Improving milk nitrogen efficiency through a reduction of CP supply without detrimental effect on productivity requires usage of feeding systems estimating both the flows of digestible protein, the exported true proteins and from these predict milk protein yield (MPY). Five feeding systems were compared in their ability to predict MPY v. observed MPY in two studies where either protein supply or protein and energy supply were changed. The five feedings systems were: Cornell Net Carbohydrate and Protein System (v6.5.5), Dutch protein evaluation system (1991 and 2007), Institut National de la Recherche Agronomique in France (INRA), National Research Council and NorFor. The key characteristic of the systems with the best predicted MPY was the inclusion of a variable efficiency of utilisation of protein supply taking into account the supply of both protein and energy. The systems still using a fixed efficiency had the highest slope bias in their prediction of MPY. Therefore, the development of new feeding systems or improvement of existing systems should include a variable efficiency of utilisation of the protein related to both the protein and energy supply. The limitation of the current comparison did not allow determining if additional factors, as used in INRA, were beneficial. This concept should also probably be transferred to essential amino acids.

Results are presented on weight changes in sows which indicate (1) that checks to increases in weight at specific stages appear to be a normal function of pregnancy in sows, (2) that most of the weight gained during pregnancy in excess of that accounted for by the litter and placenta is lost before the next pregnancy, either during lactation or, if this is prevented, immediately after weaning, (3) that considerable weight loss occurs between weaning and re-mating on a level of feeding which is sufficient to allow a mean gain of 1 lb. per day during pregnancy, and (4) that sows given a relatively low level of total feed during lactation appear to lose considerably less weight between weaning and re-mating, and to gain weight more rapidly during the first few weeks of pregnancy, than those fed to a relatively high level during lactation. Practical implications of these results are considered.

The diameter of adipocytes from subcutaneous, intermuscular and internal cavity fat depots of 5 pre- and 14 postnatal Romney female sheep was measured, the volume calculated, and the number per depot computed from the weight of triglyceride in the depots.

The rates of increase of adipocyte volume relative to the increase in weight of total side adipose tissue, and of the fat depots and their chemical components, were calculated using linear regression analyses of the natural logarithmic transformed data. These logarithmic regression equations were used to estimate the volume of adipocytes in sheep at different stages of development. The total numbers of adipocytes at each stage of growth were estimated using linear double logarithmic regressions of adipocyte number on carcass weight.

The growth of total adipose tissue and of each of the fat depots occurred mainly by an increase in the adipocyte volume, which increased over 70-fold from 120 days gestation to 5 years of age. The increase in adipocyte volume during growth occurred at similar rates in all of the fat depots and no significant differences between the volumes of adipocytes from the fat depots were found within sheep of similar carcass weight. During the same growth period the total number of adipocytes increased about 6-fold. Differences in the relative rates of growth of the fat depots were attributed to cellular multiplication rather than to cellular enlargement.

Osteochondrosis might reduce the performance of slaughter pigs, longevity of sows and animal welfare. The aim of the present work was to describe the prevalence in Swiss breeds and to analyse the genetic background of osteochondral lesions. Between January 2002 and December 2005, about 9500 station-tested pigs were examined for several exterior traits before slaughtering at the Swiss pig performance testing station using the Swiss linear description system with a scale from 1 to 7 per trait. The animals belonged to three breeds: Large White dam line, Swiss Landrace and Large White sire line. Additionally, a random sample of these pigs (n = 2622) was examined for osteochondral lesions at seven positions of the carcass after dissection. At first, the surface and shape of the femur, humerus, radius and ulna at the joints were evaluated by a trained person. Afterwards these bones were sawed and the state of the cartilage and the distal epiphyseal cartilage of the ulna was examined at the cutting surface. Osteochondral lesions were scored on a scale from 1 to 6. The prevalence of osteochondral lesions was low at head of humerus, condylus lateralis humeri, radius and ulna proximal and head of femur. Osteochondral lesions at condylus medialis humeri (CMH), distal epiphyseal cartilage of ulna (DEU) and condylus lateralis femoris (CMF) exhibited phenotypic and genetic variance. Their heritabilities ranged from 0.16 to 0.18 using linear mixed animal models. Therefore, it is possible to reduce the prevalence of osteochondral lesions by selection in principle. Exterior traits showed low heritabilities (0.10 to 0.26) but several favourable genetic correlations with osteochondral lesions at CMH, DEU and CMF with low to moderate magnitude. Genetic correlations between osteochondral lesions and production traits were low.

