To investigate the effect of dietary fat and metabolizable energy (ME) on milk protein concentration, an experiment was carried out using 12 multiparous early-lactation Holstein-Friesian dairy cows. Three diets were offered in a complete Latin-square change-over design, based on ad libitum access to grass silage. One of three concentrates was offered at a rate of 12 kg/day, each formulated to supply one of two levels of ME (12·1 and 13·6 MJ/kg dry matter (DM)) and one of two levels of fat (31 and a mean of 88 g acid hydrolysis ether extract per kg DM): low energy, high fat (LEHF); low energy, low fat (LELF); and high energy, high fat (HEHF). The concentration of milk protein was significantly higher from animals offered the LELF concentrate (32·5 v. a mean of 31·2 (s.e.d. 0·45) g/kg, P < 0·05), because of lower milk yields (31·0 v. a mean of 33·4 (s.e.d. 0·63) kg/day, P < 0·05). Animals offered the HEHF concentrate produced the highest yields of milk protein but their milk had the lowest concentrations of fat (32·5,34·4 and 31·9 g/kg for LEHF, LELF and HEHF respectively; s.e.d 1·07; P < 0·05 for difference between LELF and HEHF). Silage DM intake was significantly increased by animals offered the LEHF concentrate (9·1, 8·6 and 8·7 (s.e.d. 0·19) kg/day, P < 0·05 for differences between LEHF and the other two concentrates). Urinary purine derivative excretion, used as an index ofmicrobial protein supply, was highest from animals offered the LELF and HEHF concentrates, which both supplied similar amounts of fermentable ME. It is hypothesized that increased de novo synthesis offatty acids on the low fat diet reduced the availability of glucose for lactose synthesis, leading to reduced milk yields and hence increased milk protein concentrations.

Haemorrhagic lesions, heel erosions and changes in foot conformation have been associated with husbandry, underfoot conditions and nutrition of dairy cows.

These characteristics were monitored in 40 heifers in a 2 × 2 factorial design starting in the last trimester of pregnancy and continuing until 12 weeks post partum. Primary treatments were housing in straw yards or cubicles and secondary treatments were alternative complete diets given during lactation which differed in concentrate: forage ratio. A scoring system was developed for each of the foot lesions to allow statistical analysis of results. Locomotion scoring was carried out weekly.

White line haemorrhages, sole haemorrhages and heel erosions were all present before calving. White line haemorrhages were exacerbated by housing in cubicle yards and alleviated by housing in straw yards (P < 0·001) with an interaction between diet and housing around calving (P < 0·05). Sole haemorrhages were exacerbated both by housing in cubicle yards (P < 0·01) and the high concentrate diet (P < 0·01) with an interaction between diet and housing around calving (P < 0·05). Heel erosions were exacerbated (P < 0·05) by housing in straw yards but not affected by diet. Sole haemorrhage and heel erosion scores generally increased during early lactation (P < 0·001) independent of the treatments. There was evidence that these foot lesions were not caused by laminitis. There was a higher incidence of lameness for heifers given the high concentrate diet but no correlation between locomotion score and the type of lesion or lesion score.

Fifty-five multiparous Holstein-Friesian cows were used to evaluate the short- and long-term effects of varying the crude protein (CP) content of concentrates offered at a low level (5 kg/day) along with ad libitum access to a high quality grass silage. Three dietary treatment groups in lactation weeks 4 to 22 received concentrates containing either 156 (L), 247 (M) or 338 (H) g CP per kg dry matter; from weeks 13 to 21, half of the L animals changed over to the H concentrate and vice versa so that there were five treatment groups (LL, LH, MM, HL and HH). Feeding M or H compared with L increased silage voluntary intakes (P <0·05) and the yields of milk (P <0·05), fat (P < 0·05) and protein (P < 0·01). Milk protein concentration increased with level of concentrate CP (P < 0·05). Pattern of concentrate CP supply (comparison ofLH, MM and HL) had no significant effect on intake or yields of milk and milk solids across the experiment (weeks 4 to 21), though cows gained less weight on treatment HL than on LH (P <0·05) or MM. Intake, milk and component yields were all markedly affected by a change in concentrate CP at week 13; there were positive effects of additional CP (LL v. LH) and negative effects of reduced CP (HH v. HL) on silage intake (P <0·05), as well as milk yield (P < 0·001), milk protein yield (P < 0·001) and milk protein concentration (P < 0·001). Responses to increased concentrate CP were of a similar magnitude in early and midlactation; extra concentrate CP can recover depressed yields and concentrations of milk protein in established lactation. Production responses to concentrate CP involved a concomitant increase in silage voluntary intake.

