Repeat breeding is a serious reproductive disorder in dairy cattle. The causes of repeat breeding are multifactorial and there are two main mechanisms: failure of fertilisation or early embryo death, mainly due to poor quality of oocytes and an inadequate uterine environment. Many methods have been used to increase the pregnancy rate for repeat breeder cows, such as intrauterine infusion of antibacterial agents or antibiotics, hormonal treatments for oestrus synchronisation and induction of ovulation, and progesterone supplementation or induction of accessory corpus luteum; however, the results were inconsistent between studies. Embryo transfer (ET) has the capability to minimalise the effects of poor oocyte quality and unfavourable uterine environments on early embryo development during the first seven days after ovulation in repeat breeder cows, and several studies showed that ET significantly improved the pregnancy rate in this group of animals. Thus, ET can be considered an option to increase the conception rate in repeat breeder dairy cows.

Albendazole, administered orally at a dose rate of 25 mg/kg of body weight to presumed pregnant cows or heifers on days 21, 31, 41, 51, and 61 of gestation, did not induce toxicosis in embryos or fetuses, and all calves born were structurally normal. Albendazole administration at a rate of 25 mg/kg to cows at 7 and/or 14 days of gestation decreased the apparent conception rate (ie, embryolethality), but did not have a teratogenic effect. Apparent embryolethality was greater in cows administered 25 mg/ kg only on day 14, compared with those administered the drug only on day 7. Single dosage of 25 mg/kg given in the final 3 months of gestation did not induce abortion. There were no adverse effects of albendazole at a dosage of 10 or 15 mg/kg on developing embryos or fetuses when administered to presumed pregnant cows at various times in early gestation.

Administration of progesterone in poly(d-,l-lactide) microspheres was used to maintain pregnancy in mares after luteolysis was induced by treatment with pros F2 alpha at day 14 of pregnancy. Mares were given vehicle only (control, n = 6) or 0.75 g (n = 7), 1.5 g (n = 8), or 2.25 g (n = 5) of microencapsulated progesterone at days 12 and 22 of pregnancy. Serum progesterone concentrations were determined daily, and pregnancy was evaluated by transrectal ultrasonography on alternate days. Significantly (P < 0.05) more mares given 1.5 or 2.25 g of progesterone (6 of 8 and 4 of 5 mares, respectively), but not those given 0.75 g (3 of 7 mares), maintained pregnancy through day 32, compared with control mares (O of 6). Progesterone concentrations decreased significantly (P < 0.025) in all groups after administration of prostaglandin F2 alpha at day 14, and significant (P < 0.05) effects of time and treatment on progesterone concentrations were found between days 12 and 22, and 22 and 32. Although treatment with 1.5-g and 2.25-g doses of microencapsulated progesterone improved maintenance of pregnancy, compared with that of vehicle-treated controls, administration of 2.25 g of microencapsulated progesterone appeared to be most efficacious in maintenance of pregnancy during the study interval.

The role of decreased luteal activity in embryonic loss after induced endotoxemia was studied in mares 21 to 35 days pregnant. Fourteen pregnant mares were treated daily with 44 mg of altrenogest to compensate for the loss of endogenous progesterone secretion caused by prostaglandin F2 alpha, (PGF2 alpha) synthesis and release following intravenous administration of Salmonella typhimurium endotoxin. Altrenogest was administered daily from the day of endotoxin injection until day 40 of gestation (group 1; n = 7), until day 70 (group 2; n = 5), or until day 50 (group 3; n = 2). In all mares, secretion of PGF2 alpha, as determined by the plasma 15-keto-13,14-dihydro-PGF2 alpha concentrations, followed a biphasic pattern, with an initial peak at 30 minutes followed by a second, larger peak at 105 minutes after endotoxin injection. Plasma progesterone concentrations decreased in all mares to values < 1 ng/ml within 24 hours after endotoxin injection. In group 1, progesterone concentrations for all mares were < 1 ng/ml until the final day of altrenogest treatment. In 6 of 7 mares in group 1, the fetuses died within 4 days after the end of treatment, with progesterone concentrations < than 1 ng/ml at that time. In the mare that remained pregnant after the end of treatment, plasma progesterone concentration was 1.6 ng/ml on day 41 and increased to 4.4 ng/ml on day 44. In group 2, all mares remained pregnant, even though plasma progesterone concentrations were < 1 ng/ml in 4 of 5 mares from the day after endotoxin injection until after the end of altrenogest treatment. One group-2 mare appeared to develop a secondary corpus luteum before day 70, with progesterone concentrations greater than 1 ng/ml from day 36 through day 70. Daily altrenogest administration consistently prevented pregnancy loss, which usually follows induced endotoxemia. Altrenogest administration offers a reliable and practical treatment for the prevention of fetal loss following endotoxemia in mares < 2 months pregnant. One group-3 mare remained pregnant, and in the other mare, fetal death was diagnosed 8 days after endotoxin administration, although this mare was still being treated with altrenogest. In that case fetal death was believed to be unrelated to the treatment.

