The effect of undegradable protein supply was studied in overfat lambs given low-energy diets to reduce carcass fatness. Two trials involving sequential batches of 48 overfat Suffolk × lambs investigated the effects of supplementing an ad libitum straw diet with either 0 or 100 g fish-meal pellets daily for 14-, 28- and 42-day periods. Lambs supplemented with fish meal in trials 1 and 2 lost significantly less weight. Weight losses (g/day) were - 2 v. -129 (s.e.d. 26) and -5 8 v. -188 (s.e.d. 29) respectively. There were highly significant and favourable effects of fish-meal supplementation on carcass weight and composition (recorded in the second trial only). Carcass weight (kg) after 14, 28 and 42 days was 21·8, 20·4 and 18·3 for unsupplemented lambs and 22·4, 21·9 and 21·6 for supplemented lambs; saleable lean (kg) as determined by a commercial boning-out process was 12·1, 11·3 and 10·0 v. 12·7, 12·6 and 12·3 respectively. There were corresponding changes in conformation but fat trimmed off the carcass was not significantly reduced by the dietary treatments. There was, however, a reduction by one-fifth in excess carcass fat (about 0·5 kg) over the period 14 to 42 days on trial, and over the trial as a whole, fat trim fell from an estimated proportion of carcass weight of 0·17 to 012, equivalent to a fall in Meat and Livestock Commission fatness score from 4H to 3L. Results indicated very favourable financial rewards for supplementing diets of overfat lambs with fish meal.

Investigations were made of the effects of the fi-agonist cimaterol on the growth and hormone status of normal and double-muscled Belgian White-blue bulls. Results indicated that repartitioning effects of this agonist may in part be mediated indirectly through an alteration in the levels of metabolic hormones and that the growth promoting effect is transient.

Milk composition in Awassi sheep was determined in relation to time of milking, stage of lactation and age of ewe. About 80 ewes of the main flock of the Kraim Centre, were used. Fat, total solids and solids not fat proportions were not significantly affected by age of ewe, but they increased as stage of lactation advanced. With equal intervals of milking of 12 h, milk fat and total solids proportions were higher in the evening milk than in the morning milk although no differences between the morning and evening in the quantity of milk obtained were observed.

Path analysis was applied to correlations among lamb carcass measurements. Correlations were obtained from lamb carcasses averaging 15·7 kg and 270 g fat per kg carcass weight. Correlations were adjusted to represent within breed, sex and management group relationships. The purpose of the analysis was to study the relationships of carcass weight with carcass measurements and to identify carcass measurements that are independent other than through their relationships with carcass chemical fat concentration and carcass weight. The direct effect of live weight on all carcass measurements was positive. Thus, heavier carcasses with the same fat concentration had larger fat and tissue depths, muscle measurements, leg measurements and kidney fat weights. The results of correlations among the residuals suggest that fat depths C and J, specific gravity, muscle width A and kidney fat weight are nearly independent estimates of carcass composition in the sense that they are only correlated through their relationships with carcass weight and carcass fat composition. Robust predictors of carcass composition were developed by first adjusting carcass measurements for the direct effects of carcass weight and then computing regressions on the adjusted measurements. These predictors appeared to be better predictors of environmental and genetic differences than least-squares multiple regression yet reduced the accuracy of within group prediction only slightly.

