Search PubMed⌕ Search

Biomedical subjects

H Dobson

Publications and source records attributed to H Dobson.

At least 73 records · Page 4Linked to original sources
PubMed1996

Reproductive and financial impact of a do-it-yourself artificial insemination programme compared with keeping a bull.

The fertility of five dairy herds was studied for three years while they initiated a programme of do-it-yourself artificial insemination (DIY AI) and kept a herd bull, and the financial impact of the new programme was assessed. The herds of approximately 100 cows were all Friesian pedigree, changing to Friesian/Holstein. The DIY inseminators each operated within one herd and were all trained at the same centre. Within a herd, each cow inseminated by a bull was paired with a cow inseminated by AI. The paired cows calved during the same week and were of the same lactation number and genetic type. Each year 20 matched pairs, that is 40 cows per herd, were used, giving a total of 600 cow records. During the first two years, in the majority of herds the calving interval decreased in both the cows inseminated by DIY AI and by the bull. There was a higher culling rate for all cows in the first year, resulting in an improved Fertex score and improved profitability in the second year compared with the first. However, in the five herds combined it was only by the third year that the calving interval for the DIY AI cows was shorter (by 17.9 days) than for cows inseminated by the bull (P < 0.05). The first year of the DIY AI programme was a financial strain for the farmers, but the second and third years showed enough improvement to recover the losses incurred in initiating DIY AI, that is, the capital investment and learning period.

Animal Husbandry↗
PubMed1996

Norgestomet implants, plasma progesterone concentrations and embryo transfer pregnancy rates in cattle.

A study was undertaken to test the hypothesis that supplementation with exogenous progestagen at the time of embryo transfer would enhance pregnancy rates in recipients. Two-hundred-and-seventy-two oestrus-synchronised crossbred heifer and cow recipients received 200 grade 1 and 72 grade 2 Simmental embryos transferred non-surgically. Heparinised blood samples were taken on day 6 and day 7 (oestrus = day 0) for the assessment of the endogenous plasma progesterone concentration. Half the recipients received an ear implant impregnated with 3 mg norgestomet on the day of embryo transfer. The pregnancy rates were 51.9 and 49.6 per cent for the norgestomet-treated and control groups, respectively. The pregnancy rate for grade 1 embryos was 56.0 per cent and for grade 2 embryos 36.1 per cent (P < 0.01). The breed of recipient, weekday of transfer, operator and condition score had no effect on pregnancy rate. The maiden heifers had a higher pregnancy rate (54.2 per cent) than the cows (46.2 per cent). The mean plasma progesterone concentrations of the pregnant and non-pregnant groups on day 6 were 6.7 ng/ml and 6.6 ng/ml, respectively, and 7.6 ng/ml in both groups on day 7.

Animals↗
PubMed1996

Reduced conception rates in dairy cattle associated with serological evidence of Leptospira interrogans serovar hardjo infection.

Fertility data from 673 cows in five dairy herds with a moderate to high seroprevalence of microscopic agglutination titres (MAT) of > or = 1:10 against Leptospira interrogans serovar hardjo were collated to assess the relationship between pregnancy rates and antibody titres to serovar hardjo. A significant proportion of failures of conception (10 to 13 per cent, P < 0.001) were associated with MATs of 1:10 to 1:100; the overall pregnancy rate of the seronegative cows was 28.5 per cent higher (P < 0.001) than that of the cows with MATs of > or = 1:100. First service pregnancy rates showed a similar trend but the differences were significant (P < 0.05) only in cows with antibody titres > or = 1:30. An assessment of other possible risk factors for reduced pregnancy rates, such as lactation number and calving to first service interval, had no effect on the statistical results of the study or its conclusions.

Animals↗
PubMed1996

Presence of antigen and antibodies in serum and genital discharges of heifers after experimental intrauterine inoculation with Leptospira interrogans serovar hardjo.

