Duroc and halothane negative British Landrace boars and gilts were performance tested on ad libitum or restricted feeding regimes, with like-sexed non-littermate groups of one, two, three or four pigs per pen. There was a total of 320 pigs with 20 litter groups per breed with four boars and four gilts per litter group. Within each feeding regime, a boar and a gilt from each litter were tested on one of two diets in 1986, for each of the four combinations, and pigs were tested similarly for two other diets in 1987. Carcass composition was determined by half-carcass dissection of 160 pigs allocated between treatments.

There was a breed × sex interaction for growth and performance traits for pigs fed ad libitum. Duroc boars were faster growing and more efficient than Landrace boars, but Duroc gilts grew more slowly and were less efficient than Landrace gilts. On restricted feeding, Duroc pigs were more efficient than Landrace pigs.

At constant slaughter weight, Duroc pigs had less subcutaneous fat but more intermuscular fat. Although they had less separable fat in the carcass, Duroc pigs were not leaner as weights of bone, skin, head, feet and tail were heavier than for Landrace pigs.

Group penning and group feeding of pigs may have enhanced competition effects resulting in positive genetic and phenotypic correlations between growth rate and backfat depths on both feeding regimes.

The positive genetic correlation between growth rate and fat deposition resulted in a negative genetic correlation between growth rate and carcass lean content and a lower genetic correlation with lean tissue growth rate than in other studies.

Work in the United States of America has shown that dietary supplements of nickel (Ni) can result in an increase in rumen urease activity and can increase growth rate and food conversion efficiency in lambs and steers given low protein diets. It has been suggested that Ni enhances urea recycling through its effect on urease activity. To examine this hypothesis, four sheep were given a high-energy, lowprotein diet with or without a supplement of 5 mg/day Ni, given as NiCl2.6H2O by continuous infusion into the rumen. Urea irreversible loss rate (ILR) and pool size were measured by means of a single intravenous injection of 14C-urea. The addition of Ni resulted in a significant increase in rumen urease activity (P < 0·05) but there was no significant effect on urea ILR, urea pool size, urinary urea excretion or on the quantity of urea recycled to the gastro-intestinal tract. Ni also had no effect on plasma urea or rumen ammonia concentrations, on diet digestibility or on nitrogen retention. It is concluded that the enhancement of urease activity by supplementary Ni conferred no nutritional advantage to the sheep.

Six diets based on maize and soya-bean meal were prepared. The basal diet had a crude protein (CP) concentration of 171 g/kg. The same ingredients, together with maize starch, were used to give a diet with CP 131 g/kg. This diet was supplemented with all (positive control) or with three of the four amino acids lysine, threonine, tryptophan and methionine. Each diet was given at two rates of intake. From the results, the optimum ratio between these four amino acids at different planes of intake was calculated. Amino acid digestibility in the basal diet was measured at three intakes, using pigs fitted with T cannulas at the terminal ileum.

The results showed that the optimum ratios between the four amino acids (expressed in terms of digestible amino acids) were not affected by the rate of food intake. The optimum ratio between the four amino acids (i.e. when they are equally limiting) was lysine 1·00, methionine + cystine 0-61, threonine 0·64 and tryptophan 0·20. Digestibility was not affected by the level of intake.

Two fats, soya-bean oil and tallow, were blended in the ratios 70: 30, 50: 50 and 30: 70. The ratios of unsaturated to saturated fatty acids (U/S) of the blends were 3·18, 2·08 and 1·49 respectively; values for soya-bean oil and tallow were 6·69 and 0·93. These five fat sources were each included into a basal diet at levels of 40, 80 and 120 g/kg. The digestible (DE) and metabolizable (ME) energy together with the apparent fat digestibility (AFD) of the experimental diets were measured in a metabolism trial based upon four 4 × 4 Latin squares using 16 gilts of 30 kg initial live weight. Linear equations relating dietary DE and ME values to level of inclusion of fat were extrapolated to 1000 g/kg to obtain values for the fats. DE values for soya-bean oil and tallow were 38·06 and 34·16 MJ/kg respectively. Corresponding data for ME were 35·63 and 32·53 respectively. These figures were used to calculate values of the mixtures. Data thus derived did not differ significantly from those determined directly, indicating that there was no synergism between the two fats. DE values of fats determined as the product of AFD of fats and their gross energy followed similar trends. The majority of the increase in values of fats was associated with a change in the U/S ratio from 0·93 to 2·08.

