Both milk production (MP) and conception rate (CR) of primi- and multiparous cows (P+M) in Israel are characterized by the same summer-autumn trough and winter-spring peak. Although there is no causal link between CR and MP (a simulation-model study explained the connection), monthly CR determines the number of dry cows 7 months later, at 2 months pre-calving. Inevitably, when the number of dry cows is low, MP is high, and vice versa.

Replacement heifers (RH) in Israel have a consistently high (64%) CR throughout the year. The same simulation model was used to investigate the effect of manipulated RH breeding on the herd MP pattern. When RH breeding was confined to the 3-month July to September (J-S) period during which CR is lowest for post-partum P+Ms, the monthly MP pattern in an otherwise year-round breeding dairy herd was the diametric opposite of the one produced by all-year RH breeding. When a uniform monthly quota was set for RH and P+M conceptions, and monthly RH conceptions were restricted to complement monthly P+M conceptions, the herd MP pattern became almost level. There did not appear to be any economic penalty attached to the planned RH conception system.

In practice it will not be possible to adhere to a strict monthly quota of conceptions, since there is a 1 to 2 month lag between insemination and confirmed conception. Estimates of individual farm monthly CR could be used, where available. Alternatively, if 40% of all RH inseminations were performed in J-S, the MP curve would be much flatter than under the present non-planned system of RH insemination.

Twenty-four Friesian dairy cows were divided into two groups of 12 between 12 and 18 weeks prior to calving and fed to achieve condition scores at calving of 3·2 (F) or 2·3 (T). For the first 11 weeks of lactation, six cows from each group (H) were given daily 9 kg of a high-fat compound (acid ether extract (AEE) 96 g/kg dry matter (DM)), 3 kg molassed sugar-beet pulp and hay ad libitum. The other six cows in each group (L) were given 10 kg of a low-fat compound (AEE 29 g/kg DM), 2 kg sugar-beet pulp and hay ad libitum. Allowances of compound and sugar-beet pulp were designed to provide equal amounts of energy, neutral-detergent fibre and protein. The fat source used in compound H was a calcium salt of palm acid oil (Megalac®).

DM intake was not affected by treatment but fat intake was significantly higher on diet H (P < 0·001). Group TH had higher intakes of digestible energy (DE) than group FH (249 v. 229 MJ/day; P < 0·05), but condition at calving did not affect DE intake with diet L (FL = 230, TL = 233 MJ/day). Milk yield was not significantly affected by treatment, although cows in group TL tended to yield less milk than other groups (28·3, 27·3, 28·0 and 24·3 kg/day for FH, FL, TH and TL respectively). The concentration of milk fat was higher and of milk protein lower with diet H compared with diet L (milk fat 48·1, 42·2, 42·9 and 39·6; milk protein 28·0, 31·0, 28·4 and 30·5 g/kg for FH, FL, TH and TL respectively). Loss of condition score was greater for cows in group F (0·65 units) than for those in group T (0·04 units). Within group F, loss of condition tended to be greater with diet L.

It is concluded that the increased intake of fat with diet H tended to decrease loss of condition in cows that were fat at calving but increase milk yield in cows that were thin at calving. It also tended to increase milk fat concentration but decreased milk protein concentration.

Daily partial milk yield of Sanga cows in 13 smallholder agropastoralist herds at two locations on the Accra Plains was recorded through monthly sampling. Estimates of mean daily partial milk yield and milk composition were computed from 1266 observations. The unadjusted mean daily partial milk yield was 875 (s.e. 11) g. The composition of milk: total solids (TS), fat (F) and solid-not-fat (SNF) were 131 (s.e. 14), 41 (s.e. 11) and 90 (s.e. 7) g/kg respectively. Least squares estimate of mean daily partial milk yield were 808·2 and 462·4 g with average s.e. of 41·8 for wet and dry season respectively. The wet and dry season differences in daily partial milk yield, TS and F were highly significant (P < 0·01). Seasonal difference in SNF was not significant.

Herd difference in partial milk yield, TS, F and SNF were highly significant (P < 0·02). There were no significant effects of location on daily partial milk yield and SNF, although location effects on F and TS were significant (P < 0·05). The highest milk yield was observed in cows in third lactation and the lowest in cows in seventh lactation (P < 0·01). Daily partial milk yield peaked in the 3rd month of lactation. On average, lactation length was 210 to 240 days. Both linear and quadratic effects of stage of lactation were highly significant (P < 0·01). Lactation curve parameters for partially milked cows were also estimated. The implications of the results for milk production in sub-Saharan Africa were discussed.

