The power for detection of quantitative trait loci (QTL) using marker information was compared in several schemes differing in the mating type and the number of parents involved. An experiment based on an F2 population of fixed size obtained by crossing two lines differing phenotypically for a single trait was simulated, assuming that QTLs could be fixed or segregating in the lines crossed. Different additive and dominant QTL effect values and allele frequencies were considered covering a range of different favourable situations for the detection of the QTL. Comparison was done by regression using flanking marker information. Mating animals at the F1 generation level minimizing relationships was not worse than mating at random or maximizing relationships. The number of parents used affected the power of the experiment when the QTL was segregating in the original crossed lines. Differences in power were mainly related to the number of males from the original line. When the power of the experiment was high as a result of genetic hypothesis assumed, considering several males increased the power. However, when the genetic hypothesis assumed led there to be less power to detect a QTL, the power was higher when fewer males were used.

The effect of ensiling grass and supplementing the resulting silage with water-soluble carbohydrate in the form of sucrose and undegradable dietary protein (UDP) in the form offish meal on forage intake and milk production and composition were evaluated in an experiment involving 63 mid-lactation Holstein-Friesian cows. Herbage from the primary growth of a predominantly perennial ryegrass sward was zero-grazed (ZG) from 19 April to 16 May 1993. The herbage was mown and picked up with a precision-chop harvester and offered as the sole diet, twice daily, to 18 cows which were on average 186 days into lactation. On 13 May, herbage from the same sward was harvested identically to the ZG herbage and ensiled, treated with formic acid at a rate of 2·85 lit grass. At 53 days after ensiling the silage was offered either as the sole diet (SO) or supplemented with sucrose at 10·3 g/kg fresh silage (SS) or supplemented with sucrose and fish meal each at 10·3 g/kg fresh silage (SSF) to 15 cows per treatment which were on average 164 days into lactation. The feeding period was 28 days for ZG and 21 days for the SO, SS and SSF treatments, and the last 7 days were the main recording interval. Prior to going on to the experimental diets all animals were offered a common silage ad libitum and supplemented with 5 kg of a 180 g/kg crude protein concentrate. Dry-matter intakes (DMI), milk yields and milk composition were recorded during the pre-experimental period and subsequently used as covariates in the statistical analysis. For diets ZG, SO, SS and SSF, forage DMI (kg/day), total DMI (kg/day), milk yields (kg/day), fat concentration (g/kg) and protein concentration (g/kg) were 14·4,14·0,13·7 and 13·9 (average s.e.d. = 0·55); 14·4,14·0,14·5 and 15·4 (average s.e.d. = 0·59); 15·4, 14·4, 14·5 and 16·7 (average s.e.d. = 0·42); 36·6, 38·6, 38·6 and 37·5 (average s.e.d. = 2·67); 33·0, 30·7, 32·2 and 32·8 (average s.e.d. = 0·75). Nitrogen (N) digestibility was higher on SO and SSF (P < 0·05) relative to ZG with SS being intermediate, otherwise treatment did not alter (P > 0·05) diet apparent digestibility. Ensilage increased the immediately soluble N fraction (a value) and degradability of N (P < 0·001) relative to ZG. It is concluded that ensilage had no effect on forage DMI but decreased milk yield and protein concentration relative to the parent herbage. The positive response in milk yield due to supplementation of the silage-based diet with sucrose and fish meal and the lack of response to sucrose supplementation alone suggests that nutrients absorbed from the digestive tract of cows offered silage-based diets are more limiting in protein or specific amino acids supplied by fish meal than in energy. The decrease in animal performance due to ensiling may be overcome by supplementation of silage-based diets with UDP at sufficient levels to equate that of the parent herbage.

