Two groups of nine British Friesian cows were fed from about 32 weeks before calving to achieve condition scores at calving of 2·5 (thin) and 4 (fat). For 10 weeks after calving all cows were offered 7 kg hay daily in four feeds, with concentrates given five times daily according to appetite.

During early lactation, the group of fat cows had lower dry-matter intakes and daily milk yields and yielded less milk protein and lactose than the group of thin cows. The mean yield of milk over the whole lactation was 500 kg less in the fat cows but the difference was not significant. The fat cows lost 48 kg body weight and 1·20 units condition score during early lactation compared with 27 kg body weight and 0·52 units condition score in the thin cows. No difference in reproductive performance was found between the two groups but significantly more cases of disease occurred in the fat cows than in the thin cows.

It is concluded that cows that are fat at calving eat less than thin cows, give the same or less milk than thin cows, mobolize more body tissue and lose more weight after calving than thin cows and suffer more disease.

An experiment was performed with two groups of nine British Friesian cows to compare the effect of calving in fat or thin condition on (1) the mobilization and functional activity of subcutaneous adipose tissue, (2) the mobilization of skeletal muscle, (3) the development and resolution of fatty infiltration of the liver and (4) the chemistry and haematology of blood. Sampling was performed at various times during the dry period and subsequent lactation. There were no differences between groups in the amount of adipose tissue mobilized between 4 weeks before and 26 weeks after calving. The lipogenic and lipolytic capacities of isolated adipocytes were also not different between groups at any time although major changes occurred in both over the calving period and during early lactation. Acetate oxidation to carbon dioxide was higher in adipocytes isolated from thin cows particularly after calving. More muscle fibre area was lost in the fat cows compared with the thin cows between 4 weeks before and 4 weeks after calving and the fat cows had greater infiltration of fat in the liver at 1 and 4 weeks after calving than the thin cows. The mean white-cell count was lower and the packed-cell volume was higher in the fat cows than in the thin cows at 1 week after calving. The major differences between groups in blood composition were increased concentrations of copper, non-esterified fatty acids, bilirubin and enzymes such as ornithine carbamyl transferase in the fat cows after calving. These results suggest that fat and thin cows respond differently to the metabolic demands of early lactation and that some of these differences render fat cows more susceptible to disease.

For 25 weeks starting at week 3 post partum autumn-calving dairy cows were offered either a flat rate of concentrates in which all cows received the same daily amount throughout the experiment (F), or a variable rate based on their individual milk yield at 2 weeks post partum, and which was reduced at weeks 10, 15 and 20 of the experiment (V). Two mean amounts of concentrates were compared, 11 kg/day (11) and 7 kg/day (7) and grass silage was available ad libitum. For treatments 11F, 11V, 7F and 7V respectively, mean milk yields were 26·2, 24·5, 21·5 and 21·3 kg/day, mean live-weight changes were +0·18, +0·07, -0·09 and -0·05 kg/day, and mean silage dry-matter intakes were 8·0, 7·1, 9·4 and 9·0 kg/day. Differences between systems of allocation were not significant, but differences between amounts of concentrates offered were significant. Due to the greater milk yield and milk fat concentration of the F system of allocation, milk fat yield was significantly greater than for the V system. The substitution rate of concentrates for silage dry matter was significantly greater during the first 10 weeks of the experiment than during the succeeding 15 weeks. In the residual period (3 weeks indoors and 14 weeks grazing), there were no significant effects on performance. The mean 305-day milk yields for 11F, 11V, 7F and 7V respectively were 6957, 6388, 5862 and 5901 kg.

Two experiments are described in which dairy cows in early lactation were individually offered ad libitum complete diets containing firstly rolled barley, wheat or oats comprising proportionately 0·6 of the total dry matter (DM) and seeondly, whole oats, rolled oats or whole oats soaked in sodium hydroxide comprising proportionately 0·5 of the total DM. Organic-matter (OM) digestibility was measured using chromium III oxide as an external faecal marker and production of milk, milk fat and milk protein were monitored. Rumen digestion rates of each grain type were measured in sacco using non-lactating cows.

In the first experiment, voluntary DM intakes did not differ between diets, OM digestibilities were, in decreasing order, wheat > barley > oats, and faecal starch concentrations were, in decreasing order, barley > wheat > oats. Cows given oats produced the most milk and milk fat while cows given wheat produced the most milk protein. Digested OM was used most efficiently by cows given oats and their greater productivity was attributed partly to higher levels of dietary fibre and lipid.

