Production and endoparasitism of first grazing season Holstein heifers and steers were investigated over two grazing seasons. Studies were conducted on low-lying peaty soil. In year 2000, 40 animals were included in a 2×2 factorial, replicated experiment with two sexes (steers v. heifers) and two stocking rates (SR): normal v. low (840 v. 420 kg live weight per ha at turn-out) in a set stocking grazing system. Mean grass heights over the entire season were 6·3±4·8 cm (mean±s.d.) at normal SR and 9·8±6·1 cm at low SR. Mean daily live-weight gain during grazing was significantly (P<0·001) lower at normal SR (256±147 g) compared with low (468±142 g) but sex did not significantly affect the daily gain. Serum pepsinogen levels, indicating uptake of gastric nematodes, were higher at normal SR and consistently higher in steers compared with heifers, although not significantly. In 2001 the experiment included 80 animals in a 2×2 factorial experiment with two sexes (steers v. heifers), two grazing systems (set stocking and two-paddock rotation) and four replicates. Pasture quality was low, 570 g digestible organic matter per kg organic matter and 139 g crude protein per kg dry matter on average, independent of grazing system. Mean daily live-weight gain was not significantly affected by grazing system. A tendency (P=0·07) to lower daily gain for the heifers than for steers was observed (427±161 g v. 474±138 g). Lower levels of pasture contamination with parasites were observed in the paddocks without grazing up to mid July but otherwise rotation did not prevent parasite infections. It is concluded that first grazing season steers and heifers have the same potential for growth when grazing marginal areas with low pasture quality. Set stocking or the two-paddock rotation scheme did not affect productivity or level of parasite infection at the end of season. Parasite infections became a problem at high SR. SR is an important factor for both daily live-weight gain per animal and total production per ha. However, due to the very heterogeneous structure of marginal areas there is a need for other indicators than kg live weight per ha at turn-out in order to define a clear relationship between stocking rate and production.

The effect of certain simple and cost-effective processing methods on the nutritional and anti-nutritional properties of seed materials of an under-utilized food legume, Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker ex Burck (velvet bean, VB), collected from Valanadu, Kerala, India was analyzed in experiment 1. The raw VB seeds were found to contain appreciable levels of crude protein (263.2 g/kg dry matter (DM)); ether extract (79.6 g/kg DM); crude fiber (95.8 g/kg DM) and ash content (38.4 g/kg DM). Among the different treatments used, soaking in sodium bicarbonate solution + autoclaving was more effective in reducing maximum levels of various anti-nutritional compounds of VB seeds. Furthermore, in experiment 2, the effect of inclusion of different levels of velvet bean meal (VBM; subjected to soaking in sodium bicarbonate solution + autoclaving) as an alternative protein source in poultry feed on the growth performance of commercial-type broiler birds was investigated. The results indicate that the inclusion of VBM up to the 40% level exhibited better growth performance of the broiler birds such as feed intake, body weight gain, feed conversion ratio and protein efficiency ratio in both the starter and finisher phases.

The aim of this paper was to validate an alternative multi-criteria evaluation system to assess animal welfare on farms based on the Welfare Quality® (WQ) project, using an example of welfare assessment of growing pigs. This alternative methodology aimed to be more transparent for stakeholders and more flexible than the methodology proposed by WQ. The WQ assessment protocol for growing pigs was implemented to collect data in different farms in Schleswig-Holstein, Germany. In total, 44 observations were carried out. The aggregation system proposed in the WQ protocol follows a three-step aggregation process. Measures are aggregated into criteria, criteria into principles and principles into an overall assessment. This study focussed on the first two steps of the aggregation. Multi-attribute utility theory (MAUT) was used to produce a value of welfare for each criterion and principle. The utility functions and the aggregation function were constructed in two separated steps. The MACBETH (Measuring Attractiveness by a Categorical-Based Evaluation Technique) method was used for utility function determination and the Choquet integral (CI) was used as an aggregation operator. The WQ decision-makers’ preferences were fitted in order to construct the utility functions and to determine the CI parameters. The validation of the MAUT model was divided into two steps, first, the results of the model were compared with the results of the WQ project at criteria and principle level, and second, a sensitivity analysis of our model was carried out to demonstrate the relative importance of welfare measures in the different steps of the multi-criteria aggregation process. Using the MAUT, similar results were obtained to those obtained when applying the WQ protocol aggregation methods, both at criteria and principle level. Thus, this model could be implemented to produce an overall assessment of animal welfare in the context of the WQ protocol for growing pigs. Furthermore, this methodology could also be used as a framework in order to produce an overall assessment of welfare for other livestock species. Two main findings are obtained from the sensitivity analysis, first, a limited number of measures had a strong influence on improving or worsening the level of welfare at criteria level and second, the MAUT model was not very sensitive to an improvement in or a worsening of single welfare measures at principle level. The use of weighted sums and the conversion of disease measures into ordinal scores should be reconsidered.

