Ten Landrace × (Landrace × Large White) young female pigs were allocated to each of four treatments. The experiment was arranged as a 2 × 2 factorial design, the variables being oestradiol benzoate v. ethyl oleate and boar v. visual testing. The oestradiol benzoate (or ethyl oleate) was administered at 140 days of age, the treatment consisting of six injections, over a 3-day period, of 0·5 ml of either ethyl oleate or a solution of 0·4 mg/ml β-oestradiol-3-benzoate in ethyl oleate. Subsequently the gilts were either inspected visually each day or taken to a vasectomized boar for oestrus detection. All gilts were mated at the second oestrous period, and slaughtered on the 20th day of gestation. Those gilts receiving exogenous oestrogen attained puberty significantly earlier (P<0·01) than the control gilts. Of the 20 gilts treated with oestrogen, 12 (60%) attained puberty within 5 days of the start of treatment. No significant difference was found between boar testing and visual testing, although receptivity to mating appeared to be lower for visually tested gilts. There are no significant differences between treatments in ovulation rate, conception rate or embryo survival.

Designing breeding schemes suitable for smallholder livestock production systems in developing regions has hitherto been a challenge. The suggested schemes either do not address farmers’ breeding goals (centralized station-based nucleus schemes) or yield slow genetic progress (village-based schemes). A new breeding scheme that integrates the merits of previously suggested schemes has been designed for Menz sheep improvement in Ethiopia. It involves selection based on breeding values in nucleus flocks to produce elite rams, a one-time only provision of improved rams to villagers and a follow-up village-based selection to sustain genetic progress in village flocks. Here, we assessed whether conventional selection of breeding rams based on breeding values for production traits, which is the practice in station-based nucleus flocks, meets farmers’ breeding objectives. We also elicited determinants of farmers’ ram choice. Low but significant correlations were found between rankings of rams based on farmers’ selection criteria, estimated breeding values (EBV) and body weight (BW). Appearance traits (such as color and horn) and meat production traits (BW and linear size traits) significantly determined farmers’ breeding ram choice. The results imply that conventional selection criteria based solely on EBV for production traits do not address farmers’ trait preferences fully, but only partially. Thus, a two-stage selection procedure involving selection on breeding values in nucleus centers followed by farmers’ selection among top- ranking candidate rams is recommended. This approach accommodates farmers’ preferences and speeds up genetic progress in village-based selection. The Menz sheep scheme could be applied elsewhere with similar situations to transform conventional station-based nucleus breeding activities into participatory breeding programs.

The objective of this study is to investigate the age-related changes of and the effects of dietary conjugated linoleic acid (CLA) on muscle-fibre types in commercial pigs. We divided 25 crossbred male pigs into five age groups (7, 30, 60, 100 and 180 days) and 30 finishing pigs into two dietary groups (one fed a CLA-enriched diet and the other fed a control diet for 30 days). We analysed the composition (%) of myosin heavy-chain (MyHC) mRNA according to the absolute copies of each MyHC (I, IIa, IIb and IIx) mRNA, and the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) in the longissimus muscle. From days 7 to 180, the MyHC I mRNA abundance and SDH and MDH activities presented a decreasing trend, the MyHC IIb mRNA abundance presented a steady trend and the MyHC IIa and IIx mRNA abundances presented an increasing trend. On day 30, MyHC I and IIb mRNA abundances were at their lowest (P < 0.05), and the MyHC IIa and IIx mRNA abundances were at their highest (P < 0.05). In the CLA group, the MyHC I mRNA abundance and the activities of SDH and MDH were improved in the longissimus muscle, whereas pressure loss, drip loss and average back fat depth significantly decreased (P < 0.01) and shear force significantly increased (P < 0.01). Loin eye area, feed conversion rate and meat colour showed some tendency to be improved. These results indicated that more oxidative fibres might convert to glycolytic fibres with increasing age or weight, and that the early developmental stage might be a key stage for this conversion. During the finishing stage, the proportion of oxidative fibres might be increased by dietary CLA supplementation, which may contribute to the water-holding capacity of meat. The results would provide an important basis for the application of muscle-fibre types in the improvement of pork quality.