From each of 159 litters, between one and three pigs were fed ad libitum and between one and four pigs were fed at several restricted feeding levels from about 27 to 107 kg live weight. Effects of litter by feeding regimen (ad libitumv. restricted feeding) interactions (L × F) and sex by feeding regimen interactions (S × F) on production traits were investigated. In experimental groups where restrictedly fed animals received an amount of food based on their estimated voluntary food intake capacity (FIC), interactions were non-significant. In groups where restricted feeding was independent of FIC, significant L × F or S × F interactions were found for daily food intake (FI), daily gain, lean tissue growth rate and fatty tissue growth rate, but not for body composition and food conversion traits.

Because of between-animal variation in FIC, restricted feeding according to a fixed scale restricted intake of some animals to a higher degree than others and degree of food intake restriction (DFR) was calculated from actual FI and FIC for animals fed at a restricted level. After correction of FI and production traits of restrictedly fed animals for differences in DFR, L × F and S × F interactions were not significant.

It was concluded that the poor relationships often found between test-station results of boars and results of their progeny in practical environments may be caused, to an important extent, by differences in DFR in each environment. To overcome these genotype by environment interactions it is recommended that animals be fed ad libitum in both test and commercial environments.

The non-linear model y = ae(−hW−c/W) was fitted to weekly calculated daily gain (DG), daily food intake (FI) and food efficiency (FE) of 653 barrows and gilts fed ad libitum or restrictedly during a growing period from 27 to 108 kg live weight. Where y was DG, FI or FE, W was live weight and a, b and c were parameters. The model fitted well to the expected course of the traits, with an accuracy similar to that of quadratic polynomials. Parameters for one trait could simply be derived from the parameters for the other two traits. For each trait, four basic patterns were distinguished, depending on the signs of b and c. Curves with a maximum (b > 0 and c > 0) occurred most frequently. In cases of curves with a maximum, the model could be reparameterized to a model with parameters having a simple biological meaning.

Coefficients of determination in barrows averaged 0·29 for DG, 0·88 for FI and 0·45 for FE, whereas these values were somewhat lower in gilts. With ad libitum feeding, a DG curve with a maximum was fitted in proportionately 0·83 of the barrows and 0·61 of the gilts. The maximum DG was on average at live weights of 64 kg for barrows and 77 kg for gilts. A maximum in the FI curve was predicted in proportionately 0·60 of the barrows and 0·39 of the gilts. Curves for DG and FI in gilts were less curvilinear than in barrows. FE curves, with ad libitum feeding, had a maximum in proportionately 0·59 of the barrows and 0·52 of the gilts. This predicted maximum FE was, on average, before the start of the growing period. Gilts had a higher FE than barrows from 35 kg body weight onwards, and the difference increased with increasing live weight. Differences in FE between ad libitum and restricted feeding were small, with a tendency for animals fed at a restricted feeding level to be more efficient at the end of the growing period.

Average FE curves and individual FI or DG curves were used for indirect prediction of individual DG or FI curves, respectively. The correlation between directly and indirectly predicted values of DG and FI at live weights of 30, 65 or 100 kg was about 0·7 in ad libitum fed barrows and gilts, and greater than 0·8 in pigs fed at a restricted level. This indicates that the model is suitable to predict and control the course of individual daily gain by influencing the course of food intake.

