Over a 3-year period, productivity characteristics and criteria of trypanosomiasis incidence and severity have been monitored by monthly examination of individual N'Dama cattle in villages in The Gambia. From this database, 60 lactating cows in which Trypanosoma congolense or T. vivax had been detected on blood examination (group 1) were compared with 50 cows which had not been found infected with trypanosomes during the monitoring period (group 2). The latter were selected on the basis of comparability of age and stage of lactation to those of group 1 for examining the effect of trypanosome infections on the quantity of milk extracted for human consumption, and on the growth of their sucking calves. Data from a 6- to 7-month period were examined in the analysis.

The quantity of daily milk extracted during the 1st month ot intection (group 1) decreased by proportionately 0·25 in comparison to the amount extracted during the preceding month when parasites were not detected. The corresponding figure in the uninfected controls (group 2) was 0·02. The mean daily milk extracted for human consumption from uninfected cows during a 6-month period was proportionately 0·26 higher than the mean for the infected cows. Growth rates of calves sucking infected and uninfected dams were similar.

These observations indicate that infection with pathogenic trypanosomes of lactating N'Dama cattle causes a reduction in milk production.

In economic terms, it was estimated that the decline in milk extracted for human consumption due to trypanosome infections amounted to an average of £1 per month per cow.

Twenty-four lactating British Friesian type cows were used in a four period, partially balanced, changeover design experiment to evaluate eight treatments consisting of four protein sources in the supplement (soya-bean meal, formaldehyde treated soya-bean meal, fish meal and a mixture supplying equal crude protein levels from fish and soya-bean meal (respective degradabilities of total supplement nitrogen (N) were 0·56, 0·37, 0·32 and 0·44), each offered in supplements formulated to contain 150 and 200 g crude protein per kg fresh weight in a 4 × 2 factorial design. All supplements were offered at 8·0 kg/day in addition to ad libitum access to a medium digestibility grass silage (digestible organic matter as proportion of dry matter (DM), 0·66); with a relatively poor quality fermentation (pH, 4·5; ammonia-N proportion of total N, 0·21).

There were no significant interactions between source and level of protein on any of the animal performance variables. Source of protein did not influence milk output or milk composition but increasing protein intake significantly increased milk yield (26·0 and 26·7 (s.e. 0·19) for the low and high protein supplements respectively). Blood urea levels were significantly influenced by both protein source and level.

Total diet digestibility and energy and N utilization studies were undertaken with six replicates per treatment and the full data are presented. Neither protein source nor level had any significant effect on DM or energy digestibility. N digestibility was significantly reduced following formaldehyde treatment of soya-bean meal (0·69 v. 0·72 (s.e. 0·01)) and most N utilization variables were influenced by the level of protein intake but not by protein source.

Crude protein concentration in diets based on high-moisture maize grain was increased using rumen degradable protein (RDP) or rumen undegradable protein (UDP). Treatment diets (numbers in parentheses indicate approximate RDP and UDP concentrations, g/kg dry matter (DM)) were: low-RDP (59, 80), high-RDP (79, 92), low-UDP (66, 67), high-UDP (69, 107, with maize gluten meal as chief UDP source) and high-UDP (71, 91, with fish, meat and maize gluten meals as UDP sources). Rumen pH and concentrations of volatile fatty acids, measured hourly for 12 h after feeding in four rumen fistulated Holstein steers, were unaffected by treatment (P > 0·05). Rumen ammonia-N concentration was greater for high-RDP (193 mg/1) than low-RDP (68 mg/1; P < 0·001). Within 12 h of feeding, ammonia-N concentration declined from 169 to 58 mg/1 for low-RDP and remained stable for high-RDP.

In a 56-day feeding trial using Holstein heifers (live weight 128 kg) and the first four treatments, RDP concentration had no effect on DM intake (P > 0·05). Lower DM intake (P < 0·01) for high-UDP (4·40 kg/day) than low-UDP (5·13 kg/day) was attributed to low palatability of maize gluten meal. Live-weight gain and food conversion efficiency were unaffected by treatment.

In a 56-day feeding trial using Holstein bulls (live weight 110 kg) and all treatments, RDP concentration had no effect on animal performance (P > 0·05). Food conversion efficiency increased (P < 0·001) when UDP concentration was increased only if UDP was supplied by a mix of fish, meat and maize gluten meals.

When RDP supply was not limiting to DM intake, protein source (amino acid composition) was better than protein degradability as an index of the feeding value of dietary protein.

