Calf Gender Research Articles

Effect of Calf Gender on Milk Composition, Reproductive Hormones and Serum Biochemical Parameters of Female Dromedary Camel

Arabian dromedary camels received little interest compared to other domestic animals. Literature data about factors affecting camel's milk composition and serum biochemical profile are limited and not sufficient. In the present study a total of 60 milk samples (Three milk samples were collected from each animal for three consecutive days) and 20 blood samples were collected individually from 20 clinically healthy female dromedary camels at first month of lactation to study the effect of calf gender on milk composition, some hormonal and serum biochemical profile. Animals were grouped into two groups, A and B. Group A contained 10 females dromedary camels that gave birth to male calves and Group B contained 10 females dromedary camels that gave birth to female calves. All samples were analyzed, and the result revealed that calf gender has non-significant effect (P>0.05) on milk composition, serum progesterone, cortisol, calcium and magnesium levels. While significant effect but not sharp (P=0.02) were observed on serum phosphorus levels and high significant effect were recorded on serum estrogen level (P<0.0001).Since such study are rare inEgypt, the data presented, could be used as a reference guide for the effect of calf gender on milk composition, reproductive hormones and serum biochemical parameters of female dromedary camel during early lactation.

Factors Affecting Morbidity, Mortality, and Growth Rates in Suckling Calves under Conditions of Nile Delta, Egypt

The aim of this study was to estimate morbidity, mortality risk, and growth rates during period from birth to weaning in calves under the conditions of Nile Delta. Data were collected during the period from January 2009 until December 2018. Data were collected from 1727 newborn calves from 3 breeds (869 Friesian, 488 Baladi and 370 their Crossbred). The overall rates of calf morbidity and mortality during the period of pre-weaning reached 74.35% and 12.16%, respectively. The majority of cases occurred within the period from 8 to 30 days of calf age (44.93% and 6.20%, respectively). Morbidity and mortality rates were the lowest for Crossbred calves. The means of calf weight at birth and weaning, amount of milk used for suckling and the average daily gain were significantly greater for Friesian calves. Furthermore, morbidity, mortality and growth rates were affected by calf birth season, dam parity, calf gender, calf weight at birth and cause of disease. Incidence and mortality rates due to enteric diseases alone during the pre-weaning period were higher (71.18% and 36.67%, respectively). Calves affected by the diseases had significantly decreased weight at weaning compared with healthy calves. It is clear from this study that elevated calf mortality was associated with low weight at birth. Accordingly, we recommend more attention must be given to proper management and improved health conditions of the calves. It must be obtained ideal weights at birth, alleviate heat stress during the summer, and care for primiparous cows.

Strategy to improve the parturition ability in crossbred recipients implanted with embryos produced in vitro

The aim of this study was to evaluate the synchronization rate, ease to parturition, calves viability and retained placenta rate for Nellore recipients treated with triancinolone (TRI) + dexametasone (DEXA) + PGF2α (d-CLO). Hundred-ninety-four crossbred recipients (½ Nellore/ ½ Caracu) were divided into two groups (TRI, n = 97; Control, n = 97) and observed from 285 to 292 days of pregnancy. On Day 285, animals from Group TRI received 1mg/60 Kg of BW/IM of triancinolone (Retardoesteróide®, Hertape Calier Saúde Animal S/A) followed of association of 25mg of dexametasone (Caliercortin®, Hertape Calier Saúde Animal S/A) and 150μg of D-cloprostenol (Veteglan®, Hertape Calier Saúde Animal S/A) on Day 292. Animals from Control received injections of saline solution in same days. TRI had higher synchronization of parturition than Control (79.4% vs. 19.5, respectively; P < 0.05), as well TRI had lower assistance of parturition. No differences were observed for assistance of parturition comparing the born weight and gender of calves. TRI had lesser placenta retained than Control (11.4% vs. 25.8%, respectively; P < 0.05). In short, this strategy of induction resulted in better conditions of assistance and quality of parturition, decreasing the placenta retained in Nellore recipients implanted with embryos produced in vitro.

