Effects of work and diet on progesterone secretion, short luteal phases and ovulations without estrus in postpartum F1 crossbred dairy cows

The effects of work and diet supplementation on progesterone secretion and on incidence of short luteal phases and ovulations without estrus was investigated in 40 postpartum F(1) crossbred dairy cows. These cows were allocated to 1 of 4 treatment groups: Group SPNW, supplement-nonworking; Group SPW, supplement-working; Group NSNW, nonsupplement-nonworking; and Group NSW, nonsupplement-working. After calving, working cows pulled sledges with a load of 300 to 450 Newtons(N); 4 hours per day 4 days per week, for a total of 100 days over a 1-year period. All cows were fed natural grass hay ad libitum while the supplemented cows were fed 3 kg of concentrate per head per day. The proportion of cows which showed behavioral estrus by 1 year post partum was 100, 100, 60 and 20% for Group SPNW, SPW, NSNW and NSW cows, respectively. Based on plasma progesterone concentrations, ovulation started 62 days earlier than onset of behavioral estrus. A total of 73 ovulations occurred by 1 year post partum. Forty-nine (67.1%) and 26 (32.9%) ovulations occurred in the supplemented and nonsupplemented cows while 33 (45.2%) and 40 (54.8%) ovulations occurred in the working and nonworking cows, respectively. Of the total ovulations, 26 (35.6%) were not associated with behavioral signs of estrus and occurred in 13 (32.5%) cows. The incidence of ovulation without estrus was higher (P<0.05) in working (42.4%) than in nonworking (30%) cows and in nonsupplemented (41.7%) than in supplemented (32.7%) cows. Short luteal phases occurred in 32.5% of the cows before the establishment of normal estrous cycles. In working cows, diet supplementation off-set the negative effect of work on the onset of estrus and conception. However, a relatively higher number of cows in Group SPW had ovulations without estrus before a normal estrous cycle was established. The incidence of short luteal phases or ovulations without estrus did not influence the pregnancy rate in subsequent normal estrus periods. In conclusion, in the supplemented cows, work did not influence the proportion of cows showing estrus and conceiving, but it significantly delayed the postpartum anestrus interval. In the nonsupplemented cows, reproductive activity was impaired in both working and nonworking cows, but was pronounced in working cows. However, once pregnancy was established there was no effect of work on the maintenance of pregnancy. Our study shows that with appropriate feeding regimens lactating crossbred cows could be used for draught purposes without any detrimental effects on fertility, but calving intervals would be extended. Finally, the physiological mechanisms involved in anestrus and ovulations without estrus and the significance of such phenomena in affecting postpartum reproductive performance and fertility in working cows require further investigation.     

Inflammatory cytokine concentrations in uterine flush and serum samples from dairy cows with clinical or subclinical endometritis

The objective of this study was to compare the concentrations of inflammatory cytokines in uterine flush and serum from healthy postpartum dairy cows and cows with clinical or subclinical endometritis. Clinical endometritis was diagnosed by observation of vaginal discharges (>50% pus) and subclinical endometritis was diagnosed by evaluation of uterine cytology (neutrophils >18%) at 4 weeks postpartum. Uterine flush was obtained from 48 cows at 4, 6, and 8 weeks postpartum for evaluation of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, IL-8, and IL-10 concentrations. Serum samples were obtained from 34 cows just after calving and at 1, 2, 4, 6, and 8 weeks postpartum for evaluation of TNF-α, IL-1β, and IL-6 concentrations. Concentrations of TNF-α, IL-6, and IL-10 were greater (P < 0.05) in cows with clinical endometritis than in cows with subclinical endometritis and healthy controls, whereas concentrations of IL-8 in both cows with clinical and subclinical endometritis were greater (P < 0.005) than in controls. Overall, IL-6 and IL-10 concentrations decreased during the postpartum period. IL-1β concentrations in cows with clinical endometritis decreased (P < 0.0005) during the postpartum, whereas concentrations in cows with subclinical endometritis and controls did not change significantly with time; at 4 weeks postpartum, concentrations were greater (P < 0.0001) in cows with clinical endometritis. There were no significant effects of group, sampling time, or interaction on serum cytokine concentrations. In conclusion, cows with endometritis have greater inflammatory cytokine concentrations in uterine flush than healthy cows, but no differences were observed in serum.     

