Two experiments were carried out to investigate the effect of restricted suckling and milking regimes on milk yield, milk composition and calf growth. Experiment 1 was carried out in temperate conditions in the United Kingdom and experiment 2 under tropical conditions in Mexico. In experiment 1 a Latin rectangle (change-over) design with 3-week periods was used with eight Holstein Friesian cows suckling their Simmental-sired calves. Saleable milk yield (SMY), sucked milk (CSM), milk composition and calf performance were studied. The treatments were: once a day milking (a.m.) with suckling immediately after (1χAM); once a day milking (a.m.) with suckling p.m. (1χPM); twice daily milking with suckling after a.m. milking (2χAM); twice daily milking with suckling after each milking (2χ2χ). The cows were offered maize silage ad libitum and 4·3 kg dry matter (DM) per day of rapeseed meal plus minerals and vitamins. The calves had ad libitum access to concentrates (165 g crude protein (CP) per kg DM) and wheat straw. In experiment 2, 11 B. indicus χ B. taurus cows, suckling their Brahman-sired calves were used in an experiment with the same treatments and experimental design. Cows were offered star grass (Cynodon nlemfuensis) hay ad libitum and 4.0 kg DM per day of concentrate (117 g CP per kg DM). The calves had ad libitum access to concentrate (151 g CP/kg DM), star grass hay and Ramon leaves. For 1χAM, 1χPM, 2χAM and 2χ2χ respectively in experiment 1, the total milk yields (TMY = SMY + CSM) were 17.9, 18.0, 16.7 and 19.5 kg/day (s.e.d. 1.11) and SMY represented 0.70, 0.45, 0.77 and 0.53 of TMY. Corresponding results for experiment 2 were 6.0, 6.2, 7.0 and 7.1 kg/day (s.e.d. 0.32) and 0.69, 0.45, 0.78 and 0.61. Effects of treatment on milk yield and composition were consistent with the feedback inhibitor of lactation theory. It was concluded that different milking and restricted suckling patterns can be used to manipulate saleable milk production and calf growth. Holstein Friesian dairy cattle in a restricted suckling system without the calf presence at milking, behaved similarly to zebu-crossbred cows by reducing milk let down at milking.

Three experiments were undertaken to assess the Zimbabwean donkey. In the first study, 191 male and 144 female working donkeys from Matopos, Nkayi and Matobo districts were weighed. Age, sex and coat colour were recorded and heart girth, umbilical girth, body length and height were measured. There were no differences (P > 0⋅05) in live weight, 142 and 141 kg, heart girth 115 and 115 cm, body length 89 and 90 cm and height 105 and 105 cm between males and females. This suggests that draught potential might be similar between the sexes. Heart girth was the best single predictor of live weight: live weight (kg) = heart girth (cm)2⋅83/4786 (R2 = 0⋅86). Donkeys were similar in size to others in Africa. In the second study, the voluntary dry-matter intake (DMI) of a poor quality hay was measured for 35 days in nine male (mean live weight 150 kg) and nine female donkeys (142 kg) allocated to one of three treatment groups: water available ad libitum, or given every 48 h, or every 72 h. There were significant differences in daily water (P < 0.001) and DMIs (P < 0.05): 8.5, 4.9 and 5.1l and 3.1, 2.8 and 2.7 kg for the three treatment groups, respectively. However even with restricted access to water, donkeys maintained a relatively high DMI. In the third experiment a 3 Х 3 Latin square was designed with three teams of four male donkeys each, either working (5 h/day) I no access to food (5 h/day); not working/no access to food (5 h/day) or not working/access to food 24 h/day, for 63 days. For working and non-working donkeys, there were no significant differences (P > 0.05) in DMI, DM apparent digestibility and mean retention time (MRT) of hay. Time of access to food did not influence DMI. The apparent lack of response was attributed primarily to the poor quality of the hay.