Assessment the Calf’s Welfare Due to The Gender, Number of Offspring and Calving Status in Holstein Calves

The aim of the present paper was to study the influence of gender, number of offspring, calving status on both health and welfare. Out of 3000 heads, data for 429 Holstein female calves and 551 male calves which have been born during one year were used with computer records. The result suggested that abnormal behaviour during 1st 12 hours of calf's life have been significantly affected by twinning and dystocia .The presence and duration of behaviour related to respiratory, digestive or mixed disorders were significantly higher in females, the calf’s growth rate was higher in male than female with significance difference, while its birth weight was significantly higher in dystocia than calves from normal parturition. There was a non-significant effect of calf gender, number of offspring and parturition state on calves weaning age. It could be concluded that Calf gender, number of offspring and parturition state have a different effects on behaviour and growth performance of calves from birth till weaning. Abnormal behaviours during the first 12 hours of calf's life as delayed sternal recumbancy, standing, abnormal suckling have been significantly affected by twinning and dystocia and not significantly affected by calf sex. Presence and duration of behaviour related to respiratory, digestive or mixed disorders were significantly higher in females than males, where these disorders were significantly higher in case of dystocia and twinning births. Culling of cows with incidence of twinning is recommended to control the decreased fertility, decreased total number of calves over the lifespan of the cow, and decreased milk production.

Association between gestation length and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran.

In this study, 252,798 lactations on 108,077 cows in 433 herds were used to determine the association between gestation length (GL) and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran. The GL averaged 278.1 ± 5.41 d, was categorized as short (SGL; at 1 SD below the population mean), average (AGL; the population mean ± 1 SD), or long (LGL; at least 1 SD above the population mean). Factors including parity, calf gender and calving season were associated with the GL. Primiparous cows with SGL had less lactation performance than those with longer GL; however, there was no difference between those with AGL and LGL. Multiparous cows with longer GL always had more partial and 305-d lactation performance. Primiparous cows with SGL produced less milk at the beginning of lactation and at the peak than those with AGL or LGL; inverse trends were found for lactation persistency, upward and downward slopes of the lactation curve. Within multiparous, a direct relationship was found between GL and the peak yield, where cows with longer GL always produced more milk at the peak. Multiparous cows with SGL produced less milk at the beginning of lactation, reached their peaks later, had higher lactation persistency and showed a lower upward slope of lactation curve than those with AGL or LGL. There was a direct relationship between GL and calf birth weight, where cows with longer GL had calves with more weight at the birth. Within primiparous, cows with SGL had the lowest and those with LGL had the highest rate of dystocia. However, multiparous cows with AGL had a lower rate of dystocia than those with SGL or LGL. Although there was a direct relationship between GL and lactation performance, intermediate GL seems optimal when considering dystocia.

Unexpected empirical dependence of calf gender on insemination time: system-based explanation

Unexpected empirical dependence of calf gender on insemination time: system-based explanation

Distribución de partos e influencia de algunos factores de variación sobre el intervalo entre partos y mortalidad de terneros, bajo paridera continua, en vacas de cría en la dehesa

A total of 619 calvings and 547 intervals between calvings (IBC) from 97 cows, 15 Retinta cows and 82 crossbreed (Charolais x Retinta) cows, reared under continuous calving during eight consecutive years were controlled in the Dehesa ecosystem. The 39.25% of the calvings occured from December to February and only the 14.38% from August to October. The heifers and cows of seventh, eighth, tenth and eleventh and following calving showed an IBC higher than the cows of third, fourth, fitth and sixth calving. The variable “cow” had significant effect on the IBC, but the factors “gender of suckled calf”, “year”, “bull”, “calving month”, “fence” and, “body condition score at calving” had not significant influence on IBC. The age at first calving had not significant effect on IBC of heifer and average IBC of cows. Age at weaning of born calves from November to March was significantly lower than those born calves from May to July. The calf’s mortality seems affected by the genetic type of calf and the birth time. The use of Charolais bulls leads to a calves mortality at birth higher regarding Limousine bulls.

