PubMed Health⌕ Search

Biomedical subjects

R J Love

Publications and source records attributed to R J Love.

At least 19 recordsLinked to original sources
PubMed1993

Seasonal effects on fertility in gilts and sows.

The ancestral wild pig is a short day length seasonal breeder. The domestic pig appears to have retained some of this seasonality as evidenced by a reduction in fertility during the summer-autumn period. The most important aspect of this seasonality is a reduction in the number of mated sows that farrow. Many of these sows conceive and embryos develop normally for 20-25 days before pregnancy is terminated and the sow returns to oestrus (25-35 days after mating). In other species, transduction of photoperiodic information is achieved by release of melatonin during the dark period. In the pig, the pattern of melatonin secretion and the subsequent hypothalamo-pituitary-gonadal responses appear to be more complex. A relatively high light intensity is required for pigs to generate a distinct diurnal melatonin rhythm and they appear unable to respond appropriately to abrupt changes in photoperiod. Pigs on restricted feeding and maintained under long photoperiods (but not under short photoperiods) have higher concentrations of melatonin than do similarly maintained pigs fed ad libitum. Continuous release melatonin implants have a deleterious effect on farrowing rate, suggesting that the abnormally high melatonin concentrations observed in sows in summer-autumn play a role in the pathogenesis of seasonal infertility. Ad libitum feeding of sows during the first few weeks of pregnancy may prevent the increase in melatonin concentrations and so remove the seasonal influence on fertility. The pituitary response to different photoperiods is also somewhat confusing. Although there is some evidence of increased sensitivity to the negative feedback of ovarian steroids in the prepubertal gilts and weaned sows during summer-autumn, LH concentrations are increased in early pregnant sows. It is proposed that the failure of sows to maintain pregnancy in summer-autumn results from disruption of maternal recognition of pregnancy causing regression of the corpora lutea, loss of pregnancy and return of the sow to oestrus.

Animals↗
PubMed1990

Facial growth in males 16 to 20 years of age.

Postpubertal craniofacial skeletal and dental changes were examined from lateral cephalograms taken when subjects were 16, 18, and 20 years of age. The sample consisted of males with no previous orthodontic treatment who had Class I skeletal and dental characteristics. Mandibular growth was found to be statistically significant for the age periods of 16 to 18 years and 18 to 20 years. Growth from 16 to 18 years was greater than that from 18 to 20 years. Maxillary and mandibular growth were highly correlated at each age period. However, overall mandibular growth was approximately twice that of overall maxillary growth. Mandibular growth was found to involve an upward and forward rotation, a result of posterior vertical growth exceeding anterior vertical growth. Lower incisors were found to tip lingually with increasing age. Incremental changes in mandibular cephalometric measurements were found to be equivalent when measured from either articulare or condylion, indicating the interchangeability of the landmarks for growth estimates.

Adolescent↗
PubMed1990

Fertility of sows mated on different days of the week.

The farrowing rates resulting from matings on different days of the week were determined for a 2800-sow intensive piggery in both 1983 and 1984. The results showed that sows mated early in the week achieved a significantly higher farrowing rate than sows mated late in the week (P less than 0.0001). During the seasonal (summer to autumn) infertility period, Wednesday matings resulted in a poor farrowing rate whereas for the rest of the year farrowing rates following Wednesday matings were similar to those for Sunday Monday and Tuesday matings. Consistent results were obtained for data from both years. It is proposed that the stress of regrouping unmated sows on Wednesday to accommodate newly weaned sows is responsible for this decrease in fertility. This study illustrates how detailed analysis of farrowing rates on a day of mating basis can identify a problem which is otherwise masked by weekly data.

Animals↗
PubMed1990

Premature farrowings caused by feeding cottonseed meal.

Increasing the level of cottonseed meal (CSM) in sow diets from less than 5% to 10% increased the incidence of premature farrowings (gestation length less than 111 days) from 1.1% to 2.7% (p less than 0.001) and reduced the mean gestation length from 114.07 +/- 1.53 to 113.70 +/- 1.59 days (p less than 0.0001). Survival of piglets born prematurely was poor. After removal of CSM from the diet there was a residual effect lasting several weeks before the gestation length returned to normal. Experimental feeding of diets containing 20% and 40% CSM to small groups of sows caused significant shortening of gestation length and 3 of 26 sows fed 40% CSM farrowed prematurely. The mechanism by which CSM causes this effect has yet to be determined.

Animal Feed↗
PubMed1989

Biotin studies in pigs. 5. The post-ileal absorption of biotin.

