Calf Gender Research Articles

A novel production profile classification system for incoming calves that predicts feedlot growth performance

Context Mitigating financial risk in the feedlot environment is an ongoing occurrence, and good production is a key risk mitigator. However, production protocols are based on historic averages because of the inability to predict growth potential of incoming calves. Production profiling of individual incoming feeder calves could address these limitations. Aims The aim of this study was to establish criteria for optimal sorting of incoming feeder calves into various cattle groups in a feedlot that maximises feedlot profit. Methods South African feeder calves (n = 436) were classified into four production-profile (PP) categories according to a predetermined set of phenotypic traits: PP 3 (n = 72) representing feeder calves with the poorest feedlot growth potential, PP 2− (n = 191) with below-average potential, PP 2+ (n = 139) with above-average potential and PP 1 (n = 34) with above-average feedlot growth potential. After combining the data of PP 2− and PP 2+ into PP 2, mixed modelling of economically important feedlot growth traits (average daily gain (ADG), carcass ADG, and carcass exit weight) was performed to evaluate the effect of PP classification (PP 1 and PP 3), while adjusting for potential confounding effects such as starting weight (entry weight) and gender. Key results Carcass weights for calves with a PP classification of 3 and 1 were 15.54 kg less (P < 0.000), and 11.34 kg more (P = 0.007) respectively, than those with a PP classification of 2 (261.27 kg, 95% CI 257.94–264.57), after adjusting for entry weight, calf gender and the random effect of the feeding pen. Similar to carcass weight, calves with a PP 3 classification were outperformed by other classifications in all the measured traits (P < 0.05). Conclusions This is the first report demonstrating the ability of subjective production-profile classification to predict growth performance of individual feeder calves. Implications The opportunity of the PP classification system lies in value-based procurement of incoming feeder calves based on their growth potential at the start of the feeding period, and then to use technology to improve and finalise the current subjective PP classification system.

The Association between Charolais Cows' Age at First Calving, Parity, Breeding Seasonality, and Calf Growing Performance.

The objective of this study was to evaluate the impact of cows' calving ages and newborn calf body weight on the pre-weaning growth rates of calves under the farming conditions of a northeastern European country. The females were purebred Charolais cows that calved between 2019 and 2022. A total of 130 calves (bulls = 76; heifers = 54) were observed during the evaluation. The investigation showed that, based on gender, bulls had a 4.28% higher birth weight than heifers (p < 0.05). The gender of the calves affected their weight, indicating that newborns bulls were significantly heavier. Calf gender affected calf growing performance. Male calves' weight gain was higher than that of females in the time before weaning (210 days). The highest gain of bulls was observed from 211 days to 365 days after birth. The average daily weight of male calves during this period was 6.16% (p < 0.001) higher compared to the period up to 210 days after birth. Heifers had a higher daily weight in the period up to 210 days after birth, and the daily weight gain was 12.9% (p < 0.001) higher in this period compared to the period from 211 to 365 days after birth. We observed a higher weight gain in calves from mothers with a higher number of calvings. Being born from cows with four or more calvings had a significant effect on the weight gain of calves in the period up to 210 days (p < 0.05). In the period up to 210 days, the weight gain of calves born from cows with two calvings was the lowest and was 9.79% lower compared to calves born from cows with four and more calvings (p < 0.05). The best weights were obtained from calves born in the spring and autumn seasons. Calves born in spring, summer, and autumn differed in weight by 0.37 kg. The calves of cows that were inseminated in the autumn season had the highest gain in the period up to 210 days and also from 210 to 365 days (p < 0.05). In our study, significantly higher average birth weight of calves was detected in autumn compared to summer and winter (p < 0.05). Also, the highest gain was found from 211 to 365 days after birth in the summer season, but the difference was only 1.47% (p < 0.05).