The work performance of two teams of four donkeys (heavy, 680 kg and light, 460 kg) and one pair of Jersey crossbred oxen (646 kg) was compared when they ploughed 4 hi day on four types of soil (clay, redsoil, sandy soil and sandy clay) using two types of plough, a conventional ox plough (40 kg) and a lighter prototype, the ‘Walco’ plough (32 kg) on an experimental farm. Work parameters were also measured with farmers’ cattle and donkey teams ploughing on f arms in Matobo and Nkayi districts. Working speed, power and effective field capacity (ETC) were higher for the ox-team (1·03 m/s, 920 W and 14·5 h/ha for the conventional plough and 0·99 m/s, 745 W and 13·9 h/hafor the Walco plough) and the heavier donkey team (0·87 m/s, 689 W and 14·2 h/hafor the conventional plough and 0·87 m/s, 787 W and 17·3 h/hafor the Walco plough) than for the lighter donkey team (0·59 m/s, 461 W and 22·1 h/hafor the conventional plough and 0·64 m/s, 445 W and 23·4 h/hafor the Walco plough). Expressed as a proportion of live weight or metabolic live weight there were no significant differences in draught forces exerted between teams but power output per unit live weight was greater in the ox-team than in the light donkey team but similar to that in the heavy donkey team. The Walco plough required a lower force (742 N) to operate than the conventional plough (816 N) but apart from this did not have any marked advantages over the conventional plough. On-farm, team sizes of donkeys varied from three to seven animals (team weight 340 kg to 1007 kg) and cattle team sizes from two to four animals (team weights 558 to 1709 kg). Regardless of team number, the heavier teams tended to out-perform the lighter teams (speed range 0·63 to 1·08 m/s, power 395 to 1136 W, EFC 9·1 to 25 h/ha)) with one exception, a well trained team of two oxen (team weight 879 kg, speed 1·02 m/s, power 775 W, EFC 9·1 h/ha). Donkeys tended to plough at a slower pace than oxen, with a lower power output, although when weight differences between teams were equalized (four heavy donkeys compared with two oxen), then there was little to chose between the species. Results suggested that teams of three or more donkeys can effectively be used for ploughing on the soils tested. The results highlighted the importance that team live weight and training/experience have in determining work performance.

A study was conducted to determine whether sheep form conditioned flavour aversions (CFAs) or preferences (CFPs) for food flavours associated, respectively, with excessive or appropriate concentrations of sulphur (S) and also whether the rate of formation and strength of CFAs and CFPs are dependent on the animal's initial S status or the level of administration of S. In experiment 1, 48 mature ewes were conditioned to associate a new food containing a novel flavour with an infusion of S delivered intra-ruminally, or the same food containing another novel flavour with an infusion of distilled water. The same flavours were then used in experiment 2. At the end of each conditioning period, the relative preference for the two flavoured foods was determined by measuring the amount of each food ingested during a two-choice, 20-min preference test. Experiment 1 consisted of two phases. In phase 1 each conditioning period lasted for 5 days and was repeated four times, whereas in phase 2 the conditioning period lasted for 8 days and was repeated three times.

In experiment 1 the sheep were initially in an S-adequate state. In experiment 2, the sheep were re-randomized to treatments and started in an S-depleted state. The conditioning periods also lasted for 8 days and were repeated three times. There was no evidence to support the hypothesis that sheep develop CFAs or CFPs to food flavours associated with S doses in phase 1 of experiment 1. In phase 2, however, sheep formed CFAs towards the food with the flavour they had come to associate with administration of high levels of S. Repeated exposure to the flavour associated with high levels of S led to stronger aversions and there was an interaction between the S dose level and conditioning periods, indicating that the rate of development of these CFAs was highest for the highest S dose levels. The differences between results of phase 1 and 2 were probably due to the different numbers of reinforcements and different intervals between specific flavour/dose associations.