Relations Between Birth Weight and Some Body Measurements in Anatolian Black Cattle Calf Grown in Breeding Conditions

In this study, it was aimed to investigate the relationship between birth weights and body measurements of Anatolian Black cattle and to develop linear regression equations to estimate calf birth weights. The animal material of this study, 108 Anatolian Black Cattle were used which were born in 2018. Those animals came from 21 different farms which are located in Osmansin village, Çamlıdere district of Ankara province. In study, birth weights (BW), withers height (WH), rump height (RH), chest girth, (CG), chest depth (CD), body length (BL) and front wrist girth (FWG) were obtained in the order of; 14.451±0.397 kg, 57.775±0.347 cm, 59.843±0.382 cm, 53.510±0.517 cm, 24.137±0.281cm, 49.608±0.581 cm, 7.123±0.068 cm. The effect of calf gender was statistically significant only in FCG (P<0.05), but not statistically significant in other characteristics. The effect of age maternal WH, RH, CG and CD values were significant (P<0.05), on the other hand, there is no significant (P>0.05) effect BW, BL and FCG. The highest correlation was found between BW and CG (r=0.808) however, the lowest correlation was found between BW and FCG (r=0.467).In addition, the highest correlation between body measurements was found between WH and RH with a value of 0.965. Regression analysis was performed between the chest girth and the live weight measurement, which is the measurement value that gives the highest correlation coefficient so that the live weight estimate can be made with the body weight parameters; BW = - 15.53 + 0.5577 CG (R 2 = 65.3%) formula was obtained.

Prediction of stillbirth in Holstein‐Friesian dairy cattle by measuring metabolic and endocrine parameters during the peripartal period

The aim of this study was to determine whether measurements of certain metabolic (non-esterified fatty acid, β-hydroxybutyrate, glucose, total protein, albumin, urea-nitrogen, aspartate aminotransferase, total calcium, inorganic phosphate and magnesium) and endocrine (cortisol, thyroxine, triiodothyronine, insulin and insulin-like growth factor) parameters in the peripartal period (2months and 3weeks before expected calving and within 1hr after calving) were related to the prevalence of stillbirth in a Holstein-Friesian farm in Hungary. All together 155 dairy cattle (n=22 primiparous, n=133 multiparous cows) were monitored in two separate years selected randomly on the same farm. Overall, the prevalence of stillbirth was 11% (n=17). Significantly higher stillbirth rate was detected in case of heifer calvings (OR=8.5), and when ≥3 assistants (severe dystocia; OR=8.9) were needed to assist at calving while the body condition score of the dams, the bodyweight and gender of the newborn calves, the percentage of posterior presentations had no significant effect on stillbirth rate. There were no significant differences between cows without and with stillbirth in case of any measured metabolic and endocrine parameters during the examined time periods. At the same time, some of the metabolic parameters (TP, AST and inorg.P) showed some significant differences among the stillbirth groups, but stillbirth could not be predicted by the measured parameters and therefore the role of metabolic and/or endocrine changes on the prevalence of stillbirth needs further elucidation.

Contribuição de fatores não-genéticos para o desempenho reprodutivo de vacas Mirandesa

Conhecer as características reprodutivas da raça bovina Mirandesa é fundamental para o melhoramento e conservação desta raça de carne, sobretudo pela sua baixa diversidade genética. A depressão por consanguinidade acompanha-se frequentemente de desempenhos individuais e maternais mais fracos, que podem agravar os efeitos ambientais. Neste trabalho utilizaram-se 7386 registos do Livro Genealógico para caracterizar alguns indicadores reprodutivos: a idade ao primeiro parto (AFC), a duração da gestação (PL), o intervalo entre partos (CI), a distribuição partos no ano (CD) e a longevidade produtiva (PLf). Testaram-se ainda efeitos não genéticos na sua expressão, através de métodos não-paramétricos, por não estarem cumpridos os pressupostos de normalidade. A mediana para a AFC aproximou-se dos 32 meses, variando com o sistema de produção, a exploração, e o ano e estação de nascimento. A média de PL (287±8.9 dias) foi afetada pela paridade e sexo da cria. A mediana do CI foi de 378 dias, e variou apenas com o programa de reprodução, paridade, ano e estação. Os partos, irregularmente distribuídos ao longo do ano, mostraram padrões distintos segundo o sistema de produção. A longevidade produtiva desta raça foi de 6,45 anos, e 20% da população apresentou uma PLf superior a dez anos. Este trabalho sugere serem a estratégia do agricultor e a nutrição os principais efeitos não genéticos limitando o desempenho reprodutivo nesta raça, a considerar para aumentar o número de vitelos produzidos anualmente em paralelo com uma cuidada seleção de reprodutores para reduzir o inbreeding da raça.

