In a population of 268 yearling bulls, those carcasses graded as U−, U0 or U+ for beef carcass conformation (n = 240) and those graded as 2−, 20 or 2+ for beef carcass fatness (n = 213) were selected to study the efficiency of carcass weight, carcass dimensions and instrumental colour of latissimus dorsi, rectusabdominis and subcutaneous fat, to discriminate among these carcass grades, in a population of high-muscled and very lean carcasses from young bulls. The increase in conformation grade meant an increase in carcass weight and perimeter of the leg. Classifiers use attributes characterizing muscular development and carcass profiles from a general impression of the whole carcass. There were no significant differences for carcass weight or carcass dimensions, among the carcasses classified according to the three fat classes. The a* and b* coordinate values for the latissimus dorsi muscle were observed to decrease significantly as the carcass conformation score increased (P < 0.05). However, muscle and subcutaneous fat of fatter carcasses showed higher a*, b* colour coordinates and chroma (C*) values than leaner carcasses. The CIE (Commission International de l’Éclairage) L*, a* and b* colour coordinate measurements taken on the carcasses 45 min post mortem varied significantly from the readings taken after hanging for 24 h (P < 0,001). The higher a* and b* values on the carcasses chilled for 24 h could be caused by oxygenation of both subcutaneous fat, and latissimusdorsi and rectusabdominis muscles in the time elapsing after slaughter and after carcass exposition to circulating air in the cooler for 24 h. Lightness of the latissimus dorsi muscle underwent a decrease, compared with an increase in the rectusabdominis muscle. Hardening of the subcutaneous fat during cold storage may exert an influence on the decrease in lightness observed. These differences in carcass colour during chilling storage would suggest that the relationship between carcass colour and conformation grades was higher shortly after slaughter. Both L* colour coordinate of fat colour (P < 0.01) and a*, b* and C* colour coordinates of latissimus dorsi muscle (P < 0.05) were related to conformation classification. Colour was more efficient to differentiate conformation than fat cover classes. Sixty-two percent of carcasses were correctly classified for conformation by colour differences but only 37% of carcasses were correctly classified for fatness by colour.

Six castrated male sheep were used to measure the apparent digestibility of fodder beet roots when included at two concentrations (610 and 490 glkg) in a feeding regimen in which the only other component was a standard complete diet of known digestibility. Mean digestibility coefficients for organic matter and gross energy for the beet were calculated to be 0·962 and 0·953 respectively. Digestible and metabolizable energy values (MJIkg DM) were calculated to be 16·0 and 13·1 respectively.

Thirty-six individually penned lambs (mean live weight 32·4 (s.d. 2·27) kg) were offered maize silagead libitumand one of three concentrate mixes, two of which contained extracted rapeseed meal (control and HR) and the other fish meal (FM). The concentrates were given according to live weight and in sufficient quantities to provide proportionately about 0·4 of the dry matter (DM) intake of the lambs. The dietary concentrations of nitrogen (N) g/kg DM were 22·4, 27·4 and 27·5 and of rumen undegradable N 6·6, 7·3 and 11·6 for the control, HR and FM diets respectively.

Both the HR and FM diets depressed maize silage intakes compared with the control during the first 21 days (P < 0·05) and lambs given the FM diet continued to have lower intakes than control lambs (P < 0·05) throughout the experiment. The live-weight gain of HR lambs was considerably depressed in comparison with the control and FM lambs during the first 21 days of the experiment (P < 0·05). Overall HR lambs gained weight more slowly than control and FM lambs up to 45 kg live weight but the difference was not statistically significant. Food conversion ratio was better for FM than HR (P < 0·01). There were no treatment differences in wool growth.

The results obtained provide little evidence that fish meal had any beneficial effects upon lamb growth compared with the control diet except a possible increase in the efficiency of metabolizable energy utilization.

There are two schools of thought concerning the most appropriate environment in which to select breeding animals. One says ‘ Always select animals under environmental conditions similar to those where they are to be used ‘. The other says ‘ Select breeding animals in the optimum environment so that they have the best chance of revealing their genetic capabilities ‘. Experiments on growth of laboratory mice and experience with European cattle in the tropics have shown the advisability of the first course in these cases. In regard to hill sheep and dairy cattle in Britain, on the other hand, practice favours the second course, but there is little experimental evidence to support it.

