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Biomedical subjects

D R Lindsay

Publications and source records attributed to D R Lindsay.

At least 19 recordsLinked to original sources
PubMed2004

Natural methods for increasing reproductive efficiency in small ruminants.

This paper describes three strategies to improve the reproductive performance of small ruminants in ways that lead to "clean, green and ethical" animal production. The first is aimed at control of the timing of reproductive events for which we turn to the socio-sexual inputs of the "male effect" to induce synchronised ovulation in females that would otherwise be anovulatory. The second strategy, "focussed feeding", is based on our knowledge of the responses to nutrition and aims to develop short programs of nutritional supplements that are precisely timed and specifically designed for individual events in the reproductive process, such as gamete production, embryo survival, fetal programming and colostrum production. The third strategy aims to maximise offspring survival by a combination of management, nutrition and genetic selection for behavior (temperament). All of these approaches involve non-pharmacological manipulation of the endogenous control systems of the animals and complement the detailed information from ultrasound that is now becoming available. The use of such clean, green and ethical tools in the management of our animals can be cost-effective, increase productivity and, at the same time, greatly improve the image of meat and milk industries in society and the marketplace.

Animal Feed↗
PubMed2004

Nutrition and colostrum production in sheep. 1. Metabolic and hormonal responses to a high-energy supplement in the final stages of pregnancy.

We tested the hypothesis that supplementation with cracked maize during the last week of pregnancy would provide ewes with a substrate for glucose and enhance the synthesis of lactose and, consequently, their production of colostrum. Thirty single- and 30 twin-bearing ewes were fed lucerne hay and half of each group was supplemented daily with 0.75 kg per head cracked maize during the last week of pregnancy. Colostrum production and the endocrine patterns in the animals were investigated. Supplementation with maize more than doubled the mass of colostrum available at birth in unsupplemented ewes: 339 v. 145 g in single-bearing ewes and 536 v. 197 g in twin-bearing ewes (P < 0.001). The total colostrum produced in the 10 h after birth was also significantly increased by supplementation: 730 v. 475 g in single-bearing ewes and 1259 v. 631 g in twin-bearing ewes (P < 0.01). The colostrum in the supplemented ewes was also more liquid with a viscosity score of 5.8 compared with 5.7 and 4.5 in unsupplemented single- and twin-bearing ewes (P < 0.01). Supplemented ewes had higher concentrations of lactose in their colostrum at parturition (2.6% v. 1.8% in single-bearing ewes and 2.5% v. 1.4% in twin-bearing ewes; P < 0.01). The plasma concentrations of progesterone and growth hormone in supplemented ewes were lower, whereas those of IGF-I and insulin were higher, all consistent with a higher capacity to produce colostrum. It is concluded that a high-energy supplement, like maize, fed to ewes in the last week of gestation increases their capacity to produce colostrum for their lambs, particularly for ewes bearing twins.

Animal Feed↗
PubMed2004

Nutrition and colostrum production in sheep. 2. Metabolic and hormonal responses to different energy sources in the final stages of pregnancy.

Lupins and maize, with similar concentrations of metabolisable energy, should produce similar responses in colostrum production at parturition when fed during the last week of pregnancy, but, in the present study, we tested the proposal that the physical form of whole lupins would restrict intake and, therefore, the response compared with cracked lupins or maize. Fifty-five twin-bearing ewes were divided into four groups: in the last 15 days of pregnancy, 14 were fed whole lupins, 13 were fed cracked lupins, 14 were fed cracked maize and 14 received no supplement. The cracked supplements were fed in increasing amounts for 6 days to avoid acidosis. The whole lupins were fed only from Day -8. All supplementary grains increased the intake of metabolisable energy by >35%, but only ewes eating maize accumulated significantly more colostrum at parturition: control, 207 g; cracked maize, 452 g; cracked lupins, 206 g; whole lupins, 231 g (P < 0.05). Plasma urea concentrations were extremely high (approximately 10 mmol L(-1)) for both groups eating lupins and approximately double those of control ewes or those receiving maize ( P < 0.05). We conclude that gut distention is not a cause of a poor response to lupins, but the ammonia associated with near-toxic concentrations of plasma urea may be affecting the production of colostrum.