Reproductive function in beef cows calving in the spring or fall

Plasma progesterone was determined twice weekly for approximately 100 days postpartum in suckled purebred (Hereford) and crossbred (beef x dairy) cows that calved in the spring or late summer/fall season. The progestèrone profiles and occurrence of estrus were used to determine ovulation times and to monitor ovarian function. Postpartum ovulations occurred significantly earlier in crossbred than in purebred cows (38.1 ± 18.5 vs. 58.1 ± 21.8, P<0.01) and in fall compared to spring calving cows (32 ± 13.9 vs. 59.1 ± 20.3, P<0.001). Rations providing either 70 or 100% of requirements for metabolizable energy were fed from 30 days prepartum until the end of the subsequent rebreeding period. Cows receiving the 70% energy ration ovulated slightly earlier but there was no effect of ration on days to pregnancy. The minimal effect of energy ration was not unexpected in this trial since many of the cows were overconditioned during late gestation.The correlation between calendar date of calving and interval to first ovulation was significant for spring (r = ?0.38, P<0.01) but not for fall calving animals. Since cows were confined and received a balanced ration of stored feeds throughout the year, photoperiod and/or temperature rather than nutritional factors would be the probable cause of delayed ovarian activity in spring calvers.Reproductive performance was assessed during the period when samples were collected and the response for purebred (n=105) and crossbreds (n=142), respectively were: ovulated by day 60 postpartum, 57 vs. 87%; mated by day 100 without conception, 17 vs. 26%; ovulated before day 100 without detection and mating, 10 vs. 4%; anovulatory to day 100, 7 vs. 0%; pregnant by day 100, 67 vs. 70%. Similar comparisons for spring (n=133) and summer/fall (n=144) calvers, respectively, were: ovulated by 60 days postpartum, 56 vs. 96%; mated by day 100 without conception, 27 vs. 17%; ovulated by day 100 without detection and mating, 8 vs. 5%; anovulatory to day 100, 5 vs. 0%; pregnant by day 100, 60 vs. 78%. The difference with the greatest practical significance is that a higher proportion of the late summer/fall calving animals were pregnant by day 100 postpartum (P<0.01) which indicates that reproductive performance is superior in fall calving beef cows.     

Effects of dietary supplementation of pioglitazone on metabolism,milk yield,and reproductive performance in transition dairy cows

The objective of this study was to investigate the effect of dietary supplementation of pioglitazone (PGT), a specific ligand for PPARγ, on metabolic dynamics, milk production, and reproductive performance of transition dairy cows. Eighty multiparous Holstein cows in their second or more lactations were blocked by the calving date and parity and assigned randomly to four dietary groups (n = 20 cow/treatment) including control (no PGT−/−), supplemented with PGT (6-mg PGT/kg body weight) from Day −14 to +21 relative to parturition (PGT+/+) or only during prepartum (PGT+/−) or postpartum periods (PGT−/+). Postpartum body condition score and body weight loss decreased (P < 0.05) in all PGT-supplemented groups. Milk yield was not affected by PGT supplementation (P > 0.05). Percentage of milk fat decreased (P < 0.05) in all PGT-treated groups; however, milk fat yield was lower (P < 0.05) in PGT (+/+) and PGT (+/−) groups compared with PGT (−/−). Peripartum (Day −7 to +7) concentrations of plasma nonesterified fatty acids and β-Hydroxybutyrate decreased in PGT (+/+) but not in the PGT (−/−) group (P < 0.05). During the postpartum period, PGT reduced (P > 0.05) plasma concentrations of nonesterified fatty acids in all PGT-treated groups but did not affect β-Hydroxybutyrate level. Plasma concentrations of triglycerides decreased in all PGT-supplemented groups. Supplementation of PGT increased the peripartum concentrations of plasma glucose in PGT (+/+) and PGT (+/−) groups compared with control. Plasma concentrations of insulin-like growth factor 1 were higher in PGT (+/+) compared with the control group during both the peripartum and postpartum periods. Plasma concentrations of growth hormone and insulin were not affected by PGT treatment (P > 0.05). Mean days to ovulation were lower in PGT (+/+) and PGT (-/+), and the proportion of cows ovulating by Day 14 postpartum was higher in PGT (+/+) compared with control. Days open were shorter in PGT (+/+), PGT (+/−), and PGT (−/+) groups compared with control. However, the proportion of pregnant cows at 120 days in milk were higher in all PGT-supplemented groups. The results showed positive effects of dietary supplementation of PGT, especially supplementation during both the prepartum and postpartum periods, on metabolic dynamics, ovarian function, and reproductive performance in transition dairy cows.     

