The efficacy of a single injection of oestradiol benzoate, or a combination of pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG), for the induction of a fertile oestrus and ovulation in the prepubertal pig was investigated in two experiments.

In the first experiment, 1·2 mg of oestradiol benzoate induced 21/23 gilts to ovulate, and 22/23 gilts showed oestrus and were inseminated on day 4 or 5 after treatment. At 28 days after insemination, 12 gilts were pregnant and carrying a mean of 7·1 (s.d. 3·3) live embryos, giving an embryonic survival rate of 0·703. All the 22 gilts treated with 400 international units PMSG plus 200 international units HCG as a single injection ovulated but only 10 showed oestrus and were inseminated. At 28 days after insemination, six gilts were pregnant with a mean of 13·0 (s.d. 5·8) live embryos, giving an embryonic survival rate of 0·583.

In the second experiment, 9/11 oestradiol benzoate and 10/10 PMSG/HCG gilts ovulated in response to treatment. Oestrous detection and insemination were delayed until the expected time of the second oestrus, 20 to 30 days after treatment. Nine gilts (3 oestradiol benzoate, 6 PMSG/HCG) showed oestrus in this period and eight were inseminated. Five gilts were pregnant 28 days after insemination with a mean of 11·4 (s.d. 1·1) live embryos, giving an embryonic survival rate of 0·860.

The relation between the weight of the alimentary tract contents and the weights of body fat and the uterus was examined in 23 Blackface ewes. Six ewes were not pregnant, five had single foetuses and 12 had twins. The pregnant ewes were slaughtered three or four days before their expected lambing date. There was a negative relation between uterine weight or body fat weight and the weight of alimentary tract contents. The effect of uterine weight was small and not significant when only the pregnant animals were considered. It was unlikely that physical restriction of the alimentary tract by the uterus played more than a minor role in limiting voluntary food intake under the conditions of this experiment.

Somatostatin (SS) is a hormone that inhibits the secretion of growth hormone. Immunization against SS can promote the growth of animals. A novel SS-VP22 fused vaccine, pEGS2SS-V, was constructed from pEGS2SS plasmid with a VP22 gene fragment. Two times of immunization with pEGS2SS-V-induced anti-SS antibodies in mice. Compared with mice immunized with pEGS2SS and 0.85% saline, the growth performance of mice immunized with pEGS2SS-V was increased by 14.1% (P < 0.05) and 48.4% (P < 0.01) on the 2nd week after the first vaccination, respectively. The results indicated that the effects of the somatostatin DNA vaccine could be improved effectively by VP22 gene adjuvant.

An experiment was carried out to study the effect of changes in either the quality or the quantity of dietary protein intake on the excretion of nitrogen (N) compounds in the chicken. Thirty-two White Rock male broilers (1 day old) were raised in batteries and fed a commercial starter diet for 9 days. Then they were randomly divided into eight groups each of four birds, of similar body weight (mean live weight: 178 (s.e. 1·9) g), and individually housed in metabolism cages. Following a paired-feeding design based on metabolic body weight (kg M0·75), each group of birds was given, for an experimental period of20 days, each of four levels of protein (60, 120, 180 or 240 g/kg: 5 days each) in two groups of isoenergetic (14·5 kj metabolizable energy per g dry matter) and semisynthetic diets based on soya-bean meal, known to be first limiting in methionine, either unsupplemented (diets S) or supplemented with 2 g/kg DL-methionine (diets SM). Excreta were collected every 3 days for 48 h, frozen and stored at −20°C. The excreta samples were subjected to chemical analysis for uric acid by a rapid high-performance liquid chromatographic method, for urea and ammonia by a colorimetric method, and for total N by the Kjeldahl procedure. In general, the excretion of major N compounds was markedly affected by either the quality or the content of dietary protein. Overall, the excretion of total N, uric acid-N, ammonia-N and urea-N significantly (P < 0·05) decreased with improvement in dietary protein quality and significantly (P < 0·05) increased with increase in protein intake. Regression equations were obtained relating the excretion of uric acid, urea, ammonia and total N on protein supply. For the partition ofN compounds output, the ratios of uric acid-N and ammonia-N to total N significantly (P < 0·05) decreased on improving dietary protein quality and increased or remained unchanged, respectively, with the increase in dietary protein content. The use of the ratio of ammonia-N to total N is recommended as a rapid, easy and accurate indicator of dietary protein adequacy, as an alternative to measures based on total N balance, without the need for separation of urine and faeces.