Two groups of six bulls were offered a fattening diet based on barley or sugar-beet pulp in the proportions of either 500: 200 g/kg or 200: 500 g/kg to compare the effects of starch and degradable fibre on rumen fermentations, plasma hormones and metabolites. The bulls were fed twice daily at 08.00 and 16.00 h.

The large proportion of sugar-beet pulp in the diet induced higher levels of acetic and butyric acids and less propionic acid than the high proportion of barley. The diurnal patterns over a 24-h period of rumen pH, volatile fatty acids, glucose and ammonia were characterized by two cycles. Sugar-beet pulp in large proportions induced more even fermentations as indicated by flatter curves with less extreme values than those produced by a large inclusion of barley in the diet. Ammonia concentration was high before feeding and decreased subsequently during 4 to 6 h after the meal.

No typical patterns were observed in plasma concentrations of glucose and alpha-amino nitrogen. Plasma urea concentration rose 2h after feeding and dropped during the following 6 to 8 h. There were no effects of dietary carbohydrate composition on growth hormone concentration but plasma insulin was significantly reduced with the diet high in sugar-beet pulp. Furthermore, the insulin profile showed peaks after each meal with the barley diet but only after the afternoon feeding with the diet high in sugar-beet pulp.

Correlated responses to selection in a tropical beef herd for high (H) and low (L) estimated breeding value for pregnancy rate were measured over three calf crops. The H line calves were proportionately 0·04 lighter at weaning but during the ensuing dry season they lost less weight than L line animals, so that between the ages of 12 and 18 months there were no significant line differences in live weight. It was concluded that selection for cow fertility had not directly altered the progeny's growth rate. Tick resistance and heat tolerance also did not differ between the lines. However, resistance to worms was lower (P < 0·05) in the H line indicating genetic antagonism between cow fertility and worm resistance. Scrotal circumference and scrotal circumference adjusted for live weight were significantly higher in H line bulls between 9 and 18 months of age. Pregnancy rates of heifers in the H line were 0·12 higher than in the L line despite similar average live weights at mating. It is suggested that accelerated sexual maturity in both heifers and bulls has occurred as a result of selection for lifelong cow fertility.

Data on individually recorded silage dry-matter intake (SDMI), concentrate dry-matter intake (CDMI) and live weight of steers and data on silage composition including toluene dry matter (TDM), pH, total nitrogen (N), ammonia nitrogen (NH3-N), volatile fatty acids (VFAs), digestible organic matter in the dry matter (DOMD) and neutral-detergent fibre (NDF) obtained from experiments conducted at three sites were used to obtain simple and multiple linear regressions of SDMI on other variables.

Live weight accounted for a high proportion of the variation in intake but this effect could generally be removed by scaling intake by live weight raised to the power of 0·75 (M0·75). CDMI was the most important factor affecting scaled intake in mixed diets. TDM, NH,-N and VFAs all had important effects on SDMI. The relationship of SDMI with TDM was curvilinear suggesting that there is little to be gained in intake terms from wilting to TDM above 250 g/kg. The effect of NH3-N appeared to be related more to its correlation with VFAs than with any other nitrogenous constituent while the VFAs appeared to have a direct effect on SDMI. The effects of N and pH on SDMI were generally small. DOMD and NDF had relatively little effect on SDMI. Significant differences in intercepts between sites were found for most relationships although common slopes were often found.

Data on individually recorded silage intake (SDMI), concentrate intake and live weight of steers and data on silage composition including toluene dry matter, pH, total nitrogen, ammonia nitrogen, volatile fatty acids, digestibility and fibre measures obtained from experiments at three sites were used.

Correlation and principal component analyses indicated that there was severe collinearity among a number of the variables, particularly among various fermentation characteristics, between different measures of digestibility and between different measures of fibre. This collinearity was shown to have caused instability in least-squares multiple regression coefficients of silage intake on other variables previously obtained from the same data (Rook and Gill, 1990). Principal component regression and ridge regression allowed the derivation of new coefficients which were more stable and more in line with a priori expectations from experimental results. Linear functions of the original variables and the use of models containing fewer variables also proved effective in overcoming the problems of collinearity.

Fermentation characteristics were shown to be the most important silage factors affecting intake and butyric acid was shown to be more important than other volatile fatty acids or ammonia nitrogen. Neutral-detergent fibre was found to be better related to intake than other fibre or digestibility measures.

The precision of a number of new models for predicting silage intake by beef cattle was investigated with independent data using the mean-square prediction error and compared with two previously published models (Agricultural Research Council, 1980; Lewis, 1981). The new models generally performed well relative to the previous models.