Forty-five Large White × Landrace gilts were given food to realize energy intakes recommended by the Agricultural Research Council (1981) to attain maternal weight gains in pregnancy of either 40, 20 or 10 kg using a diet containing 125 g crude protein and 12·5 MJ digestible energy (DE) per kg over three parities. During a 3-week lactation period all animals were given a standard level of feeding. Maternal weight gains in pregnancy were much greater than those anticipated, for all treatments during each parity. The relationship between the actual and the predicted weight gains (kg) was the same for all three parities, actual AW = 22·62 + 0·71 predicted AW (R = 0·69). There was a large range of weight gains within treatments which was related to backfat thickness (P2 measurement (mm)) at conception in the second and third pregnancies, AW = 10·52 + 0·62 P2 measurement (R = 0·63) and to the change in P2 measurement, AW = 38·37 + 1·68 AP2 (R = 0·38) in the first pregnancy. The daily gain per MJ DE intake decreased wth parity and with decreasing energy intake. Numbers of piglets born and weaned were similar for all treatments; birth weights were also similar but there was an unexplained significant difference in piglet weaning weight in parity 2. There were no significant differences among treatments for either the total number or weights of piglets produced over the three parities.

In order to obtain a better knowledge of the behaviour of the domestic pig, a small population was established in 1978 near Edinburgh in an enclosure with several types of habitat, including woodland and bog. Over a 3·5-year period 13 different groups were studied with each group typically containing a boar, four sows, a young sub-adult boar and an immature gilt. The sow and her piglets were allowed to determine the time of weaning and, apart from providing food for maintenance and reproduction, handling was kept to a minimum. The behaviour of these pigs, which included most of the behaviour of the European wild boar, is described in a general manner for the non-specialist.

The effect on the reproductive performance of Greyface (Border Leicester × Scottish Blackface) ewes of a low level food intake and associated loss of live weight from either 14 days before mating, or from the time of mating, until 11 to 26 days after mating, was investigated. Ewes (252) were allocated to one of three treatments with ewes within each treatment divided into two flocks (flock A: 16 ewes per treatment; flock B: 68 ewes per treatment). Ewes of treatment LL were given a ration providing proportionately 0·5 estimated metabolizable energy (ME) requirements for maintenance from 2 weeks before mating. Those of treatment HL were given a daily ration providing 1·5 estimated ME requirements for maintenance until mating and the restricted ration thereafter. Ewes of treatment HH were given the higher ration throughout the experimental period. Flock A ewes were slaughtered at 11 days post mating and flock B ewes at between 18 and 26 days post mating. Treatment differences in the ovulation rates of flock A ewes were not statistically significant but in flock B, ewes of treatment LL had a lower mean ovulation rate (1·81) than those of treatments HL (2·23) and HH (2·09) (P < 0·001). The lower ovulation rate of LL ewes relative to HL ewes in flock B was reflected in a lower mean potential lambing rate per ewe pregnant than in the HL treatment (1·58 v. 1·79; P < 0·01) and per ewe put to the ram (1·37 v. 1·65; P < 0·01). HL ewes had a slightly lower mean potential lambing rate per ewe pregnant (1·79 v. 1·97; P < 01) and per ewe put to the ram (1·65 v. 1·82; P < 0·05) than HH ewes. Ova wastage rates of LL + HL and HH ewes were 0·26 and 014 (P < 001) respectively at 24 days post mating. Values for LL and HL ewes (0·27 and 0·25 respectively) were not significantly different.

Estimated mean conceptus lengths were 370, 500 and 1400 μin for LL, HL and HH ewes respectively (P < 0·05).

It is concluded that low food intake before mating reduced the mean ovulation rate and low intakes after mating compromised embryo growth rate and induced a higher rate of ova wastage; this increase in the incidence of ova wastage was not significantly exacerbated by the low levels of intake prior to mating.

Sodium bicarbonate had no effect on the dry-matter (DM) intake of heifers given a complete mixed diet of grass silage, molasses, barley, soya-bean meal and a mineral mix (660, 140, 100, 85 and 15 g/kg DM respectively) when it was incorporated into the mix at 20 and 40 g/kg DM or sprinkled on top of the diet at a rate of 350 g/day. In a second experiment, cows in mid lactation were given a complete mixed diet of silage, barley, soya-bean meal and minerals (660, 240, 85 and 15 g/kg DM) or the same diet with the barley replaced with molasses at 140 g/kg DM. Sodium bicarbonate was sprinkled on top of the diets at 0, 450 or 900 g/day. There were no significant effects on DM intake in the final week of each 3-week period. However, there was an apparent interaction of diet and sodium bicarbonate on the initial acceptance of the diet, with the intake of the diet in week 1 being significantly lower than the final intake with 900 g/day sodium bicarbonate in the absence but not in the presence of molasses.