Nineteen pluriparous buffaloes of Nili-Ravi breed which calved during the months of October and November 1983 were studied for the effects of sucking stimulus on the uterine involution, post-partum ovarian functions and fertility. On the day of calving, buffaloes were assigned to either a limited-suckling (LS) or non-suckling (NS) group. Changes in reproductive organs were monitored by rectal palpations at weekly intervals. Buffaloes were observed for oestrus twice daily (04.00 and 18.00 h) with the help of a teaser bull, and were artificially inseminated at the first post-partum and each subsequent oestrus. LS buffaloes had a shorter period to uterine involution (20 days) than NS buffaloes (28 days). Intervals to regression of the corpora lutea of pregnancy and to resumption of post-partum follicular development did not differ in the two groups. LS buffaloes had longer intervals to first post-partum oestrus and conception (54 and 88 days respectively) than NS buffaloes (39 and 68 days respectively). However, the difference in services per conception of LS and NS buffaloes was non-significant (2-05 v. 1·62). These limited data reveal that the suckling stimulus has a negative effect on the post-partum resumption of oestrous activity, and that conception is delayed. Further studies are indicated to verify these observations in a larger sample size and during all seasons of the year.

Six groups of eight 2-day-old calves were placed successively in a controlled environment chamber. Three groups were exposed to air temperatures of 10° and 25°C. A liquid diet of skimmed-milk substitute and 4 I/day of drinking (free) water was offered to each calf. Within each group, calves were allocated to either a low (<0·2 m/s) or a high (>3 m/s) air velocity and to either a low (30 g dry matter (DM) per kg M0·75 per day) or a high (40 g DM per kg M0·75 per day) feeding level. At 8 days of age the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·77 (s.e. 0·126) and 0·82 (s.e. 0·126) respectively (P > 0·05). The apparent digestibilities of DM were greater at the low feeding level with low air velocity than for either this feeding level with high air velocity or the high feeding level at both air velocities (P < 0·05) between which there was no significant difference (P > 0·05). At 8 days of age there were significant air temperature × air velocity (P < 001) and air velocity × feeding level interactions in the intake of free water (P < 005). There was a significant air temperature × feeding level interaction for total water intake (P < 0·05). Urinary water loss relative to total water intake was significantly greater at the low air velocity than at the high air velocity (P < 0·05).

In a further two groups of eight calves given 30 g DM per kg M 75 per day at 8 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·71 (s.e. 0·020) and 0·90 (s.e. 0·013) respectively (P < 0·01). In the same calves given 40 g DM per kg M0·75 per day at 20 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·89 (s.e. 0·009) and 0·93 (s.e. 0·011) respectively (P < 0·05). The free and total water intakes, the ratios of (total water intake-faecal water loss): total water intake and the urinary losses of water were significantly greater at the air temperature of 25°C than at 10°C (P < 0·05). Live-weight gains were lower at 10°C than at 25°C (P < 0·01).

The results suggested that air temperature, air velocity and feeding level can affect the health and growth of calves less than 4 weeks of age.

Fourteen red deer, three hinds and 11 stags, ranging from birth (8·8 kg) to 10 years of age (143·4 kg), were slaughtered and the carcasses dissected into individual muscles and bones.

Regression equations relating the actual weight of each component or group of components to independent variables such as age, live weight, carcass weight, total muscle weight or total bone weight were fitted to the data, the majority of which satisfactorily conformed to simple allometric relationships. Twenty of the muscles and one muscle group exhibited a pattern of growth which was better described by the inclusion of a quadratic function. The description of the data using an additional term in the allometric equation was considered to be more biologically sound than the often-used practice of fitting different coefficients to the logarithmic form of the allometric equation for each stage of growth. The group of muscles surrounding the thoracic and lumbar vertebrae and those of the abdominal wall were the fastest growing, both having a growth coefficient of 1·08 with standard errors (s.e.) of 0·013 and 0·017 respectively. The slowest growth was found in the distal forelimb group of muscles (growth coefficient = 0·84, s.e. 0015), no individual muscle in this group having a growth coefficient greater than 0·9.

The bones of the axial' skeleton increased in weight faster than those of the appendicular skeleton. The growth coefficients were, axial 1·13, forelimb 0·93 and hindlimb 0·92 (s.e. 0·025, 0013 and 0·015, respectively).

The muscles of the proximal hindlimb were slightly heavier in the hind, and those of the dorsal neck and shoulder heavier in the stag.