The excretion of Leptospira interrogans serovar hardjo in cervico-vaginal mucus (CVM) or urine and the local and systemic immune responses to the organism were monitored in eight susceptible heifers after intrauterine inoculation while six similar heifers served as controls. All the heifers were inseminated at the subsequent oestrous periods. The overall percentage pregnancy rate (the number of pregnancies divided by the total number of inseminations) was lower in the infected heifers than in the controls though not significantly (33.3 v 50.0 per cent). Leptospires were detected, in either the urine or the CVM of six of the eight infected heifers during the study period of 15 weeks, either by direct immunofluorescence or dark ground microscopy; the bacteria did not grow in culture from any of the CVM samples. The control heifers remained free from evidence of infection. In the infected heifers, mean titres of at least 1:100 in a microscopic agglutination test were maintained for one to two weeks before declining to 1:10 to 1:30, whereas in serum IgG-ELISA tests (developed by using either protein or carbohydrate antigens), antibody titres of at least 1:100 were maintained throughout the study. During oestrous periods, IgA antibodies were detected more frequently in CVM with titres which were usually higher than the titres of IgG.

Agglutination Tests↗
PubMed1996

Presence of antigen and antibodies in serum and genital discharges of cows from dairy herds naturally infected with Leptospira interrogans serovar hardjo.

Samples of cervico-vaginal mucus from 163 bulling cows (group 1) and post calving discharges from 59 newly calved cows (group 2) in five dairy herds naturally infected with Leptospira interrogans serovar hardjo were examined for the presence of antigen and IgG and IgA antibodies by using two ELISA systems which were protein or carbohydrate based. Corresponding serum samples were examined for systemic immune responses by using a microscopic agglutination test (MAT) and IgG-ELISA tests. Antigen was detected by direct immunofluorescence in six of the 163 samples of cervico-vaginal mucus. Both IgG and IgA antibodies were detected by ELISA in the genital discharges with a prevalence much higher than that obtained by the MAT but lower than that observed with the serum IgG-ELISA. Combining both groups, none of the MAT-positive cattle was negative by serum-ELISA. By using the protein or carbohydrate fraction serum IgG-ELISA assays, respectively, 29 or 41 per cent of the MAT-negative cows were positive at a titre of at least 1:40. Similarly, eight or 23 samples (10 or 27 per cent) had titres of at least 1:20 in the genital discharge ELISA for IgG and IgA antibodies, respectively. The serum IgG-ELISA was the most efficient in detecting hardjo antibodies, but in group 2 the IgG- and IgA-ELISA of the post calving discharge proved to be equally effective.

Animals↗
PubMed1995

A survey of the reasons for culling pregnant cows.

This survey analysed the history of cows which were pregnant when they were slaughtered at an abattoir in south west England by sending a questionnaire to their farm of origin to determine the reason(s) for culling them and their recent reproductive history. Of the slaughtered cows, 23.5 per cent were pregnant and 26.9 per cent of these were in the third trimester. The three main reasons for culling were infertility (28.2 per cent), mastitis (21.8 per cent) and old age (15.8 per cent). In 50.9 per cent of cases the farmer thought that the cow was not pregnant. In 66 per cent of the returns the cow had run with a bull. The average age of the slaughtered cows was 7.9 years. The records were categorised as 'OK' when they were consistent with the stage of pregnancy found post mortem, as 'error' when there were slight inconsistencies and 'gross error' when there were more serious discrepancies. Thirty-six per cent of the returns were classed as 'OK', 56.6 per cent as 'error' and 27.2 per cent as 'gross error'. It is estimated that these errors represent an annual loss of 30.78 million pounds to the cattle industry of the United Kingdom.

Abattoirs↗
PubMed1995

Collection, in vitro fertilisation and culture of bovine oocytes intravaginally or in a conventional incubator.