Silent ovulation, based on walking activity and milk progesterone concentrations, in Holstein cows housed in a free-stall barn

The objectives of the current study were to determine the incidence of silent ovulation (based on walking activity and milk progesterone profiles), identify risk factors for silent ovulation, and investigate its impact on reproductive performance in high-yielding dairy cows in free-stall housing. Overall, 277 lactations in 161 Holstein Friesian cows from a commercial dairy herd in northern Japan were studied. Walking activity (measured with pedometers) >80% above the mean for the preceding 2 d was defined as estrus, whereas day of ovulation was estimated using milk progesterone concentrations. Ovulation not preceded by increased walking activity was considered silent ovulation; the incidence was 55.2%, 23.8%, 21.3%, and 10.5% at the first, second, third, and fourth ovulations postpartum, respectively. Moderate and high milk yield significantly increased the risk of silent ovulation at second (odds ratio [OR] = 2.7 and 1.2; P = 0.04) and third and/or fourth ovulations (OR = 6.7 and 12.9; P = 0.03). Based on survival analysis, silent ovulations at the first, second, third, and/or fourth ovulations were associated with 28% (hazard ratio [HR] = 0.72), 55% (HR = 0.45), and 47% (HR = 0.53) reductions in pregnancy rate, respectively, and 41% (HR = 0.59), 66% (HR = 0.34), and 65% (HR = 0.35) reductions in artificial insemination (AI) submission rate. Cows with at least one silent ovulation (with the exception of the first ovulation) had a longer interval from calving to first AI (72 vs. 54 d, P < 0.001) and to achievement of pregnancy (133 vs. 80 d, P < 0.001). In conclusion, approximately one third of the ovulations (based on milk progesterone concentrations) in Holstein cows within 90 d postpartum were silent. Silent ovulations at the second to fourth ovulations were associated with high milk yields and at all ovulations were associated with impaired reproductive performance.     

Postpartum ovarian activity in dairy cows: Correlation between behavioral estrus, pedometer measurements and ovulations

The efficacy of pedometers as estrus detection aids was tested in a group of 47 Holstein cows during the postpartum period. Pedometers were strapped on the left front leg of each cow on the day of parturition and pedometer measurements were recorded twice daily for 60 days. The cows were also observed twice a day for behavioral signs of estrus. Daily blood samples were collected during Days 1-30, and thereafter once every two days from Days 30-60 after parturition for progesterone assay. Rectal palpations of the ovaries were carried out once every four days during the first month after parturition. Based on the progesterone profiles and rectal palpation findings, 91 ovulations were recorded in 42 cows and 5 cows remained acyclic during the observation period. Seventy-six percent (69 91 ) of the ovulations were associated with pedometer indications of estrus, while only 35% (32 91 ) of the ovulations were associated with observed estrus. Fifty-seven percent (24 42 ) of the first postpartum ovulations were associated with pedometer measurements, but only 19% (8 42 ) of the first postpartum ovulations were associated with behavioral signs of estrus. Similarly, pedometers were superior to observations as a method of detection of estrus associated with the second and third postpartum ovulations (91% vs 37%, 92% vs 78% respectively). It is concluded that pedometers are useful aids for estrus detection, particularly in the immediate postpartum.     

Effect of early postpartum PGF2α treatment on reproductive performance in dairy cows with calving and puerperal traits

The objective of this study was to evaluate the effects of early postpartum PGF two alpha treatment on reproductive performance in dairy cows with calving and puerperal traits. A total of 363 Holstein cows (128 primiparous and 235 multiparous) were selected based on the presence of at least one of calving and puerperal traits (dystocia, retained placenta, twin, abortion, and postpartum uterine infections) and were assigned to two groups (treatment and control) irrespective of presence or absence of luteal tissue. Cows in the treatment group were treated twice with 25 mg dinoprost 8 h apart on day 20 postpartum, and for the control group saline placebo was administered. As it was speculated that the timing of a second dose would mimic the release of endogenous PGF2α from the uterus, our hypothesis was that two doses of PGF2α 8 h apart may increase the duration of elevated plasma prostaglandin F2α metabolite concentration in these cows. Recorded reproductive variables included days to first estrus, days to first AI, first service conception rate, pregnancy by 150 days in milk, service per conception, open days, and the percentage of repeat breeder animals. The data were analyzed using SPSS (Version 15) (IBM North America, New York, NY, USA) and Minitab (Version 14) (Minitab, State College, PA, USA). Although early postpartum PGF2α treatment had no effect on days to first estrus (36.7 days vs. 34.9 days, P = 0.056) and days to first AI (70.5 days vs. 72.2 days, P = 0.537), it increased first service conception rate (47.1% vs. 27.6%, P < 0.001); and this was more remarkable in primiparous cows (64.7% vs. 25%, P < 0.001). PGF2α treatment reduced the mean service per conception (1.92 vs. 2.72, P < 0.001) and the mean open days (112 days vs. 144 days, P < 0.001), and increased pregnancy by 150 days in milk (DIM) (80% vs. 66%, P = 0.004). The prevalence of repeat breeder syndrome in cows with calving and puerperal traits was reduced by PGF2α treatment (10% vs. 29.8%, P < 0.001). In conclusion, treatment of cows with calving and puerperal traits twice with a luteolytic dose of PGF2α 8 h apart on Day 20 postpartum improved reproductive performance and reduced the prevalence of repeat breeder syndrome.     

