This paper examines a paradox at the centre of efforts to improve livestock production in sub-Saharan Africa. For decades livestock nutrition and animal food have been identified as critical constraints, yet producers have shown little interest in improved food technologies. The main argument is that the analyses highlighting nutrition and food as critical constraints have focused primarily on biological productivity, and are thus at odds with livestock producers’ perceptions. The paper concludes by suggesting that livestock research in Africa must taker greater account of different systems, situations and producers, as well as key characteristics of technology such as reliability and management flexibility.

Segregation analyses were applied to data from an experimental sheep flock to investigate the presence of a major gene affecting litter size. The data set contained 14 years of litter size data, with up to five parities per ewe, from Cheviot sheep carrying the putative Thoka fecundity gene from Icelandic sheep. Segregation analyses were performed using a Markov chain Monte Carlo method implemented using Gibbs sampling. Uniform priors were initially used for estimating variance components, the gene effect and fixed effects in the data. Genotypes in the base generation were assumed known based on the use of the imported Icelandic donor semen from the founder rams. The use of alternative priors (naïve and inverse-gamma distributions) for the variance components did not significantly affect the results, demonstrating the data to be sufficiently powerful for the analyses used. Segregation analyses detected a major gene for litter size in the Thoka Cheviot flock increasing litter size by 0·70 lambs per ewe lambing for a single copy of the gene. When the analysis was repeated without fixing the genotypes in the base population, the analyses predicted a different genotype than that previously used for one of the founder rams and suggested the major gene to be segregating in the Cheviot founder animals prior to the introduction of the Thoka rams. A liability threshold analysis was also applied to the data. As identified in other studies, the threshold analysis overestimated the heritability, but the estimated major gene effect was not significantly different from other analyses. The results confirm the segregation of the Thoka gene in a Cheviot flock and highlight the statistical method as a useful tool for identifying carrier animals to be used for future matings.

The effect of partial replacement of poly- (PUFA) with monounsaturated (MUFA) fatty acids in pig diets on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness was studied. No effect of dietary fat was observed on total saturated fatty acid concentration in any of the backfat layers or intramuscular lipid fractions. No significant effect of dietary fat was observed for the MUFA concentration in the outer layer, but a marked effect was evident for the inner layer (P < 0·001). A linear effect of dietary MUFA was observed for MUFA (P < 0·001) and PUFA (P < 0·001) in polar lipids. No significant effect of dietary treatment was observed on total concentration of n-3 fatty acids in any lipid location but a marked effect was observed for total n-6 fatty acid concentration. The response of pig fatty acid n-6 concentration was different depending on the lipid location. The neutral lipid fraction showed significantly lower n-6/n-3 fatty acid ratio than the subcutaneous fat. Intramuscular polar lipids showed no significant response of n-6/n-3 ratio. A linear effect of dietary MUFA concentration was observed on the melting point on the inner backfat layer (MP = 34·4 (s.e. 2·51) + 0·15 (s.e. 0·07) ✕ dietary MUFA (g/kg dry matter) (R2 = 0·24, P < 0·05)), indicating that the partial substitution of dietary PUFA by MUFA produced a fat of higher consistency. No response of the melting point of the outer layer to dietary treatment was observed. A marked effect of dietary fat was shown for backfat hardness (P < 0·001), gumminess (P < 0·001) and chewiness (P < 0·001). No effect of dietary fat was observed on the rheological properties of longissimus lumborum muscle.