The new models included a number constructed using the technique of ridge regression which were shown to be consistently better predictors than the models obtained from the same estimation data by stepwise least-squares regression. Better prediction was also obtained by reducing the number of variables in the least-squares models below that required to maximize R2 in the estimation data. The poor performance of the least-squares models with the best R2 may be attributed to collinearity between the independent variates in the estimation data.

Most of the models considered overpredicted relative to observed intakes. This may have been the result of differences in breed type and management of the animals between the test data and the estimation data used to construct the models, that is the use of the models with the test data involved a degree of extrapolation.

It is concluded that ridge regression and deletion of variables offer a positive step forward in intake prediction compared with models based on maximizing R2 in the estimation data. However, further work is needed to clarify the effect of factors such as breed and rearing system on intake and to clarify the usefulness of various fibre measures in intake prediction. A number of new models are proposed which utilize a range of input variables thus allowing flexibility in their use in practical situations.

Digestibility (DE) and metabolizability (ME) of a single pelleted diet was examined with growing Angus and Holstein cattle. One hundred and ninety-one individual digestion trials were conducted with bulls, steers and heifers. Food was offered ad libitum or restricted with a daily meal frequency of four. Data were analysed by two covariate models. The first included relative dry matter intake (RDMI) defined as the ratio of DMI to body weight (M0·73). In the second model, covariates were defined by genetic-size scaling; the first covariate scaled DMI by mature weight (A) raised to the power 0·73 (DMI/A0·73) and the second covariate was degree of maturity (μ) defined as body weight divided by A. Model 2 also allowed separation of size and DMI effects. No breed differences were detected. There was a consistent trend for increasing ME and ME/DE from heifers to steers to bulls which was significant between heifers and the average of bulls and steers (575·3 v. 589·3 and 832·8 v. 844·3 J/kJ for ME and ME/DE, respectively). Independent of animal effects, DE, ME and urinary energy (UE) decreased and ME/DE and faecal energy (FE) losses increased as RDMI or DMI/A0·73 increased. Per unit rise in RDMI equivalent to maintenance, the corresponding changes for DE, ME, ME/DE, FE and UE were –33·9, –13·6, 21·3, 34·1 and 9·6 J/kJ, respectively. DE increased 1·5 and ME increased 0·8 J/kJ GE for each 01 unit increase in degree of maturity.

One hundred and twenty-seven groups of cattle were studied in a slaughterhouse lairage to determine the factors affecting their ability to rest. The cattle were studied by direct observation over one 30-min period during their first 3·5 h in the lairage. An ethogram/time budget analysis of one focal Hereford × Friesian steer or heifer per group was undertaken and the lying behaviour of the whole group was recorded. Linear regression analysis was used to examine the effect of length of time in the lairage on behaviour. The effects of source, sex, group size, space allowance and bedding were examined by a comparison of regression lines. In cattle from markets, standing and moving behaviour, and the number of aggressive interactions decreased and lying behaviour increased with time in the lairage. This was not the case in cattle coming direct from farms. In cattle from markets, steers settled down at a faster rate than heifers, and cattle kept in group sizes >5 settled down at a faster rate than those kept in group sizes ≤5. The presence of straw bedding was associated with greater lying behaviour in market heifers and in market cattle kept in group sizes ≤5 than in similar cattle without straw bedding. Cattle from markets but not those from farms started to settle down within 3·5 h of arrival in the lairage and their behaviour was affected by the social and physical environment.

Six mature sheep, each fitted with a rumen cannula, were assigned to six diets in a 6 × 6 Latin-square design experiment to examine the effects of a yeast culture on ruminal metabolism, rumen liquid outflow rate, fibre digestion in the rumen and overall nutrient digestibility. The yeast culture (YC) was a commercial product composed of a yeast (Saccharomyces cerevisae) and the media on which it grew and dried so as to maintain its fermentative capacity. The six dietary treatments were three diets differing in hay dry matter (DM): concentrate DM ratio (90: 10, 65: 35 and 40: 60 designated low, medium and high concentrate respectively) each given either without or with a supplement of 4 g/day of YC. Treatment periods were of 3 weeks duration. There were significant effects of dietary forage: concentrate ratio on rumen function (P < 0·05). Rumen pH, rumen liquid outflow rate, rumen ammonia concentration, total volatile fatty acids concentration, and molar proportions of acetate, propionate and butyrate were not significantly affected by the inclusion of YC (P < 0·05). Supplemental YC did not affect the overall nutrient digestibility of organic matter, neutral-detergent fibre or gross energy measured in vivo. However, at every forage:concentrate ratio, YC increased the disappearance of hay organic matter from nylon bags incubated in the rumen for 24 h (P < 0·05). The values with and without YC were 0·482 and 0·432 for the low, 0·423 and 0·366 for the medium, and 0·360 and 0·321 for the high concentrate diets respectively. However, YC had no effect on hay disappearance when bags were incubated for 48 h. YC appeared to increase the initial rate of forage digestion in the rumen without altering overall food digestibility or the patern of production of fermentation end products.

