Biotechnology in Cattle Reproduction.

End of Project ReportTeagasc acknowledges support from the European Union 3rd and 4th Framework Programmes (CT-92-0163 and CT-95-0190)Over the next decade the Irish agri-food industry will have to compete in a rapidly changing world environment arising from increased competitiveness, decreased world market prices and increased consumer demands for higher quality, healthier and safer food. To become competitive in this environment the scale and efficiency of production at both farm and factory level will have to increase significantly and this must be achieved with due regard for the protection of the environment and the welfare of animals. New technologies will be needed to achieve this. Biotechnology will be central to the development of these new technologies. This project has been concerned with the identification and evaluation of biotechnology developments that have the potential to increase reproductive efficiency in cattle. This includes a range of technologies relating to the in vitro production, manipulation, cryopreservation and transfer of cattle embryos. The potential of other emerging technologies such as embryo and sperm sexing, cloning and biopharming or the production of commercially desirable proteins in cows milk are also addressed in this report.European Unoi

Protein Nutrition and Fertility in Cattle.

End of Project ReportThe objectives of the project were to determine the effects of dietary crude protein intake, on blood concentrations of ammonia and urea and on fertility, and on the possible biological mechanisms involved. Heifers were used in all experiments in order to avoid any confounding effects of lactation and, or, negative energy balance. The results are summarised as follows. • • • • 5 Blood urea and ammonia increased linearly with increases in dietary urea. Fermentable carbohydrate, in the form of molassed sugar beet pulp (MSBP), was more effective than barley in reducing blood urea concentration. Plasma ammonia concentrations were more variable but MSBP was again more effective than barley in reducing these. Embryo survival rate was not affected by either dietary crude protein (CP) or fermentable energy intake irrespective of whether animals were fed a silage diet supplemented with feed grade urea or were grazing pasture with a high crude protein content. Despite generating systemic urea concentrations of up to 25 mmol/L and systemic ammonia concentrations of up to 242 μmol/L no significant relationship between these parameters and embryo survival rate was established. Consistent with these results on embryo survival, elevated blood urea or ammonia had little effect on the biochemical composition of oviduct fluid, the environment of the early developing embryo. It can be concluded that elevations in systemic concentrations of ammonia or urea per se, particularly of the magnitude observed under normal feeding conditions, are unlikely to impair embryo survival in cattle as a consequence of disruptions to the oviductal environment

Viability of in vitro produced cattle embryos.

End of Project ReportEmbryo transfer is being increasingly used in the cattle industry. As well as direct embryo transfers, many embryo-based biotechnologies have the potential to improve cattle production efficiency through enhanced breeding strategies, by facilitating the introduction of desirable traits such as disease resistance and through the production of desirable medical or pharmaceutical products in the milk. These biotechnologies are, however, dependent on a supply of viable in vitro produced (IVP) embryos. While the in vitro fertilization rate is high (80%) in cattle, only about 30 transferable embryos, or blastocysts, are produced from every 100 fertilized oocytes. A major factor affecting the viability of IVP embryos is their failure, in a high proportion of cases, to undergo normal development to the blastocyst stage in the manner of in vivo embryos. The major problem relates to a failure of the cells of IVP embryos to form a compact cell mass when they are 5 - 6 days old. This ultimately leads to developmental problems and compromised viability. Cell compaction is recognized as a critical event in early embryo development and has been associated with marked changes in protein synthesis and phosphorylation in the embryos of some species. This report is the first, to our knowledge, to describe the rate and pattern of protein synthesis and phosphorylation before, during and after compaction in both in vivo and in IVP cattle embryos. The main results are summarised below.European Union 4th Framework Programmes (Contract CT-95-0032

Fluctuations in Energy Intake and Fertility in Cattle.