The aim of this study was to test the feasibility of intravaginal culture for in vitro fertilisation and production of bovine embryos. Oocytes were collected from five cows, superovulated with ovine follicle stimulatory hormone (oFSH), by using a 7.5 MHz rectal linear array ultrasound transducer. From 124 follicles punctured, the oocyte recovery rate was 48 per cent. Fifty-one oocytes were placed in capsules either in the vagina or in an incubator, and cocultured with sperm for 24 hours followed by coculture with oviductal cells for 48 hours. There was no significant difference between the fertilisation rates or the cleavage rates achieved by the two systems and the mean fertilisation rate was 44 per cent. However, the fertilised oocytes did not develop beyond the eight-cell stage.

Animals↗
PubMed1995

Transport-induced stress responses in fed and fasted donkeys.

Plasma endocrine and metabolic responses to transport for 30 minutes and four hours were investigated in six fed donkeys. In the unstressed animals there was a pulsatile secretion of cortisol at two-hour intervals, from minima of 51.4 +/- 17.6 nmol litre-1 to maxima of 160.0 +/- 11.0 nmol litre-1, but during transport this pulsatility was lost and the animals' stress response was characterised by steady high concentrations of 110 to 220 nmol litre-1. The cortisol concentration decreased after the journey and remained at a minimum until the restoration of pulsatile secretion 8.5 to 10.5 hours later. The transport-induced adrenocortical response did not produce any significant changes in the plasma concentrations of triglycerides, cholesterol, glucose, total protein, albumin, globulin or urea. The donkeys' responses to transport for four hours were also investigated after they had been deprived of food for one or three days. Food deprivation alone increased plasma cortisol and triglyceride concentrations, and decreased glucose and insulin concentrations, and transport consistently, and feeding after the journey sometimes, accentuated their adrenocortical function; the changes in cortisol concentrations as a result of the journey tended to be lower than in the fed animals. Transport had no effect upon the triglyceride response to either period of fasting. Hyperglycaemia was induced by transport in four of the six donkeys fasted for one day and in all of them after three days of fasting.

Analysis of Variance↗
PubMed1995

Predicting local recurrence by correlating pre-operative mammographic findings with pathological risk factors in patients with breast cancer.

The pre-operative mammograms for 231 patients undergoing conservation surgery for breast cancer between March 1988 and September 1992 were analysed for features that may predict the presence of pathological risk factors of local recurrence (residual microscopic disease, extensive intraduct carcinoma (EIC) and lymphatic/vascular invasion). Residual microscopic disease was detected in 40% of patients and was associated with a DY mammographic pattern (p = 0.03), casting calcification (p = 0.0002) and absence of mammographic nidus (p = 0.0006). Residual microscopic disease was found in 75-88.9% of patients when two of these preoperative mammographic features were present in combination. The mean lumpectomy diameter was significantly smaller for patients with DY compared to N1 mammographic pattern on Wolfe grade (p = 0.039). Both residual disease and Wolfe grade were related to age (p = 0.0032 and p < 0.0001). EIC was found in 22% of patients and was associated with casting (p < 0.0001) and non-casting (p = 0.04) calcification, absence of mammographic nidus (p < 0.0001) and stellate mammographic nidus (p = 0.02). No significant association was found between mammographic features and lymphatic/vascular invasion. Pre-operative mammographic features can predict patients likely to have residual microscopic disease or EIC following conservation surgery for breast cancer. These patients should be selected for wider primary excision.

Adult↗
PubMed1995

Stress and reproduction in farm animals.

Transport of post-partum cows or sheep before an oestradiol-induced LH surge delayed gonadotrophin secretion possibly by affecting hypothalamic activity but not via an opioid mediated mechanism as the effect could not be reversed by naloxone. In addition, reduced LH responses to GnRH were observed in cattle during transport. In sheep, adrenocorticotrophic hormone (ACTH) also diminished the LH response to GnRH, but only when GnRH was administered 3 h after ACTH, not after 0.5 h. This finding suggests that very early suppression of LH secretion by stressors is not mediated by ACTH action at the pituitary but that immediate activation of the sympathetic nervous system may be involved. In ewes during the breeding season, repeated exposure to GnRH at intervals of 2 h during transport resulted in lower LH responses to the second and third injections. When anoestrous ewes were treated with oestradiol and GnRH while being restrained and isolated, the onset of the LH surge was delayed. The effects of hypothalamus-pituitary-adrenal hyperactivity on LH release may involve suppression of GnRH receptor activity, a reduction in releasable LH, or both factors. Studies in vitro with perifused ovine pituitaries showed that ACTH or corticotrophin releasing hormone markedly suppressed LH secretion in response to the second of two exposures to GnRH. This occurred with pituitaries obtained from anoestrous ewes irrespective of prior treatment with oestradiol, suggesting that compounds from the hypothalamus-pituitary-adrenal do not exert effects on the oestradiol-sensitizing mechanisms on the pituitary. In conclusion, stressors affect reproductive function via actions at the hypothalamus as well as impairing pituitary LH release induced by GnRH.