Only one minor anatomical variation was found which was related to the insertion of the m. rhomb oideus.

Glucocorticoids (GCs) are counterregulatory hormones with broad effects on the digestion and absorption of dietary carbohydrates, lipids and proteins, but the underlying molecular mechanisms of these effects remain unclear. The present experiment was conducted to investigate the main expression sites of nutrient transporters and the effects of GCs on the gene expression of these transporters in the rabbit small intestine. The results showed that peptide transporter 1 (PepT1), facultative amino acid transporter (rBAT), neutral amino acid transporter (B0AT), excitatory amino acid transporter 3 (EAAT3), sodium-glucose transporter 1 (SGLT1) and glucose transporter 5 (GLUT5) were mainly expressed in the distal segment, glucose transporter 2 (GLUT2) and fatty-acid-binding protein 4 (FATP4) were mainly expressed in the proximal segment and cationic amino acid transporter 1 (CAT1) was mainly expressed in the middle segment of the rabbit small intestine. In addition, we analysed the effects of 3 h (short-term) or 7 days (long-term) dexamethasone (DEX) treatment on the gene expression of most nutrient transporters. The results showed that short-term DEX treatment significantly decreased PepT1, B0AT, EAAT3, rBAT and SGLT1 expressions in all small intestinal segments, while it significantly decreased GLUT2 in the duodenum and FATP4 in the duodenum and ileum (P < 0.05). Long-term DEX treatment also significantly decreased PepT1, CAT1, B0AT, EAAT3, rBAT and SGLT1 in all small intestinal segments and significantly decreased GLUT2 in the jejunum and FATP4 in the ileum (P < 0.05). In conclusion, DEX could decrease the gene expression of most nutrient transporters (except GLUT5) and affect the transport of intestinal amino acids, monosaccharides and fatty acids.

1. Seventy-two individually fed, virus pneumonia-free Large White weaners were used to determine the effect of supplementing diets containing either some animal protein or only vegetable protein with either 0·1% CuSO4.5H2O or 2½% E.C. Feed (molasses distillers dried solubles).

2. The marked growth-promoting effect of supplementing a diet containing animal protein with Cu was again confirmed. The response when Cu was added to the all-vegetable diet was significantly less than that on the diet containing some animal protein, the significant improvement in growth rate on the two types of diet being respectively 5·1% and 14·5%.

3. The addition of 2½% E.C. Feed to the diet containing some animal protein significantly increased growth rate by 5·1%. This response was significantly less than that obtained from Cu supplementation. The 3·6% increase in mean growth rate when E.C. Feed was added to the all-vegetable diet was not statistically significant.

4. Whereas Cu improved the efficiency of food utilisation of the pigs, particularly when added to the diet containing animal protein (a significant improvement of 5·2%), E.C. Feed did not on either type of diet. Both Cu and E.C. Feed similarly increased the rate of food consumption of the pigs on both types of diet.

5. There were no differences in the performance of the control pigs given either the unsupplemented diets with animal protein or the corresponding all-vegetable diets.

Over 2 years, 104 Greyface ewes were mated at a synchronized oestrus either in early October or early November. From late September until slaughter at return to service or between 4 and 7 weeks after mating, ewes were fed to maintain their body condition score as previously adjusted by differential group feeding on grass. Ovulation rate and potential lambing rate were derived from counts of corpora lutea and viable embryos at slaughter. Both rates were higher in the early-mated ewes in comparable body condition. Stress factors were implicated as contributing to the decline in ovulation rate with time, while ewes which failed to hold to first mating were largely responsible for the decline in potential lambing rate.

Heritability is a central element in quantitative genetics. New molecular markers to assess genetic variance and heritability are continually under development. The availability of molecular single nucleotide polymorphism (SNP) markers can be applied for estimation of variance components and heritability on population, where relationship information is unknown. In this study, we evaluated the capabilities of two Bayesian genomic models to estimate heritability in simulated populations. The populations comprised different family structures of either no or a limited number of relatives, a single quantitative trait, and with one of two densities of SNP markers. All individuals were both genotyped and phenotyped. Results illustrated that the two models were capable of estimating heritability, when true heritability was 0.15 or higher and populations had a sample size of 400 or higher. For heritabilities of 0.05, all models had difficulties in estimating the true heritability. The two Bayesian models were compared with a restricted maximum likelihood (REML) approach using a genomic relationship matrix. The comparison showed that the Bayesian approaches performed equally well as the REML approach. Differences in family structure were in general not found to influence the estimation of the heritability. For the sample sizes used in this study, a 10-fold increase of SNP density did not improve precision estimates compared with set-ups with a less dense distribution of SNPs. The methods used in this study showed that it was possible to estimate heritabilities on the basis of SNPs in animals with direct measurements. This conclusion is valuable in cases when quantitative traits are either difficult or expensive to measure.