In experiment 2 there was no evidence for the development of CFPs or CFAs to food flavours associated with S doses. The apparent indifference of the sheep to S was probably due to their responding more to their previous experience of the food flavours than to their S status. Spearman rank correlations on flavour preferences indicated that conditioned flavour responses formed in experiment 1 persisted in individual sheep when they were allocated at random into their new treatments in experiment 2 and influenced or masked the formation of new associations. This demonstration of ‘carry-over’ effects highlights the importance of considering an animal’s previous experience of flavours and their associations with post-ingestive consequences when coming to conclusions concerning current development of CFAs and CFPs. These results may also have more general implications for feeding studies in animals that are randomized into treatment groups without regard to their previous feeding experiences.

A comparison was made of sow lying behaviour, piglet aggregation behaviour and performance in crates (no. = 10) and oval pens (no. = 8). Twenty-four hour time-lapse video tapes were made and a farrowing day defined for each sow by noting the 24-h period during which the sow gave birth (09:00 to 09:00 h). Each sow and litter, balanced for parity and time of year, was analysed from 12:00 to 20:00 h during the 24 h immediately following this day. The following analyses were conducted: (1) the number and type of lying behaviour; (2) each litter was scanned every 10 min and at each lying event the number of piglets within 0·3 m of the sow noted; two indices were then calculated, based on the mean of the 10-min scans and the mean for the lying events, for each sow expressed as a proportion of the total litter size. Any dead piglets were removed and cause of mortality established by post-mortem examination. Production data showed that there was no significant difference between litter size at birth and at weaning but overall level of mortality was higher in the pen compared with the crate due to crushing. The majority of crushing events occurred in the first 3 days after farrowing (crate 75%; oval pen 64%). The total number of lying events and related posture changes did not differ between systems; only ‘roll-over’ events (movement from lateral on one side to the other within 10 s) were higher in the oval pen. There was no difference in the proportion of aggregating piglets at the 10-min scans or the lying events. Increased crushing mortality in the pen does not appear to be due to the aggregation behaviour of piglets but to the increased number of sow roll-over behaviours.

Resistance to naturally acquired gastro-intestinal (GI) nematode parasite infections (predominantly Haemonchus contortus) was studied in 166 Red Maasai, 230 Dorper and 294 crossbred (Red Maasai Х Dorper) ewes in the sub-humid coastal region of Kenya. Live weights (LWT), blood packed-cell volume (PCV) and faecal egg counts (PEC) were recorded at mating, 3 months post mating, 1 week before lambing and 1, 2 and 3 months post lambing for four separate lambings that took place between 1993 and 1996. The Red Maasai ewes were more resistant to GI nematode infections than Dorper ewes as shown by their significantly lower FEC and significantly higher PCV at most of the sampling times over the reproductive cycle. The breed difference for FEC was significant in the lactating ewes but not in the non-lactating ewes. At most sampling times, the crossbred ewes were as susceptible as the Dorper ewes in terms of both PCV and FEC, particularly at the 1 and 2 month post-lambing samplings. Resistance was also manifested by a lower proportion of ewes having to be treated with an anthelmintic and a lower mortality rate in the Red Maasai than the Dorper. The Red Maasai ewes were significantly lighter by about 1 to 2 kg than the Dorper ewes at all sampling times. There was a significant increase in FEC and decrease in PCV over the first 2 months of lactation in lactating ewes compared with non-lactating ewes. This peri-parturient increase in FEC occurred in both breeds and the crossbreds but was more marked in the susceptible Dorper ewes.