Effects of Sexed and Conventional Semen Use and Calf Sex on Milk Yield Parameters, Body Weight and Milk Electrical Conductivity in Holstein Cows

This study was designed to determine the effects of semen type and calf gender on milk yield parameters, milk electrical conductivity and milk flow values and postpartum maternal body weight. A total of 265 Holstein cows in the first lactation were used in the study. The effect of sperm type on maternal body weight levels after calving and milk electrical conductivity values was significant (P0.05). Heifers inseminated with sexed semen had higher 100-days milk yield, milk peak yield and postpartum maternal body weight in the first lactation. Milk peak duration was higher in heifers inseminated with conventional semen (P0.05). In conclusion, heifers inseminated with sexed semen had higher maternal body weights, 100-days milk yield, milk peak yields and milk electrical conductivity levels in the first lactation than inseminated with conventional semen

57 Relationship between Proportion ofBos indicus Genetics of Dams and Calf Performance from a 31-Year Multibreed Herd Dataset

Abstract This is a 31-year retrospective cohort study aiming to evaluate the relationship between the proportion of B. indicus genetics of crossbred dams and the weaning weight of their calves. Our hypothesis was that crossbred dams with intermediate degree of B. indicus genetics wean heavier calves than those with low-to-high degree of B. indicus genetics at the subtropical condition. The cow-calf pairs (n = 4,901) were in six evenly distributed breed groups according to the proportion of Brahman: G0–19%, G21–34%, 38%, G41–59%; G63–78% and G81–100%. Dams reared contemporaneously were undergone to controlled breeding seasons where the six breed groups of dams and sires were reciprocally mated. Non-adjusted and 205d-adjusted weaning weight of calves were considered as dependent variables and analyzed using MIXED procedure of SAS 9.4. The following independent variables were included in the model as fixed effects: parity category order (primiparous, secundiparous and pluriparous), calving period (0-30d, 31-60d, 61-90d and 91-120d), gender of calf (male or female) and breed group. Year was included as a random effect. All possible interactions were tested and only those with P &amp;lt; 0.20 remained in the final model. Most of all, for the non-adjusted weaning weight, the breed group effect (P &amp;lt; 0.001) varied according to the calving period. Dams calving after 30d of calving season weaned the lightest calves. However, the magnitude of such losses was variable within breed groups. Calves from G0-19% and G81-100% of dams were the most and least impacted by calving period, respectively. The difference on weaning weight between calves born at 0-30d and 91-120d was 60kg for G0-19% of dams and 30kg for G81-100% of dams. For every other breed group, this difference ranged from 45kg to 55kg. In spite of such interaction effect, calves from G0-19% and G81-100% of dams were lighter (230.4 and 225.0 kg, respectively; SEM: 3.4) than any other breed group (238.3 to 242.5 kg). For the 205d-adjusted weaning weight, there was a breed group effect (P &amp;lt; 0.001), regardless of calving period. Lighter calves were still weaned from G0-19% and G81-100% of dams (214.9 and 206.5 kg, respectively, SEM: 2.8) compared with any other breed group (223.4 to 227.6 kg). Thus, crossbred dams with intermediate degree of B. indicus genetics weaned the heaviest calves, probably as result of outbreeding enhancement provided by the adaptability of B. indicus to the tropics and productivity of B. taurus.

Dry Period Length in Dairy Cattle: II. Influence on Calf Survival and Growth Performance

This study was conducted to investigate the effects of dry period length (DPL) on survival rate, gender, growth performance, mortality of Holstein calves. Data belonged to 800 Holstein cows in different parities (2nd, 3rd and ≥4th) and 800 calves delivered by these cows. DPL were classified in 5 categories (≤40, 41-50, 51-60, 61-70, ≥71 days). Calves were weighed and body dimensions (body length, wither height, hearth girth) at birth and 6th months of age. There were significant relationships between DPL and calf gender (P

Molecular evaluation of Cryptosporidium spp. among breeding calves of Lorestan province Western Iran.