1. The primary growth of a tetraploid red clover was cut from 17 to 19 June and ensiled with formic acid at 3·81/t fresh crop (F), equal volumes of formic acid and formalin at 9 11/t (67 g formaldehyde per kg crude protein) (FF) or wilted and ensiled without additive (W). The silages were given ad libitum either alone or with supplements of dried grass or barley/fish meal at 6·7 g dry matter per kg live weight to 45 British Friesian male castrates, initially 3 months old and 104 kg live-weight.

2. The use of formaldehyde reduced the concentration of fermentation acids and of ammonia-nitrogen in the silage. Wilting the crop increased silage dry-matter content by 74g/kg fresh weight but this silage had the highest concentration of fermentation acids and of ammonia-nitrogen.

3. Digestibilities of diets containing silage FF were lower than those of diets containing silages F and W except when silage FF was supplemented with dried grass (interaction P <0·05).

4. The intake of silage W was on average higher than that of silages F and FF (P < 0·001). Supplements of barley/fish meal and dried grass depressed silage intake to a similar extent (P <0001). When silages were given as the sole feed, calves consuming silage F had higher live-weight gains than calves given silages FF and W (P <001). This effect was not apparent when silages were supplemented with barley/fish meal, but with a supplement of dried grass the calves given silage FF grew more slowly than those given silages F and W.

5. The results are discussed in relation to the possible effect of treatments on the supply of rumen-degradable protein and of amino acids to the animal.

Two experiments were conducted to investigate the relationships between work and intake and digestion of food by draught oxen given millet stover. In the first experiment, intake of millet stover, water intake, live weight, plasma concentrations of triiodothyronine, thyroxine and urea-nitrogen were measured in 18 animals that worked 0, 2 or 4 h/day in sequence during three 3-week experimental periods. Digestibility and rate of passage of food residues through the digestive tract were measured in a second experiment on 12 animals working either 0, 2-5 or 5 h/day in sequence during three 2-week experimental periods. Feeding behaviour was monitored on six animals working either 0, 2-5 or 5 h/day. Work did not affect intake of millet stover, apparent digestibilities and the rate of passage of digesta through the gastro-intestinal tract. This suggests that the nutrient supply from intake of roughages by ivorking oxen is unlikely to be sufficient to compensate for the extra energy expended during work. Food intake was affected by the quality of the millet stover offered. The level of intake of millet stover ivas proportional to the amount of leaves in the stover. Food intake increased also as work progressed. However, animals mobilized their body reserves to perform work. Animals consumed more water on working days than on days they were at-rest in shade. The heat stress that working animals were subjected to did not appear to interfere with their digestive function.

Genetic parameters of veal calves were estimated from data on 510 Danish Red male calves by 39 sires.

Heritability estimates for the growth and carcass traits were low, those for body dimensions and dressing percentage high.

Correlations between the growth and carcass traits indicated no genetic incompatibility in selection.

The problem of achieving simultaneous improvement in the dairy, carcass and growth qualities is discussed. It is suggested that the adoption of performance testing for growth and carcass quality prior to the entry of bulls into AI service, followed by progeny testing for milk and fat yields, would provide the best method of genetic improvement.

