Insemination Period Research Articles

Effects of calving interval of dairy cows on development, metabolism, and milk performance of their offspring

Extending the voluntary waiting period (VWP) for insemination in dairy cows is of interest as a strategy to reduce the frequency of calving events and inseminate at a moment with fewer fertility problems. Little is known about the calves born from dams with a different VWP followed by a different calving interval (CInt). The objective of the current study was to identify the effect of dam's CInt on body condition, metabolic status, and milk production of their offspring from birth until 100 DIM of the offspring's first lactation. Holstein-Friesian dairy cows (n = 154, 41 primiparous, 113 multiparous) were blocked according to parity, milk yield, and SCC and randomly assigned to a VWP of 50, 125, or 200 d. Female calves (n = 62) from cows with different CInt were monitored from birth until their first calving event as heifer. Certain dams were not successfully inseminated soon after the planned VWP, resulting in differences between the intended VWP and the actual CInt. Calves were regrouped according to their dam's actual CInt (CInt_1: 324-408 d; CInt_2: 409-468 d; CInt_3: 469-586 d). The dam's CInt did not affect calf birth weight. From birth to weaning, the calves born to dams in CInt_1 had a higher plasma nonesterified fatty acids (NEFA) concentration (0.34 mmol/L; CI: 0.30, 0.37) than CInt_2 (0.28 mmol/L; CI: 0.26, 0.31) and CInt_3 (0.26 mmol/L; CI: 0.24, 0.29) calves. Calves born to dams with a shorter CInt (CInt_1) had greater IgG and IgM against keyhole limpet hemocyanin (KLH) than CInt_3 (IgG: 6.05 ± 0.30 vs. 4.64 ± 0.30; IgM: 6.45 ± 0.17 vs. 5.89 ± 0.16, respectively; mean ± SE) before weaning. After weaning till calving, CInt_1 calves tended to have greater plasma NEFA concentration than CInt_3-calves. During the first 100 DIM, a longer CInt of the dams resulted in lower plasma IGF_1 (CInt_2), lower milk lactose (CInt_3), and lower fat- and protein-corrected milk (FPCM; CInt_2) in offspring, compared with shorter CInt of the dams (CInt_1). Collectively, a longer CInt in dams did not affect birth weight of their calves or BW during the weaning or rearing phase. From birth till weaning, a longer CInt in dams resulted in less anti-KLH IgG and lower plasma NEFA concentration in plasma of the calves. During the first lactation of their offspring, a longer CInt in dams can result in a lower plasma IGF_1 and FPCM during the first 100 DIM, although effects were not present in all CInt categories.

The impact of environmental temperature on ewe reproduction, adaptive responses during insemination, and productive characteristics of the lambs obtained from them

The reproductive function of ewes and the development of their offspring are largely influenced by their clinical condition and the temperature of the environment. The maximum temperature values have significantly increased over the last two decades, making climate change a pressing issue for sheep breeding worldwide, including Ukraine. The consequences of exposure to high temperatures of the outside air, above all, in the mating season, can be marked by a significant increase in the heat load on the body of the brood stock, a decrease in clinical indicators and reproductive capacity. On the other hand, the current understanding of how these components interact is insufficient, which conditions the relevance of this work. In order to determine the effective terms of insemination of sheep in the mating season of 2021, taking into account the terms of insemination and the characteristics of the outside air temperature, three technological groups of ewes were formed, which were in the same flock and were artificially inseminated with freshly obtained sperm from the same breeders in August–September: from August 15 to August 27; from August 28 to September 9 and from September 10 to September 21. It was discovered that ewes inseminated between August 28th and September 9th were less adaptable to environmental conditions, experiencing increased daily fluctuations of body temperature, pulse and breathing rates, stillborn lambs, cases of abortion, and decreased preservation of young animals, including ewe lambs, which are highly valuable in breeding – by 15.8% and 10.9% concerning the initial and final phases of the insemination period. However, the young lambs born from ewes inseminated between August 15th and August 27th had the highest survival rate until weaning due to better survival of ewe lambs compared to those inseminated during later phases of the mating season against the background of a lower percentage of output of rams until the moment of weaning against ewes that were inseminated from August 28 to September 9. It has been shown that the growth rate of lambs during early postnatal development varies depending on the timing of their mothers' insemination. Ewes inseminated between August 15th and 27th produced lambs with the highest weight at 90 days, reaching 26.81 and 24.18 kg, respectively; 20.1% and 26.8% more than rams, and 19.1% and 18.8% more than female lambs whose mothers were inseminated in the middle and at the end of the breeding season. A similar picture is characteristic of the average daily growth values. It was determined that the formation of clinical indicators, and above all, the body temperature of young animals born from mothers fertilized at the beginning and in the middle of the mating season, was the most intense. The results of this study made it possible to understand the adaptive mechanisms of the response of sheep to changes in environmental temperature, which will be useful in future investigations to determine its effect on the thermopotential and clinical condition of lambs during the first day after birth, which is the most critical.

