A genetic study was carried out to: (1) conduct a genetic analysis of longevity of Swedish Yorkshire sows, (2) study the environmental and genetic factors that influence the presence and severity of osteochondrosis, and (3) investigate the relationship between breeding values for osteochondrosis and longevity of sows. The data for the longevity analyses were extracted from the Swedish litter-recording scheme data bank (Quality Genetics, former Scan Avel HB). After editing original data, records of 9814 Yorkshire sows with 7553 (77%) uncensored and 2261 (23%) censored born 1986 through 1997 were used in the analyses. Litter size at first and last farrowing, age at first farrowing, backfat thickness, daily gain and weight at completion of performance test (~170 days) were included as fixed effects in all analyses. The combination of herd-year effect was treated as fixed or random, time-independent or time-dependent in different analyses. Sire effect was considered as the source of genetic variation and thus a sire model was used. The analyses of osteochondrosis were based on information on 14 388 Landrace and 14 458 Yorkshire pigs from the Swedish pig progeny-testing scheme, recorded from 1987 through 1997. The birth herd and the combination of sex, testing station, year and month for start of test were included as fixed effects in the statistical model. Variance and covariance components for osteochondrosis recorded at elbow and knee joints were estimated in a bivariate animal model by the restricted maximum likelihood method within each breed. In the survival analyses (Yorkshire sows), the fixed effects of herd-year (when it was treated as fixed effect), litter size at first and at last farrowing, age at first farrowing, backfat and gain at completion of performance test were highly significant (P < 0·01). Herd-year combination was the major cause of variation for risk of culling, compared with other fixed effects. The risk of being culled at a certain time decreased as the litter size at first and at last farrowing, or backfat of the gilt at completion of performance test increased. With increasing age at first farrowing, the risk of being culled at a certain time increased. Heritability in the original scale for longevity ranged from 0·21 to 0·31. The results for osteochondrosis showed that the combined effect of sex-testing station-year and month of start of test was highly significant (P < 0·01). Estimates of heritabilities for osteochondrosis score were similar for both Landrace and Yorkshire breeds and was, on average, 0·21. The correlations between breeding values for longevity and osteochondrosis were low (on average 0·07, adjusted for genetic trends) but were significant (P < 0·01) and in a favourable direction: higher osteochondrosis load associated with higher risk of being culled.

A dynamic model for simulation of growth in pigs, extended to describe thermoregulatory processes, was made stochastic to simulate groups of pigs with between-animal variation in mature body protein (Pα) and lipid mass (Lα), in the potential rate at which mature mass is attained (B⋆), and in the distribution of body protein and lipid over pools and depots. The resulting variation in body composition leads to variation in energy requirements for protein turn-over and thermoregulation, causing between-animal variation in maintenance requirements (MEmaint).

Simulated population means for Pα, Lα /Pα and B⋆ were varied in three steps each. Excluding unrealistic parameter combinations this led to 33 – 6 = 21 simulated genotypes. Simulated within-population coefficients of variation (CV) were 7, 15 and 3%. Random replicates of each genotype were simulated five times, in climatic conditions that were in turn severely cold, mildly cold (about 5 and 1ºC below lower critical temperature), thermoneutral, mildly hot and severely hot (about 1 and 5ºC above upper critical temperature), during the entire growth period of 23 to 100 kg live weight. Simulated food intake was ad libitum.

Simulated thermoneutral within-population standard deviations of body protein and lipid content were 0·21 to 0·46 kg and 0·78 to 2·14 kg at 100 kg body weight. On average, the corresponding values in cold and hot conditions were slightly higher.