Fat metabolism is an important and complex biochemical reaction in vivo and is regulated by many factors. Recently, the findings on high expression of fibroblast growth factor-16 (FGF16) in brown adipose tissue have led to an interest in exploring its role in lipogenesis and lipid metabolism. The study cloned the goat’s FGF16 gene 624 bp long, including the complete open reading frame that encodes 207 amino acids. We found that FGF16 expression is highest in goat kidneys and hearts, followed by subcutaneous fat and triceps. Moreover, the expression of FGF16 reached its peak on the 2nd day of adipocyte differentiation (P < 0.01) and then decreased significantly. We used overexpression and interference to study the function of FGF16 gene in goat intramuscular preadipocytes. Silencing of FGF16 decreased adipocytes lipid droplet aggregation and triglyceride synthesis. This is in contrast to the situation where FGF16 is overexpressed. Furthermore, knockdown of FGF16 also caused down-regulated expression of genes associated with adipocyte differentiation including CCAAT enhancer-binding protein beta (P < 0.01), fatty acid-binding protein-2 (P < 0.01) and sterol regulatory element binding protein-1 (P < 0.05), but the preadipocyte factor-1 was up-regulated. At the same time, the genes adipose triglyceride lipase (P < 0.01) and hormone-sensitive lipase (P < 0.05) associated with triglyceride breakdown were highly expressed. Next, we locked the fibroblast growth factor receptor-4 (FGFR4) through the protein interaction network and interfering with FGF16 to significantly reduce FGFR4 expression. It was found that the expression profile of FGFR4 in adipocyte differentiation was highly similar to that of FGF16. Overexpression and interference methods confirmed that FGFR4 and FGF16 have the same promoting function in adipocyte differentiation. Finally, using co-transfection technology, pc-FGF16 and siRNA-FGFR4, siRNA2-FGF16 and siRNA-FGFR4 were combined to treat adipocytes separately. It was found that in the case of overexpression of FGF16, cell lipid secretion and triglyceride synthesis showed a trend of first increase and then decrease with increasing interference concentration. In the case of interference with FGF16, lipid secretion and triglyceride synthesis showed a downward trend with the increase of interference concentration. These findings illustrated that FGF16 mediates adipocyte differentiation via receptor FGFR4 expression and contributed to further study of the functional role of FGF16 in goat fat formation.

The study examined the effects of harvest time of red and white clover silage on eating and ruminating activity and particle size distribution in feed boli, rumen content and faeces in cows. The clover crops were harvested at two stages of growth and ensiled in bales. Red clover crops had 36% and 45% NDF in dry matter (DM) at early (ER) and late (LR) harvest, respectively, and the white clover crops had 19% and 29% NDF in DM at the early (EW) and late (LW) harvest, respectively. The silages were fed restrictively (80% of ad libitum intake) twice daily to four rumen cannulated non-lactating Jersey cows (588 ± 52 kg) in a 4 × 4 Latin square design. Jaw movements (JM) were recorded for 96 h continuously. Swallowed boli, rumen mat, rumen fluid and faeces samples were collected, washed in nylon bags (0.01 mm pore size) and freeze-dried before dry sieving through 4.750, 2.360, 1.000, 0.500, 0.212 and 0.106 mm into seven fractions. The length (PL) and width (PW) values of rumen and faeces particles within each fraction were measured by use of image analysis. The eating activity (min/kg DM intake; P < 0.05) was higher in LR compared with the other treatments. The eating activity (min/kg NDF intake; P < 0.05) was affected by clover type with highest values for white clover silage. The mean ruminating time (min/kg DM), daily ruminating cycles (P < 0.001) and JM during ruminating (P < 0.05) were affected by treatment with increasing values at later harvest time. The proportion of washed particle DM of total DM in boli (P < 0.001), rumen mat (P < 0.001), rumen fluid (P < 0.01) and faeces was (P < 0.001) highest by feeding LR. There were identified two peaks (modes 1 and 2) on the probability density distribution (PDF) of PW values of rumen mat and faeces, but only one peak (mode 1) for PL values. There was no difference in the mean and mode 1 PW and PL value in rumen mat between the four treatments. The mean PL, mode PL, mode 2 PW and mean PW in faeces were highest for LR (P < 0.05). The mean particle size in boli measured by sieving was higher at white clover compared with red clover treatments (P < 0.001) and the highest value in faeces was found in LR (P < 0.01). The two peaks on PDF for width values of rumen mat and faeces particles are most likely related to the leaves and the stems/petioles. In conclusion, the mean total chewing activity per kg DM was lowest for the white clover silage and increased for both silages due to later harvest time. The mean particle size in boli was smallest for LR, whereas the mean PL and PW in faeces were highest for the LR.

