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    Effect of slope class on defoliation frequency and severity of Trifolium repens by sheep in hill pastures : a thesis presented in partial fulfilment of the requirements for the degree of Master in Applied Science at Massey University
    (Massey University, 1996) Liu, Cunqi
    Hill pastures demonstrate varying intensities of grazing related to slope. A study of this effect was carried out at the Ballantrae Hill Country Research Station on set-stocked pastures that were maintained on high (H) and low (L) soil fertilizer/stocking rate treatments. In the first experiment, 10 marked white clover stolons were observed at 1-week intervals for grazing damage in each (200 * 300 mm) of 10 paired quadrats on both flat terrain (FT) between 0-20° and steeply sloping terrain (ST) between 30-45° in each of two treatments (H & L) in winter of 1995. The defoliation frequency (0.38 vs 0.29 ± 0.10; P<0.05) and severity (0.45 vs 0.30 ± 0.11; P<0.05) were significantly higher on the FT than on ST, but this phenomenon only occurred on the H treatment. In order to determine the reason for causing sheep grazing discrimination between terrain, 10 sites that contained the FT and ST were selected on the L treatment. At each site, four paired turves (200 * 300 mm) were cut, two turves were from the FT and the other two from the ST, were transplanted into similar or contrary terrain to give all combinations of turf and terrain in spring of 1995 and again in autumn of 1996. In autumn, turf from the FT was grazed more frequently (0.38, 0.36 vs 0.15, 0.11 ± 0.18; P<0.001) and severely (0.81, 0.87 vs 0.28, 0.19 ± 0.41; P<0.001) irrespective of its location in the sward, but this effect was stronger within the first three weeks of the grazing period. In contrast, this phenomenon did not occur in spring, and when FT turf was transplanted into the FT it was less (0.09 vs 0.32, 0.31, 0.37 ± 0.23; P<0.05) severely defoliated than the other treatments. It is concluded that sheep generally defoliated white clover on the FT more frequently and severely than on the ST and the main reason for this discriminatory grazing was the difference in the vegetation conditions (e.g., botanical composition) of pastures. This preference for the FT was stronger during autumn, on the H treatment, and in the early stage of a grazing period. These findings suggest it may be possible to lessen discriminatory grazing in hill pastures by improving pasture botanical composition, adjusting fertilizer application rate or by seasonal manipulating of grazing polices.
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    Zearalenone in pasture and its effects on reproduction in ewes : a thesis presented in partial fulfilment for the degree of Master of Applied Science in Animal Science at Massey University
    (Massey University, 1997) Kramer, Richard
    Zearalenone is an oestrogenic mycotoxin which has the potential to cause reproductive disorders in sheep. Zearalenone-producing Fusarium species are present in New Zealand pasture and it is likely that the amount of zearalenone present during the mating period may be sufficient to cause reproductive dysfunction in the grazing sheep. This study consisted of three trials which aimed to measure zearalenone levels in the pasture and sheep, and determine the subsequent effects on reproductive performance. The first trial investigated the levels of zearalenone during April in various components of the ryegrass plant at various pasture sites, which included urine-patch, dung-patch and inter-excreta sites. Zearalenone taken up by the ryegrass plant was also determined. The second trial comprised of 6 groups of ewes (n=10), and compared levels of zearalenone and related metabolites in the blood and urine of ewes grazed on pasture or chicory and either orally (5 mg/ewe)or intravenously dosed (2 or 0.5 mg/ewe) daily with zearalenone. The subsequent effects on ovulation rate, conception rate, and number of lambs carried was also determined. The third trial comprised of 4 groups (n=110) of ewes, of which two groups were grazed on grass-dominant pasture and the remaining 2 groups were grazed on chicory for two weeks prior to mating at which time one of the groups on each grazing treatment was interchanged and the ram introduced. The levels of free and conjugated zearalenone in the blood and urine were determined and the subsequent effects on ovulation rate, conception rate and the number of lambs carried were measured. In the first trial it was shown that zearalenone concentration within sites was highly variable at that time of the year, however, urine-patch and dung patch sites yielded significantly higher quantities of zearalenone. Zearalenone appeared to be readily taken up by the ryegrass plant through the roots and translocated into the young growing tissue of the plant. The distribution of zearalenone in the pasture and the plant are discussed with regards to zearalenone intake by the animal. The zearalenone dosing trial showed that significant levels of zearalenone, α-and α-zearalenol, zeranol and taleranol were present in the blood and urine of dosed ewes and that levels of all compounds analysed were higher in ewes grazed on pasture. Ewes grazing pasture had a significantly lower (P<0.05) ovulation rate than ewes grazed on chicory. The third trial showed that chicory was effective in reducing the levels of free zearalenone present in the ewe around the time of mating with levels in ewes grazed on chicory being significantly lower (P<0.05) in both the urine and blood, than in ewes grazed on grass pasture. There were no significant differences in reproductive performance. Zearalenone levels in the pasture were generally lower in 1995 than in previous years and might have reduced possible differences in reproductive performance between ewes on the different feed types. The implications of higher zearalenone concentrations in the pasture are discussed with regards to reproductive performance and the use of chicory as a feed prior to mating. Further research is required to identify and clarify links with zearalenone and metabolites produced in pasture and reproductive dysfunction in ewes.
