Fifty-five calves aged 105 days of age, of both sexes, belonging to two genetic groups (H, high or L, low) differing in their predicted breeding value (PBV) by 78 kg for fat plus protein yield, were individually penned for 3 weeks with the final 2 weeks on a diet designed to provide energy close to their maintenance requirements. The calves were then cannulated in the jugular vein and blood was sampled every 15 min for 25 h. Following this a growth hormone releasing factor (GRF) preparation was administered on up to four occasions, being one of (per kg live weight) either 0·2 or 0·4 μg GRF (treatments SGRF or DGRF respectively) or 0·2 μg thyrotropin releasing hormone (TRH). On each occasion blood samples were taken at −15, 4, 8,12,16, 20 and 45 min relative to the time of administration and up to four further occasions, one prior to and three within 32 min of administration. Samples were assayed for growth hormone (GH).

GH concentration of troughs prior to an episode of GH release was 1·19-fold greater in H compared with L calves with concentrations decreasing to 0·9 of their previous values each h. Trough and peak concentrations had repeatabilities of 0·21 and 0·26 respectively (both P < 0·05). There was no association between PBV and either peak concentrations, number of pulses (4·84 per 25 h) or mean GH concentration (13·3 μg/l).

GH released was only 1·11-fold greater after DGRF than SGRF. The difference in the regression coefficients for PBV between SGRF and DGRF was small, as it was for the difference between coefficients for the two sexes. The pooled coefficient was 0·00342 loge units per kg (s.e. 0·00157; P< 0·05) indicating a 1·31-fold greater response in H than in L calves. The correlation between responses to SGRF and DGRF was 0·482 and the repeatability of SGRF was 0·338; a pooled repeatability was estimated as 0·362(P < 0·01). The regression of GH release on PBV for TRH was 0·00345 (s.e. 0·00330). For all secretagogues, response depended on prior concentrations.

It was concluded that GH release following GRF administration was positively related to PBV in dairy calves and response was moderately repeatable; furthermore, although aspects of endogenous secretion may be related to PBV they suffer from measurement difficulties.

During an experiment to measure changes in body composition of lactating Holstein-Friesian dairy cows, the velocity of ultrasound (VOS) through two hindquarter sites and a shoulder site was measured. Fifty-four cows were offered grass silage ad libitum with 3, 6 or 9 kg dry matter (DM) per day of concentrates. Six cows were slaughtered 2 to 4 days post partum (week 0) and two from each diet at 2, 5, 8, 11,14,19, 24 and 29 weeks post partum. After slaughter the right half-carcass and organs were frozen and minced before chemical analysis and the left half-carcass from 15 animals was jointed and fully dissected into bone, muscle, subcutaneous and intermuscular fat and other tissues. The relationships between the VOS measurements, together with live weight (LW) and the proportions of dissected fat and muscle tissues in the half carcass were examined and found to be comparable with published data for beef cattle. The relationships of the VOS measurements and LW to chemically determined fat and crude protein (CP) and derived estimates of energy were examined for the carcass and for the whole empty body, and found to account for proportionately 0·66 to 0·87 of the variance. The use of this noninvasive technique to monitor changes in body composition of dairy cows during lactation is therefore suggested as a useful and reliable technique. Dissection of a small inexpensive abdominal sample joint to estimate the fat: muscle ratio of the carcass was found to account for 0·85 of the variance. Finally, the relationship between dissected fat and muscle tissue weights in the half carcass and chemical fat and CP weights in the carcass and empty body were examined and found to be highly correlated.

