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To determine the chemical body composition of Thoroughbred foals born in two consecutive years, and to investigate several techniques used to predict body composition in foals born in the second year, with particular reference to fat.The chemical composition of 20 foals at around 160 days of age, born in two years, was determined. In vivo techniques to predict body composition were assessed in 23 foals born in Year 2, before and after euthanasia; 10 of these foals were used for chemical body composition analysis. Techniques to assess body composition in vivo included liveweight (LW), overall and regional condition scores, ultrasonic fat thickness measurements over the ribs and rump, linear measurements and bioelectrical impedance analysis. Correlations were determined between ultrasonic fat thickness, and bioelectrical impedance analysis, before and after euthanasia. Stepwise regression analysis was used to determine the relationships between in vivo techniques used to assess body composition and the chemical body composition of 10 animals.Foals used for analysis of chemical composition weighed between 220.5 and 260.0 kg before euthanasia. Fat content ranged from 5.5-13.0% of the partial empty bodyweight (LW less head, gastrointestinal contents, distal limbs and skin). Fillies had significantly more fat mass and percentage fat than colts (p=0.031 for both measurements). The mean chemical composition of the fat-free partial empty body was 73.2% (SD 0.6) water, 22.7% (SD 0.9) protein, and 4.1% (SD 0.4) ash. Most of the variation in the concentration of empty body water was associated with variation in the concentration of fat (p0.001). The live animal overall condition scores were correlated with fat mass and concentration (p=0.006 and p=0.013, respectively; n=10). Condition score over the rib region was highly correlated with fat mass and fat concentration (p=0.004 and p0.001; n=10). Ultrasound measurements taken 10 cm cranial to the tailhead and 4 cm from midline, used to assess the thickness of rump fat, were correlated with condition score (p=0.001), and explained 71% of the variation in body fat mass (p=0.002; n=10).Nearly 50% of the variation in fat-free mass and partial empty body water mass were associated with variation in the impedance indices calculated from length and bioelectrical impedance analysis measurements (p=0.023 and p=0.026, respectively; n=10).At around 42% of expected mature weight, fillies were significantly more fat than colts. Condition scores were correlated with partial empty body fat mass, and there was a trend for higher scores in fillies compared to colts. Much of the variation in water or protein mass of the partial empty body could be explained by variations in LW.Measurements of LW, rump fat and condition score are useful predictors of the chemical composition of foals at 5 months of age.

Objective To determine the changes in Ca, P, Mg, Na, K, S, Cu, Fe and Zn concentrations of milk during the lactation in pasture-fed Thoroughbred mares and then calculate the dietary mineral requirements of the sucking foal and the lactating mare. Procedure Milk was sampled on days 1, 3, 7, 14, 21, 28 and at various times between 55 to 65, 85 to 95 and 135 to 150 days after parturition from 21 pasture-fed mares. The concentrations of macro- and micro-elements in the milk were determined by inductively coupled plasma emission spectrometry. Results Concentrations (mg/L) of these elements were highest in colostrum (Mg 302, Na 561, K 955, S 1035, Cu 0.76, Fe 0.79 and Zn 5.5) except for Ca (1245) and P (895), which where highest on day 7. The mean milk mineral element concentrations (mg/L) over days 55 to 150 were Ca 843, P 543, Mg 47, Na 120, K 590, S 219, Cu 0.19, Fe 0.34 and Zn 2.1. The mean plasma element concentrations (mg/L) over the same period were Ca 120, P 77.1, Mg 17.0, Na 3110, K 168, S 983, Cu 1.1, Fe 1.5 and Zn 0.49. Concentration gradients between plasma and milk were observed and, in the case of Ca, P, Mg, K and Zn, their concentrations in milk were greater than those in plasma, while a reverse situation was observed for Na, S, Cu and Fe. Conclusion With the exception of Ca and P, the highest concentrations of mineral elements were observed in the colostrum. The nursing foal should have access to good pasture or creep feed, because the intakes of Ca, P and Cu from milk may be less than optimum to meet the daily mineral element requirements.