Cattle breeds of African, European and Indian origins are being evaluated at Rockhampton for their suitability for beef production in northern Australia. In the current study, Belmont Adaptaur (HS), Belmont Red (AX) and Belmont BX (BX) dams were mated to produce straightbreds and crossbred progeny by Brahman (B), Boran (Bo) and Tuli (Tu) sires. B dams were mated to produce straightbreds and crossbred progeny by AX, BX, Bo, Charolais (Ch), HS and Tu sires. This paper reports values for heterosis for some crosses and live weights on pasture for some straightbred and crossbred genotypes at birth, at weaning and at 18 months.

Heterosis for birth weights was greatest for taurine dam breed × indicine sire breed, generally negative for the reciprocal cross and markedly less for Tu-sired than for B- or Bo-sired progeny. Heterosis was not estimated for Bo and Tu crosses at weaning or at 18 months. At these ages, heterosis for growth includes a component related to resistance to environmental stresses. Thus, heterosis was then greater for B crossbreds derived from the less resistant HS than from the more resistant AX.

There were significant differences between genotypes in live weights at each age. Progeny by B sires from taurine dams had higher live weights than progeny by Bo or Tu sires. Evidence is presented that strongly indicates that the difference in growth rates between the B- and Bo-sired progeny arose entirely from differences in mature live weights of the B and Bo, not from differences in efficiency of growth of their crossbred progeny. Similarly, live weights of progeny by taurine sires from B dams ranked according to the mature live weights of the sire breeds. Thus, the Ch- and Tu-sired progeny had the highest and lowest live weights at all ages respectively. Comparative growth potentials of the indicine sire breeds were estimated by comparing 18-month live weights of progeny from HS dams. Relative to Bo = 100, growth potential of B = 205. Similarly, growth potentials of the taurine sire breeds were estimated from progeny from B dams. Relative to Tu = 100, the estimates were HS = 104, AX = 111 and Ch = 117. Crossbred progeny by B and Bo sires were generally significantly heavier at all ages than the corresponding straightbreds. However, Tu-sired progeny had similar birth weights too, but generally higher weaning and 18-month live weights than, the corresponding straightbreds. Relatively low birth weight and low heterosis for birth weight identify the Tu as a potentially useful sire breed when an increase in birth weight of crossbreds is undesirable.

Within each dam breed, no straightbred could match the growth rate of the best crossbred. At 18 months this advantage was proportionately 0·21, 0·09, 0·05 and 0·16 over that of the straightbred HS, AX, BX and B respectively. Live weight of every crossbred based on B dams exceeded that of the straightbred B, the most populous breed in northern Australia. Thus, increases in growth rates could be achieved by crossbreeding irrespective of the base breed. Live weights at 18 month for progeny of Bo, Tu and AX sires from B dams, all of which exceeded those of the straightbred B, suggest that the African breeds can be used to complement the B in crossbreeding programmes in northern Australia.

Cattle breeds of African, European and Indian origins are being evaluated at Rockhampton for their suitability for beef production in northern Australia. In the current study, Belmont Adaptaur (HS), Belmont Red (AX) and Belmont BX (BX) dams were mated to produce straightbreds, and crossbred progeny by Brahman (B), Boron (Bo) and Tuli (Tu) sires. B dams were mated to produce straightbreds, and crossbred progeny by AX, BX, Bo, Charolais (Ch), HS and Tu sires. All animals were reared together in the presence of cattle ticks and gastrointestinal nematodes (‘worms’). Over a 10-month period, half of each genotype was treated every 3 weeks to control ticks and worms. The resistance of each genotype to these parasites was estimated from direct counts of maturing female ticks (‘tick counts’) and from a combination of worm eggs in fresh faeces (‘worm egg counts’) and response to treatment to control the parasites.

The ranking of the sire breeds for tick resistance was B, Bo > BX > AX, HS, Tu > Ch and for worm resistance was B > Bo, BX > AX, Ch, HS, Tu. Only the B × BX and B × Bo could match the resistance of the B to ticks and worms combined.