MEmaint showed a protein-turn-over-related within-population CV of 1·5% at thermoneutrality. Thermoregulatory action contributed about 4% extra variance in cold and hot conditions but CV values were not affected. A genetic increase in the maximum protein deposition rate from 100 to 250 g/day would increase MEmaint as related to protein turn-over and thermoregulation by 11% at thermoneutrality, and by 6 to 11% in cold or hot conditions. Two relevant groups of genotypes could be distinguished based on the within-population regression coefficients of MEmaint on daily or cumulative protein deposition (bdailyPdep, bcumPdep). These ranged from 0·250 to 0·428 kJ/kg0·75 per day per g/day and from 2·77 to 5·45 kJ/kg0·75 per day per kg, respectively, in 12 ‘conventional’ genotypes at thermoneutrality. On average, bdailyPdep was increased by 48%, 20%, –11% and –36% in the other climatic conditions mentioned above, respectively. The corresponding increase of bcumPdep was 32%, 14%, 8% and 48%. Three fast-growing lean genotypes showed similar bdailyPdep and bcumPdep at thermoneutrality, but much more pronounced increases in cold and hot conditions: 137%, 49%, –12% and + 88% for bdailyPdep and 248%, 108%, 17% and 196% for bcumPdep.

It is concluded that differences in body composition traits between pig genotypes do not cause important between-genotype differences in thermoregulatory MEmaint, and that thermoregulatory processes contribute little body-composition-related variation to hot or cold MEmaint within most genotypes.

The inferences to be made from this with regard to experimental design are discussed. The verification of the above predictions will require a very elaborate and large-scale experiment.

Differences in the metabolic resource situation between non-reproductive male and female mice of a line selected for high litter size at birth (average of 22 born per litter) and a non-selected control line (average of 10 born per litter) were investigated in two replicates. Brody curves were fitted to individual data on body weight against age and linear regression lines were fitted to individual data on cumulative food intake against age. Mature body weight and mature daily food intake were higher in selected mice than in control mice and higher in males than in females. Selected males matured faster than selected females and control mice. In general, differences in growth and food intake curves between species or lines can mostly be explained by differences in mature size. Therefore, parameters were subsequently scaled by individual estimates of mature body weight. Differences that remain after scaling are a consequence of what have been called specific genetic factors. Scaled mature food intake was higher in selected mice than in control mice and higher in females than in males. Scaled maturation rate was higher in selected mice than in control mice and higher in selected males than in selected females. This shows that in the present study, specific genetic factors have been detected for both body weight and food intake, which suggests that selection for increased litter size has disproportionally changed the resource allocation pattern.

In the accompanying paper, specific genetic factors for body weight and food intake were identified in non-reproductive male and female mice of a line selected for high litter size at birth (average of 22 born per litter) and a non-selected control line (average of 10 born per litter). The existence of these factors are indicated by variation in efficiency parameters such as growth efficiency and maintenance requirements. Residual food intake (RFI) and Parks’ estimates of growth efficiency (AB) and maintenance requirements (MEm) were used to quantify these factors. In the growing period, females had a higher RFI (are less efficient) than males. At maturity, selected mice had higher RFI than control mice and selected females had higher RFI than selected males. AB was higher in selected-line mice than in control-line mice, and higher in males than in females. MEm was higher in selected-line mice than in control-line mice, and higher in females than in males. The results indicate the existence of specific genetic factors for both growth efficiency and maintenance requirements. Selected females may increase RFI in the adult state to anticipate the metabolically stressful periods of pregnancy and lactation, to support a genetically highly increased litter size.

The components of phenotypic variance attributable to maternal lineage for production traits of the UK Holstein Friesian dairy population were estimated. First lactation production records of 55 230 cows calving between 1996-1998 in the UK Holstein Friesian population were used in the analysis. Maternal pedigree records were traced back to 1960 to establish maternal lineages. The tracing resulted in 36 320 cows being assigned to 11 786 cow families with more than one cow per maternal lineage. Using test day records it was possible to explore aspects of the lactation curve in terms of persistency and different periods of production. The traits analysed were 305-day milk yield and composition traits, the first three milk yield tests of lactation and two measures of persistency. A contemporary record design was used to minimize pair-wise additive direct genetic relationships between cows within a maternal lineage and to remove both the effect of heterogeneous variance over time and the complications of permanent environment effects. No significant component of variance attributable to maternal lineage was found for yield traits. When data were restricted to maternal lineages with five or more records, persistency, as a ratio of cumulative yield in the last third to that in the first third of a 300-day lactation, was estimated to have a 4·4% component due to maternal lineage variance significant at the 5% level. The study also investigated the preferential treatment of cow families. Some evidence of maternal lineage × herd interaction was found.

