Dam parity affects fetal growth, placental size, and neonatal metabolism in spring-born beef calves.

To determine effects of dam parity on perinatal nutrient availability in beef cattle, data and samples were collected from 18 primiparous and 35 multiparous spring-calving Sim-Angus dams and their calves. Time to stand was recorded and neonatal vigor assessed. Jugular blood was collected from a subset of calves at 0 (post-standing and pre-suckling) 6, 12, 24, 48, and 72 h of age, and blood chemistry panels were completed. Expelled placentas were dissected, dried, and weighed. Prepartum maternal circulating glucose, non-esterified fatty acids (NEFA), triglycerides, and urea N were analyzed. All statistical models included the fixed effect of dam parity, and calf sex (when P ≤ 0.25) was included for calf and placental variables. Effects of sampling hour, and parity × hour were included for calf metabolites over time using repeated measures. Multiparous dams had greater body weight prepartum (P < 0.001) but similar (P = 0.25) body condition score. Maternal circulating urea N and triglycerides were greater (P ≤ 0.05) in multiparous dams pre-calving. Calves born to primiparous dams weighed 10% less (P ≤ 0.04) at birth with smaller (P ≤ 0.01) heart and abdominal girths. Cotyledonary, intercotyledonary, and total placental masses were less (P ≤ 0.05) for primiparous dams. Dam parity did not affect (P ≥ 0.58) calf time to stand, vigor score at 10 min, or rectal temperature. Serum glucose was greater (P = 0.03) at 0 h but less (P ≤ 0.04) at all other hours in calves from primiparous dams. Calves from primiparous dams had greater (P ≤ 0.02) serum NEFA at 6, 12, and 24 h although plasma triglycerides were greater (P < 0.001) at 6 h. Calves from primiparous dams had greater (P ≤ 0.04) serum urea N at 12 h and creatinine at 12 and 24 h. Plasma insulin was greater (P ≤ 0.04) in calves from multiparous dams at 12, 48, and 72 h, but parity did not affect (P ≥ 0.18) serum total protein or plasma cortisol. Serum aspartate aminotransferase was greater (P ≤ 0.04) at 6 and 24 h, creatine kinase was greater at 24 h, and gamma-glutamyl transpeptidase was less (P ≤ 0.04) at 6, 12, and 24 h, for calves from primiparous dams. Calves born to primiparous dams had greater (P ≤ 0.02) total bilirubin and direct bilirubin at 12 and 24 h. Data indicate that calves born to first-parity heifers had decreased perinatal nutrient availability, resulting in reduced fetal and placental growth, as well as greater energy reserve mobilization and metabolic indicators of stress as neonates.

Approximately two-thirds of beef calf deaths prior to weaning occur within the first 3 wk after birth. The goal to have heifers produce their first calf by 2 yr of age likely contributes to factors that limit nutrients available for fetuses and calves immediately after birth. However, little is known about differences in heifers (first parity) and cows (later parities) regarding factors affecting calf resilience, such as fetal growth and calf metabolism shortly after birth. Our data show that calves born to first-parity heifers had altered nutrient availability, demonstrated through smaller placentas, lower birth weights, and altered metabolites in early life. Although calves had similar vigor and ability to maintain body temperature, calves born to first-parity heifers had to mobilize more energy and had lower insulin during the first 3 d post-birth. Calves born to first-parity heifers had greater indicators of stress during the first 72 h of life not associated with calving difficulties. Overall, these effects may have increased morbidity and mortality of calves born to first-parity heifers if they were in a less intensively-managed system. Better understanding of challenges faced by calves born to first-parity dams provides opportunities for their improved management.

Effects of spring- versus fall-calving on perinatal nutrient availability and neonatal vigor in beef cattle.

To determine the effect of calving season on perinatal nutrient availability and neonatal beef calf vigor, data were collected from 4 spring- (average calving date: February 14; n = 203 total) and 4 fall- (average calving date: September 20; n = 179 total) calving experiments. Time to stand was determined as minutes from birth to standing for 5 s. After birth, calf weight and size (length, heart and abdominal girth, and cannon circumference) were recorded. Jugular blood samples and rectal temperatures were obtained at 0, 6, 12, and 24 h postnatally in 6 experiments and at 48 h postnatally in Exp. 2 to 8. Data were analyzed with fixed effects of season (single point) or season, hour, and their interaction (over time, using repeated measures). Experiment was a random effect; calf sex was included when P ≤ 0.25. Within calving season, correlations were determined between calf size, vigor, and 48-h serum total protein. Fall-born calves tended to have lighter (P = 0.09) birth weight and faster (P = 0.05) time to stand than spring-born calves. Season did not affect (P ≥ 0.18) gestation length, other calf size measures, or 48-h serum total protein. Fall-born calves had greater (P ≤ 0.003) rectal temperature at 0, 24, and 48 h postnatal. Spring-born calves had greater (P ≤ 0.009) circulating glucose at 0 h, serum non-esterified fatty acids at 0 and 6 h, and plasma triglycerides at 0, 6, 12, and 48 h. Fall-born calves had greater (P ≤ 0.03) sodium from 6 to 48 h and magnesium from 0 to 24 h of age. Phosphorus was greater (P ≤ 0.02) at 6 and 12 h of age in spring-born calves. Spring-born calves had greater (P ≤ 0.04) aspartate aminotransferase at 12 and 24 h and creatine kinase at 0 and 12 h of age. Fall-born calves had greater (P ≤ 0.03) albumin, calcium, and chloride, had lower (P ≤ 0.03) bicarbonate and direct bilirubin, and tended to have greater (P = 0.10) anion gap (all main effects of calving season). Calf birth weight had a weak positive relationship (P ≤ 0.03) with 48-h serum total protein and time to stand in fall-born, but not spring-born, calves. Overall, fetal growth was restricted and neonatal dehydration was increased by warm conditions for fall-born calves, but vigor and metabolism were negatively affected by cold conditions in spring-born calves. These data suggest that calving season influences perinatal nutrient availability, which may impact the transition of beef calves to postnatal life.