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    The effects of leaf shear breaking load on the feeding value of perennial ryegrass for sheep : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1992) Inoue, Tatsushi
    Reducing physical resistance has been thought to be a key factor to increase efficiency of masticatory breakdown of forage, which may lead to faster rumen fractional outflow rates (FOR) and consequently to increased voluntary feed intake and hence improved feeding value (FV). Two selections of perennial ryegrass (PRG) were selected for low (LS) and high leaf shear breaking load (HS) based on the maximum load required to shear across the leaf, i.e. leaf shear breaking load (LSBL). The series of experiments were conducted to investigate the effects of LSBL on the FV of PRG for sheep. LSBL, morphological and anatomical parameters were measured on the LS and HS PRG selections grown under the optimum climatic conditions. LSBL for the LS PRG selection was approximately 41 % lower the HS PRG selection. However, the LS selection had shorter leaf lengths, narrower leaf widths and narrower leaf cross-sectional area (CSA) than the HS selection. Therefore, in leaf shear strength (LSS), the LS selection was estimated to be approximately 27 % less resistant to shear than the HS selection per unit of CSA. The lower LSS in the LS selection is due to the lower concentration of sclerenchyma tissues in leaf CSA compared with the HS selection. However, the differences in the total shear load required to breakdown a unit dry weight of leaves to 1 x 1 mm·particle size, namely, leaf index of masticatory load (IML) between the selections were influenced by the differences in m orphological characteristics of leaves between the two PRG selections. Comparisons were made between the LS and HS PRG selections in the efficiency of mastication by sheep on particle breakdown. There were no major effects of reduced LSBL in PRG on the efficiency of mastication during eating and during rumination. Although the LS PRG selection was approximately 29 % lower in LSBL than the HS PRG selection, the difference for the two PRG selections in IML was almost nil. Effects of LSBL in PRG on rumen fractional outflow rate (FOR) and apparent digestibilities were investigated in sheep fed at restricted feed intake levels. There were no effects of reduced LSBL on FOR, although the LS PRG selection was approximately 39 and 12 % lower than the HS PRG selection in LSBL and IML, respectively. The digestibility of the cellulose fractions was approximately 16 % lower in the LS PRG selection than the HS PRG selection. The leaf morphology in PRO may affect the efficiency of fibre digestibility. Two field trials were conducted to test the hypothesis that LSBL in PRG improves FOR and leads to higher voluntary feed intake, and hence achieves improved live weight gain and wool production, namely FV. Although the LS PRG selection had 25-30 % lower LSBL than the HS PRG selection, live weight gain and wool production of sheep were not improved by reduced LSBL. FOR in sheep showed no indications of difference and voluntary feed intake was similar between the animals grazing the LS and HS PRO selections. The lack of difference in IML between the LS and HS PRG selection can be considered as a main reason for this. The hypothesis, that reduced LSBL in PRG would improve its FV, was therefore rejected. In conclusion, there were no major effects of reduced LSBL in PRG on efficiency of masticatory particle breakdown, and consequently, FOR, feed intake and hence FV in sheep. This is due to the lack of selection effect of PRG in IML. IML is a determining fac tor for the efficiency of mastication both during eating and rumination. The selection of PRG for a lower IML will, therefore, be necessary in I order to increase efficiency of masticatory particle breakdown, FOR and hence FV of PRG.
