A total of 182 pigs from one farm and comprising 65 boars (B), 65 gilts (G) and 52 castrates (C) from 48 litters, were reared from birth to 89 kg live weight. Sex of pig did not influence age at slaughter but B compared with G and C had lower killing-out proportions (0·748 v. 0·756 v. 0·753) and reduced backfat measurements. Skin damage in transit to slaughter and/or in lairage was more prevalent in B compared with C, with G being intermediate. Muscle pH measurements were not influenced by sex except ultimate pH of the m. semispinalis capitis, where B compared with G and C had a higher incidence of values above 6·1 (0·246 v. 0·060 v. 0·120). Carcasses of B had proportionately more shoulder (0·04 unit) and more leg (0·011 unit), at the expense of middle, than those of C with G being intermediate. Weight losses in the preparation of de-boned sides for curing were higher in carcasses of B compared with G and C.

Curing data were obtained from the carcasses of 54 boars (B), 58 gilts (G) and 46 castrates (C) reared from birth to slaughter at 89 kg live weight. Middle bacon rashers were compared for colour and incidence of fat splitting. The uptake of curing salts was similar for each sex group but carcasses of B retained proportionately 0012 less of the cure compared with G and C which did not differ significantly. Bacon yields from B, G and C at a final live weight of 88·6 kg were 40·6, 42·4 and 42·2 kg respectively. Sex did not influence the degree of splitting of the backfat layers in bacon rashers and had little effect on the colour of their lean tissue, but B compared with G and C tended to have a higher incidence of separation of the inner fat layer from the m. longissimus in the bacon rasher.

Consumer reaction to bacon from boars and castrates, whose production and processing characteristics were known, was determined in 122 households consisting of 238 respondents. On a seven-point scale the mean scores for six organoleptic characteristics were similar for each sort of bacon relative to that usually purchased. A proportion of 0·045 of cooks scored boar bacon at the point of strongest rejection (unappetizing aroma) during cooking but less than 001 considered that the flavour was very much stronger than their usual bacon. Few respondents marked boar bacon inferior to their usual bacon for eating characteristics. On a comparative basis the frequency distribution of scores for flavour, juiciness and pleasantness of aroma on the plate was slightly in favour of castrate bacon but was of little importance. Using the production and processing data obtained and accepting no adverse consumer reaction to boar bacon, a financial advantage to the producer of entire male pigs for bacon manufacture over castrates was demonstrated (£2·95). However, if the retailer should not reward the curer for the extra leanness of the boar then the curer might be at a financial disadvantage.

Ninety-two gilts in replicates of four littermates were mated at puberty at a mean live weight and age of 95 kg and 191 days respectively. The littermates were allocated at random to one of four food allowances (kg/day) during four successive gestations: (A) 1·5, (B) 2·0 in parity 1 followed by 1·5 in subsequent parities, (C) 20 and (D) 2·5. A diet calculated to contain 12·7 MJ digestible energy per kg was fed throughout gestation, the 2-week lactation and from weaning to conception.

The numbers of sows which conceived at parity 5 when the experiment terminated were 10, 12, 13 and 16 for treatments A to D respectively. Sow live weight at conception differed significantly (P < 0·01) from parity 2 onwards: the maximum live weights of sows on treatments A and B did not exceed 130 to 135 kg, but the live weights of sows on treatment D continued to increase to reach 195 kg at the end of the experiment. The in vivo skin plus subcutaneous fat thickness at the P2 location differed significantly (P < 0·001) between treatments from parity 2 onwards, decreasing by 3 mm in treatment A and increasing by 6 mm in treatment D from the start of the experiment to conception at parity 4. The interval from weaning to conception was significantly (P < 0·05) lower in treatment B in parity 2. This was the only significant effect and was contrary to the tendency for the interval to increase as the food allowance in gestation was decreased. The numbers of pigs born alive, stillborn or weaned (including fostered pigs) were not significantly affected by treatment. Birth weight and post-natal growth rates were significantly (P < 0·05) increased after parity 1 as gestation food allowance increased, with the exception of the post-natal growth rate in parity 3. Overall birth weight was increased by 018 kg per pig and weaning weight by 0·93 kg per pig on treatment D compared with treatment A.