This study investigated the potential use of blood metabolite and hormone concentrations as genetic markers for milk fat production and their possible interactions with sex and age. Two groups of calves, one from the Massey University high breeding index (HBI) line of dairy cattle (seven males, eight females) and the other from the low breeding index (LBI) line (four males, 11 females), were studied at 3·5 months and 7 months of age. The average breeding indices (BI) of the calves based on ancestry BI were 138 (s.d. 4·4) and 111 (s.d. 2·3) respectively. Serial blood sampling regimens were conducted in relation to feeding (chaffed lucerne hay at 1·3 times maintenance energy requirement), during an intravenous urea load (120 mg/kg live weight) and during fasting (63 h) and refeeding. Urea spaces and fractional decay constants at each age were estimated by a single compartment distribution model based on plasma urea concentrations following the intravenous urea load.

Plasma concentrations of urea, creatinine and non-esterified fatty acids (NEFA) were not significantly different between the lines in any of the periods examined and at either age. In contrast, plasma concentrations of glucose and insulin were greater in the HBI calves than in the LBI calves although these differences were restricted mainly to the period immediately after feeding. Urea space at 7 months of age was also greater in the HBI animals than in the LBI animals. Plasma concentrations of all hormones and metabolites except insulin were significantly influenced by sex and/or age.

The study does not confirm previous findings that genetic merit for dairying is expressed in terms of plasma levels of urea and NEFA, particularly those during a fast. However, the results of the present study are consistent with previous observations of differences in glucose and insulin metabolism between the tivo Massey University genetic merit lines. These traits may therefore have potential as genetic markers for milk fat production.

Herbage from first and second regrowths of perennial ryegrass based swards was directly ensiled following treatment with formic acid (850 g/kg) at 2·53 and 2·58 l/t, sulphuric acid (45% w/w) at 3·09 and 3·04 l/t, an inoculant of Lactobacillus plantarum (Kickstart, United Distillers Ltd) at 2/24 and 2/14 l/t, or no additive (control). First regrowth herbage had mean dry matter (DM) and water-soluble carbohydrate concentrations of 168 and 27·0 g/kg fresh weight with comparable values for second regrowth herbage of 164 and 16·9 g/kg respectively. All silages preserved well, although both the rate and extent of fermentation, as indicated by pH and lactic acid levels, were greater in control and inoculant-treated silages. Additive treatment had little effect on nutrient recovery following ensilage with the exception of a slightly greater recovery of both DM and energy with inoculant treated, second regrowth material. The silages were evaluated in two experiments, with 9 and 4 week periods for first and second regrowths respectively, using 48 British Friesian dairy cows. Animals were housed in individual stalls and, in addition to the treatment silages, received 5 kg/day fresh weight of a supplement containing 197 g crude protein per kg DM. Treatment of first regrowth material with formic acid significantly increased silage DM intake (P < 0·02) with a smaller, though positive effect being obtained with inoculant treatment. Treatment with either formic acid or inoculant had no significant effect on DM intake with second regrowth material. In contrast sulphuric acid tended to depress intake of first regrowth material whereas a marginal increase in intake was obtained with second regrowth material. Inoculant treatment had no significant effect on milk yield with either first or second regrowth material, although there was a tendency for small, though consistent, increases in milk fat and protein concentrations. Formic acid treatment resulted in marginal increases in fat plus protein yield whereas effects of sulphuric acid were less consistent with animal performance being decreased with first regrowth material and little effect observed with second regrowth material.

An iterative method is presented, based on the method of Moav and Hill (1966) to derive the optimum linear selection index for any number of traits with linear or non-linear profit functions. For non-linear profit functions the index weights will be functions of the trait means prior to selection and the selection intensity. Using the equations developed, the optimum selection index for three dairy cattle milk production traits was computed. Convergence was obtained after three to four iterations, and was robust to the starting values used for iteration. The ratio of expected genetic gains were only marginally different for selection intensities of 1 and 4 standard deviation units. Differences were greater for the index coefficients. All alternative indices tested gave lower gains in profit than the optimum index. For linear profit functions this index reduces to the standard linear index, and for two uncorrelated traits this index reduces to the index of Moav and Hill (1966).