Predictors of beef calf temperament at weaning and its impact on temperament at breeding and reproductive performance.

Two experiments were conducted to determine (i) factors influencing calf temperament at weaning, (ii) association between heifer-calf temperament at weaning and temperament at breeding and (iii) effect of heifer-calf temperament on pregnancy rate per artificial insemination (P/AI). In experiment 1, beef cows and their calves (n=285) from three farms were used. Sire docility estimated progeny difference (EPD) score, birth type (normal or assisted), calf gender, calf behaviour (during 1st 4weeks) and calf health status (until weaning) were recorded. Cows and calves were assigned a temperament score (0-calm; 1-excitable), and all cows were given a body condition score (BCS, 1-9; 1-emaciated; 9-obese) at weaning. Calf's illness (p<.05), low sire docility EPD score (p<.05), altered gait (p<.05), altered resting behaviour (p<.01), reduced/no play behaviour (p<.05) and cow excitable temperament (p<.001) increased calf excitable temperament at weaning. In experiment 2, replacement heifer-calves (n=758) from 12 farms were assigned a temperament score at weaning and later at breeding. Blood from 40 calves at weaning and 31 heifers at initiation of synchronization (same animals) was collected by coccygeal venipuncture for determination of circulating cortisol and substance P concentrations. Heifers were assigned a BCS and reproductive tract score (RTS, 1-5; 1-immature, acyclic; 5-mature, cyclic), synchronized for fixed time AI, observed for oestrus and were artificially inseminated. Cortisol concentrations were increased in excitable heifer-calves compared to calm heifer-calves at weaning (p<.05), and substance P was increased in excitable compared to calm females both at weaning and breeding (p<.05). Low sire EPD docility score (p<.01), heifer-calf excitable temperament at weaning increased excitable temperament at breeding (p<.01). Controlling for BCS categories (p<.01), oestrous expression (p<.0001) and temperament at breeding by oestrous expression (p<.05), the calf's excitable temperament at weaning (p<.001) reduced P/AI (Calm, 62.7 (244/389) vs. Excitable, 53.4% (197/369); p<.01). In conclusion, selection of docile cows and sires with greater docility EPD score should be given consideration to reduce calf excitement. Temperament in beef female can be detected earlier in their life and could be used as a tool in the selection process and to improve their performances.

Prevalence and risk factors for stillbirths in Holstein cows in a hot environment

Risk factors for stillbirth were studied in a dairy operation in northern Mexico (25°N). Data set consisted of 29406 full term calving records. Factors affecting stillbirths were analyzed using a step-wise multivariable logistic regression models. The predictive indicators of stillbirth risk were: temperature-humidity index (THI) during pregnancy and at calving, season of calving, calf birth weight, gestation length, semen characteristics (conventional or sexed), gender of calves, hour of calving and type of parturition (normal or dystocic). Throughout the study period, 7.3 (95%, confidence interval= 7.0–7.6) of every 100 calving events had a stillborn calf. Stillborns were higher with severe dystocia compared with non-assisted births (29.0% vs. 6.2%, p&lt;0.0001) and calves with birth weights &lt;35 kg compared with heavier calves at calving (19.3% vs. 2.3%, p&lt;0.0001), and was lower in calves whose gestation length was &gt;278 d compared with calves with shorter gestation periods (2.8% vs. 30.0%, p&lt;0.0001). Cows in a severe state of heat stress prenatally and at birth (THI &gt;83 units) had 1.3 higher risk of stillbirths than cows suffering reduced heat stress (p&lt;0.0001). Evidence for a greater (p&lt;0.001) stillbirth rates in cows with parturitions between 18:00 and 19:00 h compared with cows calving during other hours of the day was found (9.1% vs. 7.1%). Together, these results demonstrate that ameliorating heat stress during the peripartum period is an important management practice to reduce stillbirths in Holstein cows in this warm climate. Additionally, a greater attention of parturition around sunset can lower the current stillbirth rates.

