Conference Presentations by Juraj Grizelj
Zbornik radova, 2024
The paper presents the technical description, scientific basis, and the purpose, meaning and poss... more The paper presents the technical description, scientific basis, and the purpose, meaning and possibilities of applying genomic analysis as part of a program to improve the productivity of dairy cows using veterinary methods based on modern technological procedures. Also, the results and experience in the application of genomic analysis in Croatia, where this method is widely used in the organization of the breeders’ association, are presented, all within the framework of the international project of genetic improvement of Simmental cattle. The application of genomic analysis on Holstein cattle, although very widespread in the world, is at the beginning in Croatia, and this is one of the first reports on the subject. The paper presents the possibilities, which are in the stage of practical development, of applying complementary procedures of assisted reproduction in order to make the most efficient use of the genetic potential of animals in which a superior genome has been determined. The results and the method of their evaluation are presented, as well as examples of 3 farms where the research was conducted. It was concluded that there is a large variability of individual traits within the herd, and that this is an indicator of the need for intensification and wider introduction of organized work on the advancement of genetics using these modern methods. Within this framework, the need to form breeding goals for each farm was emphasized with the aim of achieving greater added value in those parts of cattle production where the producer’s commercial interest lies. The possible consequences of the reduction of genetic variability at a higher concentration of identical genes were also pointed out. At the end, a rough estimate of the costs was given, and it was concluded that the introduction of this method is interesting as an investment for farmers to improve the genetic structure of their herd, but also for the veterinary service as an extension of the base of professional services. Of course, it is illusory to expect that this modern method alone can contribute to the farmer’s breeding goals and increase the productivity of the farm. These goals can only be achieved through the integral application of a quality program of expert support by specialist veterinarians and expert advisors of other specialties in close coordination with the farmer, who must effectively implement the obtained expert information.
Proceedings, 2024
The paper presents the results of the application of a multidisciplinary program in order to incr... more The paper presents the results of the application of a multidisciplinary program in order to increase the productivity and profitability of a dairy cow farm by applying veterinary methods supported by digital techniques. The basis of the program is the monitoring of physiological and production indicators with software applications that often make an integral part of farm equipment today. The program includes treatment of cows in the part of feeding, control of nutritional and metabolic status and reproduction. The program is designed in such a way that it can be taken over by interested veterinary organizations that have an interest in offering milk producers - the users of their services - a professionally differentiated program with the aim of increasing the productivity of their production. In addition to clinical disciplines, the program also contains a module for evaluating the economic efficiency of production. In this report, the results of the application of the program in relation to reproduction is presented. The key part of the program is digital equipment that, by indicating the presence or absence of function, provides the possibility of timely intervention in making the cows cyclic, which for various reasons did not establish reproductive (cyclic) function in time to be able to achieve reproduction and production indicators as the service period of 110 days or the average day of lactation of 180 days, which are the biological prerequisites for the biologically optimal production capacity of the herd. Results. Assuming an earlier intervention, especially in combination with other components of this program (nutrition, nutritional-metabolic status), it is concluded that the application of this program would successfully achieve the intensity of the reproductive function in quality, which is a prerequisite for achieving production capacity in accordance with desirable economic standards.
Proceedings, 2024
The paper introduces the functional basis of nutritional and metabolic status in dairy cows. The ... more The paper introduces the functional basis of nutritional and metabolic status in dairy cows. The importance of determining nutritional and metabolic status was considered from several aspects and it was concluded that the use of data is an irreplaceable indicator of metabolic disorders and a number of subclinical diseases of dairy cows. The main causes of the lower intensity of production and reproduction should be sought in improper nutrition and the consequences that manifest as significant shortages, which is reflected in a disturbed nutritional and metabolic status. Diagnosing disorders early - in the phase of their occurrence, enables timely correction of their occurrence through (most often) correction of the diet or by removing other causes, that is, by applying appropriate medicinal substances. Early diagnosis and correction of the mentioned management factors, or - if indicated - treatment, prevents the occurrence of damages due to the reduction of production and reproduction, which are regular consequences of these disorders and diseases. In other words, the implementation of this methodology is a prerequisite for the program to increase the productivity of dairy production. Digital technology makes it possible to carry out milk analysis directly on the farm, which significantly increases the efficiency of the entire model. In an experiment - monitoring of these data on an otherwise relatively successful dairy farm with 40 cows of the Holstein breed, it was determined that in the uninseminated cows on the farm, as many as 72% had an elevated fat concentration in the milk in the first 40 days of lactation, while 27% of them had in addition, an elevated quotient (> 1.4) between the concentrations of milk fat and protein, which indicates the initial phase of liver function failure due to the heavy load of processing mobilized fat into a metabolically suitable energy substrate.