Twenty-four Friesian calves were fed from twelve weeks of age on six diets containing 15 or 30% ground barley straw, the straw being ground through screens of and in.

From twelve weeks to seven months of age (120–250 kg) the calves had mean growth rates of 1·15 kg/day with a feed conversion ratio of 4·15: 1. From seven to eleven months of age (250–380 kg) the corresponding figures were 1·16 kg/day and 5·53: 1, and in the final fattening period of 11–14 months (380–500 kg), 0·92 kg/day and 8·19: 1.

These differences between stages of fattening were highly significant. There were no differences in performance due to the particle size of the straw or to the proportion of straw in the diet.

In this experiment, we assessed the effect of amino acid (AA) intake restriction in entire male Yorkshire pigs between 15 and 38 kg BW (restriction phase) on BW gain, body composition and plasma levels of blood urea nitrogen (BUN), cortisol, insulin-like growth factor I (IGF-I), growth hormone (GH) and leptin during the subsequent re-alimentation phase. During the restriction phase, 36 pigs were allotted to one of two dietary treatments: adequate AA intake (control) or AA-limiting diets (AA-30%). Thereafter, pigs were fed common non-limiting diets up to 110 kg BW. Throughout the experiment, pigs were scale-fed at 90% of the estimated voluntary daily digestible energy intake. At the end of the restriction phase, pigs on AA-30% had lesser BW gain (650 v. 784 g/day; P < 0.001), loin area (LA; 12.2 v. 14.2 cm2; P < 0.001), BUN (4.6 v. 6.3 mg/dl; P < 0.02), lesser plasma levels of IGF-I (440 v. 640 ng/m; P < 0.001) and cortisol (8.2 v. 19.2 μg/dl; P < 0.001), greater backfat thickness (BF; 7.56 v. 6.56 mm; P < 0.02), and greater plasma levels of leptin (2.7 v. 1.8 ng/ml; P = 0.027) and GH (3.3 v. 2.0 ng/ml; P = 0.05) than pigs on control. During the re-alimentation phase, previously restricted pigs showed full compensatory growth (CG) in terms of BW gain (1170 v. 1077 g/day; P < 0.002), whole-body protein deposition (Pd) (179 v. 163 g/day; P < 0.001) as well as physical and chemical body composition (whole-body lipid to body protein mass ratio, LB/PB; 1.14 v. 1.15; P > 0.10). Besides GH at 45 kg BW (4.2 v. 2.4 ng/ml; P = 0.066), there were no effects of previous AA intake restriction on leptin, IGF-I and BUN during the re-alimentation phase (P > 0.10). Plasma cortisol and IGF-I levels may act as an indicator of AA-induced restriction in Pd in growing pigs. Plasma BUN level does not appear as a sensitive indicator for compensatory Pd. Plasma leptin and GH levels allow for the involvement of the brain in controlling chemical body composition. Full CG was observed during the energy-dependent phase of Pd in growing pigs and might be driven by a target LB/PB, possibly mediated via plasma leptin, IGF-I and GH levels.