In an integrated group housing system for sows, animals of all stages of production are kept in one group, except around farrowing, and remain there throughout their productive life. Lactating sows have access to the suckling section of the house via an electronic gate. Jostling of piglets from different litters is avoided by keeping the litters in their own suckling pen until weaning. The system allows lactating sows to freely evade their piglets, and move between the suckling section and the communal area. They can maintain their social position and cool off in the relative cool communal area. Earlier observations (Houwers et al., 1992) showed sows decreased sucklings and increased their absence from the farrowing pen towards weaning. It was not clear whether the overall performance of the piglets was depressed by absence of sows before weaning. The relevance for practical farming partly depends on the production results that can be achieved.

A general parabola constrained to pass through points (0,0) and (1,1) yields a linear one parameter (q) function which can be used to relate the fraction of maturity of organs or masses of tissue to the fraction of maturity of the whole animal. This is an empirical approach. It is often preferable to derive a function from a theory of the phenomenon under study. A theory of feeding and growth of animals is used to derive a non-linear one parameter (k) function which can be used to study the same data to which the linear q-function is applicable. The parameter, k is directly proportional to the fraction of total nutrients consumed by the animal which is allocated to the organ as the animal ages. If the fraction of nutrient allocated remains constant, the parameter k is constant and has the same properties as the parameter q. However there is nothing in the theory which constrains k to be constant, therefore, the q-function is of more general use than the q-function in the study of the relationship of the fraction of maturity of organs to that of the whole animal. Two cases are presented to illustrate this generality.

High food intake in early pregnancy resulted in increased prenatal mortality and reduced subsequent litter size in many studies using gilts (den Hartog and Van Kempen, 1980). With multiparous sows there is generally no difference in the rate of embryo survival or litter size with high feeding in early pregnancy (Toplis et al, 1983, Dyck & Cole, 1986).

Limited evidence suggests that sows fed low levels in lactation and then a high level early in the following pregnancy may show increased rates of embryo mortality (Pike and Boaz, 1972; Hughes et al, 1984). The effect of high feeding may be due to low plasma progesterone concentrations (Hughes et al 1984; Dyck et al, 1980) in early pregnancy which may be associated with reduced embryo survival and litter size.

This study was designed to investigate the effects of high or low feed intake in lactation and early pregnancy on plasma progesterone concentrations in early pregnancy and subsequent litter size using multiparous sows.

The fact that laying hens prefer to lay in a nest is not evidence in itself that a suitable nest-site is necessary for the hens’ well-being. Stronger evidence would be found if hens were prepared to pay some cost to use a nest-site. The objective of this study is to quantify the strength of individual hens’ nesting motivation in terms of meaningful measures such as overcoming aversive obstacles, work or time.

To investigate the motivation to gain access to a nestbox, hens were floor housed in groups of four in a pen containing food and water. Access to a nesting pen containing two nestboxes, could be restricted using a number of obstacles such as a narrow gap, a water bath and a swing door. Between trials hens were singly housed in wire-floored cages containing a perch and a nestbox. Results indicate that hens made less entries of longer duration to the nesting pen (Means + s.e in Figures 1 and 3) on treatment days with an obstacle than on control days without an obstacle. There was little disruption of use of the nest box (Figures 2 and 4). Hens that were due to lay made more visits on both control (C Egg) and treatment (T Egg) days (Figure 1), which may indicate greater motivation to explore the whole pen before oviposition.

The use of the ‘anti oestrogen’ clomiphene to increase the ovulation rate of the sheep was investigated. Although in most trials clomiphene had a positive effect, this effect was small and inconsistent—especially n i relation to dose. It was concluded that the present approach would not lead to a simple technique to increase ovulation rate and the number of lambs born.

The first objective of this trial was to evaluate swedes of different dry matter content developed by the Scottish Crop Research Institute in particular to determine whether dry matter content and related hardness were appropriate for the grazing situation. The second objective was to study the performance of Highland Mule wether lambs (Bluefaced Leicester x Blackface) (BFLX) compared to Suffolk x Blackface (SX) and Cheviot (C) wether lambs. The Highland Mule wether lamb is a by-product in the production of Highland Mule ewe lambs for breeding and the specific interest was in whether there was any deleterious effect on finishing performance associated with the Bluefaced Leicester sire.

Representative lambs of the genotypes involved were purchased in September and run on grass and stubbles until the start of the swede feeding period (2 November) with the aim of maintaining liveweight. Liveweight was 33, 33 and 36 kg for BFLX, S and C respectively on 2 November. Adjacent plots of the swede varieties Dryden (D), Melfort (M) and Doon Major (DO) were grown in one field (two replicates) and 33 lambs of each genotype grouped and allocated to each variety.