The effect of tail docking on metabolizable energy requirements and carcass characteristics was studied using 80 weaned entire Awassi male lambs. Docking was performed within 3 days of birth and lambs were weaned at 90 days old. Docked and undocked lambs were randomly allocated to four groups, individually penned and offered different amounts of a pelleted concentrate diet. The pelleted diet was estimated to contain 11·8 MJ of metabolizable energy (ME) and 182 g of crude protein (CP) per kg dry matter (DM). Lambs on the high levels of intake were slaughtered at a target weight of approximately 45 kg. Other lambs were maintained on the diet for 149 days before being slaughtered. The right sides of all carcasses were cut into standardized commercial cuts then dissected into muscle, fat and bone. The soft tissue was pooled and analysed for DM, C P, ash and fat. Prediction of live-weight gain (LWG) and empty body gain for a given ME intake (MEI) was made using the growth and MEI data. MEI was expressed as MJ per kg metabolic body weight (M 0·75) per day. Tail docking had no effect (P > 0·05) on lamb growth from birth to weaning. During the post-weaning growth period, LWG and empty body gain were significantly higher (P < 0·05) for undocked lambs than docked lambs, at feeding levels between 0·31 and 0·52 MJ/kg M 0·75 per day and similar (P > 0·05) at high levels of intakes (between 0·74 and 1·1 MJ/ kg M 0·75 per day). Hot and cold carcass weights were similar (P > 0·05) for the two groups. Differences in empty body weight and fleece-free empty body weight were significant (P < 0·05) only for the 0·443 to 0·522 MJ/kg M 0·75 per day level of ME intake. Predicted ME requirements were higher for docked lambs for an estimated LWG between 0 and 100 g/day and lower for higher LWG (125 to 225 g/day). Docking had no effect (P > 0·05) on food conversion efficiency (FCE). Carcasses from docked lambs had significantly lower (P < 0·001) internal plus tail fat. Pooled soft tissue excluding tail fat, for the undocked lambs contained significantly more (P < 0·01) protein, less (P < 0·001) fat, higher (P < 0·01) moisture and similar (P > 0·05) ash content.

The present experiment was designed to evaluate the effect of different time spans of ad libitum feeding of pigs prior to slaughter after a period of restricted feeding on performance and texture characteristics of the meat. Te n litters of five pigs (Duroc ✕ Landrace ✕ Large White crosses) were allocated to five feeding treatments (AA, R28A42, R43A27, R52A18 and R60A10) at the age of 70 days. AA-pigs were given ad libitum a concentrate diet from day 70 to slaughter at day 140 (approx. 100 kg live weight). R28A42, R43A27, R52A18 and R60A10 pigs were given food at a restricted level (0·6 of ad libitum) for 28, 43, 52 and 60 days, respectively, followed by ad libitum feeding for 42, 27, 18 and 10 days, respectively, until slaughter at day 140. All pigs that had been given food at a restricted level for a period (R28A42, R43A27, R52A18 and R60A10) showed a compensatory growth response in the subsequent ad libitum period. However, only pigs on ad libitum for a minimum of 27 days prior to slaughter (R28A42 and R43A27) had carcass weights and muscle mass similar to that of the control pigs (AA) at slaughter. The restricted feeding increased meat proportion, whereas the feeding strategies had no effect on technological meat quality traits (pH24, drip loss and CIE-colour traits: L*, a* and b*). During compensatory growth, protein turn-over was increased and positively related to the length of the ad libitum period as indicated by the concentration of elongation factor-2 (eEF-2) (P < 0·10), the activity of µ-calpain (P < 0·01) and the myofibrillar fragmentation index (MFI) 1 day post mortem in m. longissimus dorsi (P < 0·08) and the solubility of collagen (P < 0·01). Although not significant, the shear force at day 1 followed the same pattern of improvement as the MFI. The concentration of eEF-2 increased at a faster rate following transition to ad libitum feeding than did the activity of µ-calpain. This suggests that muscle protein synthesis increases at a faster rate after change to ad libitum feeding and reaches the same level as in the control pigs (AA) before muscle protein degradation. This time lag between the increase in protein synthesis and degradation could explain the compensatory growth response and it also suggests that in order to use the compensatory growth mechanism to improve tenderness, the optimal time of slaughter may not coincide with the period of highest growth rates, but may occur at a later stage, when muscle protein degradation is maximal. For pigs slaughtered at 100 kg live weight, we expect muscle protein degradation to be maximal some time beyond 42 days of ad libitum feeding prior to slaughter.

This study examined the effects of glutamine and nucleotides on growth, intestinal villous height and immune responses of weaned pigs. Eighty weaned pigs (Landrace ✕ Yorkshire ✕ Duroc) were randomly assigned to five treatments, including a control diet and a 2 (glutamine 1·0 and 1·5%) by 2 (nucleotides 500 and 1000 p.p.m.) factorial design. There were no differences among the five treatments in weight gain from weeks 0 to 4 and 0 to 8 of the experiment. However, the food intake of treatment 3 (glutamine 1·0% and nucleotides 1000 p. p. m. ) for weeks 4 to 8 was higher (P < 0·05) than that of the control group. Intestinal villous height, and serum immunoglobulin-G concentration 2 h post lipopolysaccharide injection, were higher (P < 0·05) for pigs administered treatment 3 than for controls. Furthermore, foot and mouth disease (FMD) neutralizing antibody titres were also higher (P < 0·05) than the control group for pigs given treatment 3 when measured 3 weeks following vaccination with FMD antigen. These observations suggest that a combination of 10% of glutamine and 1000 p. p. m. of nucleotides in the diet could improve food intake and intestinal villous height and promote the immune responses and FMD antibody titres of weaned pigs.