Animal Feed↗
PubMed2000

Subarachnoid meperidine (Pethidine) causes significant nausea and vomiting during labor. The Duke Women's Anesthesia Research Group.

BACKGROUND: The combined spinal-epidural (CSE) technique using bupivicaine-fentanyl has become an established method of pain control during parturition. One limitation is the relatively short duration of effective analgesia produced by bupivicaine-fentanyl. In contrast, subarachnoid meperidine has been shown to provide a long duration of anesthesia in nonobstetric patients. Therefore, the authors tested the hypothesis that subarachnoid meperidine produces a significant increase in the duration of analgesia compared with bupivicaine-fentanyl. METHODS: Based on a power analysis of preliminary data, the authors intended to recruit 90 patients for the study, randomized to three groups: 2.5 mg bupivicaine-25 microg fentanyl, 15 mg meperidine, or 25 mg meperidine. However, after enrolling 34 patients, the study was discontinued because of a significant increase in nausea or vomiting in the study patients. RESULTS: Nausea or vomiting was substantially increased in both meperidine groups compared with the bupivicaine-fentanyl group: 16 with nausea or vomiting in the meperidine groups (n = 21), compared with 1 in the bupivicaine-fentanyl group (n = 11), P = 0.0011. The mean duration of analgesia provided by 25 mg meperidine was 126 +/- 51 min, compared with 98 +/- 29 min for bupivicaine-fentanyl and 90 +/- 67 min for 15 mg meperidine. These data were not significant (P = 0.27). CONCLUSIONS: Although intrathecal meperidine could potentially prolong subarachnoid analgesia during labor, its use was associated with a significant incidence of nausea or vomiting. These data do not support the use of subarachnoid meperidine in doses of 15 or 25 mg for labor analgesia.

Adult↗
PubMed1999

Maternal behaviour and the survival of lambs in superfine wool sheep.

Superfine merino lambs from superfine and medium-wool ewes were compared to test the hypothesis that superfine ewes have poorer maternal capacity than broader wool ewes. All lambs were sired by one ram using artificial insemination in the superfine ewes and embryo transfer in the medium-wool ewes. This ensured a similar genetic background in all lambs. Single born lambs from the superfine ewes were 1.5 kg lighter than those from medium-wool ewes (3.3 v. 4.8 kg, P<0.05). Compared with the medium-wool ewes, in the first hour after birth the superfine ewes spent less time grooming their lambs (8.7 v. 25.2 min, P<0.05) and more time separated from them (21.3 v. 0.0 min, P<0.05). The lambs of superfine ewes also stood and attempted to suck for less time (17.7 and 2.4 min v. 32.4 and 10.5 min, P<0.05) than those of medium-wool ewes. Twenty-nine per cent of lambs from superfine ewes died in the first 4 weeks after birth compared with only 4% of lambs from medium-wool ewes. It was concluded that superfine ewes lost more lambs than medium-wool ewes and that this was associated with their lambs being smaller at birth and with the ewes being poorer mothers.

Animals↗
PubMed1997

Development of a preferential relationship with the mother by the newborn lamb: importance of the sucking activity.

