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The aim of this experiment was to evaluate the impact of selection for greater muscling on the adrenaline responsiveness of muscle, adipose and liver tissue, as reflected by changes in plasma levels of the intermediary metabolites lactate, non-esterified fatty acids (NEFA) and glucose. This study used 18-month-old steers from an Angus herd visually assessed and selected for divergence in muscling for over 15 years. Ten low muscled (Low), 11 high muscled (High) and 3 high muscled heterozygotes for myostatin mutation (HighHet) steers were challenged with adrenaline doses ranging between 0.2 to 3.0 μg/kg live weight. For each challenge, 16 blood samples were taken between −30 and 130 min relative to adrenaline administration. Plasma was analysed for NEFA, lactate and glucose concentration and area under curve (AUC) over time was calculated to reflect the tissue responses to adrenaline. Sixteen basal plasma samples from each animal were also assayed for growth hormone. Muscle glycogen and lactate concentration were analysed from four muscle biopsies taken from the semimembranosus, semitendinosus and longissimus thoracis et lumborum of each animal at 14, 90 and 150 days on an ad libitum grain-based diet and at slaughter on day 157. In response to the adrenaline challenges, the High steers had 30% lower lactate AUC than the Low steers at challenges greater than 2 μg/kg live weight, indicating lower muscle responsiveness at the highest adrenaline doses. Aligning with this decrease in muscle response in the High animals were the muscle glycogen concentrations which were 6.1% higher in the High steers. These results suggest that selection for muscling could reduce the incidence of dark, firm, dry meat that is caused by low levels of glycogen at slaughter. At all levels of adrenaline challenge, the High steers had at least 30% greater NEFA AUC, indicating that their adipose tissue was more responsive to adrenaline, resulting in greater lipolysis. In agreement with this response, the High steers had a higher plasma growth hormone concentration, which is likely to have contributed to the increased lipolysis evident in these animals in response to adrenaline. This difference in lipolysis may in part explain the reduced fatness of muscular cattle. There was no effect of selection for muscling on liver responsiveness to adrenaline.
Selective breeding is an effective tool to improve livestock. Several selection experiments have been conducted to study direct selection responses as well as correlated responses in traits of skeletal muscle growth and function. Moreover, comparisons of domestic with wild-type species and of extreme breeds provide information on the genetic background of the skeletal muscle phenotype. Structural muscular components that differed with increasing distance in lean growth or meat quality in mammals were found to be myofibre number, myofibre size, proportions of fibre types as well as the numbers and proportions of secondary and primary fibres. Furthermore, markers of satellite cell proliferation, metabolic enzyme activities, glycogen and fat contents, the expression of myosin heavy chain isoforms, of activated AMPKα and other proteins in skeletal muscle tissue and circulating IGF1 and IGF-binding proteins have been identified to be involved in selection responses observed in pigs, cattle and/or chicken. The use of molecular methods for selective breeding of fish has only recently been adopted in aquaculture and studies of the genetic basis of growth and flesh quality traits are scarce. Some of the molecular markers of muscle structure/metabolism in livestock have also been identified in fish, but so far no studies have linked them with selection response. Genome scans have been applied to identify genomic regions exhibiting quantitative trait loci that control traits of interest, for example, muscle structure and meat quality in pigs and growth rate in chicken. As another approach, polymorphisms in candidate genes reveal the relationship between genetic variation and target traits. Thus, in large-scale studies with pigs’ associations of polymorphisms in the HMGA2, CA3, EPOR, NME1 and TTN genes with traits of carcass and meat quality were detected. Other studies revealed the significance of mutations in the IGF2 and RYR1 genes for carcass lean and muscle fibre traits in pigs. Mutations in the myostatin (MSTN) gene in fish were also examined. Advances in research of the genetic and environmental control of traits related to meat quality and growth have been made by the application of holistic ‘omics’ techniques that studied the whole muscle-specific genome, transcriptome and proteome in relation to muscle and meat traits, the development of new methods for muscle fibre typing and the adaptation of biophysical measures to develop parameters of muscle fibre traits as well as the application of in vitro studies. Finally, future research priorities in the field are defined.
