Forty-four British Friesian, first-lactation heifers were used in a randomized block experiment over a 2-year period to examine the effects of two patterns of concentrate allocation during the post-calving, indoor feeding period. The animals, mean calving date 17 October (s.d. 15 days), were offered concentrates either on a high-low system consisting of 80kg/day for the first 90 days of lactation and thereafter 5-4kg/day, or on a uniform system in which 6-8 kg/day was offered from calving until going to pasture (mean of 182 days). In addition, all animals received access ad libitum to grass silage, with a mean dry-matter content and digestible organic matter in the dry matter value of 218 and 679g/kg respectively. During the 1st year all 22 animals were housed as a single group, but in the 2nd year the animals were housed in individual stalls and silage intakes recorded for all replicates. In each year all animals grazed as a single group at pasture without supplementary concentrates.

Total concentrates consumed were 1163 and 1187 (s.e. 19·4)kg for the high-low and uniform treatments respectively. Although the animals on the high-low treatment reached a higher peak milk yield, there were no significant differences in milk yield over the winter period, 3257 and 3311 (s.e. 41·5) kg, or total lactation, 4862 and 4886 (s.e. 80·6)kg, for the high-low and uniform treatments respectively. The animals on the high-low treatment, however, were significantly lighter in body weight at the end of the winter but there was no difference between treatments at the end of lactation. Milk composition data are also presented.

Two experiments have been carried out to examine the interaction between animal size and the response in animal performance to an increase in the digestibility of grass silage. In experiment 1, grass silages harvested during July and August after regrowth intervals of 43 and 85 days were offered ad libitum both unsupplemented and supplemented with 2 kg of concentrates per head per day to British Friesian steers of (±s.e.) 170±1·9, 300±2·9 and 420±3·6 kg initial live weight. Earlier cutting did not affect silage dry-matter intake or live-weight gain but increased carcass gain by 0·12kg/day (P<0·01).

In experiment 2, early-cut grass silage, made from two regrowths of perennial ryegrass, which were harvested during July and August after regrowth intervals of 43 and 48 days, and late-cut silage, made from a single regrowth, which was harvested in August after a regrowth interval of 90 days, were offered ad libitum to 84 Hereford-cross steers of (±s.e.) 170±3·4, 300±4·4 and 420±5|·2kg initial live weight. Earlier cutting increased silage dry-matter intake by 340 g/kg, live-weight gain by 0·23 kg/day and carcass gain by 0·18 kg/day (P<0·001). It i s concluded that increasing the digestibility of grass silage by cutting grass at an earlier stage of growth is likely to produce a substantial increase in the daily carcass gain of beef cattle and that the response to higher digestibility is as great with mature cattle as with young, growing animals.

Carcass characteristics of purebred British Friesian steers and crossbred steers by eight sire breeds out of British Friesian dams, in 16-month and 24-month beef production systems, were compared. Sire breeds included Charolais, Simmental and the main traditional British beef breeds. A total of 579 cattle were involved.

The cattle were slaughtered at a fixed level of fatness and the carcasses evaluated using a standardized commercial cutting technique. Data were adjusted to equal carcass subcutaneous fat concentration.

Sire breed differences were similar in both feeding systems. Charolais crosses killed-out best and Aberdeen- Angus and Devon crosses poorest; the range was 25 g/kg live weight.

Significant differences were recorded between breeds in the proportion of saleable meat in the carcass (P<0·001): Charolais, Sussex and Aberdeen-Angus crosses had the highest values, on average being 15g/kg carcass weight better than purebred Friesians. Breed differences were detected in the proportion of total saleable meat occurring in the higher-priced joints, Simmental and Charolais crosses ranking highest, but the range across sire breeds was only 10 g/kg carcass weight. There were important differences between sire breeds in rate of meat weight gain that were related to mature size.

Purebred Friesians were less efficient than either Charolais or Hereford crosses in converting food into meat in the 24-month system. Friesians also had the lowest efficiency and Hereford crosses the highest efficiency in the 16-month system, although the differences were not statistically significant.