One hundred and fourteen pig carcasses were measured within 1 h of slaughter for fat thickness at three locations using the SFK Fat-O-Meater. The three fat thickness locations were the last rib and 3rd and 4th last ribs measured 70 mm from the dorsal mid-line over the m. longissimus, and the lumbar fat thickness which was recorded on the anterior face of the m. glutens medius on the dorsal mid-line of the split carcass. Lean depth measurements were also recorded at the last rib and 3rd and 4th last ribs for all carcasses. After overnight chilling the leanness of each carcass was estimated using an EMME SA-1 machine. The carcasses were then separated into the major tissues. The weight of trimmed North American commercial joints (standard of 6 mm subcutaneous fat) and their lean content were best predicted by half carcass weight (residual s.d. = 0·78 and 1·23 kg respectively), whereas the EMME machine readings alone had low precision (residual s.d. = 1·51 and 1·41 kg respectively). The proportion of North American commercial joints in a carcass and their lean content were best predicted by lumbar fat (residual s.d. = 16·5 and 25·8 g/kg). The digital readout of lean content provided by the EMME machine appeared to be more related to carcass weight than lean weight, as residual s.d. for regressions increased when the overall sample was divided into two weight classes. Multiple regression equations indicated that half carcass weight and fat thickness measurements gave the best precision to predict joint and lean weights, whereas fat thickness and lean depth measurements gave the best prediction of carcass joint and lean proportions.

A feeding experiment was carried out to assess the effect on performance of three stocking rates in identical-sized pens with pigs growing from 25 to 60 kg live weight. Groups of 8,10 and 12 pigs per pen, 300 pigs in total, were used with lying plus exercise space allowances of 0·61, 0·49 and 0·41 m2 per pig respectively and an additional dunging area in each pen of 2·7 m2. There were no significant differences in rate of growth, food: gain ratio, days to slaughter or carcass backfat measurements. With 12 pigs per pen, the pigs tended to be dirtier and cleaning out of pens was more difficult. It was concluded that under the conditions prevailing a group size of 10 pigs gave the stocking rate of choice.

Thirty-eight multiparous sows were used to ascertain whether a high (4 kg/day), compared with a low (2 kg/day) food level affected early embryonic survival. To avoid any effect on ovulation rate the treatments were imposed 3 days after mating (2 days after presumed ovulation) and continued until the sows were killed 30 days after mating. Sows which were given the high food level gained more than twice as much body weight as those on the low food level, but ovulation rates, embryo numbers, embryo body sizes and embryo survival rates were similar for both feeding levels. It is concluded that, if necessary, multiparous sows may be fed higher than normal food levels in early pregnancy without prejudice to embryonic survival.

Three treatments were imposed on three groups of four boars from 26 to 40 weeks of age: a mating frequency of six copulations per week, housed near sexually receptive gilts (M + ♂); not mated, housed near sexually receptive gilts (NM + ♂); and not mated, isolated from female pigs (NM – ♂ ). The M + ♂ boars had similar semen characteristics from 49 to 57 weeks of age to the NM + ♂ and NM – ♂ boars. However, the M + ♂ boars achieved a significantly greater number of copulations (P < 0·05) and spent significantly longer ejaculating (P < 0·05) during the mating tests conducted from 49 to 57 weeks and from 66 to 70 weeks of age than the NM – ♂ boars. It is concluded that isolating young post-pubertal boars from female pigs will reduce their subsequent copulatory performance. Further, mating at a high frequency from 26 to 40 weeks of age does not appear to seriously affect subsequent semen quality.

The effect of rate of growth on the development of animals is examined in terms of it being related to variation from a pattern of development described by the allometric hypothesis. For this purpose, aliometry is expressed in terms of an extension to the shape/size concept originally proposed by Mosimann.

It is shown that such an effect of rate of growth would bias estimates of the development pattern, depending on the experimental design. However, within the framework of the method, a procedure for both removing the bias and actually estimating the effect of rate of growth on development is available.

A previously described test for one type of deviation from aliometry is shown to be incorrect by simulation.

An alternative test for the adequacy of the allometry hypothesis is developed, based on factor analysis of residual matrices from multivariate analysis of variance (the latter being used so that effects of treatment and concomitant variables can be taken into account).

Photographs of ultrasonic images of 10 animals were taken. Two replicate photographs were taken at each of four body positions (10th rib, 13th rib, 3rd lumbar and hindquarter) on both sides of the body in the morning and the afternoon of the day of scanning. Several measurements were taken on each photograph by an experienced interpreter. Replicate photographs failed to account for all possible sources of measurement error. Since neither time of day nor side of the body affected the mean value, taking observations at different times of the day or on both sides of the body could permit most sources of measurement error to be taken into account. Variation due to errors of measurement and differences among animals are presented. The residual error distribution contained several extreme outliers.