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    Studies on the effect of some nitrogenous materials on the food intake of sheep : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1968) Bryant, Arnold Max
    The problem of how mammals regulate their food intake is in itself, of sufficient scientific interest to justify its intensive study. To those concerned with human biology, additional impetus is provided by the prevalence in affluent societies of disorders of health associated with the excessive intake of food. To those concerned with animal production, there is the realisation that optimum food intake is the major determinant of efficient production. In practice, the nutritive value of many of the foodstuffs the ruminant is called on to convert to useable products is limited by the amount eaten.
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    A study of morphological and physiological changes in the mandibular gland of the sheep associated with eating and direct stimulation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1981) Ariyakulkaln, Punnipa
    This study was undertaken to investigate relationships between the structure of the mandibular gland of the sheep and its secretory activity in response to feeding, direct stimulation of autonomic nerves, or pharmacological agents that mimic the action of autonomic transmitters. Forty-five crossbred Romney ewes and wethers were used in acute experiments and twenty-two in chronic experiments. Histochemical and electron microscopical examinations of the structure of mandibular glands confirmed that their secretory endpieces are composed of mucous tubulo-acinar cells and seromucous demilunes. The mucous acini contained a single type of electron lucent granules, whereas the granules of demilunes typically exhibited a tripartite structure. The intercalated ducts were relatively short and lined by non-secretory, simple cuboidal cells and occasional basal cells. Striated ducts were numerous and lined by four cell types, the most common of which (type-I) were tall, columnar, electron lucent cells with well developed membrane infoldings basally with associated mitochondria and small, dense, apical bodies. Myoepithelial cells were distributed densely around the secretory endpieces and within the basement membranes. Myoepithelial cells were also found embracing the intercalated duct cells. Both AChE-positive and biogenic-amine fluorescent nerve fibres were present around the secretory endpieces and the walls of blood vessels. Fewer biogenic-amine fluorescent fibres were seen in relation to duct cells. Electron microscopy showed unmyelinated fibres in both epilemmal and hypolemmal sites. The epilemmal axons were frequently found close to a variety of effector cells, while hypolemmal axons were observed occasionally in the intercellular space between adjacent striated duct cells and between intercalated duct and mucous cells. Axons containing large granular vesicles were also found within interstitial nerve bundles. Mandibular secretion was studied after cannulation of the mandibular duct in both acute and chronic experiments. In anaesthetized animals, stimulation of either the chorda lingual nerve (3-8V, 5-10Hz, 0.2 msec) or injection of carbachol (40 µg kg-1 body weight, iv) within 10-25 sec caused a copious secretion (0.33-0.74 g min-1) of low protein content (0.44-1.56 mg ml-1). This response was completely blocked by atropine (0.1 mg kg-1 body weight). In contrast, stimulation of cervical sympathetic trunk (3-8V, 5-10 Hz, 0.2 msec) after a latency of 35-102 sec caused a meagre secretion (0.01-0.06 g min-1) of high protein concentration (4.02-25.68 mg ml-1). Isoprenaline had similar effects. Secretory responses to sympathetic stimulation were blocked by propranolol (1.0 mg kg-1 body weight). Studies involving gel electrophoresis demonstrated major protein bands exclusively in the sympathetic nerve or isoprenaline stimulated saliva. These major protein components (both soluble and insoluble) were found by immunocytochemical studies to be localized in the demilunes and some