Cryptosporidium spp. are opportunistic intestinal protozoans with global distribution and are of great importance as zoonotic protozoans are common to humans and domestic animals, including cattle and calves. Identification and detection of parasite species using precise methods including molecular methods can be an effective step in treating and controlling parasites. This study aimed to investigate the prevalence of Cryptosporidium among breeding calves of Khorramabad city, Lorestan province, Western Iran, using PCR. The faecal samples were taken from 181 healthy and diarrhoeal calves and after the Ziehl Neelsen Acid-fast staining and microscopic evaluation, the genomic DNA was extracted for molecular evaluations. To detect Cryptosporidium species, specific primers targeting the SAM-1 gene of Cryptosporidium and a commercial master mix were used for PCR. Out of 181 faecal samples of breeding calves in Khorramabad city, 9 samples (5%) were positive for Cryptosporidium spp. using the PCR method. Statistical analysis of the data showed that there was no significant statistical relationship between Cryptosporidium infection of the calves and variables of age, breed, type of water consumption, clinical signs of diarrhoea, and sampling location, while parasite infection had a significant relationship with calf gender so that all Cryptosporidium positive samples were from male calves (p ≤ 0.05). Considering the presence of Cryptosporidium infection, the region's traditional grazing system, and the close relationship between livestock and humans, there is a possibility of human infection in the region. So preventive measures such as periodic animal testing with sensitive and accurate diagnostic techniques including PCR, pharmacological treatment of livestock, water hygiene and the use of industrial grazing instead of traditional grazing to improve the hygiene of food consumed by livestock are recommended.

Reproduction record of captive Sumatera elephant (Elephas maximus sumatranus) at Way Kambas National Park, Indonesia

This research aims to determine reproductive data on Sumatran elephants (Elephas maximus sumatranus) in the ETC and ERU of Way Kambas National Park, Indonesia during 1988-2021. Data recorded from the elephant population at both locations (ETC and ERU) includes the number, gender of elephants, elephant calves, ages and birth dates. Calving intervals and service periods were calculated from calving records of cows with a minimum parity of two. Data collection produced data on 47 elephant calves from 13 female elephants with at least twice the parity and 12 primiparous cows. Elephant reproductive records at ETC and ERU were: age (37.44 ± 9.03 vs. 29.75 ± 3.30 years), parity (2.78 ± 1.09 vs. 2.50 ± 0.58), and age at first birth (18, 11 ± 3.92 vs. 17.75 ± 0.50 years). While the calving interval was 1857.56 ± 870.81 vs. 1833.00 ± 305.18 days, and service period respectively 1229.44 ± 846.18 vs. 1210.50 ± 283.59 days, respectively. It can be concluded that the calving interval and service period for captive elephants at ETC and ERU were not much different and were within the normal range. Young cows showed better reproductive efficiency than older cows. Monitoring calves is very important. Further assistance is needed to improve elephant mobile veterinary services, increase diagnostic laboratory capacity, and educate camp managers, veterinary assistants, and mahouts about elephant diseases, their monitoring and treatment. In addition, the use of reproductive technology such as monitoring ovulation using ultrasound and carrying out artificial insemination was expected to increase reproductive efficiency.

Reproduction record of captive Sumatera elephant (Elephas maximus sumatranus) at Way Kambas National Park, Indonesia

This research aims to determine reproductive data on Sumatran elephants (Elephas maximus sumatranus) in the ETC and ERU of Way Kambas National Park, Indonesia during 1988-2021. Data recorded from the elephant population at both locations (ETC and ERU) includes the number, gender of elephants, elephant calves, ages and birth dates. Calving intervals and service periods were calculated from calving records of cows with a minimum parity of two. Data collection produced data on 47 elephant calves from 13 female elephants with at least twice the parity and 12 primiparous cows. Elephant reproductive records at ETC and ERU were: age (37.44 ± 9.03 vs. 29.75 ± 3.30 years), parity (2.78 ± 1.09 vs. 2.50 ± 0.58), and age at first birth (18, 11 ± 3.92 vs. 17.75 ± 0.50 years). While the calving interval was 1857.56 ± 870.81 vs. 1833.00 ± 305.18 days, and service period respectively 1229.44 ± 846.18 vs. 1210.50 ± 283.59 days, respectively. It can be concluded that the calving interval and service period for captive elephants at ETC and ERU were not much different and were within the normal range. Young cows showed better reproductive efficiency than older cows. Monitoring calves is very important. Further assistance is needed to improve elephant mobile veterinary services, increase diagnostic laboratory capacity, and educate camp managers, veterinary assistants, and mahouts about elephant diseases, their monitoring and treatment. In addition, the use of reproductive technology such as monitoring ovulation using ultrasound and carrying out artificial insemination was expected to increase reproductive efficiency.