The purpose of this study was to examine the importance of the genetic and maternal environmental factors influencing the 12-week weight (12WW) of Welsh Mountain lambs and to estimate genetic parameters for this trait. Records of 8880 Welsh Mountain lambs born between 1979 and 1995 were analysed. The records were from the nucleus flock of the CAMDA cooperative breeding group. In this flock selection of replacements had been based on a multi-trait index incorporating lamb growth and maternal ability as important objectives and 12WW as one of the selection criteria. Twelve models were examined, all including direct additive genetic variance and various combinations of genetic and environmental maternal effects. The most appropriate model was chosen based on log-likelihood ratio tests. It included appropriate fixed effects, and direct additive, maternal additive, maternal permanent environment and maternal common environment (litter) random effects that defined proportionally 0⋅21 (h2), 0⋅09 (m2), 0⋅06 (pe2) and 0⋅18 (ce2) of the phenotypic variance. Ignoring the additive maternal effect resulted in inflated estimates of direct heritability and ignoring the environmental effects associated with dam inflated the direct and maternal heritabilities. There was no correlation (P < 0⋅05) between the additive direct and additive maternal effects. Additive direct and maternal breeding values increased by 0⋅12 (s.e. 0⋅006) kg/year and 0Ό3 (s.e. 0⋅003) kg/year respectively. The results demonstrate the effective incorporation of selection index methodology in the context of a hill sheep flock and also the importance of several categories of maternal effects.

Two experiments were carried out simultaneously in a temperate environment (T), at Sourches (west France), with 24 Landrace X Large White sows and in a tropical environment (TRO), in Guadeloupe, France (16° latitude N, 61° longitude W), with 18 Large White sows, to study the effect of incorporating fat into the lactation diet on sow and litter performance. In each environment, multiparous sows were divided into three groups and given either a control diet (C) containing 20 g fat per kg, or the same diet enriched with a 50 : 50 peanut-rapeseed oil mixture, so as to obtain a fat content of 80 g/kg (medium fat, MF) or 140 g/kg (high fat, HF). A restricted experimental diet was supplied to the sows from day 105 of gestation until farrowing and then ad libitum throughout the 28-day lactation period. The piglets all had ad libitum access to solid food from day 21 to day 70. Milk samples were collected 24 h post partum (colostrum) and at day 21 of lactation. Chemical composition of milk was determined and fatty acid composition was assessed by capillary gas chromatography. Compared with T, the TRO sows showed an increase (P < 0⋅001) in rectal temperature and respiration rate but a decrease in food intake (P < 0·01), milk yield (P < 0⋅001) and litter weight gain from birth to weaning (P < 0⋅05) as well as from weaning to day 70, reaching 25 to 30 kg live weight (P < 0⋅05). However, as dietary fat level increased, the T sows showed a linear decrease (P < 0⋅01) in food intake and no significant change in metabolizable energy (ME) intake during the lactation period. In TRO, the MF diet led to a 0⋅22 proportional increase (P < 0⋅01) in ME intake through a change in nycthemeral feeding behaviour. Both environment and increased dietary fat level significantly affected the fat level and fatty acid composition of colostrum as well as mature milk, particularly n-3 polyunsaturated fatty acid concentration in milk. In conclusion, the addition of fat to the lactating sow diet may be more beneficial under high ambient temperatures than in thermoneutral conditions.

