The rationale for a method of computing selection indices for dairy cows is outlined. It uses predicted transmitting abilities of sires from a best linear unbiased prediction or similar method of evaluation together with mean transmitting abilities (cow indices) of dams to estimate herd genetic levels. Indices for individual cows are computed using deviations from those of contemporaries in the herd of her sire's transmitting ability, her dam's index and her own production in each lactation.

The method is being used in the UK, cow indices being expressed as transmitting abilities relative to the same fixed genetic base as for sire evaluation.

In 1979/80, 390 cows of black and white breeds produced more than 750 kg fat plus protein in a 305-day lactation, compared with a mean of 390 kg for all recorded black and white cows. The cows were distributed in 207 herds and were the daughters of 177 sires whose breeding values (with population means in brackets) were +220 kg milk ( + 100), +8 kg fat (+5) and +6 kg protein (+2). The farms on which they were kept were not markedly different from average holdings in England and Wales. Management was characterized by high labour input, with high intakes of diets containing a high energy and protein concentration, and care was taken to ensure that food was on offer at all times. Grassland management tended towards conservation by silage rather than hay. Calving intervals were slightly longer than average (393 days v. 386 days for all recorded cows of a similar age).

The most obvious characteristic of management was the close attention given to ways of persuading the animals to eat enough food to satisfy their nutritional requirements.

A total of 182 pigs from one farm and comprising 65 boars (B), 65 gilts (G) and 52 castrates (C) from 48 litters, were reared from birth to 89 kg live weight. Sex of pig did not influence age at slaughter but B compared with G and C had lower killing-out proportions (0·748 v. 0·756 v. 0·753) and reduced backfat measurements. Skin damage in transit to slaughter and/or in lairage was more prevalent in B compared with C, with G being intermediate. Muscle pH measurements were not influenced by sex except ultimate pH of the m. semispinalis capitis, where B compared with G and C had a higher incidence of values above 6·1 (0·246 v. 0·060 v. 0·120). Carcasses of B had proportionately more shoulder (0·04 unit) and more leg (0·011 unit), at the expense of middle, than those of C with G being intermediate. Weight losses in the preparation of de-boned sides for curing were higher in carcasses of B compared with G and C.

Plasma hormone concentrations and metabolite responses to changes in energy equilibrium were measured in experiments designed to compare a) Hereford × Friesian with Friesian calves and b) Friesian calves sired by bulls with a high level of Improved Contemporary Comparison with those sired by bulls of a low level. The concentration of thyroxine and triiodothyronine tended to be greater in calves of higher dairy merit. The concentration of growth hormone was largely unrelated to dairy merit in the circumstances studied. The concentration of insulin was greater in Hereford × Friesian than in Friesian calves following feeding and following the injection of propionate. Responses to the injection of insulin and of growth hormone (as measured by changes in the plasma concentration of urea nitrogen, free fatty acids, glucose or the other hormone) were little affected by the level of Improved Contemporary Comparison of a calfs sire.

It was concluded that the thyroid system and the response of insulin to perturbation of energy balance may provide criteria of genetic merit for milk production which are neither age- nor sex-limited.

Curing data were obtained from the carcasses of 54 boars (B), 58 gilts (G) and 46 castrates (C) reared from birth to slaughter at 89 kg live weight. Middle bacon rashers were compared for colour and incidence of fat splitting. The uptake of curing salts was similar for each sex group but carcasses of B retained proportionately 0012 less of the cure compared with G and C which did not differ significantly. Bacon yields from B, G and C at a final live weight of 88·6 kg were 40·6, 42·4 and 42·2 kg respectively. Sex did not influence the degree of splitting of the backfat layers in bacon rashers and had little effect on the colour of their lean tissue, but B compared with G and C tended to have a higher incidence of separation of the inner fat layer from the m. longissimus in the bacon rasher.

The relationship between the composition of the fat-free carcass and carcass fatness was studied by considering the relationship as one between two shape vectors, with the effect of size removed, using an extension of the multivariate linear least squares technique for studying multivariate allometry.

In two sets of data, one of dressed carcasses of cattle and the other of empty carcasses of lambs, the composition of the fat-free carcass (in terms of protein, water and ash) was significantly related to carcass fatness (P < 0·10 and P < 0·05 respectively). The consequences of this relationship to the study of the chemical composition of carcasses are discussed.