Summary The effect of copper supplementation of pasture fed mares and foals on the copper status of the foals, in terms of plasma, soft tissue and bone copper concentrations and caeruloplasmin activity, was investigated. Twenty-one Thoroughbred foals from either control mares (n = 9), or copper-supplemented mares (n = 12) were divided randomly into control (pasture only, n = 10) or supplemented (pasture and oral copper sulphate, n = 11) groups. The pasture diet was grazed by all animals, and contained 4.4–8.6 mg Cu/kg dry matter (DM). The copper supplement for the mares contained copper sulphate equivalent to 0.5 mg Cu/kg liveweight (LW)/day. This daily dose was converted to allow administration as a thrice weekly dose (i.e. multiplied by 7/3) which was given for 13–25 weeks prior to foaling. The supplemented foals, also dosed 3 times a week, received 0.2 mg Cu/kg LW/day at age 21 days, which was increased to 0.5 mg Cu/kg LW/day at 49 days and was continued at this level until euthanasia at 150 days. Foal plasma copper concentration and caeruloplasmin activity increased from birth to 21 days post partum and then plateaued at a concentration similar to the mare, but the rise in these indices was not affected by copper supplementation of the mare or foal. Copper supplementation of the foal increased foal liver copper concentration at 150 days (P

Optimum reproductive efficiency of farmed deer is often constrained by apparent maladaptation of wild cervids to a given farm environment or components of that environment. Seasonal breeding amongst forest-fringe species of northern temperate origin (e.g. red deer, fallow deer) benefits the species within its natural range, but often creates misalignment in southern temperate zones between the high nutritional demands of lactation in summer and the earlier peak of pasture production and quality occurring in spring. This can lead to increased calf mortality, decreased calf growth rates and depressed dam liveweights. Much emphasis has been placed on manipulating either pasture production patterns or the timing of birth to create better synchrony between the two. The latter largely involves artificial manipulation of the timing of conceptions (e.g. melatonin treatment), but there may also be options for genetic selection of deer for earlier calving patterns. Tropical cervid species farmed in temperate environments can exhibit either aseasonal reproduction (e.g. chital deer) or autumn-wintering calving patterns (e.g. rusa deer), leading to high mortality of neonates (hypothermia, predation) under uncontrolled breeding management. However, there are simple management options to synchronise and shift calving patterns to better align tropical species to temperate environments. The effects of chronic and acute stress on reproductive efficiency of farmed deer are often discussed but seldom demonstrated. Many farmed deer populations exhibit high pregnancy rates (i.e. > 90% females pregnant), indicating robust reproductive physiology and general habituation to the farmed habitat. Low reproductive rates of pubertal red deer hinds in some herds may be partly indicative of the effects of chronic stress, although other factors such as social facilitation and nutrition cannot be discounted. While species of cervids that are used for farming generally display a high degree of behavioural plasticity, the farm environment and associated management practices may impinge on important components of the social environment. Thus, practices such as controlled breeding (e.g. single-sire mating) and confinement during calving may have effects on reducing overall reproductive potential by disrupting social processes (e.g. dam—calf bonds). This highlights the paucity of knowledge on the complexities of cervid behaviour and their implications in both wild and farmed deer.

A series of six studies were carried out in red deer stags to test hypotheses concerning the importance of steroid control of velvet antler growth and to investigate mechanisms by which these hormones exert their effects. Medroxyprogesterone acetate (MPA) an LH inhibitor administered to stags during hard antler caused premature antler casting, reduced subsequent antler weight and caused a reduction in the LH and testosterone responses to GnRH. In two separate studies blockade of testosterone receptors with cyproterone acetate (CPA) administered to stags, either during early velvet antler growth or during the hard antler stage, significantly reduced LH and testosterone responses to GnRH. In both studies antler length, but not weight, was increased by CPA treatment. In another study testosterone implants were used to prevent the gradual decline in plasma testosterone levels normally observed during winter. Implants were removed 3 weeks before the anticipated date of antler casting. The implants significantly increased plasma testosterone levels and subsequent antler growth (expressed as a proportional increase compared with the previous year) compared with untreated controls. To determine whether the annual cycle of plasma testosterone response following GnRH stimulation was due simply to a lack of LH stimulation, ovine LH was injected on six occasions at defined stages of the antler cycle to red deer stags and the testosterone response measured. The testosterone responses were low at antler casting and during velvet antler growth compared with antler cleaning and peak rut. It appears low testosterone levels are due, in part, to a loss of responsiveness by the testes to LH as well as a low level of secretion of LH during the antler growing season. Finally synthetic ACTH was injected at the same defined stages of antler growth as in the previous study to determine whether cortisol and adrenal androgen production altered with the stage of the antler cycle. No significant differences were found in the dehydroepiandrosterone (DHEA) response, but cortisol responses were higher from late velvet antler growth to peak rut, compared with the times of antler casting and early velvet growth. Overall it was concluded that velvet antler growth can occur without testosterone stimulation during the period of velvet growth, but the data reinforce the concept that the timing of antler growth is linked to the annual cycle of testosterone.