The proposed Agricultural Research Council (ARC 1984) protein evaluation system for ruminants provides lower nitrogen allowances than any other. (National Research Council 1985; Alderman 1987). A U.K. Interdepartmental Working Party (IDWP) was set up to consider the ARC (1980) proposals and recommend a practical protein evaluation system for ruminants for use by the advisory services. Its provisional proposals have been reported by Webster (1987). This trial was set up to provide a practical evaluation of the two systems in a commercial dairy herd.

Animals. Thirty-three Friesian cows (mean livewewight 590kg, mean previous milk yield 6120 kg), in early lactation were blocked according to (a) previous treatment, (b) number of previous lactations and (c) previous milk yield. The cows were randomly allocated within blocks to one of three dietary treatments.

Treatments. Dietary nitrogen allowances were calculated, according to (1) ARC(1984) and (2) IDWP (Webster, 1987) except that the ARC (1984) concept of essential amino acid nitrogen was included in the IDWP calculations. The difference in nitrogen allowances between the two systems was so great as to warrant a third intermediate treatment (INT), calculated to provide allowances mid-way between the other two.

There is a clear need to improve financial returns from hill sheep to help maintain rural populations in hill/upland areas while at the same time reducing the reliance of hill sheep farmers on social/production type subsidies. Particular problems with hill sheep are their small carcass size and poor conformation, which result in reduced values for both draft ewes and wether lambs. These poor carcass attributes are also passed down to the lowland producer through the production of poor conformation halfbred ewes out of hill ewes. With the increasing pressures being placed on the lowland sector to improve carcass quality, many producers are beginning to look at the possibility of breeding their own replacement top-cross ewes. Any widespread adaption of this practice will further undermine the profitability of sheep production in the hill and upland sectors.

Since the cell wall content (CWC) and cell wall digestibility are the main factors influencing the animal's energy supply from forages, the ability to accurately measure CWC is crucial. This is becoming increasingly important as feed evaluation methods move towards a more dynamic approach of assessing nutrient supply from a wide range of substrates in order to reflect the two-stage nature of digestion in ruminants. Originally developed for forages, the neutral detergent fibre (NDF) procedure of Goering and Van Soest (1970) is generally regarded as providing a satisfactory measure of CWC despite the fact that varying amounts of cell wall pectins are soluble in neutral detergent solution (Chesson, 1986). However, previous work (IVVO, 1991) suggests that sample drying temperature and other factors can influence the measurement of CWC. An experiment was undertaken to study the effect of different drying temperatures and method of NDF analysis on the measurement of CWC in different forage types.

Ultrasonic probe data were available on 199 crossbred pigs (98 females, 101 barrows). These animals were probed at approximately 30, 50, 70, 100 and 120 kg live weight with two probing instruments (Krautkramer USM2, Combison 310) at three sites along the back. The measurements were examined as predictors of the proportion of valuable cuts (part dissection) and estimated lean concentration (at 100 and 120 kg live weight).

The standard deviations for proportion of valuable cuts (after correcting for sex effects) were 24·8, 26·7, 23·4, 27·1 and 29·4 g/kg at 30, 50, 70, 100 and 120 kg. Residual s.d. for predicting proportion of valuable cuts from live weight and ultrasonic probes (Combison, quotient fat to muscle area) were 190, 20·9, 19·3, 213 and 19·6. For the USM2, the residual s.d.s were 19·2, 26·3, 19·9, 25·1 and 24·6. Thus the Combison probe provided a better prediction of proportion of valuable cuts. The standard deviations of estimated lean concentration as determined by a Fat-O-Meater reflectance probe were 28·9 and 39·3 at 100 and 120 kg live weight. The residual s.d.s from live weight and ultrasonic measurements were 15·4 and 19·2 for the Combison probe and 21·5 and 20·5 for the USM2 probe. If the estimated lean concentration is accepted as a selection objective the value of ultrasonic probes as criteria in selection indices will increase.

The N fraction of fresh grasses, silages and hays is generally considered to be extensively degraded in the rumen. However published N degradability values for each type of material vary over quite a wide range. This may, at least in part, be due to an effect of the stage of growth of the harvested material since with increasing maturity there are marked changes in chemical composition and botanical features. Accordingly the ruminal N degradability characteristics of perennial ryegrass, harvested at different stages of growth and conserved as hay or silage, were determined using the polyester bag procedure.

Crops of young primary growth (C1), first regrowth (C2) second regrowth (C3) and mature primary growth (C4) were harvested from a field of perennial ryegrass c.v.S23. For each crop the fresh grass was stored frozen, conserved as field-cured hay and conserved by ensiling in laboratory silos either directly or after wilting and in both cases with or without formic acid addition (3l/tonne). The silos were opened after 90d and the silages subsequendy stored frozen.

