Although the extent of ossification between the caracoid and clavicle bones of the pectoral girdle (ossa cinguli membrii thoracici) in the ostrich carcass can be used to determine between ossification classes within the age range 8 to 14 months (considered as the optimal time of slaughter of ostriches), it is not an accurate tool for estimating the exact age at slaughter. It is possible to distinguish between carcasses originating from the birds between 10 and 12 months of age, at which ostrich meat toughens.

Economic values for average ad libitum food intake capacity (FIC) were estimated with two different linear-plateau models. One model based on a constant minimum fat to protein deposition ratio (Rmin). The other model relied on a constant minimum marginal ratio between fat and protein deposition (MR). Economic values were used to define aggregate genotypes where the driving variables of the growth models were considered as traits. The consequences of a possible implementation of such aggregate genotypes were evaluated with a comparison of the expected selection responses for the different traits.

Economic values for the traits under the two models indicated the same direction of selection and differed only slightly in their magnitude. For a FIC below its optimum, FIC had a positive and Rmin or MR a negative, economic value. In this situation the maximum protein deposition rate Pdmax had no influence on the production costs and therefore an economic value of zero. Selection emphasis is then mainly put on FIC which leads to an increase in average daily gain (ADG). If FIC is above its optimum, economic values for FIC were negative, positive for Pdmax and equal to zero for Rmin or MR. Practically no differences between the selection responses under the two growth models were observed.

The use of growth models to estimate economic values for FIC allowed to attribute a positive economic value to this trait if it is below its optimum. This is not possible when economic values are estimated with an economic production model.

Three experiments (EXP) were conducted to determine the role of insulin-like growth factor-I (IGF-I) in the control of growth hormone (GH) and LH secretion. In EXP I, prepuberal gilts, 65 ± 6 kg body weight and 140 days of age received intracerebroventricular (ICV) injections of saline (n = 4), 25 μg (n = 4) or 75 μg (n = 4) IGF-I and jugular blood samples were collected. In EXP II, anterior pituitary cells in culture collected from 150-day-old prepuberal gilts (n = 6) were challenged with 0.1, 10 or 1000 nM [Ala15]-h growth hormone-releasing hormone-(1-29)NH2 (GHRH), or 0.01, 0.1, 1, 10, 30 nM IGF-I individually or in combinations with 1000 nM GHRH. Secreted GH was measured at 4 and 24 h after treatment. In EXP III, anterior pituitary cells in culture collected from 150-day-old barrows (n = 5) were challenged with 10, 100 or 1000 nM gonadotropin-releasing hormone (GnRH) or 0.01, 0.1, 1, 10, 30 nM IGF-I individually or in combinations with 100 nM GnRH. Secreted LH was measured at 4 h after treatment. In EXP I, serum GH and LH concentrations were unaffected by ICV IGF-I treatment. In EXP II, relative to control all doses of GHRH increased (P < 0.01) GH secretion. Only 1, 10, 30 nM IGF-I enhanced (P < 0.02) basal GH secretion at 4 h, whereas by 24 h all doses except for 30 nM IGF-I suppressed (P < 0.02) basal GH secretion compared to control wells. All doses of IGF-I in combination with 1000 nM GHRH increased (P < 0.04) the GH response to GHRH compared to GHRH alone at 4 h, whereas by 24 h all doses of IGF-I suppressed (P < 0.04) the GH response to GHRH. In EXP III, all doses of IGF-I increased (P < 0.01) basal LH levels while the LH response to GnRH was unaffected by IGF-I (P > 0.1). In conclusion, under these experimental conditions the results suggest that the pituitary is the putative site for IGF-I modulation of GH and LH secretion. Further examination of the role of IGF-I on GH and LH secretion is needed to understand the inhibitory and stimulatory action of IGF-I on GH and LH secretion.

