. Neither concentrations of LH during estrus nor concentrations of progesterone 8 to 14 d after estrus explained the possible antifertility effect of GnRH given during late estrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

Effect of grazing and fat supplementation on production and reproduction of Holstein cows.

The objective of this trial was to investigate the effects of feeding a soybean oil refining by-product (SORB), made up mainly of sodium salts of long-chain fatty acids, on reproductive performance and productivity of 36 early lactation Holstein cows managed in a free-stall barn or on annual rye-ryegrass pasture. In this 2 x 2 factorial arrangement of treatments, cows consumed 0 or 0.5 kg/d of SORB as part of a total mixed ration for barn cows or as part of a grain supplement fed to cows on intensively, rotationally stocked pasture. Blood was sampled 3 times weekly and plasma was measured for progesterone to assess ovarian activity. Estrus activity was recorded using the HeatWatch estrus detection system. Although average 14-wk milk production (37.2 kg/d) was not different among treatments, barn cows had more persistent lactations than did grazing cows. Cows housed in the barn lost less body weight and returned to initial body weight sooner and had lower mean concentrations of plasma nonesterified fatty acids (464 vs. 261 mEq/L) than those managed on pasture. The milk fat of cows on pasture contained greater proportions of conjugated linoleic acid and linolenic acid but a corresponding 0.22 percentage unit decrease in milk fat concentration (3.39 vs. 3.16%). Cows managed on pasture had greater peak concentrations of plasma progesterone during the first estrous cycle. Cows managed on pasture and fed SORB had the greatest accumulation of plasma progesterone over the 14 wk of the study (SORB x housing interaction). These cows experienced the most mounts during their first estrus (9.3) and pregnancy rate was also greatest for this treatment (62.5%). Feeding SORB did not affect production of milk, fat, or protein. Loss of body condition was less in cows fed SORB. Ruminal fluid concentration of propionate increased and ruminal pH decreased in cows fed SORB. A lower proportion of fatty acids less than 18 carbons in length was found in the milk fat of cows fed SORB, thus indicating lower de novo synthesis of fatty acids. Higher proportions of C18:2n-6 and conjugated C18:2 were found in the milk fat of cows fed SORB. Based on concentrations of plasma progesterone, cows fed SORB experienced their first ovulation earlier (26.7 vs. 42.4 d postpartum) than did cows not supplemented with SORB. Neither housing system nor SORB supplementation influenced detection of first estrus (50.5 d) or the mean length of each estrus period (447 min).

Animals↗

PubMed2005

Resynchronization of ovulation and timed insemination in lactating dairy cows, II: assigning protocols according to stages of the estrous cycle, or presence of ovarian cysts or anestrus.