In each of 2 years, two groups of 25 British Friesian heifers were given, respectively, a moderate- and a low-energy diet for a 12-week period. Mean live-weight gains of 0·25 kg/day and 0·45 kg/day were recorded for the moderate-energy diet, and losses of 0·22 kg/day and 013 kg/day for the low-energy diet. Heifers were inseminated artificially at oestrus at approximately the mid-point of the 12-week period, this oestrus being the next observed after synchronized oestrus, which followed luteolysis induced by cloprostenol injections. With few exceptions, heifers that gained weight were in good or medium condition at insemination and those that lost weight were in medium or poor condition.

Highest pregnancy rate (0·78) was recorded for heifers that gained weight and were in medium condition at insemination. For heifers losing weight, pregnancy rate dropped to 0·46 (P < 0·05) due to reproductive failure occurring before the 25th day after insemination. Only in heifers in poor body condition was there a significantly higher proportion failing to ovulate normally (P < 0·001). Among heifers gaining weight, those failing to become pregnant to the first insemination were approximately lOOg/kg heavier than the pregnant ones (P<0·05).

Irrespective of gain or loss of weight, and of body condition at insemination, embryo losses did not occur later than the 25th day after insemination, except that five heifers that showed oestrus when pregnant (according to plasma progesterone levels) and were reinseminated then showed evidence of embryo loss.

Twenty-four castrate male cattle were used in two nutritional balance and slaughter experiments to measure the effects of two implantations with 300 mg trenbolone acetate and 36 mg resorcylic acid lactone over the live-weight range 250 to 400 kg. Control and implanted animals were pair-fed barley-based diets of differing protein concentration in the first experiment and the lower protein diet at two levels of feeding in the second experiment.

Daily live-weight gain and nitrogen retention were significantly increased by implantation in both experiments. The carcasses of implanted animals contained significantly more lean meat and a higher proportion of meat in the forequarter. The edible portion of these carcasses contained significantly more protein and water and less fat.

Live-weight gain and carcass composition were not influenced by dietary protein intake. Increased feeding level improved live-weight gain, suggesting that a higher metabolizable energy intake would give an increased response to implantation.

In each of 4 years, 24 autumn-calving, single-suckling Aberdeen Angus × Friesian cows with Charolais cross calves were subjected to different winter feeding regimes and to a range of weaning dates, and the effect on cow and calf food intake and performance was measured. Giving 257 kg concentrate dry matter to cows on an ad libitum silage diet over winter increased calf and cow weights in the following September by 17·8 and 11·7 kg respectively. Weaning after 4 months of lactation resulted in a net saving in winter forage requirements when compared with weaning in March/April but a high input of concentrate was necessary to achieve satisfactory calf performance. Weaning in July increased calf weights in August/September by 22·1 kg and reduced cow weights by 22·3 kg compared with weaning in March/April. Later weaning at pasture might be preferable, producing heavier calves, provided that cow weights can be restored at pasture.

Four silages were prepared from whole crop maize, each receiving additives of 21 1 formic acid per t fresh crop, and 0, 14, 27 or 53 g formaldehyde per kg crude protein in the crop. These silages, together with 19·6 g urea per kg dry matter, were offered ad libitum for 83 days to 60 British Friesian steer calves, initially 99 kg live weight, either alone or with groundnut or fish meal to raise the dietary crude protein content by 27 g/kg dry matter.

Formaldehyde treatment restricted silage fermentation, increased silage and dry-matter intake and live-weight gain, but reduced digestibility, so digestible organic matter and digestible energy intakes were unaffected. Much of the increase in live-weight gain appeared to be due to an increase in gut fill, as carcass weight was not significantly affected by formaldehyde treatment. There was no improvement in the utilization of dietary nitrogen, but there was some evidence that formaldehyde treatment may have increased the proportion of muscle in the carcass.