The dietary inclusion of feed additives to improve the carcass characteristics of the final product is of great importance for the pork production chain. The aim of our study was to evaluate the effects of the association of ractopamine (RAC) and conjugated linoleic acid (CLA) on the performance traits of finishing pigs during the last 26 days prior to slaughter. In total, 810 commercial hybrid barrows were used. Animals were distributed among treatments according to a randomised block design in a 3 × 3 factorial arrangement, with three RAC levels (0, 5 or 10 ppm) and three CLA levels (0, 0.3 or 0.6%). Pigs fed the diet with 5 ppm RAC had higher average daily feed intake (ADFI) (2.83 kg; P < 0.05) when compared with those fed 10 ppm RAC and the control diet (2.75 and 2.74 kg, respectively). Lower ADFI values (P < 0.01) were observed with the diets containing CLA compared with the control diet with no CLA (2.73 and 2.75 v. 2.85 kg/day, respectively). The average daily weight gain of pigs fed 5 and 10 ppm RAC was +148 and +173 g/dayhigher (P < 0.001), respectively, than those fed the control diet. Dietary RAC levels influenced (P < 0.001) feed conversion ratio (FCR), which was reduced as RAC levels increased, with the pigs fed 10, 5 and 0 ppm RAC presenting FCR values of 2.57, 2.71 and 3.05, respectively. FCR also improved (P < 0.05) with the inclusion of 0.6% CLA relative to the control diet (2.70 v. 2.84, respectively). There was a significant interaction between CLA × RAC levels (P < 0.01) for final BW, loin eye area (LEA) (P < 0.05) and backfat thickness (BT) (P < 0.05). The treatments containing 10 ppm RAC + 0.6% or 0.3% CLA increased LEA and reduced BT. In conclusion, the level of 10 ppm inclusion of RAC increased the overall performance parameters of pigs and therefore improved production efficiency. The combined use of RAC and CLA promoted a lower feed conversion ratio as well as better quantitative carcass traits, as demonstrated by the higher LEA and lower BT. The dietary inclusion of CLA at 0.3% improved feed efficiency, however, without affecting LEA or BT yields.

To investigate the effect of dietary fat and metabolizable energy (ME) on milk protein concentration, an experiment was carried out using 12 multiparous early-lactation Holstein-Friesian dairy cows. Three diets were offered in a complete Latin-square change-over design, based on ad libitum access to grass silage. One of three concentrates was offered at a rate of 12 kg/day, each formulated to supply one of two levels of ME (12·1 and 13·6 MJ/kg dry matter (DM)) and one of two levels of fat (31 and a mean of 88 g acid hydrolysis ether extract per kg DM): low energy, high fat (LEHF); low energy, low fat (LELF); and high energy, high fat (HEHF). The concentration of milk protein was significantly higher from animals offered the LELF concentrate (32·5 v. a mean of 31·2 (s.e.d. 0·45) g/kg, P < 0·05), because of lower milk yields (31·0 v. a mean of 33·4 (s.e.d. 0·63) kg/day, P < 0·05). Animals offered the HEHF concentrate produced the highest yields of milk protein but their milk had the lowest concentrations of fat (32·5,34·4 and 31·9 g/kg for LEHF, LELF and HEHF respectively; s.e.d 1·07; P < 0·05 for difference between LELF and HEHF). Silage DM intake was significantly increased by animals offered the LEHF concentrate (9·1, 8·6 and 8·7 (s.e.d. 0·19) kg/day, P < 0·05 for differences between LEHF and the other two concentrates). Urinary purine derivative excretion, used as an index ofmicrobial protein supply, was highest from animals offered the LELF and HEHF concentrates, which both supplied similar amounts of fermentable ME. It is hypothesized that increased de novo synthesis offatty acids on the low fat diet reduced the availability of glucose for lactose synthesis, leading to reduced milk yields and hence increased milk protein concentrations.

