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.

Comparison of the 7-day CO-Synch and 8-day estradiol-based protocols for estrus synchronization and timed artificial insemination in suckled Bos taurus cows.

Two experiments were conducted to compare, follicle diameter (FD) on Day -1, corpus luteum (CL) area on Day 7, progesterone (P4) concentration on Day 7 and 18, pregnancy per timed artificial insemination (TAI) on Day 30, and pregnancy loss (PL) between Days 30 and 60 after TAI (TAI, Day 0) using two different synchronization protocols. In Experiment 1, Angus cows (n = 1148) were randomly assigned to either 7-d progesterone CO-Synch (7-d CO-Synch) or 8-d progesterone + estradiol (8-d P + ES) synchronization protocols for TAI. On Day -10, cows in the 7-d CO-Synch treatment group (n = 574) received a progesterone-releasing intravaginal device (PIVD; 0.5 g P4) and GnRH (0.105 mg), on Day -3 the PIVD was removed and cows received cloprostenol (0.150 mg), then, on Day 0 (64 h after PIVD removal), cows received GnRH (0.105 mg) and were TAI. On Day -10, cows in the 8-d P + ES treatment group (n = 574) received a PIVD (0.5 g P4) and estradiol benzoate (2.0 mg), on Day -2 the PIVD was removed, and cows received cloprostenol (0.150 mg) and estradiol cypionate (0.5 mg), then, on Day 0 (48 h after PIVD removal), cows were TAI. Pregnancy per TAI was determined on Days 30 and 60. In a subset of cows (7-d CO-Synch, n = 41; 8-d P + ES, n = 40), serum P4 concentration was evaluated on Day 18. In Experiment 2, anestrus (n = 34) and cyclic (n = 34) suckled beef cows were selected and submitted at random on Day -10, to either 7-d CO-Synch or 8-d P + ES treatment groups. Follicle diameter on Day -1, CL area, and serum P4 concentration on Day 7 were determined. In Experiment 1, pregnancy per TAI on Day 30 did not differ (7-d CO-Synch = 48.9%; 8-d P + ES = 45.6%) between treatments but it was greater for cows with BCS ≥5 (P < 0.01). Pregnancy loss between Days 30 and 60 did not differ between treatment groups but tended to be greater in cows with BCS <5.0 (P < 0.1). In a subset of cows, serum P4 concentration on Day 18 did not differ between treatment groups but tended to be lower (P < 0.1) in cows that had PL between Days 30 and 60 compared to cows that had no PL. In Experiment 2, FD tended to be greater (P < 0.1) and CL area was greater (P = 0.05) in anestrus cows from 7-d CO-Synch treatment. In cyclic cows, the treatment did not affect the FD or CL area. In conclusion, there was no difference in pregnancy per TAI on Day 30 and PL between Days 30 and 60 between cows using 7-d CO-Synch + PIVD or 8-d estradiol-based + PIVD protocols for estrus synchronization and TAI.

Age at First Gestation in Beef Heifers Affects Fetal and Postnatal Growth, Glucose Metabolism and IGF1 Concentration.

This study aimed to determine the effects of age at first gestation on offspring growth performance, glucose metabolism, and IGF1 concentration. Heifers impregnated by AI from a single bull at 15 months of age (15 M, n = 20), or 27 months of age (27 M, n = 20), and multiparous cows (adult, n = 20) were used. Dams from all groups were managed in a single group during gestation and lactation. Gestational length was longer in the 15 M and 27 M than in adult dams (p = 0.009). Bodyweight at birth, at weaning and ADG during lactation were higher in calves from adult dams than in those from 27 M dams, and higher in calves from the latter than in 15 M calves (p < 0.001). Calves from 15 M dams had an increased head circumference/BW ratio compared to calves from 27 M dams, while calves from this latter group had an increased ratio compared to calves from adults (p = 0.005). Body mass index was greater in calves from adults than in those from 15 M and 27 M dams (p = 0.002). Milk production from 15 M and 27 M dams was similar but lower than that from adults (p = 0.03). Calves born from adult dams had greater blood glucose concentrations than those from 15 M and 27 M dams (p < 0.05). Serum IGF1 concentrations were higher in calves from adults than in calves from 15 M and 27 M dams (p = 0.01). This study showed that age at first gestation affects offspring postnatal growth performance, glucose metabolism and IGF1 concentration.

Effects of inorganic copper injection in beef cows at late gestation on fetal and postnatal growth, hematology and immune function of their progeny.

