Genetic and phenotypic parameters and correlated responses in performance test traits were estimated for populations of Large White (LW) and British Landrace (LR) pigs tested in Edinburgh and Wye respectively, to four generations of divergent selection for lean growth rate (LGA), lean food conversion (LFC) and daily food intake (DFI) with ad-libitum feeding.

There were differences between the two populations in genetic parameters, as LW heritabilities for growth rate, daily food intake and backfat depths were higher and the correlation between growth rate and backfat was positive for LW, but negative for LR. However, heritabilities, genetic and phenotypic correlations were generally comparable between selection groups, within each population. Genetic and phenotypic correlations indicated that animals with high daily food intakes were faster growing, had positive residual food intakes (RFI), were fatter with higher food conversion ratios. RFI was highly correlated with daily food intake and food conversion ratio, but phenotypically independent of growth rate and backfat, as expected.

Selection for LGA, in LW and LR populations, increased growth rate (54 and 101 g/day), but reduced backfat (−3·9 and −2·0 mm), food conversion ratio (−0·23 and −0·25) and total food intake (−11·8 and −12·6 kg). There was no change in daily food intake in LW pigs (−19 g/day), but daily food intake increased in the LR pigs (69 g/day). With selection for LFC in LW and LR populations, there was no response in groivth rate (9 and 9 g/day), but backfat (−4·1 and −2·1 mm), total (−6·6 and −11·8 kg) and daily food intake (−90 and −172 g) were reduced, as animals had lower food conversion ratios (−0·13 and −0·22). LW and LR pigs selected for DFI ate more food in total (6·8 and 5·9 kg) and on a daily basis (314 and 230 g), grew faster (94 and 51 g/day) and had higher food conversion ratios (0·12 and 0·13). Backfat was increased in LW pigs (3·7 mm), but not in the LR population.

In general, efficiency of lean growth was improved by increasing groivth rate, with little change in daily food intake from selection for LGA, but was primarily due to reduced daily food intake with selection on LFC.

In 56 balance trials sows received diets in pregnancy containing (g/kg diet) either 24·7 nitrogen (N) (C) or 16·7 N (L) followed by diets in lactation containing (g/kg dietary dry matter) either 28·5 N and 8·4 lysine (C) or 32·8 N and 10·3 lysine (H). N and energy balance during lactation (day 4 to 25) were made during three successive parities (23, 17 and 16 sows in parities 1,2 and 3, respectively). Retention in piglets was calculated from their body composition at weaning.

Mean daily litter gain was 2·72 kg/day and was not affected by the dietary treatments. Mean body-weight loss of sows was 0·67 kg/day and was lower only in parity 2 on lactation treatment H compared with lactation treatment C. N retention was less negative on lactation treatment H than on lactation treatment C (significant in parity 1) and N retention was less negative on pregnancy treatment L than on pregnancy treatment C (significant in parity 3). Fat mobilization on lactation treatment H was higher than on lactation treatment C (significant in parities 2 and 3). The proportion of energy mobilized as protein to the total energy mobilization was significantly lower on lactation treatment H compared with lactation treatment C. Estimated daily N, lysine and Heal digestible lysine requirements for first parity lactating sows were 162 g, 48 g and 37 g respectively. For second parity sows 179 g, 54 g and 42 g and for third parity sows 185 g, 56 g and 43 g. N excretion during lactation was proportionately about 0·6 of ingested N. This resulted in an N excretion of about 2·3 kg N during a 25-day lactation period. After correction for differences in litter size, body weight of sows, daily litter gain and N mobilization increased with parity number.

To reduce nitrogen excretion (NEx) the effect of nitrogen supply on nitrogen retention (NR) and NEx was studied in pregnant sows during three parities. A nitrogen supply of 40 g/day (treatment L) was compared with 62 g/day (treatment C) during day 0 to 85 of pregnancy. In the last month of pregnancy nitrogen supply on treatment L was 50 g/day and on treatment C 74 g/day. Faecal digestible lysine supply followed the same pattern as nitrogen. Nitrogen and energy balances were measured during mid pregnancy (day 50 to 60; no. = 22) and late pregnancy (day 105 to 112; no. = 60). During mid pregnancy treatments had a minor affect on NR and energy metabolism. NEx on treatment L was proportionately about 0·40 lower than on treatment C. During late pregnancy NR was lower on treatment L than on treatment C. NEx on treatment L was proportionately reduced by 0·35 compared with treatment C. In parity 1 the lower NR on treatment L was compensated by a higher fat gain. Results indicate that nitrogen and faecal digestible lysine supply on treatment L were close to minimal requirement in late pregnancy. Assumed values for maintenance requirement of nitrogen (0·45 g N per kg M0·75) and efficiency of ingested nitrogen to NR (0·6) were in line with the results of the balance trials. The observed nitrogen retention of sows, especially during mid pregnancy, permits a reduced nitrogen supply to reduce NEx.

