Service Conception Rate Research Articles

Reproductive performance in anestrous dairy cows following treatment with two protocols and two doses of progesterone

The objectives of this study were to evaluate the effect using two doses of progesterone (P4) releasing devices in two different programs on reproductive performance of anestrous dairy cows. Cows ( n = 1555) not detected in estrus by 10 d before the planned start of the seasonal breeding program and in which no CL was palpable were treated with an intravaginal P4-releasing device (‘Single’; ∼1.56 g of P4) or a modified device with triple the normal P4 dose (‘Triple’; ∼4.7 g of P4). The devices were in place for either 6 d (‘Short’) or 8 d (‘Long’), with 1 mg estradiol benzoate (EB) given 24 h after device removal. The ‘Long’ program also included treatment with 2 mg EB at device insertion. The Long program resulted in a higher first service conception rate (RR = 1.18 (95% CI = 1.03–1.33); P = 0.02), but had no effect on the 28-d, 56-d or final pregnancy rate compared to the Short program. There were no effects of dose of P4 on any outcome. In conclusion, the Long compared to the Short program, but not the dose of P4, improved first service conception rates in anestrous cows.

Endometritis treatment with a PGF 2α analog does not improve reproductive performance in a large dairy herd in Argentina

In Argentina, most dairy cows with endometritis are treated with prostaglandin (PGF 2α or its analogs) and insemination is withheld until there are no signs of endometritis. The objective of the present study was to evaluate if this method of managing endometritis enhances reproductive performance. Three experiments were conducted over 4 years in a large farm in the west of Buenos Aires province. In Experiment 1, half of the cows diagnosed with endometritis (>1.5-fold difference in diameter of uterine horns, as determined by rectal palpation) received standard endometritis management (treatment with tiaprost, a PGF 2α analog, rectal palpation every 20 days, and withholding of AI until endometritis apparently resolved) and the other half was untreated, with AI at the first estrus after the voluntary waiting period. Untreated cows were inseminated and conceived 20 days earlier than treated cows, and the pregnancy rate by Day 90 postpartum was higher in the untreated group. In Experiment 2, cows with endometritis were divided into four groups according to the severity of symptoms; within each group, cows were allocated to treatment or control, as in Experiment 1. Although first service conception rate decreased as endometritis severity increased, reproductive performance in treated versus control cows was similar to that of Experiment 1 (with no interaction due to degree of endometritis). Re-evaluation of the treated cow (to confirm uterine “normality”) may have been responsible for the delay in conception in both experiments. The objective of Experiment 3 was to determine the effects of tiaprost treatment on clinically normal postpartum cows (no evidence of endometritis). Tiaprost treatment reduced the interval from calving to conception in multiparous cows, but it delayed conception and reduced the conception rate in primiparous cows. In conclusion, treatment with tiaprost impaired reproductive performance in primiparous cows (in the absence of endometritis). Furthermore, the standard treatment for endometritis (treatment with a prostaglandin analog and withholding insemination until clinical signs abated) impaired reproductive performance and increased costs.

Influence of Bovine Somatotropin on Characteristics of Estrus and Reproduction of Holstein Cows During Summer Months

A field trial was conducted to evaluate the effects of bovine somatotropin (bST) on estrous characteristics of multiparous, lactating Holstein cows (n = 44) during the summer months. Cows were randomly assigned to receive bST every 14 d or no bST (control) and were fitted with a HeatWatch® transmitter (HW; DDx Inc., Denver, CO). A temperature-humidity index (THI) was calculated for the day of estrous onset. Ranges of THI were 68 to 80 (THI < 72 = THI 1 [no heat stress], THI 72 to 76 = THI 2 [mild heat stress], THI > 76 = THI 3 [moderate heat stress]). Duration of estrus, number of standing events, and quiescent periods between standing events were similar (P>0.10) between bST and control cows. The number of standing events was influenced (P<0.05) by THI and averaged 20.3 ± 3.0, 8.6 ± 1.3, and 8.9 ± 1.2 for THI 1, THI 2, and THI 3, respectively. Quiescent periods observed between standing events tended (P=0.11) to be influenced by THI and were 1.2 ± 0.8, 3.0 ± 0.4, and 3.0 ± 0.4h for THI 1, THI 2, and THI 3, respectively. Days to first service were less (P=0.07) for bST-treated cows (90.9 ± 5.1 d) than for control cows (105.9 ± 6.1 d). First service conception rates and pregnancy rates were similar (P>0.10) between bST-treated and control cows. We conclude that estrous characteristics and pregnancy rates of lactating dairy cows were not influenced by bST treatment. However, the number of standing events was reduced, and quiescence between mounts tended to increase, in lactating dairy cows as ambient temperature and humidity increased.