The effect of calf gender on milk lactation traits and lactation gain of Holstein and Simmental cows

Considering the challenging market conditions for dairy farms, calf gender management should be one of the tools used to increase profitability. The objective of this paper was to examine the effect of calf gender on lactation milk traits in Holstein and Simmental cows. Holstein cows that calved a female calf had a higher milk yield (p&lt;0.0001) and lower milk fat and protein content (p&lt;0.01) in the first lactation. The favourable effect of female calf on milk yield was also found in the second lactation of Holstein cows (p&lt;0.0001). Simmental cows that calved female calves in the first and the second lactation also had higher milk yield and lactation gain, however the differences were not significant. Although no statistically significant effect of calf gender on milk yield was determined in the Simmental population, indications of positive effect of female calf gender on lactation milk yield impose the need for further research. Using gender selected semen as a tool for calf gender management could enable to increase the milk yield of Holstein cows and the profitability of Holstein farms as well.

ANALYSIS OF THE QUALITY OF SEXED BULL SEMEN BY COMPUTER-ASSISTED SEMEN ANALYSIS-CASA

The quality of the ejaculate is determined by examination of the macroscopic (volume, density, color, smell) and microscopic properties of the sperm (concentration of spermatozoa in 1 ml and the total number of spermatozoa in the ejaculate, morphology, vitality, mobility of spermatozoa and integrity of the acrosomal membrane). Computer assisted semen analysis (CASA) is an automated system that measures sperm motility, kinetics and concentration. Some systems have modifications for evaluating the morphological characteristics of spermatozoa. The assessment of morphological characteristics of spermatozoa can be performed by microscopic examination (presence of normal and pathological spermatozoa, integrity of sperm cell membrane and acrosome abnormalities). The Blom method, as the method of the staining of the sperm smear with eosin and nigrosine, determines the vitality of the semen. In modern cattle breeding, sexed bull semen (semen from which desired gender of calf will be delivered) is used more and more. The analysis of sexed semen, and especially the comparison of its quality with conventional semen, is an increasingly common requirement on the cattle production market. The aim of the work was to examine the quality of 15 samples of sexed bull semen, originating from imports. The tests included determination of concentration and kinetics using the CASA system, as well as assessment of vitality and morphological characteristics by Blom staining. The average sperm concentration in 15 samples was 19.61x106/ml of ejaculate. The total motility was 39.42%, while the number of immobile spermatozoa in the samples was 60.58%. The number of morphologically normal spermatozoa varied from 2.91x106 to 6.11x106, and the percentage of pathological spermatozoa from 8% to 28%. Taking into account the results obtained and the absence of standards related to sexed semen in the currently valid Regulation on the manner of marking of sperm, the manner of keeping records on sperm production, as well as on the conditions that must be met by animal sperm in terms of quality (Official Gazette of the Republic of Serbia, 38/14), it is necessary to carry out more frequent analyzes of sexed semen using the CASA method in order to obtain values that would become an integral part of the Regulation and thereby facilitate the manipulation of sexed semen on the market.

PH and ferning score of cervical mucus related to gestation and calf gender of Holstein Friesian crossbreed cows

This study aimed to compare the ferning score based on the pH of the cervical mucus and its relation with gestation and the calf gender of cows. Ten Holstein Friesian crossbreed cows which were detected in estrus and about to be artificially inseminated, were used for this study. Sample of cervical mucus was collected using Metricheck for pH and ferning observations. Pregnancy diagnosis was conducted two months after insemination, and the gender of the calves was recorded at parturition. This study indicated that cervical mucus pH did not affect the ferning characteristics, ferning score, and pregnancy of cows. However, higher ferning scores tended to result in the pregnancy of cows. Also, alkaline pH tended to result in male calves and vice versa. Further study is needed with a more significant number of samples related to the application of ferning display as an indicator of estrus to obtain a higher pregnancy rate.

Application of artificial intelligence methods for bovine gender prediction

This study investigates determining the gender of calves using some artificial intelligence (AI) techniques. Gender identification is important in animal breeding, focusing on the desired outcome and planning. The data used to determine the gender of calves were the speed, magnitude, and density of the bull's semen. The analysis of the related studies showed that there was not a study on gender prediction of bovine with the application of AI methods. In this study, fuzzy logic (FL), artificial neural networks (ANN), support vector machines (SVM), and random forests (RF) were used. The efficiency of these approaches was verified by statistical analysis parameters such as accuracy, specificity, sensitivity (recall), precision, and F-score. The FL, ANN, SVM, and RF models had 84%, 96%, 97%, 99% accuracy, 93.75%, 96.88%, 100%, 100% sensitivity, 66.66%, 94.44%, 92.31%, 97.30% specificity, 83.33%, 96.88%, 95.31%, 98.44% precision results, respectively. Application of these AI techniques for prediction bovine gender proves that these methods may be used by semen breeders as supporting information tools. In particular, it was observed that the RF method yielded the highest accuracy results.