In a consumer trial the assessments of 874 cooks and 5034 family members were analysed. Forty-one boar and 40 barrow carcasses were selected in a commercial abattoir so that the two sexes were similar in carcass weight, fat thickness and muscle pH. A boar sample including a higher proportion of tainted carcasses was selected. It was divided into three boar taint-level subgroups according to their 5a-androst- 16-ene-3-one (androstenone) concentration in fat (Jig androstenone per g fat) as follows: L < 0·5 (no. = 17), M 0·5 to 1·0 (no. = 13) and H > 1·0 (no. = 11). From each carcass, loin/rib chops were prepared and cooked hams, brine-cured bellies and Spanish dry-cured hams were processed. An analysis of variance was used to estimate the effects of sex and boar taint levels. Cooks (P < 0·05) and family members (P < 0·01) reported a higher level of odour for boar chops. A higher level of unfavourable responses to odour and flavour were found in the H taint-level subgroup. Also, the H taint-level group produced the highest proportion of negative judgements on overall acceptability in comparison with normal purchases. The response of cooks to odour from brine-cured bellies was significantly affected by sex (boar and barrow). For bellies, odour, overall acceptability and comparison with normal purchases were significantly affected by the boar taint-level subgroups (P < 005). The treatments had no significant effect on any quality question related to boar taint in cooked ham. However, boar taint level significantly affected the assessments of flavour and overall acceptability from Spanish dry-cured ham (P < 0·01). A higher proportion of negative responses was found in the H taint-level subgroup. The trial indicates that boar meat can produce an unfavourable response from consumers for fresh meat (chops) or products needing heating prior to consumption (brine-cured bellies). However, in cooked products with hot processing and cold consumption (cooked ham) no negative effect from using boar meat was observed. To produce Spanish dry-cured ham, androstenone quantification should be carried out to avoid consumer dissatisfaction.

Two hundred and thirty-nine pigs reared at the Meat and Livestock Commission's Stotfold Pig Development Unit and derived from the four major breeding companies in the UK were slaughtered at 63 kg live weight in an experiment which examined the effect of genotype (Meat-line or White-line), pre-slaughter transport time (1 or 4 h) and lairage time (2 or 21 h) on carcass and meat quality. The pre-slaughter handling was chosen to simulate good commercial procedures and cover the range of transport and lairage times probably experienced by a large proportion of British slaughter pigs. Meatline pigs had higher killing-out proportions and heavier carcasses, with increased cross-sectional area of the m. longissimus dorsi. Backfat thickness was similar in the two genotypes. White-line pigs had heavier livers and produced meat which potentially had a lower incidence of PSE. Longer transport time increased live-weight loss. It reduced carcass yield in the White-line but not in the Meat-line pigs. Transport had no major effects on meat quality. Longer lairage, during which the pigs were fed in compliance with the law, resulted in reduced carcass yield but increased liver weight and allowed some repletion of liver glycogen. It also reduced ultimate pH values in the m. semimembranosus and m. adductor. There were no important or consistent differences in the way pigs of the two genotypes responded to pre-slaughter handling.

Experiments involving both digestion and growth trials were undertaken to compare the responses of pigs to two increments of digested energy resulting either from gut fermentation or from digestion by endogenous enzymes in the small intestine. Unmolassed sugar-beet pulp (SBP) and maize starch (MS) were selected as model materials for these two systems. A control diet was formulated to fulfil the needs of pigs for all essential nutrients apart from energy. This diet was offered according to a scale set at about twice the maintenance energy requirement. The two SBP diets contained 150 and 300 g SBP per kg (SBP15 and SBP30) and the two MS diets 100 and 200 g MS per kg (MS10 and MS20). Sixty observations were made with 10 female and 20 male growing pigs to provide information on digestion. The results showed that the energy in SBP and MS had an apparent digestibility of 0·74 and 0·98 respectively (s.e.d. 0025). The neutral-detergent fibre fraction of SBP had a digestibility of 0·81 (s.e. 0·055). Forty pigs (20 male and 20 female) were involved in the growth trial. The responses of pigs to increments of different digestible energy (DE) were measured in terms of daily carcass-weight gain. The results gave values of 435, 478, 527, 511 and 567 (s.e.d. 17·3) g/day for the control, SBP15, SBP30, MS 10 and MS20 treatments respectively. These results suggest that the apparent DE of SBP is used for carcass growth with an efficiency of 0·57 (s.e. 0·012) relative to the DE from MS.

