Phylogenetic analysis of ORF5 and ORF7 of porcine reproductive and respiratory syndrome (PRRS) virus and the frequency of wild-type PRRS virus in México.

Porcine reproductive and respiratory syndrome (PRRS) is caused by a genetically diverse RNA virus and is an economically significant disease in the swine industry. In this study, a total of 8,126 serum samples were obtained from 275 technified and semi-technified farms belonging to 30 of the 32 states of Mexico and representative of the eight regions of the country. Anti-PRRSv antibodies against the PRRS vaccine and an isolated wild Mexican virus were tested by ELISA. Antibodies were found in 15%-49% of the tested sera, with 2.4%-9.8% against the vaccine and 7.7%-26% against the wild virus. The PRRSv virus was detected by RT-PCR in 77 of the 1,630 pooled samples tested, representing seven of the eight geographic regions into which the Mexican Republic is divided. The complete sequences of open reading frames 5 and 7 from 20 PRRSv-positive samples were determined. The analysis of the sequences together with the previously published sequences of historic strains revealed that all the strains belonged to the one, five and eight lineages of the PRRSV2. Striking differences, particularly in ORF5 and ORF7, were found between sequences of the strains and the reference virus, due to insertions and substitutions in positions that play key roles in the recognition, structure and function of the virus. Overall, these results established the magnitude of PRRS virus genetic diversity, and the most frequent virus strain that predominates in Mexico. The PRRSV2 is presented in the porcine population of Mexico; the circulating strains have important changes in ORF5 and ORF7, which probably explain the results obtained in the serological analysis of the wild virus and vaccine strains.

Reduction in the mRNA expression of sVEGFR1 and sVEGFR2 is associated with the selection of dominant follicle in cows.

The vascular endothelial growth factor (VEGF) is essential for follicular development by promoting follicular angiogenesis, as well as for the proliferation and survival of granulosa cells. The biological effects of VEGF are regulated by two membrane receptors, VEGFR1 and VEGFR2, and two soluble receptors, sVEGFR1 and sVEGFR2, which play an antagonistic role. Thus, the objective of this study was to identify the mRNA expression pattern of total VEGF, VEGFR1, VEGFR2, sVEGFR1 and sVEGFR2 in bovine preselected follicles (PRF) and post-selected follicles (POF). The mRNA expression of these five genes in both granulosa cells (GC) and theca cells (TC) was compared between follicles classified as PRF and POF based on their diameter and on their ratio of estradiol/progesterone (E2/P4). Results showed a lower expression of mRNA of sVEGFR1 and sVEGFR2 in POF than in PRF (p < .05). Regarding the mRNA expression of total VEGF, VEGFR1 and VEGFR2, there was no difference between POF and PRF follicles (p > .05). Our results showed that the mRNA expression of VEGFR2 and sVEGFR1 was more abundant than the expression of VEGFR1 and sVEGFR2, while GC was the main source of mRNA for total VEGF. On the other hand, TC was the follicular compartment where the receptors were most expressed. Our results suggest that non-dominant follicles maintain a greater concentration of the mRNA expression of both membrane and soluble VEGF receptors. On the other hand, follicular dominance is related to a reduction in the mRNA expression of sVEGFR1 and sVEGFR2, which may favour VEGF binding with VEGFR2 and, hence, improve the follicular health and development.

Serological survey of veterinarians to assess the zoonotic potential of three emerging swine diseases in Mexico.

We conducted an immunological assay of blood samples taken from 85 swine-specialist veterinarians attending the Congress of the Mexican Association of Swine Specialist Veterinarians in Mexico in 2011. Serum samples were assayed for Porcine rubulavirus (PorPV), Encephalomyocarditis virus (EMCV) and Leptospira spp. antibodies. Using a hemagglutination inhibition test, we registered 2.3% and 27% seropositivity for PorPV and EMCV, respectively. Using viral neutralization tests, we registered 5.8% and 47% seropositivity for PorPV and EMCV, respectively. For Leptospira spp., we registered a seropositivity of 38.8%. The variables (sex, age, years of exposure, number of visited farms, biosecurity level and region) showed no significant effect (P > 0.05) on the seropositivity for EMCV, PorPV and Leptospira spp. except for number of visited farms on HI seropositivity for EMCV (P < 0.05; odds ratio: 1.38). The data obtained provide information on the epidemiology of emerging diseases with zoonotic potential in occupational risk groups.

Percentage of ubiquitinated spermatozoa does not correlate with fertilizing capacity of thawed bovine semen.