Effect of Certain Immunomodulators on Uterine Infections and Fertility in Post Partum Buffaloes

The present study was aimed to study the effect of aqueous extract of Tinospora cordifolia and autologous plasma on uterine infections. Buffaloes in estrus, 40 days and above postpartum were checked for uterine infections. Animals having uterine infections were randomly divided into three groups of six animals each. Buffaloes in group I, II and III (control) were given intrauterine infusion of aqueous extract of Tinospora cordifolia (3,000 mg total dose), autologous plasma (150 ml) and phosphate buffer saline (150 ml) respectively, in three divided doses, once daily for three consecutive days, starting from the day of estrus. A fourth group (IV) comprising of six buffaloes having no uterine infection was also included in the present study. Buffaloes were inseminated artificially on next estrus following treatment and confirmed for pregnancy 60 days later. Bacterial population in CVM of buffaloes in group I, II and III was significantly (p<0.05) higher than group IV. After treatment there was a significant (p<0.01) reduction in bacterial population in group I (83.496±7.755%) and group II (80.233±5.799%) than group in III (7.557±33.551%) at next estrus. There was non-significant improvement in first service conception rate (CR, 33.33%) and overall conception rate (OCR, 27.27%) in group I, in comparison to group III (first service CR-16.67%; OCR-20.0%). No significant improvement was seen in OCR (22.22%) in-group II also in comparison to group III. The improvement in group I was however, nonsignificantly lower than normal animals of group IV (First service CR-16.67%; OCR-36.33%). (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 7 : 930-935)

19POSTPARTUM ANESTROUS TREATMENT WITH INTRA-VAGINAL PROGESTERONE DEVICE OR CALF REMOVAL FOR 120 HOURS IN SUCKLED CROSSBRED DUAL PURPOSE COWS

Postpartum anestrus is the main reproductive problem that affects crossbred cattle production in Venezuela. (Soto et al., 2002 Theriogenology 57, 1503–1510; Soto et al., 2000 Revista Científica FCV-LUZ 10, 391–398). In order to reduce the postpartum anestrus and lower the calving to conception interval, 167 crossbred (Bos indicus×Bos taurus) anestrous cows between 90 and 130 days postpartum with body condition score 3 (scale 1–5) were randomly allotted to one the following treatments: 1) PH (n=59), intravaginal sponge (IS) impregnated with 250mg of medroxyprogesterone acetate (MAP) during 7 days+50mg of MAP and 5mg of 17β-estradiol (17β-E) i.m. at the day of sponge insertion (Day 0), plus 500 IU of eCG i.m. at Day 5 and1.5mg of 17β-E i.m. at Day 8 (PREGNAHEAT-E, VIATECA, Villa del Rosario, Venezuela); 2) CR (n=57), 120-h temporary calf removal; and 3) CG (n=20), control group. Work was performed in a commercial farm located in a subhumid tropical forrest region. Estrus, first service conception and pregnancy rate were analyzed by chi-square analysis. The intervals to conception were analyzed using analysis of variance (GLM) and the means was compared by least square means method. To evaluate the treatment effect, the interval to conception of each pregnant cow during the first 100 days were considered for the analysis. This interval (days) was significantly (P≤0.05) higher in the PH treatment (155.9±7.3) compared to control (174.4±8.1) but no differences were shown between PH and CR (161.0±7.8). Other results are shown in Table 1. PH treatment improved the estrus and pregnancy rates and shorten the interval to conception indicating that this is a promising anestrous treatment for suckled crossbred dual purpose cows under tropical conditions. Table 1. Reproductive performance of postpartum anestrous suckled cows treated with intravaginal progesterone or temporary calf removal

Effect of feeding calcium salts of long-chain fatty acids, from palm fatty acid distillate or soybean oil, to high producing dairy cows on milk yield and composition, and on selected blood and reproductive parameters

