A randomized block experiment using 108 British Friesian cows was conducted over a 2-year period to assess the effects of level and pattern of concentrate allocation during early lactation on the performance of cows which calve during January and February. The three concentrate levels were 280 (L1), 405 (L2) and 530 (L3) kg during a 74-day post-calving period, and the two systems of allocation were either a uniform daily allowance (uniform system) or a high input for the first 4 weeks after calving followed by a low input (high/low system). The animals had ad libitum access to medium-quality grass silage during the indoor period and in both years were turned out to pasture on 9 April. At pasture they were grazed rotationally in treatment groups at a stocking rate ranging from 6·4 cows ha-1 in the early-grazing season to 4·9 cows ha-1 in the late-grazing season.

Mean milk outputs for the indoor feeding period were: high/low system 1577 (L1), 1705 (L2) and 1764 (L3), uniform system 1583 (L1), 1676 (L2) and 1783 (L3) ±33·8 kg; and for the total lactation were high/low system 4625 (L1), 4906 (L2) and 5148 (L3), uniform system 4830 (L1), 4933 (L2) an d 5301 (L3) ±118·9 kg.There was no significant interaction between level and system of concentrate allocation. Feed intake, milk composition, animal live weight and body-condition data are also presented.

Experiments carried out to determine the amino acid requirement in growing animals are often based on the premise that the amino acid composition of body protein is constant. However, there are indications that this assumption may not be correct. The objective of this study was to test the effect of feeding piglets a diet deficient or not in total sulfur amino acids (TSAA; Met + Cys) on nitrogen retention and amino acid composition of proteins in different body compartments. Six blocks of three pigs each were used in a combined comparative slaughter and nitrogen balance study. One piglet in each block was slaughtered at 42 days of age, whereas the other piglets received a diet deficient or not in TSAA for 19 days and were slaughtered thereafter. Two diets were formulated to provide either 0.20% Met and 0.45% TSAA (on a standardized ileal digestible basis) or 0.46% Met and 0.70% TSAA. Diets were offered approximately 25% below ad libitum intake. At slaughter, the whole animal was divided into carcass, blood, intestines, liver, and the combined head, tail, feet and other organs (HFTO), which were analyzed for nitrogen and amino acid contents. Samples of the longissimus muscle (LM) were analyzed for myosin heavy chain (MyHC) and actin contents. Nitrogen retention was 20% lower in piglets receiving the TSAA-deficient diet (P < 0.01). In these piglets, the nitrogen content in tissue gain was lower in the empty body, carcass, LM and blood (P < 0.05) or tended to be lower in HFTO (P < 0.10), but was not different in the intestines and liver. The Met content in retained protein was lower in the empty body, LM and blood (P < 0.05), and tended to be lower in the carcass (P < 0.10). The Cys content was lower in LM, but higher in blood of piglets receiving the TSAA-deficient diet (P < 0.05). Skeletal muscle appeared to be affected most by the TSAA deficiency. In LM, the Met content in retained protein was reduced by 12% and total Met retention by more than 60%. The MyHC and actin contents in LM were not affected by the TSAA content of the diet. These results show that a deficient TSAA supply affects the amino acid composition of different body proteins. This questions the use of a constant ideal amino acid profile to express dietary amino acid requirements, but also illustrates the plasticity of the animal to cope with nutritional challenges.

Food intake is a key biological process in animals, as it determines the energy and nutrients available for the physiological and behavioural processes. In herbivores, the abundance, structure and quality of plant resources are known to influence intake strongly. In ruminants, as the forage quality declines, digestibility and total intake decline. Equids are believed to be adapted to consume high-fibre low-quality forages. As hindgut fermenters, it has been suggested that their response to a reduction in food quality is to increase intake to maintain rates of energy and nutrient absorption. All reviews of horse nutrition show that digestibility declines with forage quality; for intake, however, most studies have found no significant relationship with forage quality, and it has even been suggested that horses may eat less with declining forage quality similarly to ruminants. A weakness of these reviews is to combine data from different studies in meta-analyses without allowing the differences between animals and diets to be controlled for. In this study, we analysed a set of 45 trials where intake and digestibility were measured in 21 saddle horses. The dataset was analysed both at the group (to allow comparisons with the literature) and at the individual levels (to control for individual variability). As expected, dry matter digestibility declined with forage quality in both analyses. Intake declined slightly with increasing fibre contents at the group level, and there were no effects of crude protein or dry matter digestibility on intake. Overall, the analysis for individual horses showed a different pattern: intake increased as digestibility and crude protein declined, and increased with increasing fibre. Our analysis at the group level confirms previous reviews and shows that forage quality explains little of the variance in food intake in horses. For the first time, using mixed models, we show that the variable ‘individual’ clarifies the picture, as the horses showed different responses to a decrease in forage quality: some compensated for the low nutritional value of the forages by increasing intake, few others responded by decreasing intake with declining forage quality, but not enough to cause any deficit in their energy and protein supplies. On the whole, all the animals managed to meet their maintenance requirements. The individual variability may be a by-product of artificial selection for performance in competition in saddle horses.