P-147 Comparison of Fertilization rate, Blastocyst rate and number of Top Quality Embryo with Short (2 hours) and conventional co-incubation (16-20 hours)of gametes

Abstract Study question Does short Co-incubation of gametes increase quality and quantity of embryos by eliminating suboptimal culture conditions like increased reactive oxygen species seen with overnight incubation? Summary answer Although short co-incubation group had lower fertilization rate it yielded more blastocysts and top quality embryos on day 3 and 5. What is known already Successful fertilization can occur 20 minutes after co-incubation of gametes. Incubation time of 18 hours has been used as a routine combining it with fertilization check. However it is known to produce reactive oxygen species (ROS) released by cellular metabolism of inseminated sperms which affect embryo development and cause zona pellucida hardening. Studies have shown reduced oocyte exposure time caused improved embryo development. However, other studies have reported lower fertilization rate with no such advantage. Not many studies have been done with short co-incubation without denudation which might allow optimum fertilization and at the same time prevent increase in ROS. Study design, size, duration It is prospective controlled study. 62 patients (921 oocytes) were recruited. The sibling oocytes from each patient were divided into 2 groups. Group 1( Control) conventional co-incubation of gametes (16-20 hours) and group 2 short co-incubation (2 hours) after which they were transferred to a fresh media. Study period was from January 2022 to September 2022. Institutional scientific and ethical committee approval and written consent of couple taken. Participants/materials, setting, methods Couples undergoing IVF in tertiary infertility centre were recruited. Women under 40 years who yielded minimum 6 oocytes and males with normal semen parameters were included. Those excluded were couples requiring ICSI, poor responders with <6 oocytes retrieved and couples requesting day 3 transfer. Primary outcome was number and percentage of top quality embryos (TQE) and blastocyst rate. Secondary outcome was fertilization rate. SPSS used for data analysis. Results expressed as mean +/-SD or percentage Main results and the role of chance Total oocytes studied 921 in 62 patients. Since control and study group were from sibling oocytes of same patient they were matched for age BMI, ovarian reserve, stimulation protocol, semen parameters and laboratory handling. Extra oocytes in odd number oocytes were randomized to 2 groups. Mean age was 31 years. Group 1 had 425 out of 455 (93.4%) oocytes fertilized and group 2 had 412 out of 466 (88.4%) oocytes fertilized (p value<0.05). TQE on day 3 were 251 of 425 (59.05%) fertilized in group 1 and 277 of 412 (67.23%) fertilized in group 2 (p = 0.013). Blasts formed in group 1 were 41 of 425 (9.64%) and in group 2 were135 of 412 (32.76%) (p = 0.001). TQE on day 5 were 28/425 (6.67%) in group 1 (0.45 +/−0.9 blasts per patient) and 95/412 (23.05%) in group 2 (1.53+/-1.86 blasts per patient). (P = 0.001) Percentage of grade 2 embryos on day 3 and 5 was significantly higher in short co-incubation group. Although fertilization was higher in group 1 many embryos did not progress beyond day 2 as both grade 1 and 2 embryos on day 3 and 5 were less in percentage and absolute per patient value in this group. Limitations, reasons for caution Pregnancy rate could not be calculated as some patients wanted 2 embryos transferred and one group had only a single blast. For their transfer blasts were taken from both groups. Very poor responders (<6 oocytes) not studied. Further studies needed to establish best time duration for short co-incubation (1-8 hours) Wider implications of the findings Practice for co-incubation after 16-20 hours needs to be re-evaluated. The study shows more top quality blasts with short insemination period. This may become the practice if it is established by further studies assuming that TQE are known to yield better pregnancy rates and IVF results Trial registration number not applicable

Effect of Anti-Mullerian Hormone, Metabolic Profile and Mineral Levels at Transition Period On The Calving – Conception Interval in Cows