High-density single nucleotide polymorphism (SNP) platforms are currently used in genomic selection (GS) programs to enhance the selection response. However, the genotyping of a large number of animals with high-throughput platforms is rather expensive and may represent a constraint for a large-scale implementation of GS. The use of low-density marker (LDM) platforms could overcome this problem, but different SNP chips may be required for each trait and/or breed. In this study, a strategy of imputation independent from trait and breed is proposed. A simulated population of 5865 individuals with a genome of 6000 SNP equally distributed on six chromosomes was considered. First, reference and prediction populations were generated by mimicking high- and low-density SNP platforms, respectively. Then, the partial least squares regression (PLSR) technique was applied to reconstruct the missing SNP in the low-density chip. The proportion of SNP correctly reconstructed by the PLSR method ranged from 0.78 to 0.97 when 90% and 50%, respectively, of genotypes were predicted. Moreover, data sets consisting of a mixture of actual and PLSR-predicted SNP or only actual SNP were used to predict genomic breeding values (GEBVs). Correlations between GEBV and true breeding values varied from 0.74 to 0.76, respectively. The results of the study indicate that the PLSR technique can be considered a reliable computational strategy for predicting SNP genotypes in an LDM platform with reasonable accuracy.
Efficiency of food and nutrient (including energy) use are considered the key factors in the economic and environmental performance of livestock systems. The aim of this paper is to consider the basis of genetic variation in the components that constitute dietary nutrient efficiency; and to conclude whether there would be benefit, in any relevant terms, in including these components in breeding programmes that aim to improve nutrient efficiency within pig and poultry systems of production. The components considered are (i) external, pre-ingestion losses, such as food spillage and its relation to feeding behaviour traits, (ii) digestive efficiency, (iii) maintenance requirements, (iv) net efficiency of energy and nutrient utilisation and (v) partitioning of scarce resources within productive and between productive and fitness functions. It is concluded that opportunities to exploit genetic variation exist mainly in the potential to improve the digestive efficiency of pigs and to reduce the maintenance requirements for resources mainly in hens, but also potentially in pigs. Current evidence suggests that there are very weak genetic and phenotypic correlations between components of feeding behaviour and productive traits, and little genetic variation in the net efficiency of nutrient utilisation among poultry and pig genotypes. The implication of the latter is that there would be little exploitable genetic variation in the partitioning of scarce nutrients between productive functions. Currently, there is a lack of understanding of the genetic basis of the partitioning of scarce nutrients between productive and fitness functions, and how this may impact upon the efficiency of nutrient use in pig and poultry systems. This is an area of research to which further effort might usefully be devoted.
The restrictions on the use of antibiotic and anthelmintic treatments in organic pig farming necessitate alternative non-medical control strategies. Therefore, the antibiotic and parasite-reducing effect of a fructan-rich (prebiotic) diet of dried chicory was investigated in free-ranging piglets. Approximately half of 67 piglets from nine litters were experimentally infected with Ascaris suum and Trichuris suis in the suckling period (1 to 7 weeks of age) and 58 of the piglets were challenged daily with Eschericiacoli O138:F8 for 9 days after weaning to induce weaning diarrhoea. The litters were fed either chicory (30% dry matter) or a control diet. The effect of chicory on intestinal helminths, intestinal microbiota, especially Bifidobacteria and Campylobacter spp. and E. coli post-weaning diarrhoea was assessed. The weight gain of the piglets was not impaired significantly by chicory. The intestinal A. suum worm burden was reduced by 64% (P = 0.034) in the chicory-fed piglets, whereas these same piglets had 63% more T. suis worms (P = 0.016). Feeding with chicory elicited no changes among the main bacterial groups in ileum according to terminal restriction fragment length polymorphism analysis. However, the terminal-restriction fragment (T-RF) 208 bp, which may belong to Lachnospiraceae, was stimulated by the chicory feed (P = 0.03), and T-RF 370 bp that matches Enterobacter belonging to the Enterobacteria was reduced (P = 0.004). In addition, chicory increased the level of Bifidobacteria (P = 0.001) and the faecal Campylobacter excretion level was transitorily reduced in chicory-fed piglets at 7 weeks of age (P = 0.029). Unfortunately, it was not possible to assess the effect of chicory on post-weaning diarrhoea as it did not develop. In conclusion, feeding piglets chicory around the time of weaning caused complex changes of the microbiota and parasite communities within the intestinal tract, and feeding piglets chicory may therefore serve as an animal-friendly strategy to control pathogens.