striated duct cells of the resting gland. It was found that in sheep fed lucerne chaff (ca. 1,000 g daily) a rapid and sustained mandibular flow only occurred during eating, although, short term increases were seen, for example, during drinking. Flow was absent during rumination and slight (0.95 ± 0.09 g h-1) or absent at rest. Saliva produced during eating had its highest protein concentration almost immediately as eating commenced (1.65 ± 0.06 mg ml-1) and remained at a high level during the first hour of eating (1.55 ± 0.06 mg ml-1) Propranolol (1.0 mg kg-1 body weight, iv) caused significant reductions in protein secretion during eating (P<.001) without associated changes in flow. Gel electrophoretic studies confirmed the presence of a major protein band similar to soluble protein band X found in sympathetically evoked saliva. The intensity of this major protein band in saliva collected during eating was also reduced after propranolol treatment. Saliva collected during teasing had a high protein concentration (2.73 ± 0.20 mg ml-1). It is concluded that sympathetic activation was involved mainly early in the eating period and that parasympathetic nerves were active throughout. The latter was confirmed by a great reduction in flow after injection of atropine (0.1 mg kg-1, iv). Morphological studies of the glands of sheep whose food had been withheld for 20 hours revealed that both the mucous acini and seromucous demilunes were filled with secretory granules. Stimulation of the chorda lingual nerve for 2-4 hours caused acini to discharge their contents of secretory granules, but no appreciable changes in the demilunes. On the other hand, stimulation of the cervical sympathetic trunk produced varying degrees of degranulation in the demilunes, with, in some cells, vacuolation. Infusion of isoprenaline (2h; 0.3 µg kg-1 min-1) produced similar changes in demilunes. Striated duct cells showed reduced PAS-staining, and disruption of their basal regions, particularly after stimulation of sympathetic nerves. Concurrent stimulation of both sympathetic and parasympathetic nerves resulted in a combination of the above separate effects. Eating led to extensive degranulation and greater evidence of synthesis in the mucous acini than parasympathetic nerve stimulation, the changes increasing with the duration of eating, and a depletion of secretory granules in demilunes that could be prevented by propranolol. (1.2 mg kg-1 body weight, iv ). The morphological changes in demilunes were not proportional to the duration of eating but were greatest in its early phases. Evidence of small dense bodies which were apparently discharged via the apical membrane of striated duct cells and a loss of PAS-staining in these cells suggest that they secrete during eating. However, neither damage to striated duct cells nor secretory endpieces was evident. The results suggest that the sheep mandibular gland is naturally stimulated by both divisions of the autonomic nervous system, with acinar cells predominantly under the parasympathetic and demilunes under the sympathetic control. The sympathetic stimulation of salivary protein secretion appears to be mainly mediated via a β-adrenergic mechanism whereas the secretion of fluid and probably also mucus glycoproteins is an atropine-sensitive parasympathetic effect. On both morphological and physiological grounds it is suggested that in sheep mandibular glands, myoepithelial cell contraction is important in assisting the secretion of viscous saliva. Further studies on the following areas would seem appropriate: (i) systematic morphological studies using stereological analysis of changes in the acinar cells, demilunes, striated ducts and their cytoplasmic components; (ii) ultrastructural examinations of the innervation pattern in this gland under normal conditions, after specific denervation and reinnervation; (iii) studies of the nature and origin of the salivary proteins secreted during eating and nerve stimulation and (iv) the use of chronically cannulated animals for studies of the influence of different conditions of feeding.