The body dimensions and live weight of 126 Mule (Bluefaced Leicester × Scottish Blackface) and Scottish Blackface ewes were measured during the 1986/87 housing season. Body dimensions included: head and neck length, body length, diagonal body length, height to withers, height to rump, girth at widest point, heart girth, width at widest point and width at shoulders. It was found that most body dimensions varied greatly with body weight. However, some body dimensions such as head length were found to be independent of weight within the weight range studied. Prediction equations are presented for each body dimensions for unshorn sheep.

These predictions can be used as a basis for the design of sheep housing, for example, trough space allowances, design of feeders or as a biological basis for space allowance.

Eighteen lambs (L) and 18 goats (G), 12 weeks of age, were allocated in equal numbers to three diets. The basal (B) diet had no added copper (Cu) while the other two had 30 or 60 mg added Cu per kg dry matter (DM) as CuSO4.5H2O. Lambs and goats were housed and fed individually. After 67 days, deaths from Cu toxicity occurred only in lambs from groups L-30 (basal diet + 30 mg Cu per kg DM) and L-60 (basal diet + 60 mg Cu per kg DM). The remaining lambs and all of the goats were slaughtered at 91 and 137 days respectively.

A decreased food intake and loss of weight were observed in some lambs towards the end of the experiment which appeared to be associated with an approaching haemolytic crisis. The additional dietary Cu had a positive effect on food conversion efficiency only in the early stages of the experiment in both lambs and goats. None of the goats died or lost weight.

Plasma Cu concentrations and serum glutamate oxalacetate transaminase and creatine kinase activities were elevated in lambs of groups L-30 and L-60 after 2 months, while in goats the concentrations were in normal ranges during the whole experimental period.

Additional dietary Cu increased significantly the Cu concentrations of liver, kidney, muscle, spleen, heart, brain, hair and faeces in both lambs and goats. Additional Cu decreased the fresh and dry liver weights of lambs and the liver to live weight ratio whereas the corresponding values for kidneys were increased. The differences between groups of goats in fresh or dry liver and kidney weights were not significant, though the fresh and dry liver weights tended to be higher in groups G·30 and G·60 compared with those in the group G·B.

The amount of Cu stored in the livers of the lambs was six to nine times higher than that of the goats. Differences in Cu storage between lambs and goats may be related to species differences in Cuutilization and hence resistance to Cu toxicity.

Work in the United States of America has shown that dietary supplements of nickel (Ni) can result in an increase in rumen urease activity and can increase growth rate and food conversion efficiency in lambs and steers given low protein diets. It has been suggested that Ni enhances urea recycling through its effect on urease activity. To examine this hypothesis, four sheep were given a high-energy, lowprotein diet with or without a supplement of 5 mg/day Ni, given as NiCl2.6H2O by continuous infusion into the rumen. Urea irreversible loss rate (ILR) and pool size were measured by means of a single intravenous injection of 14C-urea. The addition of Ni resulted in a significant increase in rumen urease activity (P < 0·05) but there was no significant effect on urea ILR, urea pool size, urinary urea excretion or on the quantity of urea recycled to the gastro-intestinal tract. Ni also had no effect on plasma urea or rumen ammonia concentrations, on diet digestibility or on nitrogen retention. It is concluded that the enhancement of urease activity by supplementary Ni conferred no nutritional advantage to the sheep.

Two fats, soya-bean oil and tallow, were blended in the ratios 70: 30, 50: 50 and 30: 70. The ratios of unsaturated to saturated fatty acids (U/S) of the blends were 3·18, 2·08 and 1·49 respectively; values for soya-bean oil and tallow were 6·69 and 0·93. These five fat sources were each included into a basal diet at levels of 40, 80 and 120 g/kg. The digestible (DE) and metabolizable (ME) energy together with the apparent fat digestibility (AFD) of the experimental diets were measured in a metabolism trial based upon four 4 × 4 Latin squares using 16 gilts of 30 kg initial live weight. Linear equations relating dietary DE and ME values to level of inclusion of fat were extrapolated to 1000 g/kg to obtain values for the fats. DE values for soya-bean oil and tallow were 38·06 and 34·16 MJ/kg respectively. Corresponding data for ME were 35·63 and 32·53 respectively. These figures were used to calculate values of the mixtures. Data thus derived did not differ significantly from those determined directly, indicating that there was no synergism between the two fats. DE values of fats determined as the product of AFD of fats and their gross energy followed similar trends. The majority of the increase in values of fats was associated with a change in the U/S ratio from 0·93 to 2·08.

