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Genomic Insights Into Heterosis: Dominance or Additive × Additive Interaction?

Heterosis was documented in the 18th century, but its biological basis has been debated since. The theoretical framework proposed by Hill, and adapted by Lynch, is based on two central parameters: admixed composition (S), and the heterozygosity (H). Using genomic information, it is now possible to estimate independently the individual realized Si and Hi. In this research, a methodology for estimating the contribution of dominance and additive &#xd7; additive effects to heterosis is proposed. This approach would be especially relevant in cases where there is insufficient phenotypic information available, or an adequate genetic group experimental design, common in humans, wild species and other admixed populations. We also provide theoretical arguments highlighting the enhanced precision of the estimations of heterosis parameters through this method. Furthermore, we exemplify this procedure by analysing data from an experimental F2 pig population, which was initially designed for QTL mapping. Notably, all animals in this population were genotyped (including F1 and parental breeds), but phenotypic information was only available for F2 individuals and included 13 traits related to growth, fat deposition, carcass characteristics and meat quality. Significant additive effects (p&#x2009;<&#x2009;0.05) were detected for longissimus muscle area and carcass temperature, suggesting complementary additive effects for these traits. Significant dominance and additive &#xd7; additive effects were also detected for birth weight and carcass length, respectively (p&#x2009;<&#x2009;0.05), indicating that heterosis for these traits is primarily attributable to dominance and additive &#xd7; additive interactions. These results demonstrate that the proposed methodology can successfully estimate the genetic components underlying heterosis and underscores the utility of this approach in&#xa0;situations where we possess genomic data but limited phenotypic data.

SNP

[Nutritive antibiotics and biostimulant preparations in the rations of swine for fattening].

Two experiments were carried out with sows for fattening having a body weight of 20 to 100 kg. The following nutritive antibiotics were tested -- bacipharmin -- 10% (PRB), zinkbacitracin -- 10% (UFRJ), vitamycin 3 (USSR), nitrovin (Peizun, USA) and mekadox -- 5% (USA). It was established that the stimulating effect of these antibiotics was manifested during the first fattening period -- up to 60 kg body weight, when the average daily increment of the experimental groups treated with bacipharmin, zink bacitracin and nictrovin in the I experiment was 7--15% higher and in the II experiment in which zink bacitracin, vitamycin 3, nitrovin and mekadox were added -- 8--14% higher as compared to the control groups. During the second period of fattening (60--100kg) no effect of the same nutritive antibiotics was observed, with the exception of the vitamycin treated group. In both experiments an economy of combined fodder per 1 kg body weight was realized in the experimental groups. Application of nutritive antibiotics and biostimulators during the second period is economically unexpedient. The antibiotics tested have no negative effect on carcass slaughter characteristics and on the chemical composition of meat. No residual substances of the nutritive antibiotics tested were detected on the second day following slaughter in the meat group treated with mekadox, since no sows of this group were slaughtered.

Animal Feed

Associations between gut microbiota on carcass traits and meat quality in Neijiang pigs, Yorkshire pigs, and their hybrids.

This study was designed as an exploratory analysis to compare carcass performance, meat quality traits, and gut microbiota of Neijiang pigs (NN), Yorkshire pigs (YY), and Yorkshire &#xd7; Neijiang hybrid pigs (YN), with the goal of generating testable hypotheses regarding potential links between gut microbial composition and production phenotypes. Compared with NN pigs, YN hybrids exhibited improved carcass performance while inheriting the favorable meat quality characteristics of Neijiang pigs. The results of 16S rRNA sequencing analysis showed that the relative abundance of the microbiota was similar to that of NN pigs. LDA effect size (LEfSe) results showed that Streptococcus, Treponema, probable_genus_10 and Fibrobacter were the differentially enriched taxa in YN pigs (p < 0.05). Correlation analysis was performed on carcass, meat quality and intestinal microbiota screened out by LEfSe. The results showed that Akkermansia tended to positively associate with body length and oblique length in YN pigs; Dialister correlated positively with dressing rate and pH45min; Treponema showed positive trends with a*45min and a*24h (p < 0.05). Finally, the correlation network model preliminarily mapped associations among production traits, gut microbiota, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for exploratory screening. Nine core microbial taxa exhibited close correlations with phenotypic indicators, which implied that these microbes might modulate metabolic pathways to shape pig performance. Overall, hybrids inherited superior parental carcass and meat quality but harbored unique gut microbial communities relative to purebreds-these preliminary correlative observations generate new hypotheses that gut microbiota may contribute to heterosis-associated phenotypic advantages, which require further targeted validation.

Animals

Experimental feeding of DDE and PCB to female big brown bats (Eptesicus fuscus).