A partially balanced change-over design experiment was made to examine the effects of concentrate energy source on the voluntary food intake and animal performance of 50 lactating dairy cows offered a diverse range of grass silages. The silages were also offered as the sole diet to 10 dairy cows in a partially balanced change-over design experiment. A total of five silages were prepared. Silages A, B and D and silages C and E were harvested from primary regrowths and secondary regrowths respectively of predominantly perennial ryegrass swards. Herbage was ensiled either pre-wilted or unwilted and either untreated or treated with a bacterial inoculant or formic acid based additives. For silages A, B, C, D and E, dry matter (DM) concentrations were 473, 334, 170, 170 and 256 (s.e. 4·0) g/kg, pH values 4·42, 4·01, 4·88, 4·46 and 3·91 (s.e. 0·059), ammonia-nitrogen (N) concentrations 86, 88, 289, 182 and 135 (s.e. 10·6) glkg total N and in vitro DM apparent digestibilities 0·76, 0·76, 0·75, 0·73 and 0·75 (s.e. 0·009) respectively. When offered as the sole diet DM intakes were 14·1,14·7,10·5,10·1 and 11·5 (s.e. 0·50) kg/day. Five concentrates were formulated to contain similar concentrations of crude protein, effective rumen degradable protein (ERDP), metabolizable energy (ME) and fermentable ME (FME) but using different carbohydrate sources to achieve a wide range of starch concentrations. For the low and high starch concentrates, starch concentrations were 50 and 384 g/kg DM, and acid-detergent fibre concentrations were 128 and 75 g/kg DM respectively. The silages were offered ad libitum supplemented with 10 kg concentrate per head per day. For silages A, B, C, D and E silage DM intakes were 10·6, 10·5, 8·5, 8·6 and 9·0 (s.e. 0·37) kg/day and milk yields 23·9, 28·1, 26·2, 26·1 and 25·0 (s.e. 0·76) kg/day respectively. Concentrate energy source did not influence (P > 0·05) silage DM intake, diet apparent digestibility or the yields of milk or fat plus protein. For concentrates containing 50, 131, 209, 310 and 384 g starch per kg DM, milk protein concentrations were 32·0, 32·2, 32·5, 33·0 and 33·6 (s.e. 0·13) glkg, milk fat concentrations were 44·5, 43·9, 43·8, 43·3 and 43·1 (s.e. 0·35) glkg and urinary allantoin concentrations 15·2,15·4, 17·0, 1.7·6 and 18·0 mmolll respectively. Increasing starch intake resulted in positive and negative linear relationships for milk protein (P < 0·01, R2 = 0·96) and fat (P < 0·01, R2 = 0·96) concentrations respectively. There were no significant concentrate energy source × silage type interactions on silage intake or yields of milk or fat plus protein (P > 0·05). However there was a concentrate energy source × silage type interaction on milk fat yield (P > 0·05). It is concluded that, with silages of varying fermentation and intake characteristics but similar apparent digestibility, there were no concentrate energy source × silage type interactions on food intake, milk composition or milk yield. Also concentrate energy source had no effect on silage DM intake or milk yield. However increasing starch intake linearly increased milk protein concentration, probably due to increased microbial protein synthesis and decreased milk fat concentration.

An analysis has been carried out of over 88000 calving survey records for bulls of eight beef breeds tested in commercial dairy herds in England and Wales. The data were collected from 1981 to 1993. The traits analysed were the degree of difficulty at calving, assessed from no difficulty to serious difficulty, calf mortality to 48 h, gestation length, and subjective assessments of calf size and conformation.

Major sire breeds in the survey were the Hereford (30070 records, 93 sires), Charolais (25816 records, 105 sires) and the Limousin (15420 records, 55 sires). Other sire breeds were Belgian Blue (5391 records, 24 sires), Simmental (3864 records, 19 sires), Aberdeen Angus (2886 records, 12 sires), Piedmontese (2423 records, 7 sires) and the Blonde d'Aquitaine (2271 records, 8 sires).

Information was routinely recorded on cow age (heifer or mature), sex of the calf, and the year and month of the calving, while cow size and the regional location of the herd were also recorded in later years.

Heifers had more difficult calvings, higher calf losses and shorter gestations than mature cows (all P < 0·05) Seriously difficult calvings and calf mortality were higher for male calves, which were also larger and had better conformation than heifer calves (P < 0·05).

Sire breed effects were significant for all traits, although sire breed ranking for calving ease was different for cow and heifer calvings and some interactions involving sire breed were also significant. For cow calvings, the easiest calving breeds were the Hereford (1·1%) and the Aberdeen Angus (1·4%), while the Charolais (4·3%), Blonde d'Aquitaine (3·7%) and Simmental (3·1%) had most difficult calvings.

Gestation length differed between sire breeds, from Aberdeen Angus (281·0 days) and Hereford (282·7 days) up to the Limousin (288·1 days) and the Blonde d'Aquitaine (289·0 days). For calf size and conformation, the Simmental, Charolais and Blonde d'Aquitaine were the best.

In general, summer months were associated with lower incidences of difficult calvings, lower losses and shorter gestations.

Large cows had calves which were larger and of better conformation than small or medium cows, but large cows also had longer gestations, more difficult calvings and poorer calf survival (all P < 0·05).

Statistical models are discussed that should be used for the genetic evaluation of calving survey traits, when beef bulls are to be used in dairy herds in the United Kingdom.

