Relationship between plasma beta-carotene concentrations during the peripartum period and ovulation in the first follicular wave postpartum in dairy cows

Beta-carotene functions independently of vitamin A in the reproductive performance of dairy cows. The concentrations of beta-carotene in plasma decrease during the dry period, and reach a nadir in about the first week postpartum. This coincides with a negative energy balance, which affects the onset of the first ovulation in early postpartum cows. Thus, we hypothesised that plasma beta-carotene concentrations during the peripartum period may affect ovulation in the first follicular wave postpartum in dairy cows. The aim of the present study was to investigate changes in the profiles of plasma beta-carotene concentrations during the peripartum period in ovulatory and anovulatory cows during the first follicular wave postpartum. We used 22 multiparous Holstein cows, which were fed a total mixed ration consisting of grass, corn silage and concentrate, and collected blood samples for beta-carotene and progesterone analysis from week 3 prepartum to week 3 postpartum when the period of day 0-6 after parturition was regarded as the parturient week (week 0). The first ovulation was confirmed using the profile of plasma progesterone concentrations and colour Doppler ultrasound. Thirteen cows ovulated during the first postpartum follicular wave. Parity, the dry-off period, calving interval, mastitis episodes, and actual 305 days' milk yield during the previous lactation, and milk composition in the last month during the previous lactation in this study did not differ between ovulatory and anovulatory cows. Differences in the plasma beta-carotene profile were observed between ovulatory and anovulatory cows. Plasma beta-carotene concentrations at week 3 prepartum were greater in ovulatory cows (2.97+/-0.24 mg/L) than in anovulatory cows (1.53+/-0.14 mg/L; P<0.001), after that its concentrations in ovulatory cows decreased and reached the lowest level at week 1 postpartum, although its concentrations in anovulatory cows remained unchanged. No differences in plasma beta-carotene concentrations between the two groups were observed postpartum. The present study indicates for the first time that the lower beta-carotene concentrations in plasma during the prepartum period is associated with anovulation during the first follicular wave postpartum.     

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 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.     

Ovarian and endocrine responses and reproductive performance following GnRH treatment in early postpartum dairy cows

At calving forty-eight Holstein and Guernsey cows were assigned according to age and breed to one of six postpartum periods (1 or 2, 3 or 4, 5 or 6, 7 or 8, 12 or 13 and 18 or 19 days postpartum). Thirty-six of the cows (6 cows per postpartum period) received a single intramuscular injection of 100 μg GnRH. The other twelve cows (2 cows per postpartum period) served as controls and received a single intramuscular injection of the carrier vehicle for GnRH.Four of 36 cows administered GnRH and three of the 12 control cows ovulated by the day following treatment. Four of the cows were 12 or 13 days postpartum (1 control and 3 GnRH treated) and three were 18 or 19 days postpartum (2 controls and 1 GnRH treated). Six of the seven cows that ovulated the day following treatment had a follicle > 1.0 cm the day prior to treatment. Follicular growth was detected in the earlier postpartum periods but ovulation the following day was not detected for either control or GnRH treated cows. Following estrus or silent estrus, plasma progesterone concentrations increased to about 4 ng/ml on day 13. However, in cows ovulating the day following GnRH treatment, plasma progesterone declined from about 3 ng/ml on day 9 to approximately 1 ng/ml on day 13 postestrus. In addition, LH in plasma was higher (P < .01) ? through 13 days following estrus or silent estrus in cows ovulating the day after GnRH treatment in comparison to cows during the first or subsequent postpartum estrous cycles.In summary, in addition to days postpartum other factors including follicular development and maturity are probably involved in GnRH induced ovulation.     

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.     