Restricted maximum likelihood analyses fitting an animal model were conducted to estimate genetic parameters with a pooled-data set of performance tests (growth traits and food intake) on 661 bulls and progeny tests (growth traits and carcass traits) on 535 steers. Traits studied included concentrate intake (CONC), roughage intake (ROU), TDN conversion (TCNV), TDN intake (TINT) of bulls; rib eye area (REA), marbling score (MARB), dressing proportion (DRES) and subcutaneous fat depth (SCF) of steers. Body weight at start (BWS), body weight at finish (BWF) and average daily gain (ADG) of all animals were measured. Estimated heritabilities were 0·18 (CONC), 0·71 (ROU), 0·11 (TCNV) and 0·36 (TINT); 0·02 (REA), 0·49 (MARB), 0·15 (DRES), 0·15 (SCF), and from 0·20 to 0·38 for growth traits. Genetic correlations of ROU were different from those of CONC, probably due to inconsistent restrictions on concentrate intake; those of TINT with the weights, ADG and SCF were high. MARB showed positive genetic correlations with growth traits and low correlations with TINT and SCF. High potentiality for improvement of marbling score was suggested.

The aim of this work in pigs was to evaluate the effect of fermented liquid food (FLF) and the combination of FLF plus short-term addition of an antibiotic food additive zinc bacitracin (FLF + ZB) compared with fed non-pelleted dry food (NPDF), on microbial metabolism in the gut and the effects on flavour and odour attributes and profiles of pig meat as well as boar odour from entire male and female pigs.

At an average start weight of 60 kg, 108 pigs (54 males and 54 females) were equally allocated to three treatments according to pen-replicate, litter and sex. Microbial metabolism in the gut was studied in 24 pigs, eight from each treatment. For sensory profile evaluation (flavour, odour and tenderness) of pork loins from m. longissimus dorsi, 48 pigs (24 entire males and 24 females) were selected. The sensory evaluation of different qualities of flavour and odour as well as tenderness of cooked pork loins (LD) was done by a boar taint (skatole and androstenone) trained taste panel. To evaluate the odour and the flavour, a sensory profile analysis was performed which involved the following attributes: total off-odour/off-flavour, pig, urine, manure, naphthalene, rancid, sweet and sweat in the whole sample including both meat and fat.

Giving FLF to pigs significantly changed the microbiota in the gastro-intestinal tract compared with NPDF. In particular, the density of coliform bacteria was reduced in the gastro-intestinal tract of the pigs on FLF. Giving FLF demonstrated no effects on skatole concentration in caecum, colon, blood and backfat and boar odour attributes, whereas administration of FLF + ZB decreased the skatole concentrations and the typical boar odours, pig and manure odour, compared especially with the pigs on NPDF. However, meat from pigs given FLF either with or without zinc bacitracin had smaller but significantly worsened scores for three flavour attributes — pig flavour, rancid flavour and total off-flavour — compared with meat from NPDF pigs and the three flavour attributes were equally affected in both sexes. This seems to point to a significant worsening of meat flavour in pigs given FLF that is independent of sex and boar odour problems (skatole and androstenone).