Genetic parameters were estimated for traits recorded in a calving survey for beef sires used in commercial dairy herds in England and Wales. The five traits included in the survey were calving difficulty score, calf mortality to 48 h after birth, gestation length, and subjectively assessed calf size and conformation. The data file examined included over 88 000 records, on 323 sires of eight beef sire breeds, namely Aberdeen Angus, Belgian Blue, Blonde d'Aquitaine, Charolais, Hereford, Limousin, Piedmontese and Simmental.

Estimates of heritability and genetic and phenotypic correlations were obtained for all traits by REML procedures using a sire model. The effects of cow age, calf sex, year and season of the calving and sire breed were included in the model, together with interactions.

Heritability estimates were 0·09 (s.e. 0·01) for calving difficulty score, 0·32 (s.e. 0·03) for gestation length, 0·02 (s.e. 0·003) for mortality, 0·09 (s.e. 0·01) for calf size and 0·06 (s.e. 0·01) for calf conformation.

Heritability estimates for the scored categorical and binomial (mortality) traits were also obtained using threshold model analysis. As expected, these estimates were higher than the REML estimates; 0·16 (s.e. 0·01) for calving difficulty score, 0·08 (s.e. 0·01) for mortality, 0·14 (s.e. 0·01) for calf size and 0·09 (s.e. 0·01) for calf conformation. Calving difficulty score was strongly correlated genetically with calf size (-0·84), mortality (0·74) and calf conformation (-0·72), and moderately correlated with gestation length (0·26). Calf size and conformation were very highly correlated genetically (0·86), and both were also strongly correlated with mortality (-0·63 and -0·52 respectively). In all cases, the genetic correlations were stronger than the phenotypic correlations.

Sire genetic merit was predicted for all traits and the distribution of these predictions is described. Sire predictions of genetic merit for calving difficulty score on the underlying scale were backtransformed to predict the expected incidence of serious difficulties in future calvings and these predictions are illustrated for the major sire breeds.

Two experiments were conducted to compare the response oflactating cows to supplementary light in their lying area during increasing and decreasing natural daylength. During decreasing daylength, supplementary light in the lying area increased the time cows spent lying down and considerably reduced calculated food intake, milk production, live weight and body condition, so that lights were installed in the feeding area for the last half of the experiment, which partially restored intake and live weight. Plasma cortisol concentrations and milk somatic cell counts were increased by supplementary light in decreasing daylength before, but not after, lights were installed in the feeding passage, suggesting that cows may have been stressed by the difficulties encountered during feeding in the dark. During increasing daylength supplementary light did not affect lying time, had less effect on food intake and no effect on milk production or live weight. There was a small reduction in plasma corticosteroid by the end of the experiment with supplementary light. It is concluded that providing supplementary light only in the lying area of dairy cows will have adverse effects on their production and welfare in decreasing, but not increasing daylength

Two studies investigated the effect of contaminated pasture on selective grazing, overall grazing behaviour and the process of defoliation of dung patches through experiments targeted at four major questions: (a) how does relative utilization of tall and short grass change as the sward is grazed down? (b) what effect does herbage mass and sward height have on the relative utilization of short and tall grass? (c) how are tall grass patches actually utilized by cattle? and (d) how is overall grazing behaviour influenced by contamination of the sward?

Experiments were conducted in mid to late season using Friesian dairy cattle. In experiment 1, two -pasture types (topped sward (T) v. grazed-only sward (G)) were used. The distribution of bites on tall grass from both pasture types indicated that the grazing animals tended initially to graze short grass when they met a new sward, and then select tall grass as the swards were progressively grazed down. This switch happened earlier in the defoliation process in the topped sward. In experiment 2 observations were conducted on previously grazed and previously ungrazed swards. The distribution of bites on tall grass showed a similar trend to that found in experiment 1 and as the sward was gradually grazed, biting rate significantly declined. There was also a significantly higher total grazing time on the previously ungrazed sward (no contamination by dung). Comparing data based on a consistent biting rate (calculated as the time for 20 consistent bites) and natural biting rate (calculated as the total time for 20 bites) suggested that the grazing animals had increased difficulty in handling tall grass which may explain the declining biting rate as the swards were being grazed down and more bites were directed at tall grass. The defoliation of tall grass dung patches appeared to be concentrated around the edges of the patch. The average area of sward affected by a single dung pat was 1·04 m2 measured at the pre-grazing stage and was markedly reduced to 0·51 m2 at the post-grazing stage. In conclusion, selective grazing is likely to exist due to the presence of dung and conditioned by dung distribution and sward type and this in turn modifies biting rate during grazing down of a sward.

Sixty-five primiparous cows were used in two experiments to study the effects of feeding high or low levels of concentrate during the last 2 to 3 weeks before calving on performance in early lactation. During early lactation (until 12 or 16 weeks after calving) all the 23 cows in experiment 1 were given the same diet. In experiment 2, the 42 cows were given diets with a ratio of concentrate/forage of either 60:40 or 40: 60, each providing the same energy level.