Blood chemistry and rectal temperature changes in a population of healthy, fall-born, suckling beef calves from birth to 72 h of age.

To determine changes in suckling neonatal beef calf blood chemistry and body temperature during the first 72 h of life, jugular blood samples and rectal temperatures were obtained from 24 healthy, fall-born Angus-cross and Hereford calves (average calving date = September 11) at 0 (after standing, but pre-suckling), 6, 12, 24, 48, and 72 h postnatally. Serum chemistry panels were conducted, and plasma triglycerides and serum non-esterified fatty acids (NEFA) were also determined. Data were analyzed using sampling hour as a repeated effect, and individual data points were compared to adult bovine reference intervals. All serum chemistry measures were affected by hour of age except bicarbonate (P = 0.48). Serum glucose, total protein, and globulin concentrations increased (P < 0.001) from 0 to 24 h. Plasma triglycerides increased (P < 0.001) from 0 to 6 h and 24 to 72 h. Serum urea nitrogen increased (P < 0.001) from 0 to 6 h and decreased (P = 0.01) from 48 to 72 h. Serum NEFA and creatine kinase (CK) increased (P < 0.001) from 0 to 6 h, but decreased (P ≤ 0.02) from 12 to 72 h. Serum magnesium, aspartate aminotransferase (AST), and total and direct bilirubin increased (P < 0.001) during the first 12 h, then decreased (P < 0.001) from 24 to 72 h. Gamma-glutamyl transpeptidase (GGT) increased (P < 0.001) from 0 to 12, and then decreased (P < 0.003) from 12 to 48 h. Serum creatinine decreased (P < 0.001) from 0 to 72 h, and albumin decreased (P < 0.01) from 0 to 12 h but increased (P < 0.001) from 24 to 48 h. Anion gap decreased (P ≤ 0.05) from 6 to 24 h. No serum components measured were within adult bovine reference intervals for all calves at all sampling times. All serum albumin concentrations were outside of reference intervals, and the majority of serum glucose, calcium, phosphorus, potassium, CK, GGT, and total bilirubin were outside of reference intervals. More serum chemistry measures diverged from reference intervals in the first 24 h of neonatal life. Rectal temperature decreased (P = 0.003) from 0 to 6 h of age, then increased (P ≤ 0.02) from 12 to 48 h. In summary, blood chemistry profiles of healthy, suckling neonatal beef calves change over the first 72 h of life, indicating rapid changes in metabolism and physiology. Bovine reference intervals based on adults do not appear to represent neonatal calves; thus, neonatal status and animal age should be taken into consideration when interpreting serum chemistry in a clinical or research setting.

Factors affecting placental size in beef cattle: Maternal and fetal influences.

Our objectives were to determine the effects of dam body condition score (BCS), age of dam, and calf sex on placental size and the relationships between dam body weight (BW) and calf size with placental size. Expelled placentas and calf size at birth were collected from crossbred beef heifers and cows during four experiments (n = 22 to 39/experiment). Placentas deemed complete by visual inspection were dissected; dry weights were determined for cotyledonary and intercotyledonary tissues. Mixed linear models were used to individually determine main effects of peripartum BCS category [Thin (<5), Moderate (=5), or Fleshy (≥6)], age of dam category [Primiparous (2 yr), Young (3-4 yr), or Mature (≥5 yr)], and calf sex on placental measures. Correlations were determined for placental characteristics with prepartum dam BW, gestation length, and calf size. Thin BCS dams had lower (P ≤ 0.05) cotyledonary, total placental, and average cotyledon weights and greater placental efficiency (calf birth BW/placental weight) than moderate and fleshy dams. Intercotyledonary weight was lower (P < 0.01) in thin BCS dams compared with fleshy dams. Thin and moderate BCS dams had smaller (P ≤ 0.04) calf birth BW than fleshy dams. Primiparous dams had lower (P ≤ 0.05) total placental and average cotyledon weights than young and mature dams, yet calf birth BW was unaffected (P = 0.17). Male calves were heavier (P = 0.01) than females, yet there were no differences (P ≥ 0.59) in placental weights. Calf birth BW and heart girth had moderate positive correlations (P < 0.01) and shoulder to rump length and abdominal girth had weak positive correlations (P < 0.01) with all placental weights. Dam prepartum BW and calf flank girth had moderate positive correlations (P < 0.01) with total placental weights and weak positive correlations (P < 0.01) with cotyledonary and average cotyledon weights. Intercotyledonary weight had moderate positive correlations (P < 0.01) with gestation length and calf flank girth and a weak positive correlation (P < 0.01) with dam prepartum BW. Gestation length had a weak positive correlation (P = 0.02) with total placental weight. Number of cotyledons was not correlated (P ≥ 0.28) with any dam or offspring characteristics. In conclusion, these data suggest that both maternal age and BCS affected placental size. Calf size at birth and placental weight were positively correlated, but it is still unknown which controls and signals for the growth of the other.