Affymetrix GeneChip microarrays are a powerful tool to study global gene expression profiles and have been used on many species. However, no sheep-specific Affymetrix GeneChip is currently available and the bovine array is fairly limited in its coverage and annotation. Previously, a probe-selection method based on hybridisation of genomic DNA (gDNA) was developed, which enables GeneChips to be used for species that they were not designed for. This approach can greatly increase the number of potential annotated genes that can be studied beyond that which is currently available, particularly for species that do not have comprehensively characterised genomes. In this study, we demonstrate that gDNA-based probe selection on the Affymetrix Human U133+2 GeneChip array can be used to study gene expression profiles in sheep tissues. More than 20 000 transcripts were detected in triplicate ovine skeletal muscle and liver samples, which is more than would be possible using the commercially available sheep-specific microarray. The majority of the top 15 differentially expressed genes for each tissue were known to either be expressed in a tissue-specific manner or relate to specific functions of that tissue. Gene ontology analysis of the differentially expressed genes revealed the expected differences in gene expression profiles between the two tissues. Besides demonstrating that the probe selection method can be used to study the ovine transcriptome, the benefits of this approach are that it can greatly increase the number of annotated and novel genes that can be studied beyond those currently possible using ovine- or bovine-specific microarrays. This same method also has the potential to allow the study of other species where species-specific microarrays are not available or whose genomes have not been comprehensively characterised.
In certain contexts, dairy firms are supplied by small-scale family farms. Firms provide a set of technical and economic recommendations meant to help farmers meet their requirements in terms of the quantity and quality of milk collected. This study analyzes how such recommendations may be adopted by studying six farms in Brazil. All farms are beneficiaries of the country's agrarian reforms, but they differ in terms of how they developed their activities, their resources and their milk collection objectives. First, we built a technical and economic benchmark farm based on recommendations from a dairy firm and farmer advisory institutions. Our analysis of the farms’ practices and technical and economic results show that none of the farms in the sample apply all of the benchmark recommendations; however, all farms specialized in dairy production observe the main underlying principles with regard to feeding systems and breeding. The decisive factors in whether the benchmark is adopted and successfully implemented are (i) access to the supply chain when a farmer establishes his activity, (ii) a grasp of reproduction and forage production techniques and (iii) an understanding of dairy cattle feed dietary rationing principles. The technical problems observed in some cases impact the farms’ dairy performance and cash position; this can lead to a process of disinvestment. This dynamic of farms facing production standards suggests that the diversity of specialized livestock farmers should be taken into account more effectively through advisory approaches that combine basic zootechnical training with assistance in planning farm activities over the short and medium term.
Colour is an important quality parameter of broiler meat influencing the consumer buying behaviour. The alterations of the colour after slaughter are related to the oxidative status of the tissue. This in turn is influenced by an interaction between the mitochondria and the antioxidative enzymes. In this study, breast muscles were collected from hens and cocks of a commercial line slaughtered at the ages of 28 and 41 day. Analysis of the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) was performed with samples obtained 20 min and 48 h after slaughter (post mortem, p.m.), whereas the mitochondrial respiratory activity was analysed in permeabilised breast muscle fibres collected 20 min p.m. The carcass characteristics of breast muscle and leg weight as well as breast yield were significantly higher, and the leg yields lower, in the 41-day-old broiler. The 28-day-old hens and cocks had comparable carcass characteristics (P > 0.05), whereas 41-day-old cocks had significantly higher carcass, breast and leg weight in comparison to the hens. The pH20 min p.m. and the L*48 h p.m. were significantly higher, and the a* and b* values of the 20 min and 48 h p.m. samples as well as the drip loss were significantly lower in the 41-day-old broiler. Mitochondrial respiratory rates were comparable (P > 0.05) between the 28- and 41-day-old cocks and hens. The same result could be found with regard to the activities of the SOD, GPx and GR except for lower activities of the SOD20 min p.m. and higher of the GR48 h min p.m. in the 41-day-old broiler. The concentrations of thiobarbituric acid-reactive substances were generally higher in the breast muscles of the 41-day-old broiler. Assorting the data according to their mean pH20 min p.m. indicates a positive influence of higher pH values (>6.34) on the mitochondrial function, whereas a low pH20 min p.m. results in tendentially and significantly higher activities of the antioxidative enzymes and drip loss values. These results indicate a relation between the meat quality and the oxidative metabolism as well as antioxidative capacity of the meat.
