A two-pool model of tritiated water kinetics was investigated as a means of partitioning total body water into empty body water and gut water in 17 lactating goats. Empty body water, gut water and total body water were of a similar magnitude to, and highly correlated with, a rapidly equilibrating tritiated water pool, a more slowly equilibrating pool and the sum of these two pools, respectively.

Empty body fat was poorly correlated with both live weight and empty body weight (R2 = 0·42 and 0·51, respectively). However, there was a strong inverse relationship between the water and fat contents of the empty body. Consequently, empty body fat was accurately predicted by a multiple regression equation which included both empty body weight and empty body water as independent variables (R2 = 0·97). Substitution of these variables with estimates derived from tritiated water kinetics still resulted in a high correlation (R2 = 0·88). Tritiated water kinetics offered little improvement over live weight alone in the prediction of empty body protein, empty body ash or fat-free empty body.

The performance of 32 Cambridge (C) and Suffolk × Cambridge (S × C) twin and triplet rearing ewes and their progeny was investigated from lambing until the lambs reached slaughter weight. The ewes and lambs were housed and penned in individual family groups until 35 days after lambing. From 7 to 35 days the effect of rearing type was studied in combination with feeding the ewes a complete diet containing either 250 (diet 250) or 400 (diet 400) g milled hay per kg. After 35 days ewes and lambs grazed pasture. Ewes suckling triplets produced slightly more milk at 20 days 4·3 v. 4·1 (s.e.d. 0·20) kg/day and significantly more at 30 days 4·1 v. 3·7 (s.e.d. 0·18) kg/day, but consumed similar amounts of dry matter (3·9 kg/day) and so tended to lose more body condition. The latter was also a feature of ewes given diet 400 which produced similar milk yields but had lower complete diet intakes than those on diet 250. S × C had higher yields than C ewes.

Triplet lambs grew faster than twins 361 v. 290 (s.e.d. 9·0) g/day to 35 days but during the outdoor period triplet males but not females grew as fast as their twin counterparts 337 v. 317 for males and 269 v. 302 for females (s.e.d. 12·7) g/day. A selection of male twin and triplet lambs was slaughtered within the range 39 to 42 kg when 102 and 105 days old respectively. Triplet lambs had a lower killing-out proportion 0·458 v. 0·477 (s.e.d. 0·0085) and hence carcass weight but all carcasses qualified for Meat and Livestock Commission certification.

An investigation was made into a possible relationship between the relative growth potential and skeletal muscle fibre number in low birth weight Large White pigs and their heaviest birth-weight littermates. Estimates of the total fibre number of m. semitendinosus were made from 23 pairs of ‘small’ and ‘large’ littermates. Littermates were slaughtered at the same age and were of a mean live weight 86 (s.d. 15) kg. Small littermates (mean birth weight 939 (s.d. 164) g) had, on average, lower live weights at slaughter (P < 0·001) and lower muscle fibre numbers (P < 0·05) than their large littermates (mean birth weight 2085 (s.d. 343) g). However, pigs within the low birth-weight category exhibited various degrees of catch-up growth with their heaviest littermates and some individuals actually exceeded their large littermates in live weight at slaughter. The relative live weights at slaughter and relative muscle fibre numbers of small and large littermates were determined by expressing the value for the small littermate as a proportion of the corresponding value for its large littermate. No correlation existed between relative live weight at slaughter and relative muscle fibre number of small and large littermates. The small littermates were then divided into two groups by their mean value of relative small to large slaughter weight (0·84). The littermates of low relative slaughter weight (≤0·84) exhibited a large range of muscle fibre numbers although their mean fibre numbers were lower than their large littermates (P < 0·05). This large range was probably responsible for the lack of correlation mentioned above. Those small littermates which exhibited a good degree of catch-up growth (relative slaughter weight >0·84) possessed fibre numbers which were not significantly different from those of their large littermates. These results suggest that pigs which exhibit an appreciable degree of catch-up growth always contain high relative numbers of fibres in their muscles. Those which show a poor degree of catch-up growth (≤O·84) exhibit a range of fibre numbers because there may be environmental and other factors which prevent some pigs from realizing their full growth potential. The results of the present study advocate muscle fibre number as an indicator at birth of potential for post-natal growth performance.