The application of artificial insemination technology within the red deer and fallow deer farming industries is in its infancy. However, its future potential is enormous, particularly in relation to genetic improvement programmes and international exchange of genetic material. This paper reviews the present state of such technology for these two species by discussing the major components of oestrous synchronisation, semen collection/cryopreservation and insemination techniques. Artificial oestrous synchronisation overcomes problems associated with the detection of natural oestrus. Synchronisation can be achieved through the administration of progestagens or strategic administration of prostaglandin analogues. Most studies have investigated the use of the controlled internal drug release (CIDR) device, with 12–14 day insertion plus 200–250 IU pregnant mares' serum gonadotrophin (PMSG) at device withdrawal (red deer) or 14 day insertion alone (fallow deer) being the more common treatment regimens within the natural breeding season. Administration of cloprostenol on Days 13–14 of the oestrous cycle is also highly effective in fallow deer. Future studies need to refine synchronisation regimens to increase oestrous synchrony. Semen collection, which is under seasonal constraints, is mainly by electro-ejaculation, with semen processed for cryopreservation using standard techniques. The development of artificial vagina (AV) collection methods holds promise for safer and more efficient semen collection from deer. Transcervical access to the uterine lumen has proven difficult in red and fallow deer. Presently, most fixed-time inseminations are performed per vaginam (intravaginal or intracervical) or laparoscopically (intrauterine). Conception rates to per vaginam inseminations ((20–80) × 10 6 motile spermatozoa) at approximately 48 h after CIDR device withdrawal have been highly variable and generally low (less than 40%) for both species, with a tendency towards better rates (40–60%) with double inseminations (44 and 68 h) in red deer and higher concentrations of motile spermatozoa (more than 100 × 10 6 ) for fallow deer. Conception rates to laparoscopic intrauterine inseminations ((10–40) × 10 6 motile spermatozoa) at 54–56 h (red deer) or 65–70 h (fallow deer) after CIDR device withdrawal have been more consistent and generally higher (60–70%) for both species.

There is often a poor synchrony between the high energy demands of lactation in summer and the peak of pasture production and quality occurring in spring for red deer (Cervus elaphus) and fallow deer (Dama dama) farmed under pastoral conditions in temperate climates. Considerable research within the last decade has investigated either daily administration or constant infusion of exogenous melatonin in order to advance the breeding season and hence the seasonal pattern of births of farmed deer and, therefore, align lactation and feed production. Melatonin is the hormone involved in the transduction of photoperiodic information to the endocrine system leading to precise timing of reproduction. Owing to the absence of pregnancy and lactation, the pubertal hind/doe provides the simplest model for exogenously controlling the seasonality of oestrus, ovulation and conception. All forms of exogenous melatonin delivery initiated in summer (10–12 months of age) are effective in advancing the onset of puberty. However, the degree of advancement relative to control females has been highly variable, reflecting a wide range of treatment protocols. The most significant variables appear to be the time of onset of treatment and the degree of social interaction between treated and control animals. Initiation of treatments less than 100 days after the winter solstice are likely to delay puberty by impinging upon a possible photoperiod entrainment period. Initiation of treatments more than 100 days after the solstice advances puberty, with progressively later initiation dates generally resulting in smaller degrees of advancement. Melatonin-treated red deer hinds and stags appear to influence the timing of puberty of contiguous control hinds. The maximum degree of puberty advancement so far achieved by melatonin treatment has been 54 days for red deer and 56 days for fallow deer. In adult female deer, lactation does not appear to markedly influence the degree of phase shifting by melatonin treatment. However, because melatonin treatment initiated before the end of pregnancy, 140–170 days after the winter solstice, may prevent lactogenesis, the use of melatonin is contra-indicated during pregnancy. Treatment initiation after the onset of lactation does not appear to influence milk yields, as evidenced by calf/fawn growth rates. Treatment of adult male red and fallow deer during summer advances all aspects of reproductive seasonality. Coincident treatment of males and females appears to result in coincident early rutting and oestrous activity, leading to high conception rates. Long-term consequences of treatment of red deer stags include early sexual quiescence and occasional expression of transient testicular cycles, with re-synchronisation of treated and control stags occurring 14–15 months after the initiation of treatment. However, initiation of treatment of red deer stags less than 50 days after the winter solstice delays sexual quiescence and sexual recrudescence, indicating that increasing photoperiod in early spring is important in the entrainment process. While seasonal birth/lactation patterns for red and fallow deer can be advanced by exogenous melatonin treatment, research is needed to elucidate the actual effects on overall productivity, particularly in relation to calf/fawn growth rates and the impact of precocious puberty in early-born animals.