Two similar style experiments were carried out in a climate-controlled pig house to determine the effects of adverse climatic conditions and relocating and mixing on the health status and productivity of pigs. In both experiments, 120 pigs were used. The climate-controlled pig house consisted of two fully separated but identical rooms (experimental and control) with five pens each (12 pigs per pen). Pigs exposed to draught and low environmental temperature had lower daily gain (experiment 1: 45 g/day; experiment 2: 25 g/day) and higher food conversion (food: gain ratio) than pigs housed under optimal climatic conditions (control). Moreover, clinical disease signs (i.e. diarrhoea, coughing, sneezing and haemorrhagic ear lesions) were more pronounced in the experimental than in the control group. In experiment 1, pigs were relocated and mixed at 10 weeks of age either within or between the experimental and control room. Data showed clear negative effects on daily gain and clinical disease signs especially among pigs that were relocated to suboptimal climatic conditions. In experiment 2, pigs were either relocated and mixed between both rooms or they remained in their own pens. Data on daily gain and clinical disease signs revealed that the health of the pigs was strongly affected by mixing. Therefore, the present work emphasizes the importance of climatic environment and social factors in intensive pig production.

Various procedures for estimating the economic values required to weight characteristics in multitrait selection have been proposed. Some, despite their theoretically sound foundations, are frequently misinterpreted. One such method involves the derivation of economic values based upon accepted economic theories of the firm, profit maximization, and the concepts of marginal economic behaviour. An amplified and more rigorous presentation of this method and its theoretical basis is presented that confirms the basic propriety of the method, clarifies the misinterpretations surrounding its application, and offers additional insights into the potential fallacy of less economically rigorous alternatives.

We propose a new method for determining age in mullet fishes taking the thoracic spines as material of analysis. The relations length-age and tueight-age were evaluated by von Bertalanffy and logarithmic regressions. Both methods closely agreed with the observed data but the von Bertalanffy's model showed the best R2 values in both species. Two parameters related to growth speed; the K coefficient of von Bertalanffy's model and the slope of logarithmic regression, were higher in Liza ramada than in Liza saliens. However, our results show that mullet have both high rates of size-growth and weight-production, in comparison with other marine fishes.

An experiment was carried out in Egypt using Giza White rabbits to investigate their lactational performance and to estimate the repeatabilities of milk yield and other litter traits. Data on 325 litters from 115 does fathered by 40 sires were used. Lactation traits involved milk yields during the first 7 days, 21 days and 35 days. Litter traits included litter size and weight at birth, number born alive, litter weight and gain at 21 days, litter size and weight at weaning and pre-weaning litter gain. Linear mixed models were used for analysing such data.

Phenotypic variation in milk yield was relatively high during the first 7 days, and decreased thereafter with advance of lactation stage. Year-season effects were significant for most litter traits, while month of kindling affected litter weight and gain at 21 days and milk yield during the first 7 days (P < 0·05 or P < 0·001). Litters kindled during winter had the highest milk yield compared with litters kindled in the other seasons. Milk production, litter size and weight and litter gain had curvilinear relationship with parity (P < 0·05 or P < 0·001). Sire of doe had no significant effects on litter traits studied. Repeatabilities of all traits were low and ranged from 0·001 to 0·134. Litter size and weight at birth were residually correlated with milk yield. Litter weight and gain at 21 days were significantly correlated with the lactational performance of the doe (P < 0·001).

This study was conducted to determine the relationship between plasma concentrations of thyroxine (T4), triiodothyronine (T3) and body weight in young Majaheem male camels. Eighteen camels aged 6 to 7 months were divided equally into three groups (Gl, G2 and G3). All groups were given concentrate pellets (187 g crude protein per kg) at the rate of 15 g/kg body weight daily. In addition, each group was given one of the following roughages: lucerne hay to Gl, rhodes grass hay to G2 and ammonia-treated wheat straw to G3. Roughages, salt and water were measured and given ad libitum. Every 2 weeks all camels were weighed and blood samples were collected. Data were statistically analysed using a general linear model procedure. There was a positive correlation between T4 concentration and body weight. T4 was higher in camels given either hay or straw compared with those given rhodes grass hay, while there were no differences among the three groups in T3 and in body weight.

Ten crossbred boars were penned individually and offered either meal or pellets of identical composition to appetite from single space hopper feeders which also provided water. The hoppers were sited on raised steel mesh platforms 1·2 m × 0·87 m in size under which was placed a similar sized collecting tray. Spilled food was collected for 24 h once weekly for the 4-week experimental period. Live-weight gain tended to be lower on the meal diet compared with the pellets (882 v. 968 (s.e. 28·7); P = 0·07) while food conversion efficiency (g food per g growth) was worse on the meal diet (2·65 v. 241 (s.e. 0·059); P < 0·05). Food spillage is the most likely explanation for the difference in food conversion, however collectable spilled food was (g/g food offered) 0·0089 and 0·0026 respectively of meal and pellets offered. The value for the meal diet is about one-tenth of the expected value and suggests that direct collection of spillage from non-pelleted diets even over a wide area in front of the feeder is not an accurate technique.