The food intake of almost all the cows decreased in the few days before calving but the decrease was less pronounced among those on the low concentrate level before calving. The average daily food intake during the calving week gave a metabolizable energy intake about 30 MJ higher on the high compared with the low feeding level. The level of feeding before calving had no effect on the cows' food intake after calving, or on their milk yield, health and fertility, or on scores for udder oedema and sole haemorrhages. The high level offeeding before calving was associated with significantly higher concentrations of insulin and lower concentrations of free fatty acids in the calving week of lactation but the level offeeding either before or after calving had no effect on these concentrations in the 8th week of lactation. The feeding of a high ratio of concentrate/forage after calving was associated with a significantly lower milk fat content. It can be concluded that the concentrate/forage ratio at calving does not seem to have any significance for the performance after calving.

Thirty-two post-partum Mediterranean river buffalo cows were continuously observed for signs of oestrus from September to December with the aid of two vasectomized bulls. Symptoms of oestrus among female Mediterranean buffaloes are weak, therefore oestrus was assessed based on bull behaviour (following and licking a cow and trying to mount her). Oestrus was divided into three phases based on the bull behaviour assessment. Status of the uterus and ovarian follicles were checked rectally every day for each cow which was detected by a teaser bull to be in oestrus. All cows in oestrus were bred twice by artificial insemination (AI), the first at ovulation and the second (using a different bull) 22 h later.

The average duration of interest shown by the bull towards a cow (from the very first to the last sign of interest) was 68 h and the average length of the three phases was: phase 1 = 21 (s.d. 29) h, phase II = 32 (s.d. 24) h and phase III = 15 (s.d. 15) h. Fifteen buffaloes were bled during oestrus, and LH profiles were determined. No differences were evident among oestruses followed by pregnancy (no. = 18) and the others (no. = 26) for the variables describing behavioural events. Neither intensity of the bull courtship, presence or clarity of mucous discharge, or housing system affected the success of AI. The only differences between pregnant and non-pregnant cows were in the timing between the LH peak and the end of phase II (2·4 v. 14·7 h, P < 0·001), end of phase III (22 v. 40 h, P > 0·05) and ovulation (25 v. 46 h, P < 0·05). Successful pregnancies occurred 34 (s.d. 14) h after the end of phase II. The endocrinology and behavioural patterns of buffalo reproduction need further research to clarify the reasons for non-optimal pregnancy rates after AI.

Subtropical grasslands are low in organic matter digestibility (OMD) (0·60) and nitrogen (N) (15 g/kg) for much of the year and this limits cattle production which is characterized by low calving rates and low weaning weights. Production has been based on Bos taurus British breeds of cattle but this is changing and now many breeding herds comprise B. indicus cows and their crosses. This change has increased some aspects of production, but low calving rates persist.

A 4-year study was undertaken with a view to improve calving rates and weaner output by supplementing cows grazing either native or improved pastures with a high protein oilseed meal (cottonseed meal; CSM) on four sites. These sites were subdivided into a total of 36 paddocks to allow for two replications in a 3 breeds × 3 supplementation rates × 2 pastures factorial design. Selected cows (no. = 216) from Hereford (H), Brahman (B) and Brahman × Hereford (BH) breed types were set to graze either native pastures (0·45 to 0·62 OMD, 8 to 15 gN per kg; low quality) or improved pastures (0·47 to 0·67 OMD, 10 to 22 g N per kg; medium quality). Cows were given either 0, 750 or 1500 glday of CSM for 130 days from calving until 4 weeks into a 12- to 13-week mating period. The CSM was given as two meals per week.

Live weight at mating of cows on the low quality pasture was increased (P < 0·01) over those not supplemented by feeding either 750 g CSM per day (H and B cows) or 1500 g CSM per day (all cows). There was no significant effect of supplementation on the mating weights ofB cows grazing the medium quality sites. Calving rate ofB cows was not increased by their supplementation on either low (4-year mean 58·3 %) or medium quality pastures (66·8%) but did tend to be higher in H cows when supplemented at 1500 g CSM per day on the low (66·7 v. 78·0 (s.e. 6·09) %; P < 0·1) and medium quality pastures (70·5 v. 93·5 (s.e. 4·72) %). An increased calving rate (65·8 (s.e. 6·6) % to 83·2 (s.e. 5·82) % in supplemented BH cows grazing low quality pastures approached significance (P < 0·1) when given CSM at 1500 glday but there was no increased trend in calving rate when this breed type was supplemented on medium quality pastures.