Adrenal Glands↗
PubMed1994

Comparative evaluation of ovarian structures in cattle by palpation per rectum, ultrasonography and plasma progesterone concentration.

The aims of this study were to determine the relationship between the ultrasonographic determination of corpora lutea and the plasma progesterone profile of cyclic cows during an oestrous cycle, and to compare the accuracy of detection of normal and abnormal ovarian structures by ultrasonography and palpation per rectum, based on the plasma progesterone profile. The ovaries of six lactating cyclic dairy cows were scanned and blood samples were obtained three times a week for one month. There was a high correlation (r = 0.85) between the diameter of the corpus luteum and the plasma progesterone concentration, but on days -3 and -2 (oestrus = day 0) the diameter was the same as mid-luteal values but it was functionally inactive (plasma progesterone < 0.5 ng/ml). The accuracy of palpation per rectum and ultrasonography for determining the presence and age of the corpora lutea was investigated in 34 cows by using the plasma progesterone concentration and the dissection of ovaries post mortem as standards. The sensitivity, specificity and positive predictive value of palpation for identifying mid-cyclic corpora lutea were 85 per cent, 95.7 per cent and 89.5 per cent, respectively. Ultrasonography had a sensitivity of 95 per cent, a specificity of 100 per cent and a positive predictive value of 100 per cent. Twenty-nine cows were diagnosed by palpation per rectum as having either follicular or luteal cysts. During ultrasonography, an ovarian cyst was defined as a non-echogenic structure at least 5 mm in diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Relationship between plasma insulin and triglyceride concentrations in hypertriglyceridaemic donkeys.

Hyperinsulinaemia is a commonly-observed characteristic of insulin resistance, and a reduction in insulin sensitivity is thought to be either a causative and/or symptomatic feature of equine hyperlipaemia. A positive correlation (r = 0.545, P = 0.0015) existed between plasma insulin and triglyceride concentrations determined in 31 donkeys with naturally occurring hyperlipidaemia/hyperlipaemia. Greater insulin values tended to occur in the animals with an overweight body score. Inter-animal variation in insulin concentrations, however, prevented the identification of any differences either within hypertriglyceridaemic donkeys (when classified by clinical condition, date of arrival to a sanctuary and eventual outcome after treatment) or between groups of normotriglyceridaemic (n = 6) and experimentally fasted hypertriglyceridaemic (n = 5) donkeys. Determination of basal plasma insulin concentrations may not provide an accurate assessment of underlying insulin sensitivity. Alternatively, hyperinsulinaemia may be evident only in animals with established insulin resistance.

Animals↗
PubMed1994

Cell adhesion molecules in oesophageal epithelium.

The distribution of a range of integrins, E-cadherin, and carcino-embryonic antigen (CEA) like molecules in normal human oesophageal epithelium was investigated immunohistochemically on frozen sections of endoscopic biopsy specimens. The integrin subunits alpha 2, alpha 3, alpha 6, alpha v, beta 1, and beta 5 were expressed throughout the epithelium. There was strong expression of alpha 2, alpha 3, and beta 1 subunits in the basal cell layer and for all the subunits studied the intensity of the staining decreased as cells moved towards the lumen. The heterodimer alpha v beta 3 was expressed weakly in the basal aspect of the basal cell layer only. The CEA molecules were not present in the basal cells layer but there was weak expression in the prickle cell layer and strong positivity in the mature functional layer. E-cadherin was found throughout the epithelium but was weakly expressed at the basal aspect of the basal cells layer and showed strong positivity in the prickle cell and squamous cell layers. These results indicate that cell-cell (E-cadherin, CEA) and cell-matrix (integrins) adhesion molecules show a well defined spatial pattern of immunoreactivity in the oesophageal mucosa and may play a part in the maintenance of normal tissue architecture and physiological homeostasis.