End of Project ReportsReproductive failure in dairy cows results in fewer calves born, lower milk sales, slower genetic progress and consequently, significant financial loss to the industry. Dairy cattle breed improvement programmes have, at least until very recently, focused primarily on increasing the yields of milk or milk solids. The resulting genetic improvement has led to significant increases in milk yield per cow but this increase is now associated with a significant decline in cow reproductive wastage. An important part of the Teagasc research programme in this area is to determine the time at which embryo loss occurs and also to determine whether the extent of the embryo loss is affected by the energy nutrition of the cow and to devise strategies to reduce its extent. This project has focused on the relationship between changes in dietary energy intake near the time of insemination and the extent and pattern of embryo survival. The main results are summarised in this report and detailed results of the several experiments involved have been published in the papers listed at the end of this report. • • 4 The objectives of this project were to determine the effect of changes in energy intake near the time of insemination on embryo loss rate, on the timing of embryo loss and on the possible biological mechanisms involved. Cross bred heifers were provided with either high or low energy intakes that were based on pasture allowances calculated to provide either 0.8 or 2.0 times their maintenance requirements. These energy intakes were allocated for two weeks before and about five weeks after insemination. The effect of the changes in energy intake on embryo loss and on the time at which embryo loss occurred, relative to the time of insemination, was established. Possible associations between embryo loss and blood concentrations of progesterone, NEFAs, insulin and glucose were examined. A sudden reduction from a high to a low energy intake imposed for two weeks from the day of insemination reduced the subsequent embryo survival rate by 30 percentage points to a survival rate of 38%. When energy intake over this same period was either maintained or increased, embryo survival rate remained high (overall mean, 69%), within a range of 65-71%. The time at which embryo loss occurred was established. Embryo survival or pregnancy rates measured on days 14 and 30 after insemination and at full term were 68%, 76% and 72%, respectively. These results provide new information indicating that most embryo loss, at least in heifers, had occurred on or before day 14 after insemination. There was no evidence of any association between the shortterm changes in energy intake either before or after AI and blood progesterone concentration. Neither was there any evidence that the detrimental effect of the sudden reduction in energy intake on embryo survival was mediated through changes in the systemic concentrations of non-esterified fatty acids (NEFAs) or insulin. There was a suggestion, however, that the detrimental effect of the reduced energy intake may operate through a reduction in systemic glucose concentrations.Dairy Levy Farmer Fun

Increasing the use of AI in suckler herds.

End of Project ReportReproductive efficiency is a major factor affecting production and economic efficiency of beef herds. For herds using artificial insemination (AI) heat detection rate and calving rate are the two major determinants of compactness of calving and ultimately the calving-to-calving interval. Heat detection is a time consuming repetitive chore that must be carried out up to 5-times each day for as long as AI is used. Heat detection rate, usually measured as submission rate, is hugely variable from herd-toherd but for most herds only between 40% and 70% of cows that exhibit heat are actually detected by the stockman. Despite an increased understanding of the endocrine control of the oestrous cycle the goal of fixed-time insemination is not yet consistently achievable in either cows or heifers treated at different stages of the oestrous cycle and in different physiological states. The overall objective of the this project was to develop an improved cost effective hormonal method to control the time of ovulation to allow beef cows be bred by AI without the need for heat detection. A total of 3 studies were carried out and the results are summarised in this report.Department of Agriculture, Food and the Marin

Nutrition and Oestrus and Ovarian Cycles in Cattle

End of Project ReportThe overall objective of this project was to establish the effects of both long- and short-term changes in nutrition on ovarian follicle dynamics and on the systemic concentrations of metabolic and reproductive hormones. In order to avoid the confounding effects of lactation, suckling and maternal–calf bonding, beef heifers were used in a series of three studies.European Union 3rd Framework Programme (Contract AIR3-CT94-1124

Cattle Embryo Growth Development and Viabilty.

End of Project ReportA major problem for the cattle breeding industry is the high rate of early embryo loss which compromises reproductive efficiency and genetic improvement, resulting in serious financial loss to farmers. An important part of the Teagasc research programme in this area is the investigation of basic parameters of cattle embryo growth, development and viability during the critical period when most of the embryo loss occurs. We have now characterised this period of embryo development and to our knowledge, this is the first report describing the morphology, growth rate, protein content and metabolic activity of cattle embryos during this period. The main results are summarised here and detailed results have been published in the papers listed at the end of this report. Embryo growth rate and protein content increased exponentially between days 8 and 13 after fertilisation. Furthermore, there was a high rate of protein synthetic activity, energy and amino acid metabolism and signal transduction activity, all reaching a peak between days 8 and 13 after fertilisation. Because of the high rate of metabolic activity evident during this time it is likely that the embryos are very susceptible to environmental changes that have the potential to interfere with normal developmental mechanisms. The results arising from this project suggest that the critical period of early embryo loss in cattle may now be narrowed to a time window of day 8 to 13 rather than day 8 to 16 as presumed up to now. The main results are summarised.European Union 4th Framework Programme (Contract CT-95-0190)