The effects of different dietary essential fatty acids on piglet tissue composition at birth and performance until 7 days post weaning were investigated by offering the sow diets containing (17·5 g oil per kg diet) either maize oil (MO) as a control treatment, tuna oil (TO) as a source of long chain n-3 polyunsaturated fatty acids, particularly 22:6 n-3, or a mixture of maize and linseed oils (LO) which supplied the same amount of n-3 acids as TO but in the form of 18:3 n-3. Ten sows were allocated to each treatment which was offered throughout pregnancy and lactation. Compared with MO, offering TO increased sow plasma and subcutaneous adipose tissue 22: 6 n-3 proportions whereas LO increased 18: 3 n-3 and, to a much lesser extent than TO, 22: 6 n-3. Offering TO to the sow increased the proportions of 20: 5 n-3 and 22: 6 n-3 in piglet brain and liver at birth and decreased the n-6 acids, 20: 4, 22: 4 and 22: 5. LO only increased piglet liver 20: 5 n-3 proportions but to a lesser extent than TO; however, LO also decreased the proportions of 20: 4, 22: 4 and 22: 5 n-6 in piglet tissues. Offering the pregnant sow dietary 18: 3 n-3 therefore increased deposition of 22: 6 n-3 in foetal piglet tissues to a much lesser extent than tuna oil and so it is necessary to offer the sow pre-formed 22: 6 n-3 in order to achieve maximum foetal 22: 6 n-3 deposition. By experimentally allocating piglets at birth, effects of sow nutrition during pregnancy and lactation were separated. Piglets sucking MO or TO sows were heavier than piglets sucking LO sows 7 days post weaning.

The objective of this study was to assess the growth and development of carcass composition of entire male and female lambs of three British hill breeds (Scottish Blackface, Welsh Mountain, and Shetland), from weaning to approaching maturity, when kept under conditions designed to be nutritionally non-limiting. Lambs were weaned at 8 weeks of age and given a high-quality pelleted diet ad libitum until slaughter at one of five different degrees of maturity. The Gompertz growth function was used to characterize, for each genotype, the growth curve and to provide estimates of mature weight. As expected, there were significant effects of breed and sex on both food intake and growth rate. Growth rate was depressed, relative to the Gompertz fit, during the months of October to January, and intake was similarly depressed. The estimates of mature weight for the females of each breed were: Scottish Blackface, 69; Welsh Mountain, 61; Shetland, 46 kg. The mature weights of the males were found to be not significantly different from 1-3 times the mature weight of females. Relationships between carcass composition and live weight were derived by allometric regression. This study provides the first full description of the growth and meat production potential of the three breeds.

Fifty-four lean genotype crossbred gilts were allocated at 118 days of age among three diets with different protein concentrations to give lysine: energy (g/MJ digestible energy) ratios: high (0·9), medium (0·6) and low (0·3) given twice daily at 2·9 × maintenance energy. At 160 days of age, gilts were treated with exogenous gonadotropin (PG600™) and animals were examined daily for signs of oestrus. Animals were slaughtered after the second oestrus, if they had shown behavioural oestrus, or at the age of 212 days. Reproductive tracts were recovered for counting of corpora lutea and albicantia. L gilts were lighter than M or H gilts at puberty induction (80, 95, 97 (s.e. 0·73) kg for L, M, H respectively, P < 0·001), with greater backfat thickness (10·8,10·0, 9·2 (s.e. 0·21) mm P2,P < 0·001), lesser longissimus muscle depth (57·4, 65·9, 64·3 (s.e. 0·77) mm, P < 0·001) and poorer food conversion ratio during rearing (3·87, 2·48, 2·42 (s.e. 0·098) kg food per kg gain, P < 0·001). There was no statistically significant difference in the total number of animals that responded to the puberty induction, although L had a greater latency to oestrus than H. Ovulation rate at this induced oestrus was significantly lower in L gilts than in M or H gilts (12·5, 17·3, 21·5 (s.e. 1·32), P < 0·02). A lower proportion ofL, compared with M or H gilts showed spontaneous ovulation in a subsequent cycle (0·15, 0·75, 0·77, %2 = 12·72, P < 0·005). It proved possible, by means of low protein (lysine) diets, to increase body fat reserves in breeding gilts but protein restriction in the rearing phase negatively affected aspects of reproductive performance.

Experimental sheep in nutrition trials are commonly housed individually in slatted, unbedded pens and receive a concentrated, pelleted ration. Under these conditions a number of abnormal oral activities are performed including bar-biting, slat-chewing and wool-eating (Marsden and Wood-Gush 1986, Cooper et al 1994). These have been described as a functionless, stereotypic response to a restrictive or frustrating environment. They may, however, be the redirection of feeding motivation to apparently inappropriate substrates, when presented with a diet which does not satisfy all the sheep's nutritional needs. In this experiment the effect of a fibrous diet, which provides a substrate for chewing and/or rumination, on the performance of abnormal oral activities was examined, since pellated rations are usually low in effective fibre.

A previous study (Rooke et al, 1997) showed that in normal commercial feeding conditions there were large differences between litters in live-weight gain at weaning and in immune response to inclusion of soyabean meal. The current experiment attempted to separate these maternal influences into pre- and post-partum effects and investigated whether maternal diet fatty acid composition influenced piglet performance.Five groups of 6 sows (Large White x Landrace) were used. At weaning, sows were grouped into threes by live-weight and backfat thickness and allocated to one of three diets which were fed throughout pregnancy and lactation. Pregnancy and lactation diets were formulated to supply 12.5 and 14.0 MJ DE, 140 and 180 g CP and 4.5 and 8.5 g lysine / kg. Pregnancy diets contained 17.5 g/kg of either maize oil (M), linseed + maize oil (60:40 ratio, L) or fish oil (Tuna Orbital Oil, Scotia Pharmaceuticals Ltd, F) and lactation diets 35 g/kg oil (17.5 g maize oil + amounts in gestation diets). Six groups of 3 sows participated in a cross-fostering study. All sows were induced to farrow on day 113 or 114 of gestation. Piglets were removed from the sow until farrowing was complete to avoid colostrum consumption. Nine piglets / sow were chosen for cross-fostering from each group of 3 sows (1/diet). Piglets were grouped into threes by weight and allocated to each of the 3 sows. The piglets were reared on the sows with no access to creep feed until weaning at 28 days of age. At weaning the piglets were kept in their lactation sow groups and fed a common diet (16.3 MJ DE, 240 g CP , 15.5 g lysine / kg) based on cooked cereals, milk products and containing 150 g / kg soya bean meal for 7 days. Piglets were weighed at birth and weekly thereafter. The data were analysed using the REML procedure of Genstat to quantify variance relating to sow effects (during pregnancy and lactation) and of pregnancy and lactation diets.