Sixteen early to mid lactation Finnish Ayrshire dairy cows were used in a cyclic change-over experiment with four 21-day experimental periods and a 4 5 2 factorial arrangement of treatments to evaluate the effects of heat-treated rapeseed expeller and solvent-extracted soya-bean meal protein supplements on animal performance. Dietary treatments consisted of grass silage offered ad libitum supplemented with a fixed amount of a cereal based concentrate (10 kg/day on a fresh weight basis) containing 120, 150, 180 or 210 g crude protein (CP) per kg dry matter (DM). Concentrate CP content was manipulated by replacement of basal ingredients (g/kg) with either rapeseed expeller (R; 120, 240 and 360) or soya-bean meal (S; 80, 160 and 240). Increases in concentrate CP stimulated linear increases (P < 0·05) in silage intake (mean 22·5 and 23·8 g DM per g/kg increase in dietary CP content, for R and S, respectively) and milk production. Concentrate inclusion of rapeseed expeller elicited higher (P < 0·01) milk yield and milk protein output responses (mean 108 and 3·71 g/day per g/kg DM increase in dietary CP content) than soya-bean meal (corresponding values 62 and 2·57). Improvements in the apparent utilization of dietary nitrogen for milk protein synthesis (mean 0·282 and 0·274, for R and S, respectively) were associated with higher (P < 0·05) plasma concentrations of histidine, branched-chain, essential and total amino acids (35, 482, 902 and 2240 and 26, 410, 800 and 2119 µmol/l, respectively) and lower (P < 0·01) concentrations of urea (corresponding values 4·11 and 4·52 mmol/l). Heat-treated rapeseed expeller proved to be a more effective protein supplement than solvent-extracted soya-bean meal for cows offered grass silage-based diets.

In 2010, a routine genetic evaluation on occurrence of clinical mastitis in three main dairy cattle breeds – Montbéliarde (MO), Normande (NO) and Holstein (HO) – was implemented in France. Records were clinical mastitis events reported by farmers to milk recording technicians and the analyzed trait was the binary variable describing the occurrence of a mastitis case within the first 150 days of the first three lactations. Genetic parameters of clinical mastitis were estimated for the three breeds. Low heritability estimates were found: between 2% and 4% depending on the breed. Despite its low heritability, the trait exhibits genetic variation so efficient genetic improvement is possible. Genetic correlations with other traits were estimated, showing large correlations (often>0.50, in absolute value) between clinical mastitis and somatic cell score (SCS), longevity and some udder traits. Correlation with milk yield was moderate and unfavorable (ρ=0.26 to 0.30). High milking speed was genetically associated with less mastitis in MO (ρ=−0.14) but with more mastitis in HO (ρ=0.18). A two-step approach was implemented for routine evaluation: first, a univariate evaluation based on a linear animal model with permanent environment effect led to pre-adjusted records (defined as records corrected for all non-genetic effects) and associated weights. These data were then combined with similar pre-adjusted records for others traits in a multiple trait BLUP animal model. The combined breeding values for clinical mastitis obtained are the official (published) ones. Mastitis estimated breeding values (EBV) were then combined with SCSs EBV into an udder health index, which receives a weight of 14.5% to 18.5% in the French total merit index (ISU) of the three breeds. Interbull genetic correlations for mastitis occurrence were very high (ρ=0.94) with Nordic countries, where much stricter recording systems exist reflecting a satisfactory quality of phenotypes as reported by the farmers. They were lower (around 0.80) with countries supplying SCS as a proxy for the international evaluation on clinical mastitis.