Examination of the relationship in more detail showed that the fatter carcasses were those with more protein and less water in their fat-free carcass, in both sets of data, and with more ash in the empty carcasses of lambs.

Lifetime maternal performance records of 113 Angus cows born over a 12-year period were used to estimate the relationship between cow size characters, mature size (A) and maturation rate (K), and lifetime maternal performance characters, years in the herd (YH), number of calves (NC), total calf weight (TW), average calf weight at weaning (AW) and calf weight per year in herd (kg/year). Pertinent reproductive management of the herd was: heifers were mated to calve as 2-year-olds; any heifer failing to calve or any cow failing to wean a calf a second time was culled; all matings were to purebred Angus sires. Mean cow mature size was 487 ± 5 kg with a maturation rate of 0·058 ± 0·001. Means for maternal characters were: YH, 7·4 ± 0·4; NC, 6·4 ± 0·3; TW, 1283 ± 71; AW, 200 + 1·8; and kg/year, 173 ±5·1. The correlations between maternal characters and A and K, respectively, were: YH, −0·21, 0·15; NC, −0·21, 0·15; TW, −0·16, 0·12; AW, 0·20, −0·15; and kg/year, 0·05, −004. The regression of maternal characters on mature size was quadratic in every instance with optimal cow size for each character being: YH, 468; NC, 465; TW, 471; AW, 493; and kg/year, 475. The optimal cow size for average weight of calf weaned was 18 to 25 kg heavier than the optimal size for those characters associated with fertility. Relationships between maturation rate and maternal performance were not statistically significant.

Consumer reaction to bacon from boars and castrates, whose production and processing characteristics were known, was determined in 122 households consisting of 238 respondents. On a seven-point scale the mean scores for six organoleptic characteristics were similar for each sort of bacon relative to that usually purchased. A proportion of 0·045 of cooks scored boar bacon at the point of strongest rejection (unappetizing aroma) during cooking but less than 001 considered that the flavour was very much stronger than their usual bacon. Few respondents marked boar bacon inferior to their usual bacon for eating characteristics. On a comparative basis the frequency distribution of scores for flavour, juiciness and pleasantness of aroma on the plate was slightly in favour of castrate bacon but was of little importance. Using the production and processing data obtained and accepting no adverse consumer reaction to boar bacon, a financial advantage to the producer of entire male pigs for bacon manufacture over castrates was demonstrated (£2·95). However, if the retailer should not reward the curer for the extra leanness of the boar then the curer might be at a financial disadvantage.

The maintenance energy requirements of 29 Hereford × Friesian and 27 Blue Grey (White Shorthorn × Galloway) cows each offered one of six levels of feeding supplying between 0·5 and 1·2 likely maintenance requirements for 56 days were estimated, from regressions of daily live-weight change on energy intake, as the energy intake corresponding to zero live-weight change.

There were no effects of level of intake on diet digestibility or of genotype on maintenance requirements.

Maintenance requirements (M, MJ metabolizable energy per day) were shown to be determined by both live weight (LW, kg) and body condition score (C) according to the relationship: M = 0·147LW – 0·016C.LW.

The estimates derived are compared with other published values and the hypothesis is advanced that maintenance requirements are likely to be more closely related to body protein mass than to body weight.

The dietary energy equivalent of 1 kg loss of live weight is calculated to be 26·7 MJ and it is estimated that in non-lactating cows body tissue is used for maintenance with an efficiency of 0·77.

Two experiments examined the effects of including sodium bicarbonate in the diet of dairy cows in early lactation for two different feeding systems. In experiment 1, 28 Friesian cows were allocated to two groups according to parity, calving date and their milk yield in days 5 to 14. Cows were given either a standard home-mixed concentrate or a similar concentrate with sodium bicarbonate included at 25 kg/t. Concentrates were given to individual cows twice daily at a flat rate determined by their 5- to 14-day yield, and hay was group-fed to appetite. Milk yield in days 15 to 100 post-calving did not differ significantly between treatments, but cows given concentrate containing bicarbonate ate more hay and had a higher milk fat concentration (36·0 v. 32·5 g/kg, P < 0·01). In experiment 2, 80 cows were allocated to two treatments according to parity, calving date and previous lactation yield. There were two replicates of each treatment. All groups were given silage and concentrates as a complete diet for 8 weeks from calving, and 20 g sodium bicarbonate per kg total dry matter was included in the diet of half the animals. Cows given the diet containing bicarbonate had higher food intakes (14·9 v. 13·9 kg dry matter per head per day) and lower live-weight losses (13 v. 44 kg, P < 0·001). Milk yield and milk quality did not differ between treatments. Conception tended to be better in cows given the bicarbonate diet.