The effects of average carcass fat concentration of a group of lambs on correlations among lamb carcass measurements within the group and of slaughter age on variances of carcass measurements were studied. Three-hundred and sixty-eight crossbred lambs from one experiment were slaughtered on 10 days over a 2-year period. Average carcass fat concentration of the 10 groups ranged from 179 to 326 g/kg carcass weight. Variances of carcass fat, water and protein concentrations and of muscle measurements did not increase at later slaughter ages but variances of kidney fat weight, fat depths and total tissue depths increased. Several correlations among carcass measurements had significant regressions on average carcass fat composition of the groups slaughtered. When measurements were adjusted for age but not weight, correlations of carcass weight, kidney fat weight, specific gravity, tibia and tarsus length and m. longissimus depth with carcass fat, water and protein concentrations weakened as carcass fat concentration of the group increased. Correlations of kidney fat, specific gravity and m. longissimus width with fat, water and protein concentrations adjusted for carcass weight weakened as average carcass fat concentration of the group increased. Multiple regression equations did not reveal any advantage in using combinations of muscle or leg dimensions to predict fat concentration.

Erythropoietin (EPO) gene therapy can be used for several purposes; however, its effects on reproductive performance are unknown. The aim of this study was to evaluate the toxicological effects of non-viral (EPO) gene transfer on sperm motility, viability, morphology and concentration. Rabbit EPO cDNA was cloned into a pTarget mammalian expression vector. Rabbits were administered with: (1) pTarget/EPO vector, (2) recombinant human EPO (rHuEpo) and (3) saline (control). Both pTarget/EPO and rHuEpo significantly increased (P < 0.05) hematocrit levels 1 week after injection and they remained significantly higher than the control for up to 5 weeks (P < 0.05), showing that both EPO treatments were effective in stimulating the production of red blood cells in rabbits. The EPO gene transfer or rHuEPO administration had no significant effect (P > 0.05) on sperm motility, vigor, viability, concentration or morphology in the testis.

Flaking is widely used by the feed industry since it is considered to improve the digestibility and palatability of cereals for young pigs. Pelleting is believed to give similar benefits plus a reduction in feed wastage and improved voluntary intake. However, the scientific literature lacks consenssus on this subject and provides no clear indication whether the response to feed processing is influenced by the type of cereal used. This experiment examined the effects of flaking, cereal type and diet pelleting on the voluntary intake and performance of early weaned piglets.

Blood from 106 females (1 to 7 years old) of the Cambridge flock at the University of Wales, Bangor was analysed for 21 protein systems. Of the 11 polymorphic systems, haemoglobin protein (HBB) was found to be significantly associated with ovulation rate as measured by mean ovulation rate for all records per ewe. Mean ovulation rate for the HBB AA genotype was 1·25 ovulations higher than for the AB and BB genotypes (P < 0·001). The results suggest that a gene segregating in this breed is different from the Booroola (FecB) gene and that lambs of either sex can be screened at a young age for a major difference in ovulation rate.

We investigated whether kids were able to discriminate their own mother from an alien one in a two-choice test on the day of birth when they had access to acoustic, visual and olfactory cues from their mother, and whether this discrimination depended on the selective maternal behaviour of the mother (i.e. exclusive nursing of own kids). When given the choice between their own mother and an alien equivalent dam, 8-h-old kids did not show a significant preference for their dam, whereas 12- and 24-h-old kids did. When given the choice between their own and an alien mother that were both non-selective because they had been rendered peripherally anosmic by irrigation of the nostrils with zinc sulphate, 12-h-old kids did not show a significant preference for their mother. These results are similar to those reported in sheep and may suggest that the contrast of behaviour between their own and an alien mother existing in normosmic does is important for discrimination of dams by kids at this age. Finally, testing 8-h-old kids in a smaller enclosure resulted in some improvement of their performance, although they still failed to display a significant preference for their mother. On the whole, kids are able to discriminate between their own and an alien mother goat as early as previously reported in lambs. The impairment of this ability when mothers are anosmic and not selective suggests that acceptance behaviours displayed by the mother may serve as one of the cues orientating the choice of the kid when given the choice between intact mothers. Finally, the present results do not suggest the existence of fundamental differences in the establishment of a preference for the mother between lambs, which are followers, and kids, which are hiders.