The performance of Hereford × Friesian calves sired by Hereford bulls selected for either lean growth rate (LGR) or lean food conversion ratio (LFCR), or by unselected Hereford bulls, was evaluated on 327 calves on three farms over 2 years. Animals started test at 130 days of age on average and remained on test for approximately 300 days, whereupon all animals were slaughtered and carcass dissections were undertaken. Individual food intake was measured on tioo of the farms (189 animals), but only intake per pen of animals was measured on the third farm and individual food intake had to be estimated. LGR, LFCR and other traits describing performance were calculated from the growth, food intake and carcass composition data.

If no breed or environment interactions exist it is expected that proportionately 0-5 of the genetic differences between selected and control line bulls would be transmitted to their offspring. For the LGR and LFCR line bulls these values were 0·38 and 0·44, respectively, however the LGR value had a much smaller confidence interval. Genetic correlations derived from regressing breeding values predicted from offspring performance on breeding values predicted from the bulk's own performance in the selection experiment were 0·62 (s.e. 0·28) and 0·96 (s.e. 0·28) for LGR and LFCR, respectively. Heritabilities were: live-weight gain on test, 0·27; daily gain, 0·48; food intake, 0·06; food conversion ratio, 0·46; predicted carcass lean content, 0·10; killing-out proportion, 0·10; LGR, 0·36 and LFCR, 0·48.

Two trials, involving a total of 1006 Mule ewes and 1862 Suffolk-× ewes, were conducted to investigate the ability of implantation with melatonin to induce early breeding in lowland sheep flocks. Dates of implantation ranged from mid May to late June for Suffolk-× flocks and mid May to early July for Mule flocks.

From the mating patterns obtained it is suggested that the optimum implantation date is mid May to mid June for Suffolk-× ewes and mid June to mid July for Mule-type ewes.

Melatonin treatment also significantly increased the mean litter size per ewe exposed to the ram (resulting from a 6-week mating period) when the data were pooled across flocks, but the magnitude of this effect varied across flocks. Part of this overall mean increase in Mule ewes (+0·84 and +0·50 extra lambs per ewe in trials 1 and 2 respectively) was due to an increase in the proportion of ewes mating and lambing and part of it (+0·13 and +0·17 extra lambs per ewe, respectively) was due to an increase in litter size per ewe pregnant. In the Suffolk-× ewes there was evidence that the overall mean benefit following implantation with two implants (+0·31 extra lambs per ewe) was greater than that following implantation with one implant (+0·14 extra lambs per ewe), with all of the increase at the lower dose level and +0·21 extra lambs per ewe at the higher dose being due to an increase in litter size per ewe pregnant.

An experiment was conducted to investigate the effects of the length of the interval between implantation with melatonin and ram introduction on mating patterns, and to investigate the effects of melatonin on ovulation rate and litter size in Mule ewes.

Increasing the interval from treatment to ram introduction from 4 to 6 weeks was associated with a progressive and significant reduction in the time from ram introduction to mating as well as a reduction in the spread of mating across the group.

Melatonin resulted in a significant and consistent increase in ovulation rate at first oestrus (+0·44 to +0·48 ovulations per ewe) across the three treated groups, although the increase in litter size (+0·19 to +0·36) was more variable.

It is concluded that melatonin influences the pattern of mating and increases litter size in ewes and that the increase in litter size is accounted for by an induced increase in ovulation rate.

Fifty-six individually penned pregnant ewes were offered silage ad libitum with wheat or barley in a replicated experiment. Each of these cereals was either unprocessed or processed by rolling or milling and was offered at 300 g/day from 6 weeks before lambing and at 600 g/day from 3 weeks before lambing. Five and 2 weeks before lambing, total faeces were collected over 6-day periods. On average proportionately 0·18 of the unprocessed wheat and 0·20 of the unprocessed barley consumed was recovered as intact grain in the faeces. Mean digestibility of the organic matter in the complete diet increased from 726 g/kg on whole to 748 g/kg on rolled and 759 g/kg on milled cereal (P < 0·01) at the 300 g/day level and from 721 g/kg on whole to 766 g/kg on rolled and 772 g/kg on milled cereals (P < 0·001) at the 600 g/day level. When the effect of egested whole grain was removed there was no evidence of an effect of cereal processing on organic matter digestibility and although digestibility of fibre was higher with whole than with processed grain the effect was not significant. Wheat-based diets were more digestible than barley-based diets and, compared with barley, wheat appeared to have a beneficial effect on fibre digestion.