Circadian rhythms reflect extensive programming of biological activity that meets and exploits the challenges and opportunities offered by the periodic nature of the environment. In the present investigation, we recorded the total activity of athletic horses kept at four different times of the year (vernal equinox, summer solstice, autumn equinox and winter solstice), to evaluate the presence of seasonal variations of daily activity rhythms. Athletic Thoroughbred horses were kept in individual boxes with paddock. Digitally integrated measure of total activity of each mare was continuously recorded by actigraphy-based data loggers. Horse total activities were not evenly distributed over the day, but they were mainly diurnal during the year. Daily activity rhythms showed clear seasonal variations, with the highest daily amount of activity during the vernal equinox and the lowest during the winter solstice. Interestingly, the amount of activity during either photophase or scotophase changed significantly throughout the year. Circadian analysis of horse activities showed that the acrophase, the estimated time at which the peak of the rhythm occurs, did not change during the year, it always occurred in the middle of the photoperiod. Analysing the time structure of long-term and continuously measured activity and feeding could be a useful method to critically evaluate athletic horse management systems in which spontaneous locomotor activity and feeding are severely limited. Circadian rhythms are present in several elements of sensory motor and psychomotor functions and these would be taken into consideration to plan the training schedules and competitions in athletic horses.

Records on 18 939 Friesian-Holstein cows classified for 16 linear-type traits and total score in first lactation by the British Friesian Cattle Society and similarly on 13 192 cows in second lactation were analysed to estimate heritabilities and genetic correlations among the linear traits. These comprised progeny of 542 and 477 young sires, respectively, together with older sires included to increase connections. Correlations of type with milk production traits and correlations between type in first and second lactations were estimated from subsets (of about one-half) of the data. Effects due to proportion of Holstein in the sires were removed.

Heritabilities of the linear traits were similar in first and second lactations, ranging from under 0·15 for one of the leg traits to about 0·5 for stature. Genetic correlations between traits in first and second lactation were generally over 0·75, whereas phenotypic correlations for most traits ranged from 0·3 to 0·6. Genetic and phenotypic correlations among the linear traits were generally low, except for those involving size.

Phenotypic correlations between linear traits and milk yield and composition were all small, none exceeding 0·3. Genetic correlations were generally almost as small: taking first and second lactations together, the only consistent non-negligible correlations with yield were for angularity (+0·3), fore-udder attachment (–0·2) and udder depth (–0·4). The linear traits are not useful predictors of yield.

Responses to four generations of divergent selection for lean groivth rate with ad-libitum feeding (LGA), for lean food conversion (LFC) and for daily food intake (DFI) in Large White pigs were studied. The LGA (LFC) selection criterion was designed to obtain equal correlated responses in growth rate (food conversion ratio) and carcass lean content, measured in phenotypic s.d. The selection criteria had phenotypic s.d. of 27, 29 and 253 units, respectively, and results are presented in s.d. units. There was a total of 3537 pigs, with an average of 40 boars and 40 gilts performance tested in each of the high, low and control lines per generation and the lines consisted of 10 sires and 20 dams. The generation interval was equal to 13·5 months. Animals were performance tested in individual pens with mean starting and finishing weights of 30 kg and 85 kg respectively.

Cumulative selection differentials in the three selection groups were 5·8, 3·6 and 3·3 phenotypic s.d. for LGA, LFC and DFI respectively. Direct responses to divergent selection were 1·7, 1·3 and 1·2 (s.e. 0·17) for LGA, LFC and DFI. The correlated response in LFC (1·6 (s.e. 0·18)) with selection on LGA was greater than the direct response in LFC. Conversely, the direct response in LGA was greater than the correlated response (1·1 (s.e. 0·18)) with selection on LFC. The response in LFC (–1·1 (s.e. 0·17)) with selection on DFI was similar in size but opposite in sign to the direct response in LFC. Responses were asymmetric about the control, as the high LGA and LFC responses were proportionately smaller (0·74 and 0·58) than low line responses. In contrast, the difference between the high DFI and control was four times greater than the difference between low line and control.

Heritabilities of LGA, LFC and DFI were 0·38, 0·35 and 0·29 (s.e. 0·03), when estimated by residual maximum likelihood, with common environmental effects of 0·09 (s.e. 0·02). Genetic correlations for LGA with LFC and DFI were positive, 0·76 (s.e. 0·03) and 0·23 (s.e. 0·07), but the genetic correlation between DFI and LFC was negative, –0·45 (s.e. 0·06). The experiment demonstrated that substantial responses to selection can be achieved in LGA, LFC and DFI. Selection on LGA resulted in larger direct and correlated responses than selection on LFC.