The Effect of Insemination Time, Season and Insemination Method on Calf Gender in Holstein Cattle

The aim of this article is to determine the effect of insemination time, season and insemination method on calf gender in cattle. In the study, 792 records of inseminations and calving data between 2010-2019 were evaluated. The onset of estrus was determined based on mounting behavior. Inseminations were carried out between 0-6, 6-12, 12-18 hours after the onset of estrus. At the same time, inseminations were evaluated according to the seasons. Of the inseminations, 582 were artificial insemination and 210 were natural insemination. While insemination time and insemination method had no effect on calf gender, seasonal effect was found to be significant. Keywords: Holstein, Insemination Time, Gender DOI: 10.7176/JSTR/7-10-03

PSXIII-23 Influence of reproductive technologies on post weaning calf performance and carcass characteristics

Abstract The experiment objective was to evaluate the impact of assisted reproductive technologies on post weaning calf performance. Calves born following various reproductive treatments (synchronized natural service and synchronized AI) in 10 herds over 2 years were fed to reach a target backfat (BF) of 1.27 cm, sent to harvest, and carcass data collected. Calves were classified into calving groups as natural service born early (NS-Early, n = 189), natural service born late (NS-Late, n = 203), or AI sired born early (AI-Early, n = 116). Data were analyzed using the MIXED procedure in SAS with calving group, year and calf gender in the model. Weaning weights were similar between AI-Early and NS-Early; however, earlier born calves (AI-Early and NS-Early) were heavier (P &amp;lt; 0.0001) than NS-Late. AI-Early calves had heavier finished bodyweight (622.2 kg: P = 0.0024) compared to NS-Early (601.4 kg) and heavier HCW compared to both NS-Early and NS-Late (P &amp;lt; 0.01). NS-Early calves reached 1.27 cm BF in fewer days than AI-Early (261 d and 275 d, respectively; P &amp;lt; 0.01) with NS-late requiring the most days on feed to reach the same endpoint (296 d, P &amp;lt; 0.01). No differences in Quality Grade, Yield Grade, REA, marbling, or BF were detected between AI-Early, NS-Early, and NS-Late, or between early- and late-born calves (P &amp;gt; 0.38). Late-born calves required 29 more days on feed (P &amp;lt; 0.001) to reach 1.27 cm BF resulting in greater final bodyweight compared to early-born calves (625.5 kg and 612.8 kg, respectively; P = 0.04); however, hot carcass weights were similar between early- and late-born calves. Reproductive technologies that increase the number of calves born early in the calving season increased weaning weight and post weaning growth performance, but compared to high quality natural service sires, AI did not improve carcass characteristics.

Pregnancy and offspring sex ratio following insemination with SexedULTRA and conventional semen in cows in a commercial beef operation.

Pregnancy rate per AI (PR/AI) and breeding season pregnancy rates between insemination with sexed semen (SS; at 18hr after the onset of oestrus) and conventional semen (CS; at 12hr after the onset of oestrus,) and offspring gender ratio between two groups were compared. Angus cross cows (n=686, during 2019 and 2020 breeding seasons) were oestrus-synchronized using Select-Synch + CIDR protocol and were observed thrice daily for oestrus until 72hr after PGF2α administration. Cows expressed oestrus (n=513) were inseminated with either SS (n=246; SexedULTRA 4M™; y chromosome-bearing sperm) or CS (n=267). Cows (n=173) that failed to express oestrus at 72hr after PGF2α received 100μg of GnRH and CS insemination concomitantly. Two weeks later, cows were penned with natural service sires (bull:cow ratio 1:25) for 45days. Pregnancy was diagnosed 30days after bull removal. Calves' gender was determined at birth. For cows that expressed oestrus, PR/AI did not differ (p>.1) between SS (65.0%) and CS (66.7%) groups. The overall PR/AI differed (p<.05) between SS (65.0%) and CS (56.4%) groups. The natural service PR differed (p<.001) but breeding season PR (p>.05) did not differ between SS vs. CS groups. Bull:heifer gender ratio following AI was 88:12 and 52:48 for SS and CS groups, respectively, with an overall 66:34 ratio. Bull:heifer gender ratio for the two breeding seasons was 79:21 and 52:48 for SS and CS groups, respectively, with an overall 62:38 ratio. In conclusion, the fertility of SS insemination at 18hr after onset of oestrus was 97% of CS insemination at 12hr after onset of oestrus. Though breeding season pregnancy did not differ between SS and groups, preferred calf gender was 25 percentage points greater for SS over CS application. The gender accuracy was 88%.