Weaning weights of calves from and B and BH cows were increased (P < 0·05) by supplementation of their dams at 750 glday and for calves weaned from H cows supplemented at 1500 glday of CSM. Supplementation at 1500 glday on low quality pastures increased weaner output per cow mated by 120% for H, by 65% for BH cows and by 50% for B cows. Weaner output was increased by 34 and 40%, respectively, for B and H cows when supplemented at 750 glday and grazing medium quality pastures but there was no significant effect of supplementation on output from BH cows. Responses in many parameters differed between years. These results were interpreted as a response to the protein in the oilseed meal supplement by B. taurus and B. taurus × B. indicus cross cows grazing on the subtropical pastures. The study also highlighted that responses to the meal differed between breed types, between the quality of the grazed pasture and between the years of supplementation.

Juke was expressed from two silages of contrasting fermentation type with either high (H) or low (L) levels of lactic acid and reconstituted either with the silage from which it had been expressed or the other silage. This procedure produced four dietary treatments (HH, HL, LL, LH) each differing in fermentation characteristics. The dietary treatments HH, HL, LL, and LH contained 81, 71, 59, and 49 g lactic acid per kg dry matter (DM) and 101, 133, 193 and 159 g ammonia-N per kg total nitrogen (TN) respectively. The four diets were offered to four steers (mean live weight 679 (s.e. 49) kg) in a four-period change-over design experiment. Each period was of 17 days duration. DM intakes were recorded daily, with intakes on days 8 to 17 used in the statistical analysis of data. On day 12 of each experimental period, rumen fluid samples were taken throughout a 24-h period. The rates of disappearance of DM, nitrogen (N), modified acid-detergent fibre (MADF) and neutral-detergent fibre (NDF) in the rumen were determined on days 14 to 17 using the polyester bag technique. DM intakes were 7·2, 6·9, 6·0 and 6·0 (s.e. 0·50) kg/day (P = 0·08) for HH, HL, LL and LH dietary treatments respectively. Diet had no significant effect on eating behaviour, rumen fermentation parameters or degradability of DM, N, MADF and NDF fractions (P > 0·05). Silage L increased rumen fluid pH (P < 0·05), reduced buffering capacity (P < 0·05) and increased the molar proportion of propionic acid and n-butyric acid (P < 0·05 and P < 0·01) compared with silage H. Silage L also had a lower DM apparent digestibility, D-value and DM, (P < 0·001), N and MADF (P < 0·05) degradabilities than silage H. The higher DM intake of dietary treatment HH compared with dietary treatments LL and LH could not be explained by any single constituent of the silages although it was apparent that physical characteristics of the silage were more important in determining intake than the chemical characteristics.

A partially balanced change-over design experiment involving 192 beef steers, which were initially 14 months old and 415 kg live weight, was carried out to determine the intakes of 136 silages from commercial farms in Northern Ireland. Each silage was offered ad libitum as the sole food to 10 animals, with eight silages offered in each of 17 periods over 2 years. A standard grass hay was offered to 16 animals in each period to enable period effects on intake to be removed. Detailed chemical and biological compositions of the silages were also determined. The ranges for pH and dry matter (DM), crude protein, ammonia-nitrogen and apparent digestible organic matter (in vivo) concentrations in the silages and silage dry DM intakes were 3·50 to 5·49 (s.d. 0·396); 155 to 413 (s.d. 43·1) g/kg; 79 to 212 (s.d. 24·4) g/kg DM; 45 to 384 (s.d. 63·2) g/kg total nitrogen; 528 to 769 (s.d. 58) g/kg DM and 4·3 to 10·9 (s.d. 1·13) kg/day respectively. Relationships between intake and individual parameters or groups of parameters have been developed using simple and multiple linear regression analysis and partial least-squares analyses. Silage intake was closely related to factors which influence the extent of digestion and rate of passage of the material through the animal, as indicated by the strong relationships (R2 of regressions = 0·28 to 0·50) with in vivo apparent digestibility and rumen degradability and the concentrations of the fibre and nitrogen factors. Intake was poorly correlated with factors such as pH, total acidity, buffering capacity and the concentrations of lactic, acetic and butyric acids (R2 of regressions = zero to 0·11). Near infrared reflectance spectrometry (NIRS) provided the best fit relationship with intake (R2 of relationship = 0·90). The results also indicate that the intake potential of silages can be directly predicted with a high degree of accuracy from the NIRS of both dried and undried samples of silage, provided the appropriate sample preparation and scanning methods are used.