Sixty crossbred females received one of three pregnancy feeding rates over five parities: high (2·3 kg/day); medium (2·0 kg/day) and low (1·7 kg/day) to produce variation in body fatness and live weight. During a 32-day lactation all sows were fed the same allowance according to litter size. At the start of parity 5 ultrasonic P2 backfat depths for the high, medium and low treatments respectively were 11·2, 11·0 and 10·6 (s.e. 1·77) mm while live weight was 184, 177 and 167 (s.e. 8·6) kg. Averaged over five parities, backfat depths at conception were not significantly different between treatments. Sows given higher pregnancy feeding rates in pregnancy were heavier and fatter pre-partum but lost relatively more live weight and backfat during lactation. Regression coefficients for the slope of the relationship between total sow pregnancy weight (kg) and fatness (mm) change, and food intake (kg/day) were 0·2 and 0·04 respectively. Pregnancy feeding rate did not influence the number of live births but total litter weight at weaning was positively related to the weight and fatness of the sow at parturition and her subsequent rate of weight and fat loss during lactation (these characteristics of the sow also being positively related): live weight of litter at 32 days (kg) = 67 – 1·8 sow backfat change in lactation (mm) – 0·4 sow live-weight change in lactation (kg). Absolute sow live weight and fatness were positive influences on readiness to rebreed after weaning.

The relationships between the sucking behaviour of newborn piglets during bouts of sucking and their serum immunoglobulin G (IgG) levels at 12 h of age were investigated in 274 Landrace × Yorkshire piglets from 24 second parity Yorkshire sows. Mean IgG level differed between litters but was not related to the number of live-born piglets or the mean birth weight of the litter; in addition, the amount of variation in IgG level within a litter was not related to the number of live-born piglets or the amount of variation in birth weight of the piglets.

Within a litter, lower serum IgG levels were found in piglets of birth orders greater than eight and piglets that had a very low frequency of sucking bouts. The piglets that had the higher IgG levels within a litter were those that started to suck sooner, sucked from many teats and won more of their teat disputes. Piglets that were involved in fewer teat disputes within a litter or took a greater proportion of their sucking bouts on anterior teats did not have higher IgG levels. Piglets that died differed from their surviving litter-mates in having lower IgG levels and having lost weight during the first 12 h after birth. Within a litter, IgG levels were not related to 10-day weight gain. However, litters with a lower mean IgG level also had a lower mean 10-day weight gain. It is suggested that a low mean IgG level in a litter reflects or predicts a low milk production by that sow.

Whole-body amino acid composition was determined in six male and six female 53-day-old New Zealand White rabbits. There were no significant sex differences in whole-body amino acid compositition except for arginine and glycine where whole-body concentrations (g/16 g N) were significantly lower in the females (P < 0·05). Overall mean whole-body essential amino acid levels (relative to lysine = 100 units) were methionine = 20; cystine = 41; histidine = 50; phenylalanine = 65; tyrosine = 50; threonine = 64; leucine = 112; isoleucine = 51; valine = 62; arginine = 109. The lysine concentration of rabbit whole-body tissue was 6·12 g/16 g N. There was close agreement between rabbit whole-body amino acid composition and corresponding published values for the rat and pig, although the rabbit whole-body cystine was high and methionine concentration low compared with the rat or pig. The rabbit whole-body amino acid pattern can be regarded as approximating an ideal balance of dietary amino acids and as such indicates discrepancies in current recommendations on the essential amino acid requirements for growth in the meat rabbit.

