With the advent of twinning in beef cows there is a need to obtain information on the nutritional requirements of these animals during the last three months of pregnancy and to assess the effects of pre-calving nutrition on cow and calf performance in the subsequent lactation. Three experiments have been carried out With 10, 9 and 14 multiple bearing Hereford x British Friesian cows. In each experiment a comparison was made With single bearing cows but the results from these animals are not considered in this paper. The cows were given different energy intakes in a factorial arrangement with low or high levels of UDP over the last three months of pregnancy. After calving all cows were given 125 MJ ME/d for the first 12 Weeks of lactation and performance monitored to assess any carryover effect of pregnancy nutrition.

Similar diets were fed during the last three months of pregnancy in all three experiments. The diet containing a low level of UDP (0.19 of total protein) consisted of barley straw, barley grain, molassed meal and urea. While that With a high UDP content (0.33 of total protein) contained barley straw, barley grain, malt distillers dark grains and special propietary cubes.

It is well known that cattle can exhibit compensatory growth following a period of food restriction. The cause of the phenomenon has been attributed to reduced maintenance requirements, increased food intake and changes in the composition of the tissue gained. It is not clear whether changes in the composition of tissue gained occur independently of the other possible causative factors.

There is a belief, held by many in the meat industry, in catering, and by consumers alike, that meat from leaner carcasses is inferior in eating quality to that from fatter ones. In addition, meat from leaner continental breeds has been suggested by some to be inferior to that from the more traditional British beef breeds which fatten more readily at lighter weights, and meat from bulls has been similarly implicated. This may be an extrapolation of the belief in the role of fat, or it may be a separate issue concerned with other underlying genetic or physiological differences. Other factors known to influence meat quality are pre-slaughter handling and post-mortem chilling rates and conditioning. Rapid chilling of beef carcasses has economic advantages through a faster turnover and lower evaporative losses, but may impair eating quality by inducing muscle cold-shortening. Chill rate may be influenced by carcass type, in particular by the amount of fat present and by the thickness of the tissues. It is possible that the role of fatness (and conformation) in eating quality of meat may be manifested indirectly through its effect on rate of cooling.

Two randomised-block experiments have been carried out to examine the relative feeding value of wheat and barley as supplements to grass silage for finishing beef cattle. In each experiment unwilted, formic acid-treated silage was offered ad libitum and supplemented with 500 g soyabean meal and 50 g minerals and vitamins to 44 twelve month old bulls for 157 and 172 days in experiments 1 and 2 respectively. In addition 12 animals received 2.5 kg rolled spring barley (LB), 12 received 4.0 kg barley (HB) and 20 received 3.25 kg rolled wheat (W). Silage was offered once daily and concentrates twice daily in two equal meals.

Eleven British Friesian bulls and thirty-three bulls which were Friesian x Continental beef breed were used in each experiment. They were initially 402 and 385 kg live weight in experiments 1 and 2 respectively. In both experiments the animals were housed and fed in groups of four in slatted pens. All animals were slaughtered at the end of the experiments to obtain carcass data.

The increased consumer awareness of diet and health related aspects has increased the demand for leaner beef. Nutritional factors which influence carcass composition include plane of nutrition, diet type, forage:concentrate ratio and protein supplementation. An experiment has been carried out to examine the independent and interacting effects of protein supplementation and forage:concentrate ratio on performance and carcass composition of finishing beef heifers.

The six experimental diets used consisted of two dietary crude protein (CP) levels (142 (LP) and 175 (HP) g CP/kg dry matter (DM)) each offered at three forage:concentrate ratios in a 2 x 3 factorial design. High (HF), medium (MF) and low(LF) forage diets contained on a DM basis 0.75, 0.50 and 0.30 grass silage and 0.25, 0.50 and 0.70 concentrates respectively. In the HF diets, grass silage was offered ad libitum but intake was restricted in the MF and LF diets so as to equalise total metabolisable energy (ME) intakes for the six diets. In the LP diets, the control concentrate consisted of (g/kg) 925 ground barley, 50 molasses and 25 minerals and vitamins.