The objective of the studies reported was to examine the potential usefulness of measurements of concentrations of plasma glucose, 3-hydroxybutyrate and non-esterified fatty acids as means of assessing in quantitative terms the adequacy of energy intake of beef cattle.

Relationships between the concentrations of these metabolites and of either energy intake or energy status were examined in three experiments conducted respectively on 56 housed, mature, non-pregnant, non-lactating cows, on 115 housed, mature, pregnant cows, and on groups of 10 to 12 mature, non-pregnant, non-lactating cows grazing five plant communities.

The results indicated that under the conditions pertaining in these studies plasma glucose concentration was not likely to constitute a useful index of energy status in housed or grazing animals.

Plasma 3-hydroxybutyrate concentration was closely related to estimates of energy status in the pregnant cows and was considered to be potentially valuable as an index of energy status in animals in which there is a relatively high glucose demand.

Plasma non-esterified fatty acids concentration was closely related to and a potentially useful index of either energy intake or energy status in all cases, but postulated effects of diurnal variations in circulating concentrations make it imperative that relationships used for predictive purposes are derived under the conditions in which they are to be applied.

Ninety-two gilts in replicates of four littermates were mated at puberty at a mean live weight and age of 95 kg and 191 days respectively. The littermates were allocated at random to one of four food allowances (kg/day) during four successive gestations: (A) 1·5, (B) 2·0 in parity 1 followed by 1·5 in subsequent parities, (C) 20 and (D) 2·5. A diet calculated to contain 12·7 MJ digestible energy per kg was fed throughout gestation, the 2-week lactation and from weaning to conception.

The numbers of sows which conceived at parity 5 when the experiment terminated were 10, 12, 13 and 16 for treatments A to D respectively. Sow live weight at conception differed significantly (P < 0·01) from parity 2 onwards: the maximum live weights of sows on treatments A and B did not exceed 130 to 135 kg, but the live weights of sows on treatment D continued to increase to reach 195 kg at the end of the experiment. The in vivo skin plus subcutaneous fat thickness at the P2 location differed significantly (P < 0·001) between treatments from parity 2 onwards, decreasing by 3 mm in treatment A and increasing by 6 mm in treatment D from the start of the experiment to conception at parity 4. The interval from weaning to conception was significantly (P < 0·05) lower in treatment B in parity 2. This was the only significant effect and was contrary to the tendency for the interval to increase as the food allowance in gestation was decreased. The numbers of pigs born alive, stillborn or weaned (including fostered pigs) were not significantly affected by treatment. Birth weight and post-natal growth rates were significantly (P < 0·05) increased after parity 1 as gestation food allowance increased, with the exception of the post-natal growth rate in parity 3. Overall birth weight was increased by 018 kg per pig and weaning weight by 0·93 kg per pig on treatment D compared with treatment A.

The nylon bag technique was used to determine the effects of offering to steers an allowance of turnips in a diet based on straw on the degradation of dry matter and acid-detergent fibre of the straw. Rumen-cannulated steers were offered basal diets of (a) sodium hydroxide (NaOH)-treated straw ad libitum, (b) NaOH-treated straw plus turnips (50 g dry matter per kg W0·73) offered once daily or (c) turnips ad libitum. Samples of straw, treated with NaOH, anhydrous ammonia (NH3,) or untreated straw were incubated in nylon bags in the rumen along with each of the basal diets. Additionally molasses (66 g dry matter per kg W0·75) was infused into the rumen of the steers offered the NaOH-treated straw. Dry matter and fibre losses of straw from nylon bags were in the order NaOH-treated > NH3,-treated > untreated; there was no interaction (P > 0·05) between method of straw treatment and effect of basal diet on 40-h or 72-h dry matter or fibre degradability. Supplementation of the basal straw diet with either turnips or molasses depressed (P < 0·01) degradability of both dry matter and fibre of the incubated straw at 40 and 72 h, molasses infusion producing a greater depression (P < 0·05) than offering turnips. There was a fall in rumen fluid pH shortly after steers consumed their turnip allowance or molasses was infused into the rumen, minimum pH values were 6·09 ± 0·241 and 5·75 ± 0·205 respectively. The pH of rumen fluid and degradability of dry matter and fibre of barley straw were depressed by the presence of carbohydrates in turnips and molasses. A reduction in the activity of cellulolytic bacteria may have been the cause of the depression in straw degradability.