Operant conditioning techniques were used to measure the feeding motivation (hunger) of pigs restricted to the low food levels used under certain commercial conditions. Six Large White × Landrace boars were maintained in individual pens where they received their daily food allowance. Initially food was available ad libitum; subsequently boars were restricted proportionately to 0·8, 0·6 and 0·4 of their ad libitum intake in a Latin-square design. Finally boars were again offered their previously measured ad libitum intake (treatment 1·0). Hunger was measured by conditioning boars to press a panel 10 times to receive a 7-g reward of food. Operant response rates were measured over 20-min sessions during each of the treatments and at three times of day (pre-feeding, immediately post feeding and 5 h post feeding).

Operant response rate was strongly affected by restricting food allowance (means: treatment 1·0, 42 panel presses; 0·8, 212; 0·6, 266; 0·4, 320). There was a signficant interaction between food allowance and time of day (P < 0·001). Treatments did not vary in response rate before feeding. Treatments 1·0 and 0·8 depressed response rate post feeding (P < 0·001) and treatment 1·0 also 5 h post feeding (P < 0·001). Response rates on treatments 0·6 and 0·4 did not vary significantly from one another or with time of day.

Restricting pigs to low food levels resulted in a high level of hunger throughout the day. This was so even for food allowances that met current recommended feeding levels sufficient for maintenance and low weight gain (treatment 0·6 equivalent to 1·3 times maintenance). Commercial levels of feeding for the pig breeding population whilst meeting production needs do not satisfy feeding motivation. The hunger resulting from low food levels may act as a major source of stress under certain husbandry conditions such as tether and stall systems for dry sows, where sows are subject to both physical and food restriction.

Differential rates of genetic change in litter productivity, growth and carcass traits were estimated for the pig populations of six British breeding companies from their relative performance between 1972 and 1981 in the Meat and Livestock Commission's Commercial Pig Evaluation. Pigs were grown on one of two feeding regimens and slaughtered at one of three live weights (61, 93 and 118 kg).

Important differentials were found for a number of traits. Annual rates of change in litter size at birth differed by 0·34 pigs between the two extreme populations. The range between populations for live-weight daily gain (ad libitum feeding) was 20 g, for lean weight daily gain (restricted feeding) it was 6 g, and for lean weight food conversion (feeding regimens pooled) it was 28 g food per g gain. The average annual rate of change of the six company populations was compared with the rate achieved by the purebred Large White breed over the period 1972 to 1977. For mean piglet birth weight the rate was 30 g higher for the company populations, whilst for carcass weight daily gain it was 24 g higher.

There was little evidence for population × feeding regimen interactions except that companies ranked differently in average daily food intake, live-weight daily gain and carcass weight daily gain on the two feeding regimens. On limited evidence, population × slaughter weight interactions were also unimportant.

Over a 40-day period nine rabbits were each given one of nine isocaloric diets with progressively reduced amounts of crude protein (159 to 97 g/kg) but a fixed level of lysine; the latter was slightly below the higher of the National Research Council (NRC, 1977) and Societe de Chime Organique et Biologique (AEC, 1978) recommendations. The proportion of each other essential amino acid in the diet of highest crude protein concentration was close to a balance derived from the higher of each independently determined amino acid requirement given by NRC (1977) and AEC (1978), while the proportions in the two diets of lowest crude protein level were below those in a theoretical amino acid balance based on rabbit whole-body tissue composition. When an intersecting linear regression line model was fitted to growth performance data over the period, performance was found to be similar on the first six diets (159 to 123 g crude protein per kg) but further reductions in dietary protein were accompanied by a decline in growth rate and concomitant increase in food conversion ratio. Fitting of an asymptotic model to the data showed that growth performance first declined markedly between diets four and five (130 to 120 g crude protein per kg). These findings suggest that if a balance of essential amino acids relative to lysine, based on current amino acid recommendations, is adhered to in diet formulation for the growing rabbit, several of these amino acids will be in excess of requirement

Abstract The effects of two temperatures (thermoneutral, 22°C v. fluctuating high temperature, 35·22°C), four food levels (ad libitum and three levels of food restriction) on growth and energy retention of growing pigs (male and female) was investigated in a 2 × 2 × 4 factorial experiment involving 48 individually penned pigs from 20 to 50 kg live weight. A second experiment was conducted over the 50 to 80 kg liveweight range using a 2 × 2 × 3 design.