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.

Fish meal is the most widely used protein source in commercial eel foods and information on the nutritive value of more economical protein sources is needed in order to improve cost-effectiveness of diets. This investigation was conducted to determine apparent digestibility coefficients of available plant and animal meals for juvenile Australian short-finned eel (Anguilla australis australis, Richardson). The suitability of a modified Guelph-type settlement faecal collector in eel digestibility studies was assessed. Animal by-product (spray-dried meat solubles; blood meal; high fat poultry meal) and plant protein (soya bean; canola; maize gluten; lupin; field pea) meals were mixed with a reference diet and marker (0·3: 0·69: 0·01) and the resultant test diets given to the juvenile eels (3·15 (s.e. 0·42) g) at 0·05 live weight per day. The reference diet and all the test diets were well accepted by the fish. Apparent digestibility coefficients for crude protein (ADCCP) for maize gluten meal (MGM), lupin meal (LM) and blood meal (BM) were found to be 0·97, 0·96 and 0·96 respectively and they were significantly (P < 0·001) higher than that for the other ingredients. However, apparent digestibilities for dry matter (ADCDM) and energy (ADCkJ) were significantly (P < 0·0001) higher for animal by-products than for plant proteins except for maize gluten meal. This was explained by the higher content of nitrogen free extractives in the former plant proteins. There was a strong positive correlation between ADCDM and ADCkJ for all ingredients (P < 0·01). Weaker positive correlations were also found between ADCCP and ADCDM and between ADCCP and ADCkJ. Similar results obtained for warm water species using similar faecal collection techniques and over limited eel digestibility data support the suitability of the modified Guelph-type settlement collector system in digestibility studies with juvenile eels.

An experiment was carried out in growing chickens to study the effect of supplementation of a semi-synthetic diet containing soya-bean meal as the sole protein source with DL-methionine, to improve its biological value, on the excretion of endogenous protein and amino acids measured in lower ileum and total tract using traditional methods. Thirty-two White Rock male broilers (10 days old) were randomly divided into eight groups each of four birds, of similar body weight (mean live weight: 142·8 (s.e. 0·68) g), and individually housed in metabolism cages. Following a paired-feeding design based on metabolic body weight (kgM0·75), each group of birds was given, for an experimental period of 20 days, each of four levels of protein (60, 120, 180 or 240 g/kg; 5 days each) in two groups of isoenergetic (14·5 kJ metabolizable energy per g dry matter) and semi-synthetic diets based on soya-bean meal, either not supplemented or supplemented with 2 g/kg DL-methionine (diets S and SM, respectively). After 3 days of each treatment excreta were collected for 48 h, frozen and stored at –20ºC. At the end of the fourth treatment three chickens of each group were killed and their lower ileal contents collected. The remaining chick of each treatment was fasted for 24 h and given a protein-free diet for 8 days and excreta were collected for the last 4 days. Then (day 39 of age), chickens were killed and lower ileum contents removed and stored at –20ºC. Samples of excreta and lower ileum contents were subjected to nitrogen (N) analysis by Kjeldahl procedure and amino acid (AA) analysis by high-performance liquid chromatography. Supplementation with DL-methionine of the soya-bean meal-based diets halved total tract endogenous AA losses. Regression analysis produced a higher estimation of ileal and faecal endogenous AA excretion than feeding a protein-free diet. Endogenous AA excretion determined in the lower ileum was higher than in excreta no matter which estimation procedure was utilized. In conclusion, supplementation of dietary protein with the first limiting AA to improve its protein quality, causes an important drop in endogenous AA losses, that may have an important effect on the N economy and energy requirements in poultry. The use of regression analysis on excreta data where graded amounts of protein are given to growing chickens, seems a suitable method for determining endogenous AA losses provided that good quality proteins are used.