Relationship of molecular breeding value for beef tenderness with heifer traits through weaning of their first calf

Polymorphisms in μ-calpain (CAPN1) that beneficially associate with beef tenderness are reported to antagonistically associate with calving day in beef heifers and post-partum interval to estrus in beef cows. We, therefore, hypothesized that a molecular breeding value for slice shear force, calculated based on CAPN1 and calpastatin (CAST) genotypes, would demonstrate an antagonistic relationship between genomically predicted slice shear force and ordinal calving date in replacement beef heifers. A secondary objective of this study was to evaluate the association of a polymorphism in diacylglycerol O-acyltransferase (DGAT1) with reproductive traits in beef heifers. One hundred eighty-seven MARC III heifers (¼ Angus, ¼ Hereford, ¼ Red Poll, and ¼ Pinzgauer) that had been selectively bred to increase the frequency of these polymorphisms were submitted for monthly ultrasound exams beginning at 333 d of age and continuing until the start of breeding to determine pubertal status. At the last exam before breeding, all antral follicles were counted, and the length and height of each ovary was measured to determine if genomic selection for slice shear force associated with ovarian follicle number. Calving date, calf gender, and calf birth weight were recorded at parturition. Regression analysis of the molecular breeding value for slice shear force of the heifers on ordinal calving date indicated no association between genomic prediction of tenderness and calving date (P = 0.16); however, there was a tendency for age at puberty to be delayed in heifers as genetic merit for tenderness improved (P = 0.09). The results of the present study indicate that within experimental precision, selecting for tenderness using genomic predictions had minimal or no antagonistic association with reproductive performance in heifers. Further analysis of reproductive performance as cows is needed within this population but applying these genetic markers to select for tenderness in steers does not antagonize reproductive traits influencing conception or first calf birth date and birth weight in replacement beef heifers.

Weaning at 30, 75 and 180 days: Comparison between immune responses of beef calves

The interruption of the maternal-filial bond in young calves can alter the physiological responses due to increased stress at this moment. Therefore, we aimed to analyze the association between age at weaning and the immune responses of 64 beef calves weaned abruptly. The animals were distributed in three weaning (W) treatments: hyper-early (W30), early (W75) and conventional (W180). The treatments agree with the weaning ages used in cow-calf systems in South America. Blood samples were collected of all experimental animals on the day of weaning and days 1, 2 and 7 post-weaning day of the three treatments. Blood samples were used to analyze hematological variables, total plasma proteins (TPP), fibrinogen, serum amyloid A protein (SAA) and cortisol. The variables analyzed were influenced by the sampling day (P < 0.001) and the calf gender (P < 0.05), and an interaction between treatment x sampling day was observed. Over the study period, high serum cortisol levels were observed for W30 calves. The serum amyloid A protein was significantly influenced by sampling day. When compared to W180 calves, W30 and W75 animals showed prolonged concentrations in plasma fibrinogen. In addition, they presented neutrophilia and lymphopenia during the 180–187 days period, which resulted in a greater neutrophil:lymphocyte ratio (N:L ratio). Calf gender resulted in changes in the number of blood leukocytes (P < 0.05). This result provides an alert for weaning at an early age, indicating that different management strategies must be tested to minimize physiological instabilities in critical periods of the life of animals.