Calcium salts of long-chain fatty acids from palm fatty acid distillate (CaPFAD) and soybean oil (CaSOFA) were compared using 14 first lactation and 26 multiparous Holstein cows housed in a free-stall barn. It was hypothesized that if replacing CaPFAD with CaSOFA, a rich source of linoleic acid, could result in increased conjugated linoleic acid (CLA) content in milk without losing the lactational and reproductive benefits of feeding CaPFAD, this would be beneficial to the dairy industry and public health, as well as potentially enhance the consumption of dairy products. Cows were group-fed one of two total mixed rations (TMR) containing 1.7% CaPFAD or CaSOFA (DM basis) for ad libitum intake following recommendations from the manufacturer of the fat supplements. Fatty acid profiles (g/100 g of fatty acid) of CaPFAD and CaSOFA, respectively, were 16:0: 48.1, 12.1; 18:0: 4.27, 5.34; 18:1: 35.7, 23.9; and 18:2: 8.9, 51.2. Cows spent about 45 days in the fresh group, after which they were moved to high producing group where they stayed up to 10 weeks post-partum within their treatment assignments. The TMR (DM basis) were 50:50 forage:concentrate for both the fresh group and high producing group cows and contained (DM) 28% NDF and 18% CP. There were no treatment differences in milk yield, milk fat percentage, milk CLA content, milk true protein percentage, milk lactose percentage, milk urea N, linear somatic cell count and change in body condition score. Cows fed CaSOFA produced milk containing a higher content of 18:1(t) ( P<0.01) and 18:2 ( P<0.01) during weeks 8–10 post-partum, and had smaller follicles at ovulation ( P=0.03). Cows had similar concentrations of serum nonesterified fatty acids and β-hydroxybutyrate, and similar 30 days uterine score, days to first ovulation, days to first service, first service conception rate and progesterone concentration. In conclusion, while cows fed CaSOFA had similar lactational and reproductive performance to cows fed CaPFAD, the anticipated beneficial effect of enhancing content of CLA in milk was not realized from feeding CaSOFA at 1.7% of expected DM intake.

Influence of stage of lactation and milk production on conception rates after timed artificial insemination following Ovsynch

Conception rates after timed artificial insemination (TAI) are of paramount importance for the success of protocols based on synchronization of ovulation. Stage of lactation and milk production level are known factors that influence dairy cow fertility. It was the objective of this study to analyse the effect of stage of lactation and milk production level on conception rates and pregnancy rates by 200 days in milk (DIM) in dairy cows synchronized with the Ovsynch protocol (Day −10, Day −1: 0.1 mg of D-Phe6-gonadorelin, Day −3: 0.5 mg of cloprostenol, Day 0: AI). A total of 1288 dairy cows were assigned to two groups and classified in three production levels (high, average, low). Cows of all milk production levels in Group 1 (Simultaneous Ovsynch, SO) were synchronized with the Ovsynch protocol simultaneously for TAI between 73 and 81 DIM. In Group 2 cows with average milk production were synchronized at the same time as Group 1, while low producing cows were synchronized 3 weeks earlier and high producing cows were synchronized 3 weeks later than Group 1, respectively. First service conception rates (FSCRs) were lower ( P<0.05) in cows synchronized earlier than in cows of the same production level synchronized later (low production: 14.4% (22/153) versus 34.5% (51/148); high production: 28.2% (40/142) versus 41.4% (53/128)). Milk production level had no significant impact on conception rates after TAI in cows synchronized at the same stage of lactation. At 200 DIM fewer cows with high production level were pregnant than cows with average or low production ( P<0.05). This effect was independent of the stage of lactation at the initiation of Ovsynch. Endometritis at a postpartum examination did not influence conception rates after TAI. In conclusion, stage of lactation, but not milk production level, has a major influence on conception rates after TAI. Early AI after Ovsynch is less efficient and therefore its return on investment should be evaluated carefully.