Mean daily digestible energy (DE) intake, daily gain, P2 backfat thickness, carcass fat proportion, total body energy retained and body energy retained as protein did not differ significantly between the temperature treatments in either experiment. Mean carcass protein proportion was greater at 35·22°C than at a constant 22°C.

With pigs given food ad libitum during the 50 to 80 kg phase, an increase in temperature from 22°C to 35·22° reduced daily DE intake by 4·1 MJ (38·9 v. 34·8 MJ or 300 g food per day), reduced energy retention by 2·3 MJ/day (15·6 v. 13·3 MJ/day), and increased carcass protein proportion by 11 g/kg (142 v. 153 g/kg).

There was a significant interaction between the effects of sex and temperature on P2 backfat thickness over both live-weight ranges. Female pigs housed at 35·22°C had 2·6 mm less P2 backfat at 50 kg (13 v. 15·6 mm) and 2 mm less at 80 kg (20 v. 22 mm) compared with females housed at 22°C. The P2 backfat thickness of male pigs did not vary at 50 kg (13·2 v. 13·5 mm) but when housed at 35·22°C males had 1·4 mm more P2 backfat at 80 kg (18·2 v. 19·6 mm).

Twenty pregnant sows sharing a double-entry back-out Pig Code feeder with a similar group of 20 were observed over six 24-h feed cycles by a combination of direct observation and video recording. The group had access to an area of 47 m2. Sows were fed once a day on a pelleted diet and water was continually available. Feeding order was relatively constant from day to day, and was positively correlated with parity. A social hierarchy based on displacements and attacks within pairs of sows was found to be basically linear, with the exception of six reversals of dominance. Social hierarchy was positively correlated with feeding order overall, but this was not the case for the latter half of the feeding order. This was partly due to disruption of feeder use by non-feeding visits made by early-feeding dominant sows. Overall the results showed that older sows with more experience of the feeder in two or three previous parities were higher in the feeding order and social hierarchy than younger sows, and may exclude them from the feeder by repeated non-feeding visits.

Selection was carried out in a line of pigs for increased growth rate of lean tissue. The selection criterion was weight of lean in the ham predicted from live backfat and weight measurements after a 12-week performance test commencing at 25 kg live weight. All pigs were given the same total amount of food over the test period. The scale was set to about proportionately 0·85 of predicted ad libitum intake. Boars selected with an intensity of 1/12 were used for 6 months and sows selected with an intensity of 1/4 were kept for two farrowings. An unselected control line was maintained concurrently.

After five generations, performances of selected and control line pigs were compared on ad libitum and scale feeding as they grew to 85 kg. Responses in the selected line on scale feeding were +51 g/day for growth rate (GR), −0·16 for food conversion ratio (FCR), −2·2 mm for backfat (F) and +0·47 kg for ham lean (HL). On ad libitum feeding, responses were much higher in the selected line, giving rise to line × food interactions. Responses were +128 g/day for GR, −0·27 for FCR, −2·3 mm for F, +1·01 kg for HL and +0·15 kg/day for food intake (FI). Estimates of the heritability of HL from variance components were 0·43 (s.e. 0·15) on scale feeding and 0·28 (s.e. 0·19) on ad libitum feeding. The realized heritability of HL on scale feeding was 0·29 (s.e. 0·04) and its co-heritabilities with the other traits on both feeding levels were of similar magnitude to its heritability. Scale feeding exposed genetic variation in the partitioning of food between lean and fat deposition and appeared to be a suitable selection regimen for performance on ad libitum feeding.