In an experiment involving 30 roosters and 15 mature male ostriches the apparent metabolizable energy (ME) values, corrected for zero nitrogen retention (AMEn), were determined by balance method for maize and lucerne meal. A group of 10 roosters received maize as the sole dietary component. For the second group of 10 roosters a blend of 750 g/kg maize and 250 g/kg lucerne was prepared. The diet of the third group consisted of 500 g/kg maize and 500 g/kg lucerne meal. The ostrich basal diet consisted of 1000 g/kg lucerne, and was blended in the ratios 50 lucerne: 50 maize and 25 lucerne: 75 maize. Each dietary treatment was given to five ostriches, individually housed in metabolism crates. Food intake and excreta collection was carried out over a period of 5 days after the ostriches had been accustomed to the diets for 7 days. For roosters food intake and excreta collection lasted for 72 h after an adaptation period of 24 h.

The AMEn value for maize was 14·49 (s.e. 0·046) MJ/kg in roosters while in ostriches AME,, values of 14·3 (s.e. 1·81) and 14·5 (s.e. 0·845) MJ/kg for the 500 g/kg inclusion and 250 g/kg inclusion respectively were found.

In roosters lucerne meal yielded AME,, values of 4·49 (s.e. 0·506) and 4·05 (s.e. 0·321) at 250 g/kg and 500 g/kg inclusion levels respectively. For the ostriches a value of 8·9 (s.e. 0·755) Mj/kg was found for lucerne.

True ME, corrected for zero nitrogen retention, (TMEJ was computed by regressing gross energy output on gross energy input over all feeding levels. Maize yielded values of 14·65 (s.e. 0·0455) and 14·9 (s.e. 0·351) for roosters and ostriches respectively while corresponding values for lucerne were 4·03 (s.e. 0·118) and 8·6 (s.e. 0·296) MJ/kg.

It was concluded that the ostriches were capable of digesting a high starch diet such as maize to the same extent as adult roosters but ostriches were capable of digesting a high fibre ingredient such as lucerne meal much more efficiently.

Twenty-eight Suffolk-cross male castrated lambs aged 7 to 8 months, initial live weight 36 (s.e. 149) kg were given four diets which contained unground pelleted molassed sugar-beet pulp and rolled barley (940 g/kg, fresh weight basis) in the following proportions either A, 0·8 to 0·2 or B, 0·5 to 0·5, with 60 g soya-bean meal per kg. Diets A and B were offered with or without a yeast culture product Yea-Sacc. Diets zvere offered twice daily to appetite with 100 g hay per head. Yeast culture had no effect on any measurement made (P > 0·05). Lambs given diet B consumed more dry matter (DM), grew faster and had superior food conversion efficiencies (all P < 0·01). Rumen fluid taken 3 h after feeding contained higher concentrations of ammonia (F < 0·01), total volatile fatty acids (F < 0·001) and acetic acid (F < 0·001) in samples from lambs given diet A. Rumen fluid samples collected before the 10·00 h meal, produced more gas from diet A than diet B after 6 and 24 h in vitro incubation (F < 0·001) suggesting the presence of more undigested food. When ground diets were incubated, more gas was produced from diet A after 6h (F < 0·05) but not after 24 h fP > 0·05). It is suggested that diet B supported faster growth of the lambs as a result of faster rate of digestion, higher DM intake and superior food conversion.

A two-treatment experiment was made involving 340 crossbred pigs penned in groups of 20 and offered a cereal-based, non-pelleted diet ad libitum from one single-space hopper per pen supplying both food and water. Half the feeders were fitted with stalls which protected the feeding pig from its pen mates. The average number of visits per day to the feeder was reduced from 20·1 to 11·9 (s.e. 1·58, P<0·01) by fitting the stall and the average duration of each visit was increased from 2·06 min to 4·18 min (s.e. 0·298, P < 0·02). The total time of occupation and its circadian pattern were similar for both treatments There were reductions in the incidence of enforced withdrawals (12·7 v. 3·4 (s.e. 0·75), P < 0·001) and of pigs queuing (28·6 v. 84 (s.e. 2·35), P < 0·001) with the addition of a stall which also reduced the occurrence of tail biting. Although the stall improved pig welfare the anticipated reduction in food spillage was not evident.

The value of a parameter such as heritability (h2) or intra-dass correlation in best linear unbiased prediction (BLUP) with the animal model or a family selection index affects both the rate of response achieved and the rate of inbreeding. If in BLUP an estimate of h2 is used which is biased upwards above its actual value, the rate of inbreeding can be substantially reduced with little reduction in the rate of response. Further, by mating individuals from families in which many are selected to others from families with few selected (compensatory mating), rates of inbreeding can be further reduced without substantial effect on response.

Eight sets of identical twin heifers and their first three calf crops were used to determine effects of single-trait selection for blood serum insulin-like growth factor 1 (IGF-1). Twin heifers were offspring of Simmental sires and Hereford × Simmental or Hereford × Angus dams. All 16 heifers were mated with the same Simmental bull in each year of the study to produce calves born in 1989, 1990 and 1991 (no. = 16, 13 and 10, respectively). Although differences were noted in performance of progeny from the four twins with the highest v. the four with the lowest IGF-1 concentrations, they zoere not large enough to recommend single-trait selection for blood serum IGF-1 in beef heifers.