All genotypes responded to treatment to control parasites but at the low to moderate levels of infestation recorded throughout the study the response of the more resistant genotypes was too low to warrant the cost of treatment. However, the ranking of the genotypes for live-weight gains changed with parasite challenge. Progeny by B and by Bo bulls from each of the dam breeds had higher live-weight gains than the corresponding straightbreds irrespective of the level of parasite challenge but gains of Tu-sired progeny exceeded those of the corresponding straightbreds only at lower levels of parasite challenge. The difference in resistance between the B and the more resistant F2s was small and even at twice the parasite challenge experienced throughout the study, the Fts would still be expected to outgain the B. For those genotypes for which it was measured, heterosis was consistently significant for live-weight gains and for tick counts but not for worm egg counts. Heterosis for live-weight gain was consistently higher for control than for treated groups. Potential roles of the different breeds for crossbreeding is discussed in relation to the effects of different levels of parasite challenge on growth rates of their progeny.

The effect of underfeeding and ref eeding on digestion was studied in Bos taurus and Bos indicus cows. Eight nonlactating cows, four B. taurus and four B. indicus (live weight 156 kg and 207 kg respectively) were first given a forage-based diet at a level above energy maintenance requirements for 4 weeks (3·65 and 4·66 kg dry matter (DM) per day respectively for B. taurus and B. indicus). They were then restricted at a low level of intake for 2 months (1·83 and 2·33 kg DM per day respectively for B. taurus and B. indicus) and finally refed at the first level for 2 months. Digestion measurements were made before the underfeeding period, at 3 and 8 weeks of underfeeding and at 3 and 8 weeks ofref eeding. Organic matter apparent digestibility decreased with underfeeding and increased with refeeding (0·637, 0·591, 0·652, 0·692 and 0·669 in B. taurus and 0·674, 0·560, 0·580, 0·698 and 0·692 in B. indicus, respectively 1 week before, 3 and 8 weeks after underfeeding, and 3 and 8 weeks after refeeding). This lower apparent digestibility at low level of intake was not expected either by ruminal particle retention time, which increased when intake decreased, or by measurements ofmicrobial activity: DM degradability measured in situ and ruminal particle size did not vary with level of intake. An effect of the length of underfeeding and refeeding was seen: the apparent digestibility tended to increase after several weeks of undernutrition and was higher after refeeding than before underfeeding. No difference was observed between the two genotypes.

One of the sources of variation in the in vitro gas production (GP) technique is the inoculum source that is used and this could be greatly affected by the diet that is given to the donor animal. To study the effect of the host diet on the gas production profiles of grass hay and high temperature dried grass, two cows were offered either a silage: barley diet (80:20 dry-matter (DM) basis; GSB) or barley straw (ad libitum; STR). An adaptation period of 3 weeks was used and each animal experienced each diet type twice. Rumen fluid and solids were collected at the end of each 3-week period and used to inoculate the substrate cultures. The volume of gas produced (mllg DM) was 379 and 289 for GSB and STR respectively; gas yield (mllg organic matter degraded) was 442 and 411. The maximum fractional rates of degradation (per h) were 0·067 and 0·061 and the time (h) taken to reach these rates were 5·3 and 12·6. None of these differences was significant. There were also no significant differences in the concentration of total volatile fatty acids (VFA) in the final incubation media, or in the molar proportions of individual VFA. These results suggest that the fermentation stoichiometry was not affected by donor animal diet and, while microbial activity from STR was lower, this did not significantly affect the GP profile. The difference in microbial activity between the two diets was perhaps minimized by taking the sample of rumen contents before the morning meal.