The absence of a simple, accurate method of lamb carcass composition assessment presents difficulties in satisfying an increasing consumer demand for leaner meat. Present carcass classification methods, depending on visual appraisal by trained personnel, may be perceived as subjective and consequently little support for the scheme is found within the industry. Ten carcasses of varying weight (19·9 (s.d. 5·9) kg) and side concentration of fat (303·61 (s.d. 102·70) g/kg) were assessed for impedance to the flow of an alternating current (800μΛ at 50Hz) by use of an impedance analyser. Impedance measurements were highly repeatable (> 0·90) and prediction equations for side concentration of fat and lean produced residual s.d.s of 23·25 to 18·80 g/kg and 37·10 to 18·55 g/kg respectively. Impedance measurements may provide an inexpensive, accurate and simple means of assessing lamb carcass composition

Fifty entire male pigs between 7 and 28 days and 50 entire male pigs between 28 and 56 days of age' were given basal diets containing peanut meal as the protein supplement. These diets contained 4·5 to 6·1 g threonine per kg and were supplemented with graded additions of synthetic L-threonine.

It was found that the amount of threonine required for maximum performance and nitrogen retention was 6·6 g/kg dry matter (DM) between 7 and 28 days of age and 5·4 g/kg DM between 28 and 56 days of age. These values were calculated to correspond to 0·43 and 0·36 g threonine per MJ digestible energy.

The concentration of threonine in the blood plasma did not give a clear indication of the threonine requirement of the pigs.

Two trials were conducted with eight yearling camels with an average intial body weight of 300 kg, to evaluate protein and energy values of lucerne hay and barley grains. In each trial, eight animals were randomly allotted to two different dietary treatments of coarsely ground lucerne hay or lucerne hay + barley grain (50:50) in such a way that two animals in each of the two blocks received the same ration. Each trial consisted of a 10-day preliminary period followed by a 7-day collection period during which total urine and faeces collections were made, and samples were processed and composited for later analysis.

All animals consumed daily an average of about 5 kg food divided in two equal meals. The apparent digestibility coefficients for organic matter, crude protein, neutral-detergent fibre and cellulose of the lucerne hay ration improved respectively from 0·615, 0·662, 0·455 and 0·555 to 0·736, 0·655, 0·547 and 0·589, as a result of incorporating 500 g/kg barley grain in place of hay in the diet. Even though there was no difference in the proportion of nitrogen retained relative to intake, the proportion of nitrogen retained relative to that absorbed was higher (P < 0·05) in the lucerne + barley group (0·769) than in the lucerne-only group (0·747). On a dry-matter basis, the feeding value in camels of digestible protein (g/kg), total digestible nutrients (g/kg), digestible energy (MJ/kg), metabolizable energy (MJ/kg), net energy maintenance (MJ/kg), net energy lactation (MJ/kg) and net energy gain (MJ/kg) were respectively 118, 552, 10·0, 8·4, 5·4, 5·0 and 2·1 for lucerne hay and 80, 800, 14·6, 12·1, 8·4, 8·8 and 5·0 for barley grain (calculated by difference).