Supplementation with protein improved intake, nitrogen retention, feed conversion ratio, live-weight gain and carcass weight. The improvement in intake and food conversion ratio occurred mainly on the control silage, there being little effect on the formaldehyde-treated silages. Fish meal supplementation increased the digestibility of organic matter, cellulose and energy, and was more effective in improving food conversion ratio than groundnut meal. There were no significant differences between diets in the proportion of dietary nitrogen retained.

It was concluded that the scope for the use of formaldehyde, when ensiling maize for use in diets for young calves, appears to be limited.

Effects on animal health and productivity of offering diets composed wholly or partly of kale to Hereford × Friesian steers were examined in two growth trials and a digestibility trial. Rates of daily gain (kg), daily dry-matter intake (kg) and coefficients of dry-matter digestibility by 24 steers offered proportions of 0·50 or 0·75 kale with rolled barley or 100 kale were respectively 1·05, 7·5, 0·76; 0·72, 5·8, 0·72; and 0·48, 5·3, 0·70. Of 48 steers given 0·25 or 0·50 kale with rolled barley, fodderbeet or swede turnips, the food intakes and daily gains of those offered barley were greatest on the higher proportion of kale whereas with fodderbeet and turnips the food intakes and gains were higher (P<005 and P<0·01) respectively on the lower proportion of kale. Although daily intakes of S-methylcysteine sulphoxide were high, reaching 0·25 and 0·33 g per kg body weight in trials 1 and 2 respectively, and moderate changes in blood metabolism occurred, there were no cases of haemolytic anaemia. Steers given only kale produced the poorest daily live-weight gain and the results suggested that the inclusion of kale should be limited to 0·50 of the total diet.

Computer simulation was used to measure the effects of breeding management efficiency in block calving dairy herds and in those with a long mating season of 9 months. In particular, the effects of varying levels of oestrus detection and conception rates were assessed, and the product of these two parameters defined as the fertility factor. As the fertility factor increases from 20 to 50, where the mating season extends to 9 months, the mean calving index for the herd decreased linearly from 393·5 to 373·6 days and the culling rate for failure to conceive declines in curvilinear fashion from 0·196 to 0·006. Concurrent with the decrease in calving index, mean annual milk yield and margin over purchased food increase, with the herd commencing calving in January showing a more marked response than the herd commencing calving in October. When overall replacement rate is also taken into account, the margin over purchased food net of herd depreciation per cow, at 1979/80 prices, changes from £270·7 to £315·2 in the January herd compared with £275·9 to £315·8 in the October herd. For each day change in calving index associated with alteration in fertility factor, there is a change of £2·24 for the January herd and £2·01 for the October herd in margin over purchased food net of herd depreciation.

In the block calving herd, increases in fertility factor are reflected mainly in changes in culling rate for failure to conceive from 0·292 to 0·033, and not in margin over purchased food.

Samples of cooked muscle of Swamp buffalo, Hereford, Angus, Friesian and Charolais cross steers were sheared and scored by a taste panel for tenderness, flavour, juiciness and palatability. The cattle were given commercial pellets from 9 months of age to slaughter at 12,15 and 18 months. The buffaloes were fed one of four regimens: all pellets, all hay, 3/4 pellets and 1/4 hay or 1/4 pellets and 3/4 hay from 13 to 22 months of age to slaughter at 20 to 34 months.

There was little difference between the buffaloes and the cattle in shear-force or taste panel scores. Age at slaughter had no significant effect on the quality traits measured in either the buffaloes or the cattle. The feeding regime did not influence the tenderness, flavour or palatability of buffalo muscle but the high pellet diets increased juiciness.

Shear-force was not influenced by rectal or muscle temperatures, muscle pH, carcass weight or fatness in the buffaloes but fatness reduced shear-force in cattle m. longissimus.

Buffalo intramuscular fat increased with age and carcass fatness but had no effect on shear-force or taste panel score.

The experiment assessed the effects on performance from calving to the 20th week of lactation of milking cows three times daily (3 × ) compared to milking twice daily (2 × ). After 20 weeks all cows were milked 2 ×. Each treatment consisted of 18 cows and 11 heifers. The mid-calving date was 21 September 1979.