An experiment was conducted in 1995 in order to examine muscle growth, muscle histochemical properties, muscle metabolism and meat quality of two types of Danish Landrace pigs representing the growth potential of years 1976 and 1995, respectively. Danish Landrace pigs representing 1976 (slow-growing, SG) originated from a breeding station where the population was maintained without being selected for production traits such as daily gain, food conversion ratio and meat content. Pigs representing Danish Landrace of 1995 (fast-growing, FG) were bought from certified Danish pig breeders. The pigs were simultaneously tested for performance from 40 to 95 kg live weight. The daily gain, food conversion ratio and meat content of the carcass were improved proportionately by 0·43, 0·24 and 0·03 in FG pigs compared with SG pigs. In m. longissimus dorsi (LD), the cross-sectional area of muscle fibres was smaller in FG pigs compared with SG pigs indicating increased muscle fibre number. Data further suggest increased satellite cell proliferation in muscles of FG pigs. Serum from FG pigs stimulated the proliferation of C2C12 muscle cells to a greater extent than serum from SG pigs, although the serum level of insulin-like growth factor 1 did not differ between pig types. The effect of serum on protein turn-over of C2C12 myotubes did not depend on pig type. The glycogen concentration in the LD did not differ significantly between pig types, while the activity of citrate synthase, 3-OH-acyl-CoA-dehydrogenase, and lactate dehydrogenase were higher in the LD of SG pigs compared with FG pigs. Pork chop colour of FG pigs was proportionately 0·09 lighter (L⋆) and 0·13 less red (a⋆) than pork chops of SG pigs. The total muscle pigment concentration in the LD, m. biceps femoris and m. vastus intermedius was proportionately reduced by 0·17, 0·19 and 0·11, respectively, in FG pigs compared with SG pigs. In the LD, the concentration of myoglobin was proportionately reduced by 0·17 in FG pigs. The chemical composition of the LD differed between pig types such that the water content was higher and protein content lower in LD from FG pigs compared with SG pigs. The pH of the LD measured 45 min and 24 h post mortem, drip loss and thawing loss were similar for both pig types. Meat tenderness of conditioned pork chops of FG pigs was slightly reduced in accordance with a decreased intensity of the 31 kDa peptide band and increased cooking loss. The present study suggests that increased muscle fibre number and rate of muscle DNA deposition (satellite cell proliferation) have contributed to the increased muscle growth as a result of selection for performance in pigs under Danish conditions. However, the increase in growth performance was accompanied by deterioration in muscle colour and slightly reduced tenderness.

As part of an investigation of factors responsible for a previously reported lower efficiency of carcass lean gain in steers offered grass silage diets, 16 Simmental × Friesian steers (515 (s.e. 6·4) kg) were offered perennial ryegrass silage ad libitum (C0) or silage plus rolled barley at 200 (C20), 400 (C40) or 600 (C60) g/kg total diet dry matter (DM). Barley-supplemented diets were intake-restricted to provide equal DM and metabolizable energy (ME) intakes to those offered C0. Eight steers were selected at random to determine the ME contents of the diets by open-circuit respiration calorimetry. The other eight steers were offered the same diets and were blood-sampled at 20- to 60-min intervals, for 10 h, to monitor changes in the concentrations of a number of nutritionally related plasma metabolites and hormones. Estimated ME intakes in these steers were 85·7, 83·1, 84·4 and 86·2 (s.e. 0·91) MJ/day from diets C0, C20, C40 and C60 respectively. Rumen-fistulated Hereford × Friesian steers provided 24-h rumen data for the same diets offered at equal amounts of ME per kg metabolic live weight.

Mean 24-h plasma concentrations of insulin and insulin-like growth factor 1 (IGF-1) were linearly and positively related (P < 0·01 and P < 0·001 respectively) and glucagon quadratically related (P < 0·05) to the proportion of barley in the diet. Plasma insulin increased after feeding on all diets but concentrations on diets C40 and C60 were significantly higher than those on C0 and C20 at all post-feeding sampling times up to 9 h after feeding. Plasma IGF-1 concentrations increased above pre-feeding levels following feeding of the higher barley diets (C40 and C60; P = 0·053) but remained unchanged in steers offered C0 and C20. Mean plasma concentrations of glucose were unaffected by diet but those of β-hydroxybutyrate (BOHB) and urea were positively and negatively related respectively (both P < 0·001) to the proportion of barley in the diet. Plasma BOHB and urea concentrations also changed with time after feeding (P < 0·001). Amongst the rumen parameters measured (pH; ammonia and volatile fatty acid concentrations and proportions) only the mean 24-h concentrations and proportions of butyrate were positively related to the proportion of barley in the diet (P = 0·051 and P < 0·05 respectively). All rumen parameters were affected by time after feeding (acetate, P < 0·01; others, P < 0·001) but there was no interaction between treatment and time for any parameter.