The objective was to determine the effect of age and dietary protein content on post-partum oestrous and ovarian cyclicity in autumn-lambing ewes. Twenty-four multiparous (age 4·5 (s.e. 0·61) years) and 24 primiparous (age 1·5 years) ewes which lambed on 28 October (s.e. 0·2) and were rearing 2·0 and. 1·7 (s.e. 0·13) lambs, respectively, were equally allocated to two dietary treatments in a 2 × 2 factorial design. Diets comprised a d libitum hay supplemented with concentrate (12·5 MJ metabolizable energy per kg dry matter (DM) and either 210 or 140 g crude protein per kg DM), offered at a daily allowance of 1·2 kg per ewe from lambing to weaning (18 December) and 0·4 kg per ewe thereafter. Throughout the study (3 November to 24 May) ewes were group-housed in straw-bedded pens under natural photoperiod at 57°N and their live weights and body condition scores were assessed at 2-week intervals. A raddled vasectomized ram was continually present with each group and ewes marked by the ram were recorded thrice weekly. Blood samples were obtained thrice weekly for measurement of peripheral progesterone concentrations and ovulation rate was determined by laparoscopy during January and March. There was no significant effect of dietary protein content on any of the variables measured. For multiparous and primiparous ewes, mean live weights and body condition scores at lambing were 79·5 (s.e. 1·41) v. 58·4 (s.e. 1·54) kg (P < 0·001) and 2·5 (s.e. 0·05) v. 2·2 (s.e. 0·05) (P < 0·001) and daily live-weight losses over the suckling period were 153 (s.e. 19·3) v. 85 (s.e. 21·1) glday (P < 0·05). Intervals from parturition to first overt oestrus were 39 (s.e. 3·2) v. 33 (s.e. 2·3) days and to the onset of ovarian cyclicity were 29 (s.e. 4·9) v. 25 (s.e. 1·5) days. Durations of ovarian cyclicity were 133 (s.e. 27·1) and 110 (s.e. 5·7) days (P < 0·01) during which 7·6 (s.e. 0·32) and 6·5 (s.e. 0·34) (P < 0·05) ovarian cycles were recorded respectively. Fifteen ewes had initial short cycles (≤10 days), six had prolonged cycles (≥21 days) and 11 had extended inter-luteal phase intervals (≥8 days). All ewes had recent ovulations at the January laparoscopy but only 19 multiparous and nine primiparous ewes had ovulations in March. Mean ovulation rates were: January 2·2 (s.e. 0·14) and 1·4 (s.e. 0·13) (P < 0·001), and March 1·6 (s.e. 0·23) and 1·2 (s.e. 0·15) for multiparous and primiparous ewes, respectively. It is concluded that, for ewes lambing at their normal time of mating, (i) the strong seasonal drive for reproduction results in the resumption of oestrous and ovarian cyclicity during the early post-partum period; (ii) initial luteal phases may be of short or extended duration; (Hi) there is no effect of age or dietary protein content, within the range studied, on the onset of ovarian cyclicity; and (iv) multiparous ewes experience a greater number of ovarian cycles and achieve higher ovulation rates than primiparous ewes.

Increasing amounts of sewage sludge will be applied to agricultural land over the next 10 years as a result of the prohibition of its disposal to the sea. The addition of potentially toxic elements (PTEs) to the soil via sewage sludge is controlled by European legislation designed to limit the accumulation of PTEs in soil which could give rise to toxicity to plants or livestock. However the possibility exists that direct ingestion of sewage sludge and soil together with grazed herbage may result in accumulation of PTEs in body tissues. To assess the extent of accumulation of PTEs by direct ingestion of soil and sewage sludge 12 groups of housed weaned lambs were given diets ad libitum comprising dried grass (900 g/kg total diet dry matter (DM)) and three different soils (100 glkg total diet DM). Soil was replaced by dried digested sewage sludge at levels ofO (level 0), 75 (level 1), 150 (level 2) and 300 g/kg soil DM (level 3). Voluntary intake of DM was markedly depressed by the inclusion of sewage sludge in the diet (on average by 24 g DM per g sewage sludge DM addition). There was no effect of sewage sludge on diet apparent digestibility. Live-weight gain was depressed (P < 0·001) by the addition of sewage sludge to the diet from 236 glday (level 0) to 141 glday (level 3). Liver and kidney weights were also reduced (P < 0·01). The apparent availability coefficients for Cd, Pb and Cu increased with increasing level of sewage sludge in the diet fP < 0·05), as did their concentrations in the liver and kidney (P < 0·01). Concentrations of Cd and Pb in liver increased from <0·07 mg/kg DM and <0·40 mg/kg DM (level 0) respectively to 0·61 mg/kg DM and 4·60 mg/kg DM (level 3) respectively at the end of the trial. Similarly the concentrations of Cd and Pb in kidneys increased from 0·19 mg/kg DM and <0·56 mg/kg DM (level 0) respectively to 0·80 mg/kg DM and 7·10 mg/kg DM (level 3) respectively by the end of the trial. No increases were observed in concentrations of Cd or Pb in muscle tissue. The main effect of type of soil on concentrations of PTEs in body tissues was not significant The daily rate of accumulation ofPb in kidney ranged from 1·1 to 51·5 uglg daily tissue DM growth during the first 57 days of the experiment and from 0·33 to 6·78 /xg/g daily tissue DM growth between day 57 and day 112. A decrease in the second period was also observed for Cd, with accumulation in kidney ranging from 0·31 to 4·44 fig/g daily tissue DM growth during the first 57 days and from 0·21 to 1·44 /jg/g daily tissue DM growth between day 57 and 112. Concentrations of Pb in liver of lambs given the highest level of sludge approached the statutory limit set for human food. The results indicate that in relation to accumulation of PTEs in liver and kidney there would appear to be little margin of safety with respect to the current United Kingdom statutory limits for the concentrations of Cd and Pb in sludge-amended soils. Confirmation of these results is required in the grazing situation.