Complete diets of the same composition were offered separately to each group in quantities equivalent to 1040 g/kg of their previous intake. The diet for the first 18 weeks of lactation was estimated to have an energy concentration within the range 11·0 to 11·3 MJ metabolizable energy per kg dry matter. After 18 weeks, the diet was reformulated to reduce the energy concentration to 10·3 MJ per kg dry matter. Total food intakes for the 20 weeks of treatment were 2352 kg dry matter (3 ×) and 2241 kg dry matter (2 ×). From 8 April 1980 the cows were turned out to grass to complete their lactations.

During the 20 weeks the mean daily milk yields of heifers were 19·3kg (3×) and 171kg (2×) (P<005). Cow yields were 28·4 (3×) and 23·9 kg (2×) (P< 0·001) during the same period. After 3× daily milking ceased, there were some positive carry-over effects on milk yield and food intake.

Lactation yields from heifers were 4881 (3 ×) and 4498 kg (2×), whilst for cows the equivalent yields were 6485 (3 ×) and 5694 kg (2 ×) (P<0·01). There were no significant differences in milk quality. At 20 weeks after calving the cows milked 3 × daily had gained less weight, but by 44 weeks from calving the weight gains were similar at 42 (3 ×) and 45 kg (2 ×).

Body weights at birth, 90 days, 180 days and 1 year of age were analysed in 620 calves, the offspring of sires of the Friesian, Jersey and Simmental breeds, and of dams of three indigenous zebu breeds, namely Barka, Boran and Horro, at four diverse locations in Ethiopia.

Breed of sire, breed of dam and location all significantly affected weight. Progeny of Friesian and Simmental sires were similar in weight but both were heavier than the progeny of Jersey sires, their weight being, respectively, 25·0,24·9 and 21·2 kg at birth; 88·0, 84·6 and 74·9 kg at 90 days; 151·7, 150·6 and 135·4 kg at weaning at 180 days; and 220·6,224·8 and 193·3 kg at 365 days. Barka crosses were heaviest and Horro lightest. Mean weight for progeny from Barka, Boran and Horro dams was, respectively, 24·0, 24·6 and 22·5 kg at birth; 85·2, 83·8 and 78·5 kg at 90 days; 149·6, 148·0 and 140·1 kg at 180 days; and 233·7, 208·1 and 196/9 kg at 365 days. Dam breed × location interaction was significant except at birth, and sire breed × dam breed and sire breed × location interaction were significant at 90 days of age. In a comparison of Friesian and Simmental, the Friesian sires interacted relatively more favourably with the Barka dams, and the Simmental with the Boran. The Jersey was also relatively better with the Boran crosses, compared with either the Barka or the Horro crosses. By 1 year of age Jersey crosses were at a relative (but insignificant) advantage in body weight at the hottest location.

Two foods, distillers' wet draff and draff plus pot ale syrup, containing 207 and 256 g crude protein per kg dry matter respectively, were given as sole food at the maintenance level to four adult wether sheep. Two of the sheep were given draff and two draff plus syrup for a 28-day period; the treatments were then changed over for a second period. The copper contents of the foods were 17 and 30mg/kg dry matter for the draff and draff plus syrup respectively. Sheep are particularly susceptible to copper and care should be taken when feeding such by-products, but during these short-term trials there was no evidence of copper poisoning. Energy losses in the faeces and urine were measured for all sheep, and methane losses were measured in closed-circuit respiration chambers for two sheep on each treatment. The metabolizable energy values of the foods were 10·8 (s.e. 0·15) and 12·5 (s.e. 0·15) MJ/kg dry matter for the draff and draff plus syrup respectively. The proportions of gross energy intake lost as methane were 0·029 for the draff and 0·042 for the draff plus syrup; these were much lower than the values predicted by the commonly used equation.