Social rank and reproductive performance in a herd of farmed red deer females (Cervus elaphus)

Hierarchical relationships between individuals determine unequal access to recourses like food and individuals of the other gender, resulting in a higher reproductive success of high-social ranked individuals. Environmental conditions and food availability may determine how strong these effects are. The aim of this work was to determine if social rank of farmed red deer females affect the reproductive results of a hormonal oestrous synchronisation treatment with ad libitum food. The studied responses included the time to oestrus onset, percentage of females that came into oestrus, conception and calving rates, gestation length, and calf gender. The study was performed during autumn on a research farm located in Mexico (20°36ʹ N, 99°55ʹ W). Forty-nine adult red deer females were assigned to two replications of 21 and 28 animals respectively and were allocated into independent paddocks with ad libitum food and water availability. Oestrous cycles were synchronised with a traditional protocol of intravaginal devices impregnated with progesterone. Agonistic behaviours between females were recorded (total = 1626 interactions), hierarchical position (Success Index = SI) of each animal was calculated and individuals were categorised as high (n = 13), medium (n = 20) or low-ranked (n = 16) individuals. Reproductive data were recorded during the 5 days after the oestrous synchronisation treatment and during the calving period. Any of the recorded responses differ between HR, MR and LR females. Female SI, age and bodyweight were not related with the probability of coming into oestrus, result pregnant, and giving birth to a male calf. Thirty-seven (78.5%) females of this study gave birth. From these calves, 15 were males and 22 were females. Due to high percentage of females in oestrus that gave birth (85.7%), it was not possible to detect the relationship between female SI, age, and bodyweight with the conception rate. Female SI, age and bodyweight were unrelated to time to oestrus onset (r2 = 0.09; P = 0.17), and to gestation length (r2 = 0.10; P = 0.20). In conclusion, with ad libitum high quality food, the social rank of red deer hinds did not affect the time to oestrus onset, percentage of females that came into oestrus, gestation length, calving and conception rates, and offspring sex ratio after an oestrous synchronisation hormonal treatment.

Effect of Calf Gender on Milk Yield and Fatty Acid Content in Holstein Dairy Cows.

The scale of sexed semen use to avoid the birth of unwanted bull calves in the UK dairy industry depends on several economic factors. It has been suggested in other studies that calf gender may affect milk yield in Holsteins- something that would affect the economics of sexed semen use. The present study used a large milk recording data set to evaluate the effect of calf gender (both calf born and calf in utero) on both milk yield and saturated fat content. Linear regression was used to model data for first lactation and second lactation separately. Results showed that giving birth to a heifer calf conferred a 1% milk yield advantage in first lactation heifers, whilst giving birth to a bull calf conferred a 0.5% advantage in second lactation. Heifer calves were also associated with a 0.66kg reduction in saturated fatty acid content of milk in first lactation, but there was no significant difference between the genders in second lactation. No relationship was found between calf gender and milk mono- or polyunsaturated fatty acid content. The observed effects of calf gender on both yield and saturated fatty acid content was considered minor when compared to nutritional and genetic influences.