Calreticulin (CRT) is a Ca2+-binding molecular chaperone in the endoplasmic reticulum. We cloned and characterized the CRT gene in an important marine food fish species Asian seabass (Lates calcarifer). The full-length DNA of the CRT gene was 2194 bp, including a complete open reading frame encoding 420 amino acid residues, a 113 bp 5′-untranslated region and an 818 bp 3′-untranslated region. The CRT gene contained nine exons and eight introns covering a total of 2772 bp genomic DNA from the start to stop codon. Ten single nucleotide polymorphisms (SNPs) were detected in introns and an exon in six individuals collected from five different locations. The CRT gene was assigned to linkage group 4 of the linkage map of Asian seabass. Quantitative real-time PCR revealed that the CRT gene was highly expressed in liver at the age of 1, 3 and 7 months under normal conditions, whereas its expression in liver reduced sharply after 0.5 to 2 h cold challenge at 16°C, and then increased slowly. A preliminary association analysis showed a significant (P < 0.001) association between the SNP6 in the CRT gene and the mortality after cold challenge at 16°C. Our results suggest that the CRT gene is associated with cold tolerance of Asian seabass and further investigation will be necessary to illustrate the underlying mechanisms.

The farrowing process is one of the most energy-demanding activities for the modern hyperprolific sow. This study evaluated the effects of supply of energy on the expected date of farrowing on the farrowing kinetics and piglets’ performance during the first 24 h after birth. A total of 80 sows were used. The sows and their respective litters were considered as the experimental unit. On the expected day of farrowing, the sows were allocated to one of the following groups: sows that did not have access to feed from farrowing induction until the end of the farrowing process (CON, n = 40); sows fed 500 g of energetic supplement, which consisted of 250 g of the basal lactation diet plus 250 g of cane sugar, 18 h after farrowing induction (SUP, n = 40). The farrowing duration, farrowing assistance, birth interval, number of total born, stillborn and mummified piglets were recorded for each sow. Piglets were weighed individually at birth and 24 h later. The interval from birth to first suckle was evaluated individually for each piglet in 16 randomly selected litters (eight litters per treatment group). Blood glucose concentrations of six sows were measured shortly after expulsion of the first piglet. Farrowing duration, farrowing assistance and stillborn rate tended to be greater (P = 0.06, P = 0.09 and P = 0.07, respectively) in sows from the CON group compared to sows from the SUP group. However, there was no difference (P > 0.05) between the groups for birth interval. Colostrum intake was greater (P < 0.05) for piglets from the SUP group compared to piglets from the CON group. Additionally, BW gain of the piglets suckling the SUP group was greater (P < 0.05) than those suckling the CON group at 24 h after birth. The blood glucose concentrations during the expulsive stage of farrowing were greater (P < 0.05) in the SUP group than for sows from the CON group. In conclusion, supplying modern hyperprolific sows energy on the expected day of farrowing is a valuable nutritional intervention to improve the farrowing kinetics and piglets’ performance in early life.

Twenty-four crossbred wethers (live weight 27·6 (s.e. 0·36) kg) were divided into three groups and given a concentrate diet. One group was a control, one was given cimaterol (10 mg/kg diet) and one was given clenbuterol (2 mg/kg diet). After 49 days on treatment the animals were fasted for 48 h and slaughtered at a live weight of about 36 kg. The effects of both beta-agonists were similar. Food conversion was proportionately 0·20 better in treated sheep which also produced heavier (18·3 v. 17·0 kg, P < 0·01) carcasses that were leaner. The cross-sectional area of the m. longissimus was increased proportionately by about 0·25 (P < 0·001) and the thickness of subcutaneous fat over the muscle reduced by 0·37 (P < 0·01). The loin joint from treated animals contained proportionately 0·30 more muscle (P < 0·001) and 016 (F > 0·01) less fat. Muscles from treated sheep had higher pHu values (P < 0·01) which resulted in reduced loss of exudate during storage (P < 0·01) and darker colour (P < 0·05). They also contained only about half as much intramuscular fat (13 v. 27 mg/g, P < 0·001) and less haem pigments (2·4 v. 3·9 mg/g, P < 0·001). The results indicate that beta-agonists substantially improve carcass quality but, under certain conditions of pre-slaughter handling, may reduce lean meat quality. The similarity of response to both beta-agonists suggests the observed effects on meat quality may be common to this class of drug.