1. Four fitter-mates from 20 litters on each of 3 farms were divided equally and distributed at random between two treatment groups. Each piglet was injected intramuscularly with 2 c.c. of an iron preparation between 1 and 2 days of age. The control group received an iron-dextran complex which provided 150 mg. of iron per piglet and a second group received an irondextrin complex which provided 200 mg. of iron per piglet.

2. The body weight and the level of haemoglobin in the blood of each piglet were measured at 1, 8, 15, 22, and 56 days of age and the incidence and cause of disease and mortality were recorded.

3. The level of haemoglobin in the blood of both groups was comparable throughout the experiment.

4. At the 22nd and 56th day, the group receiving 200 mg. of iron was approximately 6% heavier than the group receiving 150 mg. of iron. These differences were highly significant at the 0·1% level.

5. From each of 3 additional litters, 3 piglets received no supplementary iron while 5 piglets received 200 mg. of iron provided by the iron-dextrin complex. The three whole litters were slaughtered on days 3, 8, and 22 respectively. The mean level of iron per 100 g. of liver and spleen within the untreated group on the above occasions was 5·8, 5·8, and 3·7 mg. respectively, compared with 72·9, 55·1, and 17·6 mg. respectively within the treated piglets. The differences were highly significant at 0·1 % level.

The effects of recombinantly derived growth hormone (GH), oestradiol-17β plus trenbolone acetate, clofibrate, melatonin and fasting on basal plasma triglycerides (TG) and TG entry rate were determined in wether lambs given lucerene/barley pellets ad libitum. Clofibrate was administered at 2 × 0·5 g capsules orally, GH (0·25 mg/kg live weight) was injected subcutaneously daily whilst oestradiol-17β, oestradiol-17β plus trenbolone acetate and melatonin were slow release implants (either 4 or 4·8 mg, 4 nig and 20 nig and 18 mg respectively) placed subcutaneously in the ear. Both fasting and oestradiol treatments raised basal TG levels without influencing TG entry rates, defined as the maximum rate of change of plasma TG 3 to 6h following a dose of Triton WR1339 of at least 0·2 g/kg live weight. Entry rates were similar to those previously reported for goats but were higher than those reported for sheep. Triton WR1339 used to determine entry rates was found to reduce food intake at all levels in some sheep despite reports to the contrary. Among the various treatments, only oestradiol-17β and trenbolone acetate influenced body composition as determined by chemical analysis of minced carcasses, resulting in an increased gain of carcass protein and decreased gain of carcass fat. Clofibrate, melatonin and Triton, if allowance is made for Triton-induced loss in food intake, had no clear effects on body fatness. Overall the effects of hormones on plasma TG appeared to be small and it seems improbable that plasma TG are involved in effects of hormones on fatness.

The importance of lameness in dairy cattle in UK in terms of its economic consequences and welfare considerations is well documented (Russel and others, 1982). While such epidemiological work has identified factors of importance in the aetiology of the various conditions associated with lameness it has been less successful in apportioning their relative importance, particularly for those conditions affecting the hoof. A series of experiments has been conducted at the West of Scotland College over the period 1983 to 1989 mainly investigating the relationship of nutrition and lameness. In one of these Manson and Leaver (1988) found a significant difference in the prevalence of lameness between two groups of cattle fed complete diets containing either 16.1 or 19.8% crude protein. They also found a significant increase in mean locomotion score (LS) and commented that further studies were needed to understand the dietary processes by which the hoof of the cow was predisposed to such problems.

The objective of this experiment was to investigate the influence of the type of protein source in the concentrate upon the locomotion of the cows, the incidence and prevalence of lameness and finally on hoof hardness, shape, growth and wear.