The effect of the anabolic steroid trenbolone acetate (TEA) on growth and body composition was studied in Scottish Blackface mature female sheep weighing 45 kg. The sheep were blocked by weight and randomly allocated to be untreated controls (C) or subcutaneously implanted with 20 (Tl), 40 (T2) or 60 (T3) mg TBA 60 days before slaughter. The sheep were offered to appetite a loose-mix diet which contained an estimated 11 M] metabolizable energy and 120 g crude protein per kg dry matter. Live-weight gain and food intake, on average, were not significantly affected by the hormonal treatment which significantly reduced gut fill and significantly increased empty body and chilled carcass weights. Of the carcass tissues which were dissected only weights of total lean and intermuscular fat were significantly increased following TBA implantation. The relative development of fat, lean and bone in the carcass in the hormonally treated compared with control sheep was not significantly altered. The only effects on weights of organs and body parts associated with TBA implantation were increases in fat deposition in omental and perinephric and retroperitoneal depots. There was some evidence of an increasing response to TBA treatment with increasing dose level for weights of chilled carcass, carcass lean and the ratio of subcutaneous fat to intermuscular fat.

Two experiments are described in which growing lambs were offered ad libitum two concentrate pelleted diets containing 60 (diet C) or 230 (diet D) g/kg barley straw.

In the first experiment, eight male and eight female lambs were used to determine the outflow rate from the rumen of chromium-mordanted fish meal and soya-bean meal, estimated from faecal marker excretion. Diet D promoted a higher rumen outflow rate (0·0769 per h) than diet C (0·0486 per h); no differences were found either between sexes or between Cr-mordanted protein supplements.

In the second experiment, the rumen degradation of fish meal, soya-bean meal, sunflower meal, pea seeds and sweet lupin seeds was studied by incubating the supplements in polyester bags in the rumens of four lambs, following a change-over design. Increasing the proportion of straw to 230 g/kg increased the rate of nitrogen disappearance from all vegetable supplements, the differences being significant only for pea seeds.

When degradation kinetics and outflow rates were considered together, effective nitrogen degradability of protein supplements was reduced by the increased proportion of dietary straw, indicating a greater influence of rumen outflow rate than of the increased rate of microbial degradation.

Computer tomography (CT) was evaluated as a method to predict body composition of live goats. Forty-one lactating goats were scanned. CT values (X-ray attenuation data) representing soft body tissues were summarized into 140 frequencies. By principal component analysis the 140 multicollinear frequencies were reduced to six orthogonal principal components at the loss of only 0·032 of the original variation.

Following scanning at four positions the goats were slaughtered, dissected and the data analysed. Seven compositional traits (water, protein and fat from the carcass and non-carcass parts, and total energy of the body) were regressed on live weight and the six principal components from each of five CT data sets (data from the four scan positions and pooled data) in a stepwise linear regression procedure. Models from the pooled data set were further evaluated in a cross-validation procedure. Compared with evaluation based on calibration only, a more simple and precise model was chosen as the best by this procedure.

After addition of CT variables in prediction equations already comprising live weight, cross-validation deviations were reduced by 0 for carcass water, 0 for carcass protein, 0·48 for carcass fat, 0·14 for non-carcass water, 0·23 for non-carcass protein, 0·73 for non-carcass fat, and 0·73 for total energy. These results show that CT is a valuable in vivo method for predicting body fat and energy, but less valuable for body water and protein.