When compared with other menadione derivatives such as menadione sodium bisulphite (MSB), menadione nicotinamide bisulphite (MNB), an organic salt combining menadione and nicotinamide, shows better stability towards physical and chemical factors once it is added to pre-mixes or foods. The present work evaluates the bioavailability of the two vitamins present in this compound and toxicity in the pig. To assess vitamin bioavailability, pigs were given small amounts of food containing MNB or equivalent amounts of MSB and nicotinamide in the free form. Menadione and nicotinamide concentrations in blood samples drawn at set times after the diets were given did not reveal any significant differences between the two modes of administration. Haematic levels of both vitamins in animals receiving MNB, or MSB and nicotinamide, were after 2, 4, 8 and 12 h higher (P < 0·001) than those of untreated animals. The tolerance level to MNB was evaluated in pigs given diets containing graded amounts of MNB (100, 500, 2500 mg/kg) for 28 days. No significant (P > 0·05) differences were recorded in live weight, food intake and gain/food ratio in pigs given these diets when compared with those given an unsupplemented diet. Haemoglobin and bilirubin levels did not differ between animals given various amounts of MNB and control animals. Plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in pigs given 100 mg/kg of MNB did not show significant differences when compared with those observed in pigs given an unsupplemented control diet. In pigs on the diets supplemented with 500 and 2500 mg/kg of MNB there was a significant increase in the two enzymatic activities as compared with controls (P < 0·001 and P < 0·01). In the case of ALT this had disappeared by 28 weeks. MNB is a good source of vitamin K for the pig and does not appear to have any adverse effects, even when administered at levels higher than those normally used in pig food supplementation.

When modelling the effect of a changing nutrient supply to growing animals, it is important to distinguish the individual response curve of an animal from the change in this response that may occur during growth. A data analysis model is proposed where, for an individual animal, the relation between protein deposition (PD) and metabolizable energy (ME) intake above maintenance (MEp) is curvilinear, so that PD intersects the origin and reaches its maximum at the maximum protein deposition rate (PDmax). An increase of MEp beyond that required to attain PDmax would not change PD. The MEp not used for protein synthesis can be used for lipid deposition (LD). The relation between PD and LD on the one hand and ME on the other hand can then be described as a function of the maintenance energy requirement (MEm), PDmax, the level of ME required to attain PDmax (F; as a multiple of MEm) and the energetic efficiencies of PD (kp) and LD (kf). Of these statistics, only kp and kf were assumed to be independent of body weight (BW), age or genotype. Variation in PDmax was described as a Gompertz function (of age) whereas variation in F was assumed a linear function of BW. Maintenance energy requirement was expressed as a power function of BW. To evaluate the model, 145 nitrogen and energy (indirect calorimetry) balances were obtained from three types of pigs (Large White castrated males (cLW) and Piétrain × Large White castrated males (cPP× ) and males (bPP×)) ranging in BW between 45 and 100 kg and housed under thermoneutral conditions. Animals were allotted to one of four energy levels ranging from 0·70 to 1·00 of ad libitum intake. The MEm was not different between genotypes (849 kJ/kg BW0·60) whereas the kp and kf were 0·56 and 0·75, respectively. For castrated animals on ad libitum intake, PDmax started limiting PD at approximately 130 days of age (78 and 86 kg BW for cLW and cPP×, respectively). Before this age and for bPP×, PD was limited by MEp. In bPP×, the difference between PD and PDmax was small (less than proportionately 0·05). The F did not change with BW for bPP× (2·85 × MEm) whereas for the other genotypes, it decreased linearly from 4·47 at 45 kg to 2·00 at 100 kg of BW. Due to its nature, the model allows estimation of PDmax even when energy is restricting PD.