The effects of acetone concentration in milk, feeding frequency, and intake of concentrates and energy in total diet on milk yield were studied in 38624 lactations from 474 herds during 3 years. Herd-related data on feeding factors were collected once per indoor feeding period. Milk acetone concentrations higher than 0·40 mmol/l were deemed to denote hyperketonaemia, whether subclinical or clinical. The lactation curves of ketotic cows had an abnormal shape, with an inverted peak in early lactation. Most of the reduction in milk yield took place during the first 100 days of lactation with an estimated loss of proportionately 0·085 (acetone concentration ≤0·40 v. >2·00 mmol/l). The loss in 200-day milk yield was estimated to 328 kg 40 g/kg fat-corrected milk (FCM) at an overall mean of 5056 kg. If a herd's performance is monitored by lactation curves, a low peak — and hence an apparently high persistency – can indicate a ketosis problem. More frequent feeding of concentrates was correlated with a proportionately 0·033 to 0·074 higher milk yield in multiparous cows, but inconsistent between years. A more variable proportional response (−0·035 to 0·131) was observed in primiparous cows depending on interactions with, for example, breed. A greater total energy supply, including a larger amount of concentrate (maximum in lactation), was correlated with a higher milk yield, about 0·06 kg FCM per day per MJ metabolizable energy and 0·5 kg FCM per day per kg concentrate, respectively. However, increased feeding of concentrates at calving (parity 1) and 15 days after calving (multiparous cows) was correlated with decreased milk yield, by about −0–3 and −0–5 kg FCM per day per kg concentrate, respectively.

Two randomized-block experiments were carried out to examine the relative value of wheat and barley as supplements to grass silage for finishing beef cattle. In each experiment unwilted, formic acid-treated silage was offered ad libitum and supplemented with 500 g soya-bean meal and 50 g minerals and vitamins to 44 12-month-old bulls for 157 and 172 days in experiments 1 and 2 respectively. Twelve of the animals also received 2·5 kg rolled spring barley (LB), 12 received 4·0 kg barley (HB) and 20 received 3·25 kg rolled wheat (W). For experiments 1 and 2 respectively the barley contained 796 and 787 g dry matter (DM) per kg; 118 and 105 g crude protein (CP) per kg DM; 47 and 57 g crude fibre per kg DM; the wheat contained 845 and 800 g DM per kg; 112 and 116 g CP per kg DM; 23 and 25 g crude fibre per kg DM; and the silages contained 190 and 177 g DM per kg; 153 and 176 g CP per kg DM; 80 and 104 g ammonia-nitrogen per kg total nitrogen. On average over the two experiments, for treatments LB, HB and W respectively, silage DM intakes were 5·4, 4·7 (s.e. 0·14) and 4·9 (s.e. 0·11) kg/day; total DM intakes 7·9, 8·3 (s.e. 0·14) and 8·1 (s.e. 0·11) kg/day; metabolizable energy intakes 91·4, 97·8 and 94·2 MJ/day; live-weight gains 1·04,1·19 (s.e. 0·029) and 1·10 (s.e. 0·023) kg/day and carcass gams 0·65, 0·77 (s.e. 0·017) and 0·70 (s.e. 0·013) kg/day. It is concluded that the feeding value of wheat was proportionately 0·98 of that of barley for finishing beef cattle when given as a supplement to grass silage, and that the type of cereal offered did not affect silage intake or carcass composition.