It was concluded that a better understanding of all the sources of bias and error will be needed if ultrasonic measurements are to be more widely used.

Feedlot performance and carcass characteristics were examined in bulls and steers with and without a subdermal Silastic capsule containing oestradiol-17β-dipropionate. Castration and/or oestrogen treatment was imposed at approximately 8 months of age. The implants were removed 56 days before slaughter, i.e. 140 days after the trial commenced. Bulls gained more rapidly (12·9%), converted food to live-weight gain more efficiently (18·0%) and yielded leaner carcasses than did steers (P < 0·05). The oestrogenic implant elevated serum oestradiol concentrations substantially (> ninefold) over that of bulls and steers and induced a castration-response in the former. Serum luteinizing hormone, testosterone and testicular growth were suppressed (P < 0·05) during the first 140 days of the trial in bulls, but returned to normal following implant removal. This response was paralleled by a reduction in average daily gain (P < 0·05) and food: gain ratio (P < 0·10). Contrary to expectations, average daily gain and food: gain ratio were not significantly improved in implanted steers. Oestrogen treatment reduced hot carcass weight, loin eye area and quality grade in both bulls and steers; the last as a result of decreased marbling and internal fat deposition. Results of this study suggest that excessive oestrogen as provided in this study via the implant fails to improve feedlot performance and carcass merit in steers and may, in fact, diminish the inherent anabolic attributes of the intact male. Additional studies are required to understand the complex interactions of androgens and oestrogens in the regulation of body growth and composition of male cattle.

Twenty bull calves were assigned to one of four treatment groups: 1) intact bulls; 2) intact bulls implanted with oestradiol dipropionate; 3) steers, and 4) steers implanted with oestradiol dipropionate. Subcutaneous adipose tissue was obtained by biopsy 5 months after implantation. Experimental treatment did not alter (P > 0·05) mean adipose cell volume, diameter or cell number per g adipose tissue. Soluble protein content of adipose cells from bulls was increased by implantation, but not in steers. In vitro rates of fatty acid synthesis were higher in oestrogen-implanted cattle compared with nonimplanted cattle when expressed per g adipose tissue, but not when expressed per cell. Maximal activities of the lipogenic-related enzymes, acetyl coenzyme A carboxylase, adenosine triphosphate-citrate lyase, aconitate hydratase and NADP-isocitrate dehydrogenase were higher in implanted compared with nonimplanted cattle when the activities were expressed per g tissue and acetyl coenzyme A carboxylase and aconitase were also higher when expressed per adipose cell. Bulls and steers had the same basal and stimulated lipolytic rates and implantation of oestradiol dipropionate had no effect on either basal or stimulated lipolytic rate. In this experiment, the oestrogenic implant appeared to have a stimulatory effect on in vitro estimates of lipogenesis.

Two groups of suckling Charolais cows were fed at different levels of nutrition from 70 days before the estimated date of calving until 45 days after calving, to study the effects of reduced dietary intake on pre-partum plasma levels of progesterone and total oestrogens (conjugated + unconjugated) and post-partum plasma levels of luteinizing hormone and follicle stimulating hormone. Eight control cows received a ration containing the Institut National de la Recherche Agronomique's recommendations for all nutrients, while 10 cows received a restricted diet which supplied approximately three-quarters of the recommended amounts for energy and nitrogen.

The mean weight of the two groups of cows was similar at the beginning of the experiment but the restricted group had a significantly lower weight just before calving than the control group (678 v. 766 kg; P < 0·05).

After calving, cows ont he low diet had a weight loss of 600 g/day, while those on the control diet gained 300 g/day. During the last 45 days of pregnancy underfeeding did not significantly affect oestrogen levels, but progesterone levels increased proportionally by 0·24 (P < 0·01).

During the first 45 days of lactation underfeeding decreased the number of cows showing oestrus (0/10 v. 4/8) and significantly decreased both luteinizing hormone and follicle stimulating hormone levels at 5, 15 and 30 days post partum.