Effect of royal jelly and GnRH on the estrus synchronization and pregnancy rate in ewes using intravaginal sponges

The influence of natural royal jelly (RJ) paste and gonadotropin releasing hormone (GnRH) on reproductive responses of Awassi ewes was evaluated. In May 1998, 20 Awassi ewes (aged 2–5 years and weighing 52 kg) were treated with 40 mg fluorogestone acetate (FGA) impregnated intravaginal sponges for a period of 12 days. Half of the ewes were administered orally a total of 3 g RJ paste in 12 equal doses of 250 mg per day starting at FGA sponge insertion while the remaining half received no RJ paste. Ewes were exposed to two fertile Awassi rams from the time of FGA sponge removal (0 h, 0 day). Blood samples were drawn on alternate days from days 0 to 19. Five ewes per group (RJ and control) were randomly selected to receive a 50 μg GnRH injection 28 h post-sponge removal. No interactions were detected between RJ and GnRH. Incidence of estrus was greater (8/10 versus 4/10) in RJ-treated than in control ewes and intervals from 0 h to detected estrus were similar (45±4.1 h versus 55±6.7 h, respectively). Progesterone concentration increased on days 5–7 in all ewes and remained elevated through day 19 in 60% of the RJ-treated and 20% of the control ewes. These ewes lambed on average 149 days later and the number of lambs born was similar between the two groups of ewes. Regardless of RJ treatment, GnRH administration decreased ( P<0.05) the interval from cessation of treatment to estrus. The first rise in plasma progesterone occurred on day 5 in GnRH-treated compared with day 7 for non-GnRH-treated ewes ( P<0.05). The results demonstrate that RJ treatment in conjunction with a source of exogenous progesterone can be used to induce estrus and increase first service conception rate in sheep. Administration of GnRH reduced the interval to estrus and advanced plasma progesterone elevation.

The Effect of Stage of Estrous Cycle at the Initiation of an Ovsynch Protocol on the Conception Rate

A reproductive management protocol has been developed to synchronize time of ovulation in lactating dairy cows (Ovsynch). This protocol allows an effective management of reproduction in dairy cows without continuous detection of estrus. We evaluated whether initiation of an Ovsynch protocol at different stages of the estrous cycle altered the conception rate after timed artificial insemination (AI). A further objective of this study was to analyse the time of ovulation within an Ovsynch protocol by ultrasound. Cows in the Ovsynch protocol were treated with GnRH (d 0), PGF2α (d 7) and GnRH (d 9) and bred 16 20 hrs later. Milk samples were collected three times: 7 d prior to 1st GnRH-treatment, at the 1st GnRH-injection and at PGF2α-injection. The first two milk samples were collected in 186 cows to determine stage of estrous cycle at the start of the Ovsynch protocol by milk progesterone concentration. The 3rd milk sample was collected in 218 cows to determine the presence of a corpus luteum (C.l.) at the time of PGF2α-injection. Ovaries were scanned in 138 cows via ultrasonography four times: at the second GnRH injection, at AI, as well as 26 hrs and 40 hrs after the second GnRH injection. Milk progesterone levels indicated stages of estrous cycle: 37.6% cows were around the estrus, 26.7% on the beginning of diestrous, 31.7% on the end of diestrous and 4.3% were anestrous cows. First service conception rate did not differ significantly between the different stages of cycle (37.2, 30.6, 33.9, 25.0%, resp.). Synchronization rates did not differ for the different stages of cycle (89.2, 78.8, 88.9 and 80.0%, resp.). Maximum diameter of the ovulatory follicle did not vary by the stage of estrous cycle. The overall percentage of cows ovulating during a 40 hrs period following the second injection of GnRH was 87% (synchronization rate). The percentage of follicles ovulating between 0 to 17 hrs, 17 to 26 hrs and 26 to 40 hrs was 9.4, 20.3 and 57.2%, respectively. First service conception rate did not differ significantly between the ovulation intervals (38.5%, 39.3% and 31.7 %). Maximum diameter of the ovulatory follicle was 15.6 mm without differing significantly between the ovulation intervals (16.4, 16.3 and 15.3 mm). A C.l. was demonstrated in 60.6% of cows at the time of PGF2α-injection. First service conception rate did not differ significantly between cows with and without a C.l. at PGF2α-injection (38.6% and 34.9% resp.). In conclusion, overall synchronization rate for the Ovsynch protocol was high. Conception rate did not differ between the ovulation intervals (p>0.05). The stage of estrous cycle at the initiation of an Ovsynch protocol had no significant effect on the size of the ovulatory follicle and conception rate. Abstracts – Oral presentations at 11th ICPD 197

Risk factors for postpartum endometritis and the effect of endometritis on reproductive performance in dairy cows in Korea.