Pregnancy rates were compared in lactating dairy cows (n = 1083) assigned to protocols for resynchronization of ovulation based on stages of the estrous cycle, or presence of ovarian cysts or anestrus. Cows were detected not pregnant by ultrasonography 30 d after a previous AI (study day 0) and classified as diestrus, metestrus, proestrus, with ovarian cysts or anestrus. Cows in diestrus (January-May) were assigned to either Ovsynch (GnRH day 0, PGF2alpha day 7, GnRH day 9, and timed-AI [TAI] 16 h later; n = 96), or Quicksynch (PGF2alpha day 0, estradiol cypionate [ECP] day 1, AI at detected estrus [AIDE] on day 2, or TAI on day 3; n = 96). Cows in diestrus (June-December) were assigned to either Ovsynch (n = 156) or Modified Quicksynch (PGF2alpha day 0, ECP day 1, AIDE days 2 and 3, and to Ovsynch on day 4 if not detected in estrus; n = 142). Cows in metestrus were assigned either to Ovsynch (n = 68), Heatsynch (GnRH day 0, PGF2alpha day 7, ECP day 8, AIDE day 9, or TAI day 10; n = 62), or GnRH + Ovsynch (GnRH on day 0, followed by Ovsynch on day 8; n = 64). Cows in proestrus, with ovarian cysts, or anestrus were assigned to either Ovsynch (proestrus n = 89, ovarian cysts n = 97, anestrus n = 8) or GnRH + Ovsynch (proestrus n = 87, ovarian cysts n = 109, anestrus n = 9). Pregnancy rate was evaluated 30, 55 and 90 d after resynchronized AI. For cows in diestrus (January-May), pregnancy rates were higher for Ovsynch (35.9, 29.2 and 26.0%) than for Quicksynch (21.7, 16.7 and 15.6%). For cows in diestrus (June-December), pregnancy rates were similar for Ovsynch (34.4, 24.0 and 23.6%) and Modified Quicksynch (27.1, 26.2 and 21.6%). For cows in metestrus, pregnancy rates were higher for GnRH + Ovsynch (33.3, 24.5 and 20.3%) than for Heatsynch (20.3, 12.9 and 9.8%). For cows with ovarian cysts, pregnancy rates were higher for GnRH + Ovsynch (30.3, 26.6 and 22.9%) than for Ovsynch (20.2, 18.5 and 14.7%). Assignment to resynchronization protocols based on the stages of the estrous cycle, or presence of ovarian cysts improved pregnancy rates.

Anestrus↗

PubMed1988

Ovine estrus synchronization and superovulation using norgestomet B and follicle stimulating hormone-pituitary.

Finewooled Rambouillet range ewes were used in a study to determine the feasibility of using a progesterone ear implant to synchronize estrus. In addition, some of the ewes were further treated with injections of follicle stimulating hormone-pituitary (FSH-P) to induce superovulation. Five days following estrus detection and breeding, FSH-P-treated ewes were laparotomized and surgically flushed to recover embryos. The number of corpora lutea (CL), the total number of embryos and the number of transferable embryos recovered were recorded along with the number and size of follicles present on both ovaries. Ewes synchronized as recipients were laparotomized for surgical transfer of embryos 5 d following estrus. The number of CL and follicles were recorded. Response to superovulation by FSH-P did not differ (P>0.05) between age groups of ewes when the number of CL present was counted. However, the total number of embryos flushed and good embryos was lower (P<0.05) among the oldest (7 yr) ewes. The number of follicles present showed little variation between age groups. Recipient ewes (No FSH-P) were similar in the number of CL with 6-yr-old ewes, having fewer (P>0.05) CL, than 3-, 4- or 7-yr-old ewes. Only slight variation was boserved in the number of follicles in recipient ewes. Among donor ewes receiving FSH-P in addition to Synchro-Mate B, 71% were detected in estrus within 48 h of implant removal vs 55% of the recipients.

Journal Article↗

PubMed1999

Influence of equine chorionic gonadotropin on weaning-to-estrus interval and estrus duration in early-weaned, primiparous, female swine.

The weaning-to-estrus interval (WEI) influences the total nonproductive days (NPD) accumulated by the breeding herd and affects herd productivity. Short lactation lengths (LL) are commonly followed by prolonged WEI, which are also associated with short estrus duration (ED). Equine chorionic gonadotropin treatment is a tool that has been used to reduce WEI, especially for low-parity females. The objectives for this study were to evaluate the effect of LL on the association between WEI and ED and to estimate the effects of postweaning eCG administration on WEI and ED for early-weaned females. Two treatments (TREAT) consisting of 750 IU of eCG (n = 96) or control (n = 77) were applied 1 d after weaning to first-parity, weaned females. The study was conducted on a commercial farm having a target LL of 18 d. Estrus detection was conducted three times daily, and estrus duration was determined as the interval between the first and the last positive response to back pressure. Analyses of variance were conducted to estimate the effects of LL and TREAT on WEI and the effects of TREAT and WEI on estrus duration. Mean LL was 17.9+/-1.7 d, mean WEI was 106.6+/-29.2 h, and mean estrus duration was 55.9+/-15.5 h. Even though the frequency of short WEI tended to increase with longer LL, mean WEI was shortest for females weaned after 18 d and longest for those weaned after 20 d (P<.05). The WEI for females receiving eCG (98.7+/-2.7 h) was shorter (P = .0001) than that for control females (121.5+/-3.3 h). The WEI was also affected by a LL x TREAT interaction (P = .0014), indicating that the interval was longer (P<.05) for control females weaned after 17 and 20+ d than for other females. The LL and TREAT did not affect estrus duration (P = .20 and P = .157, respectively). However, estrus duration was reduced as the WEI increased (P = .0001), and it was also influenced by a WEI x TREAT interaction (P = .024). A linear regression model estimated that the association between WEI and estrus duration was stronger in the eCG group than in the control group (R2 = .51 and .15, respectively; both P<.001). In conclusion, the use of eCG postweaning was associated with more precise prediction of estrus duration as a function of the WEI and allows optimization of breeding management in early-weaned, primiparous females.