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    Application of intraruminal chromium controlled release capsules to the measurement of herbage intake of sheep at pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1990) Parker, Warren James
    Experimental evidence obtained since 1950 suggests that New Zealand sheep farm production and financial returns could be increased by adopting separate grazing management for ewes of different pregnancy and rearing status from 6 weeks before lambing until weaning. Progress in developing management systems for the differential allocation of pasture, favourable lambing paddocks and labour during this period has been restricted by the absence of equipment for diagnosing ewe pregnancy status and a lack of data relating pasture conditions to feed intake and ewe and lamb productivity. Accurate pregnancy diagnosis by realtime ultrasound scanning has been available to farmers since 1985, but research into ewe grazing management continues to be hampered by the absence of techniques for measuring feed intake. This thesis addressed the latter issue, first by validating controlled release capsule (CRC) technology for measuring feed intake and second by examining feed intakes of ewes differing in pregnancy and rearing status and relating intakes to productivity. A series of 11 experiments were conducted with sheep CRC to validate this technology for measurement of intake and to develop appropriate systems for using the technology in experimental situations. These studies examined: the linearity and period of Cr2O3 release; the effect of presence of capsules in the rumen on voluntary feed intake; the effect of feed type and feeding level on Cr2O3 release rate; and the accuracy of faecal Cr2O3 concentration in predicting faecal output of sheep dosed with CRC when alternative sampling regimens were applied. These experiments, conducted under both indoor feeding and outdoor grazing conditions, established that CRC released Cr2O3 into the rumen in a uniform manner once initiation of matrix extrusion had been completed 2 to 3 days after capsule insertion. The subsequent period of linear release (25 to 100 days) was found to be primarily dependent upon characteristics of the capsules controlled at manufacture (i.e. orifice diameter, matrix composition and length of pressed tablet matrix core). In comparison, environmental factors, both within and outside the sheep, had relatively small effects on the rate or linearity of Cr2O3 release. Release rate decreased by c. 4% if daily feed intake was at 0.7 maintenance compared to an ad libitum level, increased by c. 2% if hay rather than fresh pasture was consumed and decreased by 10 to 13% if capsules were placed in rumen-fistulated sheep rather than in intact animals. Adoption of feeding level below 0.6 maintenance for 4 to 7 days reduced Cr2O3 release rate and could cause capsule failure. Between-capsule variation in release rate from CRC recovered from the rumen by slaughter was low (coefficient of variation 2.0 to 6.5%). Variation between capsules within sheep was usually lower still. Voluntary herbage intake was significantly reduced if sheep were dosed with prototype CRC with inflexible wing designs. Under indoor conditions, correlations of 0.90 to 0.99 between daily faecal output derived by Cr2O3 dilution and actual faecal output for individual sheep were obtained. The correlation between estimates of mean 3-day faecal output of sheep at pasture predicted from the Cr2O3 concentration in morning and evening grab samples and from total collections was 0.87. Prediction of individual animal intakes (indoors) appeared less accurate (r = 0.74) because of variation in capsule release rate and in the animal's own ability to select and digest its diet. Group mean estimates, which are appropriate for practical grazing conditions, were usually within ± 10% of the actual value. Low diurnal variation in faecal Cr2O3 concentration (non-significant) allowed flexible faecal sampling regimens to be applied. In summary CRC were demonstrated to be superior to existing feed intake measurement techniques and to be well suited to the estimation of mean intakes of sheep, provided that suitable faecal sampling regimens were applied. A pilot study investigating the feed intakes and productivity of ewes of different pregnancy and rearing status indicated that intakes of twin-bearing ewes were reduced in comparison to those of single-bearing ewes during late pregnancy, when the two groups were grazed together under "commercial" farming conditions. During lactation, intakes exhibited a curvilinear relationship with time and were generally higher (by up to 32%) in twin-rearing ewes than in single-rearing ewes. This pattern of feed intake was less clear in a subsequent nine-week lactation study. In that trial, experimental groups comprising equal numbers of ewes rearing single or twin lambs were continuously grazed on five different pastures maintained at fixed sward surface heights (2.5, 4.0, 6.0, 7.0 and 9.0 cm). Herbage intakes by both single- and twin-rearing ewes were maximised at a sward surface height of approximately 5.0 cm (1000 to 1100 kg dry matter/ha). Lamb growth rates were not affected by sward height during the first six weeks of lactation because the ewes mobilised body reserves to maintain milk production. All ewes lost liveweight during the first 6 weeks of lactation but only the ewes on the 2.5 cm sward failed to regain lost liveweight from weeks 6 to 9 of lactation. Wool production, strength and colour were not affected by sward conditions in either the ewes or lambs over the lactation period. These results suggest that New Zealand farmers would gain little benefit from differential management of ewes post-lambing where a minimum grazing height of 5.0 cm could be maintained provided that ewes were in good condition (i.e minimum condition score 3.0) at lambing.