Infectious atrophic rhinitis is a disease of the upper respiratory tract of pigs, characterized in the live animal by deformation of the snout and conchal atrophy. However, the severity of the disease in pigs on commercial units is highly variable and air quality may be implicated as a significant factor in addition to the recognized pathogens. In this study the aerial environment was monitored in 49 pig buildings on 12 commercial farrowing-finishing units. A total of 1117 pigs from the 12 farms were examined individually at commercial slaughter weight to quantify the severity of conchal atrophy, using snout scoring and morphometric techniques.

A number of significant relationships were shown between environmental variables in the farrowing house and the severity of conchal atrophy. Mean snout score (MSS) and the percentage of snouts from each herd sample with a score of three or more (SS3) were correlated with total bacterial counts (r = 0·78 (P < 0·01) and 0-83 (P < 0·01) respectively), counts of 10 [mi to >15 urn particles (r = 0·67 (P <0·05), 0·73 (P <0·05)) and concentrations of gravimetric dust (r = 0·65 (P <0·05), 0·64 (P <0·05)). Concentrations of ammonia were correlated with SS3 (r = 0·68 (P <0·05)).

Dust in the first-stage weaner houses was again a significant component of the aerial environment associated with the severity of the disease. MSS and SS3 were correlated with counts of 10 urn to >15 μm particles (r = 0·66 (P <0·05), 0·68 (P <0·05)), concentrations of respirable dust (r = 0·67 (P <0·05), 0·63 (P <0·05)), total dust (r = 0·75 (P <0·05), 0·87 (P <0·001)), and gravimetric dust (r = 0·83 (P <0·01), 0·88 (P <0·001)). The results support the theory that the mass or number of particles present as inspirable aerosols, and the presence of large numbers of viable bacteria may compromise the local defence mechanism of the upper respiratory tract in the pig and facilitate colonization by Bordetella bronchiseptica and Pasteurella multocida. Saturation deficit in the second-stage weaner houses was correlated with both mean morphometric index and SS3 (r = 0·860 (P <0·01) and 0·683 (P <0·05) respectively), and volumetric stocking density in the finishing houses was correlated with both MSS and SS3 (r = -0·84 (P <0·01), -0·64 (P <0·05)). It is hypothesized that the severity of the disease may be lessened by reducing the concentrations of dust, microbes and ammonia which may play a significant role in the development of the disease.

The effect of monosodium L glutamate (MSG) on diet palatability and piglet performance during the suckling and weaning periods was studied in the course of five successive experiments involving a total of 230 litters during the suckling period and 120 pens of seven piglets during the post-weaning period. During the suckling period, the addition of 5 g MSG per kg diet led to a significant 0·36 proportional increase of creep food intake from the 18th day post farrowing. However, no increase in weaning weight was observed subsequent to the intake of the diet with added MSG. Moreover, in an experiment where MSG was added with an associated commercial flavour, no flavour enhancing effect of MSG was detectable. Few health problems were encountered at weaning and the number of scouring piglets was not related to one particular diet. During the first 13 days after weaning the addition of MSG to the diet increased daily food intake by proportionately 0·1 (P < 0·01) as well as growth rate by proportionately 0·07 (P < 0·01). Moreover, the addition of MSG to the diet was more effective with piglets of low weaning weight and thus contradicted the classical relationship between post-weaning performance and weaning weight. Finally, in an experiment where weaning occurred at lower ambient temperature, no improvement of post-weaning performance was observed following the addition of MSG.

In comparative digestibility trials with growing pigs Latin squares are widely used as experimental designs. In this paper conditions for the application of Latin squares are explicitly stated and checked with real data. Data were collected at the Institute for Livestock Feeding and Nutrition Research in the Netherlands and consisted of digestibility trials run on pigs of 40 to 100 kg live weight. There is strong evidence for a certain form of period × animal interaction in the data. This may seriously affect estimates of treatment effects and results of significance tests. It is concluded that Latin squares are unsuitable for comparative digestibility trials with pigs growing from 40 to 100 kg. When there is no interest in statistical comparison of the diets under study, Latin squares can still be used. Some suggestions for alternative designs are given.