Forty Large White ♂ × (Large White (f × Landrace ♀) pre-pubertal gilts were used to study the influence of five different doses of parenteral oestradiol benzoate (OB) on the attainment of puberty. Five gilts from eight litters were treated at 140 days of age with either 5, 10, 15, 20 or 25 μg OB per kg body weight (BW). The doses were split equally into three bolus injections given on consecutive days. Daily boar contact commenced on the day that the first oestrogen injection was given and continued until the gilts were mated. All gilts were slaughtered at either 20 days post coitum or at 235 days of age for those gilts not exhibiting a second oestrus.

The numbers of gilts which ovulated within 10 days after OB injection were: 5/8, 7/8, 8/8, 6/8 and 5/8 for treatments 5 ng/kg BW through to 25 fig/kg BW, respectively. These differences were not significant (P > 0·05). The duration of behavioural oestrus after OB injection was positively correlated to the dose of oestrogen administered (r = 0·98, P < 0·01). There were no significant differences in age at puberty between treatments, and no significant differences were found in the subsequent reproductive performance.

The effects of two levels of energy intake, ad libitum and 80% of ad libitum, of diethylstilboestrol implantation and no such treatment, and of two slaughter weights (‘450’ and ‘490’ kg), on the performance of Israeli-Friesian intact male cattle were studied.

Average daily gain was 1130 g and 959 g and daily carcass gain was 630 g and 553 g for animals on ad libitum and 80% of ad libitum energy intake, respectively. Average daily gain was 1038 g and 944 g and daily carcass gain was 595 g and 562 g, for diethylstilboestrol-treated and untreated animals, respectively. Slaughter weight had little effect on rate of gain.

The differences in conversion ratio of ME into live weight between treatments were small. Diethylstilboestrol-treated animals were slightly more efficient.

The non-implanted animals on the restricted plane of nutrition and which had been slaughtered at ‘490’ kg had a significantly higher dressing percentage, a higher percentage of fat trim and less bone than animals slaughtered at ‘450’ kg body weight on both levels of nutrition.

Among the diethylstilboestrol-implanted male calves, however, the animals fed at 80% of ad libitum feed and killed at ‘450’ or ‘490’ kg live weight had significantly more fat trim in the carcass and less bone than the animals fed ad libitum.

A total of 56 sheep, 28 Clun and 28 Southdown were slaughtered, five of each breed, at birth, 50, 100, 150 and 200 days and three of each breed at 415 days of age. The left half of each carcass was separated anatomically into individual muscles, bones and fat depots. For the purposes of analysis, individual muscles were assigned to one of eight muscle groups, depending upon their anatomical location.

The relative growth of some individual muscles was found to change over this age range, as indicated by a significant squared term in the quadratic allometric equation: this was true for proportionately 0·33 of the muscles in Clun and for proportionately 0·44 of those in Southdown, accounting for proportionately 0·33 and 0·47 of total muscle weight in Clun and Southdown respectively.

Principal components analysis (PCA) was used to derive the multivariate analogue of the quadratic part of quadratic allometry: the sign of the loading on the second principal component had the same sign as the change observed in bq, the quadratic relative growth coefficient. Thus, PCA offers the potential to identify simultaneously, and independently of shape or conformation, all those muscles whose relative growth coefficients change over the period examined. It could be applied successfully to breed comparisons of conformation.

The cumulative effects of changing relative growth rates of muscles were small. Muscle weight distribution appears to be almost fixed within the first few weeks after birth. Despite their differences in conformation and mature size, Clun and Southdown lambs had similar distributions of muscle weight at the same age; the high valued muscles constituted 513·8 g/kg total muscle in Clun and 514·7 g/kg total muscle in Southdown lambs at 200 days of age.