To evaluate passive and active methods for rewarming hypothermic lambs, the rectal temperature of 19 neonatal lambs (4·9 (s.e. 0·34) kg) was reduced to 35°C by cold water immersion. Metabolic responses and change in rectal temperature were monitored as the hypothermic lambs recovered with added insulation in a 20 to 25°C air environment, or with thermal assistance provided by an infrared heat lamp, or through immersion in 38°C water. During the first 12 min of rewarming, the rise in rectal temperature in all treatment groups was linear, however it was more rapid with the lambs immersed in warm water (0·26°C/min; P < 0·05) as compared with the insulated lambs (0·21°C/min) and the lambs rewarmed with a heat lamp (0·22°C/min). During this 12-min period, the insulated lambs produced metabolic heat more rapidly than did the warm-water lambs, 13·6 v. 11·1 (s.e. 0·67) W/kg, respectively (P < 0·05). These data indicate that there was a substantial influx of heat which contributed to the increase in body temperature of the lambs immersed in warm water. Stabilization of rectal temperature occurred after 18 to 20 min in all treatment groups. The lambs recovered in all treatment groups, in addition, no clinical problems were observed in any of the lambs during the tests or subsequently when they were returned to their dams.

Access to an outdoor range has many potential benefits for laying hens but range use can be poor due to factors only partly understood. Techniques to monitor individual range use within commercial flocks are crucial to increase our understanding of these factors. Direct observation of individual range use is difficult and time-consuming, and automatic monitoring currently relies on equipment that is difficult to use in an on-farm setting without itself influencing range use. We evaluated the performance of a novel small, light and readily portable light-based monitoring system by validating its output against direct observations. Six commercial houses (2000 hens/house) and their adjacent ranges were used, three of which were equipped with more structures on the range than the others (to determine whether cover would influence monitoring accuracy). In each house, 14 hens were equipped with light monitoring devices for 5 discrete monitoring cycles of 7 to 8 consecutive days (at 20, 26, 32, 36 and 41 weeks of age). Light levels were determined each minute: if the reading on the hen-mounted device exceeded indoor light levels, the hen was classified as outside. Focal hens were observed directly for 5 min/hen per week. Accuracy (% of samples where monitoring and direct observations were in agreement) was high both for ranges with more and with fewer structures, although slightly better for the latter (92% v. 96% ± 1 SEM, F1,19 = 5.2, P = 0.034). Furthermore, accuracy increased over time (89%, 94%, 95%, 98% ± 1 SEM for observations at 26, 32, 36 and 41 weeks, respectively, F3,19 = 3.2, P = 0.047), probably due to progressively reduced indoor light levels resulting from partial closing of ventilation openings to sustain indoor temperature. Light-based monitoring was sufficiently accurate to indicate a tendency for a greater percentage of monitored time spent outside when more range structures were provided (more: 67%, fewer: 56%, SEM: 4, $\chi_1^2 = 2.9$, P = 0.089). Furthermore, clear and relatively consistent individual differences were detected. Individuals that were caught outside at the start of the experiment ranged more throughout its duration (caught outside: 72%, caught inside 51%, SEM: 4, $\chi_1^2 = 10.0$, P = 0.002), and individual range use was correlated between monitoring cycles (for adjacent monitoring cycles: $r_s^2 = 0.5-0.7$, P < 0.0001). This emphasizes the importance of studying range use on an individual level. In conclusion, our light-based monitoring system can assess individual range use accurately (although accuracy was affected by house characteristics to some extent) and was used to show that both cover availability and individual characteristics affected range use.

The genetic and economic consequences of introgression of either one or two genes that explain the complete between-breed difference for disease resistance between donor and recipient breeds were investigated. Four backcross strategies (0, 1, 3 or 7 generations of backcrossing) were compared for four initial breed differences (0·1, 1, 2·5 and 5 phenotypic s.d.) when female reproductive capacity was either high (10 offspring) or lower (four offspring). Selection in donor and recipient populations was for production using a selection index. Genetic comparison was based on production level between the hybrid population, after fixation of the disease resistance alleles, and the donor population. Tor a large initial breed difference and high female reproductive capacity, application of seven generations of backcrossing resulted in the largest genetic difference between donor and hybrid populations. Introgression of one or two genes made no difference to the genetic results. From an economic point of view, optimal number of generations depends on the number of genes involved in the introgression, on the female reproductive capacity and ön the initial breed difference. Seven generations of backcrossing in most cases are too many and none to three generations of backcrossing often is more optimal. Introgression of two genes is economically less attractive, especially in case of low female reproduction capacity.