One hundred and sixty Friesian heifers were allocated to two groups 8 or 9 weeks before artificial insemination and group-fed to gain live weight at 0·8 or 0·3 kg/day. Half the heifers of each group were moved to the other group 2 weeks before first insemination. All heifers received two intramuscular injections of prostaglandin (cloprostenol) 11 days apart, followed by inseminations at 72 and 96 h after the second injection.

The feeding regimes applied did not significantly affect the fertility of groups of heifers as measured by pregnancy rates to fixed-time or all inseminations. There were significant differences between pregnant and nonpregnant heifers within groups where changes in feeding levels were imposed (P<0·1 to P<0·01). Heifers whose growth rate was most severely checked, or whose body condition deteriorated relative to others in the group, were less fertile. For heifers changed from the low to the high plane of nutrition, those experiencing the greater increase in growth rate and body condition were more fertile than others.

No relationship was found between live-weight change, plasma glucose concentrations and fertility. In a second trial 158 Friesian heifers received two injections of cloprostenol 11 days apart, followed by inseminations at 72 and 96 h after the second injection. After the fixed-time inseminations the heifers were divided into two groups and were group-fed to gain live weight at 0·8 and 04 kg per head per day. Although the mean live-weight gain of the high group was significantly higher than that of the lower group (P<0·001), the overall pregnancy rates were not significantly different.

Two experiments have been conducted to compare wilted, formic acid-treated red clover and unwilted, formic acid-treated grass silages for beef production, and to examine the effects of digestibility of red clover and level of concentrate supplementation on food intake and animal performance.

In experiment 1, 12 groups of four British Friesian steers (initial live weight 229 kg) were given red clover silages of high and low dry-matter digestibility (0·70 and 0·60 respectively) and grass silage (0·71) ad libitum for a period of 11 weeks. Silage dry-matter intake and live-weight gain for the steers given red clover of high digestibility, red clover of low digestibility and grass silages were 7·75, 0·89; 6·91, 0·69; and 5·59, 0·59 kg/day respectively.

In experiment 2, 12 groups of four British Friesian steers (initial live weight 332 kg) were given red clover silage with a dry-matter digestibility of 0·63 and grass silage with a value of 0·76 ad libitum, either unsupplemented or supplemented, with 2 kg/day of fortified barley per head for a period of 19 weeks. Silage dry-matter intake, live-weight gain and carcass gain were 8·52, 0·63, 0·32 and 6·98, 0·78, 0·43 kg/day for the unsupplemented and supplemented red clover silage treatments, and 6·82, 0·59, 0·31 and 5·75, 0·75, 0·44 kg/day for the unsupplemented and supplemented grass silage treatments respectively. The performance of the cattle offered red clover silage was similar to that of cattle offered grass silage of 0·12 higher digestibility, largely as the result of higher dry matter intakes achieved on red clover silage.

The effects of pregnancy and lactation on growth were investigated in Ayrshire cattle, from data on 12 linear body measurements at 3-monthly intervals up to 4 years of age. In all, 9 888 sets of 12 measurements were obtained. There were 675 first and 518 second calvings.

When expressed as a percentage of the size of animals of the same age but in a non-pregnant, non-lactating state, the total set-back to normal growth due to pregancy and lactation ranged from 2% in withers height to 18% in forerib width in heifers, and from 1% to 3% for the same characters in cows.

All 12 measurements were affected significantly by first pregnancy (including parturition), the average retardation being 3%. For several measurements, a check to growth during pregnancy was largely obscured by progressive distention of the body, especially in measurements of width, until parturition had occurred. Thus a retardation of 9% in forerib width became apparent only after calving.

First lactation affected significantly most measurements, especially the later-maturing six, which were set-back in their normal growth over the lactation period by 3% to 9%. Thus, there was effectively zero- growth in width at forerib and only one-sixth of normal growth in foregirth, whilst growth rate in width at pins and hooks was approximately halved by lactation.

Calving at an earlier than average age affected growth adversely and thereby involved some increased risk of calving difficulties.