This study was undertaken to investigate factors affecting the success of multiple ovulation and embryo transfer (MOET) in Scottish Blackface (no. = 120) and Welsh Mountain (no. = 120) ewes, over a period of 2 years using a laparoscopic procedure for both embryo recovery and transfer. Superovulation was induced with ovine FSH, with 98 to 100% of ewes of both the breeds responding to the treatment. The overall mean superovulatory responses were 15⋅0 (s.e. 0⋅8) and 12⋅5 (s.e. 0⋅7) for Scottish Blackface and 15⋅3 (s.e. 0⋅9) and 12·8 (s.e. 0⋅8) for Welsh Mountain ewes in years 1 and 2, respectively. However, there was a wide degree of variation in superovulatory responses within each breed, with a range of 3 to 29 in Scottish Blackface and 1 to 40 in Welsh Mountain ewes. The mean embryo recovery rate was 71⋅9 (s.e. 3⋅5) % and 69⋅6 (s.e. 3⋅4) % for Scottish Blackface and 57⋅5 (s.e. 4⋅1) % and 60⋅6 (s.e. 3⋅6) % for Welsh Mountain ewes in years 1 and 2, respectively. The mean number of embryos recovered from Welsh Mountain ewes was significantly (P < 0⋅05) lower than that from Scottish Blackface ewes in both years. The lower mean number of embryos recovered in year 2 for both breeds was entirely a reflexion of the lower superovulatory responses in year 2. A significant (P < 0⋅001) relationship was observed between superovulatory response and the number of embryos recovered for both breeds. Some 77% and 72% of Scottish Blackface ewes and 65% and 73% of Welsh Mountain ewes yielded four or more transferable embryos in years 1 and 2, respectively. Neither the mean number nor the mean percentage of transferable embryos per donor ewe differed between breeds or years. A significant (P < 0⋅001) negative relationship was observed between the time of onset of oestrus and both superovulatory response and number of embryos recovered in Scottish Blackface ewes only. Embryo quality was affected by the time of onset of oestrus. In both breeds, the highest proportion of grade 1+2 embryos and the lowest proportion of unfertilized/degenerate embryos occurred in the middle range time, with a reduction in the proportion of grade 1+2 embryos in ewes that came into oestrus either early <19 h) or late (>30 h) after sponge removal. Only one embryo was transferred to each recipient and the embryo survival rates were 76⋅8% and 74⋅6% (Scottish Blackface), and 69⋅6% and 87⋅3% (Welsh Mountain) for years 1 and 2, respectively. Overall the results of this study suggest that MOET is as successful in hill ewes as has been reported for lowland breeds, even without making any major concessions to their hill status.

This study was undertaken to quantify the effect of episodes of subclinical hypocalcaemia on the interval from calving to first ovulation. It incorporated three separate surveys during early lactation of 44 and 60 cows at Mutdapilly Research Station and 56 cows at Wollongbar Agricultural Institute. Twenty-five, 37 and 39% of cows respectively, experienced episodes later than 3 days after calving, of non-parturient post-partum hypocalcaemia, when plasma calcium concentration fell below 2⋅00 mmolll. Episodes of subclinical hypocalcaemia did not affect the interval to first post-partum ovulation in the two experiments conducted at Mutdapilly Research Station but ovulation was significantly delayed in cows that experienced episodes of subclinical hypocalcaemia at Wollongbar Agricultural Institute.

The effect of a dietary supplement of calcium soaps of fatty acids on luteal steroidogenic activity was studied in sheep. Mature 3- to 5-year-old North Country Cheviot ewes were given either a pelleted control diet (C; grass, beet pulp, barley; no. = 15) providing daily, 29⋅8 g nitrogen and 13⋅7 MJ of metabolizable energy (ME) or the same diet with 5% (w/w) of the ingredients replaced with protected lipid (C + CaFA; calcium soaps of fatty acids, Megalac, Volac Etd; no. = 15) for 21 days. The latter diet provided daily 30⋅2 g nitrogen and 15⋅9 MJ ME. At the end of the feeding period the ewes were slaughtered and blood samples and ovaries were collected from individual animals. The numbers of large- (≤ 4 mm diameter) and small- to medium-sized (1 to 3 mm diameter) follicles were recorded and follicular fluids from both size groups were stored for later analyses following centrifugation. Each mature corpus luteum (CL) was isolated from its ovary and sliced to provide a pair of ca. 0⋅3 mm diameter sections. These sections (mean = 163 (s.e.12) mg) were cultured separately (4 h; 39°C; 5% CO2) in 3 ml Medium 199 in the absence or presence of 100 μIU LH. Dietary supplementation of calcium soaps of fatty acids increased progesterone concentrations in the plasma (P < 0⋅05) and follicular fluid (P < 0⋅01 and P < 0⋅05 for large and small to medium follicles, respectively); trigylcerides in plasma (P < 0⋅05); total cholesterol in plasma (P < 0⋅001) and follicular fluid (P < 0⋅001); HDL-cholesterol in plasma (P < 0⋅001) and follicular fluid (P < 0⋅01) and LDL-cholesterol in plasma (P < 0⋅01). Progesterone released by luteal tissue into the culture medium in vitro from ewes given protected lipid was higher than that from tissue of control ewes (P < 0⋅05) and supplementary LH in vitro stimulated progesterone secretion by luteal tissues from both groups (P < 0⋅05). In conclusion, a dietary supplement of calcium soaps of fatty acids altered the intra-follicular environment surrounding the oocyte and follicular cells and enhanced luteal function in sheep.