A 3-year experiment has been carried out to compare systems of bull beef production involving pasture grazing and continuous storage feeding and to examine the effects of sward surface height and concentrate input from 5·5 to 11 months of age on grazing behaviour, growth rate and body composition at the end of the treatment period and on subsequent growth rate and carcass composition at commercial slaughter weight. Animals were either set-stocked at pasture to maintain sward surface heights of 6·5 and 10·0 cm or were given grass silage (725 g digestible organic matter per kg dry matter (DM)) supplemented with 0·8, 1·6, 2·4, 3·2 and 4·0 kg cereal-based concentrates (188 g crude protein per kg DM) per head daily. Half of the animals grazed at each sward height were given 1 -6 kg concentrates per head daily while the remainder received no supplement. A total of 255 continental beef breed × Friesian calves which were initially 198 kg live weight were used. From 11 months of age until slaughter at a mean live weight of 620 kg all animals were given grass silage supplemented with 3 kg cereal-based concentrate DM per head daily.

Reducing sward surface height from 10·0 to 6·5 cm increased the proportion of time spent grazing (P < 0·001), reduced the proportion of time involved in other activities and reduced live-weight gain (P < 0·001) from 1·21 to 0·84 kg/day. Offering concentrates at pasture reduced (P < 0·001) the proportion of time spent grazing (the effect being greater with the animals grazing the shorter swards) but did not affect the performance of the animals grazing the taller swards and produced only a modest increase in the live-weight gain (70 g/kg concentrates) of those grazing the shorter swards. At the end of the treatment period, the carcasses of the animals which had been given silage contained proportionally 0·39 more lipid than those of animals which had been at pasture and had the same growth rate. Differences in live weight at 11 months of age due to differences in feeding from 5·5 to 11 months were largely retained until the end of a 7-month period of realimentation while differences in carcass composition at II months were eliminated by slaughter at a constant live weight of 622 kg.

Incorporation of food intake into breeding objectives for ruminants is often difficult because the relevant genetic parameters are unavailable. A non-statistical approach to estimating the genetic relationships between food costs and genetic changes in growth and body composition traits was therefore developed.

Equations which predict additional food requirements associated with genetic changes in growth and body composition traits are derived from an interspecies growth model. In the growth model, a genotype is mainly described according to its expected mature weights of protein, lipid and a composition trait of interest in the empty body under non-limiting conditions. Other model parameters describe the expected growth of the animal in a specific environment.

An example is shown for beef cattle in the United Kingdom, where increases in carcass weight by 1 kg and carcass subcutaneous fat proportion by 0·01 result in increases in food costs by £0·97 and £7·34 respectively for a production system where animals are given an intensive silage/concentrate diet, are slaughtered at 305 kg and have a commercial fat grade 4L. A strong dependence of the results on the type of production system, especially the degree of maturity in protein at slaughter, is demonstrated.

The model is easily adapted to other breeds and ruminant species. The approach is recommended for incorporating food intake into breeding objectives for ruminants in situations where reliable estimates of the necessary genetic parameters for a more conventional specification of the breeding objective are unavailable.

In the experiment, four grass (tall fescue hay and Italian rye grass hay, harvested in March and May) and four legume (lucerne hay, harvested in March and May; and red clover hay, harvested in March and April) forages were used. Duplicate samples were incubated in sacco in the rumens of three fistulated mature cows for 2, 4, 8,16, 2i, 48 and 72 h and the degradabilities of dry matter (DM), nitrogen, neutral-detergent fibre (NDF), cellulose and hemicellulose were measured. The maximum degradation rate (MDR) and time of maximum degradation rate (TMDR) were calculated from the first and second derivatives of a Gompertz equation.

The MDR differed between chemical components and was generally higher for cellulose (from 2·31 to 6·95% per h) and nitrogen (from 2·06 to 6·75% per h) in all forages studied. Lignin content of forages was found to be well correlated with the MDR of the fibre components (r = -0·74 for NDF, -0·72 for cellulose and -0·84 for hemicellulose).

The TMDR values were much shorter for DM and nitrogen (< 4·2 h) than for the fibre fractions (from 6·8 to 14·0 h). Furthermore, in grasses, hemicellulose TMDR occurred before those of cellulose, while in legumes the order of TMDR was less clear. Elevated positive correlation coefficients between the fibre components and their TMDR possibly indicate that the structural arrangement and types of linkages within and between these components regulate their fermentation process.

The possibility of using the Gompertz first and second derivatives to study the synchrony of the release of nitrogen and organic matter into the rumen was examined.