A total of 161 bulls from 11 breeds were used to generate crossbred calves from Angus cows in 1973 to 1977 at each of three diverse New Zealand locations, and from Hereford cows at one of the locations in the same years. The bulls comprised four local breeds, Angus, Friesian, Hereford, and Jersey, and seven recently imported breeds, Blonde d'Aquitaine, Charolais, Chianina, Limousin, Maine Anjou, Simmental and South Devon. This paper reports the reproductive and maternal performance of the straightbred and first-cross cows over the first four calvings, with first mating as yearlings at 14 to 16 months of age. A total of 7575 mating records from 2109 cows were analysed. Location differences were greater for reproduction than for growth traits and resulted in genotype × environment interactions for some components of cow performance and particularly the composite traits, weight of calf weaned per cow joined (productivity) and cow ‘efficiency’ (the ratio of productivity to cow weight). At all locations the Friesian-cross cows weaned the greatest weight of calf per head but were matched or surpassed by the lighter Jersey crosses in terms of efficiency of calf production. Most of the European crosses performed relatively much better in the most favourable environment than in the harsh environment and this was particularly marked for the productivity of Simmental crosses. Heterosis as a proportion of the purebred mean was important for cow performance and particularly pregnancy rate (0·12), productivity (0·21) and the efficiency ratio (0·16). Heritabilities for weight and age at puberty were both 0·34 (s.e. 0·08). Repeatabilities and heritabilities for cow reproductive traits were low (0·0 to 0·10) but higher for calf weights up to weaning as a trait of the cow (0·09 to 0·38). In general, the large European breeds which excelled in growth and carcass production produced female progeny which reached puberty at greater ages, had lower reproductive performance (especially in less favourable environments) and larger mature size. Some breed utilization strategies to achieve trade-offs between these genetic antagonisms are discussed.

The effect of including 14 g urea with either 75 g dry matter (DM) from sugar cane molasses (UM) or Colombian rice polishings (RP) at three levels, 68 (RP1), 137 (RP2) or 203 (RP3) g DM on grass hay DM intake and on rumen fermentation was investigated. An incomplete Latin-square design was used and each experimental period was divided into 12 days for adaptation to each diet followed by 9 days in metabolism cages when all measurements were made using five adult sheep.

Pooled mean values for rumen metabolites (five samples per day) were calculated. Rumen pH was not affected by the nature of the supplements. Concentrations of volatile fatty acids (VFA) (UM 92·8, RP1 84·2, RP2 86·4, and RP3 84·0 (s.e.d. 3·4) mmol/l) and lactate (UM 2·0, RP1 1/6, RP2 1/7, RP3 1/8 (s.e.d. 0·014) mmol/l) (UM v. RP, P < 0·05 and P < 0·10 respectively) were lower when RP were given, while concentration of branched and longer chain VFA (26·5, 34·0, 31·1 and 33·5 (s.e.d. 1·6) mmol/mol total VFA, UM v. RP, P < 0·01) and ammonia (98, 131, 141, 137 (s.e.d. 16·1) mg/l, UM v. RP, P < 0·05) were increased. Numbers of rumen protozoa (1·6, 3·2, 2·7, 3·3 (s.e.d. 0·75) × 105 per ml, UM v. RP, P < 0·20) tended to be higher 2 h after feeding when RP rather than UM were given. However, hay DM intake (1050, 960, 960, 880 (s.e.d. 45·3) g/day, UM v. RP, P < 0·05), and microbial protein supply (11·7, 9·3,11·1,10·8 (s.e.d. 0·59) g N per day, UM v. RP, P < 0·05), estimated from urinary purine excretion were reduced by feeding RP instead of UM.

At the levels of inclusion tested RP did not increase the efficiency of rumen fermentation and were not as effective a supplement with urea as was molasses for a low-quality forage diet.