The aim of this study was to estimate genetic and phenotypic (co)variances between objective measures and carcass visual scores, as a test of the potential value of visual scores in selection programmes to improve carcass composition in crossbred lambs. In each of 1986, 1987 and 1988, 22 Suffolk rams were chosen with either high or low scores on an index designed to increase lean growth rate. These rams were joined with 18 to 20 crossbred ewes each and their lambs were grown on grass to one of three target live weights (35·5, 41·5 and 47·0 kg) for slaughter. The carcasses of 1881 lambs were visually scored for overall conformation and fatness using the standard Meat and Livestock Commission methods. Additionally, a more detailed 15-point scale assessment of conformation and a direct visual score of subcutaneous fat on the carcass were taken on 1252 lambs during the latter 2 years of the study. Carcass composition was estimated by dissection of a shoulder joint into lean, fat and bone. The possibility of combining data collected on lambs slaughtered at each of the three target live weights, for the estimation of genetic parameters was investigated. Results indicated that heritability estimates for a trait using data collected within each of the slaughter groups were homogeneous. Genetic correlations between records collected for a trait within each of the slaughter groups were not significantly different from one. These results indicated that data collected at each of the target slaughter weights could justifiably be combined. Heritability estimates were generally higher for shoulder tissue proportions (0·3) than for visual scores (0-2). Genetic correlations between all conformation scores and tissue proportions were not significantly different from 0 and therefore of little or no value in predicting carcass composition. Genetic correlations between visual scores of fat and both tissue proportions and ratios were generally high (around 0·65). These results suggest that fat scores collected on crossbred animals could be valuable in purebred selection programmes where improving carcass composition of the crossbred generation is the underlying objective.

The present study compares estimates of caecotrophes production from urinary purine derivatives (PD) excretion with that from preventing caecotrophy by using a neck collar. A total of 64 New Zealand growing male rabbits were used to study the effect of diet composition on caecotrophes production. Diets were formulated using two sources of structural carbohydrates (fibre): alfalfa hay (AH) and sugar-beet pulp (SBP), mixed at two constant proportions, (0·75: 0·25) AH diets and (0·25: 0·75) SBP diets. Both diets included either barley or maize grain at two fibre: grain ratios (F/G, 80: 20 and 45: 55). Diets were given ad libitum. Growth rate, dry matter intake and digestibility were not modified by the grain source, although high F/G diets resulted in a lower growth rate (19·8 v. 26·4 g/day; P < 0·001). Between fibre sources, dry-matter intake and growth were higher in AH than in SBP diets (122·5 and 25·6 v. 101·6 and 20·4 g/day, respectively, P < 0·001 and P < 0·01). Rabbits given high F/G ratio and AH diets excreted more caecotrophes than those given low F/G ratio and SBP diets (19·5 and 20·9 v. 16·3 and 14·85 g/day, respectively). Microbial-N recycling through the caecotrophy process was higher when considering data from PD excretion (1·33 g/d) than when estimated by preventing caecotrophy (0·72 g/day).

A preliminary trial established a subclinical level of infection with Oesophagostomum dentatum capable of affecting the performance of growing pigs. Thereafter a slightly higher level of infection (100 000 larvae) was administered to each of 24 individually- and scale-fed pigs to investigate the effect of O. dentatum on performance, digestibility and nitrogen retention over the live-weight range 32 to 64 kg. Worm-free but otherwise similar pigs served as controls. Infection reduced growth rate (12·9 %) and decreased efficiency of feed conversion to body weight (14·9%). There was no effect on killing-out percentage or area of eye muscle in cross-section, but infected pigs had relatively lower backfat depths (5·5 to 12·5 %). Infection did not influence nitrogen retention, but apparent digestibility of the dry matter, organic matter, nitrogen, gross energy and crude fibre was reduced. Possible explanations for these effects are discussed in relation to tissue changes associated with larval development in the large intestine.

Over a 2-year period, 80 dairy cows were used to investigate the relationship between nutrition and fertility. The plane of nutrition of half the cows was raised for a 9-week period around the expected time of artificial insemination in both breeding seasons. The net effect was that the high-plane cows received 15% extra metabolizable energy during the 9-week period. This was achieved by giving these cows a high-energy concentrate (calculated value 13·1 MJ metabolizable energy per kg dry matter), whereas the control cows received a concentrate with a calculated energy density of 12·5 MJ metabolizable energy per kg dry matter. All cows received a basal ration that supplied an average of 75 and 80 MJ metabolizable energy per cow per day in the 2 years, respectively. Control cows received their calculated amount of dry matter using the control concentrate, whereas the high-plane cows received their calculated dry matter using the high-energy concentrate. The high-plane cows also received an additional 0·5 kg dry matter per head per day of their concentrate. They also received additional concentrates (2 kg per head per day) for 8 weeks, commencing 12 weeks before the second calving.