The transition period in dairy cows is generally accepted as the period covering 3 weeks before calving and 3 weeks after calving. The aim of the study was to compare the profiles of β-hydroxybutyrate, calcium, magnesium, phosphorus, total cholesterol, total protein, triacylglycerol, free glycerol, serum lipid and serum protein with Anti-Mullerian Hormone (AMH) in dairy cows in the transition period, and to determine whether AMH to examine whether it can be used as a marker in the next insemination period. The cows whose blood samples were taken were followed up and it was determined that they became pregnant at the insemination and the study was terminated. According to the results obtained; It was determined that BHB and free glycerol, which are important markers of negative energy balance (NEB), have an effect on AMH concentration. However, it was determined that the concentration of magnesium and the ratio of cholesterol ester in serum total fat did not change much during the transition period. Our results suggest that AMH is a good biomarker of decreased follicular activity due to NEB in the transition period and that AMH can be used for herd weeding in reinsemination.

Variability of fertility indicators in Ayrshire firstcalf heifers under the influence of early lactation

The basic value for optimizing the reproduction of the herd in dairy cattle breeding is the ability of cows to procreate offspring - fertility. It is a complex feature, characterized by many indicators and due to a complex of factors. The goal of our work was to reveal and to study these indicators and factors. The studies were carried out on Ayrshire cows of the Megrega breeding farm (the Republic of Karelia). The average milk yield per cow is over 9,000 kg of milk per year. Fertility indicators were taken into account for 5 years according to the data of 3866 lactations. The following fertility indicators were analysed: the indifference period; the period of insemination; the service period; fertilization from the first insemination; conception index (number of inseminations per conception); early embryonic death. We have analysed the relationship of these indicators with age, the amount of milk yield in general for lactation and during the early lactation period. An increase in the level of milk yield of cows during the current lactation up to 10,000 kg of milk or more was accompanied by a decrease in fertilization after the first insemination from 78.1 to 33.6%, as well as a significant deterioration in other main indicators of reproduction. The study established the relationship between the level of productivity of first-calf heifers during the early lactation period and fertility indicators. The greatest influence on fertility indicators during the early lactation period and insemination was exerted by the level of milk yield in the 1st month of the first lactation. The worst reproductive abilities were shown by first-calf heifers with an average daily milk yield of 34 kg or more. The results obtained can be used in further research on the development of selection indices, selection according to which can provide a high genetic trend in milk yield while maintaining and developing the progressive fertility of dairy cows.

Consequences of extending the voluntary waiting period for insemination on reproductive performance in dairy cows

The aim of the study was to evaluate the effect of extended voluntary waiting period (VWP) on ovarian cyclicity and reproductive performance of dairy cows. Holstein-Friesian dairy cows (N = 154) were blocked and randomly assigned to one of 3 groups with different VWP (50, 125 or 200 d: VWP-50, VWP-125 or VWP-200). Milk samples were collected 3 times a week and analysed for progesterone concentration. Ovarian cycles were classified as: normal (18–24 days), short (<18 days) or prolonged (>24 days). For cows that became pregnant within 100 days after VWP, a VWP-200 d was related with fewer days until pregnancy after end of the VWP (19.4 d) compared with VWP-50 or VWP-125 (35.5, 37.3 d respectively). During 100 days (−50 until 50 d) around the end of VWP, cows in VWP-200 had a greater percentage of normal cycles (91.9 vs 58.0 %, P < 0.01) and a lower percentage of prolonged cycles (6.0 vs 32.7 %, P = 0.01) compared with cows in VWP-50. In the 4 weeks around the end of the VWP, cows in VWP-125 and VWP-200 had a lower milk yield compared with cows in VWP-50 (32.0, 27.5 vs 37.4 kg/d, P < 0.01). Inseminations continued until 300 days in milk, resulting in fewer pregnant cows for longer VWPs. In conclusion, extending the VWP from 50 to 125 or 200 days resulted in a greater percentage of cows with normal ovarian cycles and a lower milk yield around the end of VWP. Moreover, VWP-200 reduced days open after the end of the VWP, compared with VWP-50.

Extending lactation length: consequences for cow, calf, and farmer.