The effect of proportion of dietary rumen non-degradable protein during food restriction on the weight of components of the digestive tract, carcass and subsequent growth was investigated in 37 Scottish Blackface wether lambs (initial live weight, 25 kg). Lambs were given individually ad libitum for 4 weeks a complete pelleted diet containing 150 g/kg white fish-meal (HP, 10·4 MJ metabolizable energy (ME) per kg dry matter (DM), 195 g crude protein (CP) per kg DM). Seven lambs were then slaughtered and 15 were switched to a diet containing no white fish-meal (LP, 10·4 MJ ME per kg DM, 122 g CP per kg DM) offered at 18 g DM per kg M per day, i.e. sufficient to maintain constant live weight. A further 15 continued to receive the HP diet at the same rate as the lambs given LP. After 6 and 12 weeks, five lambs on each diet were slaughtered. At 12 weeks the remainder received the HP diet ad libitum for a further 7 weeks before slaughter. During food restriction on both diets, the proportion of live weight formed by the carcass, the dissected components and the chemical composition remained the same as in the initial slaughter group. The relative weight of the non-carcass components fell during food restriction on both diets. There was a significant (P < 0·05) interaction between slaughter date and dietary treatment for reticulo-rumen weight as a proportion of empty body weight (EBM); it was smaller in lambs on the HP diet after 12 weeks of restriction (HP: 0·022, LP: 0·026). A similar pattern was observed for the small intestine and the total digestive tract. During the 7 weeks of realimentation, lambs previously on HP and LP diets had similar intakes (1343 and 1208 g DM per day) and digestive tract components, body components and chemical composition of carcass and non-carcass components were all unaffected by previous treatment. The apparent digestibility of CP of the HP diet was greater than that of the LP diet although it was overall less degradable in the rumen. When both groups of lambs were realimented on the HP diet, there were no differences in the apparent digestibility of any of the dietary components. A high dietary protein: energy ratio during restriction reduced the weight of some of the components of the digestive tract but did not significantly affect carcass composition. The effect did not persist following realimentation and did not significantly influence subsequent performance.

The interpretation of the results of feeding trials with lactating ewes and their sucking lambs can be improved considerably when milk energy production is known. The determination of gross energy (GE) however is time consuming and expensive. Therefore an equation to predict GE from milk constituents would be helpful.

Using multiple regression analysis a GE-prediction equation was derived with milk samples mainly from crossbred ewes. The concentrations of milk constituents were determined by infrared spectrometry (calibrated with cow milk). Fat concentration ranged between 43·8 and 125·0 g/kg, protein concentration between 32·4 and 53·1 g/kg and lactose concentration between 38·9 and 52·9 g/kg. GE (adiabatic bomb calorimetry) of the samples under consideration ranged between 3500 to 6800 kj/kg.

The following equation, including fat (f), protein (p) and lactose (I), is recommended and predicts GE as kj/kg fresh milk using constituents in g/kg fresh milk:

GE = 41·94 × f + 15·85 × p + 21·41 ×l (residual s.d. = 92, adj.R2 = 0·98).

This equation has, in the GE range 4500 kj to 6000 kj, an almost constant confidence interval with an average of ±25 kJ and an almost constant prediction interval, with an average of ±87 kJ. In the period until weaning it would appear justified to use the derived equation regardless of stage of lactation. The equation is valid for milk samples from sheep breeds with relatively high fat and low protein contents and where milk constituents have been determined by cow milk calibrated infrared spectrometry.

Previous studies in foetal and growing sheep have shown that prolonged administration of β-agonist drugs leads to selective but marked attenuation of cardiovascular, metabolic and endocrine responses to the natural catecholamine hormones adrenaline and noradrenaline, as well as attenuation of responses to the drug itself. The experiment reported here was carried out to determine whether administration of the β-agonist drug, salbutamol, by twice-daily intramuscular injection at rates of 40 or 200 μ/kg per day, for a period long enough to result in substantial attenuation of its metabolic and endocrine effects, might also result in impairment in the ability of treated animals to respond to stressful husbandry procedures which disturb metabolic homeostasis and which depend on increased sympathetic nervous and adrenal activity for the restoration of homeostasis. Serial blood sampling on day 1 and day 14 of salbutamol treatment showed that the large increases in plasma lactate and glucose observed on the 1st day were absent on day 14, while the rapid increases in free fatty acids and insulin observed on day 1 were very greatly attenuated. Daily blood sampling also demonstrated that salbutamol, like cimaterol, significantly decreased both pre- and post-feeding plasma insulin and glucose concentrations.