Furthermore, the correlation between mean daily gain (0 to 45 days post partum) and luteinizing hormone concentration on day 30 was highly significant (r = 0·58; P < 0·01; no. = 19). These results suggest that the delay of the first post-partum ovulation in the underfed cow is due to low gonadotropin levels.

A growth trial lasting 84 days and digestibility trials were carried out with Hereford × Friesian steers weighing initially 360 kg. Daily dry-matter intakes (kg) of 32 steers offered turnips with blood meal (250 g/day) and straw treated with sodium hydroxide (SP), urea (UP), ammonia (AP) or untreated (CP), and of a further eight steers offered turnips and ammonia-treated straw without a supplement of blood meal (A) were 6·5 (SP), 6·0 (UP), 6·6 (AP), 5·9 (CP) and 6·3 (A); live-weight gains (kg/day) were 0·69, 0·58, 0·60, 0·37 and 0·39 respectively. The non-protein nitrogen intake of steers on treatments SP and CP were matched to those on treatments AP, A and UP by the addition of urea. Coefficients of apparent straw organic matter digestibility were 0·629 (SP), 0·531 (UP), 0·578 (AP), 0·446 (CP) and 0·569 (A). Overall food intakes on all treatments were low initially (88 g/kg W0·73) and declined further to 78 g/kg W0·73. Live-weight gains also were low; those of steers given diets CP and A were lower (P< 0·001) than gains of steers on other treatments.

Improvements in the apparent digestibility of straw were obtained by chemical treatment but all values, except that of the UP group, were low. The supplementation of ammonia-treated straw with blood meal (AP) produced a higher (P < 0·001) growth rate in steers compared with that of steers receiving ammonia-treated straw alone (A). The low mean pH (6·48) and ammonia concentration (9 mg/100 ml) of rumen liquor sampled during the growth trial suggest that the poor growth rates and low food intake of cattle in this trial may be associated with the rapid release of soluble sugars from turnips given only once daily.

Wheat straw treated with 35 g NaOH per kg was offered to male calves at three levels: 300 (A), 500 (B), and 700 (C) g/kg diet, in a metabolism trial and in a feeding trial. In the former the wheat straw was offered either neutralized with HC1 (N) or unneutralized (U), in six subtreatments (AN, BN, CN, AU, BU and CU) in a 3 × 2 factorial design to a total of 24 calves. Dry-matter intake per kg W0·73 was 123, 108, 104, 122, 105 and 91 g/day, and the digestibility of the organic matter of the straw was 0·388, 0·616, 0·629, 0·385, 0·528 and 0·544 respectively. The apparent digestibility of the crude protein of the straw was negative. Nitrogen retention per kg W0·73 was 0·91, 0·58, 0·52, 0·97, 0·57 and 0·50 g/day, respectively.

In the feeding trial, unneutralized, NaOH-treated wheat straw was offered to a total of 84 calves for 100 days at the above three levels with two protein levels: standard, 120 g/kg (S) and high, 140 g/kg (H), in six subtreatments (AS, BS, CS, AH, BH and CH) in a 3 × 2 factorial design. The concentrates were pelleted. From day 101 to slaughter all the calves were offered one finishing diet.

Level of protein had no effect on performance. Increasing the levels of straw in the first 100 days sharply reduced average daily gains; these were 1 074, 825 and 583 g, respectively. However, the respective average daily gains on the finishing diet were 1 131, 1 272 and 1 316 g, indicating a considerable amount of compensatory growth.

Wheat grain was given whole (W), cracked (C) or ammonia-treated (N) as the sole diet to six steers. In Expt 1, W, C and N were given at the rate of 2·1 kg per head per day. In Expt 2, W and N were given at the rate of 7·35 kg per head twice weekly; feeding of C had to be abandoned due to frequent bloat. Dry-matter digestibility was 0·79, 0·86 and 0·88 on W, C and N in Expt 1 and 0·75 and 0·83 on W and N in Expt 2.

The digestibility of neutral detergent fibre was 0·37, 0·24 and 0·57 with diets W, C and N respectively in Expt 1 and 0·27 and 0·47 with diets W and N in Expt 2.

The quantity of whole grain voided in faeces (g/kg grain fed) was 122, 3 and 31 with W, C and N in Expt 1 and 136 and 51 with W and N in Expt 2. Voided grains had a lower ratio of cr-glucose: neutral detergent fibre than grains fed, which indicated partial digestion of starch. Rates of nitrogen retention (g/day) were 6·6, 9·4 and 9·8 with W, C and N in Expt 1 and 7·2 and 12·2 with W and N in Expt 2.