To understand the mechanism underlying the effect of high-fibre diets on feeding motivation and stereotypic behaviour in pigs, non-pregnant gilts were given either concentrate or a high-fibre diet based on oat hulls and blood samples were assayed for cortisol, glucose, insulin and free fatty acids. The duration of eating was much longer for gilts on the high-fibre diet than gilts given concentrates. Concentrations of cortisol increased with food delivery and this was most pronounced with the concentrate diet. Concentrations of free fatty acids decreased before feeding and those of glucose and insulin decreased temporarily immediately after feeding began. The diet had no marked effect on these changes, although the decrease for insulin was less evident for the concentrate diet. As feeding continued, free fatty acid concentrations decreased, while concentrations of insulin and glucose increased. The increase in glucose and insulin was fastest with the concentrate diet, although post-feeding peak values did not differ. Postprandial cortisol and free fatty acid concentrations did not differ between diets. There was no evidence of a pre-prandial cephalic phase insulin or glucose response to feeding in the gilts although concentrations of both hormones decreased immediately after the gilts began to eat. The high-fibre diet tended to delay the peak glucose and insulin response to meals, suggesting that the reduced feeding motivation following consumption of high-fibre diets does not involve the same mechanism as the increased satiety following increased energy intake. As well as reducing the occurrence of ster eoty pies, high-fibre diets decrease cortisol concentrations at feeding.

Effects of incorporation of urea and saccharose in diets, on intake and digestion by sheep of a 35-day-old pangola (Digitaria decumbens) hay, have been studied according to a 4 × 4 Latin-square design. Sixteen rams were given four diets: hay (C); hay plus urea (U, 23 g/kg hay); hay plus saccharose (S, 60 g/kg hay), hay plus urea and saccharose (SU). Acid-detergent fibre and crude protein (CP) content of the roughage were 395 and 78 g/kg dry matter (DM) respectively. Intake of hay (g DM per kg live weight0.75), supplemented with urea and sugar (42⋅9), was lower (F < 0.05) than with other diets (47.2, s.e. 1.6). The organic matter (OM) total tract and ruminal digestibility of the diet C, S, U and SU were 0.622, 0.590, 0.615 and 0.587 (s.e. 0.007); 0.361, 0.380, 0.378 and 0.345 (s.e. 0.015) respectively. Effective degradation and nylon bag kinetics of DM degradation were higher with U and SU compared with S or C. Few differences were observed between diets for ruminal concentration of volatile fatty acids. The ruminal ammonia concentrations were higher (P < 0.05) for the diets with urea than without urea (78 v. 215 mg/l). The efficiencies of the microbial synthesis (g nitrogen per kg OM fermented in the rumen) were, 23.6, 22.4, 24.9 and 29.3 (s.e. 1.7) for the diets C, U, S and SU respectively.

Even though additional urea increased nitrogen availability for ruminal bacteria, urea supplementation did not affect significantly intake or digestion of the pangola hay of medium CP content used in this experiment.

Early embryo loss is the major cause of reproductive failure in cattle. The effect of short-term changes in energy intake pre- and post-insemination on embryo survival and systemic progesterone was investigated in heifers. Two pasture allowances (low, L and high, H) were calculated on a dry-matter basis to provide 0⋅8 and 2⋅0 times maintenance requirements, respectively. Following oestrous synchronization, heifers (no. = 296) were allocated to either L or H pasture allowance for a 10 day period before artificial insemination (AI). On the day after AI, heifers (no. = 247) were again randomly allocated to either the L or H pasture allowance until either embryo recovery between days 14 to 16 or pregnancy diagnosis at day 30 (AI = day 0). Hence, there were four nutrition treatments; L-L, L-H, H-H and H-L. Blood samples were collected on days 4, 5, 6 and 7 of the pre- and days 4, 5, 6, 7, 13 and 14 of the post-AI oestrous cycle (oestrus = day 0) for determination of plasma progesterone. Embryo survival rate was significantly lower in the H-L (0⋅38) than in the L-L (0⋅70), L-H (0⋅71; P < 0⋅001) or H-H (0⋅65; P < 0⋅01) treatment groups but there was no evidence that the detrimental effect of reduced energy intake after AI was mediated through changes in systemic progesterone.