For those involved in suckler cattle systems, there are likely to be several new opportunities for increasing production efficiency in the years ahead. As a result of recent developments in embryo production technology the future is likely to see embryo transfer being used on an increasing scale and eventually taking over from artificial insemination as a major factor influencing the production of beef calves. Sex control techniques, applied to sperm or to embryos, are likely to be of particular value in making bull calves available for twinning or heifer calves for once-bred heifer production systems. The paper examines the various possibilities for applying reproductive technology in enhancing fertility, controlling oestrus and ovulation, inducing twin births, increasing the efficiency of once-calved heifer production systems,in the application of cloning techniques and the use of recombinant DNA technology.

The financial success of beef cow enterprises depends to a large extent on efficient control of cow feeding. The fact that the single suckled beef cow has to be maintained for a whole year to produce one calf means that the cost of feeding the cow represents the biggest single variable cost. Thus winter feeding must be controlled to ensure the correct balance between feed inputs and cow and calf performance, and summer grazing management must be designed to ensure high animal performance, high output per hectare and efficient grassland utilization.

Eighty percent of foetal growth occurs during the last 3 months of pregnancy and so any effect of energy restriction on calf birth weight should be most evident at that time. Russel et al (1979) showed that relatively severe levels of undernutrition were required to reduce calf birth weight by 10-15% and that subsequent calf viability and growth rate were unimpaired.

Major changes are taking place in the UK beef industry, as a result of the reduction in dairy cow numbers due to milk quotas. Similar reductions are taking place throughout Europe and have resulted in a strong export market for UK calves. Consequently in 1988 there were 800,000 fewer calves available for beef production than there were when quotas were introduced. This downward trend is forecast to continue and by 1990 the EEC will no longer be self-sufficient for veal and beef.

At times of calf shortages the concept of once-bred heifer beef (producing one calf out of a heifer otherwise destined for slaughter as clean beef, and then slaughtering her shortly after calving) has been considered as a way of generating extra calves and meeting the shortfall. Historically low fertility in young heifers, and high levels of dystokia have limited the commercial uptake of the technique. In addition returns have been low because heifers that have produced a calf are not eligible for Variable Beef Premium payments and, being unfamiliar with this type of slaughter animal the meat trade has regarded tham as cull cows and paid a reduced price.

Milk quotas have resulted in a reduction in dairy cow numbers between 1983 and 1987 which represents a loss of almost 250,000 calves for beef rearing. Increasing slaughter weights is one way to make up for some of the consequent shortfall in beef production. However slaughter weights will not increase unless it is profitable to the producer.

MLC investigations are showing that differences in performance within a group of finishing cattle means that there is extra profit in keeping faster growers longer than average. Table 1 shows slaughter weights of a group of Charolais cross male suckled calves at different ranges of daily gain. Optimised slaughter weights for each sub-group and the extra gross margin after interest which should have accrued if they had been sold at the optimised weights are also given. Within the group the fastest growing bulls should have been kept longest and would have shown the biggest increase in margins.

Icelandic sheep, the only breed in Iceland, belongs to the North European short-tailed group of sheep which includes the Finnish Landrace and Swedish Landrace breeds (Adalsteinsson, 1970). The breed was brought to Iceland during the settlement period (870-930 AD) and it is believed that there has been little if any genetic introduction from outside the country during the last 200 years. The average litter size is about 1.7 with a remarkably low incidnce (˂1.5%) of triplets. The conception rate to a single cycle in the absence of synchronisation is reputedly greater than 90%. There is also evidence for the presence of a gene (Thoka gene) with a large effect on litter size in certain flocks (Jonmundsson and Adalsteinsson, 1985). The low incidence of triplet births and the apparently high conception rate suggest that the distribtuion of ovulation rate and the level of embryo survival may be different from those of typical British breeds.

The problem of partial or complete failure of fertilization following cervical insemination in superovulated ewes submitted for embryo transfer can largely be overcome by depositing semen directly into the uterine lumen. However this technique, when carried out by mid-line laparotomy in superovulated ewes is associated with a significant reduction in ovum recovery (Trounson & Moore, 1974; Boland & Gordon, 1978). Although the recent introduction of laparoscopic intrauterine (IU) insemination has now removed the need for major surgery when inseminating superovulated ewes its use in non-superovulated ewes often results in a slight depression in litter size (McKelvey, Robinson, Aitken & Henderson, 1985). Such results imply that it too may reduce embryo recovery rates. Indeed our initial experience with the widespread use of the laparoscopic technique to inseminate superovulated ewes, although devoid of proper conventionally-inseminated controls, gave disappointingly low values for embryo recovery.