DIAGNOSIS OF PERSISTENT BVD IN ONE DAY OLD AND OLDER THAN 30 DAYS CALVES WITH RAPID KIT TESTS

Bovine Viral Diarrhoea (BVD) is an important disease of cattle which causes alimentary, respiratory and reproductive disorders and serious economic losses. Today, eradication of disease is compulsory for the increase of dairies and achieving more healthier herds. In cattle, if the calves are infected with BVD from the uterus in the first trimester of pregnancy, they are born persistent infected (PI) antigen(+). The PI calves are smaller or normal in apperance than normal calves. Persistent infected (PI) calves spread the virus throughout their lives and infect their surroundings. BVD causes early embrionic death, calves born with anomalies and immunosuppression in infected animals. In this study 200 calves between 1–30 days old from Burdur province are screened with BVD rapid test kit. In the screening, 13 calves (6.5%) are found BVDV ag(+). The gender of PI calves are found 4% female (8/200) and 2.5% male (5/200). In the 5% of PI calves (10/200), respiratory and alimentary problems were clinically seen. The antigen(+) animals are put out of the herd and vaccination protocols are recommended. In this study, diagnosing the disease can be made rapidly by both clinicians and farmers, also putting the virus spreading persistent calves out of herd without losing time and a successful struggle can be made against BVD, are shown.

The Effect of Calf Gender on Milk Production in Seasonal Calving Cows and Its Impact on Genetic Evaluations.

Gender of the calf whose birth initiates lactation could influence whole lactation milk yield of the dam due to hormonal influences on mammary gland development, or through calf gender effects on gestation length. Fetal gender could influence late lactation yields because cows become pregnant at peak lactation. The effects of calf gender sequences in parities 1–3 were assessed by separately fitting animal models to datasets from New Zealand comprising 274 000 Holstein Friesian and 85 000 Jersey cows, decreasing to 12 000 and 4 000 cows by parity 3. The lactation initiated by the birth of a female rather than a male calf was associated with a 0.33–1.1% (p≤0.05) higher milk yield. Female calf gender had carryover effects associated with higher milk yield in second lactations for Holstein Friesians (0.24%; p = 0.01) and third lactations for Jerseys (1.1%; p = 0.01). Cows giving birth to bull calves have 2 day longer gestations, which reduces lactation length in seasonal calving herds. Adding a covariate for lactation length to the animal model eroded some of these calf gender effects, such that calving a female led to higher milk yield only for second lactation Holstein Friesians (1.6%; p = 0.002). The interval centering method generates lower estimates of whole lactation yield when Wood’s lactation curves are shifted to the right by 2 days for male calves and this explained the higher yield in female calves when differences in lactation length were considered. Correlations of estimated breeding values between models including or excluding calf gender sequence were 1.00 for bulls or cows. Calf gender primarily influences milk yield through increased gestation length of male calves, and bias associated with the interval centering method used to estimate whole lactation milk yields. Including information on calf gender is unlikely to have an effect on selection response in New Zealand dairy cattle.

Pre-weaning bovine respiratory disease in the cow-calf herd

Bovine respiratory disease (BRD) in beef calves prior to weaning is a problem for 1 in 5 cow-calf farms. Preweaning BRD is a costly problem for the cattle industry and a detriment to animal well-being. This is a perplexing health problem because ranch calves typically live in conditions of little stress and relative isolation, risk factors commonly associated with BRD in weaned calves. Some factors that appear to be related to BRD risk in pre-weaned calves are waning maternal immunity, loss of herd immunity in herds with short calving periods, activities that result in increased animal density, calf gender, and age of the dam. Collectively, these factors are related to the calf’s ability to resist infection and to opportunities for pathogen exposure. Activities such as commingling and weaning may have less impact on calf health if they are completed prior to or after calves are 3 to 5 months of age, thereby avoiding the period of greatest susceptibility. Vaccination programs intended to induce adequate immunity in calves prior to 90 days of age have shown some efficacy, but require further study.