Four hundred piglets were housed in 20 pens and offered for 42 days a pre-starter and then a starter compound supplemented with trace elements given as sulphates (SULF) or proteinates (PROT) at a common level (100) or at a reduced level (20) of inclusion. The common level supplied 278, 148, 315 and 98 mg/kg and the reduced level supplied 128, 38, 135 and 50 mg/kg of iron (Fe), copper (Cu), zinc (Zn) and manganese (Mn), respectively, taking into account the natural food contents. Proteinates used in the trial were analysed and described in terms of content and quality of different potential ligands. Piglet growth was not affected by any treatment. At the end of the trial blood samples were collected from eight pigs for each treatment. These animals were slaughtered and their livers were removed, weighed and analysed. Compared with SULF, PROT increased significantly plasma levels of Fe (25·1 v. 15·7 μmol/l), haemoglobin (10·9 v. 10·4 g/dl) and the number of red blood cells (6·4 v. 6·1 millions per μl) but the liver recovery of Fe was not affected by any treatment. In piglets receiving PROT the liver content of Cu and Zn increased significantly compared with those receiving SULF. On reducing the dosage, Cu in the liver significantly decreased with SULF but not with PROT and the amount of Zn decreased more with SULF than with PROT. The results may reflect a better availability of Cu and Zn when proteinates rather than sulphates were used as mineral supplements.

Increasing sow food intake in late gestation prevents loss of sow fatness prior to farrowing. However, this may result in reduced food intake and greater overall fat loss during lactation and has also been associated with increased incidence of agalactia. In this experiment 78 Camborough sows (parities 1 to 3) were given food at one of two levels: either 1·15 × maintenance energy (normal-N sows, 2·3 (s.e. 0·03) kg/day) or 2·00 × maintenance energy (high-H sows, 3·9 (s.e. 0·04) kg/day) from day 100 of gestation until farrowing. Lactation food intake, changes in sow live weight and backfat thickness and piglet growth rates were then measured. Diet digestibility in early lactation was measured using a chromium III oxide marker in the food. There was no change in backfat thickness in late gestation in H sows (0·2 (s.e. 0·25) mm), whereas N sows lost backfat during this period (1·6 (s.e. 0·23) mm, P <; 0·001). There was no difference in lactation food intake between the two groups (6·5 (s.e. 0·13) kg/day) and differences in backfat thickness at parturition were maintained through to weaning. H sows did not show increased incidence of agalactia compared with N sows. There was no difference in diet digestibility between the two treatment groups. Food intake level in late gestation did not affect piglet birth weights, growth rates or mortality. It is concluded that the main benefit of increasing sow food intake in late gestation was to reduce sow backfat loss during the reproductive cycle.

The digestibility and voluntary intake of fibrous roughages and acorns was studied in six wild boar and five Meishan pigs. The neutral-detergent fibre (NDF) concentration of the diets ranged from 139 to 767 g/kg of the organic matter. Organic matter digestibility of acorns, mixed grass and wheat straw was higher in wild boar (P < 0·05) while voluntary food intake of the Meishan pigs was higher for mixed grass, hay and wheat straw (P < 0·05). Organic matter digestibility (P < 0·01) and NDF digestibility (P < 0·05) were both negatively related to NDF concentration of the diet. No relationship existed between voluntary food intake and NDF concentration of the diet. The apparent nitrogen (N) digestibility was positively related (P < 0·01) to dietary N while no relationship was found with dietary NDF. The negative effect of NDF on digestibility could only be partly explained by the lignin concentration of NDF. Much more important was the lower efficiency of the carbohydrate fermentation in the caecum and colon when compared with the direct absorption of glucose from the small intestine. It was estimated that digestible NDF at a maximum contributed proportionately 0·26 to the metabolizable energy intake of the animals. It was concluded that wild boar and domestic pigs should be able to maintain themselves on an all fresh grass diet when NDF concentration of the diet does not exceed about 550 g/kg and N concentration is not too low.