There was no effect of dietary treatment on the reproductive performance of the cows, although some measures of milk yield, live weight and body condition were affected significantly.

Analysis of data from all cows, regardless of treatment group, showed that the probability of pregnancy to an insemination was most strongly associated with milk yield on day 21 of lactation. Only the cumulative yield to day 21 was related to the probability of pregnancy after accounting for the trend with yield on day 21. The chance of pregnancy was lower in cows whose milk yields on day 21 were high but, among cows with similar yields on day 21, those with the higher cumulative yields at that time tended to become pregnant more readily. Thus both yield per se and rate of increase in yield in early lactation were associated with subsequent reproductive performance.

Increasingly more studies are raising concerns about the increasing consumption of meat and the increasing amount of crops (cereals and oilseeds in particular) used to feed animals and that could be used to feed people. The evolution of this amount is very sensitive to human diets and to the productivity of feed. This article provides a 2050 foresight on the necessary increase in crop production for food and feed in three contrasting scenarios: diets with no animal products; current diets in each main region of the world; and the average diet of developed countries extended to the whole world. We develop empirical aggregate production models for seven world regions, using 43 years and 150 countries. These models realistically account for the contribution of feed from food plants (i.e. plants that would be edible for humans) and of grassland to animal products. We find that the amount of edible crops necessary to feed livestock in 2050 is between 8% and 117% of today's need. The latter figure is lower than that in comparable foresight studies because our models take into account empirical features occurring at an aggregate level, such as the increasing share of animal production from regions using less crop product per unit of animal product. In particular, the expected increase in animal production is estimated to occur mostly in Sub-Saharan Africa and Asia, where the amount of feed from food crops required per unit of animal product proves to be lower than that in other areas. This 117% increase indicates that crop production would have to double if the whole world adopted the present diet of developed countries.

The effects of trace element deficiencies in lambs, particularly zinc, copper, cobalt and selenium, include decreased growth rates and increased mortality. However, trace element supplementation of sheep reared under extensive conditions has several logistical problems.

Two trials were designed to investigate the effect of a zinc, cobalt and selenium soluble glass bolus on the trace element status of out-wintered ewe lambs. In trial 1 600 8-month-old ewe lambs (500 Scottish Blackface and 100 North Country Cheviots) were allocated to two treatment groups; 300 were treated with a zinc, cobalt and selenium soluble glass bolus (zinc) and 300 were untreated (control). In trial 2, 315 8-month-old Scottish Blackface ewe lambs were allocated to three treatments: 105 were treated with the zinc, cobalt and selenium soluble glass bolus (zinc), 105 were treated with a copper, cobalt and selenium soluble glass bolus (copper) and the remaining 105 were untreated (control). Blood samples were collected immediately prior to giving boluses and again after approximately 4 months. These were assessed for zinc (plasma zinc concentration), cobalt (serum vitamin B12 concentration), selenium (erythrocyte glutathione peroxidase activity) and copper status (plasma copper concentration, caeruloplasmin, amine oxidase and superoxide dismutase activity and calculation of the ratio between the caeruloplasmin and plasma copper).

The zinc bolus in both trials significantly increased the plasma zinc concentrations (P < 0·001 and P < 0·01 respectively), erythrocyte glutathione peroxidase activities (P < 0·001) and serum vitamin B12 concentrations (P < 0·001). The copper bolus also significantly increased the erythrocyte glutathione peroxidase activities (P < 0·001) and serum vitamin B12 concentrations (P < 0·001) when compared with the controls but were not significantly different from the zinc group. The copper bolus significantly increased all of the copper status indicators (P < 0·01) when compared with the control and zinc groups. However, in trial 1 when only the zinc and control groups were compared, the zinc bolus significantly increased the ratio (P < 0·001) and serum caeruloplasmin (P < 0·001) and erythrocyte superoxide dismutase (P < 0·01) activities. These responses were not observed in trial 2 with the erythrocyte superoxide dismutase being significantly reduced in the zinc group when compared with the control group (P < 0·001).