Effect of intrauterine infusion of recombinant bovine interferon αI1 on luteal phase duration and oxytocin-induced release of 13,14-dihydro-15-keto-prostaglandin F2α in postpartum beef cows

The objective of this study was to determine if oxytocin-induced release of prostaglandin F₂α (PGF_2α; measured by the stable metabolite, 13,14-dihydro-15-keto-prostaglandin F₂α (PGFM)) was inhibited following intrauterine infusion of bovine interferon-α_I1 (rboIFNα_I1) into postpartum cows anticipated to have short estrous cycles following first ovulation postpartum. Cows expected to have short estrous cycles were assigned to receive twice daily intrauterine infusions of either placebo (SCP; n = 11) or 2 mg rboIFNα_I1 (SCIFN; n = 14) on Days 1–16 following hCG injection (2500 IU; day 0) on Days 30 or 31 postpartum. On Day 5 following hCG, each cow was injected with 100 IU oxytocin (i.v.) to induce the release of uterine PGF_2α (as measured by PGFM). Other treatment groups consisted of cows expected to have normal estrous cycle lengths following pretreatment with a 9 day norgestomet implant on Days 21 or 22 postpartum followed by hCG injection to induce ovulation. Cows expected to have normal estrous cycle lengths received twice daily intrauterine infusions of either placebo from Days 1 to 16 of the cycle and 100 IU oxytocin (i.v.) on Day 5 (NCPE; n = 11) or twice daily infusions of placebo (NCPL; n = 7) or rboIFNα_I1 (NCIFN; n = 10), from Day 13 post-hCG injection until luteolysis. Oxytocin was injected (100 IU; i.v.) into cows in the NCPL and NCIFN groups on Day 16. The calculated areas under the curve (arbitrary PGFM units) were: 164 ± 18 units, 96 ± 16 units, 93 ± 18 units, 137 ± 27 units and 53 ± 20 units for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCIFN < SCP; NCIFN < NCPL; P < 0.015). Mean luteal phase length was calculated as the number of days from injection of hCG until progesterone declined to below 0.5 ng ml⁻¹ and was: 6.7 ± 1.0 days, 10.5 ± 0.9 days, 12.0 ± 1.0 days, 18.0 ± 1.3 days and 20.7 ± 1.1 days for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCP < SCIFN = NCPE < NCPL = NCIFN; P < 0.01). In summary, luteal phase lengths were increased and oxytocin-induced release of PGFM was reduced by rboIFNα_I1 infusion in cows anticipated to have short luteal phases.     

Postpartum resumption of ovarian cycling activity in first-calf suckled beef cows exposed to familiar or unfamiliar bulls

The objective of this experiment was to determine if the proportion of first-calf suckled beef cows that resumed ovulatory cycles and the interval to resumption of ovarian cycling activity differ after exposure to either “unfamiliar” bulls or cows on d 35 postpartum, after exposure to either “familiar” bulls or cows for the first 30–32 d after calving. Fifty Angus × Hereford cows were stratified by calving date, calf BW, and calf sex by d 3 postpartum, and assigned to be exposed to familiar epididectomized bulls (BEF; n = 25) or familiar mature ovariectomized (OVX) cows (CEF; n = 25). On d 35 after calving, 12 BEF cows were assigned to be exposed to unfamiliar bulls (BEU); likewise, 12 CEF cows were assigned to be exposed to unfamiliar OVX cows (CEU). Cows were in their treatments for either 95 d (BEF and CEF) or 60 d (BEU and CEU) during the experiment. Blood samples were collected every third d from the beginning to the end of the experiment. A rise in progesterone concentration of >0.5 ng/mL in consecutive samples was used as the criterion for resumption of ovulatory cycles. Exposing cows to bulls on d 5 after calving and then switching a subset of these cows to be exposed to unfamiliar bulls 30–32 d later did not (P > 0.10) alter: (1) the proportion of cows that resumed cycling activity; and (2) postpartum interval to resumption of ovarian cycling activity compared to cows exposed to familiar bulls. However, 32% more (P < 0.05) cows exposed to bulls (BEF and BEU) resumed cycling activity by approximately 14.8 d before cows that were exposed to OVX cows (CEF and CEU). We conclude that the familiarity of first-calf cows to either bulls or ovariectomized cows, did not affect the postpartum occurrence of cycling activity or the interval from calving to resumption of ovulatory cycles. However, bull exposure, whether familiar or unfamiliar, stimulates first-calf cows to resume ovulatory cycles sooner after calving than if they are not exposed to bulls.     

A Survey of the Postpartum Reproductive Performance of Dairy Cows with Fertility Problems in Southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals. There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving. The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations. Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.     