The objectives of this study were to establish standards for growth and to model the evolution of wither height (WH) between birth and adult age in different breeds of sport- and race-horses. Therefore, 398 foals, then yearlings of three different breeds, were measured regularly between birth and 18 months of age. Linear and non-linear functions were compared for describing the growth in each breed group. The monomolecular, Gompertz, logistic and cubic models correctly estimated WH in the three breeds during the first 2 years (R2 = 0.99, s.e. 3.9 to 4.5) and better than the cubic and quadratic models (R2 = 0.93, s.e. = 4.7 to 5.3). The logarithmic and power model seemed better in the last part of the growth period (2 to 6 years, R2 = 0.85, s.e. = 5.6 to 5.9). The linear model did not fit with data on most of the growth period. Comparison of the growth in the three breeds using these models confirmed that race-horses had an intense growth in their first months whereas sport-horses had a more regular growth prolonged in their first years of life.

The assessment of animal welfare can include resource-based or animal-based measures. Official animal welfare inspections in Denmark primarily control compliance with animal welfare legislation based on resource measures (e.g. housing system) and usually do not regard animal response parameters (e.g. clinical and behavioural observations). Herds selected for welfare inspections are sampled by a risk-based strategy based on existing register data. The aim of the present study was to evaluate register data variables as predictors of dairy herds with violations of the animal welfare legislation (VoAWL) defined as occurrence of at least one of the two most frequently violated measures found at recent inspections in Denmark, namely (a) presence of injured animals not separated from the rest of the group and/or (b) animals in a condition warranting euthanasia still being present in the herd. A total of 25 variables were extracted from the Danish Cattle Database and assessed as predictors using a multivariable logistic analysis of a data set including 73 Danish dairy herds, which all had more than 100 cows and cubicle loose-housing systems. Univariable screening was used to identify variables associated with VoAWL at a P-value<0.2 for the inclusion in a multivariable logistic regression analysis. Backward selection procedures identified the following variables for the final model predictive of VoAWL: increasing standard deviation of milk yield for first lactation cows, high bulk tank somatic cell count (⩾250 000 cells/ml) and suspiciously low number of recorded veterinary treatments (⩽25 treatments/100 cow years). The identified predictors may be explained by underlying management factors leading to impaired animal welfare in the herd, such as poor hygiene, feeding and management of dry or calving cows and sick animals. However, further investigations are required for causal inferences to be established.

Intramuscular fat (IMF) % contributes positively to the juiciness and flavour of lamb and is therefore a useful indicator of eating quality. A rapid, non-destructive method of IMF determination like computed tomography (CT) would enable pre-sorting of carcasses based on IMF% and potential eating quality. Given the loin muscle (longissimus lumborum) is easy to sample, a single measurement at this site would be useful, providing is correlates well to other muscles. To determine the ability of CT to predict IMF%, this study used 400 animals and examined 5 muscles from three sections of the carcass: from the fore-section the m. supraspinatus and m. infraspinatus, from the saddle-section the m. longissimus lumborum and from the hind-section the m. semimembranosus and m. semitendinosus. The average CT pixel density of muscle was negatively associated with IMF% and can be used to predict IMF% although precision in this study was poor. The ability of CT to predict IMF% was greatest in the m. longissimus lumborum (slope −0.07) and smallest in the m. infraspinatus (slope −0.02). The correlation coefficients of IMF% between the five muscles were variable, with the highest correlation coefficients evident between muscles of the fore section (0.67 between the m. supraspinatus and the m. infraspinatus) and the weakest correlations were between the muscle of the fore and hind section. The correlation between the m. longissimus lumborum to the other muscles was fairly consistent with values ranging between 0.34 and 0.40 (partial correlation coefficient). The correlation between the proportion of carcass fat and the IMF% of the five muscles varied and was greatest in the m. longissimus lumborum (0.41).