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    Studies on the digestion of ryegrass species and the regulation of food intake by sheep : a thesis submitted for the degree of Doctor of Philosophy in the Massey University of Manawatu
    (Massey University, 1964) Ulyatt, M. J.
    The economy of New Zealand is dependent largely on the export of products of the livestock industry. While there has lately been an upsurge in secondary industry, a basic lack of raw materials and cheap labour curtails New Zealand's ability to compete economically with other countries as a manufacturing nation. If New Zealand's position as one of the world's leading agricultural exporters is to be maintained or expanded then increased primary production must be achieved. Such an increase is also necessary to maintain or improve the high standard of living of a rapidly growing internal population. Three general factors are important when the problem of increasing livestock production is considered. 1. Nutrition 2. Breeding 3. Diseases and Pests The interest of the author lies with nutrition but the other two factors are clearly important if animal production is to be improved. Breeding is important particularly in relation to raising fertility and producing types of animals that will give optimum returns in particular environments. It must be remembered however, that genetic improvement by selection of livestock, though essential, is usually slow because of the low heritability of many productive characteristics. Pests and diseases can limit animal production, particularly at high stocking rates, so the prevention of epidemics and the eradication of persistent diseases such as footrot, brucellosis and tuberculosis must continue to be actively pursued. At a symposium entitled, "Problems of Increasing Sheep Production", held in February 1964 by the NewZealand Society of Animal Production, it was evident that the most effective short-term method of increasing animal production would be by increasing stocking rate. This infers increases in both animal numbers and the food to support them. Thus to increase the carrying capacity of the present farming area there must be an increase in the quality and quantity of pasture produced. This can be achieved in two ways: by techniques of pasture management and by breeding improved strains of pasture plants. It must also be remembered that considerable advances may be obtained with improved management of existing strains of pasture plants.
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    Formononetin content in selected red clover strains and its effects on reproduction in ewes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1994) Anwar, Muhammad
    A series of trials were conducted to investigate the oestrogenicity of a low formononetin selection of red clover, 'G27', as compared to the original Pawera red clover. Formononetin concentration was measured in the plants at various stages of their growth. In ewes which grazed Pawera, G27, or Ryegrass-white clover (Control) pastures, comparisons were made of the incidence of ovulation, ovulation rate, and fertility. As the individual isoflavone level for any one strain may vary with growth stage, a study was conducted to characterize formononetin concentration in various components of G27 red clover and Pawera red clover during different stages of plant growth under field conditions. Mean formononetin concentration (percent dry weight) of leaflets and petioles was lower for G27 than for Pawera (P<0.05) at various stages of vegetative leaf development. G27 leaflet concentrations (0.29 ± 0.02) changed little during development compared to Pawera leaflets which declined from 2.16 ± 0.10 in the youngest leaflets to 0.75 ± 0.08 by the end of vegetative leaf development. Formononetin concentration in G27 leaves (leaflet + petiole) at the pre-flowering stage was 0.35% compared to 0.97% in Pawera leaves (P<0.05). At early and late-flowering stages, the formononetin concentration in G27 red clover, on a whole plant basis, was 50% of that in Pawera red clover because the formononetin concentration in petioles and stem of G27 did not decline to the same extent as that in the leaflets. When calculated only for the upper parts of the plant, which are usually ingested by sheep, G27 and Pawera red clover contained 0.27% and 0.99% formononetin, respectively, at the early-flowering stage, and 0.19% and 0.53% formononetin, respectively, at the late-flowering stage. In ewes grazed on various red clover and Control pastures, the main effects studied were ovulation rate and fertility. An investigation was made of the development and the number of follicles in the ovaries and plasma FSH