The objectives of this study were to determine the risk factors for postpartum endometritis by evaluating several reproductive factors in individual cows, and to determine the effect of endometritis on the subsequent reproductive performance in dairy herds in Korea. The data, including health status, parity and body condition score (BCS) of cows, and calving date, were collected from 320 cows in eight dairy herds calving from January 2001 to October 2002. We used logistic regression to evaluate the effects of these factors on endometritis. A stepwise procedure, used to obtain the appropriate model with alpha=0.05, revealed that retained placenta, metabolic disorders and parity are the important risk factors for endometritis. The mean intervals from calving to first service and conception were prolonged (P<0.01) by 23 and 36 days, respectively, in the endometritis group compared to the non-endometritis group. The first service conception rate was lower (P<0.05) in the endometritis group (47.6%) than in the non-endometritis group (62.6%). The number of services per conception was higher (P<0.05) in the endometritis group (1.9) than in the non-endometritis group (1.6). We conclude that retained placenta, metabolic disorders and cow parity are strongly correlated with the development of postpartum endometritis, which decreases reproductive performance in dairy herds in Korea.

Reproductive performance in Ohio dairy herds in the 1990s

The objective of this study was to evaluate trends in reproductive performance in Ohio dairy herds during the 1990s. Stringent criteria for herd inclusion were applied to DHI records to ensure high quality and reliability of the data. The final data set contained 44,425 monthly herd summary records from 1772 herds from years 1992, 1994, 1996 and 1998. Outcomes of interest were calving interval length, calving-to-conception interval, days to first breeding, services per conception and first service conception rate. PROC MIXED in SAS ® (version 8.1) was used and the monthly records were treated as repeated measures nested within years and herds. First-order autoregressive covariance structure was used to model the covariance between the repeated measures within herds. The data were analyzed for the entire herd as well as for the first lactation cows separately. During the 1990s reproductive performance declined in Ohio dairy herds. Herd average calving interval lengthened from 13.6 to 14.1 months and calving-to-conception interval increased from 136 to 150 days between 1992 and 1998, respectively. Days to first service and number of services increased while first service conception rate declined on a herd level. The reproductive performance of first lactation cows, however, remained constant during this same period. Overall herd reproductive performance was associated with herd size and fat-corrected rolling herd average milk production (FCM). As milk yield increased, first service conception rate decreased and services per conception increased. Larger herds had lower first service conception rate and needed more services per conception, but they started breeding their cows earlier resulting in a slightly shorter calving interval and calving-to-conception interval compared to smaller herds.

Effects of Fishmeal Supplementation on Fertility and Plasma Ω-3 Fatty Acid Profiles in Primiparous, Lactating Beef Cows

A 2-yr study was conducted using 82 lactating, 2-yr-old, primiparous crossbred beef cows (yr 1, n = 40; yr 2, n = 42) to study the effect of fishmeal supplementation on reproductive performance. Cows were fed a corn silage-based diet supplemented with fishmeal (5% DM) or corn gluten meal (8.7% DM), beginning 25 d prior to the start of and continuing through the 90-d breeding season. Cows were artificially bred with semen from bulls of proven fertility 12h after being detected in estrus. Jugular blood samples were taken from all cows on d 3 or 4, 9 or 10, and 15 or 16 following first insemination and analyzed for serum progesterone. During yr 2 of the study, additional blood samples were collected from four cows within each treatment group immediately before supplementation began (d 0) and at 7-d intervals for the first 35 d of supplementation. Plasma samples were analyzed for Ω-3 fatty acids. Serum progesterone concentrations did not differ between treatment groups following the first insemination (P>0.76). However, first service conception rates approached significance (NS; P=0.12) and tended to be greater for cows supplemented with fishmeal when compared with cows supplemented with corn gluten meal (76% vs 62%, respectively). Overall pregnancy rates at the end of the breeding season did not differ between the two treatment groups (P>0.64). In yr 2, within 7 d of supplementation, plasma eicosapentaenoate (EPA) and docosahexaenoate (DHA) were greater for cows supplemented with fishmeal (P<0.001). In conclusion, these data indicate that fishmeal supplementation alters plasma EPA and DHA (yr 2) and may improve first service conception rates in primiparous beef cows.