A 2 x 2 factorial experiment was designed in order to study the effects of feeding level during rearing and of mating policy on the reproductive performance and food intake of first- and second-litter sows. Gilts were offered food during rearing either ad libitum (AL) or at 0·8 of the AL level (R) and served either at first (E1) or third (E3) detected oestrus. A total of 160 out of the 243 animals that started the experiment were culled by the end of the second lactation, with significantly more R than AL animals (71 and 60%, respectively). During the first pregnancy, the R sows gained more live weight (LW) and backfat thickness (BF) than their AL contemporaries (+5 kg and +1.2 mm, respectively) and lost less BF during the first lactation (1.2 mm less). At weaning, no difference remained in LW or BF between AL and R sows (174 kg LW on average). The E3 females gained less LW during both pregnancies compared with those on the E1 treatment, but they remained heavier until the second weaning (208 kg, on average). During the first lactation, R consumed more food during the weeks 2 and 3 (by 0·5 kg/day, on average) than those reared previously on the AL regime, and no difference was observed between E3 and E1 females. No difference in food consumption was noted during parity two. However, when measured over the first two parities, lean animals consumed more food than fat animals. The size and the weight of the litter at birth or at weaning were not influenced by the treatment prior to service. The weaning-to-oestrus interval was longer during parity one than during parity two (5·7 and 5·0 days, respectively; P < 0·01) but it was not affected by feeding or mating treatment.

Factors influencing early development such as birth weight, nest competition, and the diet received during rearing have been proposed as elements conditioning the future reproductive performance of European rabbit (Oryctolagus cuniculus) females. To evaluate their effects, we followed the life of 1513 females from birth to time of death, culling or censoring (animals alive at a fixed date). Between 0 and 63 days of age 353 females died. From the remaining 1160 females, 864 were chosen based on their birth weight to be transferred from the selection to the production farm. At this farm, 431 females received the control diet (184 g of CP, 381 g of NDF and 11.8 MJ of DE per kg DM), while the other 433 received the fibrous diet (134 g of CP, 436 g of NDF and 10.0 MJ of DE per kg DM). Throughout the rearing period, we checked for the individual live weight and body condition (perirenal fat thickness) at first artificial insemination. Reproductive lifespan was defined as the number of days between the first parturition and the time of death, culling or censoring. Birth weight affected the survival of newborn females during lactation and the presence of a milk spot at birth (related to nest competition) increased the survivability of newborns weighing <45 g (P<0.001). Rearing diet altered the growth curve of females and their body condition at first insemination. The diet also altered the relative risk of death during the rearing period, which was lower among females fed on the fibrous diet (−12.5%; P<0.001). Therefore, a higher number of females fed with this diet reached their reproductive life, directly affecting the productivity measured per housed female. Fatter females at first insemination had smaller litter sizes and a higher risk of being culled than lean ones (P<0.05). In general, the fibrous diet reduced the risk of leaving the herd at early rearing, and both birth weight and perirenal fat thickness affected female’s reproductive lifespan. An excess of fat (positive change in one unit of perirenal fat) at their first insemination represented an increased the risk of death or elimination of 13%.

This study investigated some aspects of breeding management in the Italian Heavy Draught Horse breed, aiming at improving its efficiency at stud farm level. A first aim was to evaluate the risk of unsuccessful reproduction in mares after an early (3 years) or normal (4 years) age at first foaling, in interaction with different stud rearing systems. A second objective was the examination of the mean time length in which young 2-year-old stallions maintain a genetic superiority on older proven stallions, identifying a ‘genetic lifespan’ in which young stallions can be safely used for reducing the cost of services. Reproductive performance at first and second foaling of 1513 mares were used. Mares had a normal first foal at 3 (n = 745) or 4 years of age (n = 768) in stud farms on the basis of stable (n = 488), feral (n = 345) or semi-feral (n = 680) rearing systems. Logistic regression analysis was performed by modeling the risk of unsuccessful reproduction in the subsequent season (i.e., results at second foaling), as affected by the interaction of age at first foaling × rearing system (six classes). Genetic lifespan of young stallions was estimated by regressing the least square means from a mixed model analysis for repeated measures of individual differences in ‘total merit’ estimated breeding values (EBVs) between young stallions (mean no. of 45/year) and the mean EBV of all proven stallions in a given year of genetic evaluation (mean no. of 483/year). Young stallions born between 1999 and 2005 were used, following each generation (i.e., birth year) from 2 to 7 subsequent yearly genetic evaluations. In comparison with the best reproductive success of second foaling at 4 years in stable systems, the greatest risk of unsuccessful reproduction was at 3 years in feral (+167%) and 3 years in semi-feral conditions (+91%). Young stallions showed a 0.50 s.d. greater EBV at the first evaluation than proven stallions, with a mean annual decrease in EBV of 0.07 s.d./year on proven stallions. Optimal breeding management could be obtained in stud farms by limiting foaling at 3 years, particularly in feral and semi-feral rearing systems, and using young stallions for 3 to 4 years to maintain a perceptible selection differential with older proven stallions and to reduce cost of services. Later, the selection differential with proven stallions become less consistent and genetic improvement could be slowed down.