In order to determine the relative digestibilities of nitrogen and amino acids in foodstuffs for pigs and poultry, and the effects of manufacturing methods, equal quantities of soya-bean meal, sunflower meals [hulled (sunflower meal 1) and dehulled (sunflower meal 2)], meat meals [made with (meat meal 1), and without (meat meal 2), blood added at 250 g/kg meat tissue (wet weights)] and rapeseed meals [seeds heated at 80°C (rapeseed meal 1) or 100°C (rapeseed meal 2)] were mixed with protein-free ingredients. The diets were given to five growing pigs with ileo-rectal anastomoses, and, by crop-intubation, to 12 caecectomized and 12 intact cocks. Excreta were collected over 48-h periods. Endogenous excretion was estimated by giving protein-free diets.

In the order, soya-bean meal, sunflower meals 1, and 2, meat meals 1, and 2, rapeseed meals 1, and 2, true digestibilities were: with pigs, of nitrogen, 0·81, 0·80, 0·79, 0·64, 0·79, 0·73, 0·70 (s.e.d. 0·030), of lysine, 0·84, 0·83, 0·84, 0·65, 0·84, 0·76, 0·72 (s.e.d. 0·032); with caecectomized birds, of nitrogen, 0·92, 0·91, 0·91, 0·66, 0·78, 0·74, 0·75 (s.e.d. 0·018), of lysine 0·92, 0·91, 0·93, 0·62, 0·79, 0·70, 0·70 (s.e.d. 0·020); with intact birds, values were similar to those with caecectomized birds for soya-bean, and the sunflower meals, but lesser for meat meals 1 and 2; the solubilities of nitrogen in pepsin were 0·96, 0·92, 0·93, 0·80, 0·89, 0·87, 0·87.

Two hundred and eighty pigs (initial live weights 10 kg) were used to compare growth response to free lysine with that to lysine in soya-bean meal and sunflower meal 2. Lysine availabilities, assessed by analyses of regressions of live-weight gain against lysine intake were 0·82 (s.e. 0·12) for soya-bean meal, and 0·82 (s.e. 0·18) for sunflower meal 2.

Amino acid digestibilities of the sunflower meals were similar to those of soya-bean meal, and were not influenced by dehulling; values for the rapeseed meals were lower, and unaffected by differences in heating severity; values for the meat meal were reduced by blood addition. Values differed between pigs and poultry, but there was consistency in the extent to which each species discriminated between some foodstuffs. The pepsin test was insensitive. The large standard errors associated with availability values prevented meaningful comparisons with digestibility values.

To gain approval for use in the revised European Community (EC) Pig Grading Scheme to be introduced in 1989, methods of estimating carcass lean proportion must be shown to do so with a coefficient of determination greater than 0·64 and a residual s.d. of less than 25 g/kg. A trial was carried out to assess a number of methods for use in the EC Scheme as applied in Great Britain. Subcutaneous fat and m. longissimus depths at the head of the last rib and at the third/fourth from last rib were measured using the optical probe (OP), the Fat-O-Meater (FOM), the Hennessy Grading Probe II (HGP) and the Destron PG-100 Probe (DST) on a broad sample of 162 commercial carcasses representative of the ranges in fatness and weight found nationally. The left side of each carcass was separated into component tissues. Although the instruments all achieved similar levels of accuracy in predicting carcass lean proportion, some differences were found. The DST just failed to reach the required statistical criteria for approval in the EC Scheme. The results for the other three instruments were submitted to Brussels as evidence of suitability and they have been approved.