The aim of this study was to test for the existence of causative genetic variation affecting body composition traits within or adjacent to the porcine insulin-like growth factor 2 (IGF2) gene beyond the known IGF2-intron3-G3072A mutation. A focussed quantitative trait loci analysis using four microsatellite markers within the telomeric region of porcine chromosome 2p was conducted in a large resource population comprising 2741 F2 offspring. The analysis of two subsets of animals that were alternatively homozygous for the in3G3072A mutation provides evidence for additional genetic variation significantly contributing to the overall quantitative trait nucleotide variance within our population.
Lamb mortality remains a significant welfare and economic issue for sheep production. Lamb survival is to a degree dependent upon an easy delivery and the expression of appropriate behaviours from both mother and offspring, such as rapid standing, udder seeking and sucking by the lamb. Genetic solutions have the potential to improve birth assistance and lamb behaviour but large amounts of data are needed. Therefore, to achieve this objective, simple, proxy methods (scoring systems) were developed to quantify the level of birth difficulties and lamb vigour on farm. In the first study, detailed historical behavioural data from 1156 lambs (Scottish Blackface and Suffolk (S)) were analysed to develop criteria for 3 scores: birth assistance, lamb vigour and sucking assistance. The birth assistance score was developed by analysing the relationships between birth presentation and intervention levels, and intervention level and labour length. Lambs with abnormal birth positions required more assistance than normally presented lambs and lambs with long labours required more and greater assistance than those with short labours. Lamb vigour score was developed by analysing the latencies for the lamb to first perform specific behaviours; more vigorous lambs reach landmark behaviours faster than low vigour lambs. The sucking assistance score was developed from the relationship between the latency to suck successfully and assistance level, where lambs that were slow to suck required more assistance than lambs that were quick to suck. In the second study, the behaviour scoring systems (5-point categorical scales) were validated using a commercial flock of 80 twin-bearing crossbred ewes mated with either Texel (T) or S sires by simultaneously recording scores and the latency to perform specific landmark behaviours (i.e. to stand, seek the udder and suck). The vigour scores (recorded at 5 min of age) were compared with the latency from birth to standing and showed that lambs with lower (better) vigour scores were faster to stand after birth than those with higher scores. The sucking assistance scores were compared with the latency from birth to sucking, and showed that lambs with lower sucking assistance scores are quicker to suck than those with high scores. These results showed that the scoring systems could provide a practical and reliable assessment of birth assistance and lamb behaviour on farm and were sufficiently sensitive to discriminate vigour levels between lambs sired by either S or T rams.
Meat yield and quality are closely related to muscle development. The muscle characteristics mainly take place during embryonic and postnatal phases. Thus, genetic control of muscle development in early stages represents a significant stake to improve product quality and production efficiency. In bovine, several programmes have been developed to detect quantitative trait loci (QTL) affecting growth, carcass composition or meat quality traits. Such strategy is incontestably very powerful yet extremely cumbersome and costly when dealing with large animals such as ruminants. Furthermore, the fine mapping of the QTL remains a real challenge. Here, we proposed an alternative approach based on chemical mutagenesis in the mouse combined with comparative genomics to identify regions or genes controlling muscle development in cattle. At present, we isolated seven independent mouse lines of high interest. Two lines exhibit a hypermuscular phenotype, and the other five show various skeletomuscular phenotypes. Detailed characterisation of these mouse mutants will give crucial input for the identification and the mapping of genes that control muscular development. Our strategy will provide the opportunity to understand the function and control of genes involved in improvement of animal physiology.
