A new gene mapping resource: interspecies hybrids between Père David's deer (Elaphurus davidianus) and red deer (Cervus elaphus).

Three male F1 hybrids between Père David's deer and red deer were mated to red deer to produce 143 backcross calves. The pedigrees are a rare example of a fertile hybrid between evolutionarily divergent species. We examined the use of these families for genetic mapping of evolutionarily conserved (Type I) loci by testing for genetic linkage between five species-specific protein variants and 12 conserved DNA probes. Two probes were homologous, and the remainder syntenic, to the protein coding loci in cattle or humans. Using six restriction enzymes, each DNA probe detected one or more restriction fragments specific to Père David's deer. Linkage analyses among the species-specific variants placed the loci into four linkage groups within which linkage between adjacent loci and gene order was supported by a LOD > 3. The linkage groups were (HPX, HBB)-FSHB-ACP2, LDHA-CD5-IGF2, BMP3-(GC, ALB)-(KIT, PDGFRA) and LDLR-C3-FGF1. Southern and protein analysis of LDHA and ALB provided identical segregation data. These linkage groups were consistent with the cattle gene map and provide new information for comparing the gene maps of ruminants, humans and mice. The deer hybrids are an important new resource that can contribute to the comparative analysis of the mammalian genome.

The pituitary and testicular responses to GnRH challenge between 4 and 14 months of age in thoroughbred colts born in spring and autumn.

Gonadotropin releasing-hormone analogue (buserelin) challenges were carried out every 8 weeks from 4 to 14 months of age on thoroughbred colts born in the spring (n = 6) or autumn (n = 5) to define the onset of puberty. In all colts, luteinizing hormone (LH) secretion followed a seasonal pattern, with high baseline and maximal concentrations in the spring and summer and low concentrations in the winter. Testosterone concentrations were undetectable before spring and, thus, autumn-born colts were younger than spring-born colts when a testosterone response to buserelin was first observed. Mean weights of the autumn-born colts were 300 kg (282-327 kg) at the time of the first detectable testosterone response in the following spring (October). Spring-born colts had reached this weight in the winter (May and June, before day length had increased) but did not exhibit a significant testosterone response until the spring at a mean weight of 352 kg (327-403 kg). It is proposed that colts must achieve a threshold body weight concurrently with stimulatory photoperiod for onset of puberty to occur.

Elevated plasma IGF 1 levels in stags prevented from growing antlers.

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.

Insulin-like growth factor 1 (IGF-1) antler-stimulating hormone?

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.

Temporal changes in LH and testosterone and their relationship with the first antler in red deer (Cervus elaphus) stags from 3 to 15 months of age.

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 wih 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma LH and testosterone responses to gonadotrophin-releasing hormone in adult red deer (Cervus elaphus) stags during the annual antler cycle.

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 micrograms 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.

Pulsatile growth hormone, insulin-like growth factors and antler development in red deer (Cervus elaphus scoticus) stags.

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.

Genetically lean and fat sheep differ in their growth hormone response to growth hormone-releasing factor.

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 physiological effects of natural variation in growth hormone gene copy number in ram lambs.

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 (P < 0.05). 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 (P < 0.05 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.

LH and testosterone responses to five doses of a GnRH analogue (buserelin acetate) in 12-month-old Thoroughbred colts.

To determine the responsiveness of the pituitary-gonadal axis of peri-pubertal colts to GnRH, buserelin (0.5, 1, 5, 10 and 40 microg) was given to 13 male Thoroughbred yearlings ( n=3-8 colts per dose). Jugular venous blood samples were taken at -10, 0, 10, 20, 30, 40, 60, 120 and 180 min relative to buserelin administration. Increases (P < 0.05) in LH concentrations occurred in colts that received 5, 10, or 40 microg buserelin, but not in those that received 0.5 or 1 microg. Peak LH concentrations and mean area under the curve were higher (P < 0.05) in colts receiving 40 microg buserelin than in those that received 0.5 or 1 microg. Increases ( P< 0.05) in testosterone concentrations occurred in some, but not all, colts that received 1, 5, 10, or 40 microg buserelin. Neither peak concentration nor area under the curve of testosterone differed significantly among doses of buserelin. The percentage of horses that responded to the buserelin increased with increasing dose, with only the highest dose eliciting LH and testosterone responses in all colts. In conclusion, peri-pubertal colts exhibited a dose-response release of LH following buserelin treatment, but individual colts responded in an "all or nothing" manner, such that each either had an LH response or did not. Some colts that exhibited a significant LH response had no subsequent increase in plasma testosterone concentrations; perhaps the pituitary LH response may not have been great enough to stimulate the Leydig cells in these individuals.

Superovulation and embryo recovery in Red deer (Cervus elaphus ) hinds.

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<0.01). The recovery rate of ova on flushing was 38% (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<0.01), respectively, with a recovery rate of 72% (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<0.001). Overall, the results were better than those previously recorded for red deer, perhaps a function of both the FSH preparation used and an improved progesterone profile in estrus synchronization.