In the second experiment, cows fed alkali-treated oats had higher (though non-significant) DM intakes and produced the most milk, milk fat and milk protein. Excretion rates of whole grain from cows given treated or untreated whole oats did not differ, but grain weight loss in transit through the gut was higher with the alkali-treated grain. Food intakes and yields of milk and milk solids were similar in cows given either whole untreated or coarsely rolled oats.

As part of a multibreed cattle project for studying genetic variation between breeds, four adult females from each of five breeds of cattle were kept for up to 2 years in a non-pregnant, non-lactating state on each of four feeding levels. The breeds, which were Hereford, Aberdeen Angus, Dexter, British Friesian and Jersey, provided a wide range of genetic potential for body size and milk yield. The feeding levels were arranged to make the weight of lipid in the whole body about 0·05, 0·15, 0·25 and 0·35 times body weight. After an animal had been assigned to a fixed daily intake, its body weight and condition score were monitored over a period varying from 6 to 18 months until an equilibrium body weight and body composition had been established.

For standard adult body weight, Akg, and for an equilibrium body weight, Wkg, and an associated metabolizable energy intake, f/MJ, the maintenance efficiency of a breed adjusted for breed size was defined as Em = W/fA0·21. The ‘lactability’ of a breed, that is, its genetic potential lactation yield, Ykg, adjusted for breed size, was defined as Y = Y/A. The between-breed regression of Em on Y had a coefficient of -0·043 (s.e. 0·007). There was, thus, a highly significant dairy-beef gradient in the equilibrium maintenance efficiency of these non-pregnant, non-lactating adult females.

An expected value for the equilibrium maintenance requirement, of a breed or individual as a function of its lactability was estimated to be:

which implies that the maintenance requirement of dairy breeds is about 0·2 times greater than that of beef breeds, a result which was strongly supported by a literature survey, although mean estimates from feeding trials and fasting trials were anomalous.

Combining this result for milk yield with published results on growth rate, leads to the hypothesis that the greater the maximum gross efficiency of a breed for meat or milk production, the less efficiently it maintains itself, not because of any difference in fasting metabolism, but because of a reduced efficiency of food utilization for maintenance.

Analyses of variance were conducted using two separate random sets of data (25 158 and 24 084 records) on first-lactation, milk-production records of progeny of 69 British Friesian-Holstein proven sires in order to examine the criteria of seasonal grouping for a sire-evaluation model fitting herd-year-season as a fixed effect. Five different seasonal groupings were chosen each comprising two or three seasons with equal or unequal number of months and with different trends in production within season.

The smallest herd-year × month of calving within-season interaction, smallest residual variance, largest effective number of daughters and smallest among-months, within-season variation were considered to be the appropriate criteria of seasonal grouping. None of the groupings examined satisfied all criteria. However, a small herd-year × month within season interaction and all small within-season variation would be desirable if milk records were pre-corrected for the effect of month of calving in sire evaluation, and the effective number of daughters should be large. Given this the grouping currently used in Britain (three seasons: December to March, April to July and August to November) was considered to be appropriate, although a grouping with two seasons: February to July and August to January gave similar results. The regional differences in production were observed to be large, but the region × month-of-calving interaction was small.

Sixty Israeli-Friesian cows were allocated, after calving, to five treatment groups of 12 cows per group according to the concentration and source of crude protein (CP) in the concentrate. Three groups received all their protein from plant sources: a basal control group (BP) was given concentrate containing 92 g CP per kg dry matter (DM), a medium-protein group (MP) was given a diet with soya-bean meal (SBM) added to give a CP concentration of 143 g/kg DM, and a high-protein group (HP) was given a diet with SBM added to give a concentration of 180 g/kg DM. Two groups were given the basal concentrate supplemented with urea (MU) or urea phosphate (MUP) up to approximately the same CP level as the MP group. The only roughage used was vetch-oats hay at a level of 350 g/kg total DM intake. The cows were given the experimental diets ad libitum throughout lactation.

No difference was found between treatments in DM intake (kg/day), mean milk and fat-corrected milk (FCM; 40 g fat per kg) yields (kg/day), milk protein concentration, days from calving to conception or services per conception, during the entire lactation period. However, FCM yields during 60 days after calving were significantly higher for cows given the CP-supplemented diets than for the BP group. The FCM yield of the cows given the HP concentrate was higher than for those given the other concentrate mixtures only during the first 15 days after calving. Milk fat concentration was higher in cows given the BP and HP concentrates than in those given the MP ration, but only a trend in this respect was observed when part of the plant protein was replaced by urea or urea phosphate.