The effects of high ambient temperature (T) on protein (PD) and lipid deposition (LD) and energy utilization were studied on 36 Piétrain ✕ (Landrace ✕ Large White) barrows according to a factorial design including two temperatures (23ºC for thermoneutrality and 30ºC for the high temperature) and four feeding levels. One feeding level corresponded to the voluntary food intake (VFI) at each temperature. Expressed as proportion of VFI at 23ºC, the actual feeding levels were 1·00, 0·90, 0·80, 0·70 at 23ºC and 0·80, 0·73, 0·68 and 0·62 at 30ºC. Animals were offered a wheat, maize and soya-bean meal based diet containing 187 g crude protein per kg and 0·95 g ileal standardized digestible lysine per MJ of net energy. Pigs were housed individually and had free access to water. The experiment started at 24 kg live weight and animals were slaughtered at 65 kg live weight and their body composition was measured. Slaughter of nine control pigs at the beginning of the experiment allowed calculation of the composition of gain (nutrients and energy) according to the comparative slaughter technique. Reduction of metabolizable energy (ME) intake resulted in a reduced live-weight gain at each T: the maximum gain was 1052 g/ day in pigs offered food ad libitum at 23ºC and the minimum (760 g/day) at the lowest intake at 30ºC. Visceral organ mass was lower at 30ºC than at 23ºC but was not affected by feeding level within T. Growth responses were described as polynomial or broken-line functions of ME intake (linear-plateau for PD). Both the slope and the plateau were influenced by T. At 30ºC, PDmax (143 g/day) was reached at 22·8 MJ ME per day, while at 23ºC PDmax (165 g/day) was reached at 28·4 MJ ME per day. In both cases, PDmax was reached at 0·88 of VFI at this temperature. Also the marginal response of PD to ME intake before the breakpoint was affected by T (5·9 and 4·5 g PD per MJ ME at 23ºC and 30ºC, respectively). At identical high ME intake (e.g. 0·80 of VFI at 23ºC), PD was greater at 23ºC than at 30ºC. In contrast, severe food restriction reduced PD at thermoneutrality more than an identical food restriction obtained at high ambient T. The results indicate that heat stress has a direct negative effect on PD and affects the partitioning of energy gain between protein and fat deposition.

The 2002 World Summit on Sustainable Development focussed attention on agricultural sustainability and biodiversity in developing countries. These goals are relevant for livestock production in Kenya, where development agencies encourage resource-poor smallholders to acquire large, exotic, high-yielding dairy cows, despite their poor performance, revealed in recent surveys in the highlands and at the coast. The performance of the cows is not in question. The debate relates to the diagnosis of the causes, their treatment and the prognosis for the production system. To improve our understanding of the dynamics of the system, models of nutrition and energy, modified for the tropics, were used to measure the thermal responses over 24 h of six pure or crossbred Friesians at a mean lactation of 54 (s.d. 21·6) days, in separate zero-grazing units. Four smallholdings were on the hot, humid coast and two in the cooler highlands. The output of the model runs was related to the subsequent lactation, calving interval and profitability of the cows. The model showed that the thermal load caused moderate stress for all cows during the day, which became severe in the sun in the highlands, but the drop in air temperature, from 27 °C to 13 °C, at night dissipated the gain in body heat. At the coast, where the night temperature remained above 24 °C and relative humidity above 0·85, there was no remission of heat stress for cows with a milk yield greater than 11 l/day. The lactation curve, in all cows, declined from an initial peak to a low profile of 5 l/day. Cows in both regions with initial yields above 20 l/day had the steepest decline and longest calving intervals (457 to 662 days). They had the largest lactation yields and lowest direct cost per litre, but their poor breeding record reduced cull sales and increased replacement cost, raising the total cost per litre. By contrast, the cow with the lowest daily and lactation yield had the highest direct cost, but lowest total cost per litre, because she produced 2 heifer calves at an interval of only 317 days. These case studies serve as a reminder that, where heat load depresses appetite or poor food cannot support lactation, the energy deficit and stress reduces cow fertility, fitness, and longevity, so that she fails to breed a heifer replacement during her shortened productive life. The model predicted that food intake, depressed by heat stress, would not support a milk yield above 14 l/day and 3000 l per annum at the coast, and 22 l/day and 5000 l per annum in the highlands. Therefore, although appearing profitable in the short term, the current policy of promoting cows with higher yields than the climate and production system can support, is unsustainable. This outcome has implications for smallholder dairy development policy in Kenya, and probably elsewhere in the tropics. Instead, one should reconsider smaller exotic breeds and crossbreds with improved indigenous dairy cows whose overall productivity from milk yield, fecundity, longevity, and disease tolerance 50 years ago was better than that of the modern Holstein-Friesian in a Kenya smallholding.