Traditionally, a 1-yr calving interval is advised to farmers from an economical point of view, to realize a yearly peak in milk yield. A 1-yr calving interval, however, implies a yearly event of drying-off, calving and start of lactation, which are all associated with an increased risk for diseases and disorders. Deliberately extending the lactation length by extending the voluntary waiting period (VWP) for first insemination reduces the frequency of these challenging events. This reduction in frequency of calvings can be beneficial for cow health and fertility, but also can be of interest to reduce the number of surplus calves and labor associated with drying off, calving, and disease treatments. Current concerns with respect to an extended lactation are that milk yield is too low in late lactation, which might be associated with an increased risk of fattening of cows in late lactation, and compromised economic returns at herd level. In addition, limited knowledge is available with respect to consequences for cow performance in the subsequent lactation and for calves born to cows with an extended lactation. Moreover, response of dairy cows to an extended VWP depends on individual cow characteristics like parity, milk yield level or body condition. A customized strategy based on individual cow characteristics can be a future approach to select high-producing cows with persistent lactation curves for an extended lactation to limit the risk for fattening and milk yield reduction at the end of the lactation while benefitting from a reduction in challenging events around calving.

Revenues and costs of dairy cows with different voluntary waiting periods based on data of a randomized control trial

Based on modeling studies, a 1-yr calving interval for dairy cows is generally considered optimal from an economic point of view. Recently some dairy farmers are deliberately extending the voluntary waiting period for insemination (VWP) to extend the calving interval. Reasons to extend the VWP are to reduce the frequency of transitions such as dry-off and calving to improve health, to reduce labor associated with these transitions, and to reduce the number of surplus calves. This study aimed to evaluate yearly revenues, yearly costs, and yearly net partial cash flow (NPCF) for individual cows with a VWP of 50, 125, or 200 d based on data from a randomized control trial. The NPCF included revenues and costs for milk yield, calves born, inseminations, concentrate supply, partial mixed ration (PMR) supply, veterinary treatments, discarded milk due to veterinary treatments, culling, and labor (for milking, calving cows, inseminations, and veterinary treatments). Holstein-Friesian dairy cows (n = 153) within one herd were blocked for parity, calving season, and expected (primiparous cows) or previous (multiparous cows) 305-d milk yield. Cows were randomly assigned within the blocks to 1 of 3 VWP (VWP50, VWP125, or VWP200) in wk 6 after calving, and monitored from wk 6 after calving until wk 6 after the next calving or until culling. Revenues and costs were calculated per individual cow and expressed per cow per year. Revenues from milk and costs for PMR and concentrate contributed most to the yearly NPCF. Total yearly revenues were greater in VWP50 compared with VWP200 (€3,169 vs. €2,832), mainly because of €334 greater milk revenues. Total yearly costs were also greater in VWP50 compared with VWP200 (€1,964 vs. €1,729), mainly because of €102 greater concentrate costs. The VWP was not significantly associated with the NPCF per cow per year. A change in milk, feed, or calf price, or a change in labor costs for calving cows or for inseminations had a greater effect on the yearly NPCF of cows in VWP50 compared with cows in VWP200. To investigate variation in NPCF, cows were grouped for yearly NPCF and categorized into 3 economic classes (EC): EC1 (<€1,100/yr), EC2 (€1,100-€1,400/yr), and EC3 (>€1,400/yr). Cows in EC3 had greatest lactation production per day in the experiment (i.e., kg of milk, protein, fat, lactose), and lowest number of veterinary treatments during the experiment.

Economically useful traits of cows depending from the various dates of their first insemination

In Sverdlovsk region Holsteinized black-and-white cattle of the Ural type are being bred. This type of cattle is represented by numerous, highly productive animals with a high genetic potential for productivity. The aim of this article is to study the correlation of age of the first insemination of heifers on their economically useful traits. It was found that the age of the first insemination directly affects the milk productivity of Holsteinized black-and-white cattle of Ural type. The difference in age of the first insemination between the groups was 2.7 months, or 18.6%. The difference of productive period longevity between the groups was also observed, which was 0.21 of lactation (6.7%) in favor of the group that got its first insemination at age of 16-18 months. Cows inseminated for the first time at an earlier date featured lower parameters of milk productivity: lower milk yield for life, lower milk yield for the first lactation and for maximum lactation. The difference was significant at P≤0.01 in favor of cows which underwent the first insemination at age of 16-18 months for life-long milk yield. A significant difference in MFP in milk was revealed in favor of the cows in the first group (the period of the first insemination was 14-15 months). It was 0.09% at P≤0.01. The difference in MFP in milk did not have a considerable influence on increase of nutrients yield in milk, in particular milk protein. The duration of the period between calvings and the service period was long in both groups of cows, which allows concluding that, regardless of the age of first insemination, the decrease in reproductive capacity in cows of modern Holsteinized black-and-white cattle is observed. This is proved by the record KVS – 0.87 - 0.88.