Using the regression relationships found between carcass composition and fat thickness together with results from earlier studies, it was estimated that the carcass separable fat proportion of British slaughter pigs has fallen at the annual rate of 7 g/kg since 1975.

One hundred and two Large White × Landrace Fl hybrid sows were allocated over four parities in a factorial design to two levels of target P2 backfat thickness at parturition (20 mm, F v. 12 mm, T), two levels of lactation feeding {ad libitum, H v. 3 kg/day, L), and two sizes of sucking litter (six v. 10). Sows attained 13 mm P2 when first mated at 126 kg live weight. Fatness (P2, mm) at weaning was significantly influenced by target fatness at parturition (14·2 v. 9·3), lactation feeding level (13·7 v. 10·0), and litter size (12·7 v. 11·0). Changes in backfat (P2, mm) during 28-day lactation were significantly influenced by target fatness at parturition (—5·0 v. —2·5), lactation feeding (-2 0 v. —5·4), and litter size (—2·9 v. -4·6). Sow live weight (kg) at weaning was significantly influenced by target fatness at parturition (211 v. 192), lactation feeding (218 v. 186), and litter size (208 v. 196). Changes in live weight (kg) during 28-day lactation were significantly influenced by target fatness at parturition (—26 v. — 12), lactation feeding (—5 v. —31), and litter size (—12 v. —25). With multiparous sows only, total food intake during 28-day lactation was negatively related to total food intake in pregnancy. Change in backfat (P2, mm) during 28-day lactation = -0·28 - 0·27 P2 at parturition + 0·04 lactation food intake — 0·50 litter size. Change in live weight (kg) during 28-day lactation = -3·8 — 0·15 live weight post partum + 0·36 lactation food intake — 3·3 litter size. Sows with target fat levels of 20 mm P2 at parturition had better food conversion efficiencies than sows with target fat levels of 12 mm. Target fatness at parturition, and especially lactation food intake, but not litter size, significantly influenced the interval (days) from weaning to oestrus in parity 1 (9·1 v. 14·2 and 7·8 v. 15·3, but 11·6 v. 11·5), while n i subsequent parities only litter size influenced the interval (days) from weaning to oestrus (6·0 v. 8·0). Birth weight (kg) of piglets was influenced only marginally by target fatness at parturition (1·4 v. 1·2) in parity 1, and not by the other factors, or in subsequent parities. Piglet growth rate was affected by both target fatness at parturition and litter size, but by lactation feeding level only in the last week of lactation. The relationship between fatness at weaning (mm) and the weaning to oestrus interval (days) for primiparous sows can be expressed as 26·6 — 1·28 P2. High level feeding in lactation imparted production and efficiency benefit in both primiparous and multiparous sows, while pregnancy feeding to a target of 20 mm rather than 12 mm at parturition was of benefit for primiparous sows.

Sixty Large White ♂ × (Large White ♂ × Landrace ♀) pre-pubertal gilts were allocated at random to one of five treatments. Gilts on treatment A were given oestradiol benzoate (OB) at 160 days of age. They were also given allyl-trenbolone (AT) at 166 days of age for 18 days followed by an injection of gonadotrophins (Gn) at 184 days of age. Gilts on treatment B were given OB and AT, but not Gn. Gilts on treatment C were given OB and Gn, but not AT. Gilts on treatment D were given OB only and gilts on treatment E were given Gn only. Gilts which were in heat after 183 days of age were artificially inseminated twice during the first 2 days of oestrus. All gilts were slaughtered either 20 days after insemination or at 220 days of age if they were still anoestrus.

The percentages of gilts ovulating after Gn injection were 36% (4/11), 91·7% (11/12) and 91·7% (11/12) for treatment groups A, C and E respectively (P < 0·01). Gilts on treatments A, C and E were inseminated at a significantly younger age than those on treatments B and D (P < 0·05). No significant differences were found in ovulation rate or embryo survival between treatments.