The time from birth to first suckling was recorded for 161 dairy calves. Of these calves, 0·32 failed to suckle within the first 6h of life. The most important factor determining the time to first suckling was the udder conformation of the dam but delays were also attributable to abnormal maternal behaviour, especially in heifers, and poor calf vigour, especially after difficult calvings. Delayed suckling was more common as the parity of the dam increased. Heifers' calves that were sired by a Sussex bull stood up earlier and suckled earlier than those sired by a Friesian bull. Offspring of different Friesian sires differed in the time to first standing and suckling. Delayed suckling became more common as the calving season progressed. Calves born within a group of animals suckled no later than calves born in individual calving pens but 0·15 of those calves first suckled from a cow other than their dam.

In three experiments the effects of giving Hereford × Friesian cows 61 to 64 MJ/day of metabolizable energy in the last 8 weeks of pregnancy, followed by either 49 to 56 (L) or 85 to 100 (H) MJ/day for the first 8 weeks of lactation, were determined. A further comparison was made in experiment 3, in which energy intakes were restricted to 46 and 64 MJ/day (M) in the two periods respectively. The L and M groups had a similar average weight loss of approximately 55 kg over winter whereas the H groups maintained their weight. The L and M treatments had a negligible effect on milk production at 3 weeks post calving but they caused a significant depression at 6 weeks in experiments 2 and 3. Milk energy and protein concentrations were reduced in all three experiments. Calf growth was similar on both treatments in experiment 1 but was 9 to 13% lower in experiments 2 and 3 for the L and M groups compared with the H group. Reproductive performance was not significantly affected. There was a substantial increase in milk production for all groups on turnout to grazing. This was greater for the L and M groups so that their summer milk production was almost equal to that of the H group. Cows from L and M groups gained more weight at pasture. By the end of the trials cows and calves from all treatments had similar weights except in experiment 3, when cows from the L and M treatments were still lighter than those from the H treatment.

Ninety-six Hereford steer calves that weighed 249(s.e.4·7)kg were allocated randomly to four treatments of 24 steers each in a randomized complete block design with four blocks. The steers grazed dormant native range forage that contained 41 to 60 g of crude protein per kg dry matter during the 120-day wintering trial and were given 0·91 kg of supplement per head per day. The supplements used contained 175 or 350 g crude protein per kg dry matter and 0 or 165 mg monensin per kg supplement; a factorial arrangement of treatments was used in allocating the supplements. Weight gains of steers given the high-protein supplements were greater than those on the low-protein supplements during periods 1(0 to 61 days) and 2 (62 to 120 days), and over the total trial (P < 0·01). Monensin increased weight gains during period 1 and the total trial (P < 0·01). The protein level × monensin interaction was not significant for either period or the total trial (P > 0·15). The results indicate that inclusion of monensin in protein supplements for growing cattle grazed on low-quality dormant native forage may allow some reduction in protein content of the supplement.

Two trials were conducted at the BOCM Silcock Development Unit at Stoke Mandeville. The first trial evaluated the response on doe and progeny, from mating to 8 weeks after parturition, of rabbit compound diets containing 0, 100, 200 and 300 g sodium hydroxide-treated straw per kg. Performance data showed no detrimental effect of inclusion levels up to 300 g sodium hydroxide-treated straw per kg despite its high sodium concentration.

A second trial was made to ascertain whether these findings were due to the treated straw itself or to increasing sodium concentrations. A standard rabbit compound diet containing 2·5 g sodium per kg was compared with diets containing either 5·0 or 10·0 g sodium per kg, and with experimental compound diets containing either 80 g sodium hydroxide-treated straw or 80 g untreated straw per kg and both containing 2·5 g sodium per kg. Peak food conversion was estimated to occur at a dietary sodium concentration of 4·6g/kg, although the slope of the dose response curve was not statistically significant at the P ≤ level.

The results indicate that compound diets containing up to 80 to lOOg sodium hydroxide-treated straw per kg may be fed to rabbits and that inclusion of levels of up to 300 g sodium hydroxide-treated straw per kg are not detrimental to performance. On the other hand, an inclusion of 80 g untreated ground straw per kg in compound diets for rabbits had a growth-depressing effect.