Reproductive Ethics and Family

Reproductive Ethics and Family

Blood parameters and reproductive function of highly productive cows using an organic immunomodulatory drug

The aim of the study was to correct the morphofunctional status of highly productive cows before calving by using an organic immunomodulatory drug. Four groups of Holstein cows (production > 8500 kg per lactation) were formed (n=10 in each group). The immunomodulatory drug contains formic aldehyde 0.07-0.24%, sodium chlorine 0.90-0.95, distilled water. The drug was injected intramuscularly at 25-30 days before calving with an interval of 7 days, three times and 8-10 hours after calving, once (experimental group-1 – 4.0 ml, experimental group-2 - 6.0 ml, experimental group-3 - 8.0 ml). The 4th group was a control. Blood samples were taken 25-30 days before calving, 5 days before calving and 5 days after parturition. Using an immunomodulatory drug in a dose of 6.0 ml 5 days before calving, changes occur in the blood of the animal. In the blood serum of cows, the increased level of Ca by 0.5 mmol/l, P – by 0.22 mmol/l, alkaline reserve – by 4.03 vol%CO2, glucose – by 0.80 mmol/l, total protein – by 9.01 g/l, alpha-globulins – by 2.98%, Ig A – by 36.9%, Ig M – by 15.73%, Ig G – by 50.02%, reduced ratio of AlT and AsT enzymes by 17.04 and 15.74 units./l (up to the reference level), beta-globulins – by 3.44%. This contributed to a reduction in complications of calving and postpartum period by 40.0%, uterine involution by 19.04 days compared to a dose of 4 ml. The difference in criteria that characterize the morphofunctional state when using 8 ml and 6 ml is insignificant. Results of the research are statistically significant (P<0.01). Using an immunomodulatory drug in a dose of 6 ml, the cellular composition, morphobiochemical parameters of the blood are improved. The appearance of obstetric and gynecological pathologies is reduced by 40%, the retention of plaсеnta by 30%, the duration of uterine involution by 19.04 days, the period of effective insemination by 33.56 days. The fertilization of cows in the first hunt is increased by 30% than in the control group.

The relationship between the duration of the service period and the milk yield of the Holsteinized black-mottled breed

The article says that all over the world, dairy livestock is used for dairy production. They use such breeds as a black-mottled breed, Holstein, Dutch ones. Breeding livestock differs in economically useful qualities depending on the climatic and ecological-forage conditions of the breeding zone, and the gene pool of breed resources. The widespread and long-term use of the Holsteinisation, along with a positive effect, i.e., an increase in milk yield, revealed problems associated with a decrease in the reproductive functions of the livestock. The aim of the work is to study the milk yield of the Holsteinized black-mottled breed of the Ural type depending on the duration of the service period. The article notes a significant percentage of dairy cows with a service period of more than 200 days and 121-160 days. Dairy cows with a service period of up to 120 days turned out to be 32%, taking into account the presence of dairy cows with optimal insemination period of only 19%. This indicates a decrease in reproductive functions in the Holsteinized black-mottled breed of the Ural type. The change in milk yield per three lactation depending on the duration of the service period is mainly determined by the individual characteristics of dairy cows and but not on the service period. Dairy cows with a service period of 103 days have the highest milk yield indicators. Dairy cows of other groups with other duration of the service periods had milk yield by 209 - 656 kg, or 1.96 - 6.15% less. The difference was not reliable due to the significant variation in milk yield within the groups. The duration of the service period does not affect the quality indicators of milk. The optimal duration of the service period for livestock breeding, namely the Holsteinized black- mottled breed of the Ural type is considered to be 81-120 days. An increase in the duration of the service period does not lead to an increase in milk yield, but affects the duration of productive longevity of dairy cows.

Genetic determination of reproduction rate traits in dairy cattle breeding

The relevance of the study is due to the need to control economically important attributes of the reproduction of dairy cattle, which have a weak genetic determination and substantially depend on the management and feeding of cows. The purpose of the study is to determine the relationship between the duration of the voluntary waiting period, days open, and period of insemination, assess the impact of the father factor on them. An examination of the influence of genetic and environmental factors on the voluntary waiting period, days open, and milk productivity was conducted. A new feature is highlighted – the period of insemination, which was determined as the difference between the lengthening of the open day period and the voluntary waiting period. Studies were conducted on Holstein cows (a total of 605 heads), the average yield of which was 8777 kg. As a source of primary information, data from the Uniform Agri programme was used, which was processed using variance and correlation-regression analysis. The probable influence of the father factor on milk during 305 days of lactation (11.5%), days open (5.4%), and the period of insemination (5.2%) was revealed. A positive relationship has been established between milk yield and days open (0.115, p≤0.01), milk yield and period of insemination (0.165, p≤0.01), days open and voluntary waiting period (0.257, p≤0.01), days open and period of insemination (0.955, p≤0.01). The dependence of the duration of days open and the voluntary waiting period on such paratypical factors as the age of cows and the month of their calving was examined. There is a tendency to reduce the duration of days open and the voluntary waiting period in cows with each subsequent lactation. It was identified that the duration of the voluntary waiting period was the greatest in cows that calved in November, March, and May, and the smallest – in August. Cows that calved in March had a longer duration of days open, and with calving in February – the shortest. Conclusions are drawn about the possibility of using the value of the period of insemination in selection programmes. The possibility of using reproduction level attributes in selection programmes is proved