Serum Chemistry and Hematology Changes in Neonatal Stock-Type Foals During the First 72 Hours of Life.

Limited research has characterized blood chemistry in healthy stock-type foals. Our objectives were to determine foal serum chemistry and hematology changes during the first 72 hours postnatal and compare these with adult horse reference ranges. Over 3 foaling seasons, serum chemistry and hematology were determined for 16 healthy stock-type foals born to similarly managed mares. Blood was collected at 0 hours (before nursing but after standing, within 85 minutes of birth) and 6, 12, 24, 48, and 72 hours after initial sampling. Data were analyzed with sampling hour, year, and their interaction as fixed effects. Serum glucose and triglyceride concentrations increased (P < .001) from 0 to 24 hours. Triglycerides increased (P < .001) and glucose decreased (P = .01) between 24 to 48 hours. Serum nonesterified fatty acids increased (P = .04) from 0 to 6 hours and decreased (P ≤ .01) from 6 to 24 hours. Serum urea nitrogen increased (P < .001) between 0 and 6 hours and decreased (P < .001) from 12 to 72 hours. Serum total protein and globulin concentrations increased (P < .001) from 0 to 12 hours, albumin decreased (P ≤ .01) from 0 to 24, and creatinine decreased (P ≤ .02) from 0 to 72 hours. Hour also affected (P ≤ .03) electrolytes, metabolic enzymes, and all hematological components except for mean corpuscular hemoglobin (P = .77). These data demonstrate dynamic blood biochemical and hematological changes throughout the first 72 hours in foals, suggesting that sampling time should be considered when evaluating individual neonates.

Locomotion behavior changes in peripartum beef cows and heifers.

Changes in locomotor activity of beef females during the 72 h prepartum were determined in 3 experiments: (i) a 2-yr study with spring-calving multiparous cows (Exp. 1; n = 34 and 27 for years 1 and 2, respectively); (ii) spring-calving primiparous (first pregnancy; n = 13) and multiparous (n = 21) dams (Exp. 2); and (iii) fall-calving multiparous cows (Exp. 3; n = 33). For all experiments, IceQube activity monitors (iceRobotics, Edinburgh, UK) were placed above the left hind fetlock of pregnant females ≥3 d prepartum. During the calving season, females were housed in 18 × 61 m drylots with ad libitum access to hay or haylage. Parturition was closely monitored, and time of birth was noted. Motion index, standing and lying time, step count, and the number of lying bouts for each dam (summed per hour) were determined for the 72 h preceding calving. Within experiment, data were analyzed by day (days -3 to -1 prepartum), by 6-h period during the final 24 h prepartum, and by hour during the final 6 h prepartum using a mixed model with time as a repeated effect. Year was also included as a fixed effect in Exp. 1. Fixed effects of parity and time prepartum × parity were included for Exp. 2. In all 3 experiments, motion index, standing time, step count, and the number of lying bouts were greater (P < 0.001) on day -1 compared with days -2 and -3 prepartum. In the 24 h prepartum, dams had greater (P < 0.01) motion index, standing time, step count, and the number of lying bouts during 6 h preceding parturition compared with -11 to -6 h in all experiments. Motion index, step count, and lying bouts changed (P ≤ 0.02) during the last 6 h in all experiments. Primiparous dams had more (P ≤ 0.01) lying bouts than multiparous dams during the last day and -11 to -6 prepartum. In all experiments, the number of lying bouts more than doubled (P < 0.001) from -2 to -1 prepartum, with no effect of year (P = 0.57) in Exp. 1 or parity (P ≥ 0.29) in Exp. 2. This suggests that lying bout changes may be the most reliable of parameters measured in detection of calving. Moreover, fall-calving cow behavioral patterns were similar to changes observed in spring-calving females, suggesting that calving season may have minimal effects on pre-calving behavior. Overall, electronic locomotor activity monitors can detect behavioral changes peripartum in beef heifers and cows. More research is necessary to determine if these can be used to remotely sense early signs of parturition in beef cattle.