Increased prolificacy is often believed to increase the incidence of both lamb and ewe mortality especially in harsher environments. Fecundin® (Coopers Pittman Moore) is a vaccine which leads to immunization against androstenedione and a resulting increase in prolificacy (Rhind, 1987). The use of this drug gives a method of manipulating prolificacy without confounding any effects with improved nutrition, the most usual means of modifying reproductive success.

A programme was commenced in 1985 in which half the ewes in a flock of Scottish Blackface ewes was vaccinated with Fecundin (F), the remainder left unvaccinated (N). In subsequent years ewes were maintained on the same treatment. The data presented here are an analysis of a single age group of ewes completing a full lifetime on each treatment. Eighty-five ewes were allocated at random to each treatment. These were vaccinated in autumn 1985, given a booster vaccination 4 weeks pre-ram joining in 1986, 1987 and 1988 and sold as ‘cast for age’ after lamb weaning in 1989. With the exception of injection with Fecundin, at all times management was independent of treatment.

Lamb mortality is high in hill farming systems. This is not a new phenomenon. Orr and Fraser (1932) reported losses of lambs between birth and weaning of over 30% and indeed an annual ewe death rate of up to 24%.

Poor nutrition, of both macro- and micro-nutrients, is a prime cause of this problem exaggerated by difficult environmental conditions at the time of birth. Improved nutrition during late pregnancy was believed to be the most important (Wallace, 1948) and nutrition during mid pregnancy received scant attention. However, applied experiments with mid-pregnancy feeding of hill ewes (Milne, 1984; Waterhouse and McClelland, 1987) showed very significant effects of better nutrition during this period. The present paper summarizes the implementation of improved mid-pregnancy nutrition in a monitored systems study, associated with changes in management in late pregnancy made possible by assessment of foetal numbers from ultrasound pregnancy scanning.

The birth weight of the piglet has an important influence on many aspects of later performance. There are, for example, relations between birth weight and growth rate as well as between birth weight and litter traits at farrowing (Rydhmer, Eliasson, Stern, Andersson and Einarsson, 1989). In a shorter perspective, birth weight affects piglet survival during the first weeks of life.

High Utter size (number born) is a common breeding goal. Piglet weight is related to the number of piglets in the Utter. Piglet weight is also related to survival; thus mortality increases with litter size.

The aim of this work was to study variation in piglet weight, some factors that may influence piglet weight and relations between litter size, piglet weight and piglet survival.

Individual piglet weights were registered in 747 litters from an experimental farm. Of the 8134 piglets born, 2326 were Swedish Yorkshire, 239 Swedish Landrace, and the rest were crosses between these two breeds. One-third of the piglets were born in gilt litters. The piglets were creep fed from the 2nd week and weaned at 6 weeks of age. They were individually weighed at birth and at 3, 6 and 9 weeks of age. Birth weight in this report refers to the weight of all piglets born, including those stillborn.

Adrenal glucocorticoids are known to stimulate the development of digestive enzymes in the sucking rat. In the pig, Cortisol concentrations in plasma reach peak levels at birth. We studied the effect of neonatal Cortisol levels on the development of two proteases, chymosin (rennin, EC 3.4.23.4) and pepsin A (EC 3.4.23.1) in the stomach of the pig.

Material and methods Three vaginal-delivered (VD) pigs (114 to 115 days gestation) were killed at birth. The remaining 40 newborn pigs were removed by caesarean section (SC) at 111 to 112 days gestation (i.e. 2 to 4 days before term). After birth these pigs were injected intramuscularly with either saline, metyrapone (an inhibitor of adrenal 11-deoxyhydrolase activity and Cortisol synthesis, 10 mg/kg per day) or ACTH (adrenocorticotropic hormone, 100μ/kg per day).

Although natural weaning in the pig occurs at 6 to 8 weeks of age it is common commercial practice to wean at 3 to 4 weeks. This abrupt and early weaning is often associated with a more or less prolonged check in growth, frequent occurrence of gastrointestinal disease and a significant mortality. The transition from a milk diet to a solid diet in the post-weaning period necessitates complex digestive and metabolic adaptations in the piglet. Experiments in small animals have shown that some of the changes brought about by weaning are at least partially controlled by hormones from the adrenal cortex (Henning, 1981).

We have investigated the changes that occur in the mucosa of the small intestine and in the pancreas of pigs weaned at 21 days of age. In addition we have investigated the effects of an orally administered synthetic glucocorticoid (dexamethasone; DEX) given before weaning, on the development of the intestine and pancreas.

Two pigs from each of six litters were killed at 18 days of age, half of the remaining pigs were given DEX (0.4mg/kg ) suspended in agar (0.5%). This dose was divided into four equal aliquots and given by stomach tube on days 19 and 20. Controls received an equivalent volume of agar. Pigs were weaned at 21 days, two control and two DEX treated pigs were killed on the day of weaning and at 28, 35 and 42 days. After weaning pigs were allowed ad libitum access to a commercial starter diet.