1. Nitrogen balance studies were conducted on 16 steers in two separate trials. The steers were fed on four diets containing respectively dry rolled barley; dried, steamed and rolled barley; dried, crimped barley and barley that had been stored in a sealed silo and rolled.

2. There were no significant differences in the dry-matter intake of any of the diets.

3. No consistent differences between the diets in dry-matter digestibility or nitrogen retention were observed.

The aim of this study was to evaluate nitric oxide (NOx) concentration in infected and non-infected mammary quarters of dairy heifers before and after calving. The relationship between bacterial species and NOx concentrations, as well as correlation between NOx concentrations and postpartum somatic cell count (SCC), was assessed. Coagulase-negative staphylococci, Staphylococcus aureus and Escherichia coli were the bacteria commonly isolated during the pre- and postpartum period. Infected quarters had greater NOx concentrations than non-infected quarters before (30.81 v. 22.83 μM/ml, P < 0.05) and after (9.56 v. 5.77 μM/ml, P < 0.0001) calving. It was determined that the interaction between sampling period and infectious status had no effect on NOx concentration (P < 0.16). Infected quarters had greater SCC (log10) than healthy quarters (4.95 v. 4.39; P < 0.0001). NOx concentrations, however, did not correlate with SCC (r = 0.02). In summary, changes in NOx concentration were mainly dependent on the infectious status of the quarters with variations among the bacterial species (P < 0.05).

Forty-four Borana × Friesian F1 crossbred calves born to Borana (Bos indicus) cows were randomly assigned to either suck their dams hvice daily or bucket-feeding with 1341 milk over a 57-day pre-weaning period. Their dams were also allocated either to a supplement group with grass hayad libitumand 5 kg per head per day of a concentrate ration or to an unsupplemented group withad libitumgrass hay only. Calves were fed in individual boxes in a calf house. The mean birth weight of calves was 24·8 (s.e. 1·8) kg. Suckled calves were heavier (P < 0·01) at weaning (47·7 (s.e. 1·9) v.37·1 (s.e. 1·8) kg) and had faster pre-weaning growth rate (411 (s.e. 30)v.215 (s.e. 29) g/day) than bucket-fed calves. Calves which sucked supplemented cows were heavier (P < 0·001) at weaning (51·2 (s.e. 2·6)v. 44·2 (s.e. 2·6) kg), had faster (P < 0·01) pre-weaning growth rate (477 (s.e. 41)v.346 (s.e. 41) glday) and higher (P<0·01) daily milk intake (2·6 (s.e. 0·2)v.1·6 (s.e. 0·2) I/day) than those which sucked unsupplemented cows. Mean concentrate intake was 302 (s.e. 30) g/day for bucket-fed calves and 341 (s.e. 33) and 408 (s.e. 33) g/day for calves which sucked supplemented and unsupplemented cows. Cow milk production was higher (P < 0·01) in suckled than in milked cows (3·3 (s.e. 0·2)v.1·0 (s.e. 0·2) I/day) and in supplemented than unsupplemented cows (3·9 (s.e. 0·2)v.2·7 (s.e. 0·2) I/day). Concentrations of milk protein, fat and total solids averaged 39 (s.e. 15), 49 (s.e. 16) and 143 (s.e. 21) g/kg, respectively and were not significantly influenced by either concentrate supplementation or suckling. Restricted suckling and early weaning coupled with appropriate calf and cow feeding regimes could be one of the alternatives for calf rearing under smallholder and small scale peri-urban dairy production systems. However, further studies are warranted to evaluate the effects of such a strategy on both calf and cow performances under these production systems.