A feeding system, draught cows, disease/work interactions and animal power introduction in a farming system, four areas of recent research on draught ruminants which are important to future development of animal power, are reviewed. A new feeding system for draught animals is described which enables food requirements and the effects of work on live weight and milk production to be calculated.

Recent data on the energy cost of walking are appraised. Research on working cows, mainly in Ethiopia, has shown that undernutrition has a greater effect on milk yield than work, which has a transient effect. The length of the post-partum anoestrous period increases with decrease in body condition. Body-weight loss increases with increasing work load. It is suggested that dairy cows delay conception by 1 day for every day of work done. Work has little effect on food intake or digestive parameters. Although it is associated with an overall increase in food intake of cows, even of un-supplemented forage diets, the increase is not sufficient to meet all the extra energy needs for work. Food intake of both working and non-working cows increases during lactation.

Disease limits the working capacity of draught animals and work can exacerbate disease. These effects were investigated using Trypanosoma evansi in Indonesia and T. congolense in The Gambia. In both studies, infected animals were able to do much less work than non-infected ones and the severity of the effect depended greatly on the strain of trypanosome used. In general, increasing the plane of nutrition did not ameliorate the effects of the disease, nor in the Gambian study did it prevent loss of appetite in infected animals.

The technical and agronomic innovations necessary for the introduction of animal power into an inland valley region of central Nigeria are described and some of the sociological implications discussed.

In a previous experiment the provision of straw to group-housed pigs increased the number of daily feeder visits. This effect of straw is comparable with conditions of reduced social competition for access to the feeder. The aim of this experiment was to investigate if changing straw provision within a pen resulted in similar and reversible effects in this behaviour. One hundred and twenty male pigs (41·1 (s.e. 0·43) kg) were used in three blocks each of four pens of 10 pigs. In each block of 42 days duration one pen had no straw throughout (treatment 1); one pen had no straw for 21 days (period 1) followed by straw for 21 days (period 2) (2); one pen had straw followed by no straw (3) and one pen had straw throughout (4). The pens were situated in a naturally ventilated building with light from 06.00 to 20.00 h. Each pen had a kennel, a lying area and a single-space computerized feeder for recording feeding behaviour. The pigs’ activity was recorded on video in the 2nd and 5th weeks of each block. The number of feeder visits was slightly higher for pigs with straw (1: 9·69 v. 4: 10·46) but this was not significant (P > 0·05). The effect was more marked for treatment 2 where the visits increased (P < 0·01) from period 1 (8·52) to period 2 (10·64) and for treatment 3 where they decreased (11·20 v. 10·10). Pigs without straw (treatment 1) spent more time in the kennel than those with straw (treatment 4) (P < 0·05). For treatment 2 the proportion of time spent in the kennel fell from 0·607 in period 1 to 0·288 in period 2 (P < 0·01). There was a general trend for more activity and more lying outside the kennel when straw was provided. The effect of straw provision was not as marked as that seen previously; nevertheless changing straw provision (treatments 2 and 3) did result in an increase in feeder visits with straw, probably related to the increase in general activity and lying outside in the area adjacent to the feeder.

The influence of environmental stimuli considered biologically relevant for nest building sows, on nursing and suckling behaviour and piglet growth was investigated. Effects of floor type (beach sand v. concrete) and substrate type (straw feeder v. no straw feeder) were examined in a 2 × 2 factorial experiment with nine replicates of four multiparous sows. The sows were kept individually in roofed 7·6 m2 ‘get-aw ay-pens’ from 1 week pre-partum until 13 to 15 days post-partum. The behaviour of sows and piglets were video recorded for 24 h on days 0, 3, 6 and 12 post-partum.