The rate of body-weight loss after calving tended to increase with increase in amount of plant protein in the diet but was highest for the cows given the diets supplemented with non-protein nitrogen. Later in lactation, the body-weights of cows given the MP, HP and MUP diets increased immediately after they reached their lowest weight whilst cows given the BP and MU diets started gaining weight 165 and 120 days after calving, respectively.

Rumen ammonia-N and blood urea-N concentrations (mg/1) for treatments BP, MP, HP, MU and MUP were: 56 and 101; 120 and 226; 143 and 269; 191 and 227; and 179 and 212, respectively. The relationship between rumen ammonia concentrations, blood urea concentrations and CP utilization for the different treatments is discussed. Supplying urea as urea phosphate tended to improve performance by an increase in annual milk and milk protein yields as well as in live-weight gain.

Energy expenditure, food intake and some physiological reactions of Brahman and Brahman × British Friesian cattle working on an inclined treadmill at 33°C were studied. The effect of work at a lower ambient temperature (15°C) and local cooling of the head region while at 33°C were also investigated. Whilst walking up a 6° gradient at 1 m/s, animals expended about four times as much energy as when standing. Heat production during work (W/kgM0·75) was similar in both breeds and was not influenced by the treatments imposed. Crossbred animals showed significantly higher respiration rates and sweating rates than the Brahmans immediately after working for 30 min at 33°C. Food intake and body-weight changes in the crossbreds at 33°C compared with Brahmans provided further evidence that these animals were less tolerant of the conditions. Head cooling during work appeared to reduce depression in food intake associated with work at 33°C in both breeds although it had no effect on physiological changes.

In a multibreed experiment 306 females from 25 British breeds of cattle were given a standard pelleted diet ad libitum. Correlations of food conversion efficiency (FCE) with body weight, weight gain, and food intake were studied over 12-week and longer periods from 12 to 72 weeks of age. Inter-age correlations of FCE with itself and the other traits were also studied over age intervals separated by 12, 24, 36 and 48 weeks. The between-breed correlations were genetic while the within-breed correlations were phenotypic.

Between breeds, FCE measured over the full age range from 12 to 72 weeks appeared to be very highly correlated with FCE measured over the 12-week period between 24 and 36 weeks of age. Correlations of 12 to 72 week FCE with traits not requiring measurement of food intake were much lower, being at most 0·77 for weight gain, 0·73 for weight gain per unit body weight and 0·57 for body weight. The pattern of correlations implied that over constant age ranges the larger faster-growing breeds with high intakes tended to be more efficient; however, these correlations were generated primarily at early ages between 12 and 36 weeks and FCE at later ages could not be predicted from other traits measured at earlier ages. Nevertheless, between-breed selection to improve FCE by indirect selection on body weight and weight gain could be effective but there would appear to be no advantage in waiting beyond 1 year of age.

Within breeds, correlations of 12 to 72 week FCE with FCE measured over 12-week periods increased with age from 0·24 to 0·61. Correlations of FCE with weight gain in the same 12-week periods were quite high (0·49 to 0·89) and those with weight gain per unit weight were invaribly higher (0·68 to 0·90). However, as a predictor of FCE in any subsequent period, weight gain per unit body weight was poor and weight gain of no value whatsoever. There was no strong association of FCE with body weight.

Two groups of 19 Border Leicester cf × Scottish Blackface 9 ewes were fed so that ewes of one group were in a very high level of body condition at mating (mean score 3·35) and had a high level of intake. Ewes of the second group were in moderately high condition (mean score 2·74) and were given a live-weight maintenance ration. Ewes in the high group had a higher ovulation rate than those of the moderate group (3·36 v. 2·33) but a lower number of embryos per ewe mated (1·16 v. 1·42). Mean follicle stimulating hormone profiles were similar for ewes of the two groups during the luteal and follicular phases of the cycle before mating and during the subsequent oestrus. Mean prolactin concentrations were higher in ewes of the high group during the follicular phase and oestrus but not during the luteal phase. Mean luteinizing hormone (LH) concentrations were higher in ewes of the high group during the follicular phase and oestrus but not during the luteal phase. Mean LH concentrations were similar for the two groups at all times but the frequency of LH pulses was higher in the high group during the follicular phase.

Ewes that were not pregnant at slaughter had abnormal progesterone profiles following mating, abnormal pre-ovulatory LH surges or failed to show oestrus. These abnormalities were not related to gonadotrophin profiles prior to oestrus.