1. Two groups of ewes were given a dietary supplement containing 40 g of either ‘protected’ tallow (PT) with only 3% linoleic acid or ‘protected’ safflower oil (PP) with 57% linoleic acid for 28 days prepartum and 30 days post-partum.

2. Although the birth weights of the lambs were unaffected by dietary treatment, the lambs in the PT group gained weight approximately 20% faster than those in the PP group.

3. The gross compositions of the milks of both groups of ewes were similar but the milk fat obtained from the PP group contained about twice as much linoleic acid as was found in the PT group.

4. Dietary treatments did not affect the haematocrits, red blood cell (RBC) or white blood cell numbers of the lambs. However, the haematocrits were higher at birth than at 10 days later and the RBCs were found to be less fragile at birth than at 10 days later.

5. The ratio of trienoic/tetraenoic fatty acid in the plasma lipids of the lambs was positively correlated with live-weight gain. Male lambs grew faster than females and twins faster than triplets and the trienoic/tetraenoic ratio was higher in males than females and higher in twins than in triplets.

6. These results showed that although it was possible to increase the linoleic acid content of the milk of ewes and of the blood lipids of their lambs by feeding protected safflower oil, no increase in lamb growth was obtained.

Cattle not fed a supplement on dry season grazing lose weight. The magnitude of this loss and the extent of recovery during the subsequent wet season were measured in Mashona steers.

Mashona steers aged 8 and 20 months at the outset (groups A and B respectively) were used. Within each group (n = 50) steers were fed cottonseed meal (CSM, 250g per 100kg live-weight) or not fed CSM during the dry season.

Twenty-four bull calves, eight Hereford × Friesian, eight Aberdeen Angus × Friesian and eight Friesian, were reared from birth to slaughter at 13 weeks of age solely on a milk substitute diet given ad libitum.

Samples of jugular blood were taken at weekly intervals from 5 days to 89 days of age for determination of concentrations of prolactin, growth hormone (GH), insulin and total thyroxine (T4) in plasma, tri-iodothyronine (T3) uptake, and thus free T4 index (FTI).

The Friesian calves had a higher mean body temperature and lower mean T3 uptake than did either of the beef crosses.

The Aberdeen Angus cross had a higher mean dry-matter intake per unit of metabolic body size (DMI/W0·73), heart rate and plasma insulin concentration than did the Hereford cross, and a higher insulin concentration but not a higher heart rate than did the Friesian. Live-weight gain and DMI/W0·73 for the Friesian was intermediate between that of the Aberdeen Augus cross and the Hereford cross.

DMI/W0·73 was positively correlated with insulin: GH ratio, prolactin: GH ratio and T4: GH ratio.

The increase in heart rate per unit DMI/W073, a measure of the heat increment of feeding, was negatively correlated with the plasma insulin concentration, insulin: T4 and insulin: GH ratios.

Prolactin concentration, GH concentration and T3 uptake declined with age, whereas insulin concentration, T4 concentration and FTI increased with age. The relationship was linear for prolactin and insulin concentrations, but curvilinear for the other variables. The Friesian breed had a higher GH concentration than did the beef crosses during the first 12 days of life. The large increase in insulin concentration for the Aberdeen Angus × Friesian occurred from about 47 days of age. The peak T4 concentration and the lowest T3 uptake of the breeds occurred between 33 and 42 days of age.

Possible mechanisms for the control of dry-matter intake by preruminant calves and the difficulties associated with prediction of performance from plasma metabolic hormone concentrations obtained at a young age are discussed.

Malt distillers grains (MDG) and brewers grains (BG) are the fibrous residues remaining after the extraction of sugars from malted barley during the process of malt whisky and beer production, respectively. MDG and BG are popular supplements in beef finishing diets with up to 15kg/head/day being fed on Scottish farms (Lilwall, Smith and Wood, 1983). However, in some areas, close to distilleries and breweries, and particularly during the summer months, MDG and BG can be bought cheaply and ensiled, and could be fed to appetite as the sole or major part of the diet. This investigation explores this possibility.

Some unusual limitations of MDG and BG as a complete diet are that they are virtually devoid of soluble minerals such as Na and K and are low in some trace elements and vitamins. They also contain high levels of unsaturated fats which depress fibre digestion and voluntary dry matter intake (Miller et al., 1970). This effect can be partly overcome by supplementation with calcium carbonate (El Hag et al., 1972) probably by the formation of insoluble calcium soaps of fatty acids in the rumen. Based on these considerations a mineral/vitamin mix was designed specifically to supplement these materials.