Effects of dietary conjugated linoleic acid on metabolic status,BW and expression of genes related to lipid metabolism in adipose tissue of dairy cows during peripartum

Conjugated linoleic acid (CLA) dietary supplementation reduces milk fat content and yield, but its effects on lipid metabolism and energy status remain controversial. The objective of this study was to investigate the effects of dietary CLA on adipose tissue (AT) mRNA abundance of genes related to lipid metabolism, plasma indicators of metabolic status, body condition score (BCS) and BW changes in dairy cows. Sixteen multiparous Holstein cows (3.2 ± 1.4 lactations, 615 ± 15 kg BW) were randomly assigned to treatments: 1) CLA; rumen-protected CLA (75 g/d) or 2) Control; equivalent amount of rumen inert fatty acid (FA) as the previous diet (78 g/d), from − 20.2 ± 3.2 (mean ± SEM) to 21 d relative to calving (d 0). Subcutaneous AT was biopsied from the tail-head region at d 21 to determine the mRNA abundance of genes related to lipid metabolism. Blood samples were collected at − 20.2 ± 3.2, 0, 7, 14 and 21 d relative to calving to determine plasma non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), insulin and glucose. Conjugated linoleic acid decreased milk fat yield and milk fat content by 15 and 16%, respectively. Cows fed CLA had lower plasma NEFA and BHBA and greater glucose and insulin concentrations (P < 0.05). Mean BCS at 21 d postpartum was greater (P < 0.01; 2.89 vs 2.25), and BCS loss from the day of enrollment to 21 d postpartum was reduced (P < 0.01; − 0.13 vs − 0.64) in the CLA group. The expression of acylcoenzyme A oxidase, carnitine palmitoyltransferase 1A, hormone-sensitive lipase, β2 adrenergic receptor and acetyl-CoA carboxylase was downregulated by CLA supplementation, whereas the expression of sterol regulatory element binding protein, lipoprotein lipase and peroxisome proliferator-activated receptor gamma was upregulated (P < 0.01). In summary, CLA-supplemented cows showed signs of better metabolic status and less severe fat mobilization. Moreover, CLA increased mRNA abundance of genes related to lipogenesis and decreased mRNA abundance of genes related to FA oxidation and lipolysis in the AT of dairy cows during early lactation.     

Effect of corticoid induced parturition on lactation and on prepartum profiles of serum progesterone and the estrogens among cows retaining and not retaining fetal membranes

Twenty-one mature F1 Brahman-Hereford cows were treated with 25 mg of dexamethasone (DEX) on day 279 or 280 of gestation to induce birth prematurely. Eigth cows were untreated (UT). Blood was sampled on day 279 or 280 of gestation just prior to treatment of cows with DEX (0 hr), at least daily thereafter to calving and within 1 hr postpartum. Concentrations of progesterone (P₄), estrone (E₁) and estradiol-17β (Eβ) and -17α (Eα) in blood serum were measured by radioimmunoassay. Among 21 cows treated with DEX, 16 (76%) calved within 78 hr (52±3 hr). Eleven of the 16 cows retained fetal membranes more than 12 hr (RFM) and five cows did not retain fetal membranes (NRFM). Five cows (24%) treated with DEX calved 266±46 hr later (NOR) on day 290±1 of gestation compared to day 286±2 for cows in group UT. No cow in groups NOR or UT had RFM. Failure of group NOR to calve prematurely appeared due to elevated serum P₄ (P<.05), low serum Eβ (P<.10) and other estrogens (P>.10) pretreatment, and to only a 32% decrease in serum P₄ within 72 hr after treatment. Serum estrogens, especially Eβ, were next lowest pretreatment in group RFM. However, in group RFM, all serum estrogens increased (P<.10 to P<.01) within 48 hr after treatment, reached higher concentrations and peaked later in relation to calving than in other groups (NRFM, NOR and UT). Synchronization of placental maturation and parturition may require a longer period of elevated serum estrogens prior to calving than was observed in group RFM. Treatment of cows prepartum with DEX had no effect on gain of calves, milk yield or yields of fat, total protein and total solids in milk during the first 12 weeks of lactation.     