It is known that microbial activity in the hind-gut of pigs influences the amino acid composition of faeces (Mason, 1984), yet contributes little to protein nutrition (Just, Jørgensen and Fernández, 1985). This diminishes the extent to which amino acid digestibility determined by faecal collection from intact pigs adequately represents nutritional value. In order to minimize the interference of hind-gut microflora, pigs for digestibility trials have been surgically modified to create a by-pass of the large intestine by ileo-rectal anastomosis (e.g. Green, Bertrand, Duron and Maillard, 1987 and 1988). This involves transection of the ileum approximately 100 mm anterior to the ileo/caecal valve. The modification can be considered as an alternative to collecting digesta from cannulas fitted in the ileum. The attributes of ileo-rectal anastomosis are that all digesta, rather than spot samples, can be collected and the animals remain in good health for many months of trial work. There is, however, concern that because the anastomosis operation involves complete severance of the ileum, digestion in the ileum may be abnormal. Of particular concern is the by-pass of the ileo-caecal valve which is suspected to have a restraining rôle on digesta passage (Gazet and Kopp, 1964; Laplace and Borgida, 1976), and therefore a possible influence on digestibility. When using ileo-caecal valve, by fitting the anterior digesta, other workers have attempted to preserve a complete ileum, and functional ileo-caecal value, by fitting the anterior cannula immediately posterior to the valve (Laplace, 1986)

Forty Hereford cross steers of 350 kg live weight were allocated to 10 treatments in which straw was offered ad libitum. The straws comprised two varieties of winter barley (Gerbel (G) an Igri (I)), two varieties of spring barley (Corgi (C) and Golden Promise (GP)) and one variety of winter wheat (Norman (N)). Each straw was offered either untreated (with 20 g urea per kg added at feeding), or treated (with 30 g anhydrous ammonia). After 10 weeks the treatments were changed. The mean growth rates for steers receiving the untreated straws were 0·11, 0·13, 0·40, 0·20 and 0·27 kg/day and for treated straws were 0·36, 0·33, 0·61, 0·60 and 0·52 kg/day for G, I, C, GP and N respectively. The straw intakes for untreated straws were 3·4, 3·6, 5·2, 4·4 and 4·6 kg dry matter per day and for treated straws 4·7, 4·8, 5·9, 4·9 and 5·8 kg dry matter per day for G, I, C, GP and N respectively. Chemical and biological measurements were compared as predictors of voluntary intake of straw and growth rate in the steers. Biological measurements were very efficient in predicting performance of the steers while chemical measurements were much less valuable.

Days elapsed from the mid point of the anoestrous period to first (DF) and last (DL) oestrus of the breeding season and duration of this breeding season (DD) within a flock of 60 adult Lincoln ewes are reported in this note. All traits showed considerable variation and the phenotypic correlation between DF and DD was −0·57 (P < 0·01) while that between DL and DD was 0·87 (P < 0·01). However, DF was not correlated with DL (P = 0·10).

Two trials were conducted in 1986 on artificial insemination of female fallow deer at fixed intervals from the cessation of oestrous synchronization treatment. Semen had been collected previously from mature bucks by electroejaculation and extended in sodium citrate/egg yolk diluent.

In the first trial involving a comparison of the fertilization rates of fresh and frozen-thawed semen delivered intravaginally, 57 does each received a single intravaginal progesterone-releasing device (CIDRtype S, Carter Holt Harvey Plastic Products Group Ltd, Hamilton, NZ) for a 14-day period early in the 1986 breeding season. All does were inseminated intravaginally with either fresh (no. = 26) or frozenthawed (no. = 31) semen (85 × 106 motile spermatozoa per inseminate) at 48 h after CIDR removal. The apparent conception rates for the two types of semen were 65·4% and 64·5% respectively (P > 0·1) and the actual fawning rates were 500% and 48·4% respectively (P > 0·1).

In the second trial involving an investigation of the feasibility of laparoscopic intrauterine insemination, 55 does were synchronized as for the first trial. At 56 to 58 h from CIDR removal, the does were anaesthetized and laparoscopically inseminated with frozen-thawed semen (85 × 106 motile spermatozoa per animal) by direct injection into both uterine horns. Anaesthesia was reversed immediately following artificial insemination. The apparent conception rate was 47·3% and the actual fawning rate was 41·8%.

Data from both trials indicate that reasonable fawning rates can be obtained for artificially inseminated fallow deer. Between 11 and 25% of does expected to fawn did not and this may represent embryonic mortality attributable to the method of oestrus/ovulation synchronization.