Effects of sire and dam on late-pregnancy conceptus and hormone traits in beef cattle

Intermediate metabolites and molecular correlates of one‑carbon and nutrient metabolism differ in tissues from Holstein fetuses

Methionine and folate cycles along with transsulfuration comprise the one‑carbon metabolism (OCM) pathway. Amino acids and other nutrients feed into OCM, which is central to cellular function. mRNA abundance, proteins (Western blotting), and metabolites (GC-MC) associated with OCM were used to characterize these mechanisms in fetal tissues. Liver, whole intestine, and semitendinosus muscle were harvested from fetuses in 6 multiparous Holstein cows (37 kg milk/d, 100 d gestation). Data were analyzed using PROC MIXED (SAS 9.4). Protein abundance of BHMT was greatest (P < 0.01) in liver suggesting active remethylation of homocysteine to methionine. This idea was supported by the greater (P < 0.05) mRNA of CBS, BHMT, MTR, SHMT1, and MAT1A (encoding OCM enzymes) in liver. The antioxidant protein GPX3 had greatest (P < 0.05) abundance in liver, whereas the glutathione-transferase GSTM1 was 5-fold greater (P < 0.05) in intestine than liver and muscle. Greatest concentrations of glycine, serine, and taurine along with lower cysteine underscored the relevance of OCM in fetal liver. Phosphoethanolamine concentration was greatest (4-fold, P < 0.05) in intestine and along with the greatest (P < 0.05) mRNA of SLC44A1 (choline transporter), CHKA, and CEPT1 underscored the importance of the CDP-choline pathway. Greatest (P < 0.05) mRNA of PPARA, CPT1A, and HMGCS2 along with lower PCK1 in liver highlighted a potential reliance on fatty acid oxidation. In contrast, greater (P < 0.05) concentration of myo-inositol in muscle and intestine suggested both tissues rely on glucose as main source of energy. Future research should address how environmental inputs such as maternal nutrition alter these pathways in fetal tissues and their phenotypic outcomes.

Ultrasonographic measurements in first trimester concepti identify predictors of birth weight and postnatal development in cattle

The placenta is a major driver of prenatal growth and involved in programming of postnatal performance. We therefore determined placental and embryo-fetal ultrasonographic parameters in early pregnancy and their relationships with birth weight and postnatal weights in a Bos indicus-Bos taurus composite beef cattle population. Pregnancies were generated in 2-yr-old Droughtmaster heifers by artificial insemination after estrus synchronization in 2 consecutive years (2009, n = 36 and 2010, n = 57), with a subset of 2010 heifers used again as lactating 3-yr-old cows in 2011 (n = 24). Each cohort was managed as 1 contemporary group for measurements of Corpus luteum diameter, amnion length and width, placentome width and thickness, and embryo-fetal crown-rump length, at 7 and 8 wk of gestation. This was followed by recordings of birth weight, branding weight at 5 to 6 mo of age and weaning weight 2 mo later. At a significance threshold of P < 0.05, placentome thickness at week 7 was negatively correlated with weights at birth (r = -0.23), branding (r = -0.25), and weaning (r = -0.35), whereas placentome width at week 7 (r = 0.24) and thickness at week 8 (r = 0.29) were positively correlated with birth weight. Thicker placentomes in males at week 7 (7%) difference mirrored sex differences in weights at birth (7%), branding (10%), and weaning (6%). The sex difference trend for birth weight was not consistent across sire-year combinations, ranging from -3.2 to +4.7 kg (birth weight of males - females per sire). These results support the hypothesis that placental parameters at the transition from embryo to fetal stage are major predictors of fetal and postnatal growth, albeit with significant environmentally induced plasticity, in stabilized B. indicus-B. taurus composite populations, and suggest that elements of B. indicus-B. taurus reciprocal differences in birth weight persist in composite populations.

Prenatal muscle fiber development and bundle structure in beef and dairy cattle

Muscle fiber development during gestation determines the muscle structure at birth and establishes the conditions for muscle development in growing cattle. Differences in muscle structure among beef cattle breeds and between beef and dairy cattle are obvious already shortly after birth. The objective of the study was to investigate the development of muscle fibers and muscle fiber bundle structure in semitendinosus muscle of divergent cattle breeds from 3 mo of gestation until birth. Fetuses of German Angus (GA), Galloway (GW), Belgian Blue (BB), and Holstein Friesian (HF) were harvested at 3, 4.5, 6, or 9 mo of gestation. Muscle sections were analyzed for fiber size and types as well as for bundle structure. The results confirmed that primary muscle fiber development occurs mainly during the first trimester of gestation. All fibers were initially positive for fetal fast myosin. Slow myosin as a marker for fiber maturation was detected in primary fibers at 3 mo of gestation showing a weak immunostaining. During the second trimester, the intensity of immunostaining strongly increased indicating increased slow myosin protein expression. Concurrently, the shape of primary fibers changed from myotubes to myofibers whereas the size stayed nearly constant. The main increase in muscle mass during the second trimester was caused by secondary fiber development. As an example, the ratio between secondary and primary fibers increased in Holstein Friesian fetuses from 5.9 at 4.5 mo of gestation to 21.6 at 6 mo of gestation. Primary and secondary fibers continued to growth during the third trimester. Regional differences in the density of slow muscle fibers were detected leading to greater variation within the muscle than among breeds. Structural organization of muscle fibers in muscle fiber bundles developed early in fetal life. At first, large main bundles were visible. Smaller structural units defined as primary bundles were measurable at 6 mo of gestation when most fibers were developed. The size of primary bundles nearly doubled from 6 mo of gestation to birth in all breeds. In summary, differences among breeds in the early fetal muscle fiber development were detected in contractile differentiation and partly in muscle fiber bundle structure. A prolonged secondary fiber generation and altered contractile differentiation may be involved in breed differences of postnatal muscle development.