This study examined the genetic and phenotypic associations between finisher performance, pre-breeding body condition of the gilt, subsequent lactation feed intake and survival of the primiparous sow to farrow in the second parity. Complete data were available on ∼2200 sows, along with additional cohort and historical performance data. Genetic variation was observed for average lactation feed intake (heritability: 0.18 ± 0.04), with a significant proportion of observed variation in average intake attributable to variation in lactation length. Weight and body condition (fatness) at finishing were very highly correlated genetically (0.89 ± 0.03 and 0.90 ± 0.02) and moderately correlated phenotypically (0.58 ± 0.01 and 0.58 ± 0.01) with weight and body condition before mating. Estimates of genetic (rg) and phenotypic (rp) correlations between feed intake recorded at finishing and average lactation feed intake (LADI) were moderate (rg = 0.26 ± 0.16 and 0.42 ± 0.22) and low (rp = 0.07 ± 0.02 and 0.08 ± 0.03), with rg dependent on the models and data subsets used for lactation intake. Non-unity genetic correlations imply that different genetic control mechanisms regulate feed intake during growth and lactation. Moderate genetic correlations between lactation feed intake with live weight (TWT) or growth rate (TADG) recorded at selection and live weight before mating (0.42 ± 0.11, 0.42 ± 0.11 and 0.37 ± 0.15) were considerably higher than the corresponding phenotypic correlations for LADI with TADG or 29WT (0.09 ± 0.02 and 0.08 ± 0.02). Correlations between fatness at selection (TFAT) or mating (29FT) and LADI were negative but not significantly different from 0. Overall, these data suggest that there is exploitable genetic variation for feed intake during lactation, and that selection is possible if lactation feed intakes are recorded. However, genetic correlations suggest that early growth seems to be related to lactation feed intake capacity. There was generally no strong evidence that selection for lean growth potential in dam lines will substantially diminish sow lactation intake capacity as a correlated response.

Four experiments were carried out to measure the effects of exposure to a cellulase preparation on the degradation characteristics of whole barley straw and its botanical fractions. The effect of chemical pre-treatment (NaOH and H2O2) on treatment with a cellulase preparation and the addition of propionic acid to inhibit loss of dry matter were also studied during the fermentation of ensiled straws. Samples of each preparation were incubated in polyester bags in the rumens of three sheep to estimate degradability. The data were described using the equationp = a + b (1—ec) where p is degradability at time t and a, b and c are constants.

The pH of ensiled straw was consistently decreased (P < 0·01) and the solubility increased (P < 0·01) by treatment with a cellulase preparation and by increasing the period of ensiling. The b values were decreased by increasing the length of the ensiling period (F < 0·01). The increase in the solubility of the treated botanical fractions was particularly apparent for the leaf blades, followed by leaf sheath, with the internodes being least affected (P < 0·01). However, treatment with a cellulase preparation had little or no effect in increasing the potential degradability (a + b) of any botanical fraction. The degradability of the whole plant and botanical fractions of straw increased (P < 0·01) with NaOH treatment and was further improved (P < 0·01) by alkaline H2O2 treatment. The increase was greater in internodes than in leaf sheath (P < 0·01). Treatment with a cellulase preparation and chemical pre-treatment had little or no effect on the 48-h dry-matter loss (DML) and the (a + b) values, but it increased (P < 0·01) the a values and solubility.