The present study examines the size distribution of ovine steroidogenic and non-steroidogenic luteal cells throughout pregnancy. Cells were isolated from corpora lutea collected from early (< 8 weeks), mid (9 to 14 weeks) or late (15 to 18 weeks) stages of pregnancy. Cells were stained for 3β-hydroxysteroid dehydrogenase (3β-HSD) activity, a marker for steroidogenic cells. Both 3β-HSD positive and β-HSD negative cells covered a wide spectrum of size ranging from 7 to 37 μm in diameter. There was a significant increase (P > 0·01) in mean diameter of non-steroidogenic luteal cells as pregnancy progressed. Mean diameter of 3β-HSD negative cells increased from 17·8 (s.e. 0·4) μm in the corpus luteum of early stage of pregnancy to 22·4 (s.e. 0·3) μm in the corpus luteum of advanced pregnancy. However, there was no significant increase in the mean diameter of 3β-HSD positive cells. Corpora lutea obtained from early stages of the pregnancy contained more steroidogenic cells than the cells obtained from mid and late pregnancy (P < 0·01). Percentage of 3β-HSD negative cells had increased 2·07-fold by 18 weeks of pregnancy when compared with the early stage of pregnancy. In contrast, percentage of 3β-HSD positive cells had decreased to 50% of starting values during the same period (P < 0·05). These results indicate that the ovine corpus luteum of pregnancy is morphologically dynamic over the course of pregnancy. Steroidogenic activity of luteal cells may decrease as pregnancy progresses, especially activity of the large luteal cells.

The objective of this study was to investigate if there is a genotype ✕ feeding system interaction for milk production in Holstein-Friesian dairy cows. For this purpose, 48 high genetic merit (HM) and 48 medium genetic merit (MM) dairy cows, were used in a two (genotypes) ✕ three (levels of concentrate feeding) randomized-block design experiment in three consecutive years. In year 1, all animals were in their first lactation, while in year 2 and year 3, 18 and 12 first lactation cows replaced animals culled at the end of the previous lactation. A total of 66 cows remained in the study in the same feeding system for the 3-year duration of the study. Concentrate feeding levels were 376, 810 and 1540 kg per cow per lactation; these were identified as the LC, MC and HC feeding systems respectively. There was a separate farmlet for each feeding system; farmlets were managed so that pre-grazing and post-grazing herbage height were similar for all three feeding systems. When compared on treatment means there was a significant genotype ✕ feeding system interaction for fat yield, while for mean solid-corrected milk yield the interaction was close to statistical significance (P = 0·07). However, regression coefficients of both milk and protein yield on pedigree index for milk and protein yield were significantly different between the LC and the HC. The interaction between feeding system and the regression of both on pre-experimental milk and protein yield were close to statistical significance (P = 0·08 and P = 0·09 respectively). Outputs of milk, fat, protein and lactose were greater for the HM than the MM cows. Feeding system had a significant effect on milk, fat, protein and lactose yields. There was a significant genotype ✕ feeding system interaction for body condition score (BCS) at the end of lactation; the MM cows had a higher rate of body tissue repletion than the HM cows especially in the HC system. The results suggest that there is a genotype ✕ concentrate feeding level interaction and that feeding systems developed in the past for animals of lower genetic merit may require adaptation if they are to be optimal for higher genetic merit animals.

The objective of this experiment was to evaluate the performance and well being of animals accommodated outdoors over the winter period on out-wintering pads (OWPs), relative to animals housed indoors in conventional slatted floor sheds. One hundred and twenty-six steers were assigned at random to one of seven treatments. The first six treatments were accommodated on OWPs. These six treatments were arranged in a three (6, 12 and 18 m2 per head space allowance) by two (wind sheltered or exposed) factorial design. A seventh treatment group (control) was housed indoors in a slatted-floor shed at a space allowance of 3 m2 per head. All animals were offered silage ad libitum and 5 kg concentrate per day. All animals were slaughtered at the end of the 151 day experiment. Animal production and indices (climatic energy demand (CED), behaviour, cleanliness, hoof condition and immune function) of animal welfare were evaluated. There was no significant effect of stocking density outdoors or sheltering on live-weight gain, carcass gain, fat score, fat score per 100 kg carcass, kidney plus channel fat (KCF) as a proportion of carcass, carcass conformation score, killing-out proportion, food intake or food efficiency. Relative to animals housed indoors on slats, animals accommodated outdoors on OWPs had higher daily live-weight gain (F < 0·001), carcass gain (F < 0·05), and food intake (F < 0·05). However, animals on the OWPs had less KCF per kg carcass and lower fat scores per 100 kg carcass. There was no effect of shelter on the CED of animals out-wintered, which was higher (P < 0·001) than their counterparts wintered indoors on slats. Animals housed on slats were cleaner than animals housed at 6 or 12 m2 per head (F < 0·05) but not 18 m2per head. There was no effect of treatment on physiological measures. Animals confined on the OWP with or without shelter, had a greater number of lying bouts per 24 h (F < 0·076), had a greater synchronized lying frequency (F < 0·082) and displayed less hesitation prior to lying when compared with animals housed on slats. Indoor animals had more white line disease (F < 0·01) and under-run (F < 0·001) on their front hoof, when compared with outdoor animals. Animals accommodated outdoors at 18 m2per head had more (F < 0·05) claw erosion while the indoor animals had a greater (F < 0·001) degree of under-run present on their hind hoof. There was no evidence to suggest that out-wintering compromised animal welfare. Further studies are required to determine the reason for the increased carcass growth and leanness of the cattle on the OWPs.