The recent increased prevalence of uterine prolapses in sows around parturition has led to inferences that the prolapses may be associated with hypocalcemia. However, limited data are available to support that hypocalcemia occurs in sows. Hypocalcemia in dairy cows is associated with feeding excess dietary Ca during late gestation. The excess Ca is assumed to suppress homeostatic mechanisms critical to maintain serum Ca concentrations as the Ca demand increases during the early stages of lactation. In this experiment, sows were fed diets with excess Ca during late gestation and early lactation to assess the potential development of hypocalcemia in the peripartum period. Twelve crossbred (Large White × Landrace) multiparous gestating sows were fed a control diet (CON), 0.65% Ca to 0.38% standardized total tract digestible P (STTD P) and 0.67% Ca to 0.38% STTD P in gestation and lactation diets, respectively) or a high Ca diet (HCa, 1.75% Ca to 0.46% STTD P and 1.75% Ca to 0.45% STTD P in gestation and lactation diets, respectively). The diets were fed from gestation day 86 þ ± 1 until the end of lactation (27 þ ± 2 days period). On day 112 of gestation, indwelling venous catheters were placed in each sow. Blood samples were collected at 15-min intervals within four designated times (0700, 1000, 1300 and 1700 h) on gestation day 113 and lactation days 1, 3 and 5. Venous blood pH, gases (pO2, pCO2 and HCO3−), electrolytes (K+, Na+ and Cl−), ionized Ca (iCa), metabolites (glucose and lactate), plasma total Ca (tCa), and P were analyzed. Overall, sows fed HCa diet had greater (P < 0.001) concentrations of blood iCa and plasma tCa than sows fed CON diets. No clinical signs of Ca metabolism disorders were observed. Unexpectedly, concentrations of plasma P in sows fed HCa diets were lower (P < 0.001) than in sows fed CON diets. Plasma P tended to decrease (P = 0.057) as day of lactation increased. Differences between dietary treatments for blood pH, gases, electrolytes and metabolites were not detected (P > 0.05). No evidence for hypocalcemia was detected in peripartum sows fed CON or HCa diets. These data imply that excess Ca in late gestation diets did not result in hypocalcemia during the peripartum period. Future experiments should focus on factors other than hypocalcemia to identify causes of uterine prolapses in sows.

1. Sixteen sows were immunised in late pregnancy with Salmonella pullorum antigen. Sows showed marked differences in serum antibody titre at parturition.

2. Twelve hours after birth, serum antibody titres in the 173 piglets born to the 16 sows were measured. They were positively related to the serum titres of their mother.

3. Marked variation existed in the antibody titres of colostra from different teats and from different sows. No relationship was found between colostral titres and the titres in sow or piglet sera.

4. Sow and piglet serum titres were negatively related to piglet and litter weight gain from birth to 7 days of age.

5. Those piglets with high serum antibody titres at 12 hr. after birth displayed better growth rates and enjoyed lower mortality than piglets with low antibody titres.

Forty-eight Hereford × Friesian cows and their South Devon calves were paddock grazed at high or low stocking rates of 412 or 206 cows and calves per ha in experiment 1, and either paddock grazed or set stocked at high or low stocking rates of 4·12 or 2·74 cows and calves per ha in experiments 2 to 4.

There was no significant effect of grazing system on milk yield, milk composition or calf growth but in experiment 2 paddock-grazed cows gained more weight than those set stocked. Cows at low stocking rates gained more weight than those at high stocking rates and, in general, gave more milk. Calf growth rates were also higher at low stocking rates in experiments 1, 3 and 4 but not in experiment 2. Milk composition was not significantly affected by stocking rate. There were substantial increases in calf live-weight gain per ha at the high stocking rate but, because of a lower gain by cows, the differences in total live-weight gains per ha for cows and calves were much smaller.

1. Two growth trials and a digestibility trial were carried out with a total of 84 British Friesian steers to investigate the substitution of root crops for a part of the concentrates in an all-concentrate diet. In Trial 1 six experimental diets were offered ad libitum and contained, on a dry-matter basis, (1) 100% concentrates, (2) 34%, (3) 66%, (4) 87% sliced swedes and (5) 66%, (6) 87% whole potatoes. In Trial 2, five diets were offered ad libitum and contained (1) 100% concentrates or (2) 34%, (3) 50%, (4) 66%, (5) 100% swedes.

2. In both the growth trials when the steers weighed less than 350 kg live weight, daily dry-matter intake was lower for steers offered the highest proportion of swedes than for steers offered concentrates. Substitution of potatoes for concentrates resulted in a higher daily dry-matter intake and daily live-weight gain than did substitution of swedes.

3. In Trials 1 and 2 rate of live-weight gain and in Trial 2 carcass gain were similar for steers on treatments 1 and 2. In Trial 2 liveweight gain declined from 1-05 to 0-87 kg/day and carcass gain declined from 0-62 to 0-51 kg/day between steers on treatments 1 and 5. 4. The replacement of concentrates with swedes or potatoes did not affect the overall digestibility of dry matter.