Eight change-over design experiments (each a duplicated 3 × 3 Latin square design using six rumen-fistulated wether sheep, live weight 50 to 60 kg) measured rumen fermentation patterns for 24 perennial ryegrass silages. Sheep were offered 800 g dry matter (DM) per day of each silage in two equal meals at 09.00 and 17.00 h. Samples of rumen liquor were taken on days 19 and 21 of each 21-day period, at 08.50 h and at 1·5-h intervals until 16.30 h. Rumen samples were analysed by gas chromatography; silages by high-performance liquid chromatography and by near infra-red reflectance spectroscopy (NIRS) using samples scanned after drying at 100°C (NIRSdry) or in the fresh state (NIRSwet).

Mean intake of DM was 737 g/day. The range of silage composition was as follows (mean, range, s.d., g/kg DM unless specified): metabolizable energy (ME MJ/kg DM) 11·1, 8·8 to 12·6, 0·81; pH 4·0, 3·6 to 5·0, 0·34; lactic acid 86, 4 to 139, 42·6; butyric acid 4·7, 0·1 to 46·7,10·2. Rumen measurements varied substantially both diurnally and between silages. Mean diurnal rumen values for the 24 silages (mean, range, s.d.) were: pH 6·76, 6·55 to 7·09, 0·155; ammonia (mg/l) 132, 70 to 247, 47·7; total volatile fatty acids (TVFA mmol/l) 58·2, 45·8 to 72·0, 8·97; (acetate+butyrate)/propionate (ABP) 3·2, 2·2 to 4·8, 0·56.

Partial least-square models were developed to predict rumen fermentation (means for six sampling times) using either the silage chemical composition (CHEM g/kg DM unless specified: DM, ME (MJ/kg DM), crude protein (CP), ammonia (NH3, g N per kg total N), neutralizingvalue (meq per kg DM), sugar, lactic, formic, acetic, propionic and butyric acids and ethanol) or silage NIRSdry or NIRSwet. Prediction performance was assessed comparing values for R2, standard error of cross validation (SECV) and SD/SECV (s.d. of reference population! SECV) obtained by the ‘leave one out’ cross validation method. NIRSwet gave slightly better prediction accuracy overall than NIRSdry but both were superior to prediction from chemical composition. Values for R2, SECV and SD/SECV for pH were 0·23, 0·14, 1·09; 0·76, 0·08, 2·01 and 0·72, 0·08, 1·89 for CHEM, NIRSdry and NIRSwet respectively. Corresponding values for rumen ammonia (mg/l) were 0·48, 35·2, 1·35; 0·69, 27·1, 1·76 and 0·70, 26·3, 1·81; for TVFA 0·52, 6·73, 1·33; 0·80, 4·06, 2·21 and 0·93, 2·47, 3·63; for rumen ABP ratio 0·69, 0·32, 1·78; 0·76, 0·30,1·88; 0·72, 0·30,1·85. The silage predictors with greatest influence in the CHEM model for rumen ABP ratio were sugar, CP and lactic acid (negative) and butyrate and ethanol (positive). NIRS shows considerable promise as a means of predicting rumen fermentation of animals given grass silage diets.

This study investigated the effects of weaning and sex on various aspects of production and quality characteristics in 22 male and 18 female lambs of the Rasa Aragonesa local meat breed. Half the lambs were weaned (W) at 38 to 40 days and half were left unwearied (UW). Both groups were given ad libitum concentrates and cereal straw. Average farm weight was 22·1 kg at 78·3 days. Live-weight gain was significantly different between sexes but not between W and UW lambs. Dressing proportion was higher in UW lambs. Significant differences in fatness were found between W and UW lambs and between sex of lambs. Among the meat quality traits, W lambs had redder and UW lambs paler meat judged by colour a* and haem pigment concentration. No statistical differences were found in the other traits except flavour intensity, which was higher in UW (66·8) than in W (63·6) lambs on a 1 to 100 scale. All other eating quality aspects, in grilled m. longissimus lumborum slices, tended to be higher in UW lambs. The fatty acid composition of subcutaneous and intramuscular fat depots differed significantly (intramuscular fat was more unsaturated and polyunsaturated). There were also differences between W and UW lambs in subcutaneous fat (higher unsaturated in W lambs). However in intramuscular fat composition only differences in polyunsaturated fatty acids (higher in UW lambs), but not in total unsaturated or saturated, were observed. Tatty acids of less than C16 chain length were higher, in both fat depots, in UW lambs than in W lambs reflecting greater incorporation of milk fatty acids. Palatability characteristics were not closely associated with fatty acid composition except that flavour intensity was correlated with total saturated fatty acids.

The potential of diets, based on maize silage (M), non-bird-resistant grain sorghum silage (NBRGS), bird-resistant grain sorghum silage (BRGS) and forage sorghum silage (FS), in different proportions with concentrate for each silage, was evaluated for the finishing of weaner lambs. On a dry basis the ratios of silage: concentrate were 70: 30, 60:40, 50:50, 40: 60 and 30: 70 respectively for each of the silages. The concentrate mixtures were composed of different quantities of maize meal and soya-bean oilcake meal in order to balance the crude protein contents of the different diets used from weaning to 35 kg live weight and from 35 kg live weight to slaughter at 140 and 110 g/kg respectively.