The latency from termination of farrowing until perceptible milk ejection tended to be shorter for experienced sows (parity 4 to 5) kept on sand than on concrete floors (1207 (s.e. 109) min; no. = 7 v. 1725 (s.e. 123) min; no. = 6, respectively; F2,8 = 3·93, P < 0·07) and for experienced sows with access to a straw feeder than without access to a straw feeder (1257 (s.e. 113) min; no. = 8 v. 1666 (s.e. 132) min; no. = 5, respectively; F2,8 = 3·56, P < 0·08). On days 3 and 6 a longer duration of suckling was found for sows on sand v. concrete floors (384 (s.e. 20) v. 327 (s.e. 16) s on day 3; F1,19 = 5·6, P < 0.03 and 377 (s.e. 14) v. 318 (s.e. 13) on day 6; F1,21 = 9·09; P < 0·01, respectively) and with straw feeder v. without straw feeder (385 (s.e. 20) v. 326 (s.e. 18) s on day 3; F1,19 = 5·11, P < 0.04 and 372 (s.e. 14) v. 323 (s.e. 13) on day 6; F1,21 = 6·21; P < 0·03, respectively). On day 3, a tendency for a sand × straw feeder interaction (F11,8 = 3·58, P < 0.08), showed that sows without environmental stimuli terminated more sucklings than sows with access to a straw feeder and sows kept on sand (32 (s.e. 7) %, 16 (s.e. 4) % and 13 (s.e. 5) %, respectively). Similarly, on day 6 a significant sand × straw feeder interaction (F316 = 7·15, P < 0·01) led to increased frequency of foreleg rowing for sows without environmental stimuli compared with the three other treatments (14 (s.e. 2) v. 7 (s.e. 1), 5 (s.e. 1) and 6 (s.e. 1) foreleg rowings per h, respectively). During the stay in the experimental pens, the growth rate of piglets kept on sand tended to be higher than for piglets kept on concrete floors (261 (s.e. 33) v. 240 (s.e. 30) g per piglet per day; F1,25 = 3·38; P < 0·08).

The results of the present experiment indicate that provision of biologically relevant stimuli affect the nursing and suckling behaviour of sows and piglets. The reduced termination of sucklings, the reduced frequency of foreleg rowing, the increased duration of suckling as well as the earlier development of suckling behaviour might have been advantageous for the early milk intake of the piglets.

Performance of 80 (tests 1 and 2) or 60 (tests 3 and 4) weaned pigs were compared when using ‘Tubetype’ feeder (T), allowing the animals to mix meal and drinking water, or another type (V) where drinking and eating places are separated. The difference in growth rate was not significant but the mean daily water consumption (1 per pig per day) was higher with T than with V in each test but significantly only in tests 1 and 3 (1·84 v. 1·40, and 2·11 v. 1·26, P < 0·01).

Feeding behaviour was assessed during tests 2 and 4. Multifactor analysis of variance revealed effects (P < 0·01) of feeder, group size and period of the day on the occupation time and the average number of animals using the feeders simultaneously. These two variables were higher for V than for T (test 2: 23·4 per 24 h v. 21·5 per 24 h and 4·5 v. 3·7, P < 0·05; test 4: 20·0 per 24 h v. 18·2 per 24 h, P< 0·01). In each test, both feeders were used for a longer time and by more piglets during the ‘day’ than during the ‘night’ (P < 0·01). When grouping 40 pigs, animals used both feeders during almost all the day period (V: 15·9 per 16 h and T: 15·8 per 16 h). During the night period, this was only true with V (V: 7·4 per 8 h; T: 5·8 per 8 h). The use of feeder V in crowded conditions thus prevented preferential diurnal feeding activity, commonly described in pigs. In conclusion, even if productivity is not affected, feeding behaviour and thus eventually welfare are influenced by the type of feeder, especially with high numbers of animals.

The data used in these analyses were compiled from individual feeding records of 1832 pigs from 70 sire families using FIRE (food intake recording equipment) system from Hunday Electronics Ltd at the Cotswold Pig Development Company. Pigs were on test between 45 (s.d. 2·76) kg and 95 (s.d. 6·78) kg. Daily food intake (DFI kg), food intake per visit (FlV kg), number of visits per day (NV), duration of each visit (TV min), time in the feeder per day (TD min), feeding rate (FR kg/min) and number of non-feeding visits per day (NFV), were measured as means of test and DFI was also recorded as means of bi-weekly periods of test. Performance test traits ofbackfat depth off test (BF mm), food conversion ratio (ECR kg/kg) and average daily gain (ADG kg), over the test period, were also measured.

Parameters were estimated by restricted maximum likelihood with a multivariate individual animal model. DFI had a heritability of 0·21 ranging from 0·18 to 0·26 over the four test periods. Correlations between DFI in each test period were high (rg = 0·75 to 0·99). DFI was highly correlated with performance test traits (0·61 to 0·78) but had low correlations with feeding pattern traits (0·0 to 0·24). The heritabilities of feeding pattern traits were low (0·06 to 0·11) with the exception of FIV (0·27) and NV (0·34) but correlations between feeding pattern traits were high. FIV, NV and TV were moderately correlated with ADG (rg = 0·49, -0·29, 0·33 respectively), BF (rg = 0·35, -0·15, 0·17 respectively) and ECR (rg = -0·12, 0·31, -0·27 respectively). Feeding patterns may be changed substantially by selection and the genetic correlations with performance test traits indicate that feeding patterns traits can be usefully incorporated in selection criteria to improve somewhat the accuracy of selection.

