Effect of an equine chorionic gonadotrophin-like recombinant glycoprotein treatment on fertility in Angus cattle.

This study determined the effects of administering a glycoprotein with equine chorionic gonadotropin (eCG)-like activity (eCG-like) on corpus luteum (CL) area, serum progesterone concentrations, incidence of multiple ovulations (MOV), estrus expression rate (EER), and pregnancy to timed AI (P/TAI) in Angus cattle synchronized with a 5-d Co-Synch protocol. On Day -8, cattle were body condition scored (BCS), and received a 1.0 g progesterone intravaginal device (IVD) and 100 µg GnRH. On Day -3, the IVDs were removed and 500 µg cloprostenol was administered intramuscularly (i.m.). Cattle were randomly assigned into one of two groups: eCG-like (heifers, n = 232, primiparous, n = 148, and multiparous cows = 485; 300 IU (heifers) and 400 IU (cows) eCG-like i.m. on Day -3), or Control (heifers, n = 240, primiparous, n = 151, and multiparous cows, n = 478; no eCG-like). On Day -2, cattle received a second dose of 500 µg cloprostenol, and on Day 0, 100 µg GnRH was given concurrently with TAI. Estrus expression rate was assessed by observing the tail paint rubbed off in a subset of heifers (n = 372) and all cows on Day 0. Transrectal ultrasonography was used to evaluate the presence of CL on Day -8 and to diagnose P/TAI on Day 30-35. In a subset of cattle (heifers = 194 and multiparous cows = 87), CL area, serum progesterone concentrations, and incidence of MOV were evaluated on Day 7. Heifers, primiparous, and multiparous cows were analyzed separately. Treatment with eCG-like did not affect (P > 0.1) EER in heifers. Estrus expression rate was increased (P ≤ 0.03) in primiparous (68.9 % vs 45.0 %) and multiparous (75.5 % vs. 68.8 %) cows treated with eCG-like compared with Controls. Pregnancy/TAI was increased (P < 0.01) in heifers (65.2 % vs 48.3 %) and primiparous cows (48.3 % vs. 35.1 %) treated with eCG-like than Controls. In multiparous cows with a BCS ≤4 P/TAI was increased (P = 0.03) in the eCG-like group (47.7 %) than the Control group (34.8 %) but was similar (P > 0.1) between treatment groups in multiparous cows with a BCS ≥4.5. The eCG-like treatment increased (P < 0.05) CL area in heifers and multiparous cows and tended (P = 0.10) to elevate serum progesterone concentrations only in heifers. However, it did not affect (P > 0.1) the incidence of MOV in heifers and multiparous cows. Glycoprotein eCG-like administration increased fertility in heifers and primiparous cows, but in multiparous the effect of eCG-like on fertility was associated with BCS.

Development and growth of bovine calves demi-embryos.

The aim of this study was to investigate the growth and development of animals produced from demi-embryos and compare them with whole embryos from fetus to adult life. To achieve this, calves produced from fresh demi-embryos and whole embryos were individually transferred and monitored from 60 days of pregnancy until slaughter at 550 days. Ultrasound scans were conducted on fetuses at 60 and 90 days to evaluate the biparietal, abdominal, umbilical cord, orbital, and aorta diameters. Subsequently, morphological traits of newborn calves were measured at 0, 7, and 21 days (N = 18). Live weight was recorded at birth, weaning, and every 30 days thereafter until slaughter at 550 days. The growth curve of each group was modeled using logistic regression, and the factors of the respective functions were compared. As early as 60 days of pregnancy, ultrasound evaluations revealed no morphometric differences between fetuses produced from demi-embryos and those from whole embryos. This lack of differentiation persisted in the morphometric evaluations of newborns up to 21 days of age, as well as in live weight and the growth curve from birth to slaughter. Moreover, there were no significant differences between the groups in terms of rib eye area and fat thickness evolution. Consequently, individuals from demi-embryos exhibited no discernible disparities to those whole embryos in growth and development from 60 days of gestation, through birth, and into adulthood.

Effects of cytoplasmic inheritance on preweaning traits of Hereford cattle

The influence of cytoplasmic inheritance on birth and weaning weight was evaluated in an experimental Hereford herd. Data on 1,720 records for birth and weaning weights from calves born between 1963 and 2002 were studied. Variance components were estimated using MTDFREML procedures and an animal model was fitted for each trait. Direct and maternal additive effects and permanent environment and maternal lineage effects were treated as random, while year and month of birth, age of dam and sex of the calf were treated as fixed. Identification of maternal lineages was based on pedigree information. The contribution to phenotypic variance of cytoplasmic lineages defined by pedigree information was negligible for both traits. Mitochondrial genotypes of cows present in the herd in 2002 were analyzed by single strand conformation polymorphism (SSCP) analysis. Only five different genotypes were identified among 23 maternal lineages. All the animals with records were assigned to maternal genotypes based on pedigree information. The statistical analysis was repeated, removing maternal lineage from the model and including mitochondrial genotype as a fixed effect. No evidence of genotype effects was detected. These results suggest a negligible effect of the mitochondrial genome on the preweaning traits of this Hereford herd.