Animals↗

PubMed1985

Management factors affecting reproductive performance of dairy cows in the northeastern United States.

Dairy herds (476) in seven states in the northeastern United States were surveyed to determine effects of various management factors on reproductive performance. Error of estrus detection (greater than 1 ng/ml of milk progesterone) on the day of service was 5.1% for 4558 cows but was as high as 60% in some herds. Error was not affected by herd size but was greater in freestall (6.8%) than in conventional (5.2%) housing. "Standing" and "riding other cows" were the most accurate signs of estrus. Of cows in or near estrus when serviced, 28.1% were open 3 wk later, 12.9% were probably open, and 59% were probably pregnant based on analysis of milk progesterone. Conception rate, not affected by herd size or housing type, was greater for cows in estrus during the morning and serviced the same afternoon (52.2%) than for cows observed in the afternoon and serviced the next morning (47.1%). Fifty-five percent of cows open to first service were serviced again within 3 days of expected return to estrus. Days to first service and conception rates were correlated positively. Milk progesterone concentration 21 to 24 days after service predicted a cow will calve with 88.6% accuracy and that she will not with 93.9% accuracy. Veterinarians predicted a calf with 92.5% accuracy by rectal palpation.

Animal Husbandry↗

PubMed2000

The effect of time of artificial insemination on fertilization status and embryo quality in superovulated cows.

Thirty nonlactating Holstein cows were superovulated to determine the effect of artificial insemination time on fertilization status and embryo quality. During the luteal phase of the estrous cycle, cows were administered 38 mg FSH-P in a 4-d descending dose regimen. Luteolysis was induced with two injections of prostaglandin on the last day of FSH-P treatment. All cows were continuously monitored for behavioral estrus using the HeatWatch estrus detection system. All cows were inseminated once with one .5-mL straw (50 x 10(6) sperm) at either 0 (n = 10), 12 (n = 10), or 24 h (n = 10) after the first standing event. The elapsed time (mean +/- SD) from the first prostaglandin dose to the first standing event was 39.4 h +/- 7.7 h. The (mean +/- SD) duration of behavioral estrus was 13.2 h +/- 4.1 h. The (mean +/- SD) number of standing events was 27 +/- 17. Five hundred twenty-nine embryos and ova were recovered nonsurgically 6 d after insemination. Fertilization rates were 29 (0 h), 60 (12 h), and 81% (24 h) (P < .01). Percentages of excellent and good, fair and poor, and degenerate embryos were not different (P > .05). Percentages of embryos with accessory sperm were 5 (0 h), 8 (12 h), and 41 (24 h) and differed between the 0 and 24 h and the 12 and 24 h inseminations (P < .01). Artificial insemination of superovulated, nonlactating Holstein cattle 24 h after onset of estrus increased fertilization rate and percentage of embryos with accessory sperm compared with insemination at 0 or 12 h after onset of estrus. Embryo quality was not affected by time of insemination.