Lambs develop a preferential relationship with their mothers within 24 h after birth. In a first experiment, we attempted to determine whether neonatal sucking was a potent reinforcer in the establishment of this preference by temporarily covering the udders of ewes after parturition. Lambs were assigned to one of three treatments: they had free access to the udder (group 1) or were prevented from sucking either between birth and 6 h afterward (group 2) or between 12 and 18 h after birth (group 3). Measurements of cholecystokinin plasma levels at birth and at 6 and 18 h showed that all lambs ingested some colostrum when the udder was made accessible. When tested in a two-choice test situation at 24 h of age, lambs from group 1 spent significantly more time near their mothers than near the alien ewes, those from group 2 did not show any discrimination, and lambs from group 3 clearly preferred the alien ewes. At 2 days of age, lambs from groups 1 and 3 showed a strong preference for their mothers, whereas those from group 2 still displayed no preference. In a second experiment, we attempted to determine whether sucking also had a reinforcing value in the maintenance of this preference. Lambs were assigned to one of three treatments: they had free access to the udder (group 1) or were prevented from sucking for 6 h either at birth (group 2) or at the age of 3 days (group 3). Lambs from group 2 did not discriminate between their own and alien dams when tested at 24 h of age, unlike those of groups 1 and 3. When a second test was performed at 4 days of age, all the lambs showed a strong preference for their dams. We concluded that sucking has strong rewarding properties in the establishment of a preferential relationship with the mother by the lamb. On the other hand, the maintenance of this preference does not rely on sucking as strongly.

Animals↗
PubMed1997

Semen production by the emu (Dromaius novaehollandiae). 1. Methods for collection of semen.

Two methods for collecting semen from male emus using an artificial cloaca (AC) have been developed. In the first method, the male mounts the female teaser and the collector effects erection and subsequent ejaculation using the AC. The second method takes advantage of the development of sexual behaviour directed towards the semen collector and semen is collected when the male mounts the collector's back. Eight of 11 males were successfully trained with teasers and 5 of the 7 males trained without teasers ejaculated successfully. The ease of training varied between birds. The use of a teaser was very valuable, as the crouching behavior of the teaser elicited mating attempts in every male. The training and collection of semen was done by one person. Both methods can be used for routine collection of semen, as they take advantage of natural stimulation and the voluntary ejaculation reflex to which the birds adapted readily.

Animals↗
PubMed1997

Semen production by the emu (Dromaius novaehollandiae). 2. Effect of collection frequency on the production of semen and spermatozoa.

This experiment tested the hypothesis that frequent collection of semen from emus would increase the total output of semen and spermatozoa over less frequent collection. Semen was collected from trained male emus using an artificial cloaca. In Experiment 1, semen was collected from males every 4th d (96-h interval), every 2nd d (48-h interval), and every day (24-h interval) for 16 d. In Experiment 2, semen was collected daily (24-h interval), twice daily (6-h interval), and three times per day (3-h interval) over 6 d. Twice-daily collections yielded twice as much volume and number of spermatozoa than daily collections. Collecting semen three times per day did not yield extra semen, as it adversely affected the libido of males. Twice-daily collections appears to yield the optimum output over the 6 d of this experiment, but longer periods of collection need to be studied.

Animals↗
PubMed1995

Isolation of Dermatophilus congolensis phage from the 'lumpy wool' of sheep in Western Australia.

A lytic phage with species-specific activity was isolated from wool samples infected with the actinomycete Dermatophilus congolensis, the agent of 'lumpy wool', collected from properties in Western Australia. The physiochemical properties, plaque morphology, host range and particle morphology of the phage isolated were characterized. The isolated phage reduced the cell numbers of Dermatophilus congolensis on infected wool samples in vitro. It may therefore have potential as a biocontrol agent of dermatophilosis.

Actinomycetales↗
PubMed1991

Ovariectomized does do not require progesterone priming for oestrous behaviour.

Ewes need to be primed with progesterone in order to achieve sensitivity to oestrogen. This relationship was examined in goats. In experiment 1 the median effective dose of oestradiol benzoate (ODB) required to induce oestrus during the breeding season (July) in progesterone-primed ovariectomized does was 15 micrograms, a dose similar to that reported to be required in ewes. In experiment 2 (initiated in March) the requirement for progesterone priming before injection of ODB to induce oestrus after a period without any exogenous hormone treatment, was compared in goats and sheep. Without progesterone priming, ovariectomized does were sensitive to doses of ODB between 20 and 80 micrograms, whereas ewes were not. This indicates that, unlike sheep, goats may not require progesterone priming in order to exhibit oestrus at the beginning of the breeding season. After being primed with progesterone, ewes were more sensitive to ODB than were does. In primed ewes the median effective dose of ODB was 12 micrograms whereas in does it was 27 micrograms. These differences may be due to a seasonal effect on oestrous behaviour or differences in sensitivity to oestrogen between the species.