The live-weight responses, voluntary herbage intakes and diet compositions of two breeds of sheep of different mature live weights, grazing two contrasting hill vegetation communities, were studied over three consecutive grazing seasons. A total of 228 Latxa and 255 Gallega non-lactating ewes, with mature live weights of 42.4 and 33.1 kg respectively, grazed two replicates, each of two 5-ha plots comprising by area either 0⋅3 Calluna vulgaris and 0.7 grass species (Agrostis capillaris, Festuca rubra and Nardus stricta) (treatment C3) or 0.7 C. vulgaris and 0⋅3 of the above grass species (treatment C7).

The Latxa ewes achieved higher rates of live-weight gain than the Gallega ewes under conditions of high availability (sward surface height >3⋅0 cm) of the preferred grass species (A. capillaris and F. rubra) but had lower rates of live-weight gain in the later part of the grazing season when the availability of the preferred grass species was low. In general, the Latxa ewes had higher voluntary herbage intakes per unit live weight and selected a diet of higher digestibility than the Gallega ewes (P < 0⋅001). The composition of the diet was significantly affected by treatment (P < 0⋅001) and was of a higher digestibility in the earlier part of the grazing season (P < 0⋅001).

The results indicate the existence of a significant (P < 0⋅001) genotype × environment interaction affecting diet selection and animal performance. Between-breed differences in diet selection are likely to be important in determining grazing behaviour and thus the suitability of different genotypes for particular environments. Breeds with a small body size are likely to be better suited to the poorer land resources where the availability of preferred species is low.

The accuracy with which several laboratory-based measurements predict the metabolizable energy (ME) value of whole-crop wheat (WCW) was determined. Twenty-six WCW forages differing in variety (cv. Slepjner, Hussar and Cadenza), maturity at harvest (milk, cheese and dough stages) and treatment applied (urea-treated, untreated or acid-based additive treated) were harvested in 2 years and conserved anaerobically in 200·1 barrels. The forages were then scanned using near infrared reflectance spectroscopy (NIRS) and analysed for chemical composition, in vitro rumen fluid-pepsin digestibility, in vitro neutral detergent-cellulase plus gamannase digestibility, in vitro fermentation gas production and in situ rumen degradability. ME was calculated using measured energy losses in faeces and urine and predicted energy losses as methane. The relationships between ME and the laboratory-based measurements were determined by regression. Gross energy was consistently the best predictor of ME (R2 = 0.53 and 0.86 in years 1 and 2 respectively). However the autocorrelation involved, militates against the prediction of ME from gross energy. None of the chemical constituents or biological techniques gave a good, robust prediction of ME. However, an NIRS calibration developed using the WCW samples was highly correlated (R2 = 0.68) with ME. This work therefore suggests that traditional laboratory-based, food evaluation techniques are unsuitable for predicting the ME content of WCW but that NIRS holds promise.

The response of Awassi ewes to graded amounts of supplementary concentrate diet was examined for the first 12 weeks of lactation. The growth rate of lambs and their health status were also investigated. Seventy-five ewes were divided into three equal groups and given a basal roughage diet of shredded wheat straw at a rate of 750 g dry matter (DM) per ewe per day supplemented with a concentrate diet at three amounts, 950 g (low), 1150 g (medium) and 1350 g (high) of DM per ewe per day starting at the beginning of lactation. Ewes were adapted to the diet by feeding daily at a rate of 200 g per ewe during the last 6 weeks of pregnancy. The concentrate was estimated to contain 11⋅8 MJ of metabolizable energy and 182 g of crude protein per kg DM. Ewes and their offspring were housed in a partly enclosed yard. Lambs remained with their dams continuously except for the days of milk yield measurements, when they were separated from the dam for 11 or 12 h. The ewes were examined for subclinical mastitis and the incidence of scouring in lambs was recorded.