A total of 48 female pigs (Large White × Landrace × Duroc cross) were used to determine whether a compensatory feed regime influenced performance, carcass composition and the level of plasma IGF-1. Pigs of initial age 73 days were fed a commercial diet at 0.70 of ad libitum (R) for 40 days followed by a return to ad libitum feeding for a further 42 days. The control group was fed ad libitum (A) throughout. Groups of animals on R and A feed regimes were slaughtered at the end of restriction period (SL1), 2 days after refeeding ad libitum (SL2) to establish the more immediate effects of refeeding on IGF levels, and after 42 days refeeding (SL3; n = 8 for each group). As expected, during the restriction period, average daily live weight gain in all the slaughter groups of R pigs was significantly lower than A pigs (P < 0.01); there was no significant difference in feed conversion ratios. In the re-alimentation period of SL3, R pigs grew 12.9% faster (P = 0.033), indicating compensatory growth. At SL1, there was a trend for carcass weight (P = 0.108) of A pigs to be higher than R pigs, but at SL2 live weight and carcass weight of A pigs were significantly heavier than R pigs (P < 0.05), but not at SL3. For killing-out percentage, there was no difference in SL1. After refeeding for 2 days (SL2) and 42 days (SL3), R pigs had significantly lower killing-out percentage than A pigs (P < 0.05). As a proportion of live weight, R pigs had smaller heart, kidney and liver (P < 0.05) than A pigs at SL1. At SL2, only the kidney was smaller in the restricted group (P < 0.05) and there were no significant differences in SL3. As a proportion of carcass weight, Longissimus dorsi was heavier in the R pigs at SL1 (P = 0.108) and SL2 (P < 0.05), but not at SL3. At SL1, there was a trend for intramuscular fat of A pigs to be higher than R pigs. The plasma IGF-1 level was lower in R pigs than A pigs (P = 0.010) at SL1, and slightly lower at SL2 (P = 0.110), with no significant differences at SL3. Dietary restriction period influenced plasma IGF-1 levels, which returned to the ad libitum group levels when animals were refed, as did live weight and carcass weight. It appears that the internal organs and possibly fat, but not muscles, underwent a compensatory response when animals were refed.
An empirical regression model for the prediction of total dry matter intake (DMI) of dairy cows was developed and compared with four published intake models. The model was constructed to include both animal and dietary factors, which are known to affect DMI. For model development, a data set based on individual cow data from 10 change-over and four continuous milk production studies was collected (n = 1554). Relevant animal (live weight (LW), days in milk (DIM), parity and breed) and dietary (total and concentrate DMI, concentrate composition, forage digestibility and fermentation quality) data were collected. The model factors were limited to those that are available before the diets are fed to animals, that is, standardized energy corrected milk (sECM) yield, LW, DIM and diet quality (total diet DMI index (TDMI index)). As observed ECM yield is a function of both the production potential of the cow and diet quality, ECM yield standardized for DIM, TDMI index and metabolizable protein concentration was used in modelling. In the individual data set, correlation coefficients between sECM and TDMI index or DIM were much weaker (0.16 and 0.03) than corresponding coefficients with observed ECM (0.65 and 0.46), respectively. The model was constructed with a mixed model regression analysis using cow within trial as a random factor. The following mixed model was estimated for DMI prediction: DMI (kg DM/day) = −2.9 (±0.56)+0.258 (±0.011) × sECM (kg/day) + 0.0148 (±0.0009) × LW (kg) −0.0175 (±0.001) × DIM −5.85 (±0.41) × exp (−0.03 × DIM) + 0.09 (±0.002) × TDMI index. The mixed DMI model was evaluated with a treatment mean data set (207 studies, 992 diets), and the following relationship was found: Observed DMI (kg DM/day) = −0.10 (±0.33) + 1.004 (±0.019) × Predicted DMI (kg DM/day) with an adjusted residual mean square error of 0.362 kg/day. Evaluation of the residuals did not result in a significant mean bias or linear slope bias, and random error accounted for proportionally >0.99 of the error. In conclusion, the DMI model developed is considered robust because of low mean prediction error, accurate and precise validation, and numerically small differences in the parameter values of model variables when estimated with mixed or simple regression models. The Cornell Net Carbohydrate and Protein System was the most accurate of the four other published DMI models evaluated using individual or treatment mean data, but in most cases mean and linear slope biases were relatively high, and, interestingly, there were large differences in both mean and linear slope biases between the two data sets.