A change-over design experiment, comprising four periods each of 4 weeks' duration, was used to evaluate three silage types each fed with two levels of protein in the supplement in a 3×2 factorial arrangement. The three silages were high digestibility unwilted (A), high digestibility wilted (B) and low digestibility unwilted (C). The supplements had crude protein contents of 152 and 240 g/kg dry matter, and were offered at a standard rate of 10 kg undried weight daily. The mean silage intakes were 9·3, 9·5 and 8·6 ±0·19 kg dry matter/day for A, B and C respectively, but protein content of the supplement had no significant effect on the intake of silage. Milk yield was significantly affected by both silage type and protein content of the supplement, with the mean yields being 23·6, 23·9 and 22·0 ± 0·49 kg/day for A, B and C respectively, and 22·4 and 24·0 ±0·40 kg/day for the medium and high protein supplements respectively. Although there was no significant interaction between silage type and protein content of the supplement, the greatest response to increased protein was obtained with B. Neither silage type nor protein content ofthe supplement affected animal live weight or milk composition (other than fat content, which was significantly affected by silage type). Blood plasma urea levels were 281 and 405 ± 28·0 mg/1 for the medium and high protein supplements respectively.

Total ration digestibility and nitrogen balances were carried out on three animals per treatment. The digestibility of dry matter, organic matter and nitrogen was significantly affected by both silage type and level of protein in the supplement. The output of nitrogen in the urine was also significantly affected by both these factors.

Chemical and physical treatments of barley grain increase ruminally resistant starch and can improve the rumen fermentation pattern. The objective of the present study was to evaluate the effects of chemical (addition of citric acid, CA) and physical (grinding to two different particle sizes, PS) treatment of barley grain on performance, rumen fermentation, microbial protein yield in the rumen and selected blood metabolites in growing calves. In all, 28 male Holstein calves (172±5.1 kg initial BW) were used in a complete randomised design with a factorial arrangement of 2 barley grain particle sizes×2 levels of citric acid. The diets were as follows: (i) small PS (average 1200 µm) barley grain soaked in water (no CA addition); (ii) small PS barley grain soaked in a CA solution (adding 20 g CA/kg barley); (iii) large PS (average 2400 µm) barley grain soaked in water (no citric acid addition) and (iv) large PS barley grain soaked in a citric acid solution (adding 20 g CA/kg barley). Barley grain was then incorporated at 35% in a total mixed ration and fed to the calves for 11 weeks. Feeding small PS barley decreased feed intake (P=0.02) and average daily weight gain (P=0.01). The addition of CA to barley grain did not affect intake but increased weight gain (P<0.01) and improved feed to gain ratio (P=0.03). Digestibility of organic matter and NDF tended (P<0.10) to increase, whereas faecal scoring was improved (P=0.03) and the presence of undigested grain particles in faeces was reduced (P<0.01) with CA-treated barley grain. Glucose and urea concentrations were increased (P<0.01) in the blood of calves fed the CA-treated barley grain. Ruminal pH tended (P=0.08) to be decreased with more finely ground barley and was increased when barley grain was treated with CA. Total volatile fatty acid concentrations in the rumen did not differ among treatments (P>0.05). However, the molar proportion of propionate was increased (P=0.03) when barley was more finely ground, and that of acetate was increased (P=0.04) when CA was added to barley grain. The ruminal concentration of ammonia nitrogen was increased (P<0.01) and microbial nitrogen synthesis in the rumen tended to decrease by adding CA to barley. Treating barley grain with citric acid increased fibre digestibility of total mixed rations, attenuated the decrease in ruminal pH, and improved weight gain and feed efficiency in male Holstein growing calves fed a high-cereal diet (550 g cereal grain/kg diet).