Duration of daily bull exposure on resumption of ovulatory activity in postpartum,primiparous, suckled,beef cows

The objective of this experiment was to determine if duration of daily bull exposure influences length of postpartum anestrus in primiparous, anovular, suckled, beef cows. The null hypotheses were that intervals from calving or the start of bull exposure (D 0) to resumption of ovulatory activity (OA), and proportions of cows that resumed OA during the experiment does not differ among cows exposed to bulls for 0 h, 6 h, or 12 h daily, and that there is no relationship between the duration of bull exposure and interval to resumption of OA in cows exposed to bulls for 0 h, 6 h, or 12 h daily. At 51.5 ± 2.3 d (±SE) after calving, cows were assigned randomly to be exposed for 12 h (BE12; n = 15) or 6 h daily (BE6; n = 14) to bulls, or not exposed to bulls (NE; n = 10) for 45 d. Interval from calving or from D 0 to resumption of OA was shorter (P < 0.05) and the proportion of cows that resumed OA during the experiment was greater (P < 0.05) for BE12 than for NE cows. Interval from D 0 to resumption of OA did not differ (P > 0.10) between BE6 cows and either BE12 or NE cows. However, interval from calving to resumption of OA was shorter (P < 0.05) for BE6 than NE cows. The proportion of cows that resumed OA did not differ (P > 0.10) between BE6 cows and BE12 cows; however, the proportion of cows that resumed OA during the experiment tended (P = 0.08) to be greater for BE6 cows than for NE cows. There was a linear relationship between intervals from calving (b₁ = −7.64 d/h; P < 0.05) and D 0 (b₁ = −3.3 d/h; P < 0.05) to resumption of OA and duration of daily bull exposure. Thus, the duration of bull-pheromone stimuli that cows perceive each day is related to when primiparous, postpartum, anestrous, suckled cows respond to this stimulus and undergo the physiological changes necessary to resume ovulatory activity.     

Importance of dam BW change and calf birth weight in double-muscled Belgian Blue cattle and its relationship with parity and calving interval

Factors affecting calving interval (CI) in double-muscled Belgian Blue (DMBB) beef cows were investigated with regard to the BW yield (BWY) of the cow–calf pair, using 834 CI records from 386 females with parities 1 to 6. The effect of parity and CI on BWY was also studied. Cow–calf pair BWY was defined as calf birth weight plus dam BWY per CI. CI (mean±s.e.: 404±1.9 days) was affected by parity, calving season, suckling and calf birth weight/dam weight. Primiparous cows had a shorter CI than cows with three or more calvings (P<0.05), with an intermediate CI for second-calf cows. Spring calvings resulted in a shorter CI than summer and autumn calvings, with intermediate values for winter calvings. Suckling dams had longer CIs than non-suckling dams. There were interactions (P<0.05) between calving season and suckling, and between calving season and mating system. Shortest CIs were observed for spring calvings in case of non-suckling and for summer calvings in case of suckling. Longest CIs were observed for autumn calvings in case of natural service (NS) and for winter calvings in case of artificial insemination (AI). Calf birth weight/dam weight of 6% to 10% resulted in shorter CI than a ratio of <6% (P<0.05). Body condition and mating system (NS v. AI) did not affect CI. Daily cow–calf pair BWY was affected by parity (P<0.001) and CI (P=0.013), with a tendency for an interaction (P=0.094). Daily cow–calf pair BWY did not differ for CIs of <12 to 16 months in primiparous cows and was lowest for a CI of 13 to 15 months in second-calf cows, whereas the effect of CI was more variable in older cows. Dam contribution to cow–calf pair BWY was larger than calf birth weight in first- and second-calf cows, and increased with increasing CI. Dam contribution to cow–calf pair BWY was smaller than calf birth weight in older cows, varying from 0.2 to 1.0 depending on CI. A short CI is advised for DMBB cows because of a larger BWY and more efficient nutrient utilisation.     