Little is known about the characteristics of biters and victims before the appearance of a tail-biting outbreak in groups of pigs. This study aimed to characterise biters and victims (according to gender and performance) and to quantify their behavioural development during the 6 days preceding the tail-biting outbreak. The hypotheses tested were: (a) biters are more often female, are the lighter pigs in the group, are more restless and perform more aggressive behaviour; and (b) victims are more often male, heavier and less active. Using video recordings we carried out a detailed study of 14 pens with a tail-biting outbreak among the weaned piglets. All piglets were individually marked and we observed the behaviour of biters, victims and control piglets (piglet types). In every pen, each piglet type was observed every other day from 6 days before (D−6) to the day of the first visible tail damage (i.e. day of tail biting outbreak; D0). While the number of male biters (6 of the 14 biters) and male victims (11 of the 14 victims) was not significantly different (P = 0.13), this numerical contrast was considerable. The start weight of victims was significantly (P = 0.03) higher (8.6 kg) than those of biters (7.5 kg) and control piglets (8.0 kg). Biters tended (P = 0.08) to spend longer sitting/kneeling (3.1 min/h) than controls (1.7 min/h), but no differences were seen in the time spent lying or standing. Victims tended (P = 0.07) to change posture more often (restlessness) than controls and chased penmates more (P = 0.04) than biters. Victims also performed more (P = 0.04) aggressive behaviour than biters and controls. In contrast, biters tended (P = 0.08) to be chased by penmates more often and tended (P = 0.06) to receive more aggressive behaviour than controls. Furthermore, biters spent longer manipulating the enrichment device (P = 0.01) and the posterior/tail (P = 0.02) of their penmates than controls and tended (P = 0.06) to perform more tail bites than victims. Victims received more posterior/tail manipulation (P = 0.02) and tail bites (P = 0.04) than controls. It was also noticed that, independent of piglet type, restlessness (P = 0.03) increased and the frequency of performed tail bites tended (P = 0.08) to increase in the 6 days preceding a tail-biting outbreak. These findings may contribute to the early identification of biters or victims and support the development of strategies to minimise the occurrence of tail biting.
Seven- to 10-month-old calves are the typical production of Galician Blond (GB), the most important bovine local beef breed in Spain. As meat lipid repercussions on human health depend on their fatty acid (FA) profile, this study aimed at analysing the individual FA at weaning and at the end of the feeding finishing period, especially trans and cis 18:1 isomers in total lipids of the Longissimus thoracis muscle in GB male calves. Distribution of main FA in veal lipids was characterized by gas–liquid chromatography (GLC) analysis on a high polar glass capillary column. Total trans and cis 18:1 isomers were purified, from total FA (TFA) methyl esters, by preparative reversed-phase high-performance liquid chromatography, to allow subsequent specific analysis of their different isomers by GLC. Calves stayed with their mothers at pasture for 2 or 5 months in intensive or semi-extensive systems, followed by an indoor feeding period. The weaned (W) group was finished on concentrate and hay, whereas the non-weaned (NW) group was finished on concentrate and hay and it continued suckling until slaughter. The studied effects did not present interactions. The duration of the indoor finishing period hardly had a significant influence on the parameters analysed. Compared to W calves, NW calves had higher proportions (% TFA) of 18:3n-3 (+38%, P < 0.0001), 20:5n-3 (+22%, P = 0.005), 22:5n-3 (+13%, P = 0.042), cis monounsaturated FA (MUFA; +8%, P = 0.032), total MUFA (+8%, P = 0.013), n-3 polyunsaturated FA (PUFA; +25%, P = 0.0001) and conjugated linoleic acid (CLA; +48%, P < 0.0001) to the detriment of 18:0 (−10%, P = 0.002), 18:2n-6 (−25%, P = 0.004) and n-6 PUFA (−20%, P = 0.011). With regard to cis and trans 18:1 isomers, NW calves had higher proportions (% total cis or trans 18:1) of Δ11trans and Δ16trans (+25% and +22%, respectively, P < 0.01) and Δ13 + 14trans (+13%, P < 0.05) and lower proportions of Δ6 to 8 and Δ10trans (−28% and 58%, respectively, P < 0.001). NW calves’ meat might be more suitable for human health than W calves’ meat due to the increase of anti-atherogenous FA such as n-3 PUFA, CLA and 18:1 Δ11trans.