Onset of puberty in pasture-raised Thoroughbreds born in southern hemisphere spring and autumn.

REASONS FOR PERFORMING STUDY: There is little information on age, weight and time of year of puberty in Thoroughbred horses, and the interpretation of such data is difficult due to the wide variety of descriptions of the onset of puberty. OBJECTIVES: To examine the age, bodyweight and date of onset of puberty in Thoroughbreds born in spring and autumn. METHODS: Bodyweight data and blood samples were collected in 59 pasture-raised Thoroughbred horses. Five autumn-born and 18 spring-born colts and 3 autumn-born and 33 spring-born fillies were examined from birth to age 13 and 17 months. A testosterone concentration >2 s.d. above the baseline concentration was indicative of onset of puberty in colts; and progesterone concentration >2 ng/ml and at least 3 times greater than the previous progesterone concentration was indicative of a first ovulation in fillies. RESULTS: Spring-born fillies and colts were older and heavier than autumn-born fillies and colts at puberty. The age at onset of puberty in spring- and autumn-born foals was 291-408 days and 212-270 days, respectively. The weight at puberty in spring-born foals was 302-409 kg, and in autumn-born foals was 277-344 kg. However, the mean date at onset of puberty was not significantly different between spring- and autumn-born horses, with puberty occurring in October (New Zealand spring). CONCLUSIONS AND POTENTIAL RELEVANCE: Seasonal changes in photoperiod affect the timing of onset of puberty, provided a minimum threshold bodyweight has been reached. Spring-born horses reached this threshold weight during the winter months and remained reproductively inactive until after the stimulus of increasing day-length occurred. The autumn-born horses reached the threshold weight to support puberty at the same time as stimulatory photoperiod and, therefore, reached puberty significantly younger and lighter than the spring-born horses.

Effect of copper supplementation on copper status of pregnant mares and foals.

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<0.08) and increased foal liver copper concentration (P<0.01). There was a significant relationship between mare and foal liver copper concentration (P<0.001, r2 = 0.7). Increasing the copper intake of mares is effective in enhancing the copper status of foals.

Effect of copper supplementation on the evidence of developmental orthopaedic disease in pasture-fed New Zealand Thoroughbreds.

The effect of copper status on the evidence of bone and cartilage lesions was investigated in 21 Thoroughbred foals. The foals and their dams were grazed on pasture containing 4.4-8.6 mg Cu/kg dry matter (DM). Four treatment groups were created by randomly allocating mares and their foals to either copper supplemented (0.5 mg Cu/kg liveweight (LW)/day), or control (pasture only) groups. This experimental design allowed the effect of copper supplementation of mare and foal to be examined independently. Parameters of bone and cartilage development were assessed in the foals both in vivo, and at post mortem at approximately age 150 days. Mare copper supplementation significantly (P<0.01) decreased radiographic indices of physitis in the distal third metatarsal bone of the foals at 150 days, and the prevalence of articular cartilage lesions (P<0.05). Articular cartilage lesions were minor in all foals, with no evidence of clinical developmental orthopaedic disease (DOD) in vivo, with the exception of minor radiographic changes assessed at post mortem. Copper supplementation of the foal had no effect on any of the bone and cartilage parameters. Copper supplementation of the mares did not abolish DOD in the growing foals, emphasising the probable multifactorial nature of this condition. However, mare supplementation may be a useful treatment regime on a farm where the incidence and severity of DOD are of concern.

Effect of copper supplementation on the copper status of pasture-fed young Thoroughbreds.

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<0.03). Copper intake of diets containing approximately 8-28 mg Cu/kg DM is well reflected by liver copper concentration, but is poorly reflected by bone, other soft tissue copper concentrations and circulating copper status indices.

Liver biopsy techniques for adult horses and neonatal foals to assess copper status.

OBJECTIVE: To evaluate standing, percutaneous, ultrasound-guided, transthoracic liver biopsy in mares, and transabdominal laparoscopically-guided, liver biopsy under general anaesthesia in foals, as techniques for obtaining tissue for assessment of copper status. The techniques were evaluated with respect to ease of use and effect on the animal. PROCEDURE: Twenty of 24 Thoroughbred mares and 21 of their foals were biopsied. The animals were part of a larger study of the effect of copper supplementation on copper status and the prevalence of developmental orthopaedic disease. Livers were also collected from unrelated horses and sampled to investigate the variability in the distribution of copper in liver tissue. RESULT: The biopsy technique caused no lasting effect on the mares, but there was an increased risk of viscus penetration associated with taking multiple biopsy cores. The use of ultrasonography to scan the target area for the liver identified four cases that were not appropriate candidates for liver biopsy, because of large intestine being located in the biopsy area. In the foals there were no serious postoperative adverse effects, nor was there any evidence of problems caused by the procedure when the abdomen was examined post-mortem at 5 months of age. In livers collected to investigate the variability of copper concentration, copper appeared to be relatively evenly distributed through the liver. CONCLUSION: Standing, percutaneous, ultrasound-guided, transthoracic liver biopsy in mares, and transabdominal, laparoscopically-guided, liver biopsy under general anaesthesia in foals are convenient procedures for obtaining liver tissue for assessing copper status in horses. The use of ultrasound to identify liver tissue is recommended, especially in older mares.