The results indicated that the administration of AT prior to Gn injection had an adverse effect on both the percentage of gilts ovulating and the development of embryos.

The physical and chemical composition of sows was determined at first mating (no. = 6), weaning the first litter (12) and 14 days after weaning the fourth litter (24). The sows were from 108 Large White/Landrace Fl hybrid gilts allocated in a factorial arrangement according to two levels of subcutaneous fatness at parturition (12 v. 22 mm P2), two levels of lactation feeding (3 v. 7 kg) and two sizes of sucking litter (six v. 10). Treatments significantly influenced the composition of dissected carcass fat and chemical lipid, but not composition of dissected lean and chemical protein. The final body protein mass of well fed sows at the termination of parity 4 was 41 kg, and the total content of gross energy (GE) in excess of 3000 MJ, with an average of 12·4 MJ GE per kg live weight; equivalent values for the less well fed sows were 33 kg and 9·4 MJ GE per kg live weight respectively. The weights of chemical lipid and protein could be predicted from the equations: lipid (kg) = -20·4 (s.e. 4·5) + 0·21 (s.e. 0·02) live weight + 1·5 (s.e. 0·2) P2; protein (kg) = -2·3 (s.e. 1·6) + 0·19 (s.e. 0·01) live weight - 0·22 (s.e. 0·07) P2. On average, sows lost 9 kg lipid and 3 kg protein in the course of the 28-day lactation; these being proportionately about 0·16 and 0·37 of the live-weight losses respectively. Maternal energy requirement for maintenance was estimated as 0·50 MJ digestible energy (DE) per kg M0·75, while the efficiency of use of DE for energy retention was 0·28.

An evaluation of three automatic recording probes, the Fat-o-Meater (FOM), the Hennessy Grading Probe II (HGP) and the Destron PG-100 (DST) was carried out for use in the revised European Community (EC) Pig Grading Scheme. One hundred and forty-five pig carcasses were selected from four abattoirs covering the national fatness distribution. Two fat thickness depths, one at the head of the last rib (LR) and the other at the 3rd/4th from the last rib (3/4LR fat), and one muscle depth (3/4LR muscle) taken in the same operation for recording 34LR fat were studied as predictors of EC reference lean concentration. All measurements were taken 60 mm from the dorsal mid line. The corresponding cut surface measurements were also recorded and the carcasses were dissected. The prediction of cut surface fat depths from fat depth probes was better than the prediction of cut surface muscle depth from muscle depth taken with the probes. The DST fat measurement predicted more accurately the corresponding cut surface measurements and FOM muscle depth was more precise in predicting muscle cut surface depth. The DST was better in the prediction of EC reference lean concentration with 3/4LR fat and 3/4LR muscle as predictors (residual s.d. 23·1 g/kg). By adding LR as a third independent variable FOM predicted slightly better the lean concentration (residual s.d. 22·3). For Spain, the equations with these three independent variables were submitted to the Pig Management Committee of the EC. All the methods tested predicted EC reference lean concentration with a residual s.d. less than 25 g/kg and a correlation higher than 0·8.

Operant conditioning was used to measure the effect on the feeding motivation (hunger) of pigs of diluting nutrient restricted food allowances with straw. Twelve Large White × Landrace boars were maintained in individual pens where they received their daily food allowance. Prior to the experiment, the boars were conditioned in separate rooms to press a panel so as to receive small rewards of food. The effect of diluting meal with straw on panel pressing was investigated in two trials. In trial 1, the boars were allocated to the following treatments: high (H) (3·5 of maintenance (A/)), low (L) (1·5 M) and low/straw (LS) (1·5 M + 0·15 times the dry weight of meal as chopped straw). This dilution increased the food volume by proportionately 0·29. Operant response rates were measured in six 1-h tests in each of two periods at the start (days 3 to 10, period 1) and at the end (days 20 to 28, period 2) of the 28-day experiment. In trial 2, nine of the above boars were allocated to the following treatments: high (H) (3·0 A/), low (L) (1·5 M) and low/straw (LS) (1·5 M + 0·30 the dry weight of meal as ground straw). This dilution increased the food volume by proportionately 0·75. Operant response rates were measured as above between days 10 to 17, following a 9-day adjustment period to the new regimes.