One hundred and fourteen pig carcasses were measured within 1 h of slaughter for fat thickness at three locations using the SFK Fat-O-Meater. The three fat thickness locations were the last rib and 3rd and 4th last ribs measured 70 mm from the dorsal mid-line over the m. longissimus, and the lumbar fat thickness which was recorded on the anterior face of the m. glutens medius on the dorsal mid-line of the split carcass. Lean depth measurements were also recorded at the last rib and 3rd and 4th last ribs for all carcasses. After overnight chilling the leanness of each carcass was estimated using an EMME SA-1 machine. The carcasses were then separated into the major tissues. The weight of trimmed North American commercial joints (standard of 6 mm subcutaneous fat) and their lean content were best predicted by half carcass weight (residual s.d. = 0·78 and 1·23 kg respectively), whereas the EMME machine readings alone had low precision (residual s.d. = 1·51 and 1·41 kg respectively). The proportion of North American commercial joints in a carcass and their lean content were best predicted by lumbar fat (residual s.d. = 16·5 and 25·8 g/kg). The digital readout of lean content provided by the EMME machine appeared to be more related to carcass weight than lean weight, as residual s.d. for regressions increased when the overall sample was divided into two weight classes. Multiple regression equations indicated that half carcass weight and fat thickness measurements gave the best precision to predict joint and lean weights, whereas fat thickness and lean depth measurements gave the best prediction of carcass joint and lean proportions.

Sixteen British Friesian-cross steers of early- or late-maturity types were reared on either a 16- or a 24-month system of production. The steers on the 24-month system were subjected to a reduced nutrient intake during two phases of growth: 1) during early growth when the steers were approximately 9 months old and 2) during a store period when the steers were 13 to 19 months old. Animals on the 16-month system were fed to appetite throughout. Blood sampling was carried out at various periods during growth and serum samples were analysed for growth hormone, insulin, prolactin, glucose and blood urea nitrogen. Serum growth hormone concentrations were elevated during reduced nutrient intake, whilst serum insulin concentrations fell. Serum prolactin followed a seasonal pattern, but was lower in the underfed steers. Serum glucose concentrations also tended to fall during underfeeding, but blood urea nitrogen results were inconclusive. Hormone concentrations were not influenced by the maturity type of the steer, suggesting that the hormones measured are not primarily involved in determining the differential growth patterns in steers of different maturity types.

1. The primary growth of perennial ryegrass was cut between 7 and 9 June and ensiled with formic acid at 2·5 1/t. The regrowth was cut on 24 July; part was dried at high temperature (dried grass), the remainder was left to dry in the field (hay). The dried grass (DG) and part of the hay were ground and pelleted, the hay being pelleted alone (PH) or with the addition of formaldehyde at 20 g/kg crude protein (PHF). The remainder of the hay was offered in the chopped form (CH). The four supplements (CH, PH, PHF, DG) were offered at two levels, 6·5 (L) and 130 (H) g dry matter per kg live weight to 54 British Friesian steers (initial live weight, 110 kg) receiving the silage ad libitum.

2. The silage had a high pH and a high proportion of the total nitrogen was in the form of ammonia, indicating poor fermentation. The solubility of nitrogen in the supplements was highest (262 g/kg total nitrogen) in CH, progressively less in PH and PHF and lowest (122 g/kg total nitrogen) in DG.

3. Total dry-matter intake was highest with DG at the higher level of inclusion. Dry-matter intake was significantly higher for PH and PHF than for CH (P < 0·001). However, intake of digestible energy did not differ between hays. Live-weight gain was increased from a low level of 0·24 kg/day (silage alone) by all supplements, but this effect was greater with DG than with the hays (P < 0·001). Level of supplementation increased live-weight gain from 0·54 to 0·74 kg/day.

4. Supplements of dried grass gave higher live-weight gains than did hay made from the same sward. However, the results indicate that supplementation of badly preserved silage with grass hay of good quality can produce acceptable levels of performance of up to 0·70 kg/day in 4-month-old steers. Processing of the hay had little effect on animal performance.

Hereford ♂ × British Friesian ♀ cows that had calved in September/October and were suckling mainly Charolais ♂ × calves were offered individually one of three planes of nutrition based on their estimated maintenance requirement during their first 150 days of lactation.