Effect of monensin and suckling on the GnRH induced luteinizing hormone surge and the effect of monensin on the postpartum interval in Brangus cows

Twenty-seven fall calving Brangus cows were randomly allotted to one of four treatment groups: nonsuckled monensin (NSM), suckled monensin (SM), nonsuckled control (NSC), and suckled control (SC). Cows were group fed 1.82 kg/hd/day concentrate and Coastal bermuda grass hay $\text{ad}$$\text{libitum}$. Monensin cows received 200 mg monensin/hd/day in the concentrate. At 0800 hr on day 21 postcalving, the calves were separated from the cows. Suckled monensin and SC cows were allowed to suckle their calves for 30 min at 6-hr intervals. Nonsuckled monensin and NSC cows were not suckled. Calves were given free access to the cows after 1400 hr on day 22 postpartum. At 0800 hr on day 22 postpartum, a blood sample was collected. A 100 μg GnRH challenge was administered IM at 0801 hr. Blood samples were collected at 15-min intervals for 6 hr postinjection. Changes in body weight and body condition from day 21 postpartum to the day of first estrus were not different (P>0.10) by dietary treatment. Monensin cows consumed 10.7% less hay than did the control cows. Serum luteinizing hormone (LH) following GnRH was greater (P<0.005) in suckled than nonsuckled cows. Control cows released more (P<0.005) LH in response to GnRH than did the monensin cows. The postpartum interval (to first estrus) for the monensin cows (92.4±14.7 days) was shorter (P<0.025) than the controls (138.5±9.5 days). A greater proportion (P<0.005) of the monensin cows (8 of 14) exhibited estrus by 90 days postpartum compared to the control cows (0 of 13). Monensin and suckling appear to exert independent and agonistic influences on pituitary function in the postpartum beef cow.     

Effect of postpartum suppression of ovulation on uterine involution in dairy cows

The objective of this study was to investigate the effect of time of first postpartum ovulation after calving on uterine involution in dairy cows with and without uterine puerperal disease. Transvaginal follicular puncture (FP) of follicles >6 mm suppressed ovulation and development of a CL until Day 42 after calving. Fifty-three lactating Holstein Friesian cows (3.4 ± 1.2 years old, parity 2.5 ± 1.0 [median ± mean absolute deviation]) were divided into groups on the basis of the presence (UD+) or absence (UD−) of uterine disease and whether FP was carried out (FP+) or not (FP−). Uterine disease was defined as the occurrence of retained fetal membranes and/or metritis. This resulted in the following groups: UD−FP− (n = 15), UD−FP+ (n = 13), UD+FP− (n = 13), and UD+FP+ (n = 12). A general examination, vaginoscopy, transrectal palpation, and transrectal B-mode sonography of the reproductive organs were conducted on Days 8, 11, 18, and 25 and then every 10 days until Day 65 after calving. After hormonal synchronization of ovulation (cloprostenol between Days 55 and 60 postpartum and GnRH 2 days later), cows were inseminated in the next spontaneous estrus. On average, the cows ovulated on Day 21.0 ± 6.0 (UD−FP−), 50.0 ± 4.0 (UD−FP+), 16.0 ± 3.0 (UD+FP−), and 48.0 ± 2.0 (UD+FP+) postpartum. Calving-to-conception interval and first-service conception rates were not affected by FP (P > 0.05). Healthy cows with FP had smaller (P < 0.05) uterine horn and cervical diameters assessed sonographically than cows without FP. FP reduced the prevalence of purulent vaginal discharge and uterine size assessed transrectally in UD+ cows (P < 0.05). The results showed that suppression of an early ovulation by transvaginal FP improved uterine involution in cows with and without uterine disease.     