Better apparent digestibilities of dry matter, crude protein and acid-detergent fibre as well as food conversion to live weight were found for diets with M or NBRGS as roughage sources compared with those with BRGS and FS as roughage sources. At the lower levels of concentrate inclusion in the diets the dressing proportions, carcass grades and food conversion to carcass weight for the diets with M and NBRGS as roughage sources were also better than were those with BRGS and FS as roughage sources. Although higher levels of concentrate inclusion in the diets to a large extent rectified these biological disadvantages of the diets based on BRGS and FS, they will also cause a rise in the price of the diet.

Concern for the welfare of export lambs during long-distance road transport has prompted much research and a recommended change in procedure. The latter envisages an absolute maximum journey time of 31 h and includes a rest-stop (minimum duration 1 h) for feeding and watering. In the present experiment, the physiological and behavioural responses to this new protocol have been investigated in fleeced and shorn lambs (no. = 10 per group) provided with venous catheters and heart rate monitors. The two groups were loaded on a vehicle into separate adjacent pens and driven for 14 h; then unloaded into a lairage, where their behaviour was recorded. After 1 h they were reloaded and driven for a further 15·5 h, finally arriving at a slaughterhouse where carcass condition was evaluated. Blood samples collected at 30- or 60-min intervals by experimenters travelling with the animals were analysed to determine haematocrit, plasma osmolality, plasma concentrations of glucose, creatinine phosphokinase (CPK), and the stress-responsive hormones, cortisol, prolactin, adrenaline and noradrenaline. The results showed that haematocrit increased after loading although the general trend during transport, as with osmolality, was a decline (P < 0·05). No significant changes in plasma glucose were detected but CPK increased in fleeced lambs after loading (P < 0·05). Cortisol release was stimulated by loading, especially in fleeced sheep (P < 0·001) but returned to home pen values within 6 h; heart rates changed in a similar manner. Transport did not markedly affect prolactin release although concentrations were consistently greater in fleeced sheep (P < 0·001). Noradrenaline, however, tended to be higher in shorn animals (P < 0·05). In lairage, both groups readily consumed hay, and especially concentrates, but the shorn lambs spent more time eating (P < 0·001). None of the shorn sheep, and only a few fleeced animals, drank water. There was no evidence for differences in weight loss between the two groups during the experiment and carcass quality at slaughter was within the normal expected range. The implications of these, and other related studies, for future transport policy are discussed, with particular reference to rest-stop duration and handling procedures.

An initial experiment was conducted to investigate the variability of selected metabolites in the plasma from guanacos. A second experiment directly compared plasma biochemical values for guanacos with those for sheep. During the first experiment, jugular blood samples were collected from five mature castrated guanacos using an embedded experimental design. Weekly blood samples were collected at the same time (09.00 h) on the same day each week for 7 weeks. Daily blood samples were collected at the same time each day (09.00 h) during week 5. On day 2 of week 5, blood samples were collected every 3 h from 09.00 h for a 24-h period. No evidence of a cyclical pattern of plasma parameters was observed on a weekly, daily or 3-h basis. During the second experiment, the metabolic profiles of 11 mature castrated guanacos and 11 mature barren ewes (Merino × Welsh Mountain) were compared. Significant differences in plasma concentrations of all metabolites except urea-nitrogen (guanacos -15·42 mmolll, sheep - 15·60 (s.e.d. 1·506) mmolll) were found with values for guanacos v. sheep as follows: glucose (7·63 v. 3·63 (s.e.d. 0·268) mmolll); acetate (0·26 v. 0·48 (s.e.d. 0·035) mmol/l); β hydroxybutyrate (0·06 v. 0·50 (s.e.d. 0·019) mmol/l); albumin (33·4 v. 29·5 (s.e.d. 0·93) g/l); and total protein (53·8 v. 65·6 (s.e.d. 2·12) g/l); (P < 0·001 for all previous variables); non-esterified fatty acids (0·48 v. 0·29 (s.e.d. 0·048) meq per 1; P < 0·01) and a-amino N (2·44 v. 2·66 (s.e.d. 0·088) mmolll; P < 0·05). This study indicates that the reference plasma metabolite concentrations of sheep are not suitable alternatives for use for nutritional or veterinary purposes with guanacos, but those of llamas or alpacas are. The results also suggest that energy capture and transport in camelids may be markedly different from that in conventional ruminants.