Current European Union legislation will increase the level of disposal of sewage sludge to agricultural land in the next 10 years. This increase may lead to an increase in ingestion, by grazing animals, of herbage with elevated levels of potentially toxic elements (PTEs) derived from sludge adhered to the herbage or sewage sludge-amended soil resulting in the accumulation of PTEs in body tissues, especially the liver and kidney. To assess the possible accumulation of PTEs from soils treated historically with sewage sludge, eight groups of housed weaned lambs were given either dried grass as a sole food (grass control), or diets comprising dried grass (0·9 of total diet dry matter (DM)) and soil (0·1 of total diet DM) from two experimental sites, plots within which had been treated 14 years previously with different quantities of sewage sludge. Soils from the two sites (Cassington and Royston) had contrasting physical characteristics, pH and contents of calcium. The soil from the site at Cassington was slightly acidic (pH 6·0) and had a concentration of calcium of 7·92 g/kg DM whereas the soil from the site at Royston was alkaline (pH 8·0) and had a high concentration of calcium (23·5 g/kg DM). Plots at each site had a range of concentrations of cadmium (Cd) in the soil up to three times the United Kingdom (UK) statutory limit of 3 mg Cd per kg DM. The soils from these two sites were designated control — no amendment with sewage sludge (0·69 mg Cd per kg DM), low (3·55 mg Cd per kg DM), medium (6·63 mg Cd per kg DM) and high (8·82 mg Cd per kg DM; Cassington soil only). Voluntary DM intake of diets by weaned lambs (mean 1436 glday) was not affected significantly by any dietary treatment. The concentrations of Cd in liver increased (P < 0·001) from 0·061 and 0·072 mg/kg DM (Royston and Cassington control, respectively) to 0·218 and 0·403 mg/kg DM (Royston and Cassington medium, respectively) and 0·500 mg/kg DM (Cassington high). The concentrations of Pb in liver increased (P < 0·001) from 0·733 and 0·627 mg/kg DM (Royston and Cassington control, respectively) to 118 and 1·25 mg/kg DM (Royston and Cassington medium, respectively) and 1·18 mg/kg DM (Cassington high). Similar changes were observed for concentrations of Cd and Pb in kidney. A depletion of the concentration of Cu in the liver was observed in all treatments containing soil in the diet. The rate of accumulation of Cd in the liver ranged from 0 to 0·35 μg/g daily tissue DM growth and in the kidney ranged from 0 to 0·44 μg/g daily tissue DM growth. The rate of accumulation of Pb in the liver ranged from 0 to 6·01 μg/g daily tissue DM growth and in the kidney ranged from 0 to 0·63 μg/g daily tissue DM growth. No significant accumulation of PTEs was observed in muscle tissue. It is concluded that the current UK statutory limits for the concentrations ofCd and Pb in soils treated with sewage sludge should be reviewed in the light of these results, though they require confirmation in the grazing situation.

A study was instigated to test whether grazing herbivores have evolved effective strategies to reduce parasite ingestion and to assess the effects of parasitism on these strategies. Two choice trials, each using five animals parasitized with O. circumcincta and five parasite naive animals, were conducted to investigate cues used by sheep to avoid grazing swards contaminated with faeces. Animals were presented with pairs of artificial swards (36 × 21 cm) and allowed to graze for short periods. In the first trial, four quantities (0 g, 5 g, 15 g and 25 g), and in the second trial a control (no faeces) and three age classes (0, 10 and 21 days old), of faeces were tested against each other. Increasing amount offaeces per sward tray was associated with a reduced proportion of bites taken from the sward and reduced bite depth and mass. The minimum amount of faeces at which sheep showed significant levels of rejection was 15 g. Decreasing age of faeces was associated with a reduced proportion of bites taken from the sward, reduced bite depth and mass. This presented the paradox that grazing swards contaminated with young faeces presented least risk of parasitism, yet fresh faeces presented the strongest stimulus for sward rejection. Parasitism altered animal grazing behaviour with parasitized animals becoming more selective when avoiding contaminated swards, taking smaller bites at reduced bite rates compared with non-infected animals. The enhancement of faeces avoidance behaviours shown by parasitized animals could act to reduce further intake of parasites and suggests that grazing behaviour is affected by nematode infection.