An experiment was carried out to study the effect of adding α-galactosidase to the diet on the performance and digestive parameters of growing-finishing pigs. Fifty-four gilts, average body weight (BW) of 43 (s.e. 0·4) kg, were allocated to 18 pens and used in a production experiment divided in two consecutive periods of 28 days each (growing and finishing). In each period gilts were given a diet based on cereals, soya-bean meal and peas, supplemented (Enzyme) or unsupplemented (Control) with 200 units per kg of α-galactosidase. All diets included 2 g Cr2O3 per kg as a digestibility marker. Food intake and body weight were recorded every 2 weeks and faecal samples by pen were collected at the end of each period. Average daily gain (ADG), food: gain ratio and faecal digestibility of dry matter (DM), crude protein (CP) and neutral-detergent fibre (NDF) were calculated. At the end of the production experiment nine gilts from each treatment were selected and given the finishing diet for a further 10 days before being slaughtered. Samples of digesta from the ileum and caecum were collected and ileal digestibility of monosaccharides determined. Short chain volatile fatty acids (SCVFA ) and purine bases (PB) in caecal digesta were analysed. The use of α-galactosidase improved the ADG (P < 0·01) and the food: gain ratio (P < 0·01) simultaneous to increases in the faecal digestibility of DM (P < 0·05), CP (P < 0·05) and NDF (P = 0·07) in the finishing period. Alpha-galactosidase supplementation also improved the ileal digestibility of some monosaccharides (galactose, rhamnose, mannose and fucose) of the dietary fibre fraction (P < 0·05); and reduced total caecal concentration of SCVFA (P = 0·15), proportion of branched-chain VFA (P < 0·001), and concentration of total PB (P < 0·001). It is concluded that adding α-galactosidase to a cereal-soya-bean meal-pea diet improves ADG, food: gain ratio and digestibility in fattening pigs, and reduces the amount of fermentable substrate flowing to the large intestine.

A study was carried out in the dry season, from October 1993 to May 1994 at an institutional farm in Niono (14º5’N, 6ºE, 295 m), on the Sahelian border of Mali with a semi-arid climate. Thirty-four local Sahelian goats in their first to fifth lactation weighing about 27 kg were used. Eleven of them suckled twin and 23 suckled single kids. The does were herded on natural rangeland for 8 to 9 h/day and received no food supplements. Dry season forage mass, intake and nutritive value of diets selected by goats, milk yield and effects on kids’ growth were measured.

The vegetation cover consisted of a herbaceous stratum dominated by annual gramineae plants and a woody stratum composed of 26 species of plants, whose relative abundance varied according to the topography and soil type. The goats spent between 0·126 (early dry season) and 0·004 (late dry season) of grazing time on herbaceous cover and the remaining time on consuming leaves, flowers and fruits of woody plants. The phytomass decreased as the dry season advanced. However, nutrient intake was relatively constant during the course of the study period, as the goats compensated for low biomass by walking more and grazing larger areas and for longer periods. On average, goats selected diets with 121 g crude protein and 7·6 MJ metabolizable energy per kg dry matter.

The milk yield and milk fat were measured weekly for 29 weeks but data for only 12 weeks are interpreted and discussed. Mean daily actual and fat-corrected milk (40 g fat per kg milk) production for the first 12 weeks of lactation was 692 (s.e. 139) g and 627 (s.e. 73) g respectively. The milk yield was maximum in the 1st week of lactation followed by a gradual decline. Milk yield was affected by litter size, number of lactation, weight and age of does at parturition. The does with twin kids produced significantly more milk (762 (s.e. 110) g/day) than the does with singles (656 (s.e. 158) g/day) (P < 0·05). The milk yield increased from the first lactation (542 (s.e. 49) g/day) to the third lactation (739 (s.e. 49) g/day) (P < 0·05) with no difference between the third and fifth lactation. Does over 27 kg produced more milk than those under 27 kg (P < 0·001) and does over 2·5 years produced more milk than younger does (P < 0·01). Milk fat was inversely related to milk production. Kids born as singles were heavier (2194 (s.e. 76) g) than those born as twins (1966 (s.e. 78) g) (P < 0·05). The kid growth rate was affected by birth weight (P < 0·001) and milk yield of dams (P < 0·01). Within litter size (single or twins), sex had no significant effect on the growth rate of kids, however the singles grew faster than twins (P < 0·001) throughout the 12 weeks of measurement. Single kids were 1·41 times as heavy as twins at 12 weeks.