Shortening of the oestrous cycle and repeated induction of heat as a method of treatment of repeat breeder cows

Abstract. Fifty-four repeat breeder cows were divided into 4 groups (GI to GIV), each one contained 14 cows with the exception of the 1st one which contained 12 cows. The oestrous cycle was shortened in cows of GI and GII by means of injection of 0.5 mg of cloprostenol in GI on day 10 of the cycle and by single intra-uterine infusion of 100–150 ml of Lugol's Iodine from day 3 to 5 of metoestrous in cows of GII. Cows in GIII were infused by Norofloxacin on day 1 to 3 of the 1st and 2nd cycle only. Cows in group IV were left as non-treated affected control and just rested for 3 successive cycles. Insemination was performed at the 3rd induced heat in cows of GI, after 3 cycles (2 shortened and one with normal length) in cows of GII and after 3 cycles with normal length in cows of both GIII and GIV. The post-treatment conception rates were determined. There were significant differences (P &lt; 0.005) in the total and first service conception rates between cows in GI and GIII compared with that of those in GIV and GII. Also, there was a significant difference (P &lt; 0.001) for C.R. between cows in GII and those in GIV. From the results of this study, it could be concluded that shortening of oestrous cycle and repeated induction of heats using PGF2 α analogue (cloprostenol) is better than i.u. infusion of antibiotic together with sexual rest for treatment of repeat breeder cows.

Effects of Feeding Complexed Zinc, Manganese, Copper, and Cobalt to Late Gestation and Lactating Dairy Cows on Claw Integrity, Reproduction, and Lactation Performance

Three hundred multiparous Holstein cows (150 cows per treatment) were blocked according to calving date and randomly assigned to a study to determine the effect of trace mineral source on incidence and severity of claw lesions, reproduction, and lactation performance of dairy cattle. Treatments were 1) all trace minerals supplied by sulfates(ITM)or 2) 360mg Zn from Zn amino acid complex, 200mg Mn from Mn amino acid complex, 125mg Cu from Cu amino acid complex, and 12mg Co from Co glucoheptonate per day(CTM;Availa®; Zinpro Corporation, Eden Prairie, MN) replacing an equivalent amount of Zn, Mn, Cu, and Co from sulfates. Cows received assigned treatments from 21 d prior to calving through 250 d of lactation. Cows fed CTM produced 1.2kg more (P < 0.05) milk, energy-corrected milk, and 3.5% fat-corrected milk than cows supplemented with ITM. The CTM treatment reduced (P < 0.05) days open by 22 d and tended to increase (P < 0.15) percentage of cows pregnant by 150 d in milk (54.8% vs 42.7%) and first service conception rate (27.4% vs 18.4%). Cows fed CTM tended to have a lesser incidence (P < 0.15) of claw disorders than cows fed inorganic trace minerals at 75 d postpartum (23.6% vs 34.1%) and numerically lower incidence at 250 d postpartum (10.0% vs 17.7%). The CTM treatment increased yield of milk, decreased days open, and tended to increase first service conception rates, increase percentage of cows pregnant at 150 d in milk, and decrease claw disorders at 75 d postpartum.

Fertility responses and hormonal profiles in repeat breeding cows treated with insulin

The influence of insulin treatment on conception rate and endocrine profile was studied on 21 repeat breeding cows divided randomly into two groups, i.e. insulin treatment ( n=11) and control ( n=10). Cows of the insulin treatment group were injected subcutaneously with a long acting purified form of bovine insulin at 0.2 IU/kg body weight/day on days 8, 9 and 10, and then with 0.75 mg tiaprost (PGF 2α) intramuscularly on day 12 of the oestrous cycle (oestrus = day 0). The cows of the control group only received 0.75 mg tiaprost was injected intramuscularly on day 12. There was no difference ( P>0.05) in the interval to the onset of oestrus and subsequent cycle length between the treatment (84.5±6.6 h and 21.2±0.6 days, respectively) and the control (72.3±5.9 h and 19.7±0.4 days, respectively) groups. First service conception rate and overall pregnancy rate did not differ ( P>0.05) between the insulin treatment group (45.4 and 63.6%) and the control group (33.3 and 40.0%). Progesterone concentration following administration of insulin increased ( P<0.05) in the insulin treated cows (2.2±0.4 ng/ml versus 2.9±0.4 ng/ml) but the concentration of oestradiol-17β did not differ. The insulin concentration was higher on day 10 of the oestrous cycle ( P<0.05) in the treatment group (71.0±12.5 μU/ml versus 38.1±4.5 μU/ml). The insulin and glucose concentrations were higher ( P>0.05) in animals, which subsequently became pregnant than in non-pregnant animals. The results may indicate that there is beneficial effect of insulin on fertility in repeat breeder cattle.