The mean daily intakes of metabolizable energy were 95·8, 71·5 and 52·1 MJ for the high, medium and low planes of nutrition respectively. Data were collected from 122 lactations. The mean 150-day cumulative milk yields of the cows were 1 355, 1 258 and 1 187 kg for the high, medium and low planes of nutrition respectively (P < 0·001). A i-kg increase in calf birth weight was associated with an increase in 150-day cumulative milk yield of 14·7 ± 2·17 kg (P < 0·001). Losses in live weight and condition score were significantly greater for cows given the low plane of nutrition during lactation (P < 0001).

Although there was a significant (P < 0·01) positive correlation between the growth rate of the calves and their dams' nutritional level during the winter there was evidence of compensatory growth at grass, since by the time of weaning in August, the plane of nutrition of the dam during the winter had no significant effect on the weight of the calves.

The experiment demonstrates that energy-deficient beef cows will attempt to maintain milk production at the expense of body reserves and that when supplementary solid food is made available to the suckled calves, their weaning weights are unaffected by the plane of nutrition of the dam during the winter.

A feeding experiment was carried out to assess the effect on performance of three stocking rates in identical-sized pens with pigs growing from 25 to 60 kg live weight. Groups of 8,10 and 12 pigs per pen, 300 pigs in total, were used with lying plus exercise space allowances of 0·61, 0·49 and 0·41 m2 per pig respectively and an additional dunging area in each pen of 2·7 m2. There were no significant differences in rate of growth, food: gain ratio, days to slaughter or carcass backfat measurements. With 12 pigs per pen, the pigs tended to be dirtier and cleaning out of pens was more difficult. It was concluded that under the conditions prevailing a group size of 10 pigs gave the stocking rate of choice.

Three concentrate mixtures were compared in a replicated 3 × 3 Latin square feeding trial with cows in early lactation to evaluate the effect of inclusion of tallow. The concentrates were based on barley and soya bean meal (223 g crude protein per kg dry matter) with either no tallow addition (control group) or with the addition of a protected tallow premix (0·75 spray-dried formaldehyde-treated tallow, 0·25 casein) or an unprotected tallow premix (0·75 spray-dried tallow, 0·25 casein), both added at 138 g/kg. Each concentrate was given at a rate of 8 kg per cow per day and silage was offered ad libitum. The inclusion of unprotected tallow in the concentrate did not significantly change milk yield, fat concentration, lactose concentration or live weight compared with those in the control group. The inclusion of the protected tallow supplement resulted in significantly higher yields of milk (22·9 kg/day), fat (0·95 kg/day) and lactose (1·05 kg/day) compared with those of the control group (21·3 kg/day, 0·79 kg/day, 0·95 kg/day), whilst milk protein concentration was significantly reduced. A digestibility trial with steers showed that, when hay was given with the diets, inclusion of tallow in the concentrate significantly increased the digestible and metabolizable energy concentration of the diets compared with the control diet, but dry matter, energy and fibre digestibility was reduced.

Data were obtained from 233 heifers and 246 steers born in the autumn (September) or spring (March) seasons. The calves were sired by Polled Hereford (British) and Charolais, Chianina, Limousin. Maine- Anjou and Simmental (Continental European) bulls, from Aberdeen Angus (♂ × Holstein ♀ cows. Autumn-born calves weighed more at birth than did spring-born calves ( P < 0·01 ). Season of birth did not affect 205-. 305-. 365-day or slaughter weights. Incidence of dystocia was greater for Maine-Anjousired calves than for Polled Hereford calves (P < 0·05) with the other breeds intermediate. Significant sex differences were observed in practically all live and carcass traits with the exception of Warner- Bratzler tenderness and taste panel evaluations.

There were significant breed effects in which Continental European-sired calves gained weight more rapidly than did Polled Hereford-sired calves (P < 0·01) within each 90-day period, with the exception of 180 to 270 days. Slaughter weight and carcass weight per day of age followed the same trend. At slaughter at a mean age of 416 days, mean live weight of calves from Continental European breeds of sire was 1·075 of that of the Polled Hereford-sired calves. Proportion, weight and gain per day of edible meat in the carcass were greater for calves sired by Continental European bulls (P < 0·01). Although fat thickness and marbling score means were greater for Polled Hereford-sired cattle (P < 0·01), there were no significant differences in taste panel evaluations. There were no important two-way interactions between the main effects (sex, season of birth or sire breed).