Spontaneous recovery or persistence of postpartum endometritis and risk factors for its persistence in Holstein cows

It has been stated that postpartum endometritis in dairy cows has a tendency to cure without intervention. The objectives of this field study, therefore, were to determine the proportions of cows with spontaneous clinical recovery or persistence of postpartum endometritis and to determine some risk factors for its persistency in dairy cows (Bos taurus). Holstein-Friesian cows (n = 441 lactations) from seven dairy herds were examined monthly by vaginoscopy and transrectal palpation. A cow was considered to have “postpartum endometritis” if it had pus in the cervico-vaginal discharge at the first postpartum examination during Days 15 to 60 (Day 0 = day of calving); this was classified as mild, mucopurulent, or purulent endometritis, or endometritis with fluid in uterus. Furthermore, a cow with evidence of endometritis at least once during Days 61 to 150 was considered to have “persistence (or recurrence) of endometritis.” A total of 104 (23.6%) lactations had postpartum endometritis, of which 25.3% had persistence or recurrence of clinical endometritis. Cows with persistence or recurrence of endometritis became pregnant at a slower rate (hazard ratio [HR] = 0.28; P < 0.001) than those with no endometritis until Day 150. Calving in summer (odds ratio [OR] = 7.00; P = 0.04), early postpartum complications (OR = 6.58; P = 0.05), moderate (OR = 4.03; P = 0.08) and severe (OR = 30.99; P = 004) degrees of urovagina, and mucopurulent (OR = 9.54; P = 0.02) and purulent (OR = 5.70; P = 0.04) endometritis were risk factors for the persistence or recurrence of endometritis. Furthermore, 10.6% of cows that had not shown signs of postpartum endometritis had a new diagnosis of endometritis during Days 61 to 150. Some risk factors for the new diagnosis of endometritis beyond Day 60 were early postpartum complications (OR = 2.82; P = 0.03) and moderate (OR = 5.00; P = 0.001) or severe (OR = 12.63; P < 0.001) degrees of urovagina. In conclusion, approximately one quarter of cows with postpartum endometritis had persistence of endometritis until or beyond the breeding period. Risk factors for the persistence of clinical endometritis were summer calving, early postpartum complications, clinically relevant urovagina, and clinically relevant endometritis within 2 mo postpartum.     

Effect of PGF2α and GnRH on the reproductive performance of postpartum dairy cows subjected to synchronization of ovulation and timed artificial insemination during the warm or cold periods of the year

This study was designed to evaluate the reproductive performance of lactating dairy cows (Holstein Friesian) after the injection of PGF_2α analogue on Day 15 postpartum, and GnRH analogue on Day 23 after artificial insemination (AI) with Presynch (two injections of PGF_2α, administered 14 days apart starting at 30–35 days postpartum) + Ovsynch-based (GnRH–7 days–PGF_2α–2 days–GnRH–16–20 hours–timed artificial insemination) treatments, during the warm and cold periods of the year. All the cows (n = 313) were assigned to one of the four groups including: M₁ (n = 72) in which the cows were treated with PGF_2α on Day 15 postpartum + Presynch-Ovsynch + GnRH on Day 23 post-AI; M₂ (n = 41) in which the cows received PGF_2α on Day 15 postpartum + Presynch-Ovsynch; M₃ (n = 100) including the cows that got Presynch-Ovsynch; and control group (n = 100) including the cows that were not treated and were inseminated at natural estrus. Pregnancy diagnosis was performed 28 to 35 days post-insemination by means of ultrasound. The results showed that treatment with PGF_2α on Day 15 postpartum significantly decreased the days to conception and the number of services per conception (P < 0.01) and it also improved the first service conception rate (P < 0.1) only in cows that were treated with M₂ protocol. Whereas, the days to first service was not influenced by the treatment of PGF_2α on Day 15 postpartum (P > 0.05). In contrast, administration of GnRH on Day 23 post-AI increased the days to conception and the number of service per conception (P < 0.01) and tended to decrease the first service conception rate (P < 0.1) in cows that were treated with M₁ compared with M₂ protocol. Therefore, it was concluded that Presynch-Ovsynch protocol could be more reproductive and beneficial when a single treatment with PGF_2α was administered at 15 days postpartum (15 days after the PGF_2α, Presynch-Ovsynch protocol was initiated). Interestingly, the administration of a GnRH agonist on Day 23 post-AI not only did not improve the reproductive performance of the cows receiving first postpartum timed artificial insemination after Presynch-Ovsynch protocol but also reduced that.     