concentrations in ewes grazing either G27 red clover, Pawera red clover, or Control pasture, close to oestrus. A prostaglandin F2α (PGF) injection was used on day 13 of a synchronized cycle to enhance the synchrony of oestrus in ewes. Mean level of blood equol, which is the main oestrogenic metabolite of formononetin in ewes, was significantly lower on G27 red clover (1.81 ± 0.28 μg/ml) than on Pawera red clover (7.25 ± 1.70 μg/ml) (P<0.01). Total number of ovarian surface follicles in Pawera ewes (9.40 ± 1.13) was lower than that in G27 (15.36 ± 1.87) or Control ewes (16.18 ± 2.32) 24 h after PGF injection (P<0.05). Histological examination of the left ovaries conducted 72 h after PGF injection showed that the number of healthy follicles with diameter (D) 1mm4mm) in Pawera ewes but not in any of the ewes in the other two treatments. No differences were observed in the mean plasma FSH concentrations between ewes from the three treatments at various sampling times. Two trials were conducted to compare sperm transport in ewes mated after grazing on Pawera red clover, G27 red clover, or Control pastures. In the first experiment 84 ewes were inseminated each with 500 million spermatozoa at oestrus, after grazing for two oestrous cycles. Mean numbers of spermatozoa in the cranial part of the cervix were not different between various treatments 2 h after insemination. No spermatozoa were recovered from the Fallopian tubes and uteri of many ewes, but this was considered to be due to technical problems. In a second experiment 30 Romney ewes (10 per treatment) were mated to rams after 28 days of grazing either on Pawera red clover, G27 red clover, or Control pastures. The ewes were killed 24 h after service and sperm were recovered from the tract and counted using an improved technique. The number of spermatozoa recovered from different parts of the tract did not differ significantly between treatments, although there was a trend for the low formononetin (G27) ewes to have higher mean sperm numbers than Pawera and Control ewes. In another two trials, ewes (n = 16 per group), that were potential recipients for embryo transfer, grazed on the high oestrogenic red clover (Pawera), low oestrogenic red clover (G27), and Ryegrass-white clover (Control) pastures for 5 weeks around oestrus. In both the trials, the number of ovular ewes and ovulation rate were lower (P<0.05) in Pawera ewes. The ovulation rate in Pawera, G27, and Control ewes in trial 1 was 0.62 ± 0.15, 1.62 ± 0.18 and 1.93 ± 0.27, in trial 2 it was 0.31 ± 0.18, 1.17 ± 0.27 and 1.54 ± 0.14 for the three groups respectively. Following the transfer into suitable recipients of two embryos per ewe, post-mortem examination at 35 days showed a survival rate in Pawera, G27 and Control groups of 50%, 90% and 85% in trial 1, and 50%, 50% and 69% in trial 2. Fertility, and litter size in ewes when fed on the two types of clovers close to the time of mating were studied in another experiment. The treatment groups (n = 25) and grazing lengths prior to mating were: (1) Pawera, 6 weeks; (2) G27, 6 weeks; (3) G27, 12 weeks; (4) G27 / Ryegrass-white clover (Rg-wc), 6 weeks / 6 weeks; (5) Rg-wc (Control 1), 6 weeks, and (6) White clover (Control 2), 6 weeks. Ewes were mated on non-oestrogenic pasture. Ovulation rates in ewes after the first service were not different for all treatment groups (P>0.05). The incidence of returns to service was significantly higher in Pawera ewes (72.7%) than in any of the other groups (P<0.01). The return rates for the other groups were 33.3% (G27/6 weeks), 25.0% (G27/12 weeks), 4.8% (G27/Rg-wc), 9.5% (Rg-wc) and 14.3% (white clover). Most ewes which were mated at the next two cycles became pregnant. The litter size was not significantly different between various treatment groups after 3 cycles of matings. It is concluded that G27 red clover has significantly lower formononetin concentrations than Pawera red clover at different stages of plant growth and development. Follicle growth and ovulation rate in ewes on G27 red clover were not different from those in ewes on non-oestrogenic pasture, and were better than those in ewes on Pawera red clover. The performance of ewes after grazing the low formononetin, G27, red clover was better than that of the ewes that grazed the high formononetin Pawera red clover, because of fewer returns to service and thus earlier mean lambing date. Sperm transport in the reproductive tract, and embryo survival in ewes after transfer of fertilized eggs were also not different in G27 and Control ewes. The study showed that the oestrogenicity of G27 red clover was significantly reduced compared to that of Pawera red clover from which the selection was made.