To determine if Cu injection during late gestation can affect fetal and postnatal growth, hematology and immune function of progeny, 70 multiparous pregnant Angus cows, at 219 ± 15 d of gestation, were ranked by BW and BCS and randomly assigned to one of two treatments: Cu + (n = 35) in total 160 mg of Cu were administered subcutaneously in two moments (80 mg per moment) at 64 ± 15 d and 54 ± 15 d prepartum; and Cu- (n = 35), in total of 16 ml of sterile NaCl solution (9 g / l) were administered subcutaneously in two moments (8 ml per moment) at 64 ± 15 d and 54 ± 15 d prepartum. Calves from both treatments were weaned at 260 ± 15 d of age, male calves were separated from female calves and stockered on natural pastures until 690 ± 15 d of age, then placed into a feedlot for 104 d before slaughter. At the beginning of the experiment, cows Cu serum concentration was similar (P = 0.34) between treatments and these reflected a severe Cu deficiency (Cu + = 24.2 ± 1.5 µg/dl; Cu- = 22.2 ± 1.4 µg/dl). At calving, Cu serum concentration was greater (P < 0.01) in Cu + cows than Cu- cows. Copper serum concentration in calves from Cu + cows was greater at birth (P = 0.02) and 75 ± 15 d of age (P < 0.01) and tended (P = 0.07) to be greater at 160 ± 15 d of age compared to calves from Cu- cows. Calf BW at birth did not differ (P > 0.10) between treatments, however, calf BW adjusted at 75 d of age tended to be greater (P = 0.10) in calves from Cu + cows compared to calves from Cu- cows. Calf ADG from birth to 75 d of age was greater (P = 0.04) in calves from Cu + cows compared to calves from Cu- cows. Calf hematological parameters and titers of neutralizing antibodies against BHV-1 after primary and secondary vaccination against respiratory diseases did not differ (P > 0.10) between treatments. During finishing period, steers BW, 12th rib fat thickness and LM area were not affected (P > 0.10) by treatments. In summary, inorganic Cu injection during late gestation in Cu deficient beef cows allows to increase Cu serum concentration in calves from birth to 160 d of age. This event was associated with an increase in ADG and a tendency to increase BW during the first 75 days of life. After 75 days of age, any effect on the offspring performance was not observed.

Effects of inorganic selenium injection on the performance of beef cows and their subsequent calves.

Sixty-seven pregnant Angus cows and their subsequent calves were used in a randomized design to evaluate the effect of inorganic Se injection from 80 d of gestation until weaning on cow reproductive parameters, BW and BCS evolution, milk yield and quality, calf growth and calf hematology parameters. The treatments were as follows: 1) Se+: cows were administered Se as sodium selenite at doses of 0.05 mg/Kg of BW at 80, 140, 200, 260 d of gestation and 30, 90, 150 and 240 d of lactation. Calves from Se + cows were Se as sodium selenite subcutaneously injected with a dose of 0.05 mg/Kg of BW at 70, 104, 144 d of age; 2) Control: cows and calves were administered sterile NaCl solution (9 g/l) at the same volume and intervals as Se + treatment. At the start of the experiment, forage Se concentration was 58.6 ppb ±â€¯7.6 ppb, and cow whole blood Se concentration was similar (P > 0.10) between treatments (Se+, 29.3 ±â€¯0.3 ppb; Control, 28.1 ±â€¯0.5 ppb). After Se injection, cow whole blood Se concentration was increased (P < 0.01) in Se + cows in relation to control cows until the end of the experiment. Calf whole blood Se concentration was increased (P < 0.01) at birth and 30 d of age in calves from Se + cows compared to calves from Control cows. However, calf whole blood Se concentration was not different (P > 0.10) between treatments at d 70 after birth. After the first Se injection (70 d of age), calf whole blood Se concentration was increased (P < 0.01) at 104 and 144 d of age in calves from Se + cows compared to calves from Control cows. Cow BW and BCS did not differ (P > 0.10) between treatments throughout the experiment. Ovarian follicle diameter measured by ultrasound 47 d postpartum was greater (P = 0.03) in Se + cows compared to Control cows. Pregnancy rate to fixed time artificial insemination (FTAI), overall pregnancy rate (P > 0.10) and pregnancy loss (P = 0.19) did not differ between groups. Selenium injection did not affect (P > 0.10) milk yield and composition. Calf morphometric parameters, BW at birth and growth rate during lactation were not affected (P > 0.10) by treatments. No significant effect (P > 0.10) was observed between treatments on hematological results of blood samples from calves at weaning. Results of this study shown that inorganic Se injection was an efficient tool to improve Se-status in cow-calf operation under extensive management. Selenium injection increased follicle diameter in postpartum beef cow, however, did not affect the rest of the variables studied.

Maternal energy status during late gestation: Effects on growth performance, carcass characteristics and meat quality of steers progeny.

The objetive of the current study was to determine the effect of maternal energy status during late gestation on growth performance, carcass characteristics and meat quality of steer progeny. At 180 ±â€¯4 d of gestation 56 multiparous Angus cows were blocked by BW and expected calving date and asigned to three levels of nutrition energy: SR (severe restricted; 50% of NRC requirement), MR (moderate restricted; 75% of requirement) and NR (no restricted; 100% of requirement). After parturition, all cows were managed in a single group during lactation. A total of 25 male calves (SR = 8 calves; MR = 9 calves; NR = 8 calves) were born from pregnant cows and all pens had at least one male calf. After weaning, male calves were separated of female calves and were stockered on native range until 24 ±â€¯0.1 months of age then placed into a feedlot for 104 d before harvest. Cow BW and BCS decreased linearly (P < .01) as nutritional energy restriction increased. Calves from SR dams were lighter (P = .04) than calves from MR and NR dams at parturition, however, at weaning and harvest BW was similar for SR and NR steers and decreased in MR steers. Steers from SR dams demonstrated catch-up growth with a tendecy to increased ADG from birth to harvest compared to MR and NR steers (P = .06). Hot carcass weigth was similar in SR and NR steers and increased in MR steers (P = .01). Longissimus muscle area was not affected (P > .10) by maternal energy status, however, 12 rib fat thickness was greater in SR and MR compared to NR steers (P < .01). Tenderness of Longissimus muscle was decreased in MR compared to SR and NR steers after 3d of aging. No treatment differences (P > .10) were observed in sarchomere length or collagen content. Adipocyte diameter was similar (P > .10) between treatments suggesting that decreased 12th rib fat thicness in MR steers could be due to decreased fat tissue hyperplasia. These results indicate that level of energy restriction during late gestation does no have linear response on growth performance and carcass quality of steers progeny.

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.