Influence of parity on follicular dynamics and resumption of ovarian cycle in postpartum dairy cows

The present study examined ovarian changes preceding the resumption of the ovarian cycle in postpartum dairy cows with different parities under similar body nutritional conditions. In postpartum primi- (n=6), bi- (n=4), and multiparous (n=6) Holstein dairy cows, ovarian ultrasonographic observations starting at 7 days after calving were performed every other day and then daily after the confirmation of clinical signs of oestrus for the detection of postpartum first ovulation. Blood samples were collected at the same time as ultrasonography and analyzed for oestradiol and progesterone to monitor ovarian activity. To evaluate the nutritional condition of the cows, body weight and body condition score (BCS, 1=emaciated to 5=obese) were measured weekly and blood samples for the analysis of glucose, insulin, and non-esterified fatty acid (NEFA) were collected at the same time until postpartum second ovulation. Dominant follicles (>8mm in diameter) of the first follicular wave were detected at 7 days after calving in all cows. The first wave follicle ovulated in five of six multiparous cows, whereas no first wave follicle ovulated in any of the primiparous cows. The days to first ovulation after calving in primiparous cows (31.8+/-8.3 days) were significantly greater (p<0.05) than those in multiparous cows (17.3+/-6.3 days), but were not significantly different from biparous cows (28.8+/-8.6 days). There was a significant relationship between parity and days to first ovulation after calving (p<0.05). BCS was maintained at a level of more than 2.5 during the postpartum period in all cows and there was no influence of parity on postpartum changes in BCS, glucose, insulin, or NEFA throughout the experiment. The present study demonstrated a negative relationship between parity and number of days from calving to first ovulation in dairy cows under similar body nutritional conditions. It is possible that the influence of parity on the resumption of ovarian cycle is modulated by the factors different from the nutrition-related changes during the postpartum period in dairy cows.     

Induction of twinning in Holstein and Japanese black cows by ipsilateral frozen embryo transfer

Induction of twinning by ipsilateral nonsurgical transfer of two frozen-thawed Japanese Black bovine embryos to each of 20 Holstein and 26 Japanese Black cows, that had been kept under a stable in private farm conditions, was examined. The cows were monitored every 20 days from Day 25 to Day 65 of gestation for pregnancy and fetus survival (estrus is Day 0). Seventy-five per cent (15 of 20), 65.0% (13 of 20) or 60.0% (12 of 20) and 61.5% (16 of 26), 53.8% (14 of 26) or 50.0% (13 of 26) of Japanese Black cows were diagnosed pregnant at 25, 45 and 65 days after transfer by ultrasonic echography. Embryonic losses were observed between Days 25 and 65 in 29.2% (7) Holstein and 31.8% (7) Japanese Black cows. The twin pregnancy rate in Holstein and Japanese Black cows decreased with time; 60.0% (9 of 15) vs. 37.5% (6 of 16) at Day 25; 53.8% (7 of 13) vs. 28.6% (4 of 14) at Day 45 and 41.7% (5 of 12) vs. 15.4% (2 of 13) at Day 65. At calving, Holstein cows produced five sets of twins and seven single calves, and Japanese Black cows two sets of twins and 11 single calves. The twinning rate in Holstein cows was higher (P < 0.05) than that in Japanese Black cows, 41.7% (5 of 12) vs. 15.4% (2 of 13). The calf birth weight in Holsteins was heavier (P < 0.05) than that in Japanese Black dams (24.5 kg, 33.6 kg vs. 19.3 kg, 25.5 kg for twin and single calves). The placental weight in Holstein dams calving twins was heavier than that in Holstein dams calving a single calf or in Japanese Black dams calving either twins or a single calf (6.6 kg vs. 3.5 kg, 4.6 kg or 2.8 kg). The number of placentome in Holstein dams calving twins was also higher (P < 0.05) than that in Holstein dams calving a single calf or Japanese Black dams (103.5 vs. 41.8, 67.9, 33.0). The number of placentome was approximately double in dams calving twins than that of dams calving a single calf.     