The zinc, cobalt and selenium soluble glass bolus increased the status of all three trace elements consistently for a period of at least 100 days. The increases of cobalt and selenium status were similar to those achieved using the copper, cobalt and selenium bolus, which also increased the copper status of the sheep.

In a 25-week experiment beginning at week 3 post partum, grass silages of 10·5 (H) and 8·9 (L) MJ metabolizable energy per kg dry matter (DM) were offered ad libitum to two groups of 24 autumn-calving dairy cows. Within each silage-quality group, two patterns of concentrate allocation were compared, a flat-rate (F) and a variable rate (V). All four treatment groups, HF, HV, LF and LV, received on average 1575 kg fresh weight per cow of a concentrate containing 170 g crude protein per kg during the 25 weeks. The cows on treatment F were all individually given 9 kg concentrate per day throughout. Individuals on the V treatments received different levels of concentrate, based initially on their 14-day milk yield and then reduced by 1 kg/day at 10, 15 and 20 weeks. For treatments HF, HV, LF and LV respectively, mean adjusted daily milk yields were, 24·4, 24·1, 21·6 and 22·1 kg; intakes of silage DM, 9·1, 8·7, 7·6 and 7·6 kg/day, and live-weight gains, 0·39, 0·31, 0·28 and 0·22 kg/day. The effects of silage quality were significant in each case, but the effects of pattern of concentrate allocation were not. Cows given the H silage produced milk with significantly greater lactose and solids-not-fat concentrations. During the residual period (2 weeks indoors and 14 weeks grazing) no significant differences in milk yield were observed. The 305-day yields of 6215, 6096, 5786 and 5824 kg for treatments HF, HV, LF and LV respectively, reflected the differences obtained during the indoor feeding period.

The value of using a marker for a quantitative trait locus (QTL) affecting a sex-limited trait in an outbred poultry breeding nucleus was studied. Marker and QTL were in linkage equilibrium in the base population. The recombination rate between marker and QTL was 0-05. A closed nucleus with 9000 chickens per generation was deterministically simulated. The genetic model contained polygenes and a QTL linked to a marker. Genetic effects explained proportionately 0·3 of the phenotypic variance before selection. Under selection, polygenic variance reached an equilibrium and QTL variance decreased continuously over time. Cocks were selected in two steps. First the best cocks of each full-sib family were selected (within-family selection) while final selection took place after information on fiill-sibs was available. Hens were selected after they had completed production. The effect of using marker information in estimating breeding values was studied in an ongoing breeding programme. Transmission of marker alleles was always traceable. Cumulative response over five generations increased proportionately by 0·06 to 0·13 if a marker linked to a QTL that explained 0·2 of the genetic variance was used. Cumulative response increased up to 0·28 if the QTL explained 0-8 of the genetic variance. Additional response due to the use of a marker increased with increasing intensity of within-family selection of cocks, increased with increasing variance explained by the QTL and was higher if within-family selection of cocks was carried out after rather than before their sibs had complete records.

Piglets in litters reared in groups from 3 to 7 weeks of age weighed less at weaning (7 weeks) than piglets in which litters were penned individually. Some of the difference between the two management systems was created within the week after grouping. Grouping sows and their litters did not initiate oestrus in lactation. The subsequent litter size of the grouped sows was reduced but between-treatment differences for this trait failed to reach significance at the 5% level.