Twenty-two female big brown bats (Eptesicus fuscus) were collected in a house attic in Montgomery County, Maryland. Seventeen were fed mealworms (Tenebrio molitor larvae) that contained 166 ppm DDE; the other five were fed uncontaminated mealworms. After 54 days of feeding, six dosed bats were frozen and the remaining 16 were starved to death. In a second experiment, 21 female big brown bats were collected in a house attic in Prince Georges County, Maryland. Sixteen were fed mealworms that contained 9.4 ppm Aroclor 1254 (PCB). After 37 days, two bats had died, four dosed bats were frozen, ant the remaining 15 were starved to death. Starvation caused mobilization of stored residues. After the feeding periods, average weights of all four groups (DDE-dosed, DDE control, PCB-dosed, PCB control) had increased. However, weights of DDE-dosed bats had increased significantly more than those of their contols, whereas weights of PCB-dosed bats had increased significantly less than those of their controls. During starvation, PCB-dosed bats lost weight significantly more slowly than controls. Because PCB levels in dosed bats resembled levels found in some free-living big brown bats, PCBs may be slowing metabolic rates of some free-living bats. It is not known how various common organochlorine residues may affect metabolism in hibernating bats. DDE and PCB increased in brains of starving bats as carcass fat was metabolized. Because the tremors and/or convulsions characteristic of neurotoxicity were not observed, we think even the maximum brain levels attained (132 ppm DDE, 20 ppm PCB) were sublethal. However, extrapolation of our DDE data predicted lethal brain levels when fat reserves declined sufficiently. PCB-dosed bats were probably in no danger of neurotoxic poisoning. However, PCB can kill by a nonneurotoxic mode, and this could explain the deaths of two bats on PCB dosage.

Animals

[The post mortem alterations of myofibrilar proteins and adenosintriphosphatase activities of the skeletal muscles (author's transl)].

Immediately after the death of rabbits and at different times within 48 hours, we took out a part of the psoas muscle, from which we made myofibrilar preparations. The carcasses providing the muscle samples were held at two different temperatures. One group was held for 48 hours at 25 degrees C, imitating room temperature. The other group was held for 12 hours at 25 C degrees and at 25 C degrees and 12 hours at 10 C degrees, imitating daily temperature changes. Each myofibrilar sample was subjected to SDS-polyacrylamide gel electrophoresis. In addition we determined the Ca++ activated and the EGTA inhibited ATPase specific activity of the myofibrils. We found that within 48 hours the myofibrilar proteins were subjected to some characteristic proteolytic changes, which were dependant on the environmental temperature. The most interesting change was found in carcasses held constantly at 25 C degrees for 48 hours, where the EGTA inhibited ATPase activity was increased to about seven times its initial value, reflecting impairment of the troponin complex.

Actinin

Control of glycogen metabolism in the developing turkey poult.

An experiment was conducted with young turkey poults to evaluate factors controlling glycogen metabolism in the period following hatching. Glucose and sucrose solutions were given along with a standard starter diet. Liver and carcass glycogen were measured on days 1, 4 and 6. Liver glycogen synthetase (EC 2.4.1.21) and phosphorylase (EC 2.4.1.1) were also assayed at these times. The characteristics of active and inactive glycogen synthetase at these times were determined and sensitivity of the active and inactive forms were related to physiological concentrations of glucose-6-phosphate. Supplemental glucose or sucrose increased carcass glycogen in comparison to controls; however, but sucrose was more effective than glucose in promoting liver glycogen synthesis in 4- and 6-day-old poults. There was an age dependent increase in carcass glycogen between days 1 and 6, but a decrease in liver glycogen between days 4 and 6. The activation of liver glycogen synthetase is incomplete in 1 day old poults but activity increases during the 1st week of life. Activation of glycogen synthetase decreased the apparent Ka for glucose-6-phosphate. Phosphorylase inactivation in vitro was not affected by age. Liver glucose-6-phosphate increases rapidly after hatching and the concentration is related to the in vitro Ka derived for both active and inactive synthetases. Both glucose and sucrose increased liver glucose-6-phosphate at days 4 and 6 as well as glycogen synthetase activity. The increase in enzyme activity may be caused indirectly by an allosteric effect of glucose-6-phosphate. Phosphorylase, while not affected by supplemental carbohydrates, did decrease in activity between days 4 and 6. The decrease in activity could affect the phosphorylase a/ synthetase a ratio and change glycogen metabolism.

Aging

[Staphylococcus aureus in poultry--biochemical characteristics, antibiotic resistance and phage pattern (author's transl)].