Changes in liver copper concentration of thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams.

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 dependent 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 < 0.01) and between 'normal' and 'accumulator' foals (P < 0.002). Copper injections given to mares in late pregnancy had no effect on the liver copper concentration of foals at birth. CONCLUSIONS: The significance of the two patterns of age dependant decline in liver copper concentration is unknown. Parenteral copper supplementation of the dam in late gestation had no effect on the liver copper concentration of the foal at birth.

Content and distribution of macro- and micro-elements in the body of pasture-fed young horses.

OBJECTIVE: To determine the content and distribution of Na, K, Ca, P, Mg, S, Cu, Mn, Fe and Zn in the body of pasture-fed young horses and then use a factorial model to calculate the dietary mineral requirements for growth. PROCEDURE: Twenty-one foals were killed at about 150 days of age and the organs, soft tissues, skin and bones and a sample of muscle were dissected out and weighted. The mineral concentrations of elements in all soft tissues and bones were measured by inductively coupled emission spectrometry. The total mineral element composition associated with a tissue was determined from the weight of tissue and its mineral element concentration. RESULTS: Expressed as a percent of total body mineral elements, muscle contained 20% Na, 78% K, 32% Mg, 62% Cu, 36% Mn and 57% Zn, bone contained 47% Na, 99% Ca, 81% P, 62% Mg, 30% Mn and 28% Zn while the organs accounted for a smaller percentage ranging from 0.06% for Ca to 26% for Fe. In liver Cu accounted for 9.2% of total body Cu. Each kilogram of empty body weight was associated with 1.0 g Na, 2.5 g K, 17.1 g Ca, 10.1 g P, 0.4 g Mg, 1.1 mg Cu, 0.39 mg Mn, 52.5 mg Fe and 21.4 mg Zn. CONCLUSION: The mineral element content of body weight gain is a component used in the factorial model to determine dietary mineral element requirements for growth. The calculated dietary mineral requirements, expressed per kg dry matter, for a 200 kg horse gaining 1.0 kg/day were 1.0 g Na, 2.1 g K, 4.6 g Ca, 3.5 g P, 0.7 g Mg, 4.5 mg Cu and 25 mg Zn.

Concentrations of macro- and micro-elements in the milk of pasture-fed thoroughbred mares.

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.

A preference-based approach to deriving breeding objectives: applied to sheep breeding.

Using internet-based software known as 1000Minds, choice-experiment surveys were administered to experts and farmers from the Irish sheep industry to capture their preferences with respect to the relative importance - represented by part-worth utilities - of target traits in the definition of a breeding objective for sheep in Ireland. Sheep production in Ireland can be broadly separated into lowland and hill farming systems; therefore, each expert was asked to answer the survey first as if he or she were a lowland farmer and second as a hill farmer. In addition to the experts, a group of lowland and a group of hill farmers were surveyed to assess whether, and to what extent, the groups' preferences differ from the experts' preferences. The part-worth utilities obtained from the surveys were converted into relative economic value terms per unit change in each trait. These measures - referred to as 'preference economic values' (pEVs) - were compared with economic values for the traits obtained from bio-economic models. The traits 'value per lamb at the meat processor' and 'lamb survival to slaughter' were revealed as being the two most important traits for the surveyed experts responding as lowland and hill farmers, respectively. In contrast, 'number of foot baths per year for ewes' and 'number of anthelmintic treatments per year for ewes' were the two least important traits. With the exception of 'carcase fat class' (P < 0.05), there were no statistically significant differences in the mean pEVs obtained from the surveyed experts under both the lowland and hill farming scenarios. Compared with the economic values obtained from bio-economic models, the pEVs for 'lambing difficulty' when the experts responded as lowland farmers were higher (P < 0.001); and they were lower (P < 0.001) for 'carcase conformation class', 'carcase fat class' (less negative) and 'ewe mature weight' (less negative) under both scenarios. Compared with surveyed experts, pEVs from lowland farmers differed significantly for 'lambing difficulty', 'lamb survival to slaughter', 'average days to slaughter of lambs', 'number of foot baths per year for ewes', 'number of anthelmintic treatments per year for ewes' and 'ewe mature weight'. Compared with surveyed experts, pEVs from hill farmers differed significantly for 'lambing difficulty', 'average days to slaughter of lambs' and 'number of foot baths per year for ewes'. This study indicates that preference-based tools have the potential to contribute to the definition of breeding objectives where production and price data are not available.