Some Environmental Factors Affecting Birth Weight, Weaning Weight and Daily Live Weight Gain of Holstein Calves

The present study was conducted to determine some environmental factors affecting birth weight, weaning weight and daily live weight gain of Holstein calves of a livestock facility in Izmir, Turkey. The data on 2091 calves born between the years 2005-2010 were used to assess the relevant parameters. Effects of calving year, calving month, calf gender and the interaction between calving year and calving month on calves’ birth weights were highly significant. The overall mean of birth weights was 39.6±0.15 kg. In addition, effects of calving year, calving month, gender, birth weight, weaning age, calving year x calving month, calving year x gender and calving year x calving month x gender interactions on weaning weight (WW) and daily live weight gain (DLWG) were highly significant. The overall means of WW and DLWG were respectively found to be 79.7±0.20 kg and 525±2.5 g. A one kilogram increase in birth weight resulted in an increase of 0.89 kg in weaning weight and a decrease of 1.26 g in daily live weight gain. Prenatal temperature-humidity index (THI) affected birth weight of calves (R2=0.67). Increasing THI from 50 to 80 resulted in 3.8 kg decrease in birth weight.

Factors associated with the differential in actual gestational age and gestational age predicted from transrectal ultrasonography in pregnant dairy cows

The objective of the study was to determine (1) how gestational age predicted using transrectal ultrasonography related to actual gestational age derived as the number of days from the most recent artificial insemination date, (2) what factors, if any, were associated with the differential between the two measures, and (3) the association between this differential in gestational age and the likelihood of subsequent pregnancy loss, stillbirth, or calving dystocia. The data set contained 7340 ultrasound records from 6805 Holstein Friesian dairy cows in 175 herds. Ultrasonography assessment underestimated gestational age relative to days since last service by 0.51 days (standard error [SE]: 0.040), although the differential was less during embryonic development phase (i.e., ≤42 days of gestation; mean overestimation of 0.31 days) versus fetal development phase (i.e., >42 days of gestation; mean underestimation of 0.81 days). Predicted calving date calculated from ultrasonography was 1.41 days (SE: 0.040) later than the actual subsequent calving date and was, on average, 0.52 days later than predicted calving date, assuming a gestation length of 282 days. Parity of the dam (P < 0.05), stage of pregnancy (P < 0.001), and sex of the calf born (P < 0.001) were all associated with the differential in gestational age based on ultrasonography versus days since last service. No obvious trend among parities was evident in the difference between the methods in predicting gestational age. Ultrasonography underestimated gestational age by 0.83 (SE: 0.15) days in parity 5+ cows and underestimated gestational age by 0.41 (SE: 0.14) days in the first-parity cows. Relative to gestational age predicted from the most recent service, ultrasonography underestimated gestational age by 0.75 (SE: 0.13) days for heifer fetuses and underestimated gestational age by 0.36 (SE: 0.13) days for bull fetuses. The heritability of the differential in gestational age between the methods of prediction was low 0.05 (SE: 0.022), corroborating heritability estimates for most cow reproductive traits. Overestimation of gestational age using ultrasonography was associated with an increased likelihood of pregnancy loss (P < 0.001). Gender of calf born (P < 0.001), sire breed of calf (P < 0.001), and parity (P < 0.001) were all associated with gestation length. Gestation length was 1.27 days longer (SE: 0.01) for bull calves compared to heifer calves. Calves from beef sires had a longer gestation length than calves from dairy sires, and older parity cows had a longer gestation length than younger cows. The results highlight factors associated with differences in gestational age obtained from ultrasonography and insemination data and illustrate the value of ultrasonography for the prediction of calving date and pregnancy loss.

Sex of offspring influences metabolism during early transition period in dairy cows

Abstract. A study using 20 Holstein Friesian cows was conducted to investigate the influence of calf gender on metabolism during the transition period in dairy cattle. Blood samples were collected at three time points: 2–4 days prepartum (time 1), and 1 week and 2 weeks postpartum (time 2 and time 3 respectively). Serum samples obtained were analysed for total proteins, albumin, urea, glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). Depending on the sex of the offspring, cows were divided into two groups: Group 1 consisted of cows with heifer offspring (n = 12) and Group 2 consisted of cows with bull offspring (n = 8). A two-way repeated measures ANOVA and t tests for unpaired data were used to analyse the pattern of studied parameters and differences between the two groups. The results indicate differences in metabolic parameters between the two groups. These results highlight the importance of considering fetal sex as a factor that influences maternal metabolism during the early transition period in dairy cows.