A method to establish the economic optimum (minimum) cost of fertility in the dairy herd is described and demonstrated. A Markov chain model is used iteratively to establish the gross margin of the herd in the long term at various levels of oestrous detection rate and under two different rebreeding strategies. These gross margins are required by the optimization methodology. Under the initial assumptions reflecting current commercial practice in the United Kingdom, gross margin was £806 per cow. This figure varied by proportionately 0·15 over the range of oestrous detection rates assumed (0·4 to 0·7) while delaying rebreeding by 20 days caused gross margin to drop by approximately 0·04. It was concluded that it is important to optimize fertility control as well as rebreeding strategy in order to establish the economic impact of fertility in the dairy herd.

The economic value of fertility was also expressed per unit of calving interval and adjusted calving interval (ACI). ACI was calculated by dividing calving interval by the proportion of cows not culled for reproductive failure. Under the assumptions made, the marginal value of calving interval at the optimum oestrous detection rate was £6·22 per day, rising to £7·44 per day if rebreeding was delayed. The corresponding figures for ACI were £1·57 per day and £1·24 per day. The range in marginal values at sub-optimal oestrous detection rates were £4·38 for calving interval and £0·61 for ACI. It was concluded that the lower variation in ACI at different levels of fertility may make it a more representative trait for inclusion in a selection index provided the necessary genetic parameters can be reliably estimated.

The efficiency of marker-assisted introgression programmes, expressed as genetic lag relative to a commercial population under continuous selection, was investigated using analytical methods. A genetic model was assumed for which the genetic variance in the introgression population was a function of the within-breed genetic variance and the initial breed difference. It was found that most of the genetic lag occurs in the latter stages of an introgression programme, when males and females which are heterozygous for the alíele to be introgressed are mated to produce homozygous individuals. Reducing genetic lag through selection on genomie proportion by using genetic markers throughout the genome, i.e. by selecting heterozygous individuals which resemble the recipient (commercial) population most, was effective if the initial breed difference was very large (e.g. 20 within-breed phenotypic standard deviations). In that case, selection solely on genetic markers could be practised to speed up genome recovery of the commercial line. If the initial breed difference is small, phenotypic or best linear unbiased prediction (BLUP) selection is superior in reducing genetic lag under the assumed genetic model.

An evaluation of the effects of the proportion of Texel or Rouge de l’Ouest (Rouge) genes in ewes (0, 0·5 or 1·0; the remainder being Greyface (Border Leicester × Scottish Blackface)) on prolificacy, lamb viability and lamb output was undertaken. A comparison of Texel and Rouge sires was carried out on Greyface, Texel and Rouge ewes. Prolificacy was higher in Greyface compared with Texel ewes (P = 0·06) but was lower in Greyface compared with Rouge ewes (P < 0·001). Prolificacy was similar in Greyface and Texel × Greyface ewes mated to Texel rams and in Greyface and Rouge × Greyface ewes mated to Rouge rams. The level of dystocia was similar in Greyface and Texel × Greyface ewes but significantly higher in Texel ewes (P < 0·001). The proportion of Rouge genes in the ewe had no effect on the level of dystocia. Litter weight of lambs at birth was significantly heavier in Greyface (P < 0·001) and Texel × Greyface (P < 0·01) ewes compared with Texel ewes. The proportion of Rouge genes in the ewe had no significant effect on litter weight. Lamb mortality (no. of lambs born dead and died birth to weaning) was significantly greater with Rouge ewes compared with the other ewe breed types (P < 0·001). The number of lambs which died from birth to weaning was lower with Texel × Greyface compared with Greyface ewes (P < 0·01). Expressed on a unit metabolic weight basis, Greyface ewes produced a significantly greater weight of lamb compared with Texel (P < 0·05) and Rouge ewes (P < 0·001). Texel × Greyface ewes produced a significantly greater weight of Texel-sired lamb compared with Greyface (P < 0·01) and Texel ewes (P < 0·001).