Producing organic fish diets requires that the use of both fishmeal and fish oil (FO) be minimized and replaced by sustainable, organic sources. The purpose of the present study was to replace FO with organic oils and evaluate the effects on feed intake, feed conversion ratio (FCR), daily specific growth rate (SGR) and nutrient digestibility in diets in which fishmeal protein was partly substituted by organic plant protein concentrates. It is prohibited to add antioxidants to organic oils, and therefore the effects of force-oxidizing the oils (including FO) on feed intake and nutrient digestibility was furthermore examined. Four organic oils with either a relatively high or low content of polyunsaturated fatty acids were considered: linseed oil, rapeseed oil, sunflower oil and grapeseed oil. Substituting FO with organic oils did not affect feed intake (P > 0.05), FCR or SGR (P > 0.05) despite very different dietary fatty acid profiles. All organic plant oils had a positive effect on apparent lipid digestibility compared with the FO diet (P < 0.05), whereas there were no effects on the apparent digestibility of other macronutrients when compared with the FO diet (P > 0.05). Organic vegetable oils did not undergo auto-oxidation as opposed to the FO, and the FO diet consequently had a significantly negative effect on the apparent lipid digestibility. Feed intake was not affected by oxidation of any oils. In conclusion, the study demonstrated that it is possible to fully substitute FO with plant-based organic oils without negatively affecting nutrient digestibility and growth performance. Furthermore, plant-based organic oils are less likely to oxidize than FOs, prolonging the shelf life of such organic diets.

Sensor feeding is a liquid feeding system for fattening pigs that is operated with a restricted animal/feeding-place ratio (AFR). The aim of the present study was to quantify the effect of three different AFRs (4:1, 7:1 and 13:1, calculated with a feeding space of 33 cm per animal) on the performance and behaviour of fattening pigs (mean initial weight 26·3 (s.d. 3·3) kg, live weight at slaughter 102 (s.d. 5) kg). The pigs were housed in groups of 40 and each AFR was tested with seven groups (21 groups in total). The daily weight gain of the individual pigs was calculated from the beginning of the experiments until slaughter. Additionally, the lean meat percentage was recorded (AutoFOM). Feeding behaviour was observed by means of 24-h video recording at the ages of 14 and 17 weeks with scan sampling every 5 min. The daily weight gain decreased with increasing AFR ( P<0·01) and females had lower weight gains than barrows ( P<0·001). The lean meat proportion was influenced by the AFR ( P<0·01) and sex of the pigs ( P<0·001). Proportions were highest with the AFR 13:1 and in females. The average number of pigs feeding simultaneously was highest for the AFR of 4:1 ( P<0·01). Moreover, the ingestion rate per day (kg/min) increased with increasing AFR ( P<0·05). The average number of pigs waiting behind other pigs feeding at the trough was highest with the AFR 13:1 ( P<0·001).In conclusion, growth performance and pig behaviour were negatively affected by an AFR of 13:1, which cannot be recommended for use with this feeding system. With an AFR of 4:1 lean meat values were low.

Predictions of two models were compared. The models relate ovulation rate (OR) and prenatal survival (PS) to litter size (LS): the uterine capacity model (UCM), where maximum LS is limited by uterine capacity (UC), and the threshold model (TM) whereby PS is modelled as a binary threshold trait. Records were simulated according to both models using statistics from Trench Large White gilts. Both models were able to reproduce closely the observed curvilinear relationship between OR and LS, with LS reaching a plateau at high OR. Several genetic correlations (ρg) fulfilling the conditions h20R = 0·34 and h2LS = 0·12 (the residual maximum likelihood estimates in the population) were studied by means of stochastic computer simulation. The genetic correlation between OR and LS was very sensitive to changes in h2uc, whereas ρgLS,PS was always positive, and ρgOR,PS was always negative. The correlation between PS and UC was larger than 0·90, except for very small h2UC This suggests that genes affecting PS have a strong influence on UC and that PS can be a good indirect criterion to select for UC. Both models predicted that the advantage of an index combining OR and LS with respect to direct selection on LS diminishes in successive generations of selection and that the size of the experiment needed to detect significant differences is very large. Records were also simulated by halving the mean and variance of UC, so as to mimic unilateral hysterectomy-ovariectomy (UHO). If the UHO treatment results in halving UC, LS of UHO females should behave very much as half the UC of intact females.

