Pregnancy Rates in Repeat-breeder Heifers Following Multiple Artificial Inseminations during Spontaneous Oestrus

Hormonal asynchronies during oestrus, related to the presence of suprabasal plasma-progesterone (P4) concentrations and a delayed ovulation, interfere with the fertility of repeat-breeder heifers (RBH). Since tubal dysfunction can occur in connection with hormonal asynchronies and constrained availability of fertile spermatozoa at the time of ovulation, the present study tested the hypothesis that frequent sperm deposition from onset of oestrus to ovulation may improve pregnancy rates in RBH. Five RBH and five virgin heifers (VH; controls) were repeatedly artificially inseminated (AI) at 6 h intervals from onset of oestrus to spontaneous ovulation. Hormone analyses revealed suprabasal P4 concentrations and a delay in the occurrence of the luteinising hormone (LH) surge, but a normal cortisol profile in RBH. Compared with controls, RBH presented longer interval from onset of oestrus to ovulation, and therefore, received more AIs. Pregnancy rates in RBH reached control levels (60%; NS), indicating that the hypothesis might be correct. Pregnancy rates in VH were below the expected range, presumably attributed to a deleterious influence of the frequent handling. The study suggests that pregnancy rates can be improved in RBH by frequent AI in relation to spontaneous ovulation. However, this practice of repeated manipulations, while seeming not to show adverse effects, lacks practicality for routine use

Herd health and reproductive management associated with lamb weight gain and mortality in sub-Saharan drylands-a case from Ethiopia.

Sheep are important for food and livelihood security in sub-Saharan Africa, and maximizing lamb weight gain while minimizing mortality is essential to improve production. Using the Menz sheep breeding villages of Amhara region in Ethiopia as a case study, the weight gain and mortality rate of 208 lambs were monitored during their first 5 months of life. The study was conducted in intervention and control villages, where the intervention villages were part of community-based breeding programmes and had participated in various projects aiming to improve sheep production and management. Multivariable linear regression analysis was conducted to detect associations between weight gain from birth to 1 month, and birth to 5 months, and different lamb and ewe characteristics, farmer education, application of management routines, and presence of village level sheep management interventions. In general, lambs from intervention villages, without certain signs of diseases, whose mothers were 2 years or older, had a body condition score of more than 2 on a 5-point scale, and who originated from flocks where disease prevention strategies had been implemented, had gained more weight. Overall lamb mortality was 6.8% with most deaths occurring before 1 month of age. This study highlights that health interventions in ewes improve lamb survival and weight gain and that the care of lambs during the first month of life is crucial for overall herd productivity

On repeat breeding in dairy heifers

Reproductive efficiency is essential for profitable dairy farming. Some heifers require several artificial inseminations (AIs) to conceive, and after repeated pregnancy failures, they are usually culled. The aim of this thesis is to contribute to the characterisation of repeat-breeder heifers (RBH), focusing on the oestrous period. Oestrous behaviour, follicular dynamics, and hormone patterns were studied in RBH (≥ AIs) and virgin heifers (VH, controls). RBH displayed endocrine aberrations, with progesterone concentrations of ≥ 0.5 nmol/L (suprabasal levels) at ovulation, whereas concentrations during the luteal phase were lower than normal. The preovulatory LH surge was delayed, standing oestrus was prolonged, and the preovulatory follicle persisted longer than in VH. In a field survey, the occurrence of suprabasal progesterone levels at insemination was confirmed and determined as a risk factor for non-pregnancy. Conception rates declined with increasing numbers of AIs, indicating the involvement of intrinsic factors in RBH. Pharmacological stress was induced in ovariectomised heifers, resulting in similar adrenal progesterone production (exceeding the suprabasal progesterone concentrations) in all heifers but higher cortisol-producing capacity in RBH, indicating that stress may contribute to repeat breeding. The question of whether in-built endocrine aberrations affected follicular and oocyte quality was studied. Results from light and electron microscopy (TEM) and the degree of apoptosis in the follicular wall (evaluated by the TUNEL technique) indicate that RBH enter standing oestrus with prerequisites similar to those of VH. Ability for in vitro maturation (IVM) was studied in oocytes collected by ovum pick-up (OPU), and effects of OPU on RBH characteristics were evaluated. Immature RBH oocytes were scored to be of lower quality at retrieval but not at evaluation by confocal laser scanning microscopy or TEM. After IVM, spatial organelle reorganisation was, however, less advanced in RBH oocytes, revealing cytoplasmic maturation asynchrony. Performing AI subsequent to OPU resulted in pregnancy rates similar to field fertility in RBH and VH, thus apparently not impaired by OPU. Multiple deviations (caused by intrinsic factors) occur along the course of events toward ovulation, which may affect oocyte developmental capacity and conditions for fertilisation and early embryonic development, thereby to some extent explaining the sub-fertility in RBH

The influence of oestrous substances on cyclicity and oestrous behaviour in dairy heifers

<p>Abstract</p> <p>Background</p> <p>Declining fertility is a major concern for dairy farmers today. One explanation is shorter and weaker expression of oestrus in dairy cows making it difficult to determine optimal time for artificial insemination (AI). Chemical communication is of interest in the search for tools to detect oestrus or to synchronise or enhance oestrous periods. Pheromones, used in chemical communication within species, can influence reproduction in different ways. The aim here was to investigate whether oestrous cycle length, and duration and intensity of oestrous expression in dairy heifers could be manipulated through exposure to pheromones in oestrual substances from other females.</p> <p>Methods</p> <p>Beginning on day 16 of two consecutive control oestrous cycles, ten heifers of the Swedish Red Breed (SRB) were exposed to water. During the two following cycles the heifers were exposed to urine and vaginal mucus, obtained from cows in oestrus. Cyclicity parameters were monitored through hormone measurements, oestrus detection and ultrasonographic examination.</p> <p>Results</p> <p>We found no difference in cycle length or in duration of standing oestrus between control and treatment. We did, however, find a tendency of interaction between type of exposure (control or treatment) and cycle number within type of exposure for cycle length (p = 0.068), with the length differing less between the treatment cycles. We also found a tendency of effect of type of exposure on maximal concentration (p = 0.073) and sum of concentrations (p = 0.063) of LH during the LH surge, with values being higher for the control cycles. There were also significant differences in when the different signs of oestrus occurred and in the intensity of oestrous expression. The score for oedema and hyperaemia of external genitalia was significantly higher (p = 0.004) for the control cycles and there was also a significant interaction between type of exposure and time period for restlessness (p = 0.011), with maximum score occurring earlier for treatment cycles.</p> <p>Conclusions</p> <p>No evidence of altered oestrous cycle length or duration of oestrus after exposure of females to oestrous substances from other females was found. Expression of oestrus, and maybe also LH secretion, however, seemed influenced by the exposure, with the effect of treatment being suppressive rather than enhancing.</p