Gestational, periparturient and preweaning growth traits of Holstein versus Gir x Holstein F1 crossbred dairy calves born to Holstein dams

The objectives of this study were to assess the gestational, periparturient and preweaning growth traits of Holstein vs Gir x Holstein (G x H F1) cross-bred dairy calves. Holstein cows (n=64) pregnant with Holstein (H x H) calves (bulls, n=16; heifers, n=18) or G x H (bulls, n=8; heifers, n=22) calves were sampled from 60 days of gestation through calving for serum progesterone (P4) and in utero placentome sizes, and at parturition for calving ease scores (CES), calf vigour scores (CVS), and placental characteristics. Post-calving calf measures included birth weight (day 0) and body weight (kg), hip width (HW), body length (BL), wither height (WH), hip height (HH) and heart girth (HG) through 42 days of age. Serum IgG and calf vital function tests (respiration rate (RR), heart rate (HR), rectal temperature (RT) and fecal scores) were recorded on days 1, 3, 7 and 14 of age (a.m. and p.m.). Serum gestational P4 was higher (p < 0.05) for cows with H x H than G x H calves. Placentome measurements in utero were greater (p < 0.01) for H x H calves than for G x H calves, while at parturition placental characteristics did not differ (p > 0.10). Gestation length, CES and CVS also did not differ (p > 0.10) between H x H and G x H calves. Calf RR and HR were higher (p < 0.05) for H x H than G x H calves at both a.m. and p.m., while RT, fecal scores and serum IgG did not differ (p > 0.10) between H x H and G x H calves. Birth weight did not differ (p > 0.10) between H x H and G x H calves within sex. Moreover, bulls did not differ (p > 0.10) in any of the growth measures between H x H and G x H calves, whereas H x H heifers at days 28 and 42 of age were greater (p < 0.05) in all growth traits than G x H heifers. Nevertheless, the relative change in growth measures over time (days 0 to 42) did not differ (p > 0.10) between H x H and G x H calves. While subtle differences in gestational, early growth and vital function characteristics were observed, these data suggest very similar developmental profiles between H x H and G x H calves.

Effect of grazing system on fetal development in Nellore cattle

Intensive grazing systems for beef females, based on abundant availability of high quality forages and supplementary concentrates, may affect fetal development. The objective of this study was to determine the effect of grazing system on length of gestation, fetal development, and characteristics of the calf at birth. Twenty-four pregnant (bred to Nellore bulls) Nellore females were allocated into two groups. The control group (G1) grazed Brachiaria decumbens (signal grass) in a traditional (extensive) grazing system and the second group (G2) were managed on Panicum maximumcv. Tanzania 1 (Tanzania grass) in an intensive grazing system. Fetal development was evaluated by ultrasonography on days 31, 45, 59, 94, 122, 220, and 255 of gestation. The diameter of the amniotic and allantoic cavities, crown-rump length, circumference, and diameter of the head and ocular orbit were determined. At birth, calves were weighed and height, length, thoracic circumference, and ocular orbit and bi-parietal diameters were measured. There were no differences (P > 0.05) in fetal development. The G1 cows had a longer gestation period (4.5 days; P<0.05) and their calves had greater (P<0.05) weight, height, length, and thoracic circumference at birth. In conclusion, Nellore females raised under intensive pasture management conditions, had significantly shorter gestation and smaller calves at birth than those raised under extensive pasture management conditions. Therefore, adoption of new management practices (e.g. intensive pasture management), should take into consideration animal behavior and productivity.

Dystocia-related risk factors

Dystocia is one of the leading causes of calf mortality between birth and weaning in beef cattle. An understanding of the effects of parturition and dystocia on perinatal calf viability is paramount for the development of breeding and calving programs that will minimize calf losses. This article discusses the factors affecting birth weight and replacement heifer development and redefines dystocia as any birth that reduces calf viability, causes maternal injury, or reduces maternal reproduction.

Cold thermoregulation in the newborn calf

During the fetal to neonatal transition, the newborn calf encounters severe thermolysis due to an abrupt change in thermal environment that is compounded by evaporation of fetal fluids and severe weather conditions. Maintenance of homeothermy during the neonatal period necessitates an acute and sustained thermogenic response by the newborn calf. It is now widely accepted that this thermogenic response is derived from both shivering thermogenesis in muscle tissue and nonshivering thermogenesis in brown adipose tissue (BAT). It is critical that newborn calves possess functional BAT during the neonatal period. This article focuses on the pre- and postnatal factors that influence nonshivering thermogenesis of BAT in the neonatal calf.