Effect of intermittent injections of gonadotrophin releasing hormone at various frequencies on the release of luteinizing hormone and ovulation in dairy cows

Gonadotrophin releasing hormone (GnRH, 5 μg every 4 h) was administered to six dairy cows between days 5 and 10 post-partum and the release of luteinizing hormone (LH) and the onset of ovulation were determined. LH was measured using a specific radioimmunoassay and the occurrence of ovulation was assessed from changes in the concentration of progesterone in milk. Treatment with GnRH resulted in a median time of first ovulation of 17.0 days after calving. This was less (P < 0.05) than that observed for control cows (21.5 days, n = 7). Determinations of plasma LH concentrations over an 8-h period on days 6 and 10 post-partum indicated that there was a tendency for GnRH-treated cows to have higher levels of LH on these days. The 5 μg dose of GnRH did not repeatably induce a release of LH between days 6 and 10. Endogenous pulsatile release of LH did, however, increase in frequency from 3.18 pulses per 8 h on day 6 to 5.18 pulses per 8 h on day 14 post-partum (P < 0.01).In a second experiment groups of 20 cows were treated with either 5 μg GnRH every 4 h or 15 μg GnRH every 12 h from days 5 to 10 post-partum. Seventeen untreated cows served as controls. The median times to first ovulation were 27.0 days for the control cows, 22.5 days for those cows treated with 5 μg GnRH every 4 h and 17.0 days for cows treated with 15 μg every 12 h. The latter treatment significantly advanced the time of first ovulation (P < 0.05) relative to controls. This difference had, however, disappeared by the time of the second and third ovulations. Primiparous cows ovulated later (P < 0.01) than the pluriparous cows in the group treated with 5 μg GnRH every 4 h. This was a major reason for the lack of effect of this treatment. Some treated cows were blood sampled at frequent intervals on day 8 to evaluate the LH responses to GnRH injections. The administration of 5 μg GnRH on day 8 did not elicit a pulse of LH which could be distinguished from endogenous pulsatile secretion at this time. The dose of 15 μg on this day did, however, elicit a more defined pulse on some, but not all, occasions.The injection of a small dose of GnRH twice a day from day 5 to day 10 after calving, therefore, advanced the time of first ovulation in dairy cows by 10 days.     

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 days after calving on insulin-like growth factor-I, insulin-like growth factor binding proteins, progesterone, androstenedione, estradiol, and aromatase mRNA in dominant follicles of postpartum beef cows

The effect of days after calving on IGF-I, IGFBP, progesterone, androstenedione, estradiol, and aromatase mRNA in dominant ovarian follicles (DF) was evaluated in Angus × Hereford cows. Growth of DF (>9 mm) was monitored daily by ultrasonography and fluid from DF was collected in vivo at either 30 ± 2 d or 47 ± 2 d postpartum. Follicular fluid (FF) was also aspirated from DF of contemporary ovulatory cows at proestrus. Estrous behavior was monitored continuously using the HeatWatch system, and progesterone in plasma collected twice weekly was used to assess luteal activity. Anovulatory DF aspirated 30 and 47 d postpartum had similar concentrations of IGF-I, IGFBP, progesterone, estradiol and androstenedione in FF and IGF-I and IGFBP in plasma. The intervals from aspiration to estrus were similar for cows aspirated 30 and 47 d postpartum. Proestrous follicles had greater (P < 0.01) estradiol (435 ± 79 ng/mL) than DF at 30 d (107 ± 63 ng/mL) or 47 d (68 ± 53 ng/mL) after calving. Concentrations of androstenedione in FF were also greater (P < 0.01) in proestrous follicles than in DF aspirated at 30 or 47 d after calving. Concentrations of insulin-like growth factor-1 (IGF-I) and insulin-like growth factor binding proteins (IGFBP) in FF and plasma, and aromatase mRNA in granulosa cells were similar for anovulatory and proestrous cows. In conclusion, estradiol production by DF of postpartum anovulatory cows may be limited by inadequate production of androstenedione during the postpartum anovulatory interval and this may influence follicular maturation. Concentrations of IGF-I and IGFBP were similar in anovulatory and proestrous cows, an indication that alterations in the IGF-I system in the DF at 30–47 d after calving are not associated with delayed follicular development in postpartum beef cows.     