This study investigates the myosin heavy chain (MyHC) isoform composition in the gluteus medius muscle of the Akhal-Teke horses using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). Fifteen horses aged between 1.5 and 23.5 years were used in this study and divided into three age groups: 1.5 to 4 (n = 6), 9 to 13 (n = 5) and 18.5 to 23.5 years (n = 4). The average content of the MyHC I isoform was 11.72 ± 1.07% (variation between individuals: 7.09% to 20.14%). The relative content of the MyHC IIa and IIx isoforms was subsequently 38.20 ± 1.46% (30.73% to 48.78%) and 50.07 ± 1.10% (43.8% to 56.78%) from the total MyHC. The MyHC pattern in the skeletal muscles of the Akhal-Teke horses shows that the muscles of these horses have a high capacity both for endurance and speed.
In mammals, maternal food restriction around conception and during pregnancy results in low birth weight and an adjusted growth trajectory of offspring. If, subsequently, the offspring are born into a food-abundant environment, they are at increased risk of developing obesity, type 2 diabetes, hypertension and renal dysfunction. Here, we show similar effects of maternal undernutrition on hatch weight, growth and fat deposition in offspring of birds (domestic chicken). Both mothers and offspring were fed either ad libitum or restricted in a two-by-two factorial design, resulting in two matched and two mismatched maternal–offspring nutritional environments. Offspring of ad libitum mothers grew heavier than those of restricted mothers, possibly due to the larger muscle mass. Ad libitum-fed offspring, especially females, of restricted mothers were lighter at hatch, and were heavier and had more abdominal fat at 6 weeks of age than daughters of ad libitum-fed mothers. These results suggest a common mechanism in mammals and birds in response to a mismatch in the maternal–offspring nutritional environment. They also indicate that the common practice of restrictive feeding of the broiler breeders and subsequent ad libitum feeding of the broilers may result in reduced growth and increased abdominal fat as compared to broilers of less restricted broiler breeders.
The objective of this study is to quantify the milk production response per cow and per hectare (ha) for an incremental stocking rate (SR) change, based on a meta-analysis of published research papers. Suitable experiments for inclusion in the database required a comparison of at least two SRs under the same experimental conditions in addition to details on experimental length and milk production results per cow and per ha. Each additional increased SR treatment was also described in terms of the relative milk production change per cow and per ha compared to the lower base SR (b_SR). A database containing 109 experiments of various lengths with 131 comparisons of SR was sub-divided into Type I experiments (common experimental lengths) and Type II experiments (variable experimental lengths). Actual and proportional changes in milk production according to SR change were analysed using linear mixed model procedures with study included as a random effect in the model. Low residual standard errors indicated a good precision of the predictive equations with the exception of proportional change in milk production per cow. For all milk yield variables analysed, the results illustrate that while production per cow is reduced, a strong positive relationship exists between SR and milk production per ha. An SR increase of one cow/ha resulted in a decrease in daily milk yield per cow of 7.4% and 8.7% for Type I and Type II data, respectively, whereas milk yield per ha increased by 20.1% and 19.6%, respectively. Within the Type II data set, a one cow/ha increase in SR also resulted in a 15.1% reduction in lactation length (equivalent to 42 days). The low predictability of proportional change in milk production per cow according to the classical SR definition of cows per ha over a defined period suggests that SR may be more appropriately defined in terms of the change in available feed offered per animal within each treatment.