An experiment was conducted to measure the growth and body composition changes of highly selected boars and gilts from 10 to 150 kg live weight. Thirty boars and 30 gilts were given food ad libitum and two pigs of each sex were slaughtered at 10-kg increments from 10 kg to 150 kg live weight at which time the chemical composition of the body was determined. Boars and gilts exhibited different patterns of growth, nitrogen deposition rate (NDR) and lipid deposition rate (LDR) with boars exhibiting a sharp peak in daily live-weight gain and NDR while gilts exhibited almost a flat response curve over the age and weight range tested. Gilts experienced a peak in LDR at a lighter weight than boars (75·8 v. 100·5 kg) while NDR peaked at the same weight for both sexes (70·8 kg). Maximum NDR for boars and gilts was 37·7 and 28·1 glday (235·5 and 175·5 glday protein deposition rate) respectively. The Gompertz growth equation [Y = A + C × EXP (−EXP (−B ×(X−M)))] was shown to accurately represent the growth trajectory, while the logarithmic derivative of the allometric equation [Y = aXb] was used to determine live weight and body composition relationships. Combined sex relationships indicated that total body nitrogen and lipid concentrations increased at the same rate. A quadratic equation for the prediction of NDR based on live weight was developed for this genotype (NDR = 24·06 + 0·34 W − 0·002W2). In conclusion, the results provide a basis for comparison of body composition and growth patterns between the highly selected genotype tested and pigs from other genetic backgrounds. Sex effects exist for growth and body composition but combined sex prediction equations can be used to estimate NDR potential.

An experiment was conducted to examine the effects of dietary lysine/digestible energy (DE) ratio (g/MJ) and dietary energy concentration on growth performance and body composition of young hybrid gilts from 9·1 to 25·4 kg live weight. Seven pigs were assigned to each of 10 dietary treatments consisting of lysine/DE ratios from 0·6 to 1·4 in 0·2 g/MJ increments and two DE concentrations (14·25 and 16·40 MJ/kg). Food was provided ad libitum and at 25·4 kg all pigs were slaughtered and body composition was determined. Responses to lysine/DE ratios were different for each DE concentration. The pigs given the 16·40 MJ/kg DE diets had a higher daily live-weight gain (DLWG) and nitrogen deposition rate (NDR) than those given the 14·25 MJ/kg diets up to the 1·2 g/MJ lysine/DE ratio. Beyond this point no DE effects were evident. Lipid deposition rate (LDR) was higher for all 16·40 MJ/kg diets as compared with the 14·25 MJ/kg diets and decreased with increasing lysine/DE ratio. The 14·25 MJ/kg diets resulted in increasing efficiency of nitrogen and gross energy utilization with increasing lysinel DE ratio up to the 1·0 g/MJ ratio after which it declined. Efficiency of lipid utilization decreased with increasing lysine/DE ratio for all 14·25 MJ/kg diets. The 16·40 MJ/kg diets resulted in a decrease in nitrogen and gross energy utilization efficiency with increasing lysine/DE ratio while lipid efficiency decreased up to the 1·0 g/MJ lysine/DE ratio after which it increased. Young hybrid pigs given high energy diets appear to be less sensitive to dietary lysine/DE ratio than those given lower energy diets. The optimum lysine/DE ratio for the genotype tested from 9 to 25 kg live weight was of the order of 1·2 g/MJ for both DE concentrations. The maximum DLWG and NDR of the genotype tested over the live-weight range of 9 to 25 kg appears to be of the order of 620 and 17 g/day (106 g/day protein deposition rate) respectively.