Although it is known that growth hormone (GH) influences body composition in ruminants, the precise role of the pattern of GH secretion is not known. We have studied the pulsatile release of GH and insulin-like growth factor 1 (IGF 1) secretion in the male progeny of rams from lines selected either for {fat genotype) or against (lean genotype) fatness. Seventy-two lambs (36 each of the fat and lean genotype) were kept on high-quality pasture and randomly allocated within genotype to treatment at 2, 3, 3·5, 4,5 or 6 months of age. The procedure, which was identical for each sampling period, was to sample each lamb through a jugular cannula every 10 min for 6 h, and then, following an overnight fast, to slaughter and analyse the carcass for fat. All blood samples were analysed for GH and samples taken each hour for total plasma IGF 1. The GH data were further analysed with the pulse detection routine PULSAR. Carcass fatness, adjusted for cold carcass weight, was greater for fat genotype animals than for the lean genotype. GH was pulsatile in all profiles but the pattern differed with time and genotype. Mean GH and pulse amplitude decreased with time but did not differ between genotype, although the lean genotype had higher mean GH at five of the six sampling periods. In contrast, GH pulse frequency and IGF 1 were significantly higher for the fat compared with the lean genotype lambs. GH mean and amplitude correlated negatively with carcass fatness in both genotypes and GH pulse frequency and total IGF 1 correlated positively with fatness for the lean genotype only. When carcass weight and genotype were fitted to these relationships, GH mean and total IGF 1 were found to have independent negative and positive effects, respectively, on carcass fatness. Because GH mean had a separate effect on fatness independent of genotype or cold carcass weight, it is likely that GH secretion influences composition by the same basic mechanism in both genotypes. However, although the slopes of these relationships did not differ significantly between the genotypes, the intercepts were significantly different indicating that over and above the basic mechanism, at any level of GH, the lean genotype lambs were leaner than the fat genotype lambs. This may indicate a measure ofGH resistance in the fat genotype lambs.

Ewes hcterozygous (1+) for the Inverdale prolificacy gene (FecX’) located on the X chromosome have ovulation rates about 1.0 units higher than noncarriers. The purpose of this study was to examine the reproductive performance of ewes that were either heterozygous or homozygous (II) carriers of the Inverdale gene. Carrier rams (I) were mated with heterozygous ewes (1+) to produce females, half of which were expected to be 1+ and half II. The 59 female progeny were examined by laparoscopy at 8 mo or 1.5 yr of age; 48% were found to have nonfunctional “streak” ovaries, which were about one eighth the volume of normal ovaries and showed no sign of follicular activity. There were four examples of full sib pairs where within each pair one had normal ovaries and the other had streak ovaries. Since these streak ovaries have not been observed in ewes known to be 1+ or noncarriers (+ +), it is concluded that this condition is associated with animals homozygous for the Inverdale gene.

Blood samples were taken from six tame red deer stags at 3–15 months of age once a month from a jugular catheter every 30 min for 24 h to investigate hormonal secretion during puberty and during growth of the pedicle and first antler. All plasma samples were analysed for LH and testosterone concentrations and the resultant data were analysed using the PULSAR pulse detection routine. In addition each stag was injected with gonadotrophin-releasing hormone (GnRH; 20 ng/kg body weight) after the above samples had been taken and the bleeding regimen was continued for a further 2 h. Body weight, antler size and status (i.e. whether the stags had a pedicle or antler) were also recorded. The pulsatile secretion of LH could be considered to have occurred in three phases. The first of these was one of development, with the LH pulse frequency increasing to 8 pulses/24 h, the second a phase of regression, with a decrease in LH pulse frequency to 2 pulses/24 h, and finally a second phase of development characterized by increased LH pulse frequency to 12 pulses/24 h. Testosterone secretion generally followed the same pattern. During the period before the permanent bony pedicles grew, there were less than five LH pulses/24 h. When the pedicles were growing, LH and testosterone pulsatile secretion increased but the pulse frequency of both hormones fell during velvet antler growth. However, the overall mean testosterone level did not significantly decrease between the growth stages (2·74 and 2·29 nmol/l respectively) although mean testosterone plasma rose during pedicle growth and fell during velvet antler growth. Both hormone plasma concentrations increased dramatically, and testosterone was particularly high (11·82 nmol/l), at the time of antler cleaning. All stags responded to exogenous GnRH by secreting LH and testosterone in all sampling periods. The LH response to GnRH increased during pedicle growth and fell during antler growth before rising again in autumn as the breeding season approached. Testosterone responses largely paralleled those of LH except that they remained high in early antler development. The results are consistent with the following hypotheses. (1) Pedicle initiation is caused by increased plasma level of testosterone stimulated by increasing LH pulse frequency and (2) testosterone is stimulatory for pedicle growth but not necessarily so for velvet antler growth. Journal of Endocrinology (1991) 131, 467–474