In a poultry processing plant in northern Germany 1412 swabs were taken from poultry carcasses together with 608 swabs from the personnel. The broilers came from 22 different chicken farms. The swabs taken from the poultry and those taken from the personnel proved to be 35% and 48% Staph. aureus positive respectively. The swabs taken from the feathers and from the skin were staphylococcal positive at a higher level (47%) than the swabs taken from the cloaca (19%) and the throat (23%). Between 8% and 63% of the animals from the various chicken farms were Staph. aureus positive. The frequency of staphylococcal contamination increased during the course of slaughter. 57% of the swabs taken from the gloves and the hands and 42% from the aprons of the personnel were Staph. aureus positive. Some biochemical properties, the phage patterns, and the antibiotic resistance against oleandomycin, erythromycin, bacitracin, streptomycin, tetracyclin, penicillin, chloramphenicol, virginiamycin and flavomycin were determined from 445 poultry and 345 personnel Staph. aureus isolates. Only small differences could be established between both sources in this way. Only 20% of the personnel and 34% of the chicken strains were resistant to antibiotics. In the strains collected from personnel, penicillin-resistance predominated while the poultry isolates showed predominantly tetracyclin-resistance. Of all antibiotics applied nutritively in the chicken fattening, there was a higher resistance only against oleandomycin (11% of the poultry strains). Between the chicken farms there was a different frequency of resistance (0--68%). The source of the staphylococci could be determined for only some of the strains. Only 2.5% of the chicken isolates showed characteristics described in the literature to be "poultry-specific", whereas 37% of the personnel and 24% of the poultry isolates were shown to be "human-specific" strains. It seems that the vast majority of the staphylococci originated from the slaughterhouse personnel. The rest of the strains differed in varying combinations of their properties from the given species characteristics. Although Staph. aureus was brought into the slaughterhouse by the poultry, the contaminations of the final product seemed to originate mainly from human beings.

Abattoirs

Sources of potential residue problems in dairy herds.

Drugs and chemicals provide economic benefit to animal and crop production; to derive this benefit they must be used appropriately. Data from the United States Department of Agriculture, Food Safety and Quality Service residue monitoring program indicates certain drugs and chemicals are not being used appropriately by the dairy industry, and residues are occurring in cow carcasses at slaughter. Residues of antibiotics and certain pesticides which are administered intentionally are being found. Dairy cows are also particularly susceptible to inadvertant exposure to chemicals because of certain management practices and physiologic characteristics of dairy cows. Contamination of Michigan dairy cows with polybrominated biphenyls is an example. Methods of controlling both intentional and unintentional exposure of cows to drugs and chemicals will require considerable involvement of producers.

Animals

Characteristics of thyroid function in experimental protein malnutrition.

Two experiments were conducted to study the effects of protein malnutrition on thyroid function. Resting oxygen consumption and serum concentrations of triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) were measured and correlated with thyroid histology, gain in weight, feed efficiency and carcass energy content in male rats fed isoenergetic diets ad libitum containing 22% (control) or 8% (protein malnourished, PM) casein for 28 or 32 days postweaning. A third group was pair-fed to the PM rats with the control diet. In experiment 2 additional groups were pair-fed to the PM rats with 8% casein diets in which the casein was substituted with different mixtures of carbohydrate and fat. Resting oxygen consumption/body weight (0.75) decreased as body weights increased in all groups, but was consistently greatest in PM rats. In PM rats, plasma T3 was 130% of controls after 11 days of the dietary regimen and averaged 215% of controls from days 18 through 32. In experiment 2 both T3 and T4 concentrations were approximately twice controls in all PM groups. TSH concentrations were within the normal range in all groups throughout. Feed efficiency averaged 36 to 40% of controls and mean weight gain was 30 g after 28 days in the PM groups, compared to 114 and 91 g, respectively, in the pair-fed control rats. Carcass energy content of PM rats after 28 days was significantly lower than in control or pair-fed control rats. Thyroid morphology was compatible with increased secretory activity in all the protein-malnourished groups, compared with normal activity in the control and pair-fed control groups. Thermogenesis, as measured by oxygen consumption, was markedly increased in the PM rats compared to controls. These observations are consistent with a diet-induced thermogenesis in the protein-malnourished rats. In contrast to simple under-nutrition where energy expenditure may be conserved by decreases in thyroid function and thermogenesis, increases in thyroid function and thermogenesis in protein malnutrition could provide an energy balancing mechanism whereby unneeded non-protein energy in the diet could be dissipated as heat, and survival enhanced.

Animals

[Investigations concerning the use of the rumen fermentation regulator monensin in feeding fattening bulls].

In two digestion experiments with wethers and seven feeding experiments with 198 fattening bulls with rations rich in (greater than 55% of the dry matter intake from roughage), the influence of the antibiotic monensin on the digestibility of the ration, on rumen-physiologic characteristic values and on fattening and slaughtering results was investigated. The digestibility of the organic matter and the crude nutrients was not significantly influenced by the use of monensin (20 mg/kg dry matter). The administration of 200 mg monensin per fattening bull and day resulted in an increase of the molar concentration of propionate in the rumen fluid by 9.7 mol%, the concentration of acetate and butyrate decreased by 7.3 resp. 2.8 mol %. On an average of the seven experiments the intake of dry matter was diminished by 5.1% through the use of monensin, the live weight increase remained almost unaffected (3.0% additional increase), feed and energy requirement per kg live weight were improved by 7.9%. The fattening results do not always correspond in the various experiments. The results of the dressing of the carcass, the composition of the carcass and the quality of the meat remained unaffected by the administration of monensin.

Animal Nutritional Physiological Phenomena