Animals↗
PubMed1988

Secretion of LH, FSH and oestradiol-17 beta during the follicular phase of the oestrous cycle in the ewe.

Plasma concentrations of LH, FSH and oestradiol-17 beta were measured in blood samples taken at 15 min intervals for 48 h during the follicular phase of four Merino ewes. The amplitude of pulses of LH and the mean concentration of LH were higher at the beginning of the follicular phase, 36-24 h before the preovulatory surge of LH (amplitude 2.4 ng ml-1, mean concentration 3.9 ng ml-1), than at the end, 24-0 h before the preovulatory surge (amplitude 1.2 +/- 0.1 ng ml-1; mean concentration 1.4 +/- 0.1 ng ml-1). There was no change in the inter-pulse interval during this time (mean 74 +/- 5 min). Over the same period, oestradiol levels increased from 7-8 pg ml-1 to a peak of 10-15 pg ml-1. Mean FSH concentrations declined (36-24 h: 3.6 ng ml-1 vs 24-0 h: 1.8 +/- 0.3 ng ml-1) before rising at the time of the preovulatory surge of LH and again 24 h later. It was concluded that the biphasic response of LH to oestrogen that is seen in ovariectomized ewes may also operate during the follicular phase of the oestrous cycle in entire ewes.

Animals↗
PubMed1988

The number of spermatozoa, the number of ovulations per ewe, and immunization against androstenedione affect fertility and prolificacy of sheep.

Ewes that were untreated, fed lupins or fed lupins and immunized against androstenedione were artificially inseminated. The percentage of ewes pregnant at 36-45 days after insemination (fertility) was 8% higher in ewes that had more than one ovulation than in those that had only one ovulation. Maximum fertility was achieved with 50 x 10(6) spermatozoa and this did not vary with the number of ovulations that ewes had. Among the pregnant, twin-ovulating ewes, embryo survival increased as the number of spermatozoa inseminated increased from 25 x 10(6) to 400 x 10(6). Immunization of ewes against androstenedione increased ovulation rate but reduced fertility, and reduced embryo survival among twin-ovulation ewes.

Androstenedione↗
PubMed1988

Effects of breed, ovarian steroids and season on the pulsatile secretion of LH in ovariectomized ewes.

The effects of season and of oestradiol and progesterone on the tonic secretion of LH were studied in ovariectomized Merino and Suffolk ewes, two breeds which differ markedly in the seasonal pattern of their reproductive activity. In the absence of exogenous steroids, the frequency of LH pulses was lower and the amplitude of the pulses was higher in anoestrus than in the breeding season for Merino and Suffolk ewes 30 days after ovariectomy. In long-term (190 days) ovariectomized ewes, this seasonal change in LH secretion was observed in Suffolk ewes only. During seasonal anoestrus, treatment of ewes with subcutaneous oestradiol-17 beta implants (3, 6 or 12 mm in length) decreased the frequency of LH pulses in a dose-dependent manner, with Suffolk ewes being far more sensitive to the inhibitory effects of oestradiol than Merino ewes. The lowest dose of oestradiol (3 mm) had no effect on the secretion of LH in Merino ewes, but reduced secretion in Suffolk ewes. Treatment of ewes with the highest dose of oestradiol (12 mm) completely abolished LH pulses in Suffolk ewes, whereas infrequent pulses remained evident in Merino ewes. During the breeding season, oestradiol alone had no effect on the pulsatile release of LH in either breed, but in combination with progesterone there was a significant reduction in LH pulse frequency. Progesterone effectively decreased LH secretion in both breeds in both seasons. It was concluded that differences between breeds in the 'depth' of anoestrus could be related to differences in the sensitivity of the hypothalamus to both negative feedback by oestradiol and the direct effects of photoperiod.

Animals↗
PubMed1988

Reproductive behaviour in survival: a comparison between wild and domestic sheep.