Ileal digestibility of amino acids in barley-based diets with increasing inclusion of lucerne leaf meal (LLM; 0, 50, 100 and 200 g/kg) was studied in a change-over experiment with post-valve T-caecum cannulated growing pigs. The apparent Heal digestibility of crude protein, as well as of most of the essential (EAA) and non-essential amino acids (NEAA) was not significantly affected by the dietary inclusion of LLM. The exceptions were cystine, methionine, phenylalanine, glutamic acid and serine, all of which showed a significant (P < 0·05) reduction in apparent Heal digestibility with increasing inclusion of LLM. In contrast, the calculated true Heal digestibility of all EAA (with the exception of arginine and lysine) and the NEAA glutamic acid and serine were significantly (P < 0·05) reduced with the inclusion of LLM. Associated with an increased crude protein intake, there was a significant (P < 0·05) increase in the amount of absorbed EAA when the proportion of LLM was increased in the diet. With increasing proportion of fibre in the diet, there was a significant (P < 0·05) increase in the Heal flow of glucosamine.

It can be concluded from the present data that the inclusion of LLM in a barley-based diet for growing pigs will result in an improvement in the absorbed amino-acid profile due to a significant increase in the absorption of all of the EAA.

Forty first cross hybrid gilts were used to study the effect of dietary protein during lactation on free amino acid, protein and total oestrogen concentrations in colostrum and milk. The diets were formulated to contain similar levels of digestible energy (DE) but with either 236 or 186 g protein per kg and 13·3 and 8·1 g lysine per kg air-dried diet respectively. Both diets were offered at 2·5 kg/day for 1 week prior to farrowing and ad libitum throughout a 24-day lactation (no. = 20 gilts per treatment). Colostrum and milk were collected manually at 3h (colostrum), 3, 7, 14 and 22 days (milk) post partum. Free amino acid concentrations in colostrum and milk were determined by high-performance liquid chromatography following derivatization of the amino acids by 9-fluorenylmethyl chloroformate. The lysine and glutamic acid concentrations in colostrum were the most abundant free amino acids followed by tryptophan and taurine in order of decreasing abundance. Milk free taurine concentrations increased to the greatest extent among all free amino acids over the 21 days of lactation. Gilts' mature milk was rich in free taurine, glutamic acid, glycine and lysine. During the first 3 h post partum, the protein content of colostrum was unaffected by dietary protein. However, milk protein content over 7 to 21 days of lactation was significantly higher in gilts offered the higher protein diet (P < 0·001). Total solids in colostrum and milk was not significantly affected by dietary protein. At 3h and 3 days post partum the concentrations of total oestrogen in colostrum and milk, determined by radioimmunoassay, were significantly higher in gilts offered the high protein diet (P < 0·05). These finding indicate that a high protein diet in late gestation and during lactation can influence protein content, amino acid and oestrogen concentrations of milk in gilts.

Thirty-five gilts grown between 18 and 55 kg live weight were used to examine the effects of feeding fermentable carbohydrate on voluntary food intake, performance, carcass characteristics, and large intestinal growth. Five diets were used. The first diet contained steam-flaked sorghum and a supplement based on animal protein sources and 40 g/kg soya-bean meal (diet SAP). Using this diet as a base, three other diets contained either (i) guar gum, a source of soluble non-starch polysaccharide (NSP) (diet SAP + S-NSP), (ii) Novelose™, a source of resistant starch (RS) (diet SAP + RS), and (Hi) a combination of both S-NSP and RS (diet SAP + S-NSP + RS). The final diet (diet WBL) was based on wheat, barley and Australian sweet lupins. Diets (i), (ii) and (Hi) were formulated such that the concentrations of soluble NSP, oligosaccharide and RS were similar to those contained in diet WBL. There was no relationship (F > 0·05) between voluntary food intake and indices of hind-gut fermentation, although pigs given diets SAP + S-NSP and SAP + S-NSP + RS took longer to reach the slaughter weight of 55 kg (F < 0·001) and converted food less efficiently than pigs given other diets (F < 0·001). An increased intake of S-NSP (R2 = 0·842, P < 0·05) and S-NSP + RS (R2 = 0·805, F < 0·05) was positively correlated to an increased (empty) weight of the large intestine. A significant negative relationship (R2 = 0·78, F < 0·05) existed between the daily intake of S-NSP + RS and dressing proportion, such that each gram increase caused a 0·25 g/kg decrease in the dressing proportion of pigs. No such relationships existed between the daily intake of soluble NSP, insoluble NSP, or RS (P > 0·05) with dressing proportion. These data suggest that the sources of fermentable carbohydrate used in this study, i.e. soluble NSP and RS, may not significantly depress voluntary food intake but can affect performance and have a significant effect on large intestinal growth and dressing proportion.