Sire had a significant effect on a number of parameters. The number of productive ewes was significantly lower in ewes mated with Texel sires (P < 0·001). Lamb birth weights and pre-weaning growth rates were greater with Rouge sires (P < 0·05). Number of lambs weaned per ewe lambed was significantly greater with Texel sires (P < 0·01). Overall weight of weaned lamb produced per ewe was not significantly affected by sire breed.

Evidence to support the existence of a maternal lineage variance component for production and food intake traits at the Langhill experimental dairy herd was investigated. Maternal pedigree records of the herd were traced back to the points of cytoplasmic origin using herd book records. Cytoplasmic origin was defined as the earliest maternal ancestor of a cow and used to assign cows to maternal lineages. This was either a grade-up cow or an ancestor traced back to 1920. The tracing resulted in the cows being assigned to 56 maternal lineages, ranging in size from one to 72 cows. A total of 1118 records of 517 cows, all with a first lactation record, were used in the analysis. Traits analysed were daily milk, fat and protein yield, fat %, protein %, food dry-matter intake, net energy of milk production, a measure of milk production efficiency, average condition, and calving condition, all averaged over the first 26 weeks of lactation. The analysis was performed using a residual maximum likelihood animal model with and without a random component for maternal lineage. Possible bias, due to the fact that the sires were a select sample from the population, was also examined. No significant effect was found in the analysis of the full data set that could be assigned to maternal lineage. Fat yield was the only trait to show a variance component approaching a 5% significance level with a magnitude of 4% of phenotypic variance. However, when maternal lineages of at least five cows were considered, a significant 4% maternal lineage component of phenotypic variance was found for fat yield. The power of the analysis to detect a variance component of less than 4% was shown to be poor. No evidence was found for a maternal lineage component of food intake traits or condition score. Treating sire as a fixed effect or regressing data on sire EBV made little difference to the maternal lineage component.

The objective of this research was to design and compare nucleus breeding plans that might be recommended to the breeders of Brazilian dairy cattle. Plans for native dairy breeds were compared for the change of genetic merit in milk yield and in the economic return at 25-year investment periods. Effects of nucleus herd and commercial population sizes on genetic gain and net income were examined. Investment value of plans was studied for differences in the efficiency of embryo transfer techniques and in the sale price of cows and young bulls on genetic merit. Parent selection was based on records on individuals (for females), their full- and half-sibs, their dam, full-and half-sibs of their sire and their dam and their grandam. Within herd sire selection was restricted to a maximum of one bull per full-sib family. No matings of full-sibs were allowed. Annual economic summaries considered the age distribution of animals within herds. Alternative plans were investigated for their revenue, expense and net income streams and their investment value. The cumulative genetic gain of selected animals in lactational milk production was 1639 kg and 1435 kg for large plans with 64 donors (L) and small plans with 32 donors (S), respectively. The initial genetic lift for a population size of 20 000 animals was equal to 279 kg. When the size of the commercial population was increased to 50 000 animals, the lift was increased by 10%. Profitability in the different plans was achieved after the sale of cows and young bulls. The difference between cumulative discounted net returns at year 25 for L and S was proportional to the sale prices placed on the genetic merit of cows and bulls. The programmes of genetic improvement described were profitable and should be recommended to the breeders of Brazilian dairy cattle. Considering the criteria of gain to cost, the smaller plan seems to be the most reasonable to implement.

The influence of genetic and environmental factors on body weight and reproduction and their relationship to milk production traits, were studied in data of about 4700 Sahiwal cows from Pakistan. (Co)variance components were estimated using restricted maximum likelihood (REML) procedure based on the expectation maximization algorithm applying an animal model. Mean weights of females were: at birth, 21·6 kg; at 1 year, 130 kg; and at 2 years, 222 kg. Records of age at calving, cow weight post partum and calving interval were studied in the first three parities, with parities considered as different traits. For primiparous cows the average values of these traits were: 44·1 months, 319 kg and 465 days, respectively. Mean stillbirth rate was 5·3%. Heritabilities ranged for body weight traits from 0·08 to 0·21, for age at calving from 0·10 to 0·13 and for calving interval from 0·03 to 0·07. Genetic correlations of age at first calving with calving interval and 305-day milk yield were low. The genetic correlation between 305-day milk yield and calving interval was positive (unfavourable) in first parity (0·68) but negative in the third (-0·47). Cows with a high genetic value for 305-day milk yield were heavier at first calving than were low-yielding cows (rg 0·57). The genetic change in reproductive traits over the period studied was close to zero, whereas a marked deterioration was found in phenotypic performance. It is concluded that improved feeding and management, along with some selection against poor reproduction in cows, are important for improvement of reproductive performance.