Comparative study of the influence of type belonging on the productive and biological indicators of first-calf heifers

In modern economic conditions, the most profitable livestock industry is dairy farming. One of the main conditions ensuring an increase in milk production is the acceleration of the rate of breeding work aimed at creating herds whose animals meet modern requirements for the efficient use of feed, are characterized by a high level of early maturity and the maximum realization of their genetic potential. The comparative assessment of weight and linear characteristics of heifers of different genotypes presented in the work indicates the compliance of the indicators with the standards of breed types. All the animals had a pronounced dairy type. In terms of live weight, the Yenisei type heifers of red-motley breed during the period of fertile insemination were superior to the peers of the Krasnoyarsk type of black-motley breed by 2.2 and 2.1%. The insemination index in heifers of the first and third groups was significantly lower (by 0.26 and 0.31%) than in the compared animals. In the first lactation, the cows of the Krasnoyarsk type of black-motley breed from the third group were superior in milk yield to the cows from the fourth group by 285.2 kg of milk or by 4.9% (P> 0.99). The cows of the Yenisei type of red-motley breed of the first group were superior in milk yield to the cows from the second group by 126 kg of milk or by 2.5% (P> 0.95). The animals inseminated at the age of 16-17 months had the largest mass fraction of fat and protein in milk, regardless of breed.

Fertility and milk production on commercial dairy farms with customized lactation lengths

Drying-off, calving, and start of lactation are critical transition events for a dairy cow. As a consequence, most animal health issues occur during these periods. By extending the voluntary waiting period for first insemination after calving, calving interval (CInt) can be extended, with possible positive effects for fertility and health. Some cows might be better suited for an extended CInt than others, due to differences in milk yield level, lactation persistency, or health status, which would justify a customized CInt based on individual cow characteristics. This study aims to investigate 13 farms with customized CInt, with respect to calving to first service interval (CFSI), accomplished CInt, services per conception (SC), conception rate at first artificial insemination (CR1AI), peak yield, lactation persistency, 305-d yield, and effective lactation yield. In total, 4,858 complete lactations of Holstein Friesian cows between 2014 and 2019 from the 13 farms were grouped by parity (1 or 2+) and CFSI (CFSI class; CFSI-1 < 84; 84 ≤ CFSI-2 < 140; 140 ≤ CFSI-3 < 196; 196 ≤ CFSI-4 < 252, CFSI-5 ≥ 252 d) or CInt (CInt class; CInt-1 < 364; 364 ≤ CInt-2 < 420; 420 ≤ CInt-3 < 476; 476 ≤ CInt-4 < 532, CInt-5 ≥ 532 d). Cow inseminations, available for 11 out of 13 farms (3,597 complete lactations), were grouped by parity (1 and 2+) and CFSI class or CInt class. The fertility and milk production characteristics were analyzed with generalized and general linear mixed models. The CFSI class was not associated with SC, but extended CInt class was associated with increased SC (CInt-1-5; 1.11-3.70 SC). More than 50% of cows in the CFSI class <84 d ended up in longer than expected CInt (>364 d), showing that these cows were not able to conceive for the desired CInt. More than 50% of cows in CInt classes 3 and higher (CInt ≥ 420 d) had an earlier first insemination before successful insemination (CFSI class 1; <196 d), showing that these extended CInt classes consisted of both cows with an extended waiting period for first insemination and cows that failed to conceive at earlier insemination(s). On most farms, lactation persistency was greatest in CInt class 1 (<364 d), probably related to the low peak yield in this class. When this shortest CInt class was excluded, persistency increased with extended CInt classes on most farms. Although at the majority of farms 305-d yield was greater in CInt ≥ 532 d, effective lactation yield at most farms was greatest in CInt from 364 to 531 d, especially for multiparous cows. Based on the results of this study, a CInt between 364 and 531 days seems most optimal for milk production, when high-yielding cows were selected.