Seven replicates of five littermate boar Landrace pigs were used to evaluate the effects of (a) reducing the food intake within the practical range or (b) reducing energy intake without reducing protein intake, between 33 and 90 kg live weight on growth, nitrogen balance and carcass characteristics. Three levels of food intake (ad libitum, 0·90 and 0·80 ad libitum) were used and the dietary protein contents ranged from 250 to 312 g crude protein per kg dry matter (DM) to equalize protein intake with reduced food intake. All the diets were of similar amino acid composition, and lysine per kg DM ranged from 14·3 to 17·9 g. The food was given twice daily. Balance trials were conducted at 45 and 65 kg live weight and all pigs were slaughtered at 90 kg live weight to assess carcass characteristics. Reducing food intake or only energy intake significantly reduced live-weight gain (P < 0·001). Reducing food intake decreased nitrogen retention (P < 0·01) during the 65-kg balance period. Reducing food intake had no effect on fat thickness measurements but measurements at shoulder (P < 0·001), mid back (P < 0·001), C(P< 0·01) and P2 (P < 0·05) decreased and lean: fat in rumpback increased (P < 0·05) when energy intake was reduced. The weights of small intestine (P < 0·001), large intestine (P < 0·05), liver (P < 0·05) and kidneys (P < 0·05) were significantly reduced as food intake was reduced. Energy is more limiting than protein when the intake of a diet providing for optimal growth of high potential boars is reduced between 33 and 90 kg live weight.

The effect of reducing energy intake within the practical range or reducing energy intake without reducing protein intake on chemical composition of gain, whole-body protein turn-over and energy metabolism was studied between 33 and 90 kg live weight with seven replicates of five littermate boar Landrace pigs. Three levels of food intake (ad libitum, 0·90 and 0·80 ad libitum) were used and the dietary protein contents ranged from 250 to 312 g crude protein (CP) per kg dry matter (DM) to equalize protein intake with reduced food intake. All the diets were of similar amino acid composition and were offered twice daily as pellets. There was no effect of dietary treatment on the DM, CP and fat contents (g/kg) of the empty body (EB), but fat content and fat: protein ratio in EB tended to decrease with reduction of food intake or energy intake. The relationship between energy intake and protein deposition was linear and the mean maximum protein retention was 187 g/day. Retention of DM (P < 0·001), protein (P < 0·001), fat (P < 0·001), energy (P < 0·001) and ash (P < 0·01) decreased linearly with reducing food intake or energy intake. The calculated residual heat production was 0·604 MJ metabolizable energy per kg M0·75 per day. The dietary treatments had no effects on composition of longissimus dorsi, fillet, liver, kidney, backfat or kidney fat. The nitrogen flux, nitrogen synthesis and breakdown tended to decrease with reduction in food intake or energy intake though the effects were not statistically significant. Nitrogen accretion decreased significantly (P < 0·05).

Food intake patterns of growing pigs given food ad libitum in individual and group housing were derived from food intake recordings with IVOG®-stations. The IVOG-station is a feeding station that records animal identification number, time, duration and amount of food intake during each visit of a pig to the food hopper. Data were collected in three testing batches of 90 Dutch Landrace pigs each, housed in 10 individual pens and in 10 group pens of eight pigs per batch.

Based on survival analysis theory, intervals between visits shorter than 5 min (which was used as meal criterion) were regarded as within-meal intervals and these visits were grouped into meals. In group housing, food intake per day and rate of food intake had no significantly non-normal distribution. In individual housing, rate of food intake, food intake per day and number of meals per day had no significantly non-normal distribution. In individual housing rate of food intake, food intake per day and number of meals per day had no significantly non-normal distribution. All traits were normally distributed after discarding extreme values, except food intake and eating time per visit and per meal. In group housing these traits were not significantly non-normally distributed after logarithmic transformation.

Pigs housed in groups ate faster, had a higher food intake per meal but less meals per day, less eating time per day and a lower daily food intake than pigs penned individually. During the day two peaks of feeding activity occurred, especially in group housing: one in the morning and one in the beginning of the afternoon.

A distinction was made between meals with a major contribution to daily food intake and meals of minor importance. In group housing, 69% of the daily number of meals accounted for proportionately 0·87 of daily food intake and 0·83 of daily food intake time. In individual housing 39% of the meals accounted for proportionately 0·90 of the daily food intake and 0·79 of the daily eating time.

Higher repeatabilities of day to day recordings of food intake traits, were found when estimated within 2-week periods compared with months or with the total fattening period.

Genes from the Chinese Meishan pig have the potential to enhance reproductive performance of European pigs. In order to allow prediction of the impact of Meishan genes in a range of alternative improvement programmes all traits of economic importance must be evaluated and genetic crossbreeding effects estimated. Entire male and female pigs of four genotypes, purebred Meishan (MS) and Large White (LW) pigs and both reciprocal Fl crossbred genotypes (MS ♂ × LW ♀ and LW ♂ × MS ♀), were farrowed in Edinburgh and subsequently performance tested at either Edinburgh or Newcastle. In Edinburgh, animals were penned in groups of four and fed ad libitum between pen mean weights of approximately 30 and 80 kg. At the end of test fat depths at the shoulder, last rib and loin were measured ultrasonically. In Newcastle, animals were penned in groups of six and fed ad libitum between pen mean weights of approximately 30 and 70 kg. Genotypic means and genetic crossbreeding effects (additive and heterosis direct effects and additive maternal effects) were estimated using restricted maximum likelihood.