Impact of maternal heat stress at insemination on the subsequent reproductive performance of Holstein, Brown Swiss,and their crosses

Heat stress in hot environments is one of the major factors that can negatively affect milk production, reproduction, and the health of dairy cows. The aim of this study was to evaluate the impact of maternal heat stress at insemination on the subsequent reproductive performance of the pure Holstein (HO), Brown Swiss (BS), and their F₁ crossbred (BF) cows, under subtropical Egyptian conditions. The influence of temperature–humidity index (THI) on the pregnancy rate, fetal loss rate, calving traits, and reproductive indices were investigated. Fetal loss rate of pure HO was significantly increased from 17.1% at low THI to 24.9% at greater THI (odds ratio = 2.09; P = 0.032). Furthermore, abortion and stillbirth rates of pure HO were significantly increased from 3.6% and 3.8%, respectively, at low THI to 7.2% and 5.9%, respectively, at greater THI (odds ratio = 2.17 and 2.58; P = 0.037 and 0.031, respectively). In contrast, BS and BF cows can tolerate the heat stress, as there were no differences in the fetal loss, abortion, and calving difficulty rates at the different levels of THI. Pure HO cows had a significant longer calving interval and days open at high THI (449 and 173 days, respectively), compared with low THI (421 and 146 days, respectively). On the contrary, BS and BF cows had no difference in the calving interval at the different levels of THI. Our results indicate that pure BS and BF cows have a better adaptability and competent reproductive performance than pure HO under subtropical conditions.     

Reproductive performance of repeat breeders in dairy herds

The objectives were to characterize repeat breeding in dairy cows, including reproductive performance and risk factors. Data from 613 Holstein Friesian cows in nine dairy herds across Japan were enrolled. A repeat breeder was defined as a cow that did not become pregnant after three inseminations, despite no clinically detectable reproductive disorders. In contrast, cows that became pregnant within three inseminations were considered to have normal fertility. Of the 613 cows, 87.3% eventually became pregnant after repeated AI (maximum calving to conception interval was 435 d). Mean (±SEM) first AI conception rate, days in milk at first AI, calving to conception interval and service per conception were 38.3%, 82 ± 2 d, 125 ± 3 d, and 2.0 ± 0.1 times, respectively. Normal fertility cows (n = 479) required only 114 ± 3 d to conceive and 1.7 ± 0.1 inseminations per pregnancy, whereas repeat breeders (n = 86) required significantly more days to conceive (211 ± 10) and more inseminations per pregnancy (4.7 ± 0.2). Based on survival analysis, it took 94 d after calving for 50% of normal fertility cows to become pregnant, compared to 155 d for repeat breeders. For repeat breeders, 31.4, 50.0, and 58.1% became pregnant within 210, 300, and 435 d after calving, respectively. The risk factors for repeat breeding were parity (relative risk [RR] = 0.809; P = 0.058), resumption of postpartum ovarian cycles (RR = 1.928; P = 0.009), and days in milk at first AI (RR = 0.991; P = 0.039). In conclusion, repeat breeder dairy cows had very poor reproductive performance. Lower parity, abnormal resumption of postpartum ovarian cycles, and shorter days in milk at first AI were risk factors for repeat breeding.     

Control of estrus and ovulation in dairy cows

The efficiency of a synthetic prostaglandin analog (ICI 80996) for the control of the estrus cycle in dairy cows has been tested with and without simultaneous use of progestagen implants (SC 21009, Searle). Synchronization of estrus is closer after combined progestagen-prostaglandin treatments than after prostaglandins alone (78.7 % in estrus in 48h vs 60.2 % ; P<0.001).The percentage of cows not observed in estrus during the first 96h after the end of treatment was also lower after combined treatments (20.7 % vs 31.8 % ; P<0.05). The best estrus synchronization was obtained by injecting prostaglandin analog two days before implant removal (86 % in estrus in 48h and 14.0 % not observed in estrus within 96h).Fertility was studied in a field trial after one or two inseminations at a predetermined time for each treatment. A higher pregnancy rate was obtained with two inseminations after combined progestagen-prostaglandin treatment (49.1 %). This pregnancy rate differed significantly (P<0.05) from those obtained with one A.I. after the same treatment or two A.I. after the prostaglandin treatment but did not differ from the pregnancy rate obtained with one A.I. 80h after the second prostaglandin injection. The most important problem in dairy cows is the fall in pregnancy rate between 21 days and 6 months (19.7 to 35.1 % depending on treatment ; P<0.05).     