The incidence of oestrus in 603 Hereford heifers with a mean age of 545 days (range 515 to 575) was related to live weight (range 130 to 376 kg). Observations were ranked in order of ascending live weight and the percentage of heifers showing oestrus was calculated for consecutive 10 kg increments in live weight from 130 to 380 kg. The percentage showing oestrus was subjected to the probit transformation (Y, probit units) and was then related to live weight (X, kg):

It was predicted that 50% of the heifers showed oestrus at 231 ± 1 kg, and that 5% and 95% showed oestrus at 187 and 280 kg respectively.

The objective of this study was to evaluate the use of oat hulls (OH) to substitute traditional fiber (a mixture of rice hulls and mugwort (RHM) leaf) in the diets of fattening rabbits by examining on its effect on the growth performance, coefficient of total tract apparent digestibility (CTTAD) of nutrients, gastrointestinal tract development, cecum fermentation and carcass traits. A total of 160 mixed sex Hyla commercial meat rabbits (40/treatment) were used to study the effects of including OH in the diet from 30 to 80 days of age. A control diet based on RHM and containing 175.2 g crude fiber and 169.7 g CP/kg was included. Growth performance and CTTAD of nutrients were recorded from day 35 to day 80 and day 74 to day 80, respectively, whereas gastrointestinal tract development, cecum fermentation and carcass traits were determined at day 80. Increasing concentrations of OH in the diet increased average daily feed intake (P=0.0018), but have no effects on average daily gain and feed conversion ratio (P>0.05). Moreover, the 150 g/kg OH diet decreased the relative weight of full cecum and cecal content (P<0.05), but did not affect other gastrointestinal organs. The CTTAD of NDF and gross energy decreased with the inclusion of OH (P<0.05). No effects of CTTAD of ADF, ADL, dry matter, CP and ether extract were observed (P>0.05). The concentrations of total volatile fatty acid, acetic and butyric acids were greater in rabbits fed the lower levels of OH (0 to 100 g/kg) compared with higher rate (150 g/kg; P<0.05). However, the proportions of acetic, propionic and butyric acids were not affected by treatments (P>0.05). Furthermore, no significant effect on the ratios of acetic/(propionic+butyric) was observed (P>0.05). Hot carcass weight, pH (45 min, 24 h), lightness, redness, yellowness, 24-h drip loss of longissimus lumborum muscles were not affected by diet OH (P>0.05). However, dressing out percentage increased with higher (150 g/kg) inclusion of OH. It is concluded that OH can be included in rabbit diets at levels up to 100 g/kg, but negative effect on digestion and performance were observed with the increasing of OH (150 g/kg).

Alpine transhumance or droving livestock to mountainous areas during summer months is highly relevant for Austrian agriculture but also for other countries in Alpine regions. Access of rearing stock to mountain pastures is often claimed to be beneficial with respect to health and longevity, but the robust evidence is scarce. Therefore, its effect was tested by including it in the routine genetic evaluation data set for longevity. Alpine transhumance records from 2004 to 2013 were used. After several plausibility checks and restriction to animals with sire and dam known, records of 871 287 dual-purpose Fleckvieh cows sired by 9953 bulls were available. Data were analysed by means of survival analysis accounting for the time-dependent fixed effects of region-year-season, relative performance within herd, change of herd size, and Alpine pasturing of cows, the fixed effects age at first calving and Alpine pasturing of rearing stock, the random time-dependent effect of herd-year and the random genetic effects of sire and maternal grandsire. Fleckvieh cows that had access to Alpine pasture during their rearing period at least once for a minimum of 60 days had functional longevity that was nearly 2 months prolonged compared with cows that had always stayed on the farms as calves or heifers. In a more detailed analysis, the lowest relative culling risk among the significant estimates was observed for cows that had been Alpine pastured in years 1 and 3; it was about 15% below that of cows that never had access to mountain grazing. Evidence for the beneficial effect of Alpine pasturing of rearing stock on the animals’ later fitness, indicated by longevity, could thus be provided.