The recorded behaviour of wild species of Ovis at the beginning of the breeding season supports the proposal that mating is synchronized by the 'ram effect', a phenomenon already described in domestic sheep. Animals separate into exclusive male flocks, and flocks of females and young animals for most of the year. They reunite just before the rutting season. At lambing there appear to be behavioural mechanisms that ensure that ewes lamb in close proximity to one another. It is hypothesized that these behavioural characteristics of wild sheep help protect the newborn and that much of the reproductive and maternal behaviour of domestic sheep may be traced to comparable behaviour in wild species.

Animals↗
PubMed1984

Changes in photoperiod and nutrition and their effect on testicular growth of rams.

Groups of 6 Ile-de-France rams were housed in light-proof rooms and subjected in a factorial design to two light regimens, 180 degrees out of phase, and two levels of protein in their diets. The daily duration of daylight was varied sinusoidally to produce 6-month years with 'winters' of 8 h light and 'summers' of 16 h light. The diets were formulated to supply 50% above or 25% below maintenance requirements in protein. Testicular diameter and volume increased with decreasing light and decreased with increasing light but the diet had no effect. The frequency of LH pulses was measured monthly and was high (3/12 h per ram) when the daylight was being reduced and low (1/12 h per ram) when it was increased. At the extremes of the duration of dark or light the frequency of pulses was around 1.6/12 h per ram, regardless of the duration of light. The two diets had no effect on testicular dimensions but rams fed the 'high' protein diet had a total of 175 LH pulses, which was significantly higher (P less than 0.05) than the 131 pulses recorded from rams on the 'low' protein diet. It is concluded that, in these '6-month years', decreasing light stimulates LH pulsatility and testicular growth and increasing light is inhibitory. Pulsatility of LH appears to be influenced by the protein level in the diet.

Animal Nutritional Physiological Phenomena↗
PubMed1983

Vaginal stimulation: an important determinant of maternal bonding in sheep.

The immediate induction of the full complement of maternal behavior in nonpregnant ewes primed with estrogen and progesterone has been obtained after 5 minutes of vaginal-cervical stimulation. A similar period of such stimulation given to recently parturient ewes, after the development of selective bonding to their own lambs, reversed their rejection behavior of alien lambs and produced a state of plasticity in maternal behavior, such that ewes receiving vaginal stimulation would accept and adopt alien lambs. These findings implicate vaginal-cervical stimulation as playing a role in the onset of maternal behavior.

Animals↗
PubMed1983

Effects of progesterone on the responses of Merino ewes to the introduction of rams during anoestrus.

The effects of progesterone on the responses of Merino ewes to the introduction of rams during anoestrus were investigated in two experiments. In the first experiment, the introduction of rams induced an increase in the levels of LH in entire ewes. The mean levels increased from 0.68 +/- 0.04 ng/ml (mean +/- s.e.m.) to 4.49 +/- 1.32 ng/ml within 20 min in ewes not treated with progesterone (n = 10). In ewes bearing progesterone implants that provided a peripheral concentration of about 1.5 ng progesterone per millilitre plasma, the LH response to the introduction of rams was not prevented, but was reduced in size so that the concentration was 1.38 +/- 0.15 ng/ml after 20 min (n = 5). Progesterone treatment begun either 2 days before or 6 h after the introduction of rams and maintained for 4 days prevented ovulation. In the second experiment ovariectomized ewes were used to investigate further the mechanism by which the ram evoked increases in tonic LH secretion. In ovariectomized ewes treated with oestradiol implants, the introduction of rams increased the frequency of the LH pulses and the basal level of LH. In the absence of oestradiol there was no significant change in pulse frequency but a small increase in basal levels. Progesterone again did not prevent but reduced the responses in ewes treated with oestradiol. It is suggested that following the withdrawal of progesterone treatment, the secretion of LH pulses in response to the ram effect would be dampened. This effect could be a component of the reported long delay between the introduction of rams and the preovulatory surge of LH in ewes treated with progesterone. Continued progesterone treatment prevented ovulation, probably by blocking positive feedback by oestradiol.

Animals↗