The aim of this study was to compare the ovine growth hormone (oGH) responses of 5 genetically lean and 5 genetically fat 9 month old ram lambs (selected on the basis of their ultrasonic backfat thickness) given two 0.3 micrograms kg-1 liveweight intravenous injections of synthetic human pancreatic GH releasing factor analogue Nle27 hGHRF29 -NH2 (GRF-29) 150 minutes apart. Plasma oGH response curves were analysed using an exponential 2 compartmental model and comparisons made through parallel curve analysis. Plasma oGH levels over 200 ng ml-1 were detected in response to GRF-29. Exponential model parameters indicated that lean lambs had a significantly higher rate of oGH release into the plasma after both consecutive GRF-29 injections, and a significantly lower rate of oGH clearance from the plasma after the second GRF-29 injection only. Significantly smaller peak oGH responses to the second GRF-29 injection were shown by the fat lambs. These results suggest that oGH release is impaired in genetically fat lambs and that either the synthesis of releasable oGH is reduced or the inhibitory tone is greater in the fat lambs. The lean and fat sheep may provide a useful model for the study of hormonal control of factors affecting leanness and fatness.

The concurrent and long-term effects of feeding high (H) and low (L) levels of nutrition from weaning to 4 years of age were measured in 188 high fecundity heterozygous Booroola Merino × Coopworth (BC) ewes (FecB Fec+) and 58 low fecundity New Zealand Merino × Coopworth (MC) ewes. Following the cessation of differential feeding, all groups were grazed on a common plane of nutrition for 2 years. There were no significant nutrition by genotype interactions for liveweight, lamb performance, or ewe lambing performance. During common feeding, carryover effects of restricted feeding were apparent only for liveweight and barrenness. The mature liveweight of H ewes was 60–70 kg throughout differential feeding, which was 12–15 kg heavier than L ewes. L ewes showed 58% compensatory growth but were still 5.1 kg lighter than H ewes (P < 0.05) at the end of the experiment. Ovulation rates of L ewes were 0.07–0.51 lower than their H contemporaries during differential feeding and this was significant (P < 0.05 ...

Multiple births were induced in 20 hinds subjected to a progesterone plus gonadotropin treatment to advance the breeding season by about 4 to 5 weeks. In total, over 2 years, 92 hinds were treated and run with melatonin-treated stags. Of the 59 hinds that calved to the induced oestrus, 39 produced single calves, 19 produced twins and one produced triplets. Birth weight, gestation length, perinatal mortality and growth rate to weaning at ca. 20 weeks of age were compared for singles and twins. There was a significant effect of birth type on birth weight with twins being proportionately 0·30 lighter than singles (6·27 and 8-94 kg; P < 0·001), with a significant interaction between the birth weight of a calf and the sex of its co-twin (P < 0·05); males born as co-twins to females were proportionately 0·18 heavier than their co-twin females (P < 0·06), while in contrast twin male sets were substantially lighter than twin female sets. Gestation lengths were similar for both singles and twins, with significant negative relationships between gestation length and birth weight for both singles and twins, with a 2-day decrease in gestation length for a 1-kg increase in mean birth weight. There was a strong quadratic relationship between perinatal survival and birth weight; the expected mortality rates at 5, 8 and 11 kg birth weight derived from the relationship were 0·39, 0·11 and 0·39 respectively, indicating reduced probability of survival at both low and high birth weights. The regression relationships between weaning weight or growth rate to weaning and birth weight indicate that at the same birth weight, twin-reared calves were about 5 kg lighter than singles at 20 weeks, while an extra 1 kg weight at birth was associated with an extra 2 kg weight at 20 weeks.

The effect of the timing of melatonin treatment during spring and summer on the onset of ovarian activity, the summer moult and winter coat regrowth and live weight change was investigated in yearling red deer hinds by administering melatonin beginning on 21 October, 10 and 30 November, 20 December and 9 and 29 January. Treatment begun in November resulted in all animals displaying ovarian activity before the normal onset of the breeding season whereas October, December and January treatments resulted in only a proportion (0–3/5) of animals responding. The timing of the summer coat moult, winter coat regrowth and the phase of minimal body growth which occurred in control hinds in autumn were all advanced by up to 4 weeks by melatonin treatment. The results indicate that the time melatonin treatment is administered is important in determining the timing of puberty as well as seasonal changes in coat growth and live weight in the red deer hind.

