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Through their influence on embryonic and early fetal development dietary nutrients affect the size, vigour and viability of the newborn and, in the case of sheep, adult ovulation rates. Nutritional regimens that impair post-natal growth reduce ovarian follicular development and delay puberty but have little, if any, effect on either N-methyl-D-aspartate stimulated GnRH release or the pituitary content of gonadotrophins. Nutritional effects on ovulation rate in ewes are not always accompanied by shifts in circulating FSH concentrations. Instead they may operate through altered ovarian hormone feedback mechanisms that influence the duration of exposure of the gonadotrophin-dependent follicles to FSH or through threshold-reducing actions of specific nutrients and dietary-induced metabolites on the amount of FSH needed to support the gonadotrophin-dependent follicles. Recent results suggest that the enhanced faecal excretion of oestradiol by well-fed ewes may increase ovulation rate by reducing ovarian oestradiol feedback. In the post-partum period, the key hypothalamic and pituitary secretions for successful ovulation develop normally despite undernutrition but ovulation is prevented by failure of GnRH release with, in the case of suckler beef cows, a delay in oestrus arising from the repeated development and atresia of dominant ovarian follicles. This effect is accentuated in cows that are in poor body condition at calving. Alleviating the energy deficits of high-yielding dairy cows in early lactation by giving supplements of dietary fat can reduce the interval to first oestrus but subsequent fertility can be impaired. Loss of body protein delays oestrous cyclicity; paradoxically attempts to correct this loss in ruminants by feeding diets high in rumen undegradable protein can stimulate body fat mobilization and milk production with detrimental effects on rebreeding. Excess rumen degradable protein and high feeding levels reduce embryo survival, the latter by suppressing circulating progesterone concentrations. In superovulated ewes diet-induced reductions in progesterone concentrations during oocyte maturation can impart a legacy of developmental retardation leading to decreased embryo survival. In late pregnancy, undernutrition decreases uterine blood flow, fetal insulin and IGF-1 concentrations and impairs growth and development. In the newborn, low insulin and a low selenium and iodine status inhibit thermogenesis from brown adipose tissue. Insulin may also be important in conveying information on nutritional status to the GnRH neurones thereby initiating the cascade of events that is required for successful reproduction in both sexes.

Of 111 variable age, pedigree ewes subjected to a range of superovulatory regimens and then submitted to embryo recovery by laparoscopy, nine had adhesions corresponding to a mid-line laparotomy (presumably from a previous attempt to recover embryos) and could not have their embryos recovered by the laparoscopic technique. Of the remainder, 27 ewes (26.5%) had less than three ovulations or had prematurely regressing corpora lutea at the selected time for embryo recovery (Days 5 to 6 following insemination), and no attempt was made to recover embryos from them. For the 75 ewes subjected to laparoscopic ovum recovery following laparoscopic intrauterine insemination, the average number of ovulations (+/- SEM) was 7.9 +/- 0.6; the average ovum recovery (mean of values for each ewe) was 51.7% +/- 3.5; and the percentage of recovered ova that were fertilized was 87.3%. For a further nine 3-yr-old crossbred ewes the mean values for ovulation and ovum recovery were 7.6 +/- 1.2 and 70.1 +/- 7.7, and were not significantly different for the two insemination methods used (laparoscopic intrauterine vs cervical). In general, ovulation rates for ewes given pregnant mare serum gonadotrophin (PMSG) tended to be lower (5.2 +/- 0.7) than for those given porcine follicle stimulating hormone (pFSH, 7.7 +/- 0.8) or human menopausal gonadotrophin (hMG, 7.7 +/- 2.3). Ova recovery rates were similar on Days 5 and 6 (Day 0 = insemination), and were not affected by method of insemination (laparoscopic intrauterine vs cervical).

In a review of the effects of protein nutrition on reproduction in dairy cattle, Ferguson and Chalupa (1989) expressed concern at the low conception rates to first insemination in high-producing dairy cows and suggested that a contributory factor may be an excess of rumen-degradable protein leading to toxic effects of ammonia and its metabolites on gametes and/or the embryo. More recently Elrod and Butler (1993) have provided data suggesting that degradable protein intakes which were 50% above the requirements for maximum microbial protein synthesis reduced embryo survival in dairy heifers. The objective of the present study was to investigate the effect in ewes of varying the amount of rumen degradable protein during the pre-ovulatory progesterone priming phase and the first four days thereafter on ovulation, fertilization, early in vivo and subsequent in vitro ovum development.

Reproduction in Finnish Landrace × Polled Dorset Horn ewes was accompanied by thickening of the wall of the gall bladder. The thickening was caused by hypertrophy of the epithelium, the presence of cysts, proliferation of blood vessels, glands and fibrous tissue in the lamina propria and hypertrophy of smooth muscle. The changes appeared to be initiated during pregnancy but to persist in a modified and chronic form in post-parturient animals.

Summary Music appreciation deals with the development and application of that general factor in aesthetic judgments described in the main by Burt and Eysenck. This has little to do with appreciation in terms of the assessments of Wing et al. For purposes of identification one might describe seven basic approaches in teaching method. Though each method has its place in success, two methods seem to promise the better result. These methods, the ‘Activity’ and the ‘General discriminative’ might be profitably supplemented by the other five. The effect of a student's appreciation of music is likely to be reflected in his personality and might be termed a measure. It is therefore likely that by studying a student's musical preferences the teacher might better understand his personality which in turn might facilitate sound appreciation of music.

Summary The use of sheep as convenient small ruminants for fundamental studies on digestive physiology and substrate utilization together with direct observations on their nutrient requirements for maintenance, pregnancy and lactation, has provided us with a comprehensive framework for the formulation of optimal feeding strategies for the breeding ewe. What this chapter demonstrates is that rarely do these feeding strategies involve meeting the exact nutrient requirements of the ewe at each stage of her reproductive cycle. Instead, for practical, economic and indeed sound physiological reasons they involve periods in which nutrient intakes exceed requirements and others where they are below requirements, the overall aim being to achieve balance in the composition of the body over the breeding cycle as a whole. Failure to achieve the correct body condition at mating leads to suboptimal ovulation rates. Equally damaging to overall reproductive performance are extremes of nutrition in the first month of pregnancy in that they are detrimental to embryo survival. During the second and third months of pregnancy, a period when the nutrient requirements for conceptus growth are minimal, there is now evidence that a mild degree of undernutrition is beneficial to placental growth and lamb birthweight in ewes that are in good body condition at mating. Recent advances in our understanding of the interrelationships between energy and protein and their effects on fetal growth and milk production have allowed greater flexibility in diet formulation and have provided us with a means of efficiently using body fat reserves at a time when energy requirements invariably exceed intake. Due to the fact that for most sheep production systems, housing is intermittent rather than continuous, few attempts have been made to develop an overall feeding strategy for continuously housed ewes. This chapter contains a description of the diets, feeding regimes and levels of reproductive performance achieved by a continuously housed flock of highly prolific ewes maintained on a 7 month lambing interval.