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A short herd lifespan is a significant economic loss to the dairy industry, with infertility a major cause. Conception rates to first service have fallen from around 60% in the 1970s to 40% by 2000. The re-establishment of ovarian cyclicity after calving is important in determining the timing of conception which should be around 80 days postpartum (PP) to maintain yearly calving intervals. Insulin-like growth factor-I (IGF-I) is thought to influence ovarian activity at this time. We have previously shown that pre-pubertal IGF-I levels are related to growth and can predict concentrations around first calving. This study investigated IGF-I, insulin, glucose, urea and betahydroxybutyrate (BHB) concentrations before and after first calving in typical UK herds in relation to measures of fertility during the first lactation.
The decline in dairy cow fertility over the past 30 years has major economic, welfare, genetic and environmental consequences. A significant number of potential replacement heifers either never calve or else complete only a single lactation. The relationships between metabolic status and fertility may change with age as cows reach physical maturity. To determine the reasons behind the high loss rates attributable to infertility, this study tracked a group of animals until the end of their second lactation to compare fertility and metabolic hormone profiles in the same cows at different ages.
The UK dairy industry currently suffers huge losses due to declining fertility. Although fertility in the sheep industry is good overall, the use of multiple ovulation and embryo transfer techniques would benefit from improved conception and embryo survival rates. Studies suggest that omega-3 supplementation may bring about a reduction in the secretion of prostaglandin F2α (PGF2α), which would favour the maintenance of the corpora lutea (CL) and hence, a successful pregnancy. Feeding fish meal to dairy cows has been found to improve pregnancy rates by 10% (Burke et al., 1997). Using sheep as a model, this study aimed to evaluate whether reproductive performance in ruminants is improved by feeding an algal source of omega-3 fatty acids, particularly docosahexaenoic acid (DHA, C22:6 n-3). The study was also structured to determine whether prostaglandin production is affected by supplementing diets with omega-3.
In the cow, the embryo during the first three weeks of pregnancy is free living in the uterine lumen and is dependent on the maternal glandular secretions for its nutritional support. If the environment is appropriate, the embryo will develop sufficiently to prevent luteolysis. The aim of this study was to investigate the regulation of factors involved in embryonic-endometrial interactions during early pregnancy. Uterine horn sections were collected from 17 pregnant (PREG), 9 inseminated but no embryo present and 10 uninseminated cyclic control cows on days 12, 14, 16 and 18 after natural oestrus. The latter two groups were combined to form a single non-pregnant (NP) group. Trophoblast sections were also collected from the day 14, 16 and 18 embryos. The mRNA for interferon tau (IFNτ), oxytocin receptor (OTR), oestrogen receptor a (ER), prostaglandin G/H synthase -2 (PGHS-2), insulin-like growth factor (IGF) -I and IGF binding protein -1 (IGFBP-1) was determined by in situ hybridisation using 45 mer oligonucleotide probes end-labelled with35 S. The optical density (OD) readings were measured from the resulting autoradiographs. The expression of IFNτ mRNA in the trophodectoderm did not vary with embryo age. The expression of OTR mRNA in the luminal epithelium was first detectable on day 14 in 2 out of 5 NP cows and increased thereafter. Conversely, OTR mRNA was undetectable in all PREG cows except for one day 18 cow. In the NP cows, the first significant increase in ER mRNA concentrations in the luminal epithelium was observed on day 16. The pregnancy had no effect on ER mRNA concentrations in the luminal epithelium on days 12 and 14, but was significantly reduced on day 16 and was undetectable by day 18. On day 18, PGHS-2 mRNA was detectable in the luminal epithelium of all cows, but was unaffected by pregnancy status. The expression of IGF-I mRNA in the subepithelial stroma was maintained from days 12 to 18, but was reduced in the day 18 NP cows. IGFBP-1 mRNA concentrations in the luminal epithelium peaked on day 14 in both NP and PREG cows. Thereafter, concentrations declined in the NP group but were maintained in the PREG animals. In conclusion, the suppression of OTR mRNA expression by the embryo does not appear to require the prior suppression of ER mRNA. The continued expression of IGF-I and IGFBP-1 mRNA is likely to play an important role in the establishment of early pregnancy in the cow.
Previous studies have shown that 35 — 40 % ofmodern dairy cows experience ovarian disturbances during early lactation. Even though negative energy balance (NEB) has been implicated as a regulator of ovarian function, the exact metabolite(s) or hormone(s), which mediate this effect is still not clear. In this study, we investigated the relationship between blood metabolites (NEFA, BHB and glucose) and plasma insulin like growth factor-I (IGF-I) and ovarian dysfunction. Thirty three Holstein-Friesian cows were fed a lactational ration ad libtium and were inseminated at observed oestrus starting from 56 days post calving. Three times weekly milk samples and weekly blood samples were collected from cows from calving until confirmed pregnant. Cows were placed into “NORMAL” or “ABNORMAL” categories of ovarian activity based on their milk progesterone profiles. The days to first service were 71 ± 2 in “NORMAL” and 78 ± 6 in “ABNORMAL” animals. The calving to conception interval (days open) was shorter in the “NORMAL “ than the “ABNORMAL” group (90 ± 8.7 vs 119 ± 15.2 days). IGF-I levels were significantly lower in the “ABNORMAL” group from 2 until 7 weeks after calving (P<0.02) and NEFA concentrations were higher in the “ABNORMAL” cows in the early postpartum period (P<0.03). There was no significant difference in either plasma BHB or glucose. This study confirms that elevated plasma NEFA concentrations are associated with “ABNORMAL” ovarian activity. The most significant difference was in plasma IGF-I concentrations, which stayed lower for nearly 2 months in the “ABNORMAL” animals.
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