In a consumer trial the assessments of 874 cooks and 5034 family members were analysed. Forty-one boar and 40 barrow carcasses were selected in a commercial abattoir so that the two sexes were similar in carcass weight, fat thickness and muscle pH. A boar sample including a higher proportion of tainted carcasses was selected. It was divided into three boar taint-level subgroups according to their 5a-androst- 16-ene-3-one (androstenone) concentration in fat (Jig androstenone per g fat) as follows: L < 0·5 (no. = 17), M 0·5 to 1·0 (no. = 13) and H > 1·0 (no. = 11). From each carcass, loin/rib chops were prepared and cooked hams, brine-cured bellies and Spanish dry-cured hams were processed. An analysis of variance was used to estimate the effects of sex and boar taint levels. Cooks (P < 0·05) and family members (P < 0·01) reported a higher level of odour for boar chops. A higher level of unfavourable responses to odour and flavour were found in the H taint-level subgroup. Also, the H taint-level group produced the highest proportion of negative judgements on overall acceptability in comparison with normal purchases. The response of cooks to odour from brine-cured bellies was significantly affected by sex (boar and barrow). For bellies, odour, overall acceptability and comparison with normal purchases were significantly affected by the boar taint-level subgroups (P < 005). The treatments had no significant effect on any quality question related to boar taint in cooked ham. However, boar taint level significantly affected the assessments of flavour and overall acceptability from Spanish dry-cured ham (P < 0·01). A higher proportion of negative responses was found in the H taint-level subgroup. The trial indicates that boar meat can produce an unfavourable response from consumers for fresh meat (chops) or products needing heating prior to consumption (brine-cured bellies). However, in cooked products with hot processing and cold consumption (cooked ham) no negative effect from using boar meat was observed. To produce Spanish dry-cured ham, androstenone quantification should be carried out to avoid consumer dissatisfaction.

Experiments involving both digestion and growth trials were undertaken to compare the responses of pigs to two increments of digested energy resulting either from gut fermentation or from digestion by endogenous enzymes in the small intestine. Unmolassed sugar-beet pulp (SBP) and maize starch (MS) were selected as model materials for these two systems. A control diet was formulated to fulfil the needs of pigs for all essential nutrients apart from energy. This diet was offered according to a scale set at about twice the maintenance energy requirement. The two SBP diets contained 150 and 300 g SBP per kg (SBP15 and SBP30) and the two MS diets 100 and 200 g MS per kg (MS10 and MS20). Sixty observations were made with 10 female and 20 male growing pigs to provide information on digestion. The results showed that the energy in SBP and MS had an apparent digestibility of 0·74 and 0·98 respectively (s.e.d. 0025). The neutral-detergent fibre fraction of SBP had a digestibility of 0·81 (s.e. 0·055). Forty pigs (20 male and 20 female) were involved in the growth trial. The responses of pigs to increments of different digestible energy (DE) were measured in terms of daily carcass-weight gain. The results gave values of 435, 478, 527, 511 and 567 (s.e.d. 17·3) g/day for the control, SBP15, SBP30, MS 10 and MS20 treatments respectively. These results suggest that the apparent DE of SBP is used for carcass growth with an efficiency of 0·57 (s.e. 0·012) relative to the DE from MS.

Rapeseed, sunflower and soya-bean meals were compared as the main sources of protein in concentrate supplements given to dairy cattle. The supplements contained (per kg) 620 g rapeseed meal, 760 g sunflower meal or 500 g soya-bean meal and all three were formulated to contain 300 g protein per kg. Each animal was given daily TO kg dairy compound, 3·5 kg supplement, 3·5 kg sugar-beet pulp pellets and offered maize silage ad libitum. A randomized-block design with 39 cattle was used and treatments were applied for 16 weeks. All three supplements were eaten rapidly and there were no refusals. Daily mean milk yields were rapeseed 26·7, sunflower 25·3 and soya bean 25·1 (s.e.d. 1·44) kg; milk fat and protein concentrations were not affected by the treatments. There were no significant treatment differences in live weight and condition score. It was concluded that these high protein supplements based on rapeseed meal, sunflower meal and soya-bean meal were of equal feeding value for milk production.