In a series of experiments, involving 372 lambs over 2 years, the effects of subcutaneous implants of Cimaterol (CL263, 780; anthranilonitrile, 5-[1-hydroxy-2-(isoproplyamino)ethyl]-), in young sheep grazing pasture were examined. Treatment with Cimaterol increased carcass weight gain by 37% averaged over the experiments. Wool growth was reduced by 16% in the experiments where it was measured. Cimaterol treatment also increased dressing percentages by 1.3-3.7 percentage units, increased the cross-sectional area of L. dorsi muscle, and decreased fat depot weights and subcutaneous fat thickness measurements in all experiments. These changes were accompanied by increased protein and water contents and a decreased fat content in the carcass. Analysis of the growth rates of carcass components revealed that the changes were a consequence of marked increases in the rates of carcass protein deposition (up to c. 3-fold) in Cimaterol-treated lambs accompanied by markedly reduced rates of lipid deposition. ...

To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age.Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4-8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically.Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birthweight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions.Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.

Objectives To monitor the change in liver copper concentration of Thoroughbred foals from birth to 160 days of age and to determine the effects of supplementation by two injections of copper edetate given to dams in late gestation on the liver copper concentration of their foals at birth. Procedure Ten mares pregnant to the same stallion were randomised into two groups on the basis of age, liver copper concentration and expected foaling date. The treatment group mares were given 100 mg and 250 mg copper edetate intramuscularly during the ninth and tenth months of gestation respectively. Foals had liver biopsies taken weekly in the first month of life, then monthly for four months. Foals were euthanased at 160 days of age; liver samples were taken and the copper concentrations were determined. Results Two distinct patterns of age dependant decline in liver copper concentration were evident. The mean (± SD) liver copper concentration of the foals was high at birth (374 ± 130 mg/kg DM), and for seven it declined to adult values by 160 days of age (21 ± 6 mg/kg DM). In three foals the decline was at a slower rate than in the other seven and at 160 days of age the mean concentration was 162 ± 32 mg/kg DM. Repeated measures analysis showed significant differences between each biopsy (P

Pregnant Thoroughbred mares (n = 21) were grazed on tall fescue pasture containing 4.4-8.6 mg Cu/kg dry matter (DM). Twelve mares were supplemented with approximately 0.5 mg Cu/kg liveweight (LW)/day as copper sulphate for the final 13-25 weeks gestation. Plasma copper concentration declined during the third trimester for all mares and was not affected by copper supplementation. Liver copper concentration of mares and foals was determined when the foals were 4-10-days-old. Copper supplementation of the mares tended to increase mare liver copper concentration (P

The effects of natural variation in the number of copies of the growth hormone (GH) gene on growth parameters, plasma GH profiles, and the response to GHRH challenge were compared in Coopworth ram lambs from selection lines differing in body composition and GH levels. Different genotypes at the GH locus carried two, three, or four copies of the GH gene and GH secretion was studied under ad libitum feeding conditions and in the fasted state. There were no significant effects of GH genotype on any parameters of growth or body composition. Basal serum GH concentration, GH pulse frequency, and GH pulse amplitude differed significantly with selection line and fasting, but did not differ significantly between the GH genotypes. Significant differences of subtle nature were found between the GH genotypes in their responsiveness to GHRH. For the ad libitum-fed Lean selection line animals, the first GHRH challenge resulted in a higher mean maximum response for GH1/GH1 than GH2/GH2 (P0.05). Between the first and the second challenges there was a decrease in maximum response for the GH1/GH1 genotype and an increase for the GH2/GH2 genotype (P0.05 for GH genotype main effect). The differences between GH genotypes in response to GHRH challenge suggest that polymorphism in the number of GH gene copies in sheep may have physiological implications for the function of the GH axis, which may be manifested in growing lambs only under specific genotype-environment combinations.