Twenty-eight Border Leicester ♂ × Scottish Blackface ♀ wether lambs aged 47 days and weighing 17 kg on average were allocated to be sham-implanted controls (group C) or implanted with trenbolone acetate (TBA) combined with oestradiol-17β (OE) as follows: 17·5 mg TBA + 2·5 mg OE (group TO1); 35 mg TBA + 5 mg OE (TO2); 52·5 mg TBA + 7·5 mg OE (TO3). The lambs were offered ad libitum a diet containing (per kg dry matter) an estimated 12·5 MJ metabolizable energy and 0·16 kg crude protein. They were slaughtered 60 days following implantation.

On average hormonal treatment resulted in significant increases in (a) live-weight gain, food intake and gut fill, (b) proportions of perinephric and retroperitoneal fat in empty body, (c) carcass lean proportion, and (d) proportion of lean in shoulder and rib joints. Variable changes in the weights of m. semitendinosus, m. gastrocnemius and m. supraspinatus were recorded.

Hormonal treatment, on average resulted in significant reductions in (a) killing-out proportion, (b) proportions of total fat and subcutaneous fat in carcass and (c) proportions of fat in the shoulder, rib and hind leg joints. Treated lambs had smaller thymus glands but larger accessory vesicular glands. Penile tissue was also increased in treated lambs. The proportional differences in live-weight gain and carcass fat content were 0·15 and 0·12 respectively.

Differences in dose level had little effect on growth and carcass characteristics.

To evaluate passive and active methods for rewarming hypothermic lambs, the rectal temperature of 19 neonatal lambs (4·9 (s.e. 0·34) kg) was reduced to 35°C by cold water immersion. Metabolic responses and change in rectal temperature were monitored as the hypothermic lambs recovered with added insulation in a 20 to 25°C air environment, or with thermal assistance provided by an infrared heat lamp, or through immersion in 38°C water. During the first 12 min of rewarming, the rise in rectal temperature in all treatment groups was linear, however it was more rapid with the lambs immersed in warm water (0·26°C/min; P < 0·05) as compared with the insulated lambs (0·21°C/min) and the lambs rewarmed with a heat lamp (0·22°C/min). During this 12-min period, the insulated lambs produced metabolic heat more rapidly than did the warm-water lambs, 13·6 v. 11·1 (s.e. 0·67) W/kg, respectively (P < 0·05). These data indicate that there was a substantial influx of heat which contributed to the increase in body temperature of the lambs immersed in warm water. Stabilization of rectal temperature occurred after 18 to 20 min in all treatment groups. The lambs recovered in all treatment groups, in addition, no clinical problems were observed in any of the lambs during the tests or subsequently when they were returned to their dams.

Sixty Landrace × Large White piglets were removed from their mothers at birth and allocated to one of five treatments. Treatment A piglets were controls and did not receive any form of passive immunity after birth. Treatment B piglets were given by intraperitoneal injection 20 ml equine serum derived from horses previously hyperimmunized against porcine pathogens. Treatment C piglets received the same equine serum given orally. Treatment D piglets were given 20 ml pooled pig plasma by intraperitoneal injection. Treatment E piglets received the same pig plasma given orally. All piglets were reared to 2 weeks of age in an artificial-rearing device and were automatically fed a liquid diet every hour. Overall survival to 2 weeks of age was 90% (54/60) but treatment did not affect survival. The overall survival after 6 weeks of age was 47% (22/47) deaths being due to a variety of systemic disorders. Overall daily gain to 2 weeks of age was 143 g/day and the food/gain ratio was 0·88. Treatment did not affect performance. The concentrations of immunoglobulin class G (IgG) in the blood were measured at 42, 49 and 56 days of age. There were no differences between the treatment groups in IgG concentrations.

The digestive ability of growing pigs and large adult sows was compared in digestibility experiments with 26 foodstuffs and diets. In all cases, the sows showed superior digestibility of nutrients. On average, the sows digested 150 g more crude protein, 100 g more crude fat, 300 g more crude fibre per kg diet and proportionately 0·09 more gross energy than the young animals. The superior ability of the sows to digest gross energy was negatively correlated with the soluble carbohydrate and gross energy concentration of the food. A close linear relationship between digestibility in growing pigs and that in sows was found, making it possible to apply digestibility data for growing pigs in practical diet formulation for sows.

Circadian variation in the composition of digesta was examined in pigs fitted with replaceable T-cannulas in the proximal duodenum and terminal ileum. The pigs were fed twice daily with a cereal-based diet containing Cr2O3, as a marker. Digesta were collected hourly for 16 h following morning feeding (pig live weight (LW) 25 and 65 kg) or as a 12-h composite collection (pig LW 45 kg), and analysed for pH, dry matter (DM), ash, crude fat, crude protein, starch, neutral-detergent fibre (NDF) and Cr2O3,.