Animals↗

PubMed2004

Effect of housing system and boar exposure on estrus expression in weaned sows.

Reproductive efficiency depends on detection of estrus, which may be influenced by housing and boar exposure. This experiment investigated the effects of housing system and boar contact on measures of estrus in weaned sows. Mixed-parity sows were randomly assigned to be weaned into gestation crates away from boars (AWC, n = 45), into pens away from boars (AWP, n = 42), or into pens adjacent to a mature boar (ADJ, n = 46). Estrus detection was initiated at approximately 0700 (0 h) and again at 0.25-, 0.5-, 1-, 2-, 4-, and 8-h intervals beginning on d 4 and continuing through d 7 following weaning. Estrus detection involved observation of the standing response after application of nose-to-nose boar exposure, backpressure, and side rubbing. For the AWC sows, a mature boar was moved to the front of the crates for a 10-min period and then removed. Sows housed in AWP were moved approximately 15 m to an empty pen adjacent to a mature boar for a 10-min period, and then returned to their pen. Sows housed ADJ were not moved and estrus detection was performed in their home pen for a 10-min period. The proportion of sows expressing estrus within 7 d from weaning was lowest for ADJ (80%, 37/46) compared with AWP (98%, 41/42) and AWC (96%, 43/45; P < 0.05). There was an effect of interval from weaning to estrus on the percentage of sows expressing estrus, but there was no interaction with treatment. Sows in AWC and AWP (4.7 d) had decreased (P = 0.01) intervals from weaning to estrus compared with ADJ (5.2 d). The duration of estrus was also shorter (P < 0.001) for ADJ (45 h) compared with AWC (58 h) or AWP (62 h). There was a treatment x interval x day of estrus effect for the percentage of sows expressing estrus. After detection of the first standing response on the first day of estrus, only 62 to 82% of sows were detected standing over the next 2 h for all treatments. However, at 4 to 8 h, this increased to 85 to 98% for the AWC and AWP sows, but <73% of the ADJ sows were detected during this period. On the second day of estrus, estrus expression was not influenced by interval for the AWC and AWP sows and was between 90 to 100% during the 8-h period, whereas ADJ sow detection rates were between 68 to 88%. These data suggest that housing sows adjacent to boars negatively affects estrus expression and detection. In addition, refractory behavior occurs in approximately 30 to 40% of sows and is influenced by housing relative to the boar, day of estrus, and interval from last boar exposure.

Animals↗

PubMed1997

Effect of ruminant grade Menhaden fish meal on reproductive and productive performance of lactating dairy cows.

Menhaden fish meal, fed at 0.7 kg/d [2.7% of dietary dry matter (DM)], replaced blood meal and meat and bone meal (2.0% of dietary DM) in the diet fed at dairy A (n = 341) and replaced blood, meat and bone, and corn gluten meals (3.2% of dietary DM) in the diet fed at dairy B (n = 300). Cows consumed the experimental total mixed diets from approximately 24 to 109 d postpartum. Cows were synchronized for estrus using injections of GnRH agonist at 51 d postpartum. PGF2 alpha 7 d later, and artificial insemination at detected estrus. Resynchronization occurred using the same program if estrus was not detected. Diet failed to alter reproductive responses at synchronized artificial insemination. Pregnancy rate at 120 d postpartum was not altered by diet at dairy A (65.4% vs. 60.2%) but was improved by dietary fish meal at dairy B (31.9% vs. 41.3%; interaction of dairy and diet). The dynamics of corpus luteum regression were altered in cows fed fish meal at dairy B. Dietary fish meal did not influence milk production of cows at dairy A but increased production of milk (2.3 kg/d) and protein (0.1 kg/d) of second parity cows at dairy B. When dietary fish meal was fed to cows at dairy B, production of milk fat and 4% FCM was higher for cows in parity 5 or greater than that for cows in fourth parity.

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