Blood from stages aged 15 months (n = 6) was sampled at monthly intervals every 30 min for 24 h for 12 months, at 45 degrees S in New Zealand. Three extra samplings each for 24 h were carried out at about the anticipated time of antler casting. All samples were analysed for luteinizing hormone (LH) and testosterone and the resulting data further analysed by the Pulsar pulse detection routine. The animals were kept indoors under natural daylength and were fed ad libitum. All animals were weighed, antler status and size recorded and testes diameter was measured on each sampling day. Mean LH and testosterone pulsatily and plasma concentration varied seasonally. LH pulse frequency was low during autumn (2.5 pulses in 24 h), winter (1.0-1.5 pulses in 24 h) and early spring (1 pulse in 24 h) and lowest in late spring (0.2 pulse in 24 h) before rising in summer (1.0-4.0 pulses in 24 h). LH pulse amplitude and mean plasma concentration were low (< 1 ng ml-1) from March to November (autumn-spring); both rose to a peak in January (summer) of 3.4 and 1.6 ng ml-1, respectively. Testosterone pulse frequency was generally similar to LH except that slightly more pulses of testosterone than of LH were detected from March to November and more pulses of LH from November to February (summer). Testosterone pulse amplitude fell from March to November (5.3 ng ml-1 to undetectable) although there was a conspicuous peak in July (midwinter) of almost 5 ng ml-1.(ABSTRACT TRUNCATED AT 250 WORDS)

The timing of puberty in farmed red deer (Cervus elaphus) hinds can be altered by the strategic administration of melatonin, and the present study was undertaken to investigate the importance of the duration of treatment. Six groups, each of five hinds aged about 12 months were used. The control group was untreated throughout while the remaining five groups received approximately 30, 60, or 90 days of melatonin from subcutaneous implants. Treatment began in three groups in spring (on 30 November for 30,60, or 90 days), and in two groups in summer (on 30 December for 60 days and on 30 January for 30 days) so that each duration of treatment either started (30 November) or finished (approximately 1 March) at the same time. Treatment begun in spring lasting 60 or 90 days resulted in all hinds displaying ovarian activity about 20 March, representing about a 4-week advancement in the onset of puberty. Melatonin administered for 30 days in spring and 30 or 60 days in summer resulted in only a proportion (two or three of five) of hinds responding with early ovarian activity. In addition, melatonin treatment significantly advanced the seasonal patterns in live-weight gain and coat growth in some of the earlier treated groups, and reduced prolactin secretion in all treated groups. These results indicate that approximately 60 days of exogenous melatonin treatment is required to induce an alteration in the timing of puberty in red deer hinds, providing that it is given at an appropriate time of the year.

In two experiments, Red deer hinds were synchronized with intravaginal progesterone and were given 4 d of treatment (3 d before progesterone withdrawal and 1 d after) with an ovine follicle stimulating hormone (FSH) preparation which had a claimed low level of luteinizing hormone (LH) contamination. In Experiment 1, 12 hinds received one of four FSH levels by osmotic minipump. Hinds were run with fertile stags, and laparotomy and embryo recovery were performed 9 d after progesterone withdrawal. The ovulation rates (mean of three hinds per dosage) were 1.0, 2.0, 4.3 and 15.3 (number of corpora lutea counted) for estimated daily dosages rates of 0.036, 0.071, 0.11 and 0.14 units FSH preparation/day; the response to the increasing dosage was exponential (P 24 63 ), with all recovered ova being fertilized and of transferable quality. In Experiment 2, performed later in the breeding season, eight hinds received 0.14 units FSH/day either by minipump or by intramuscular injection. The mean ovulation rates were 3.0 and 11.0 (a significant difference, P 34 47 ), and with only 18 34 ova considered to be of transferable quality. The recovery rate in Experiment 2 was significantly higher than that in Experiment 1 (P

Plasma samples taken every 30 min over a 26-h period each month from six 4- to 15-month-old red deer stags were analysed for GH. In addition, two samples taken at 10.00 and 22.00 h were analysed for insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II). A concentrate diet was available ad libitum. Food intake, body weight and antler status were recorded. Concentrations of GH were analysed using the PULSAR peak detection routine. Secretion of GH was pulsatile in every month of sampling, but the pattern of pulsatility differed seasonally. During the autumn and early winter (April–June in the Southern hemisphere) GH pulses were frequent and of low amplitude. In contrast, GH pulses in spring (August–September) were of high amplitude and high frequency resulting in a high mean level of GH circulating in the plasma. In early summer (November) the GH pulse amplitude was much lower and pulse frequency fell. There was a rise in GH pulse frequency not accompanied by an increase in GH pulse amplitude in summer (December–January). GH pulse amplitude seemed to be the main determinant of mean GH plasma level. Secretion of IGF-I was raised 1 month after peak monthly mean GH secretion. There was little consistent relationship between concentrations of IGF-II and mean daily GH. Concentrations of GH correlated positively and significantly with liveweight gain and antler growth rate with a delay of 1 month. Significantly positive correlations between concentrations of IGF-I, liveweight gain and antler growth rate were observed. It is considered that the spring and summer (September–December) seasonal acceleration of liveweight gain and antler development in stags could be a consequence of high winter/early spring (August–September) GH pulse frequency and amplitude resulting in increased concentrations of IGF-I, particularly in October. Journal of Endocrinology (1989) 121, 351–360