DML from straw treated with a cellulase preparation during fermentation decreased (P < 0·01) from about 60 to less than 10 g/kg with 30 g propionic acid added per kg straw to inhibit bacterial activity. The decreased fermentation loss was reflected in an increase in the 48-h DML and potential (a + b) values of straw treated with a cellulase preparation.

Thirty-five gilts grown between 18 and 55 kg live weight were used to examine the effects of feeding fermentable carbohydrate on voluntary food intake, performance, carcass characteristics, and large intestinal growth. Five diets were used. The first diet contained steam-flaked sorghum and a supplement based on animal protein sources and 40 g/kg soya-bean meal (diet SAP). Using this diet as a base, three other diets contained either (i) guar gum, a source of soluble non-starch polysaccharide (NSP) (diet SAP + S-NSP), (ii) Novelose™, a source of resistant starch (RS) (diet SAP + RS), and (Hi) a combination of both S-NSP and RS (diet SAP + S-NSP + RS). The final diet (diet WBL) was based on wheat, barley and Australian sweet lupins. Diets (i), (ii) and (Hi) were formulated such that the concentrations of soluble NSP, oligosaccharide and RS were similar to those contained in diet WBL. There was no relationship (F > 0·05) between voluntary food intake and indices of hind-gut fermentation, although pigs given diets SAP + S-NSP and SAP + S-NSP + RS took longer to reach the slaughter weight of 55 kg (F < 0·001) and converted food less efficiently than pigs given other diets (F < 0·001). An increased intake of S-NSP (R2 = 0·842, P < 0·05) and S-NSP + RS (R2 = 0·805, F < 0·05) was positively correlated to an increased (empty) weight of the large intestine. A significant negative relationship (R2 = 0·78, F < 0·05) existed between the daily intake of S-NSP + RS and dressing proportion, such that each gram increase caused a 0·25 g/kg decrease in the dressing proportion of pigs. No such relationships existed between the daily intake of soluble NSP, insoluble NSP, or RS (P > 0·05) with dressing proportion. These data suggest that the sources of fermentable carbohydrate used in this study, i.e. soluble NSP and RS, may not significantly depress voluntary food intake but can affect performance and have a significant effect on large intestinal growth and dressing proportion.

1. A 2×2×2 factorial experiment was carried out with 8 blocks of 8 early-weaned Friesian male calves on the 8 treatment combinations of the following factors: (A) groundnut meal versus white-fish meal as the major protein source; (B) presence versus absence of antibiotic and (C) restricted versus ad lib. feeding. The experiment was conducted over the live-weight range 55–90 kg.

2. The inclusion of fish meal rather than groundnut meal in the diet resulted in highly significant increases in both rate of gain and feed conversion efficiency (P < 0·001). This effect was most apparent at the higher level of feed intake.

3. The addition of antibiotic to the diet increased rate of gain (P < 0·001) and improved feed conversion ratio (P <0·01). Feed intake was increased slightly but non-significantly (P <0.1) on the ad lib. feeding level as a result of antibiotic supplementation.

4. Feed conversion ratio was lower and feed intake and rate of gain were higher on ad lib. than on restricted feed (P < 0·001 in each instance).

5. There was a significant (P < 0·05) level of feeding × antibiotic interaction, indicating that the difference between restricted and ad lib. feeding was greater in the presence than in the absence of antibiotic. No other significant interactions were observed.