The effect of method of blood sample collection (automatic blood sampling equipment (ABSE) v. manual) on cortisol and progesterone concentrations was investigated in 20 farmed red deer hinds and 20 domestic sheep ewes following dexamethasone and exogenous ACTH administration. Ten animals were subjected to either automatic sampling or manual sampling via jugular venipuncture in 1 week, with the treatment groups reversed in the 2nd week. The ABSE was programmed to collect a blood sample, then deliver 2 mg dexamethasone, collect a further blood sample 120 min later and then inject 100 fig ACTH. Thereafter, samples were collected at 15-min intervals during a 2·5 h period (12 samples in total). In the manual injection and sampling treatment, four samples were collected: (1) before dexamethasone administration, (2) before ACTH administration, (3) 60 min after ACTH administration, and (4) 150 min after ACTH administration. The success rate of blood sampling with ABSE was 80%. The overall mean packed cell volume (PCV) from samples collected by ABSE from both hinds and ewes was significantly lower than that from samples collected manually (P < 0·01) and PCV declined with time in manually sampled animals (P < 0·01). Plasma cortisol concentrations peaked at 45 min after ACTH administration in sheep and deer. In sheep, there was a marked fluctuation in the plasma cortisol concentrations with time. Both deer and sheep showed a reduced cortisol response to ACTH during week 2 irrespective of sampling method suggesting down-regulation of the response to ACTH. Maximum mean plasma progesterone concentration was reached at 15 to 30 min after ACTH administration. No significant differences in cortisol and progesterone responses due to blood sampling method were found in animals receiving prior dexamethasone treatment. This demonstrates that the ABSE has the ability to be used to effectively conduct ACTH stimulation tests without the need to handle the animals during the test.

The amino acid composition of cat hair was determined by conventional 24-h acid hydrolysis and non-linear least-squares extrapolation to time zero of the amino acid composition data from a series of hydrolysis intervals. Twenty-five individual samples of cat hair, consisting of four colours, were also analysed (24-h hydrolysis) to determine if there was an effect of hair colour on amino acid composition. Amino acids were determined following HCl hydrolysis (6 mol/l) with cysteine and methionine determined by performic acid oxidation of the sample prior to hydrolysis.

There was no significant (P > 0·05) effect of hair colour on the amino acid composition of cat hair. The non-linear compartmental model used to determine the amino acid composition of cat hair took into account the simultaneously occurring processes of hydrolysis and degradation of amino acids over time. The amino acids cysteic acid, methionine-sulphone, threonine and serine exhibited high loss rates during 6 molll HCl hydrolysis while the peptide bonds involving valine and leucine were slowly hydrolysed. Amino acid nitrogen accounted for 0·94 of the total nitrogen in cat hair when determined by conventional 24-h hydrolysis and 0·99 of the total nitrogen when the compartmental model was applied. The average nitrogen proportion in cat hair protein was found to be 0·175. The amino acid composition of cat hair protein is comparable with that of dog, horse, sheep and human hair although the proline content of cat hair protein appears to be lower than that in the other species.

Genetic and phenotypic variation in post-weaning growth, food intake, efficiency and body composition of mice post weaning and at maturity, were examined to determine whether genetic variation in efficiency exists and to predict likely responses to selection for increased food efficiency in post-weaning animals. Genetic variation was found for average daily gain, mid-weight, daily food intake and proportion of body fat both post weaning and at maturity. Residual food intake calculated from phenotypic regression had a heritability of 0·27 (s.e. 0·06) post weaning and 0·24 (s.e. 0·08) at maturity, and was very similar to residual food intake calculated using genetic (co)variances, indicating genetic variation in efficiency exists in post-weaning and mature mice. Although the phenotypic correlation between residual food intake post weaning and at maturity was low (0·29), the genetic correlation was moderate (0·60). This suggests that selection for efficiency in young animals will lead to a correlated improvement in maintenance efficiency of mature animals. Genetic correlation estimates suggest that correlated responses in other traits would include a concomitant decrease in post-weaning food intake, a slight increase in weight at weaning, a slight increase in post-weaning fat proportion and little or no change in post-weaning growth. In mature animals there will be an associated decrease in daily food intake and a slight decrease in mature size and body fat proportion. The results suggest that residual food intake of young animals might be a suitable selection criteria for use in livestock species to improve efficiency in young animals and also in the breeding herd.