Practical experience with artificial insemination (AI) using fresh chilled and frozen semen in mares.

The objective of this study was to compare the efficiency of artificial insemination (AI) carried out with frozen and fresh, diluted and chilled semen under field conditions. One hundred and twenty-nine mares of different breeds were included in the study. Eighty-one out of the 107 mares inseminated with fresh, chilled semen got pregnant. Seven pregnant mares aborted and 74 foals were born. Out of the 22 mares inseminated with frozen semen, 17 mares got pregnant. Two mares out of the 17 pregnant mares aborted and finally 15 healthy foals were born. No difference was found between the two groups in the ratio of the foals born (P > 0.05). The comparison of medians for the number of insemination cycles did not show significant differences. However, a significant difference (Kruskal-Wallis test, P = 0.014) was found in the number of the inseminations per conception in favour of frozen semen (2.5 vs. 1.8 with fresh chilled and frozen semen, respectively). The Cox regression revealed that the type of semen has a significant impact (P < 0.001) on the service period (duration of the insemination period): the use of frozen semen prolonged the insemination period. This could be due to management issues, since re-insemination with frozen semen took place after only one/a few missed oestrous cycles not used for AI.

MODERN TECHNOLOGIES FOR INCREASING THE REPRODUCTION LEVEL IN DAIRY CATTLE

The work aims to study the features of herd reproduction in the conditions of a modern specialized unit for growing repair young animals. The studies were carried out in the conditions of Megaferma OOO in the Kuznetsky region, which is part of the Rusmolco Company in the Penza region, on the number of animals in the modern herd reproduction center. The object of the research was the replacement heifers of the Holstein breed; the subject of the research was: live weight of heifers in different technological periods and the efficiency of insemination of heifers with sexed and ordinary sperm. The studies show the dynamics of live weight of the Holstein heifers of different origin (Holland, the USA, Russia) during directed growing; the achievement of live weight of 350 kg was established by the period of the first insemination at the age 12 months; the Dutch heifers had a higher growth rate during all growing periods. The results of studies indicate that when using sexed semen, the pregnancy rate of heifers from the first insemination was 54.5%; 82.5% of heifers were received from the studied livestock, which is 29.5% more than from the insemination with ordinary semen. When inseminating with sexed semen of heifers of different origins (Hungary, Germany, Russia), the existing differences in the experimental groups were found. The pregnancy rate from the first insemination in the studied livestock ranged from 48.7 to 59.7%, and the yield of heifers - from 77.5 to 89.4%. Such indicators are consistent with the international practice of using sexed semen and with the guarantees of the semen producer. Consequently, an increase in the number of heifers in offspring allows breeding farms to abandon the acquisi-tion of expensive breeding young stock.

Methods for determining optimal insemination time in nutrients

The implementation of the state agrarian policy provides for the creation of modern production technologies based on fundamentally new theoretical and practical research and scientifi c and technical solutions that will ensure the dynamic development of various livestock industries. Low cost of maintenance, high reproduction, resistance to diseases of various etiologies – these are exactly the criteria that nutraceuticals meet. Nutria are herbivorous, multiple polycyclic animals that multiply combine periods of lactation and pregnancy. Thus, with minimal costs for feed, the farm has the opportunity to make high profi ts. Breeding nutria is cost-eff ective and requires a more detailed study, the development of this industry in all regions of Ukraine. When breeding nutria in closed conditions, the reproductive ability of young females decreases by 20–30%. Research in the direction of the reproductive function of female nutria is practically not conducted, therefore, the study of this issue is relevant. In this article, we analyzed the methods for diagnosing the optimal insemination time for nutria, taking into account their shortcomings and ease of use, and found that the earlier methods used (before 2000) have many shortcomings, as a result of which farms receive less profi t due to death, as well as spoiled quality of fur and skins during fi ghts between animals. The use of a male probe provides not only a benefi cial eff ect on the development of the reproductive system of female nutria, but also allows timely determination of the optimal time for insemination of female nutria. The disadvantage of this method is the cost of drugs for epididiotomy and the postoperative period. Colpocytoscopy is an inexpensive, convenient, non-traumatic, and highly accurate method for determining the optimal insemination period in female nutria. Key words: nutria, reproductive cycle, puberty, male probes, insemination, colpocytoscopy.

Automated detection of health disorders in lactating dairy cattle on pasture: a preliminary study.