Reproduction in Domestic Animals, 2024
Different protocols using hormonal treatments and light treatments exist for the reproductive man... more Different protocols using hormonal treatments and light treatments exist for the reproductive management of goats during non-breeding and breeding season. The classical light treatment can be used during the non-breeding season and consists of subjecting goats to 90 long days (16 hours of light per day or natural long daylights) followed by 60 short days (8 to 12 hours of daylight or SC melatonin implants). The switch from long to short days provokes sexual activity. Concurrently with the start of the short days, male goats are removed from the females and re-introduced 60 days later. This male effect results into a synchronized oestrus of the females 5 to 11 days later. The alternative light treatment can be used during the breeding season and consists of alternations of 90 long days, 90 short days, 90 long days, and 90 short days. In this protocol, SC melatonin implants are used to simulate short days during spring, and natural short daylights during winter. Further, hormonal treatment protocols using prostaglandin (PG) can be applied after the classical and alternative light treatment. One injection of PG is given 17 days after re-introduction of the male goat, with AI 70 hours later. Further, during breeding season, two injections of PG 9 days apart can be given without prior light treatment, with the first injection at the time of re-introduction of the male goat. AI is performed 60 hours after the second injection. Hormone-free protocols can be used after the classical or alternative light treatment. The re-introduced male goat is equipped with an apron. Five days later, a marker is fixed on the apron and marked female goats are recorded during the following three days. When more than 40-50% of the goats are marked, AI of marked goats is performed 24 hours later.
Short review, current trends and situation of goat breeding in Croatia
Buletin caprin, 2023
The Law on the Prohibition of Keeping Goats Outdoors, which in 1954 greatly set back goat farming... more The Law on the Prohibition of Keeping Goats Outdoors, which in 1954 greatly set back goat farming, has significantly contributed to the decrease in the number of goats in Croatia in recent history.
Today's goat population in Croatia consists of 65.227 animals, out of which the vast majority are kept extensively (karst area), and only a small part in semi-intensive or intensive farming in the north of the country.
There are only 8,190 (12%) herd book goats whose data on lambing, milk yield and parentage are recorded. The growth of kids up to 90 days of age is also monitored with the performance field test.
The breed composition in semi-intensive or intensive breeding includes the Alpine, Saanen dairy breeds, and the Boer meat breed. Croatian autochthonous breeds of goats are extensively bred (Croatian variegated - for meat, Croatian white - for milk, and the critically endangered Istrian goat). The introduction of genomic testing of bucks by detecting DNA markers for increased milk yield is underway.
The Faculty of Veterinary Medicine University of Zagreb offers a postgraduate specialist study in English and Croatian language for the breeding and health management of small ruminants with the aim of acquiring additional competences for veterinarians specific to the field of small ruminants farming.
The team of researchers from the Faculty of Veterinary Medicine University of Zagreb has so far demonstrated high research potential through several national and international projects (FP7, AUF, SEE-ERA.NET Plus, etc.) in the field of assisted reproduction, embryo transfer and research of hormonal and non-hormonal protocols for synchronizing the sexual cycle of goats with the use of artificial insemination.
Book of Abstracts, 2019
Goats from high latitudes (>35°) and also from subtropical latitudes (25°-35°) exhibit seasonal c... more Goats from high latitudes (>35°) and also from subtropical latitudes (25°-35°) exhibit seasonal changes in reproductive activity. The breeding season in general starts in autumn and ends in winter. Apart from hormonal methods, out-of-breeding reproduction season can be achieved using natural methods based on daylength manipulation. The introduction of males among anovulatory females can also induce ovulatory activity during anoestrus what is called “the male effect”. Following introduction of a male, goats ovulate around day 3, mostly non fertile ovulations. This is called as a non-fertile short cycle (SC). They ovulate again after 5-7 days (Normal Cycle - NC) with this second ovulation being usually fertile (SC-NC cycle). The problem of naturally induced ovulations is insufficient synchronization for application of Artificial Insemination (AI) methods in and out of the breeding season in order to obtain pregnant females. Two AI protocols after oestrus induction with male effect have been studied to evaluate their efficacy under field condition but at least 5 days of insemination were needed. Higher synchrony of ovulations would allow AI protocols to be simplified and therefore to minimise costs by reducing the number of AI. To improve the protocol, the hormone serological profiles of the Saanen goats (N=82) were made after photoperiod treatment (90 long days + 60 short days) and introduction of the males out of season and also in transitional period. Blood samples for progesterone level were drawn every day from introduction of males (D0) until D13. Blood samples for luteinizing hormone (LH) level were drawn from D5 until D9 every 4 hours. Out of season 75.9% goats developed SC-NC cycle, 93.7% of these goats exhibit oestrus during D5-D9 (8.0±0.94 days), 100% of these goats displayed preovulatory LH surge between D5-D9 (201.8±21.4 hours). In transitional period 92.3% goats developed SC-NC cycle, 94.4% of these goats exhibited oestrus during D5-D9 (6.9±0.64 days) and 100% of these goats displayed preovulatory LH surge between D5-D9 (169.9±14.6 hours). Lower number of goats developed SC-NC cycle out of season and these goats responded later to the male effect with higher variation of ovulation time.