Two different cannulation procedures (simple ileal ‘T’ cannula v. The post valve ‘T’ caecal cannula (PVTC)) and two indigestible markers (TiO2 v. Cr2O3) were studied with six male littermate pigs fitted with PVTC or simple ileal ‘T’ cannulae. Six diets were used, of which two were based on wheat and wheat bran and the other four were based on two barleys of different bushel weight without and with exogenous enzymes (ß-glucanase/xylanase). Proportional TiO2 and Cr2O3 recoveries in faeces were less than 1·00, the mean values for the six diets being 0·858 for TiO2 and 0·811 for Cr2O3. With both markers, recovery in faeces was lowest for the most digestible wheat-based diet (A). The ileal apparent digestibility (IAD) coefficients of dry matter (DM), crude protein (CP), energy and amino acids measured with Cr2O3 were significantly (P < 0·001) lower than those measured with TiO2. There was no difference in overall apparent digestibility of DM, CP and energy measured with simple ileal ‘T’ cannula and PVTC techniques. However, IAD of DM, energy and CP measured with the PVTC method were significantly higher than those measured with the simple ileal ‘T’ cannula method. The data also showed that the standard errors with the simple ileal ‘T’ cannula method were greater than when using the PVTC method. Diet significantly affected ileal and overall digestibility of nutrients (P < 0·001) with values being highest for diet A and least for the wheat bran-based diet (B). Overall digestibility (OD) of DM and energy were higher for the higher bushel weight barley-based diet (C) than for the normal bushel weight barley-based diet (E). Enzyme inclusion improved OD for both barley diets and ileal digestibility of energy (0·060) and CP (0·057) for the normal bushel weight barley.

Potential measures of muscularity derived from X-ray computer tomography (CT) were assessed using data for 160 sheep (50 Suffolk males, 50 Suffolk females, 40 Texel males and 20 Charollais males). One-fifth of the lambs within each breed and sex were slaughtered at each of 14, 18 or 22 weeks of age and two-fifths slaughtered at 26 weeks. All lambs were CT scanned prior to slaughter with longitudinal and cross-sectional scans taken at three positions along the body [5th lumbar vertebra (LV5), mid-shaft of the femur (FEM) and ischium (ISC)]. After slaughter, linear measurements of side length (SL) and M. longissimus thoracis et lumborum (LTL) width (A) and depth (B) (12/ 13th thoracic vertebra) were taken on the left side of the carcass. The side was dissected and femur length (FL), the weight of three muscles surrounding the femur (M3) and the total muscle weight in the side (TM) were recorded. Five muscularity measures were calculated for the carcass. Two for the LTL muscle (A/SL, B/SL), one for the hind leg (√M3/FL3) and one for the whole carcass (√TM/SL3).

Correlations between spine length measured on the CT longitudinal scans and side length measured on the carcass were high (> 0·62), while correlations between measurements of LTL width and depth on the carcass with those on the LV5 scan were moderate (> 0·41). CT measures of muscularity were derived using linear measurements taken on CT scans together with a prediction of total muscle weight using CT tissue areas. Correlations between CT measures and dissection measures of LTL and whole carcass muscularity were moderate to high (0·33–0·54). Correlations between the dissection measure and four CT measures of hind leg muscularity were higher (0·48-0·60). These results clearly show that good in vivo measures of muscularity can be obtained for sheep by using measurements that can be taken on CT scans. This will be a useful tool for selection programmes aiming to improve sheep carcass shape, particularly those already using CT scanning to increase rates of genetic improvement in lean tissue growth.

Regression of litter weight of newborn lambs on the live weight of ewes at mating has been estimated from data on 15 breeds after conversion of group means of ewes and lambs to natural logarithms. Regression coefficients were estimated to be 0·721 for single lambs, 0·741 for twins and 0·773 for triplets. These values are not signi-ficantly different from each other. Data from ewes with single lambs and from ewes with twins are consistent with the hypothesis that litter weight at birth as a proportion of ewe weight at mating tends to dechne as ewe weight rises from small to large breeds. In a breed with ewes averaging 25 kg the expected birth weight of singles is 9·6% and of twins 15·2%, of ewe weight. For a breed with ewes of 100 kg the corresponding weights would be 6·5% and 10·6% of ewe weight. Since the estimated regression coefficient and the coefficient in the expression for metabolic weight (0·730) are alike, the regression equations can be interpreted as showing that single lambs were 22·6% and twin pairs 36·1% of ewes' metabolic weight.