When compared with the LW, the direct additive effect of genes from the MS produced increased growth rate up to the time of weaning, no change in growth rate between weaning and start of test and greatly reduced growth rate during the performance test. The maternal additive effect of genes from the MS was to reduce growth rate up to the time of weaning, with little effect thereafter. There was substantial direct heterosis for growth rate in all periods measured, but heterosis was less in males than in females during the performance test. The combined effect was such that, within sex, the LW and the two crossbred genotypes were of similar ages when they reached 70 and 80 kg, but MS pigs were 38 to 60 days older. The direct additive effect of MS genes was to increase subcutaneous fat levels and there was little evidence for the effects of maternal genes or direct heterosis on these traits. There was a direct additive effect of MS genes reducing food intake and increasing food conversion ratio and there was direct heterosis for increased food intake. There were significant interactions between genotype and sex. Male and female LW pigs had a similar performance but male MS pigs had slower growth rates on the performance test with lower food intakes, food conversion ratios and subcutaneous fat levels than the females.

The prospect that genes from the Chinese Meishan pig will be used to improve reproductive performance of European pigs requires that the Meishan is evaluated for traits of economic importance and the genetics of any breed effects investigated. Entire male and female pigs of four genotypes; purebred Meishan (MS) and Large White (LW) pigs and both reciprocal Fl crossbred genotypes (MS ♂ × LW ♀and LW ♂ × MS ♀), were fed ad libitum and slaughtered at about 70 kg. After slaughter, carcass weight, dimensions and conformation were recorded and fat depths at the shoulder, mid back and loin were measured on the carcass, together with fat depths and eye muscle dimensions recorded on a section cut at the last rib position. Drip loss, muscle reflectance and pH were measured and subjective assessments of fat firmness, fat separation, muscle marbling and muscle colour were made. Genotypic means and genetic crossbreeding effects (direct additive and heterosis effects and maternal additive effects) were estimated using restricted maximum likelihood procedures. When compared with the LW, MS carcasses had a similar killing-out proportion but were shorter with a poorer conformation. MS carcasses had substantially greater fat depths and reduced eye muscle dimensions in comparison with the LW. Differences between genotypes for fat depths and muscle dimensions were largely controlled by direct additive gene action, there was little evidence of direct heterosis and hence Fl crosses were intermediate between the purebreds. Significant genotype × sex interaction meant that genotypic differences for these traits were much greater in females than in males. Significant direct additive genetic differences between female genotypes were found for fat firmness, fat separation and drip loss, but these effects may in part have been a consequence of subcutaneous fat depth differences between genotypes. The degree of marbling was greater in MS females than in females of the other three genotypes and these genotypic differences did not seem to be associated with subcutaneous fat depth. Muscle from MS males was darker in colour with a lower reflectance than that from LW males. Genotype × sex interaction was such that genotypic differences for meat and fat quality traits differed between sexes.

Farrowing site choice was examined in 40 sows. In group 1, the preference of 16 sows was tested for pre-formed lying areas which incorporated the characteristics of previously observed farrowing nests: a hollow (H), a mattress (M), a nest box (B) and a flat control (C). None of the sows farrowed on C which indicated that choice was based on some evaluation of the lying surface. However, there was no significant preference for the three nest features: H6, M6, B 4. In group 2, C was replaced by a straw area (S). Four different amounts of straw were offered: 18, 9, 4·5 and 2·25 kg with four, four, eight, eight sows on trial at each amount respectively. All the sows farrowed on S at the 18, 9 and 4·5 levels; at 2·25 kg, three farrowed on S and five moved the straw to other lying areas on which they farrowed. The results indicated that the location of nest material has an important influence on farrowing site choice because it allows the performance of nesting behaviour. Although performance of the behaviour was not affected by the amount of straw available, 2·25 kg appeared to be inadequate for a satisfactory nest.