Workshop Internacional Caprino 2022, 2022
Review on physiology of sexual cycle of goats, hormonal and non-hormonal synchronization methods ... more Review on physiology of sexual cycle of goats, hormonal and non-hormonal synchronization methods and use of non-hormonal synchronization protocols, artificial insemination
Book of Abstracts 9th International Scientific Meeting Days of Veterinary Medicine 2022, 2022
Goats belong to the „short day breeders“ group of seasonal polyoestrous animals. In the temperate... more Goats belong to the „short day breeders“ group of seasonal polyoestrous animals. In the temperate climate zone, their season lasts from mid-summer till mid-autumn, being regulated by epiphysis' melatonine secretion, as well as by genetics and environment factors. Therefore, the presence of goat milk and dairy products, as well as goat meat, at the food market, is exclusively seasonal. In order to provide goat food products throughout the whole year, reproductive herd menagement should be established. This paper presents a brief overview of the methods of reproductive management in dairy goat herds (natural mating and artificial insemination, hormonal and nonhormonal synchronization methods and embryo production and transfer). Application of reproductive and breeding programs allow efficient diffusion of desirable genetic traits in a selection program.
Zbornik predavanja , 2022
Although sheep and goat breeding in our region is characterized mainly by a traditional way of fa... more Although sheep and goat breeding in our region is characterized mainly by a traditional way of farming, dynamic changes in global agricultural production have affected this branch of animal husbandry. Intensive farm breeding, which is gaining momentum, in addition to other factors (housing, nutrition, selection, health care, etc.) also requires a good control of reproductive functions. In the last few decades, our sheep and goat breeding systems have introduced various techniques of assisted reproduction, such as synchronization of estrus and ovulation, laparoscopic intrauterine insemination, embryo production (MOET and IVF), sperm cryopreservation, photoperiod manipulation, etc. This paper provides an overview of current news in this area, presenting recent results of scientific research, as well as our experiences in research and "translation" of this knowledge into routine agricultural practice.
With the aim of obtaining a offspring , and thus the beginning of lactation in different seasons, hormonal treatments with a combination of progestogens, prostaglandins, Equine Chorionic Gonadotropin (eCG) or "natural" methods can be used: light regime manipulation or exposure to the male after a period of isolation, the so-called "ram/buck effect". Application of the latest artificial insemination techniques in small ruminants suggests that the success rate of artificial insemination could be improved by intracornual semen deposition. Our results indicate a high pregnancy rate in sheep (about 40% in the off-season and about 65% during the breeding season) and in goats even more, around 80%. The survival rate of goat spermatozoa was dramatically improved by the use of "yolk-free" extenders, based on soy lecithin as a cryoprotectant. In contrast, the cryopreservation of ram semen has not made significant progress in the past decades, despite a great deal of research work in testing new media supplemented with various supplements, e.g. antioxidants (oxidized glutathione, reduced glutathione, cysteine), but more recent in vivo studies have shown optimistic results.
Key words: assisted reproduction, sheep, goats, artificial insemination, estrus synchronization
Uploads
Conference Presentations by Juraj Grizelj
Today's goat population in Croatia consists of 65.227 animals, out of which the vast majority are kept extensively (karst area), and only a small part in semi-intensive or intensive farming in the north of the country.
There are only 8,190 (12%) herd book goats whose data on lambing, milk yield and parentage are recorded. The growth of kids up to 90 days of age is also monitored with the performance field test.
The breed composition in semi-intensive or intensive breeding includes the Alpine, Saanen dairy breeds, and the Boer meat breed. Croatian autochthonous breeds of goats are extensively bred (Croatian variegated - for meat, Croatian white - for milk, and the critically endangered Istrian goat). The introduction of genomic testing of bucks by detecting DNA markers for increased milk yield is underway.
The Faculty of Veterinary Medicine University of Zagreb offers a postgraduate specialist study in English and Croatian language for the breeding and health management of small ruminants with the aim of acquiring additional competences for veterinarians specific to the field of small ruminants farming.
The team of researchers from the Faculty of Veterinary Medicine University of Zagreb has so far demonstrated high research potential through several national and international projects (FP7, AUF, SEE-ERA.NET Plus, etc.) in the field of assisted reproduction, embryo transfer and research of hormonal and non-hormonal protocols for synchronizing the sexual cycle of goats with the use of artificial insemination.
With the aim of obtaining a offspring , and thus the beginning of lactation in different seasons, hormonal treatments with a combination of progestogens, prostaglandins, Equine Chorionic Gonadotropin (eCG) or "natural" methods can be used: light regime manipulation or exposure to the male after a period of isolation, the so-called "ram/buck effect". Application of the latest artificial insemination techniques in small ruminants suggests that the success rate of artificial insemination could be improved by intracornual semen deposition. Our results indicate a high pregnancy rate in sheep (about 40% in the off-season and about 65% during the breeding season) and in goats even more, around 80%. The survival rate of goat spermatozoa was dramatically improved by the use of "yolk-free" extenders, based on soy lecithin as a cryoprotectant. In contrast, the cryopreservation of ram semen has not made significant progress in the past decades, despite a great deal of research work in testing new media supplemented with various supplements, e.g. antioxidants (oxidized glutathione, reduced glutathione, cysteine), but more recent in vivo studies have shown optimistic results.
Key words: assisted reproduction, sheep, goats, artificial insemination, estrus synchronization