The alpaca fiber diameter (FD) varies from 18 to 36 μm, being the finer fiber categories highly appreciated. However, the alpaca fiber presents some limitations in the textile industry due to the high incidence of fiber medullation and diameter variability, both reduces the comfort feeling of the garments. Decreasing or even removing medullation could be a possible selection objective in alpaca breeding programs for increasing economic value of the alpaca fiber. Therefore, the present work aimed to estimate genetic parameters regarding medullation traits, as well as the genetic correlations with other economical important traits, to be able to select the appropriate criteria to reduce or remove medullation on alpaca fiber and help to reduce the prickle factor in the garments. The data was collected from 2000 to 2017 and belonged to the Pacomarca experimental farm. There were 3698 medullation records corresponding to 1869 Huacaya and 414 Suri genetic types. The fiber samples were taken from the mid side, and were analyzed in an OFDA 100® device. The traits analyzed were percentage of medullation (PM), medullated fiber diameter (MFD), FD, standard deviation of FD, greasy fleece weight as fiber traits; density, crimp in Huacaya and lock structure in Suri, head conformation, leg coverage as morphological traits; weaning weight and age at first calving as secondary and functional traits. Genetic parameters were estimated via a multitrait restricted maximum likelihood. The heritabilities for PM and MFD were 0.225 and 0.237 in Huacaya genetic type and 0.664 and 0.237 in Suri genetic type, respectively; heritabilities for other traits were moderate for productive and morphological traits, and low to moderate for secondary and functional traits. The genetic correlations PM–FD and MFD–FD were high and favorable in both genetic types, between 0.531 and 0.975; the genetic correlation PM–MFD was 0.121 in Huacaya and 0.427 in Suri. The rest of genetic correlations with other traits were in general moderate and favorable. The repeatabilities were 0.556 and 0.668 for PM, and 0.322 and 0.293 for MFD in Huacaya and Suri genetic types, respectively. As a conclusion, PM was identified to be a good selection criterion, probably combined in an index with FD to reduce prickling factor.

A total of 600 Ross 308-day-old male broiler chicks were used in a 28 day digestibility study to investigate the interaction between dietary calcium (Ca) and non-phytate phosphorus (nPP) on the digestibility of minerals and amino acids. Diets were formulated to be nutritionally adequate except for Ca and nPP. Fifteen mash diets based on corn and soya bean meal with varying concentrations of Ca (6.4 to 12.0 g/kg) and nPP (2.4 to 7.0 g/kg) were used. Diets were clustered around total densities of Ca and nPP of 12, 13.5 or 15.0 (g/kg) and within each density, a range of five Ca : nPP ratios (1.14 : 1, 1.5 : 1, 2.0 : 1, 2.75 : 1 and 4.0 : 1) were fed. Birds had free access to feed and water throughout the study. At day 28, birds were euthanised for the determination of apparent ileal mineral and amino acid digestibility. Data were modelled in R version 2.15 using a linear mixed-effects model and interrogation of the data was performed by fitting a low order polynomial function. At high Ca concentrations, increasing nPP led to an increase in the apparent digestibility of minerals. Apparent ileal digestibility of phosphorus (P) was enhanced with increasing dietary nPP up to 5.5 g/kg beyond which no improvements were found. Maximal Ca digestibility was found in diets with >8.0 g/kg Ca with concomitant low concentrations of nPP. Diets with a broader Ca : nPP ratio improved the digestibility of Ca but were deleterious to the digestibility of P. In this study, apparent digestibility of amino acids was broadly unaffected by dietary Ca and nPP concentrations. However, interactions between Ca and nPP were observed for the digestibility of glutamine, tyrosine and methionine (all P<0.001). Nitrogen digestibility showed discrete optima around 10.0 and 5.0 g/kg nPP and Na digestibility was maximised around 8 to 9.0 g/kg Ca and 4.5 to 5.4 g/kg nPP. These data show that the ratio of Ca : nPP is more influential to mineral digestibility than the absolute dietary concentration of each macro mineral.