The present study was carried out therefore to determine the effect of direct intrauterine versus natural cervical insemination on egg recovery and fertilization rates in ewes superovulated using porcine FSH or PMSG and GnRH.

The deposition of semen under laparoscopic visualisation directly into the uterine lumen alleviates the problem of low fertility in superovulated ewes. However, we have recently demonstrated that intrauterine insemination when carried out at 52 h after progestagen pessary withdrawal results in a significant reduction in the percentage of embryos recovered. This observation seemed to suggest that intrauterine insemination, the timing of which was chosen to coincide with ovulation, is interfering with collection of the oocytes by the fimbria or altering the rate of oocyte transport. The present experiment was carried out to test this hypothesis by assessing ovum recovery and fertilization rates following intrauterine insemination unilaterally in the right horn only or bilaterally, at either 48 or 60 h after progestagen pessary withdrawal.

Twenty-five Finnish Landrace x Dorset Horn ewes were studied during seasonal anoestrus in May 1988. Ewes were individually penned under natural lighting conditions (57°N 2°W) and were offered 1.4 kg per day of a complete diet supplying 9 MJ of metabolizable energy/kg.

One hypothesis for the adverse effect which a high food intake in early pregnancy has on early embryo mortality in gilts is that it increases blood flow through the liver and in consequence the rate of removal of progesterone from the blood. To study this aspect the metabolic clearance rate of progesterone (MCR) from plasma and the rate of blood flow in the portal vein were measured concurrently during 14 hour periods in six ovariectomised gilts, weighing 70 to 80 kg, when their food intake was 1 and 3 kg/day. To determine the MCR, progesterone was infused into a jugular vein at 70 ug/minute for 36 hours. The concentration of progesterone was determined in plasma samples collected from a cannula in the posterior vena cava at 20 minute intervals during the last 14 hours of infusion when an equilibrium had established between the rates of infusion and clearance. Because ovariectomy removed the principal endogenous source of progesterone, body fat became depleted of the steroid. Therefore, a priming dose of approximately 100 mg of progesterone in arachis oil was given intramuscularly 48 and 24 hours before each infusion started.

A previous report from this laboratory dealt with the establishment of pregnancies in the early months of gestation after the non-surgical transfer of cattle embryos derived from the in vitro maturation (IVM) of primary bovine oocytes, their fertilization in vitro (IVF) and their subsequent development to the transferable stage (morula/blastocyst) using an in vivo (sheep oviduct) culture system (Lu et al.,1987). The present report deals with some factors affecting the efficiency of IVF and with the culture in vitro of zygotes to the morula/ blastocyst stage of development. Some embryos were frozen and after thawing transferred by non-surgical procedures to five recipient cattle to obtain information on their capacity to undergo further embryonic development.

Primary oocytes, enclosed in cumulus cells, were recovered from vesicular follicles (2-6mm) after their dissection from the ovaries of heifers slaughtered at a local abattoir. The ovaries were brought to the laboratory within one hour of animal slaughter in medium held at 35'C.

The major components of economic performance in pigs - growth rate, feed conversion ratio and carcass merit - have been the targets of selection for a number of years in the closed herds of breeding companies. Over the past 20 years substantial progress has been made for these traits. Declining fatness in closed herds may lead to a decline in the genetic variation for growth and carcass traits, and thus reduced opportunities for selection. This could arise either as genetic variation is exhausted in closed lines, or as physiological selection limits are approached. In this study genetic variation in closed lines with a history of selection for growth and carcass traits was investigated.

The data were collected from two closed lines between 1979 and 1985 by the Cotswold Pig Development Company Ltd. The two lines were housed on a single farm in the same environment and had a history of selection based upon an index of growth rate and fat depths. There were 167 sires with 4722 male and 5386 female progeny in line A, a synthetic breed based largely upon the Landrace breed, and 164 sires with 4160 male and 3887 female progeny in line B, derived from the Large White breed.

The main selection objective in pig breeding is efficient lean meat production. Selection for leaner meat has been associated with reduced meat quality (Kempster et al, 1986) and with reduced eating quality, but the latter was not substantiated in the study of Wood et al (1986). The genetic relationships between carcass traits and meat/eating quality traits need to be quantified, so that calculation of selection Indices for increased efficiency of lean meat production can take account of correlated changes in meat and eating quality traits.