Modifying the double-Ovsynch protocol to include human chorionic gonadotropin to synchronize ovulation in dairy cattle

The objectives were to determine whether rates of conception, ovulation, presynchronization, or follicle and CL characteristics were altered after modifying the Double-Ovsynch (DO) protocol to include hCG compared with the DO protocol. Primiparous and multiparous lactating dairy cows (N = 183), and nulliparous dairy heifers (N = 51) were used. Cows were blocked by parity and heifers were stratified by age and breed before being randomly assigned to one of two treatments. All females received either 100 μg GnRH or 2000 IU hCG im, at initiation of the Pre-Ovsynch (PO) portion of the DO protocol (PO: GnRH/hCG, 7 days PGF_2α and 3 days GnRH). After 7 days, females started the Breeding-Ovsynch portion of the DO protocol (Breeding-Ovsynch: GnRH, 7 days, PGF_2α, 48 or 56 h and GnRH 16 hours timed artificial insemination with sex-sorted semen). Transrectal ultrasonography and blood samples were used to assess ovarian structures, ovulation, pregnancy diagnosis, and concentration of progesterone in plasma. Conception rates were similar in females treated with GnRH or hCG in cows (32.2 and 25.0%) and in heifers (30.8 and 36.0%). Ovulation rates in cows at the onset of PO were increased with hCG compared to GnRH (77.2 vs. 62.2%, P < 0.05). Concentrations of progesterone 7 days post-hCG or GnRH were greater in cows treated with hCG compared with GnRH (least significant mean ± SEM; 4.3 ± 0.3 and 3.0 ± 0.3 ng/mL, P < 0.01), but did not differ in heifers (4.5 ± 0.9 and 2.9 ± 0.9 ng/mL). More cows ovulated within 7 days post-hCG and a greater proportion of these cows tended to have failed luteal regression by Day 3 post-PGF_2α compared with cows that had ovulated to GnRH (29.6 vs. 16.1%, P ≤ 0.10). The overall percentage of females which were synchronized to PO did not differ between GnRH- or hCG-treated cows (61.5% and 52.2%) and heifers (42.3% and 40.0%). In conclusion, no overall improvement in fertility was achieved by replacing the first injection of GnRH in the DO protocol with hCG.     

Feeding dried distillers grains with solubles to lactating beef cows: impact of excess protein and fat on cow performance,milk production and pre-weaning progeny growth

Multiparous Angus×Simmental cows (n=54, 5.22±2.51 years) with male progeny were fed one of two diets supplemented with either dried distillers grains with solubles (DDGS) or soybean meal (CON), from calving until day 129 postpartum (PP) to determine effects of excess protein and fat on cow performance, milk composition and calf growth. Diets were formulated to be isocaloric and consisted of rye hay and DDGS (19.4% CP; 8.76% fat), or corn silage, rye hay and soybean meal (11.7% CP; 2.06% fat). Cow–calf pairs were allotted by cow and calf age, BW and breed. Cow BW and body condition score (BCS; P⩾0.13) were similar throughout the experiment. A weigh-suckle-weigh was performed on day 64 and day 110±10 PP to determine milk production. Milk was collected on day 68 and day 116±10 PP for analysis of milk components. Milk production was unaffected (P⩾0.75) by dietary treatments. Milk urea nitrogen was increased at both time points in DDGS compared with CON cows (P<0.01). Protein was decreased (P=0.01) and fat was increased (P=0.01) in milk from DDGS compared with CON cows on day 68 PP. Compared to CON, DDGS decreased medium chain FA (P<0.01) and increased long chain FA (P<0.01) at both time points. Saturated FA content of milk was decreased (P<0.01) at both time-points in DDGS compared with CON cows, which resulted in an increase (P<0.01) in monounsaturated and polyunsaturated FA, including cis-9, trans-11 conjugated linoleic acid. Daily gain of the DDGS calves was increased (P=0.01) compared with CON calves, resulting in heavier BW on day 129 (P=0.01). Heavier BW of DDGS calves was maintained through weaning (P=0.01). Timed-artificial insemination (TAI) rates were greater for cows fed DDGS compared with cows fed CON (P<0.02), but dietary treatment had no effect on overall pregnancy rates (P=0.64). In summary, feeding DDGS to lactating beef cows did not change cow BW or BCS, but did improve TAI rates and altered milk composition compared with CON. As a result, male progeny from cows fed DDGS during lactation had greater average daily gain and were heavier at day 129 and at weaning compared with male progeny from cows fed a control diet.