Data from a large controlled experiment to investigate the effect of level of nutrition on reproductive performance were used to assess the value of production and blood measures as indicators of energy status in lactating dairy heifers. Live-weight change showed the strongest and most consistent relationship to mean energy balance (the difference between metabolizable energy intake and that used for milk production and maintenance) (P < 0·01 to P < 0·001). Body-condition score at a particular time was more closely related to mean energy balance in the preceding 4-week period (P < 0·05) than current energy balance. There was also a lag in the relationship between energy balance and live-weight change and mean body-condition score. Ultrasonic back fat measurements were significantly correlated with both loin and tailhead body-condition score (P < 0·001) but were more strongly related to mean energy balance in the preceding period (P < 0·05 to P < 0·001) than the body-condition scores.

Blood samples were taken from all heifers 2 weeks before calving and 1, 5, 9, 13 and 18 weeks after calving and were analysed for 13 constituents. Concentrations of blood metabolites did not show consistently strong correlations with mean energy balance. The only blood metabolite to be measurably affected by the nutritional treatments applied in lactation was β-hydroxybutyrate.

At best, combinations of production measures and blood metabolites were only able to predict the mean daily energy balance with a 95% confidence interval of ±20 MJ for an individual animal although this confidence interval was reduced to ±3 MJ for 100 animals.

Serum thyroxine levels were observed in 15 Soay ewes and seven rams for 1 year. From June to November the ewes had thyroxine concentrations 40% higher than the rams, and the level in both sexes increased from December to May, demonstrating a seasonal cycle in thyroxine level that could be associated with the annual wool growth cycle. To hasten the onset of wool follicle activity, nine Wiltshire sheep were given thyroxine implants in autumn when the follicles normally become inactive, but only a slight increase in follicle activity occurred. Eighteen Soay sheep were given thiouracil orally for 1 month in spring in an attempt to block a possible seasonal increase in thyroxine secretion that might be associated with the normal regrowth of wool, but no retardation of the spring regrowth was obtained.

Breed and crossbreeding significantly affected variation in 10 fleece, follicle density and fibre diameter traits in 12-week-old lambs. The breeds involved were the Scottish Blackface, South Country Cheviot, Welsh Mountain, Lincoln Longwool, Southdown and Tasmanian Merino, but the last only by rams.

The Southdown came closest to the Merino in affecting density and diameter traits although the Merino crosses remained clearly distinguishable by their high follicle density. The Lincoln and Blackface crosses were notable for their long fibres and the Blackface crosses also had the least dense follicle and coarsest primary fibres. The coarsest secondary fibres were from Lincoln and Cheviot crosses. Heterosis estimates were obtained for crosses involving the Blackface, Cheviot, Welsh and Lincoln breeds. Significant heterosis was present in a wide range of traits but was not apparent in all crosses. Maternal differences were evident for many of the traits but with density these differences were apparently related to maternal effects on live weight of the lamb. The sex of the lamb, its birth type and rearing and its 12-week live weight significantly affected many of the traits.

Among breeds and crosses a strong relationship was found between fibre density and average fibre diameter. The relationship suggested that breed variation in total fibre area per unit area of skin was small compared with the breed variation in its components. Fleece weight per unit area was most closely related to mean fibre length.

An experiment was conducted to investigate the effect of arginine on feed intake regulation. One hundred and twenty six 1-day-old male White Pekin ducks (Anas platyrhynchos domestica) were randomly were allotted to one of two dietary treatments. The birds were fed diets containing 0.71% (deficient) or 1.27% (sufficient) arginine for 3 weeks. At 21 days of age, feed intake was determined and hypothalamic protein profiles were analyzed using isobaric tags for relative and absolute quantification technique. The birds fed with arginine-deficient diet had a lower final live BW and cumulative feed intake (P<0.01) than those fed with arginine-sufficient diet. A total of 16 proteins were identified in the hypothalamus with >1.5-fold expressional changes between arginine-deficient and -sufficient dietary treatments. Nine of these proteins were upregulated and seven of them were downregulated. The identified proteins could be regrouped into six categories: protein processing, carbohydrate metabolism and energy production, transporter, cytoskeleton, immunity and neuronal development. Dietary arginine deficiency decreased expression of proteins involved in energy production (glycine amidinotransferase, aldolase B fructose-bisphosphate, aconitase, transaldolase, 6-phosphofructokinase type C-like) and oxygen transportation (haemoglobin subunit α expression). The proteomic alterations described here provides valuable insights into the interactions of arginine with appetite.