An experiment was undertaken to compare the productivity of crossbred ewes, produced by crossing Texel sires with Rouge de l’Ouest (Rouge) dams and Rouge sires with Texel dams, relative to purebred Texel and Rouge ewes. The purebred and crossbred ewes were crossed with Rouge and Texel sires. The proportion of productive ewes was similar in the purebred and crossbred ewes with an average figure of 0·92. Irrespective of crossing sire, Rouge ewes produced 0·48 more lambs per ewe lambed than Texel ewes (P < 0·001). The two crossbred ewe types (Texel ✕ Rouge and Rouge ✕ Texel) each produced similar numbers of lambs (on average 1·92 lambs per ewe lambed). Individual heterosis values for ewe fertility and prolificacy were small and not significant (–1·67 for the proportion of productive ewes and –3·14 for the number of lambs born per ewe lambed). Maternal heterosis values were also not significant but were of larger magnitude (6·26 for ewe fertility and 3·12 for prolificacy). Lamb mortality (number of lambs born dead per ewe lambed) at birth was similar for purebred Rouge (0·44) and Texel (0·30) ewes and was significantly reduced by crossbred matings and mating the crossbred ewes (individual heterosis –30·68, P < 0·10; maternal heterosis –80·23, P < 0·001). Individual and maternal heterosis values for lamb growth rate from birth to six weeks were 8 (P < 0·05) and 4 (P > 0·05) respectively. Lamb growth rate from birth to weaning was significantly lower in lambs from Texel ewes compared with those from the other genotypes (P < 0·05). Individual and maternal heterosis values for live-weight gain from birth to weaning were 5 (P < 0·10) and 5 (P < 0·01). The results of the current study demonstrate the superior performance of purebred Rouge ewes compared with purebred Texel ewes in terms of prolificacy and lamb growth rate from birth to weaning. However, both breeds had high lamb mortality at birth. Crossbreeding led to the production of hybrid ewes which had relatively high prolificacy with low levels of dystocia and lamb mortality.

The seasonal effects of heat load and photoperiod on yield and composition of milk from primiparous cows in the course of lactation were studied using test day records from 8968 primiparous cows on 76 farms in Georgia, collected from 1990 through 1997. The effect of prepartum photoperiod on milk production in the subsequent lactation of these cows was also evaluated. These estimated seasonal effects were compared with those estimated for 4728 primiparous cows on 13 farms, and for 1538 multiparous cows on three farms during consecutive lactations in Israel from 1994 through 1996. During lactation, the day length had a positive effect on milk yield and negative effects on fat and protein concentrations in the milk, but the daily change in day length had positive effects on milk yield and fat concentration, and a smaller positive effect on protein concentration. The day length during the prepartum period had negative effects on milk yield and fat and protein concentrations. The heat load during lactation had negative effects on milk yield and fat and protein concentrations. Most of the effects were highly (P < 0·001) significant. There was a very good match between the results obtained for primiparous cows in Georgia and Israel, for the combined effects of heat load and photoperiod during lactation on milk yield and protein and fat concentrations. The match between primiparous and multiparous cows in Israel was better for milk yield and protein concentration than for fat concentration. The estimated effects of pre-partum photoperiod were higher for multiparous cows in Israel than for primiparous cows in either country.