The role of prostaglandin F2 alpha (PGF2 alpha) in embryonic loss following induced endotoxemia was studied in mares that were 21 to 44 days pregnant. Thirteen pregnant mares were treated with a nonsteroidal anti-inflammatory drug, flunixin meglumine, to inhibit the synthesis of PGF2 alpha caused by Salmonella typhimurium endotoxin given IV. Flunixin meglumine was administered either before injection of the endotoxin (group 1, -10 min; n = 7), or after endotoxin injection into the mares (group 2, 1 hour, n = 3; group 3, 2 hours, n = 3); 12 pregnant mares (group 4) were given only S typhimurium endotoxin. In group 4, the secretion of PGF2 alpha, as determined by plasma 15-keto-13,14-dihydro-PGF2 alpha concentrations, was biphasic, initially peaking at 30 minutes followed by a second, larger peak approximately 105 minutes after the endotoxin was given IV. When flunixin meglumine was administered at -10 minutes, synthesis of PGF2 alpha was inhibited for several hours, after administration of flunixin meglumine at 1 hour, the second secretory surge of PGF2 alpha was blocked, and administration of the drug at 2 hours did not substantially modify the secretion of PGF2 alpha. Plasma progesterone concentrations were unchanged after endotoxin injections were given in group 1. In group 2, progesterone values decreased < 2 ng/ml and remained low for several days. In group 3 and group 4, progesterone concentrations decreased to values < 0.5 ng/ml by 48 hours after endotoxin injections were given. Pregnancy continued in all 7 mares in group 1; in group 2, pregnancy continued in 2 of 3 mares; and in group 3, none of the 3 mares was pregnant by 4 days after endotoxin administration. The abortifacient effect of endotoxemia in mares < 2 months pregnant is mediated indirectly through the secretion of PGF2 alpha; compromised luteal activity and inadequate progesterone secretion are the primary causes of fetal death. Although flunixin meglumine administration can be used to prevent loss of pregnancy in cases of endotoxemia, it must be initiated at an early stage of the endotoxemia, that is, when clinical signs are often not yet apparent.

Ultrasonography was used to determine whether there is embryo reduction in mares iwth unilaterally fixed twins when a major portion of the vascularized area of the wall of one of the embryonic vesicles is in apposition with the wall of the adjacent vesicle, rather than with the endometrium (deprivation hypothesis). In addition, the effect of ovulatory pattern (synchronous and asynchronous) on the incidence of embryo reduction was studied. Twin vesicles were ultrasonically detected on days 11 to 15 (ovulation = day 0) and were examined daily until there was embryo reduction or until day 40. In 31 mares with twin embryonic vesicles, unilateral fixation (71%) was more frequent (P less than 0.05) than was bilateral fixation (29%). In 28 mares with known ovulatory patterns, synchronous ovulations did not affect the type of fixation (9/17 unilateral and 8/17 bilateral); however, for asynchronous ovulators the frequency of unilateral fixation (10/11) was greater (P less than 0.01) than the frequency of bilateral fixation (1/11). The incidence of embryo reduction was greater (P less than 0.01) for unilateral fixation (14/19) than for bilateral fixation (0/9) and was greater (P less than 0.05) for asynchronous ovulators (9/11) than for synchronous ovulators (5/17). In mares with embryo reduction, the reduction was complete before detection of both embryo propers (early reduction) in 10/14 and after detection of both embryo propers (late reduction) in 4/14. For 17 synchronous ovulators, fewer underwent early embryo reduction (0 mares) than late reduction (5 mares) or no reduction (12 mares; 4 unilateral and 8 bilateral), whereas in the 11 asynchronous ovulators, more underwent early reduction (8 mares) than late reduction (1 mare) or no reduction (2 mares; 1 unilateral and 1 bilateral; P less than 0.01). In mares with early embryo reduction, the orientation and spatial relationship of one vesicle relative to the other was not determinable until the embryo proper was detected. In the 2 mares in which the embryo proper of the survivor was detected before embryo reduction was complete, the embryo proper was located opposite to the site of reduction, ie, the vesicle that was to be eliminated impinged on the thin-walled area of the yolk sac wall of the survivor. The position of the embryo proper and its emerging allantoic sac seemed to determine whether a given conceptus survived or underwent late embryo reduction. The embryo proper, the vascularized wall of the yolk sac adjacent to the embryo proper, and the emerging allantoic sac were exposed to the endometrium (uterine lumen) in the surviving vesicles; in the vesicles that underwent reduction, much of the corresponding area of the vesicle wall was covered by the wall of the adjacent survivor. The results supported the deprivation hypothesis.

A study was conducted to evaluate the effects of feeding processed kidney bean meal (PKBM) by replacing soybean meal (SBM) on fertility, hatchability, embryonic mortality and chick quality of white leghorn (WL) hens. A total of 225 white leghorn hens (195 layers and 30 cocks) with uniform body weight (BW) and age were randomly distributed into 15 pens and assigned to five treatments (i.e., T1, T2, T3, T4, and T5). A total of 360 eggs collected from all the treatment birds were used for the analysis. The feeds of the treatments were SBM substituted by PKBM at 0, 25, 50, 75 and 100% levels for T1, T2, T3, T4, and T5, respectively. Replacement of SBM with PKBM in the diet did not affect the fertility, hatchability, embryonic mortality, chick length, chick weight, and chick quality by visual score. As no difference is observed, 100% replacement of SBM by PKBM (dosed at 100 g/kg concentrate diet) is possible.