Metabolic and endocrine changes consequent on herding and immersion of the lambs in a sheep-dip, were unaltered by 14 days of salbutamol treatment, even though the procedure resulted in activation of the pituitary-adrenal axis as evidenced by increased β-endorphin and cortisol concentrations, and a large increase in plasma lactate concentration. These results suggest β-agonist-treated animals can respond normally to physiological stresses but further investigations remain necessary to determine whether responses dependent on increased lipid mobilization and shivering, such as shearing or prolonged exposure to severe cold, remain normal in β-agonist treated animals.

When designing environments for animals, the quality of space as well as the amount of space should be considered. In this study the influence of an opaque barrier on the aggressive behaviour and growth of Large White Χ Landrace piglets that were weaned at 24 days was examined. The behaviour and weight gain of 120 piglets were recorded during a 4-week period following weaning. These piglets were housed in either a conventional flat-deck pen or a straw pen, with or without an opaque barrier. There was no significant difference between the two types of accommodation in the frequency of aggressive interactions that occurred during the weaning period but where a barrier was present the frequency of aggressive interactions was 40% lower during the 1st week after weaning and growth rate was proportionately 0·15 greater. Piglets that were the recipients of most aggressive behaviour used the barrier most frequently during the weaning period and barrier users gained the most weight during the week immediately following weaning.

It was concluded that a barrier improved the weaning environment because it offered piglets an escape route during the period when most aggressive interactions occurred. A barrier may be an effective way of improving the welfare of animals housed in confined conditions.

Two pig breeds, one improved (Cotswold Fl hybrid Large White × Landrace pigs = LWX) and the other unimproved (Chinese Meishan pigs = CM) were used to test the proposition that the genotype of the pig has an effect on the selection of a diet from two foods that differ in their crude protein content. From 21 to 34 kg live weight, the pigs were given access to either one of three foods or a choice of two foods with similar digestible energy concentration (16 MJ digestible energy per kg) but a different crude protein (CP) concentration. This resulted in four dietary treatments: (i) free and continuous access to low (L) crude protein food alone (130 g CP per kg, no. = 4 of each breed); (ii) free and continous access to high (H) crude protein food alone (252 g CP per kg, no. - 4 of each breed); (Hi) free and continuous access to moderate (M) crude protein food alone (206 g CP per kg, no. = 4 of each breed) and (iv) free and continuous access to both foods L and H as a choice (no. = 6 of each breed). On all treatments the LWX performed significantly better than the CM pigs in terms of live-weight gain and food conversion efficiency (P < 0·001). The LWX and CM pigs given access to a single food contained the same amounts of protein in their bodies at 34 kg live weight, but the CM pigs had a considerably higher lipid (P < 0·001) and a lower water content (P < 0·001). When given a choice, the LWX pigs selected a significantly higher proportion of foodH(521 v. 226 (s.e.d. 49) g food H per kg for LWX and CM respectively) and therefore, a higher CP content in their diet (194 v. 144 (s.e.d. 5·4) g CP per kg respectively) than the CM pigs. The performance of pigs given a choice between two foods, in terms of live weight and rate of protein gain, was comparable with the best performance achieved on a single food (M) for the LWX, and better than the best performance on a single food (L) for the CM pigs. Thus, when given a choice between an appropriate pair of foods that differ in their crude protein content, pigs are able to select a diet that meets their requirements and allows them to express the growth characteristics typical for their breed (genotype).

Effects of alternative pen rearing system, stocking density, breed-type and their interactions on post-weaning rabbit performance were investigated in a replicated experiment. Californian purebred and terminal crossbred weanlings (no. = 502) were randomized amongst four pen treatments: CSD = conventional wire pen (61 × 76 × 46 cm) stocked with five rabbits; PSD = iron framed, wire-fitted, pen (76 × 244 × 46 cm) stocked with 20 rabbits; PDD = pen stocked with 40 rabbits, and PTD = pen stocked with 60 rabbits. Pen traits measured were average daily food intake (Fl), food efficiency (FE), survival rate (SR), and final weight uniformity (CV). Individual traits were initial (IW) and final (FW) weights and average daily gain (ADG) over 6 weeks.