Effect of monensin on postpartum interval to first estrus and serum LH response to 0, 1, 2 or 4 mg estradiol-17β at 21 days postpartum

A 2×4 factorial design was used to evaluate the effects of monensin (0 vs 200 mg) and estradiol-17β (E2) dose (0, 1, 2 vs 4 mg) on postpartum interval (PPI) to first estrus and on serum LH release at 21 days postpartum. Forty-eight spring calving Brangus cows were randomly stratified by calving date and sex of calf into two feeding groups within 24 hr of calving. Each group received 2.7 kg/head/day of a milo:cottonseed meal (4:1) mixture containing either 0 or 200 mg monensin. Coastal bermuda grass hay and water were available $\text{ad}$$\text{libitum}$. During the period of E2 treatment and bi-hourly blood sampling, suckling was controlled at 6-hr intervals.Mean cow weight and body condition score within cell changed less than 23 kg and 0.5 points, respectively, from day 1 to day 21 postpartum and were unaffected by treatment (P>0.10). PPI was reduced (P<0.01) and proportion of cows exhibiting estrual behavior by 85 days postpartum was increased (P<0.05) by treatment with 200 mg monensin and unaffected by E2 dose. Monensin fed cows had a longer (P<0.05) interval to LH response (ILH) and to peak LH (ILHP) at the 4 mg E2 dose. Monensin had no effect (P>0.10) on LH variables at 0, 1 or 2 mg E2.     

Evaluation of infrared thermography combined with behavioral biometrics for estrus detection in naturally cycling dairy cows

Low estrus detection rates (>50%) are associated to extended calving intervals, low economic profit and reduced longevity in Holstein dairy cows. The objective of this study was to evaluate the accuracy of infrared thermography and behavioral biometrics combined as potential estrus alerts in naturally (not induced) cycling dairy cows housed in a tie-stall barn. Eighteen first lactation cows were subjected to transrectal ultrasonography to determine spontaneous ovulation. The dominant follicle (DF) disappearance was used retrospectively as an indirect indicator of ovulation, and to establish the estrus period (48–24 h prior the DF disappearance). Raw skin temperature (Raw IR) and residual skin temperature (Res IR) were recorded using an infrared camera at the Vulva area with the tail (Vtail), Vulva area without the tail (Vnotail), and Vulva’s external lips (Vlips) at AM and PM milking from Day 14 until two days after ovulation was confirmed. Behavioral biometrics were recorded on the same schedule as infrared scan. Behavioral biometrics included large hip movements (L-hip), small hip movements (S-hip), large tail movements and small tail movements to compare behavioral changes between estrus and nonestrus periods. Significant increases in Raw IR skin temperature were observed two days prior to ovulation (Vtail; 35.93 ± 0.27 °C, Vnotail; 35.59 ± 0.27 °C, and Vlips; 35.35 ± 0.27 °C) compared to d −5 (Proestrus; Vtail; 35.29 ± 0.27 °C, Vnotail; 34.93 ± 0.31 °C, and Vlips; 34.68 ± 0.27 °C). No significant changes were found for behavioral parameters with the exception of S-hip movements, which increased at two days before ovulation (d −2; 11.13 ± 1.44 Events/5min) compared to d −5 (7.30 ± 1.02 Events/5min). To evaluate the accuracy of thermal and behavioral biometrics, receiver operating characteristic curve analysis was performed using Youden index (YJ), diagnostic odds ratio, positive likelihood ratio (LR+), Sensitivity, Specificity and Positive predicted value to score the estrus alerts. The greatest accuracy achieved using thermal parameters was for Res IR Vtail PM (YJ = 0.34) and L-hip PM (YJ = 0.27) for behavioral biometrics. Combining thermal and behavioral parameters did not improve the YJ index score but reduced the false-positive occurrence observed by increasing the diagnostic odds ratio (26.62), LR+ (12.47), Specificity (0.97) and positive predicted value (0.90) in a Res IR Vtail PM, S-hip AM, S-hip PM combination. The combination of thermal and behavioral parameters increased the accuracy of estrus detection compared to either thermal or behavioral biometrics, independently in naturally cycling cows during milking.     