The period of growth from parturition to weaning is a time of rapid fat deposition in many species. In the pig, body fat increases from about 10 g/kg at birth to 150 to 200 g/kg by 21 days of age (Wood and Groves 1965; Whittemore, Aumaitre and Williams, 1978). An adequate reserve of adipose tissue may be crucial to ensure health and survival, for example during the period of low food intake frequently observed after weaning.

It is likely that the nutrient composition of milk and the hormonal signals elicited by milk consumption play an important rôle in stimulating fat deposition. We have investigated the effects of milk ingestion on release of the gastrointestinal hormones GIP (gastric inhibitory peptide) and GLP-1 (glucagon-like peptide one). In addition, we have studied the effects of these hormones on fatty acid synthesis in vitro.

Explants (0.4 to 0.6 mg) of adipose tissue were obtained from three anatomical sites of an 18-day-old pig fasted for 12 h. The explants were pre-incubated for 90 min and then incubated in the presence of hormones and [14C] acetate (0.2μCi/ml). Triacylglycerols were extracted from the explants and following saponification, fatty acids were separated and radioactivity counted.

The colostrum of many species will stimulate the growth of cells in vitro and colostrum ingestion may play an important rôle in directly promoting the growth of the gastrointestinal tract in the newborn animal (Berseth, Lichtenberger and Morriss, 1984). Most studies have suggested however, that growth-promoting activity declines to zero, or to negligible levels in post-colostrum milk (Shing and Klagsbrun, 1984; Cera, Mahan and Simmen, 1987). We have investigated the ability of sow's milk, collected up to 21 days of lactation, to stimulate the growth of epithelial cells in vitro. For these studies we use cells derived from the mucosa of the small intestine: RIE-1 cells (Blay and Brown, 1984) and a lung-derived cell line: CHV79 cells.

Milk was collected from three sows at each of the following times: 0 (colostrum), 7, 14, and 21 days post partum. The samples were defatted by centrifugation (30 000 g for 40 min), filter sterilized and diluted in phosphate buffered saline (PBS, pH 6.8). RIE-1 cells (a generous gift from K. Brown, Brabaham) or CHV79 cells were grown to confluence in Dulbecco's modified Eagle's medium (DME) containing foetal calf serum (FCS, 10%). The cultures were quiesced in a medium containing 0.5% FCS for 24 h and milk samples added in serum-free PBS for a further 24 h. [3H]-thymidine was added for the final 4 h before cells were harvested. Growth-promoting activity of milk samples are expressed as a stimulation index (SI) i.e. in relation to the amount of label incorporated after incubation with an equivalent volume of PBS. Fractionation of the growth-promoting activity of a pooled post-colostrum milk sample was performed on sephacryl S-200sf and S-300sf columns.

In designing feeding regimens for sows much attention should be paid to the effects on piglet performance and piglet mortality, as these traits are of great economic significance. Clearly, piglets may be influenced by sow feeding regimen in several ways. For example, sows offered food ad libitum may be calmer and hence step upon or overlay fewer piglets than sows restrictedly given food. A gestation diet with a low protein content and protein of vegetable origin may reduce the frequency of agalactia (Ringarp, 1960; Göransson, 1989) and thereby enhance piglet survival.

In a sow feeding experiment performed at the Swedish University of Agricultural Sciences, the Swedish feeding standards (Simonsson, 1988) were compared with offering food ad libitum in lactation and a simplified gestation diet. The main objective was to study effects on sow weight and backfat changes and reproductive traits, but effects on piglet mortality were also studied.

The experiment was performed at the pig research station of the Swedish University of Agricultural Sciences from 1986 to 1990. The following treatments were applied.

Susceptibility to cold is usually reported as a major factor involved in the neonatal mortality of piglets (English and Morrison, 1984). Low energy reserves and poor insulation largely contribute to the limited thermoregulatory capacities of the newborn pig (Mersmann, 1974; Curtis, 1974). Glycogen is the predominant source of energy accounting for about 0.6 of the total energy available at birth (Mellor and Cockburn, 1986) but glycogen stores are rapidly depleted after birth. In addition, the total body fat content is very low at birth, ranging from 10 to 20g/kg (Manners and McCrea, 1963). Whereas attempts made to increase the energy stored as fat in the newborn pig by manipulation of the sow diet during late gestation have given variable results (Seerley, 1984), colostrum has proved to be an efficient route for depositing fat and hence for the supply of energy to the piglet during the first postnatal day (Le Dividich, Esnault, Lynch, Hoo-Paris, Castex and Peiniau, 1991). The present study was designed to determine the effects of colostral fat level on the energy and fat metabolism of the newborn piglet when maintained during the 1st day of life at thermal neutrality (34°C) or in the cold (21°C).

A total of 35 newborn Large White pigs averaging 1140 (s.e. 54) g in weight were used. Within each litter five piglets were selected according to their live weight. One was killed in order to determine the initial body composition. The remaining pigs were fitted with umbilical artery catheters and stomach tubes. They were placed in individual cages in closed temperature-controlled chambers maintained at either 34 or 21°C and were fed normal colostrum (60 g fat per kg, NFC) or a colostrum deprived of fat (< 10 g fat per kg, LFC) at the rate of 15 to 18 g per meal per kg birth weight. A total of 24 meals were given at about 65-min intervals.