6. The use of fish meal in preference to groundnut meal is shown to be justified on economic grounds.

The objective of the present study was to estimate heritabilities as well as genetic and phenotypic correlations for egg weight, specific gravity, shape index, shell ratio, egg shell strength, egg length, egg width and shell weight in Japanese quail eggs. External egg quality traits were measured on 5864 eggs of 934 female quails from a dam line selected for two generations. Within the Bayesian framework, using Gibbs Sampling algorithm, a multivariate animal model was applied to estimate heritabilities and genetic correlations for external egg quality traits. The heritability estimates for external egg quality traits were moderate to high and ranged from 0.29 to 0.81. The heritability estimates for egg and shell weight of 0.81 and 0.76 were fairly high. The genetic and phenotypic correlations between egg shell strength with specific gravity, shell ratio and shell weight ranging from 0.55 to 0.79 were relatively high. It can be concluded that it is possible to determine egg shell quality using the egg specific gravity values utilizing its high heritability and fairly high positive correlation with most of the egg shell quality traits. As a result, egg specific gravity may be the choice of selection criterion rather than other external egg traits for genetic improvement of egg shell quality in Japanese quails.

Crop–livestock production is claimed more sustainable than specialized production systems. However, the presence of controversial studies suggests that there must be conditions of mixing crop and livestock productions to allow for higher sustainable performances. Whereas previous studies focused on the impact of crop–livestock interactions on performances, we posit here that crop–livestock organization is a key determinant of farming system sustainability. Crop–livestock organization refers to the percentage of the agricultural area that is dedicated to each production. Our objective is to investigate if crop–livestock organization has both a direct and an indirect impact on mixed crop–livestock (MC–L) sustainability. In that objective, we build a whole-farm model parametrized on representative French sheep and crop farming systems in plain areas (Vienne, France). This model permits simulating contrasted MC–L systems and their subsequent sustainability through the following indicators of performance: farm income, production, N balance, greenhouse gas (GHG) emissions (/kg product) and MJ consumption (/kg product). Two MC–L systems were simulated with contrasted crop–livestock organizations (MC20–L80: 20% of crops; MC80–L20: 80% of crops). A first scenario – constraining no crop–livestock interactions in both MC–L systems – permits highlighting that crop–livestock organization has a significant direct impact on performances that implies trade-offs between objectives of sustainability. Indeed, the MC80–L20 system is showing higher performances for farm income (+44%), livestock production (+18%) and crop GHG emissions (−14%) whereas the MC20–L80 system has a better N balance (−53%) and a lower livestock MJ consumption (−9%). A second scenario – allowing for crop–livestock interactions in both MC20–L80 and MC80–L20 systems – stated that crop–livestock organization has a significant indirect impact on performances. Indeed, even if crop–livestock interactions permit improving performances, crop–livestock organization influences the capacity of MC–L systems to benefit from crop–livestock interactions. As a consequence, we observed a decreasing performance trade-off between MC–L systems for farm income (−4%) and crop GHG emissions (−10%) whereas the gap increases for nitrogen balance (+23%), livestock production (+6%) – MJ consumption (+16%) – GHG emissions (+5%) and crop MJ consumption (+5%). However, the indirect impact of crop–livestock organization doesn’t reverse the trend of trade-offs between objectives of sustainability determined by the direct impact of crop–livestock organization. As a conclusion, crop–livestock organization is a key factor that has to be taken into account when studying the sustainability of mixed crop–livestock systems.

The behaviour of 12 Merino and 12 Wiltshire Horn ewes was observed on the day they werefirstintroduced together into a 0·85 ha paddock and over the following 9 days. Neither breed group had associated with sheep of the other group previously. Both groups formed and maintained their own strong social groupings, and despite the small area of pasture and enforced close association each day, no significant integration of the groups was observed.

Heritability or the genetic regression of one trait on another, for example live-weight gain in field v. performance test station conditions, can be estimated efficiently by rearing offspring only from high- and low-ranking individuals, and estimating the regression of offspring on parent performance. Formulae are given for the optimum proportion of available animals to select as parents when the relative numbers of individuals in the parent and progeny generation are fixed. Although the optimum depends on the value of the parameter to be estimated, the designs are very robust to poor estimates.