Rapeseed, sunflower and soya-bean meals were compared as the main sources of protein in concentrate supplements given to dairy cattle. The supplements contained (per kg) 620 g rapeseed meal, 760 g sunflower meal or 500 g soya-bean meal and all three were formulated to contain 300 g protein per kg. Each animal was given daily TO kg dairy compound, 3·5 kg supplement, 3·5 kg sugar-beet pulp pellets and offered maize silage ad libitum. A randomized-block design with 39 cattle was used and treatments were applied for 16 weeks. All three supplements were eaten rapidly and there were no refusals. Daily mean milk yields were rapeseed 26·7, sunflower 25·3 and soya bean 25·1 (s.e.d. 1·44) kg; milk fat and protein concentrations were not affected by the treatments. There were no significant treatment differences in live weight and condition score. It was concluded that these high protein supplements based on rapeseed meal, sunflower meal and soya-bean meal were of equal feeding value for milk production.

The proportions of abdominal fat and total body lipid and protein were measured up to 30 weeks in males and 21 weeks in females from lines of lean and fat broiler chickens given diets of different protein content. There was a constant relationship between the proportions of abdominal fat and body lipid independent of line, diet or age. Data on males showed effects of line and diet on body fatness at all ages up to 30 weeks. In females, line and diet had effects on body fatness during early growth but little effect on composition at 21 weeks. Plasma very low density lipoprotein concentration was higher in the fat line in both sexes at all ages. Egg production over the first few weeks of the laying period was much higher in lean line hens.

A study was carried out on data collected between 1970 and 1979 on the crossbreeding of cattle in Vom using British Friesian, Brown Swiss and Jersey bulls. Only crossbreeding involving Friesian bulls was successful. There were progressive increases in lactation yield, yield per day of lactation length, lactation length, daily fat yield, birth weight and calving interval in the grades with increases in the Friesian contribution. The daily fat concentration however decreased with the increase in Friesian proportion. Most of the genotypes namely, pure White Fulani, 0·5 Friesian: 0·5 White Fulani; 0·75 Friesian: 0·25 White Fulani, 0·875 Friesian: 0·125 White Fulani and pure Friesian calved regularly each year. Phenotype correlations between lactation length and yield for most of the genotypes were high, positive and significant.

Priming with a progestagen-impregnated vaginal pessary followed by an injection of 750 i.u. pregnant mare serum gonadotropin at pessary withdrawal was used to induce oestrus and ovulation during anoestrus (13 June, latitude 57°N) in 58 Border Leicester × Scottish Blackface ewes that had lambed previously in late March/early April. At 54 to 58 h after pessary withdrawal the uterus of each ewe was viewed by laparoscopy and 50 × 106 viable sperm deposited into each uterine horn. Mean ovulation rate was 2·9 (s.d. 0·12; range 1 to 5). Plasma progesterone concentrations remained >1·5 μg/l in 54 (93%) of the ewes until at least day 21 after insemination implying a high fertilization rate. After allowing for three ewes that were observed to abort between 39 and 55 days after insemination and another three, carrying nine normally developed lambs, that died between 102 and 136 days of gestation, 40 of the remaining 48 ewes (i.e. 69% of the original 58) produced 76 viable lambs in early November. These conception and lambing rates obtained following the intrauterine insemination of 100× 106 viable sperm per ewe are more than double those obtained following natural mating or conventional cervical insemination with four times the number of viable sperm and imply that intrauterine insemination may enhance lamb production from ewes induced to breed during seasonal anoestrus.

The response of pigs to supplemental biotin (500 μg/kg diet) was studied in a growth trial from 15 to 88 kg live weight. Food: gain ratio was significantly improved during the grower phase and there was a tendency for improvement in the starter and finisher phases. There was also a tendency towards improved carcass grading.