Improvement of reproductive performance in crossbred zebu anestrous primiparous cows by treatment with norgestomet implants or 96 h calf removal

The aim of the present study was to compare the effect of norgestomet implants (NI) and calf removal (CR) for 96 h on estrus induction and first service fertility in crossbred zebu primiparous anestrous cows after 120 days postpartum. A total of 152 cows in a tropical environment were allotted to three experimental groups: CR for 96 h ( n=51), NI for 9 days plus 500 IU of PMSG at implant removal ( n=51) and a control group (CG) without treatment ( n=50). Estrous rate (%) and mean interval to first estrus (days) were 50.9 and 26.3±6.8; 60.7 and 13.8±6.8; 16.0% and 61.8±5.9 days for groups CR, NI and CG, respectively. CR and NI were statistically similar, however, both groups were different ( P<0.01) when compared with CG. Calving interval to first service and to conception were: CR: 151.2±8.4 and 157.8±21.4; NI: 145.2±8.5 and 150.9±21.3; CG: 186.8±7.3 and 201.0±18.5. A difference ( P<0.01) was found in both intervals when comparing the CR and NI with CG, with longer intervals for cows in the CG group. First service conception rates were 61.5, 67.7 and 62.5% for groups CR, NI and CG, respectively, and were not different ( P>0.05). These results demonstrate the efficacy of NI+PMSG or temporary CR for 96 h in inducing a fertile estrus and shortening the interval to estrus and to conception in primiparous crossbred anestrous zebu cows in the tropics.

Performance of dairy heifers fed high forage diets supplemented with bambermycins, lasalocid or monesin (2002)

One hundred and twenty Holstein heifers weighing approximately 450 lb at the beginning of the study were used to evaluate the impact of bambermycins (Gainpro®), monensin (Rumensin®), and lasalocid (Bovatec®) on performance when included in high forage diets fed ad libitum. Heifers were housed in 24 pens (5 hf/pen) containing a super hutch. Pens were blocked (3 pens/block) from heaviest to lightest and randomly assigned within blocks to bambermycins, lasalocid, or monensin treatment. Bambermycins, lasalocid, and monensin were mixed with fine ground corn and fed as topdressing to deliver 20.25, 150, and 150 mg/hd daily, respectively. Diets were formulated (NRC 2001) to support body weight gains of less than 2 lb/hd daily using a mix of chopped alfalfa hay and corn silage (lighter weight heifers) or chopped alfalfa hay, chopped prairie hay, and corn silage (heavier weight heifers) supplemented with a mineral/vitamin premix. All heifers were fed a common total mixed ration, differing only in topdressing. Diets were fed once daily for ad libitum intake. The study continued until the average bodyweight exceeded 800 lbs. (140 days on study) at which time they were inseminated and first service conception rate determined. Heifers fed monensin consumed less dry matter (DMI) (P<0.05) than those fed bambermycins and lasalocid during the periods d 29 to 56, 57 to 84, and 113 to 140 but DMI was similar across treatments during the 140- day study. No differences were observed for ADG over the 140-d study but heifers fed bambermycins and monensin tended (P=0.06) to gain faster during days 85 to 112 than heifers fed lasalocid. Feed efficiency (gain/feed) varied, but heifers consuming diets containing bambermycins and monensin were more efficient (P<0.05) during days 85 to 112 and tended to be more efficient (P=0.051) during the 140- day study than heifers consuming lasalocid. Bodyweight, condition score, and hip height were similarly influenced by dietary treatments. First service conception rates were 60, 47 and 55% for heifers fed bambermycins, lasalocid, and monensin, respectively.; Dairy Day, 2002, Kansas State University, Manhattan, KS, 2002

Factors Leading to Endometritis in Dairy Cows in Egypt with Special Reference to Reproductive Performance.