It was concluded that ammonia-treated whole wheat grain is utilized as efficiently as cracked wheat grain when given as a sole diet to cattle and results in fewer digestive disturbances than cracked wheat grain.

An experiment was performed to examine the effects of feeding four concentrations of crude protein in the diet to lactating rabbits. Diets A, B, C and D contained 173, 181, 224 and 243 g crude protein per kg dry matter respectively. Each diet was offered at one of two feeding levels: H (330 g/day) or L (280 g/day) with three replicates in each of the eight treatment groups. Milk production and nitrogen balance were measured over a 28-day lactation.

Although dry-matter intakes on feeding level H were significantly higher than those on feeding level L the difference diminished as the crude protein concentration decreased. The effect of crude protein intake on doe milk production was estimated therefore by regression analysis with digestible energy intake as a covariate. Both crude protein intake and digestible energy intake alone had significant effects (P < 0·001) on daily milk production and there was also a significant effect (P < 0·05) of crude protein intake after fitting digestible energy intake. Overall the equation was:

Milk production (g/day) =

17·61 + 0·985 crude protein intake (g/day) + 30·3 digestible energy intake (MJ/day).

(±0·448) (±14·8)

The relationship between digested nitrogen and nitrogen output as milk was also examined by regression analysis with digestible energy intake as a covariate. This equation was:

Nitrogen output in milk (g/day) =

0·438 + 0·164 digested nitrogen (g/day) + 0·572 digestible energy intake (MJ/day).

(±0·068) (±0·294)

The practical implications of feeding high levels of crude protein in the diet to increase milk production and pup weaning weight are discussed.

A rabbit nesting box incorporating a low wattage heated floor was developed. In a preliminary study a floor surface temperature in the box of 27°C was found to be adequate to minimize chilling of young pups in the nest. A full scale trial followed using 44 crossbred does, 22 provided with a nestbox containing a heated floor and 22 with a control plywood nesting box. The experiment continued for six successive reproductive cycles over the period April 1981 to February 1982 in an unheated rabbitry. Throughout the year significantly more pups reached weaning age when does were provided with nestboxes containing heated floors. On average, 0·15 of all pups born to does with heated floors had died by 28 days post partum, the comparable figure for unheated floors being 0·56. This reduction in mortality in heated boxes was apparent both on the day of birth and in the subsequent weeks prior to weaning. Ambient temperature and the wetness of the nest had a strong influence on the survival of pups in control boxes with high mortality rates experienced in the cold winter months (0·79 in February 1982). Most of these deaths in the control boxes were attributable to chilling and/or starvation in the nest (0·53 of diagnosed deaths overall). The running costs of the heated nestbox system are discussed.

The intake of ten 5-year-old Masham ewes with good teeth, five 7-year-old Mashams with poor teeth and nine 10-year-old ewes with poor teeth was measured when they were offered long (35·1 cm) or short grass (3·8 cm) outdoors or poor quality hay indoors. The young ewes ate significantly more grass and hay than the old ewes, but the difference in daily intake was greater with long grass (1473 v. 751 g organic matter per head) and with hay (895 v. 421) than with short grass (617 v. 407). The intermediate age ewes ate as much of the long grass and of the hay as the young ewes, but less of the short grass. This suggests that age influenced intake more than did tooth condition, except when short grass was offered.

Within the oldest but not within the intermediate group of ewes, there was a significant correlation between the number of incisors and organic matter intake, except with the long grass, but there was no correlation between the number of cheek teeth and intake. When offered hay, the only group with a reduced in vivo digestibility was the intermediate group of ewes, the other two groups having a similar digestibility.

There was no correlation between number of incisors or number of molars and in vivo digestibility.

Lambs, 8 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females as a common maternal breed were fed ad libitum on a concentrate containing barley and fish meal for 14 weeks. Live weight and food intake were measured at intervals of 2 weeks.

Live-weight gain varied between sire breeds, Suffolk crosses having the greatest growth rate and the Blackface lambs the least, but there were no significant differences in their food conversion ratios. Food intakes were compared with those predicted by two methods. When the only criteria for prediction were live weight and the metabolizability of the diet the prediction was poor, whereas very accurate agreement was found when the criteria for prediction included consideration of the changes in energy efficiency with food intake and with maturity.