Females of four strains of commercial turkeys, including one large strain with a characteristically high rate of oviducal prolapse, were given food either ad libitum or controlled to reach proportionately 0·8 or 0·6 of the body weight of birds fed ad libitum at 24 weeks of age. Two pens of five turkeys from each treatment were photostimulated at 24 and 30 weeks of age. Each turkey was autopsied after it had laid its first egg. The relationships between egg weight and body weight, and between the weight of abdominal fat, diameter of the vent and distance between the pubic bones and egg weight were studied by regression analysis. Egg weight was a function of body weight raised to the power 0·29 which was significantly different from the allometric relationship for Galliform species of 0·64. There was no evidence that differences existed in the quantity of abdominal fat which could impede oviposition and contribute to oviducal prolapse. There were strain differences in the diameter of the vent and distance between the pubic bones in relation to egg weight but the smallest and largest strains were similar. It was concluded that artificial selection had changed the species relationship between egg weight and body mass and that the susceptibility to oviducal prolapse in sire line turkeys was probably physiological in origin.

A flock of Cheviot ewes carrying the Thoka gene for fecundity was established in southern Scotland through the importation of frozen semen from two Icelandic rams. Ewes considered to be probable carriers of the Thoka gene were identified on the basis of measurements of ovulation rate as juveniles at 1·5 years of age and again as adults. Analysis of 3 years' records of 8926 Cheviot lambings and lambings of 351 Icelandic × Cheviot ewes considered to be probable carriers showed that fecundity increased with age in both genotypes, the number of lambs born per ewe mated being 1·07, 1·19, 1·31 and 1·41 in the Cheviots and 1·55, 1·74, 2·33 and 2·30 in the Icelandic-Cheviot crosses at first to fourth lambings respectively. The apparent effect of the crossbreeding on fecundity thus also increased with age, values at first to fourth lambings being 0·48, 0·55, 1·02 and 0·89 lambs per ewe mated, giving a weighted mean value of 0·61 (1·20 v. 1·81 lambs per ewe mated in Cheviot and Icelandic × Cheviot ewes respectively). There was a positive effect of the proportion of Icelandic ancestry on the number of lambs born per ewe mated and thus the observed increases in fecundity, although attributed principally to the effects of the Thoka gene, are also due in part to other genetic factors introduced from the Icelandic sheep in the crossbreeding programme. Lamb mortality to 6 weeks of age was only marginally higher in Icelandic × Cheviots (0·10) than in Cheviots (0·08). The increase in fecundity was achieved without an excessive proportion of large litters (<0·02 of probable carriers gave birth to quadruplets). The results demonstrate that the introduction of the Thoka gene to breeds such as the Cheviot can increase fecundity and hence the potential for more efficient lamb production.

One gilt from each of 24 littermate trios was assigned at birth to one of three treatments which were to adjust litter size to six, nine or 12 piglets. Plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured before and after stimulation with 1 ng gonadotrophin-releasing hormone (GnRH) per kg body weight at 55 and 140 days of age. At 150 days, oestrogen was administered and ovarian and uterine responses were measured at slaughter on day 160.

Litter size significantly modified pre-weaning growth rate (P < 0·01) but did not influence gonadotrophin secretion or sexual maturity at slaughter. The family of origin significantly influenced ovarian and uterine development (P < 0·05) and the LH and FSH responses to GnRH at 55 days (P < 0·05). Family size (P < 0·01) and sex ratio of the litter at birth (P < 0·05) also influenced the ovarian response to oestrogen treatment. Significant sire effects on ovarian and uterine development were established (P < 0·05); for the progeny of individual boars significant differences in the response to oestrogen were associated with significant differences in growth rate (P < 0·001).

Variations in family birth and litter weaning weights were negatively correlated with ovarian and uterine development (P < 0·05), whereas all measures of growth from weaning to slaughter were significantly and positively correlated with sexual maturity at slaughter (P < 0·05).

Basal FSH and the responses of both LH and FSH to GnRH at 55 days were correlated with growth rate at day 55 (P < 0·05). Basal LH and FSH at day 140 were correlated with ovarian and uterine development at day 160 (P < 0·05).

Despite much discussion on the use of simple profit equations to estimate economic weights, no study appears to have tested the accuracy of this method. This paper carries out such a test from the viewpoint of the individual farmer by comparing economic weights calculated in the normal way with results gained from a more empirically acceptable, non-linear equation. Although the study concludes that simple profit equations are likely to be sufficiently accurate in most circumstances, further consideration needs to be given to a series of time periods and the industry and economy at large.