ad libitum water intake patterns in newly weaned pigs were investigated, with particular emphasis on the impact of water quality, the presence or absence of food antibiotics and the use of water soluble probiotic. Pigs were given water containing low (217 mg/l), medium (2350 mg/l) or high (4390 mg/l) levels of total dissolved solids (TDS), either with or without a water additive containing probiotic, and a medicated (experiment 1 and 3) or unmedicated (experiment 2) starter diet for 20 (experiments 1 and 2) or 5 (experiment 3) days immediately post weaning. Water intake, food intake, growth and faecal scores were recorded, and blood was sampled to determine ionic composition. There appeared to be two phases of water consumption: intake in the first 5 days post weaning did not appear to be related to apparent physiological need, whilst later, water consumption increased in parallel with food intake and body-weight gain. In the earlier period, behaviour may have been a primary influence; water intake was not related to faecal scores and water quality had no effect on consumption. In the later phase, intake increased at higher TDS concentrations. Water quality had no effect on performance when pigs were given medicated food; however, pigs receiving unmedicated food exhibited reduced gain (P > 0·05) and food efficiency (P < 0·05), and increased incidence of diarrhoea, when consuming water with elevated mineral levels. The probiotic did not improve performance or decrease scouring (P > 0·05). Blood composition was not affected by treatment (P > 0·05). Although physiological need may be fundamental in establishing water requirements, it appears that other factors such as water quality and the process of weaning influence consumption patterns. These data provide further encouragement for research to define true requirements for water, which by necessity would require identification of all mediating factors.

An experiment was conducted to determine the effect of level and pattern of food intake in post-partum beef cows on the length of the post-partum anoestrous period and associated luteinizing hormone profiles. Forty-six multiparous cows were allocated at calving to one of three feeding regimes: 55 MJ metabolizable energy (ME) per day throughout (LL), 145 M] ME per day throughout (HH), or 55 M] ME per day until 6 weeks post partum and then 145 M] ME per day thereafter (LH). The duration of the post-partum anoestrous period was assessed from plasma progesterone profiles. Luteinizing hormone profiles in the peripheral circulation were determined at weeks 3, 6, 8 and 11 post partum from samples collected every 20 min for 10 h.

Feeding regime had no effect on either the length of the post-partum anoestrous period, being 99, 89 and 91 (s.e.d. 12·2) days for the LL, LH and HH cows respectively, or on any aspect of luteinizing hormone pulsatility. Body condition at calving was negatively correlated with the duration of the post-partum anoestrous period, each unit increase in body condition at calving being associated with a decrease in the post-partum anoestrous period of 86 (s.e. 21·8) days. Luteinizing hormone pulse frequency at 6 weeks post partum was positively correlated with body condition at calving.

This experiment confirms the importance of body condition at calving in influencing the duration of the post-partum anoestrous period and indicates that level and pattern of feeding post partum has little effect when cows calve at a body condition of approximately 2·25.

The effect of piggery temperature on daily live-weight gain of triple cross Large White-Duroc pigs was studied. Weaning rate and fattening completion rates were similar among piglets born in different seasons of the year but the average daily weight gain was slower during the early (20 to 40 kg live weight) and intermediate (40 to 60 kg live weight) periods of fattening in the autumn-born group (T < 0·05) whilst during the late period (60 to 80 kg live weight) slower growth rates were found in the summer- and winter-born groups (P > 0·05). In the intermediate period the fastest growth rates (900 g/day) were recorded at piggery temperatures of 16 to 20°C. In the same period the slowest growth rates (602 g/day) were recorded at temperatures of 8°C or lower and at 24°C or higher. The daily live-weight gain during the intermediate period was shown to be related to piggery temperature in a curvilinear manner according to the equation Y = −2·48x2 + 90·44x + 25·37.

The Gompertz equation was used to compute growth curves for three groups of ostriches (Struthio camelus), from Oudtshoorn in South Africa, the Namib desert in Namibia and from Zimbabwe. All were reared under typical intensive farm conditions with ad libitum feeding. There were no significant differences in mature mass between regions but the maximum daily weight gain for males occurred later (day 163) for Oudtshoorn birds, compared with day 121 for Namibian and day 92 for Zimbabwean. Oudtshoorn females reached maximum rate of gain on day 175 compared with day 115 for Namibian and day 114 for Zimbabwean. Comparisons might prove important when planning programmes for the genetic improvement of commercial flocks, but possible influences of food composition and environment should be investigated.