Cadherins↗
PubMed1994

Opioids and suckling in relation to inhibition of oestradiol-induced LH secretion in postpartum ewes.

The effects of time postpartum and suckling status on the oestradiol-induced LH surge in ewes and some of the possible mechanisms involved were investigated. Lambs were removed from nonsuckled ewes at parturition (day 0) and the ewes hand-milked 12 and 48 h later to prevent discomfort. Nonsuckled ewes on day 1, 7, 14 or 28, and suckled ewes on day 7 or 28 postpartum were injected i.m. with 50 micrograms oestradiol benzoate (hour 0). A further eight suckled ewes were given oestradiol on day 1 (as above), and four were also given naloxone (1 mg kg-1 h-1) from 10 until 14 h after administration of oestradiol benzoate. There was no LH surge in response to oestradiol on day 1. In nonsuckled ewes the onset of the LH surge was significantly (P < 0.05) delayed when oestradiol was administered on day 7 (17.4 +/- 1.5 h), compared with when it was injected on days 14 and 28 postpartum (14.4 +/- 1.7 and 14.0 +/- 1.4 h). The LH surge was also delayed (P < 0.05) when oestradiol was administered on day 7 (18.0 +/- 2.8 h) in suckled ewes. There was no difference in the duration or amplitude of the LH surge with time postpartum in nonsuckled ewes. Suckling significantly (P < 0.05) reduced the amplitude of the LH surge on both day 7 (21.0 +/- 2.4 versus 26.4 +/- 2.3 ng ml-1) and day 28 (23.6 +/- 3.2 versus 28.8 +/- 2.9 ng ml-1), but had no effect on the onset or duration of the surge.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Transport stress delays the oestradiol-induced LH surge by a non-opioidergic mechanism in the early postpartum ewe.

The present study was designed to investigate whether transport, a mild environmental stressor, could affect the oestradiol-induced LH surge in postpartum ewes and, if so, the mechanism involved. Welsh Mountain ewes, with lambs removed at parturition (day 0) and hand-milked 12 and 48 h later, were given 50 micrograms oestradiol benzoate intramuscularly at various times postpartum. Blood samples were taken via an indwelling jugular venous catheter every 2 h from 8 to 24 h after oestradiol injection. All results are given as means +/- S.D. On day 1 oestradiol was unable to induce an LH surge in any ewe. Transport (10-14 h after oestradiol) delayed the onset of the oestradiol-induced LH surge on day 14 (17.5 +/- 1.7 vs 14.4 +/- 2.0 h, n = 5 each; P < 0.05), but not on day 28 (14.9 +/- 2.0 vs 14.0 +/- 2.4 h, n = 5 out of 7). Transport had no effect on the amplitude of the surge on either day. Naloxone treatment (1 mg/kg per 2 h) was unable to prevent the delay caused by transport (18.0 +/- 1.1 vs 17.5 +/- 1.7 h, n = 8 each), and did not affect the amplitude of the surge (28.4 +/- 5.3 vs 28.1 +/- 2.3 ng/ml, n = 8 each).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The effect of vaccination against Leptospira interrogans serovar hardjo infection at the time of service on pregnancy rates in dairy cows.

Fertility data from 16 dairy herds vaccinated against hardjo infection were used to assess pregnancy rates in cattle vaccinated around the day of mating. There was no improvement in pregnancy rates 30-60 d after vaccination. Pregnancy rates in the period 5 d before and 10 d after vaccination were statistically lower than those found in 30-60 d around vaccination.

Animals↗