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.

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.

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.