Since previous health monitoring systems have shown themselves to be unsuccessful in predicting health disorders in dairy cows managed on pasture, the aim of this study was to evaluate the performance of automated health monitoring integrated in an accelerometer-based oestrus detection system (ODS) for dairy cows on pasture. Mixed-breed lactating dairy cows (n=109) in a seasonal-calving herd managed at pasture were fitted with an ODS that provided automated health monitoring. The ODS performed multimetric analysis of behavioural patterns to generate health alerts. Data were collected during the artificial insemination period of 66 days. Clinical examinations and farmer's observations were used to evaluate the performance of automated health monitoring. During the insemination period, the farmer generated two health alerts, which were classified false positives (2/2; 100%). The ODS generated 31 automated health alerts. Of all automated health alerts, 3/31 (9.7%) were confirmed as true health disorders and 28/31 (90.3%) alerts were classified as false positives. The positive predictive value (PPV) of automated health monitoring was 9.7 (95% CI=2-25.8) %. The ODS was able to alert lactating dairy cows on pasture suffering from health disorders. True health disorders were alerted by the ODS before the farmer noticed them, which could provide early and successful treatment when using the system on-farm for automated health monitoring. The evaluated accuracy of automated health monitoring is opposed to a targeted use of the system for on-farm health monitoring. For further validation, testing on other farms and during the transition period would be of interest.

Reproductive performance of replacement dairy heifers submitted to first service with programs that favor insemination at detected estrus, timed artificial insemination, or a combination of both

Our objective was to compare the insemination dynamics and time to pregnancy for up to 100 d after the beginning of the artificial insemination period (AIP) for heifers managed with first artificial insemination (AI) service programs that relied primarily on insemination at detected estrus (AIE) after PGF2α treatments, timed artificial insemination (TAI), or a combination of both. Holstein heifers were randomly assigned to receive first AI service with sex-selected semen after 368 ± 10 d of age with (1) AIE after synchronization of estrus with up to 3 PGF2α treatments every 14 d starting on the first day of the AIP (PGF+AIE; n = 317). Heifers not AIE up to 9 d after the third PGF2α received a 5-d Cosynch protocol with progesterone supplementation [GnRH + controlled internal drug release insert (CIDR)-5 d-CIDR removal and PGF2α-3 d-GnRH and TAI] before TAI. Heifers detected in estrus from CIDR removal and PGF2α until the day before TAI received AIE with no GnRH treatment; (2) 2 PGF2α treatments 14 d apart with the second treatment at the beginning of the AIP (PGF+TAI; n = 334). Heifers received AIE for up to 9 d after the second PGF2α treatment. Heifers not AIE received TAI after the 5-d Cosynch protocol and (3) TAI after the 5-d Cosynch protocol (ALL-TAI; n = 315). Heifers failing to conceive to a previous AI received a subsequent AI with conventional semen at detected estrus or TAI after the 5-d Cosynch protocol. Binomial outcomes were analyzed by logistic regression, whereas time to AI and pregnancy were analyzed with Cox's regression. The hazard of first AI up to 45 d of the AIP was greater for ALL-TAI than for PGF+AIE [hazard ratio (HR) = 1.72; 95% confidence interval (CI) =1.45 to 2.03] and PGF+TAI (HR = 1.51; 95% CI = 1.28 to 1.77), but similar for PGF+AIE and PGF+TAI (HR = 1.14; 95% CI = 0.97 to 1.33). A greater proportion of heifers received AIE in PGF+AIE (98.7%) than in PGF+TAI (78.5%). Overall, first service pregnancy per AI did not differ (PGF+AIE = 42.0%; PGF+TAI = 47.3%, ALL-TAI = 43.8%). Time to pregnancy was reduced for ALL-TAI compared with PGF+AIE (HR = 1.20, 95% CI = 1.02 to 1.42), but was similar to that of PGF+TAI (HR = 1.13, 95% CI = 0.96 to 1.33). Time to pregnancy did not differ for PGF+AIE and PGF+TAI (HR = 1.07, 95% CI = 0.91 to 1.25). Median days to pregnancy were 27, 23, and 21 for heifers in PGF+AIE, PGF+TAI, and ALL-TAI, respectively. We concluded that an ALL-TAI program for first service reduced time to pregnancy, albeit a relatively small reduction, when compared with a program that relied primarily on AIE after induction of estrus with PGF2α treatments. The program that combined synchronization of estrus and TAI (PGF+TAI) resulted in similar time to pregnancy than the predominant TAI and predominant AIE programs.