This study quantified individual phenotypic variation in live weight and live-weight changes during the first three lactations and estimated the effects of age, lactation week and pregnancy on live weight. Data comprised weekly averaged live weight (calculated from daily observations) during 452 lactations of 239 Holstein-Friesian cows. Unadjusted mean live weights were 553 (s.d. 50), 611 (s.d. 55) and 654 (s.d. 57) kg during first, second and third parity, respectively. Estimated effect of growth during parity was 46, 52 and 23 kg for the first three parities. Mean maximum weight loss was 26, 22 and 22 kg for first, second and third parity and variation was large among individuals. Week of lactation when cows had their maximum weight loss ranged from 7 weeks in first lactation to 13 weeks in third lactation. Estimated maximum effect of pregnancy on live weight during the lactation varied from 27 to 59 kg. Phenotypic variance in live weight increased with parity. Repeatabilities of live-weight observations within parity were 0.85 . Across parities, high repeatabilities were found for calving weight and mean live weight but not for parameters associated with maximum weight loss. Correlations between weekly means and mean live weight during the whole of lactation were high. It was concluded that single live-weight observations of heifers are a good measurement of mean live weight during the first three panties.

Responses in carcass composition and meat quality after seven generations of selection for components of lean growth rate were examined in a population of Large White pigs. There were four selection groups in the study, with divergent selection for lean growth rate on ad libitum (LGA) or restricted (LGS) feeding regimes, lean food conversion ratio (LFC) and daily food intake (DFI). In generations six and seven, two offspring from each of 10 sires, within each selection line, were to be allocated for half-carcass dissection and measurement of meat quality. There were 320 animals in the study, with 40 animals from each of the high and low selection lines and, within each selection line, two offspring per sire.

Responses in carcass composition were similar in the three selection groups given food ad libitum, but rates of lean and fat growth rate differed between selection lines. Intramuscular fat content was reduced with selection for high LGA and high LFC but was increased with selection for low DFI (-1·7 and -3·2 v. 2·7 (s.e.d. 0·7) mg/g), which was unexpected given the higher carcass fat content of the low DFI line, relative to the high line (249 v. 190 (s.e.d. 7) g/kg). Muscle colour was darker, as measured by trained sensory panel assessment, in selection lines which reduced the rate of fat deposition to achieve a leaner carcass (high LFC and low DFI) but there was no response in muscle colour with selection for LGA (0·4 and 0·3 v. 0·0 (s.e.d. 0·1)). Responses in muscle shear force (5·3 v. 4·4 (s.e.d. 0·4) kg) and flavour liking (4·0 v. 4·3 (s.e.d. 0·12)) were limited to the LGA and LFC selection groups, respectively. There were no significant responses in muscle moisture content, muscle pH or myofibrillar fragmentation index, nor were there any responses in meat quality with selection on LGS. Therefore, decreasing the rate of fat deposition was associated with darker meat and increasing the rate of lean growth was associated with higher shear force. There were selection strategy specific responses in the fatty acid composition of intramuscular fat, which may have contributed to the responses in eating quality.

In general, responses in meat quality were small, such that incorporation of meat quality traits in selection objectives, which are primarily focused on increasing the efficiency of lean meat production, may not be necessary. However, it would be pertinent to evaluate periodically genotypes of breeding companies for muscle quality traits.

For purely hypertrophic muscle it is postulated that the growth rate in number of nuclei is proportional to the cytoplasmic mass per nucleus multiplied by a growth constraining supplementary function. Growth constraint depends on the distance from any one of the limit number of nuclei, the limit muscle mass or the limit cytoplasmic mass per nucleus. Furthermore, theory and evidence are presented for a power (allometric) relationship between total number of nuclei (n) and muscle mass (m) given by the equation n = gmh. Evidence points to two clusters of values for h, one in the vicinity of h = 2/3 and the other h = 1/2. Both may depend on a linear relationship between number of nuclei inside muscle fibre and fibre cross-sectional area. The difference between the two situations can be derived from basic assumptions on either local or systemic diffusion mediated control of the number or division of satellite cell nuclei, leading directly to values of h either equal to 2/3 or V2. For likely values of h and suitable choices of growth constraints, almost all well known growth functions in the literature are derived as potentially applicable to total number of nuclei, or muscle mass or their ratio. Muscle mass growth will show a sigmoidal form for h = 1. This explains sigmoidal growth in body mass as it is mostly dominated by muscle mass. A possible linear growth phase before maturity is explicable from the cessation of either length (h = 1) or nuclear (h = 0) growth in muscle fibres, while cytoplasmic growth continues to maturity. Furthermore, two rat examples indicate that whole body protein growth can be described by the equations derived for muscle mass growth.