Duroc and halothane negative British Landrace pigs were performance tested on ad-libitum or restricted (0.75 g/g of ad-libitum) feeding, with like-sexed, non-littermate groups of one, two, three and four pigs per pen. Pigs started performance test at a within pen average weight of 30 (±3) kg and finished test at either a within pen average weight of 80 (±5) kg for pigs fed ad-libitum or after 70 days on test for restricted fed pigs. Half carcasses were dissected and shoulder joints and loin chops were used for objective measurements of meat quality and trained taste panel assessment of eating quality.

The goal of livestock genetic improvement is maximun increase in the economic efficiency of production (economic merit). When several traits contribute to economic merit, optimum genetic improvement can often be achieved by use of a discriminant function of available information (known as a selection index) which maximises expected genetic progress in the aggregate genotype, economic merit. This approach assumes that economic merit is a linear function of genetically controlled outputs. Although this may not always be true, since genetic responses are usually relatively small (0.005 to 0.020 of the mean per year) any non-linear effects are second-order and can generally be ignored. Economic optimization procedures which match production environments to genotypes would generate effectively non-linear functions, such non-linearity will generally be small. Thus the selection index approach can be applied, provided that functions describing economic merit are based on previously optimized production environments.

Apart from the MLC indices for hill sheep (MLC, 1986) and Atkins’ (1984) study for Scottish Blackface sheep, little attention has been directed towards the general implementation of selection indices in hill sheep production, despite the fact that hill sheep constitute the backbone of the British sheep industry (eg. the genetic contribution of hill sheep to lamb carcass meat was estimated at 33 per cent, to total lambs slaughtered 36 per cent, and to dams of the lambs slaughtered 56 per cent - see MLC, 1988)

The purpose of this paper is to try to define appropriate breeding objectives for hill sheep that could be incorporated in a selection index, in order to improve output and efficiency of sheep production in such a limiting environment.

The Cambridge is a highly prolific composite breed derived mainly from the Clun Forest (53%) and Finnish Landrace (25%) breeds with minor contributions from ten other breeds (Owen et al 1980; Owen, 1982). Ovulation rate in Cambridge ewes is characterised by high variability (range 2-13; CV = 0.55) and high repeatability (r = 0.86) between years (Hanrahan and Owen, 1985). These observations suggest the segregation of a gene with a large effect on ovulation rate. Further investigations of variation in ovulation rate have been undertaken based on a small flock of Cambridge ewes and crossbred progeny of six Cambridge rams.

Based on a single measurement of ovulation rate in October, 1983 on Cambridge ewes in the flock of University College of North Wales (UCNW) nine ewes were selected and imported to Ireland, together with four ram lambs, in August, 1984. The ewes chosen were those with the highest ovulation rate of those available (mean = 7.9) and the ram lambs were selected from dams with the highest ovulation rate (mean = 7.0). One additional ram lamb was purchased in 1985 from a private breeder in Northern Ireland who had purchased the parents from the UCNW flock.

The objectives of the trial were to investigate the effects of bovine somatotrophin (BST) from either week 2 or week 10 post-partum on the yields of milk, milk components, body weight, body condition, feed intake, health and reproductive status of dairy cows over a second consecutive lactation. The results from the heifer lactation have been reported previously (Butterwick et al. 1988).

17 Friesian dairy cows in their second lactation were continued on the same treatment as in their heifer lactation: daily subcutaneous injection of recombinantly derived bovine somatotrophin (BST;25mg/d) from either week 2 (BST2;n=6) or week 10 (BSTl0;n=5) post-partum, or injection of a buffer solution from week 2 of lactation (C;n=6). Treatments continued until week 42 of lactation or until 60 days prior to predicted calving date, if this occurred before week 42 of lactation. Initially cows were housed in cubicles and fed ad libitum through Calan doors, on a diet consisting of concentrate and grass silage (Table 1) on a 60:40 dry matter ratio. After day 110 of lactation cows were turned out to pasture but continued to receive concentrates according to milk yield and body condition score. Milk yield and feed intake were recorded daily, milk composition, body weight and body condition score were recorded twice weekly. Health and reproductive status were monitored over the lactation.