Effect of Organic Zinc,Manganese, Copper,and Selenium Chelates on Colostrum Production and Reproductive and Lameness Indices in Adequately Supplemented Holstein Cows

The current study aimed to investigate if different sources of supplemental zinc (Zn), manganese (Mn), copper (Cu), and selenium (Se) fed to dry and lactating dairy cows affect reproductive performance, lameness status, and colostrum production. The experiment was carried out on 60 multiparous non-lactating Holstein cows in a commercial dairy herd. The cows received randomly mineral mixtures in three treatment groups containing inorganic, 25% organic–75% inorganic, or 50% organic–50% inorganic forms of Zn, Mn, Cu, and Se starting from approximately 3 weeks prior to calving up to 90 days postpartum. Supplements were included in rations and fed twice a day. Reproductive parameters including days to first service, days to first estrus, service per conception, and conception rate were investigated. After parturition, colostrum production, composition, and immunoglobulin G₁ concentration were determined. Lameness, as an indicator of trace minerals deficiency, was evaluated in a five-score scale. The source of mineral supplement only numerically improved the assessed parameters excluding colostrum fat, protein, and ash percent. The organic form of supplements did not significantly affect reproductive performance, lameness score, or colostrum production.     

Prophylactic effect of a progestin (Chlormadinone acetate = CAP) on fertility of dairy cows after post-partum use

Claims made for prophylactic effects by a progestin (Chlormadione acetate = CAP) on fertility, given peroral daily to dairy cows from Day 15 to 35 post-partum, were investigated in field trials in a total of 1516 cows in Northern Germany, on 12 privately and one government-owned dairy farm, between 1969 and 1973. All animals were inseminated at estrus after Day 50 post-partum. For all treated animals, significant reduction of the calving interval by 11 days (p < 0.01) was recorded. In 942 cows, in which comparisons between treatment and control animals under identical environmental conditions were made, calving intervals were reduced by 10.5 days (p < 0.01) and the percentage of cows remaining infertile over two years was reduced from 12.4 % in the control population to 6.4 % in treated cows (p < 0.05). These advantages of CAP were most pronounced in cows older than 5 years and animals producing less than 25 kg milk/day during the first two months post-partum. In individual farms, calving intervals between treatment and control groups ranged from insignificant differences up to 44 days. Predictability of breeding dates, assurance of desirable short calving intervals and improved fertility makes this a tool for problem farms and well managed dairies alike.     

Association between evaluation of the reproductive tract by various diagnostic tests and restoration of ovarian cyclicity in high-producing dairy cows

The uterine condition of clinically normal postpartum Holstein-Friesian dairy cows (n = 45) was evaluated once weekly (Weeks 3 to 7) by endometrial cytology, vaginal mucus collection device (VMCD), vaginoscopy, and ultrasonography to establish a relationship with postpartum resumption of ovulatory cycles. The time of first detection of the corpus luteum (CL) by ultrasonography and plasma progesterone concentration ≥1 ng/mL was recorded. By 49 d postpartum, 78% of the cows (n = 35) had resumed ovarian function (CL group), whereas the remainder (n = 10) had no CL (NCL group). There was a positive correlation between VMCD score and presence of fluid in the uterus in cows with a CL (P < 0.01) during Week 3 postpartum but no significant correlation in cows without a CL. Percentage of polymorphonuclear leukocytes (PMN%) was higher in the NCL group (mean ± SEM, 24.6 ± 9.4%) than in the CL group (11.7 ± 2.2%) during Week 5 postpartum (P < 0.05). The PMN% (4.5 ± 6.5%) and VMCD (0.5 ± 0.5) scores during Week 5 in cows ovulating by Day 28 were lower (P < 0.01) than the PMN% (15.0 ± 14.3%) and VMCD (1.1 ± 0.9) scores in those ovulating by Day 49. In conclusion, higher PMN% at 5 wk postpartum was associated with delayed resumption of ovarian cyclicity in high-producing dairy cows.     

The effect of PGF-2 alpha on reproductive performance of naturally bred dairy cows with or without pyometra

Five hundred thirty-four naturally bred Holstein dairy cows from two Colorado dairies were examined $\text{per}$$\text{rectum}$ between 21 and 36 days after calving. Alternate cows in each herd received either 25 mg PGF-2 alpha or no treatment at the time of initial examination. No differences were found in days open or pregnancy rates between groups (P>0.25).Days open in 23 cows with pyometra were 98.7 ± 9.4, and 77.0 ± 2.2 in 493 herdmates without pyometra. The large inequalities in numbers precluded valid statistical comparisons between these groups. No overall difference (P>0.25) in reproductive performance was found in cows with pyometra treated at the initial examination compared to those not treated until two to four weeks after the initial examination. Contributing to the lack of significance were a number of cows with pyometra that had spontaneous cures before treatment was considered. Untreated cows that recovered spontaneously had better (P<0.05) reproductive performance than herdmates that required later treatments to initiate uterine evacuation. No overall advantage in reproductive performance was obtained by the routine treatment of postpartum dairy cows with PGF-2 alpha but treatment of cows with pyometra should not be delayed.