Machine vision can be used to collect images of pigs and analyse them to identify and measure specific areas and dimensions related to their growth, shape and hence conformation. This information could improve the stockman’s ability to maximize production efficiency and also to monitor health by detecting abnormalities in growth rates. This work introduces fully automated algorithms which find the plan view outline of animals in a normal housing situation, divide the outline into major body components and measure specified dimensions and areas. Special attention is paid to determining whether the results are sufficiently repeatable to be useful in estimating these parameters. Problems in compensating for changes in the optical geometry are outlined and methods proposed to deal with them. The repeatability of the image analysis process coupled with the subsequent signal processing for outlier rejection gives s.e. values on areas of < 0·005 and on linear dimensions of < 0·0025. For example, the plan view area less head and neck (A4) can be used to predict the weight of the group of pigs at 34 kg, 66 kg and 98 kg with standard errors of 0·25 kg, 0·17 kg and 0·39 kg respectively when using manual weighing results to calibrate the system. If an individual pig is weighed once at 75 days (e.g. 34 kg) to calibrate the A4-to-weight relationship, subsequent A4 measurements can be used to predict its weight when 125 days old (approx. 80 kg) to within 1 kg. This matches the accuracy of the manual weighing system used in the trials. The effect of pig gender on the area to weight relationships is not significant (P = 0·074), but there is a small yet significant gender effect with the linear dimensions.

Experiment I. One hundred and twenty-five lactations from 88 New Zealand × Californian does were used to study the influence of high fat diets on the performance and milk yield of multiparous rabbit does in two high productivity situations: housed in hot conditions (minimum temperature above 24°C) with eight pups (group H8), or housed in warm conditions (minimum temperature under 21 °C) with 11 pups (group W11). Starting from a control diet (diet C) with 26 g ether extract (ЕЕ) per kg dry matter (DM), two isoenergetic diets were formulated adding fat from vegetable sources up to 99 g ЕЕ per kg DM (diet V) or animal sources up to 117 g ЕЕ per kg DM (diet A). The lactating does showed similar food daily intakes (⋍105 g DM per kg), therefore digestible energy intake of does on high fat diets was significantly higher (P < 0·001). The addition of f at to the diets increased (P < 0·001) milk yield of does (+21 and 24 g/day for diets V and A, respectively) and litter weight at weaning (P < 0·05), and decreased the number of pups replaced (P < 0·01) during lactation. Group H8 does had significantly lower DM intakes, litter growth rates and milk production levels than group Wll does (P < 0·001).

Experiment 2. The effect of these diets on milk composition was determined in 62 lactations from 28 multiparous rabbit does, in which litter size was maintained at eight pups. Milk samples were collected manually on the 7th, 21st and 28th days of lactation. Milk of does given high fat diets, especially diet A, had higher fat and energy contents (P < 0·001) and a lower protein content (P < 0·001) than those given diet C. Milk of does given diet A had a greater DM content than those given the diets С or V (P < 0·001). There was a correlation between the fatty acid composition of milk and dietary fat. The proportion of odd chain fatty acids in the milk fat was lower for does given diet V (P < 0·05) than those given diet A. In conclusion, high fat diets were related to a higher milk yield and energy content of milk, allowing a higher litter weight gain and a lower mortality of sucking pups.