The incidence of endometritis and risk factors between herds and between breeds and its effect on the subsequent fertility of cows may differ among countries. It is therefore necessary to study the etiology of endometritis in these different circumstances. This work was carried out on 190 Holstein Friesian cows (2.5-13 years old) belonging to El-Salhia Agriculture project (Ismailia Province, Egypt) during the period from January 1996 to April 1997. The incidence of endometritis was 22.4%, and the most prominent risk factors leading to the occurrence of endometritis were retained placenta, stillbirth, external interference by herdmen during calving and difficult birth (20.6, 19.1, 12.3 and 5.3% respectively). The cows in the first parity had a higher incidence of endometritis (27.7%) than cows in the subsequent parities. Cows which calved in autumn (31.2%) had a higher incidence of endometritis than cows which calved in the other seasons. The endometritic cows had inferior reproductive indices than the normal cows. The interval between calving and first service in cows with endometritis was 14 days longer than the normal ones. The first service conception rate (12.5%) and final conception rate (45.5%) in cows with endometritis were lower than those in the normal cows (50 and 100%) (P<0.05 ). In conclusion the most important risk factors leading to endometritis are retained placenta and abnormal calving in dairy cows in Egypt. Moreover, postpartum endometritis adversely affects subsequent fertility in dairy cows in Egypt.

Reproductive function in average and high yielding dairy cows

AbstractThe resumption of reproductive activity in the early post partum period and the subsequent fertility of dairy cows are of considerable practical and economic importance to the producer. Regular milk progesterone analysis was used in this study to monitor the re-establishment of reproductive cyclicity in animals of average (AGM, n=20) and high genetic merit (HGM, n=28) kept under standard management conditions. The profiles obtained were then characterised into normal and four different types of abnormal activity. Resumption of cycles occurred significantly later in the higher yielding cows than in those of average genetic merit (23 ±2.3 days in HGM cows and 15 ± 1.6 days in AGM cows; P=0.0089). There was a significant increase in the amount of abnormal cycles encountered in the high genetic merit animals compared with average yielding animals (61% and 30% respectively; χ2 test, P=0.045); in particular, the delayed occurrence of ovulation post partum (11% vs 0%) and an increased incidence of persistent corpora lutea (32% vs 20%). For high genetic merit animals, the incidence of abnormal cycles was associated with increased peak milkyields (abnormal cycles: peak milk yield 54.7 ± 1.11 kg/day; normal cycles: peak milk yield 46.4 ± 1.35 kg/day, P=0.002). This relationship was not apparent in average genetic merit animals. First service conception rates were 50% (9/18) for AGM cows and 38% (10/26) for HGM cows (χ2 test, n.s.). The calving to conception interval was 98 ± 9.7 days for AGM animals (n=l7) and 105 ± 9.1 days for HGMs (n=24) (t-test, n.s.). In conclusion, this study confirms that high genetic merit dairy cows have compromised reproductive function in terms of a delayed resumption of cyclicity and an increased incidence of abnormal progesterone cycles, which was associated with higher peak milk yields. There was also a reduced first service conception rate in high yielders although the difference was not significant with this group size.

Relationship between genetic merit, milk production, body condition, blood parameters and reproductive performance of dairy cows

AbstractBased on their pedigree indices for milk production traits, 48 high (HM) and 48 medium (MM) genetic merit cows were studied in each of two years to determine the possible relationships between genetic merit, milk production, body condition, metabolite and hormone concentrations, feed intake and reproductive performance. The high genetic merit cows had higher milk production, greater body condition loss between calving and first service, lower plasma glucose and insulin-like growth factor-1 (IGF-1) and lower first and second service conception rates than the medium genetic merit cows. Furthermore, more high genetic merit cows were not pregnant at the end of the breeding period compared with medium genetic merit cows. Cows that did not conceive to first service were retrospectively compared to those that conceived to first service within each genetic merit category. Within the high and medium genetic merit category there were no significant differences between the cows that did not conceive and those that conceived to first service in terms of milk production, or plasma concentrations of glucose, non-esterified fatty acids (NEFA). Although medium genetic merit cows that did not conceive to first service lost more body condition score between calving and first service than those that conceived to first service, there was no difference in body condition score (BCS) change between calving and first service between high genetic merit cows that did not conceive and those that conceived to first service. In the present study, high genetic merit cows had higher milk production and reduced reproductive performance in comparison with medium genetic merit cows. However, reproductive performance was not associated with milk production, energy balance or plasma concentrations of glucose, NEFA or IGF-1 between calving and insemination