Six pigs were given a biotin-deficient diet (10 micrograms biotin/kg) for 14 weeks. The pigs were given the same diet for a further 42 d with one of three biotin treatments: no supplement, 400 micrograms biotin/d given orally, 400 micrograms biotin/d infused into the caecum. The concentrations of biotin in the liver, kidney and heart, at the conclusion of 42 d were greater in the pigs given the oral biotin supplement than in the unsupplemented pigs. The values for the pigs given the caecal infusion of biotin were intermediate. The excretion of biotin in faeces was increased from 35 to 101 micrograms/d by the caecal biotin infusion, and the urinary excretion was increased from 35 to 83 micrograms/d. The oral dose of biotin increased urinary biotin excretion from 35 to 345 micrograms/d, but there was no change in faecal biotin excretion. Two pigs were fitted with ileal cannulas and catheters in the vena cava. The pigs were given a dose of [14C] biotin either into the caecum, when the ileum was occluded by a bladder catheter, or orally. [14C] biotin was measured in the urine and plasma and showed that post-ileal biotin absorption was 8% as efficient as the absorption of biotin after oral dosing.

Animals↗
PubMed1986

Some epidemiological features and effects on reproductive performance of endemic porcine parvovirus infection.

The time of development of demonstrable antibody to porcine parvovirus (PPV) was determined for 661 gilts entering the breeding herd in a 2800 sow intensive piggery; 13.2% of these gilts did not have detectable antibody to PPV when first introduced into the breeding herd at 25 to 26 weeks of age. Exposure to PPV was found to vary in different sheds and even in different areas within a shed. Gilts that developed antibody to PPV during the first third of pregnancy were not adversely affected. Those that developed antibody during the middle third of pregnancy had fewer piglets born alive, more stillborn piglets and more mummified foetuses.

Animals↗
PubMed1985

Porcine atrophic rhinitis.

In snouts of pigs from 5 of 8 piggeries in New South Wales examined, there was evidence of severe atrophic rhinitis. In 220 pigs examined from one piggery there was no correlation between the severity of atrophic rhinitis and growth rate or back-fat thickness. There was also no correlation between the extent of lung pathology and back-fat thickness. Pleurisy or pericarditis did cause a significant reduction in growth rate.

Animals↗
PubMed1983

Reading problems in chronic aphasia.

Thirty-five aphasic subjects who were 1 year or longer post onset of brain injury were given a battery of reading tests which was composed of recognition and oral reading tests for letters, words, sentences, and paragraphs, and comprehension tests for sentences and paragraphs. Results indicated a residual reading disorder or alexia in all subjects, with comprehension tests producing the highest error rate, oral reading tests second, and then recognition tests. Reading ability was found to be related to overall language skill, level of education, and oral reading ability. Results are discussed in light of current theories of reading and future research needs.

Aphasia↗
PubMed1983

Evaluation of a gel diffusion precipitin test for porcine parvovirus.

The use of a gel diffusion precipitin (GDP) test for the detection of porcine parvovirus (PPV) infection in pigs is described. The close correlation between gel diffusion precipitin and haemagglutination inhibiting (HI) antibody titres indicates that, with careful standardisation, a high level of sensitivity can be achieved with the GDP test and that it is a simple and relatively inexpensive alternative to the more commonly used HI test. Experimental infection of 2 groups of pigs showed that GDP and HI antibody responses were closely correlated and that GDP antibodies to PPV persisted for at least 41 weeks after infection. In a commercial herd study, serological evidence of declining passive immunity and subsequent acquisition of active immunity was demonstrated by measuring the GDP and HI antibody titres in sequential serum samples of pigs from a known PPV endemic farm. The GDP test described was shown to be less sensitive than haemagglutination (HA) in the detection of viral antigen but was, nevertheless, considered useful as a simple screening test for the amounts of antigen usually present in PPV infected mummified foetuses.

Animals↗
PubMed1981

Seasonal infertility in pigs.

A retrospective study of a seasonal infertility problem in a large intensive piggery showed that during the periods of infertility there was a significant increase in the numbers of sows returning to oestrus in the periods 22 to 37 and 44 to 53 days after mating. A prospective study showed that the majority of sows affected by the seasonal infertility problem returned to oestrus during the fourth of fifth week after mating. However, some sows did not exhibit a normal behavioural oestrus at this time and so the oestrus was undetected until and sow completed another oestrous cycle accounting for the second period of increased returns at 44 to 53 days. Some sows failed to exhibit behavioural evidence of oestrus at this second to exhibit behavioural evidence of oestrus at this second oestrus and so had very prolonged mating to detectable oestrus intervals.

Animals↗