Progesterone profiles were obtained from 533 dairy cows during the interval from calving to the re-establishment of pregnancy by twiceweekly radioimmunoassay of milk progesterone. The importance of abnormal patterns of ovarian activity on herd fertility was determined. Animals were divided into five categories based on profile analysis: A, normal; B, delayed start to ovarian cycles; C, cessation of cycles; D, prolonged luteal activity; and E, silent oestrus. Animals in categories B to E were subdivided into treatment groups: categories B and C either (i) untreated controls, (ii) single injection 0·5 mg luteinizing hormone-releasing hormone (Hoechst) or (iii) progesterone-releasing intravaginal device (Abbott Laboratories Ltd) inserted for 14 days; categories D and E either (i) untreated controls or (ii) single injection 0-5 mg cloprostenol (Imperial Chemical Industries).

The proportion of cows in each category was: A 77·5%; B 4·9%; C 5·1%; D 1·9%; and E 10·7%. The incidence of ‘normal’ cows was 75% (first lactation), 80% (2nd to 5th lactations) and 69% (5th to 11th lactations). For normal cows (no. = 413) the interval to the start of cyclicity varied significantly with season but was not correlated with either the intervals to first insemination or to conception. In categories B to E the open period, the number of services per conception, and the days from first insemination to conception were greater than in category A, but only in category C were any differences significant. None of the treatments reduced calving-toconception intervals.

An experiment was carried to evaluate the energy and protein requirements for the growth and maintenance of lambs of different sex classes. In all, 38 hair lambs (13.0±1.49 kg initial BW and 2 months old) were allocated in a factorial design with diet restriction levels (ad libitum, 30% and 60% feed restriction) and sex classes (castrated and non-castrated males). Four animals from each sex class were slaughtered at the beginning of the trial as a reference group to estimate the initial empty BW and body composition. The remaining lambs were weighed weekly to calculate BW gain (BWG), and when the animals fed ad libitum reached an average BW of 30 kg, all of the experimental animals were slaughtered. Before slaughter, fasted BW (FBW) was determined after 18 h without feed and water. Feed restriction induced reductions in body fat and energy concentration, whereas water restriction showed the opposite effect, and the protein concentration was not affected. The increase in BW promoted increases in body fat and energy content, and these increases were greater in castrated lambs, whereas the protein content was similar between classes tending to stabilize. The net energy required for gain (NEg) and the net protein required for gain (NPg) were not affected by sex class; therefore, an equation was generated for the combined results of both castrated and non-castrated lambs. The NEg varied from 1.13 to 2.01 MJ/day for lambs with BW of 15 and 30 kg and BWG of 200 g. The NPg varied from 24.57 to 16.33 g/day for lambs with BW of 15 and 30 kg and BWG of 200 g. The metabolizable energy efficiency for gain (kg) was 0.37, and the metabolizable protein efficiency for gain (kpg) was 0.28. The net energy required for maintenance (NEm) and the net requirement of protein for maintenance (NPm) did not differ between castrated and non-castrated lambs, with values of 0.241 MJ/kg FBW0.75 per day and 1.30 g/kg FBW0.75 per day, respectively. The metabolizable energy efficiency for maintenance (km) was 0.60, and the efficiency of metabolizable protein use for maintenance (kpm) was 0.57. Nutritional requirements for growth and maintenance did not differ between castrated and non-castrated lambs. This study emphasizes the importance of updating the tables of international committees and of including data obtained from studies with sheep breeds raised in tropical conditions, with the purpose of improving the productive efficiency of the animals

Muscle metabolism (in interaction with other organs and tissues, including adipose tissue) plays an important role in the control of growth and body composition. Muscle ontogenesis has been described in different genotypes of cattle for myofibres, connective tissue and intramuscular depots. The ontogenesis or the action of putatively important factors controlling muscle development (IGF-II expression, IGF receptors, growth hormone (GH) receptor, myostatin, basic fibroblast growth factor, transforming growth factor-β1, insulin and thyroid hormones) has also been studied on bovine foetal muscle samples and satellite cells. The glucose/insulin axis has been specifically studied in both the bovine adipose tissue and heart. Clearly, cattle, like sheep, are mature species at birth based on their muscle characteristics compared to other mammalian or farm animal species. The different myoblast generations have been well characterised in cattle, including the second generation which is liable to be affected by foetal undernutrition at least in sheep. Interesting genotypes, for example, double-muscled genotype, have been characterised by an altered metabolic and endocrine status associated with a reduced fat mass, specific muscle traits and different foetal characteristics. Finally, the recent development of genomics in cattle has allowed the identification of novel genes controlling muscle development during foetal and postnatal life. Generally, a high muscle growth potential is associated with a reduced fat mass and a switch of muscle fibres towards the glycolytic type. The possibility and the practical consequences of manipulating muscle growth and, hence, body composition by nutritional and hormonal factors are discussed for bovines based on our current biological knowledge.