Active immunization against gonadotropin-releasing hormone (GnRH), commonly known as immunocastration, has been proposed as an alternative to traditional methods of castrating bulls. This study evaluated the effects of immunocastration on growth, behaviour and meat quality of post-pubertal bulls. Bulls were either vaccinated against GnRH (no. = 30, I) or left intact (no. = 30, B). A third treatment consisted of steers (no. = 20, S) that had been castrated pre-pubertally. The animals were run in eight single treatment groups (no. = 10 per group), three of each of В and I and two groups of S. Anti-GnRH antibodies developed and plasma testosterone concentrations declined in I following immunization. Aggressive behaviour of I declined to be lower (P < 0·5) than B and no different from S, 5 weeks after primary immunization. Seven weeks after immunocastration all animals were slaughtered. The hot carcass weight of I was between that of B and S but not significantly different from either. There were no effects of treatment on pHu or meat colour measurements. Taste panel assessment rated I higher than B, but lower than S for tenderness, juiciness and overall palatability. These results demonstrate that immunocastration of post-pubertal bulls 7 weeks before slaughter is a potential means of reducing problematic bull behaviour and improving meat quality although this is likely to be at the cost of reduced weight gain.

The objective was to elucidate the influences of two analytical methods, which employed neutral detergent or enzymes, on the digestion of carbohydrate fractions in the rumen and post-rumen of steers. Structural carbohydrates in diets and digesta were directly measured using both procedures and the contents of non-fibre carbohydrates (NFC) and non-fibre non-starch polysaccharides (NFSP) were estimated by subtracting the structural carbohydrates and other components from the organic matter. Carbohydrate sources were Italian ryegrass and rolled barley in the control diet and, in each of other three diets, Italian ryegrass and rolled barley plus either beet pulp, citrus pulp or soya-bean hulls. All diets contained similar proportions of dry matter as crude protein, structural carbohydrates and NFC but the starch proportion of the NFC was different in each diet, as follows: control (0·62), beet pulp (0·48), citrus pulp (0·30) and soya-bean hulls (0·63). Four Holstein steers with ruminal, duodenal and Heal cannulas were offered the four diets in a 4 × 4 Latin-square design. Estimated digestibilities of the structural carbohydrates in the rumen and the whole tract were greater (P < 0·01) when the detergent method was used than when the enzymatic method was used. The maximal difference in the ruminal digestion among the four diets was only 0·05 by the detergent method but 0·17 by the enzymatic method. Conversely, the digestibility of NFC in the rumen, as estimated from the detergent structural carbohydrates was less (P < 0.01) than that estimated from enzymatic structural carbohydrates with no evident differences among the four diets. Starch digestibility in the rumen was extensive for all diets but the ruminal digestibility of NFSP was much lower in the control and soya-bean hull diets, especially when it was estimated using the detergent method. The duodenal flow of microbial protein was greater (P < 0·05) for the beet pulp and citrus pulp diets than for the control. The acetate concentration of the ruminal fluids ranged from 84 for the control diet to 128 mmol/l for the soya-bean hulls diet. The digestion of carbohydrate fractions and the fermentation characteristics in the rumen suggested that the enzymatic method is the more appropriate method for fractionating carbohydrates.

Meals prepared from low glucosinolate rapeseed screenings (SCREEN) and from seed which had heated during storage (HEAT) were compared against commercial rapeseed meal (COM) for feeding value. Oil, crude protein (CP) and acid-detergent insoluble nitrogen contents in SCREEN, HEAT and COM, respectively, were (g/kg): 118, 246 and 13; 227, 315 and 436; and 17, 64 and 21. in situ dry matter (DM) and protein disappearance rates, soluble protein fraction and effective rumen degradability of protein (EDCP) were lower (P < 0·05) in HEAT than in SCREEN or COM. Comparing oil-extracted meals in situ, EDCP of HEAT was lower (P < 0·05) than EDCP of SCREEN or COM but protein and DM disappearance rates of HEAT were only lower (P < 0·05) than those of SCREEN. Four isonitrogenous barley-based diets (150 g/kg CP, DM basis), containing SCREEN, HEAT, COM or COM supplemented with rapeseed oil (OIL), were given to lambs. For DM, organic matter and neutral-detergent fibre apparent digestibilities, the diets ranked SCREEN > HEAT = OIL > COM (P < 0·05). Digestion and retention of nitrogen were lower (P < 0·05) in lambs given HEAT than in lambs given other diets. Food efficiency of lambs given HEAT was improved (P < 0·05) as compared with lambs given SCREEN or COM. Dressing proportions were higher (P < 0·05) with HEAT, SCREEN and OIL diets than with COM. Other than minor changes in fatty acid composition of subcutaneous fat with HEAT and OIL, carcass traits were not altered by treatment. Feeding SCREEN or HEAT did not adversely affect animal performance or food utilization.