No statistically significant differences were found in the composition of digesta from pigs weighing 25 or 65 kg LW. Calculated relative to Cr2O3, recoveries in 12-h composite samples of duodenal and (ileal) digesta were 1·19 (0·34) for DM, 1·28 (0·31) for crude protein, 0·97 (0·05) for starch and 0·93 (0·79) for NDF. Composition of both duodenal and ileal digesta varied considerably during the sampling period and was particularly influenced by giving food. Between-hour coefficients of variation for the samples taken hourly were, in general, greater at the duodenum (mean 017) than at the ileum (mean 0·11), while mean within-hour (between pigs) coefficients of variation (0·19 and 0·18, respectively) were greater than those between hours. The Cr2O3 marker generally followed the flow of dietary matter through the gastrointestinal tract, although there was an indication of a partial separation of NDF from other dietary components in the stomach. Composition of the 12-h composite samples of digesta did not differ from that of the mean of the samples taken hourly for 16 h.

One hundred and twenty pigs were used in a 3 × 8 factorial design. The factors were sex, 40 trios of littermate boars, castrated males and gilts, and dietary lysine, eight concentrations from 7×5 to 14×5 g/kg diet with 1 g/kg diet intervals of lysine with corresponding crude protein (CP) concentrations from 114 to 226 g/kg diet. Increases in dietary lysine were associated with concomitant increases in the other essential amino acids so as to provide an ideal protein. All diets had similar digestible energy values (13·65 MJ/kg). Pigs were fed once daily on a restricted scale from 25 to 55 kg live weight. For growth and carcass characteristics there was a range of linear response followed by a plateau. The inflexion points of dietary lysine for growth characteristics were at 11·1, 10·2 and 10·9 g/kg diet (171, 157 and 168 g CP per kg diet) together with daily intakes of 18·0, 16·7 and 17·6 g (daily intake of 277, 257 and 271 g CP) for boars, castrated males and gilts respectively. The equivalent points for carcass characteristics were 10·4, 9·7 and 10·1 g/kg (160, 149 and 156 g CP per kg diet) with daily intakes of 16·9, 15·9 and 16·4 g lysine (daily intakes of 260, 245 and 252 g CP). Blood urea data gave good support for these observations.

The response to dietary lysine when provided as part of an ideal protein was examined in pigs over the range of live weight from 50 to 90 kg. Ninety-six pigs, 32 trios of littermate boars, castrated males and gilts were allocated to eight diets with lysine concentrations of 5·6, 6·2, 7·3, 8·3, 9·3, 10·3, 11·4 and 12·4 g/kg diet and corresponding concentrations of crude protein (CP) from 90 to 186 g/kg diet (all having a digestible energy of 13·38 MJ/kg). Pigs were given food on a restricted scale once daily. With increasing lysine concentration, there was a linear response (followed by a plateau) for growth and carcass characteristics up to dietary lysine concentrations of 91, 7·2 and 8·4 g/kg diet and CP concentrations of 142, 116 and 132 g/kg diet with daily lysine intakes of 22·9, 18·6 and 21·2 g and CP intakes of 357, 290 and 331 g for boars, castrated males and gilts respectively.

Present day sows, particularly young sows, have smaller fat reserves than they did 10 to 20 years ago (Whittemore, Franklin and Pearce, 1980). Consequently, changes in the sows' body reserves during pregnancy and lactation have become much more critical in evaluating various nutritional strategies. The interpretation of many experiments designed ot investigate the effects of nutrition of the sow would be enhanced if changes in the body composition of the animal could be determined.

The two most widely adopted methods for measurement of milk production in sheep suckling lambs, the lamb-weight increment technique and milking-out following administration of oxytocin, give estimates which differ proportionately between 0·05 and 0·28 especially in early lactation (Doney, Peart, Smith and Louda, 1979). It is not easy to determine which method gives the most accurate estimate of milk production in suckling ewes. It is important, however, to understand the circumstances in which discrepancies between methods may occur and their magnitude. This note provides evidence that such discrepancies may vary with nutritional status of the ewe.

Mid-Pregnancy nutrition has been shown to have both positive and negative effects on lamb birth weight in primiparous Scottish Blackface ewes. The direction of the effect depends on the level of body condition at mating, being negative in ewes in high body condition (Russel, Foot, White and Davies, 1981). In the same study, it was argued that the effect in younger ewes could be due to their greater sensitivity to both under- and over-nutrition during the earlier to mid stages of their first pregnancy than is evident in older ewes. Russel et al. (1981) also suggested that the level of mid-pregnancy nutrition is likely to have effects on other aspects of production such as embryonic loss, foetal mortality and even ewe mortality.