Ewes given the high level of concentrate produced more (P < 0⋅05) milk but differences between medium and low groups were significant only up to week 4 of lactation. Total milk yields during the 9 weeks test period were 58⋅5, 70⋅4 and 93⋅3 kg for the low, medium and high groups, respectively. Ewes suckling twins produced more (P < 0⋅05) milk than ewes suckling singles. The rate of weight loss was lower (P < 0⋅01) for ewes given the high feeding regime; these regained their immediate post-lambing body weight by week 10. Sex of lambs and litter size had no effect on body weight loss but ewes nursing twins tended to loose more weight during the 12 weeks suckling period. Lamb growth rates were similar (P > 0⋅05) across treatments. The daily intake of concentrate by the ewes did not affect the incidence of scouring in lambs or mastitis in ewes.

On both economical and biological grounds it is recommended to offer concentrate during the first 9 weeks of lactation at levels >950 g per ewe per day in order to produce an appreciable yield of milk and restore a positive energy balance early in the ewe lactation period.

Two in vitro experiments were conducted in order to determine if microbial fermentation of Eragrostis curvula hay is depressed by high levels of added tallow. Two levels of tallow, to reach 0.06 (T6) and 0.12 (T12) of the ether extract (organic matter basis) in food were compared with a control (T0, 25 g ether extract per kg). The first experiment studied the pattern of gas production. From 24 h onwards, gas volume for T0 was higher (P < 0.05) than for T6 and T12. However, lag time was shorter with tallow, probably because of utilization of the released glycerol. Fermentation of a similar amount of fat included in T6 and T12 as the only substrate (fat-6 and fat-12) depressed gas production compared with the blank, irrespective of fat level. In a second experiment, characteristics of microbial fermentation were studied, including volatile fatty acid (VFA) production, bacterial adhesion to fibrous particles (measured according to purine bases concentration) and polysaccharidase and glycosidase activities, at 6, 12, 24 and 48 h incubation. Total VFA was higher (P < 0.05) in T0 compared with T6 but not with T12. Acetate: propionate ratio diminished with tallow in the food. Higher total xylosidase (P > 0⋅05) and glycosidase (P < 0⋅001) activities were observed for T0 than for T6 and T12 and similar responses were observed regarding specific activities. Bacterial adhesion was not different between T0 and T6 but it was smaller in T12. The inhibition of microbial fermentation by tallow addition is more related to specific polysaccharidase and glycosidase activities, rather than to a depressed bacterial adhesion.

Previous research has shown that supplementing the diet of growing lambs with urea enhances their ability to withstand gastrointestinal infection with the nematode Haemonchus contortus. This study compared lambs given two different amounts (χ 1 and χ 1·5) of the same urea-supplemented diet. One dietary allowance was sufficient to allow uninfected lambs to gain approximately 400 g/week without adverse clinical signs. In contrast half of the H. contortus infected lambs on this dietary allowance had to be humanely killed before the end of the experiment due to severe anaemia and anorexia. All infected lambs on this dietary allowance showed decreased mean red cell volumes and decreased plasma albumin concentrations indicating inadequate replacement of red blood cells and plasma proteins lost during the infection. The remaining lambs were offered proportionately 0·5 more of the same dietary allowance. Among lambs on this dietary allowance, there were very few differences between uninfected and infected sheep in clinical signs and growth rate. Therefore, dietary allowances that are adequate for uninfected lambs are not necessarily sufficient for infected lambs. As nearly all grazing lambs are infected with nematodes, dietary recommendations should take parasitic infection and its nutritional demands into account.