Two experiments were conducted to study the effects of phytase derived from Escherichia coli (ECP) and Peniophora lycii (PLP) on performance, nutrient digestibility, and phosphorus (P) equivalency values of young pigs; and the influence of varying ratios of calcium (Ca) to total phosphorus (Ca:tP) with or without ECP on growth performance of pigs. In each experiment, 48 10-kg pigs were housed in individual pens for 28 days. Experiment 1 was designed to study the efficacy of ECP and PLP in improving growth performance and bone mineralization of young pigs given a low inorganic P (iP) diet. In the experiment, pigs were blocked by weight and sex and randomly allocated to eight dietary treatments. Each treatment had six replicates. The treatments were a positive control with adequate iP (PC); a low iP negative control (NC) diet; NC with supplemental iP in the form of monosodium phosphate added to provide 0·75 or 1·50 g iP per kg diet (as-fed basis); NC with ECP or PLP added at 500 or 1000 FTU per kg (as-fed basis; one phytase unit or FTU is defined as the quantity of enzyme required to liberate 1 μmol of iP per min, at pH 5·5, from an excess of 15 μmol/l sodium phytate at 37°C). In experiment 2, the objective was to study the effect of varying Ca:tP ratio with or without ECP on growth performance of growing pigs. Pigs (eight replicates) were blocked by weight and sex and randomly assigned to six dietary treatments in a 3×2 factorial arrangement of Ca:tP ratios at 1·2, 1·5, or 1·8; and ECP at 0 or 1000 FTU per kg (as-fed basis). In experiment 1, ECP ( P<0·001) and PLP ( P<0·05) linearly increased daily gain. There was a positive linear ( P<0·05) response to the supplementation of the NC diet with ECP or PLP in the mineralization of the third and fourth metacarpal bones. Phosphorus equivalency values for 500 FTU of ECP or PLP based on mineralization of the third metacarpal bone were 0·77 g or 0·572 g, respectively. There were linear ( P<0·001) and quadratic ( P<0·05) responses to ECP, and linear ( P<0·01) response to PLP in P digestibility. Neither iP supplementation nor either of the two phytases had significant effects on digestibility of dry matter, protein or energy. In experiment 2, reducing Ca:tP ratio linearly improved ( P<0·05) daily gain, food intake, and food efficiency in pigs regardless of phytase supplementation. There was an enzyme by Ca:tP interaction on food intake. These studies in young pigs showed that ECP and PLP were efficacious in improving the growth performance and bone mineralization and that reducing the Ca:tP ratio enhanced performance response to phytase supplementation.

The objective was to evaluate the association between changes in daily rumination time (dRT) and early stages of disease during early lactation and to assess the performance of two proposed disease detection indices. This cohort study included 210 multiparous Holstein cows at the University of Florida Dairy Unit. Cows were affixed with a neck collar containing rumination loggers providing rumination time. The occurrence of health disorders (mastitis, metritis, clinical hypocalcemia, depression/dehydration/fever (DDF), digestive conditions, lameness and clinical ketosis) was assessed until 60 days in milk. Two indices were developed to explore the association between dRT and disease: (i) Cow index (CIx), based on changes in dRT in the affected cow during the days before the diagnosis of health disorders; (ii) Mates index (MIx), index based on deviations in dRT relative to previous days and healthy pen mate cohorts. Subsequently, an alert model was proposed for each index (ACIx and AMIx) considering the reference alert cut-off values as the differences between average index values in healthy and sick cows for each specific disease. The sensitivity (SE) of ACIx detecting disease ranged from 42% (digestive conditions and DDF) to 80% (clinical hypocalcemia) with 84% specificity (SP). The SE of AMIx ranged from 46% (digestive conditions and DDF) to 100% (clinical hypocalcemia) with 85% SP. Consistent reductions in rumination activity, both within cow and relative to healthy mate cohorts, were observed for each health disorder at the day of diagnosis. However, the ability of the proposed algorithms for detecting each specific disease was variable.