It is concluded that, the milk yield of does and weight gain of kids under the precarious feeding conditions of the study indicate that the local goats monitored were adapted to local harsh conditions. Nutrition has been regarded as the main constraint to goat production from the range in the dry season. Further specific studies are needed to overcome the dry season nutritional stress and to improve goat production.

The conventional system of estimating metabolizable protein requirement is unsuitable for defining amino acid requirements because nitrogen loss cannot be converted to amino acid loss, and because there is a lack of data on the utilization efficiencies of individual amino acids for various productive purposes. Therefore, we are proposing an alternative approach. In this review, we use methionine (Met) and cysteine (Cys) for wool production in sheep as examples, and define requirement as retention in both body and wool protein, plus the amount of obligatory oxidation that accompanies the retention. The requirements are expressed in terms of the net absorption. Mathematical models for the calculation of the requirements of both amino acids are established based on the level of absorption, endogenous contribution from body protein breakdown, oxidation rates and the amino acid composition of body and wool proteins. The flows and oxidation of Met and Cys, and Cys synthesis de novo as well are quantified using their plasma kinetics data. Wool growth rate is predicted from the amount of the amino acid available for protein retention and the partition ratio to wool growth. The estimated requirements for Met and Cys absorption for Merino sheep at maintenance are 0·45 to 0·75 g/day and 0·52 to 0·63 g/day depending on the live weight of the sheep. When wool growth rate increases to 10 g/day, the requirements increase to 0·91 to 1·24 g/day and 1·97 to 2·02 g/day respectively. The utilization efficiency for protein retention varies with the level of absorption, and is 0·02 to 0·55 for Met, and 0·09 to 0·55 for Cys. The model shows that wool growth rate is restricted by the lack of Cys supplied in conventional diets and is very sensitive to changes in oxidation of the amino acids.

Twenty-four multiparous ewes were used to test the hypothesis that synchronizing the hourly rate of release of energy and nitrogen in the rumen would optimize milk production. Three diets were formulated using the in situ degradability of the food ingredients, to differ in their rate of organic matter (OM) and nitrogen (N) release in the rumen. All diets contained 400 g grass silage per kg dry matter (DM) and were predicted to have a similar content of metabolizable energy (11·8 MJ/kg DM), metabolizable protein (102 g/kg DM), neutral-detergent fibre (365 g/kg DM) and daily ratio of N: OM supply to the rumen but differ in their hourly pattern of nutrient release to be either synchronous (S), asynchronous (A) or intermediate (I). The diets were offered ad libitum as a complete feed in a 3 × 3 Latin-square design consisting of three periods each of 28 days duration. Synchronizing the hourly supply of energy and N to the rumen did not significantly alter milk or milk fat yield (g/d), milk protein content (g/kg), DM intake (kg/day), total time spent eating or the number of meals per day. However, compared with ewes offered diets I or A, those offered diet S had a lower milk fat content (g/kg; P < 0·05) whilst protein yield (g/day) tended to be increased (P = 0·05). Animals offered the synchronous diet (S) had lower plasma urea concentrations throughout the day and significantly higher beta-hydroxybutyrate concentrations at 14:00 and 18:00 h than those offered diets I or A. In conclusion, synchronizing dietary energy and N supply to the rumen did not have a major effect on milk production in ewes.