In CSD v. PSD pen trait comparisons, FI was increased (P < 0·05), and numerically poorer FE and greater CV were detected (P > 0·05) in CSD; however, SR means were similar. Non-significant differences were observed in the PSD v. (PDD + PTD)/2 contrast (P > 0·05). For PDD v. PTD, pen FE was numerically better in the former but CV was greater (P > 0·05). Individual FW and ADG were increased (P < 0·05) in PSD v. (PDD + PTD)/2 groups; no other significant contrast differences were observed. Breed-type (B) × pen treatment (P) interaction was not significant (P > 0·05) for IW, ADG and FW; and individual sire/B × P interaction accounted for proportionately less than 0·05 of the total random variation. These results suggest the commercial potential of large pen rearing of rabbits.

Twenty-two weanling foals, about 7 months (215 days) old, were allotted to two groups. One group received high-quality protein (HP; milk powder) and the other received poor-quality protein (PP; barley protein). In addition, six foals in each group were injected intramuscularly (1 mg/kg body weight) with an anabolic steroid (Nandrolon lauras, Laurabolin vet®) at intervals of 3 weeks from weaning to 12 months (362 days) of age. Skeletal and muscular measurements from foals were also made at intervals of 3 weeks. Closure of the right distal growth plate was assessed radiographically in 13 colts in their 2nd and 3rd years of life. Blood samples were taken to investigate the blood chemistry. The HP-group foals gained weight faster from weaning to 12 months of age and were heavier at the age of 12 months than the PP-group foals. The growth of longissimus dorsi muscle and cannon bone circumference were also significantly greater in the HP-group foals. The high-quality dietary protein supplement also increased serum amino acid concentrations and haemoglobin and packed cell volume values. The foals treated with the anabolic steroid increased in body length more slowly from weaning to 12 months of age than the untreated foals. Growth plates closed about 1·5 months later in the horses treated with anabolic steroid than in the untreated horses. Weanling foals seem to require a protein supplement rich in lysine for their optimal growth. More than 31 g/day (0·46 g/MJ metabolizable energy) lysine can be recommended up to 10 months of age.

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.

Ten Large White × Landrace boars at an initial live weight of 43 kg were given free access to two isoenergetic foods with 119 (L) and 222 (H) g crude protein (CP) per kg food as a choice, for 54 days. Six more similar boars were given access to food H only. The diet selected by the choice-fed pigs (measured as the proportion of food H per kg total food intake) changed systematically with time; the CP content of the selected diet fell from 193 in the first 7 days to 146 g CP per kg food in the last 7 days. The performance of the choicefed pigs, over the 54-day period, was as good as that of those given food H only: live-weight gain was 1101 v. 1069 g/day and food conversion efficiency 0·380 v. 0·374 g gain per g food respectively. However, the choice-feeding system allowed boars to reduce the protein content of their diet as they grew. It is suggested that it might be possible to give pigs a choice between two appropriate foods during the whole growing-fattening period instead of frequently changing the composition for their single food in order to try to meet their requirements.

The effect on sow reproductive performance of including 100 g white-flowered peas (Pisum sativum hortense, cv. Vreta and Lotta) per kg, replacing barley, wheat and soya-bean meal in gestation and lactation diets, was studied over four parities using 24 pairs of crossbred littermate sows. Net sow weight gains and changes in backfat thickness over the complete reproductive cycle were similar for both treatments. Piglet live-weight gains and mean litter size at birth were not influenced by treatment, although litter size at weaning was 0·5 pigs higher (P > 0·05) for the control sows, due to higher post-natal mortality rate in the litters from the sows given the pea diets. It can be concluded that inclusion of white-flowered peas at a rate of 100 g/kg had no adverse effect on reproductive performance, with the exception of slightly higher post-natal piglet mortality.