Estimates of Genetic Variation for Angus Gestation Length

Abstract The objective of this study was to estimate variance components for gestation length within the American Angus breed. Data (n = 148,649) from the American Angus Association, containing cattle born between 2000 to 2020, were used for the analysis. Based on a cow’s reproductive biology, gestation length records were determined acceptable if between 266 and 290 days (n = 114,857). Gestation length mean and standard deviation were 278.6 and 4.6 days, respectively. Average Information Restricted Maximum Likelihood (AIREML) was used to estimate variance components for the gestation length. A single trait animal model included random effects of direct and maternal additive genetic variance and fixed effects of dam age rounded to the nearest year, calf gender and contemporary group. Contemporary group was determined as herd, year of birth and season of birth combinations. Contemporary groups containing less than five animals were excluded from analysis. Phenotypic variance for gestation length was estimated at 18.9. Direct and maternal heritability estimates for gestation length were 0.59±0.01 and 0.10±0.01, respectively. Further analysis evaluated the fixed effects of year and dam age on gestation length. From 2000 to 2020, an increase in one year decreased (P &amp;lt; 0.01) gestation length by 0.09 days. Gestation length differed (P &amp;lt; 0.01) by age of dam. Gestation length LSMEANS for 2, 3, 4, 5, 6, 7 and 8 year old cows were 277.7, 278.6, 279.0, 279.2, 279.3, 279.5 and 279.6, respectively. Heritability estimates within Angus breed suggest gestation length has a high capacity for genetic change. Results suggest gestation length has decreased over the past two decades and is shorter in younger cows.

Using Pelvic Areas and Linear Body Measurements in the Selection for Reduced Dystocia Rates in Sussex Heifers

Background: Dystocia in cattle is a global problem which causes many health issues and economical losses in the beef cattle industry. However, to the greatest of our knowledge, use of pelvic areas and linear body measurements in South African Sussex heifers has not yet been reported on literature. Hence, the aim of this study was to use pelvic areas and linear body measurements in the selection of replacement Sussex heifers to reduce dystocia amongst heifers, while improving ease of calving.Methods: One hundred eighty-six first calf Sussex heifers 24 months old, weighing approximately 437 kg were used for this study. A number of six, two-year-old bulls, weighing approximately 800 kg were used for mating the 135 heifers during the first trial with a bull to cow ratio of (1:35; 1:35, 1;35 and 1:30). The second trial consisted of 51 heifers with a number two, two-year-old bulls respectively, with a bull to cow ratio of (1:30 and 1:21).Result: A significant correlation between calving eases score and calf gender, r = -0.35 was revealed. The chances of a heifer to experience dystocia were more when a male calf was born. Birth weight, revealed that higher the birth weight higher the probability of a heifer to experience dystocia. It can be concluded that pelvic measurements in Sussex heifers may be a valuable tool to reduce dystocia.

Impact of Offspring Sex and Dam’s Pre-partum Vaccination on Colostrum Composition and Blood Hormones in Egyptian Buffaloes

An The aim of the present research was to determine the effect of both the gender of the new-born calf and the pre-partum vaccination status of the dam (ScourGuard-4K) on the chemical composition and some biological parameters of the colostrum. Blood serum was collected from four groups of pregnant dams (four animals in each group) during the dry period (vaccinated buffalo dams pregnant with a male fetus, vaccinated buffalo dams pregnant with a female fetus, unvaccinated buffalo dams pregnant with a male fetus, and unvaccinated buffalo dams pregnant with a female fetus), in the pregnancy period, at the giving-birth period and after 24 hours of postpartum. The levels of insulin-like growth factor hormone (IGF-1) and immunoglobuline G (IgG) were calculated in the maternal blood serum at the assigned periods. Colostrum samples were collected at the birth time and 6, 12, 24, 48, and 72 hours after birth for measuring the chemical composition of the colostrum, as well as levels of IgG and IGF-1. Results of the current study showed that colostrum of dams that gave birth to male fetus had a richer content of IgG and IGF-1 levels and a higher percentage of total solids, solids-not-fat, total protein, fat, and lactose. Additionally, vaccination improved the same colostrum components except for IGF-1, which was not positively influenced by the vaccination. Generally, colostrum components were the highest at the birth time, then it decreased gradually up to 72 hours after the birth except that for the percentage of fat and lactose which showed gradual increases up to 72 hours to reach the normal composition of milk.