In both trials, operant response rate was strongly affected by treatment. Overall in trial 1, animals on the H treatment made few responses (mean 60 responses per session), animals on the L treatment made significantly more responses (mean 825, P < 0·001) and animals on the LS teatment significantly more responses yet again (1263, P < 0·05). This last difference was associated with the difficulty of the LS animals consuming all of the diluted diet during period 1. In trial 2, response rates were again higher on the L than on the H treatments. There was, however, no difference between the L and LS treatments (means: 60 v. 1035 v. 1200). Proportionately only 0·04 of the diet was refused during the period of testing.

The present results show that short-term satiety arising from gut distension does not reduce the feeding motivation of animals on chronic nutrient restriction. This suggests that hunger will remain high i n pigs on restricted food allowances, even when they have access to high fibre foods. This hunger will be a potential source of stress, particularly in housing systems involving physical restraint such as tether stalls.

The level of body reserves in first-litter sows was manipulated by giving gilts one of three levels (high (H), medium (M) or low (L)) of food from selection (44 kg live weight) to parturition. The aim of this experiment was either to maintain or to mobilize these reserves during lactation (31·4 days) by feeding sows to appetite (high (H)) or 2·0 kg/day (low (L)).

When the level of body reserves was increased prior to farrowing (171 kg live weight, 32 mm backfat) sows had a lower voluntary food intake during lactation than those animals that farrowed with a low level of body reserves (126 kg live weight, 20 mm backfat) (H-H v. L-H, 3·4 v. 4·9 kg/day; P < 0·001). Both groups had a normal return to oestrous activity after weaning (mean interval between weaning and mating of 14 days) but the heavier animals mobilized more of their body reserves (H-H −30·7 kg live weight, -4·3 mm backfat; L-H -3·6 kg live weight +0·9 mm backfat; P < 0·001). When food intake during lactation was restricted to 2·0 kg/day the interval between weaning and mating was increased by 50% regardless of the level of body reserves present at farrowing. For the same animals, there were insufficient body reserves to support milk production at the same level as for those animals given food t o appetite.

The influence of four diets and two remating intervals (1 or 9 days after parturition) on several milk and production traits was studied in 73 lactations of 46 Californian C? × New Zealand $ does. Three diets were formulated to provide increasing levels of fibre concentration (180, 202 and 238 g acid-detergent fibre per kg dry matter (DM)); a fourth diet contained added pork lard (35 g/kg) at the lowest level of fibre. The energy: protein ratio was maintained between 72 and 84 kj digestible energy (DE) per g digestible protein.

The DE intake increased significantly when fat was included in the diet but was not affected by dietary fibre concentration. An increase in the DE content of the diet tended to decrease food conversion ratio at a mean rate of 0·16 kg/kg per MJ/kg DE. Fat addition also improved milk yield, litter weight at 21 days and survival index, mainly when litter size was higher than nine pups born alive. Neither live-weight gain nor prolificacy of does were affected by any of the variables studied.

The type of diet did not affect milk DM, crude protein, fat and energy concentrations, the mean values being 287·8, 116·1, 134·2 g/kg and 27·73 MJ/kg, respectively. The proportions of short- and medium-chain fatty acids in milk fat were not affected by type of diet. The effect of fat addition on milk fat composition was limited to the long-chain fatty acids, mainly C18: 0 and C18: 1. These changes in addition to differences in milk intake could also affect the survival index of pups.

Does remated 1 day after parturition showed a lower total milk yield than those remated 8 days later, the decrease being more apparent at the end of lactation. Remating interval did not affect the other variables studied.