The beef industry has emphasized the improvement of feed utilization, as measured by modeling feed intake through performance traits to calculate residual feed intake (RFI). Evidence supports an inverse relationship between feed efficiency and reproductive function. The objective of this study was to determine the relationship of reproductive assessments and RFI unadjusted (RFIKoch) or adjusted for body composition (RFIus) and the relationship among fertility-related parameters. In total, 34 crossbred bulls were housed together for 112 days of performance evaluation, followed by assessment of scrotum IR imaging, scrotal circumference, testes ultrasonography and semen quality parameters at 377±33.4 days of age. Bulls were slaughtered at 389±34.0 days of age, and analyses of carcass composition, biometrics and histomorphometry of the testis and epididymis were conducted. Bulls were grouped into two subpopulations based on divergence of RFI, and within each RFI model either by including 50% of the population (Halves, high and low RFI, n=17) or 20.6% extremes of the population (Tails, high and low RFI, n=7). The means of productive performance and fertility-related measures were compared through these categories. Pearson’s correlation was calculated among fertility-related measures. In the Halves subpopulation of the RFIus, sperm of low-RFI bulls had decreased progressive motility (47.30% v. 59.90%) and higher abundance of tail abnormalities (4.30% v. 1.80%) than that of high-RFI bulls. In the Tails subpopulation of the RFIKoch, low RFI displayed less variation in the scrotum surface temperature (0.62°C v. 1.16°C), decreased testis echogenicity (175.50 v 198.00 pixels) and larger (60.90 v. 56.80 mm2) but less-developed seminiferous tubules than high-RFI bulls. The evaluation of fertility-related parameters indicated that a higher percentage of immature seminiferous tubules was correlated with occurrence of sperm with distal droplets (r=0.59), a larger temperature variation at the top of the scrotum was correlated with improved sperm progressive motility (r=0.38), a lower occurrence of sperm loose head abnormalities was correlated with larger temperature variation at the lower part of the scrotum (r=−0.43), and a lower minimum testis echogenicity (r=−0.59) and smaller scrotal circumference (r=0.72) were correlated with age. The adjustment for body composition (RFI determination) enabled distinct biological inferences about reproduction and feed efficiency when compared with the non-adjusted model. However, both RFI models and the correlation analysis supported the hypothesis that feed-efficient bulls have features of delayed sexual maturity. Overall, the assessment of fertility-related measurements is important to avoid the improvement of feed efficiency at the expense of reproductive function in young bulls.

Muscle development in domesticated animals is important for meat production. Furthermore, intramuscular fat content is an important trait of meat intended for consumption. Here, we examined differences in the expression of factors related to myogenesis, adipogenesis and skeletal muscle growth during fetal muscle development of lean (Yorkshire) and obese (Chenghua) pig breeds. At prenatal days 50 (d50) and 90 (d90), muscles and sera were collected from pig fetuses. Histology revealed larger diameters and numbers of myofibers in Chenghua pig fetuses than those in Yorkshire pig fetuses at d50 and d90. Yorkshire fetuses had higher serum concentrations of myostatin (d90), a negative regulator for muscle development, and higher mRNA expression of the growth hormone receptor Ghr (d90), myogenic MyoG (d90) and adipogenic LPL (d50). By contrast, Chenghua fetuses exhibited higher serum concentration of growth hormone (d90), and higher mRNA expression of myogenic MyoD (d90) as well as adipogenic PPARG and FABP4 (d50). Our results revealed distinct expression patterns in the two pig breeds at each developmental stage before birth. Compared with Chenghua pigs, development and maturation of fetal skeletal muscles may occur earlier in Yorkshire pigs, but the negative regulatory effects of myostatin may suppress muscle development at the later stage.

Crossbreeding data involving Ghana Shorthorn, Sokoto Gudali and their Jersey F1s and backcrosses collected over a 16-year period were analysed to estimate additive and heterotic effects for milk production, reproduction and calf growth traits. Sokoto Gudali was significantly better than Ghana Shorthorn in all milk production traits. Calving interval and annualized milk production were better in Gudali than in the Shorthorn. The F1s had higher lactation milk yield, milked longer, produced their first calves earlier and had shorter dry periods and calving intervals than their corresponding purebreds. However, genotype was not significant for number of services per conception. Both F1s had higher average daily gain and weaning weight than their corresponding purebreds. Sokoto Gudali backcross (Jersey × F1) was significantly (P < 0·05) better than the F1 in lactation length. However, in Gudali crosses, there was no advantage in increasing the proportion of Jersey genes beyond 0·5 for milk production traits. Additive effects were significantly (at least P < 0·05) lower in the Shorthorn and the Gudali than in Jersey for milk production traits except proportion of butterfat. Heterosis estimates were significant (P < 0·01) for milk production traits for the Shorthorn but not for the Gudali. Heterotic effects were large and significant (at least P < 0·05) in improving annualized milk production in Shorthorn crosses, whilst none of the heterotic effects for reproductive traits was significant. At both 0 and 0·5 levels of Jersey inheritance, the Gudali was superior (P < 0·01) to the Shorthorn in birth weight, weaning weight and pre-weaning average daily gain. Heterotic effects for calf traits were positive and much larger in Gudali crosses than in Shorthorn crosses. In general, backcrosses were, at best, similar to the F1s implying that upgrading these indigenous breeds beyond 0·5 European inheritance may not be desirable.