We have previously shown that plasma IGF 1 concentration is positively correlated with the rate of antler growth and have proposed that IGF 1 is stimulatory for antler growth in the red deer stag. Therefore to partly resolve the question of whether the IGF 1 was of circulating or local origin in relation to its effect on antler growth, we surgically prevented stags from growing antlers. We recorded significantly elevated plasma levels of IGF 1 in the non-antlered stags compared with normal antlered stags during the antler growth periods. This result is consistent with a hypothesis that the antler is a target organ for IGF 1 and that prevention of antler growth removed a population of IGF 1 receptors. IGF 1 is already known to stimulate body growth but this work points strongly to the possibility that plasma IGF 1 may stimulate individual organ growth in an endocrine manner.

Six red deer stags from age 4 months were kept in a light-proof room under an artificial photoperiod consisting of 5.5 cycles of alternate 2-month periods of 16 h light and 8 h dark (16L:8D) and 8L:16D. At 2 or 3 weekly intervals from 10 months of age through 4 cycles, the stags were anaesthetized with xylazine and challenged i.v. with 10 micrograms GnRH. Blood samples were withdrawn immediately before and 10 and 60 min after injection. LH and testosterone concentrations were measured in all samples by RIA. Antler status was recorded daily. Peak LH values on each sampling day occurred in the sample taken 10 min after GnRH stimulation while peak testosterone occurred in the sample taken at 60 min. There were 4 cycles of LH and testosterone secretion accompanied by 4 antler cycles in the stags. The highest LH responses were detected during short days (8L:16D), and the highest testosterone responses were detected around the time of the change from short to long days. The responses of both hormones were lowest at the end of periods of long days or the beginning of short days. The increased pituitary LH response to GnRH was evident 4 weeks after the change to short days which are stimulatory for gonadal development. Antler casting occurred at the end of long days and cleaning at the end of short days. It is considered that antler cycles were due to the ability of the stags to vary release of LH and testosterone in response to changes in the artificial photoperiod.

We have investigated the possibility that IGF-1 may play a role in the regulation of antler development. Plasma IGF-1 concentrations were measured throughout the first period of development of the pedicle and first antler of red deer (Cervus elaphus) to determine whether a relationship existed between growth of antler cartilage (velvet antler) and IGF-1. We report that plasma levels of IGF-1 are significantly elevated during the velvet antler growing phase relative to the other phases of pedicle and first antler development and a strong positive correlation exists between antler growth rate and circulating concentrations of IGF-1. As IGF-1 has been demonstrated to influence cartilage growth, we suggest that IGF-1 is a candidate as an antler stimulating hormone.

Eight adult red deer stags were given an i.v. injection of synthetic gonadotrophin-releasing hormone (GnRH) on seven occasions at various stages of the antler cycle, namely hard antler in late winter, casting, mid-velvet growth, full velvet growth, antler cleaning and hard antler both during the rut and in mid-winter. The stags were allocated at random on each occasion to one of four doses, i.e. 1, 3, 10 or 95 μg GnRH. Blood samples were taken before GnRH injection and for up to 2 h after injection. Pituitary and testicular responses were recorded in terms of plasma LH and testosterone concentrations. There was an increase in plasma concentration of LH after the GnRH injection in all stags at all stages of the antler cycle. Dose-dependent responses of LH to GnRH in terms of area under the curve were apparent at all stages of the antler cycle. The lowest responses were recorded at casting, during velvet antler growth and at the rut sampling. The pattern of testosterone response reflected the inter-relationship of the antler and sexual cycles with very low testosterone responses occurring at casting and during velvet antler growth. The responses were higher at antler cleaning and then increased to a maximum at the rut before declining to reach their nadir at casting. The results are consistent with a hypothesis that the antler cycle, as a male secondary sexual characteristic, is closely linked to the sexual cycle and its timing is controlled by reproductive hormones. Low plasma concentrations of testosterone, even after LH stimulation, are consistent with the hypothesis that testosterone is unnecessary as an antler growth stimulant during growth. J. Endocr. (1988) 117, 35–41