In the spermatozoa of some species, the ubiquitin-proteasome system detects altered proteins and tags them for elimination by the proteasome. In some species' ejaculates, a high proportion of ubiquitinated spermatozoa (i.e. those having ubiquitin bound to the altered or damaged membrane proteins) has been related to infertility. The aim of this study was to assess whether the percentage of ubiquitinated spermatozoa relates to fertility of dairy bulls and whether ubiquitination increases during protein remodelling that occurs during in vitro spermatic capacitation. Thirty-two frozen semen straws from four high-fertility (ReproMax(®) ) and four normal-fertility (Normal) Holstein-Friesian sires were evaluated. Ubiquitinated and capacitated spermatozoa were quantified by sperm ubiquitin tag immunoassay and chlortetracycline stain, respectively. Fertilizing capacity of sires was assessed by in vitro fertilization. No differences were found between Normal and ReproMax(®) sires with regard to the observed percentage of ubiquitinated spermatozoa (42.97 ± 3.69% and 49.68 ± 9.27%, respectively; p > 0.05). Additionally, no differences were found in the percentage of ubiquitinated spermatozoa as a consequence of spermatic capacitation in either Normal (42.97 ± 3.69% before capacitation vs 44.67 ± 7.5% after; p > 0.05) or ReproMax(®) sires (49.68 ± 9.27% before vs 45.05 ± 7.51% after; p > 0.05). The percentage of ubiquitinated spermatozoa in a thawed sperm samples did not correlate with its in vitro fertilizing capacity; thus, this assay does not prove useful to detect in vivo fertility differences between sires. Additionally, protein degradation occurring during remodelling of the spermatozoon plasma membrane during the capacitation process does not seem to involve the ubiquitin-proteasome system.

Breed and breed x environment interaction effects for growth traits and survival rate from birth to weaning in crossbred lambs.

This study was conducted to estimate the effects of sire breed (Charollais, Dorper, Dorset, Hampshire, and Suffolk) and genetic group of the dam [local whiteface (Criolla), grade Hampshire, grade Suffolk, F(1) Dorper × Pelibuey, Australian composite, hair sheep (Barbados Blackbelly or Pelibuey), Dorset, Hampshire and Suffolk] on birth weight, survival rate from birth to weaning, and weaning weight adjusted to 65 d of age. Data were recorded from 2004 to 2006 on crossbreed lambs obtained by artificial insemination from 114 flocks in Central Mexico. High (above the mean) or low (below the mean) environmental categories were assigned to each record from flock-year-season effects solutions obtained in fixed-effects linear model analyses. Birth weights of lambs sired by Charollais rams (3.94 kg) were heavier (P < 0.05) than those sired by Suffolk (3.69 kg) whereas Dorper-, Dorset-, and Hampshire-sired lambs were intermediate. For weaning weight, lambs sired by Charollais were the heaviest (19.16 kg) compared with lambs sired by Hampshire (17.86 kg), Suffolk (17.79 kg), and Dorper (17.28 kg) whereas Dorset sired were the lightest (16.77 kg; P < 0.05). Lambs sired by Dorset rams had a lower survival rate (77.1%) than lambs sired by Charollais, Dorper, Hampshire, or Suffolk (81.6 to 83.3%; P < 0.05). Lambs from Australian composite, Dorset, Hampshire, and Suffolk dams were heavier for birth and weaning compared with lambs from local whiteface (Criolla), hair sheep breeds (Barbados Blackbelly or Pelibuey), or crosses (F(1) Pelibuey × Dorper) dams (P < 0.05) whereas lambs from grade Hampshire and grade Suffolk were intermediate. The genetic group of the dam had no effect (P > 0.05) on survival rate. Sire breed × environmental category interaction effect was significant for birth weight (P < 0.01) and weaning weight (P < 0.05), but relatively small changes on the ranking of sire breeds were observed between environmental categories for weaning weight. Genetic group of the dam × environmental category interaction effect was significant for birth and weaning weights (P < 0.01). Weaning weight of lambs from hair sheep breeds (Barbados Blackbelly or Pelibuey) and crosses (F(1) Pelibuey × Dorper) as well as purebred Dorset, Hampshire, and Suffolk dams were more affected when changing from the high to the low environmental category compared with the other genetic groups. No breed of the sire or genetic group of the dam × environmental category interactions were (P > 0.05) observed for survival rate.

Identification of antigenic variants of the porcine rubulavirus in sera of field swine and their seroprevalence.

We sampled sera from 1013 non-vaccinated swine from four states in Mexico, Guanajuato, Jalisco, Michoacán and the Estado de Mexico, to analyse anti-porcine rubulavirus antibody titres against three different porcine rubulavirus isolates (PAC-4/1993, PAC-6/2001, and PAC-9/2003) using a hemagglutination inhibition assay. The results revealed that there were antigenic differences among the isolates assessed. In particular, the estimated correlation between the PAC-4/1993 and PAC-6/2001 (0.50) isolates and between the PAC-4/1993 and PAC-9/2003 isolates (0.56) displayed a moderate positive correlation. In contrast, there was a strong positive correlation between the PAC-6/2001 and PAC-9/2003 isolates (0.73). We also found that in the state of Guanajuato, PAC-4/1993 was the isolate that was most frequently identified; in Jalisco, the isolate was PAC-6/2001; and in Michoacán, the isolate was PAC-9/2003. By contrast, in the Estado de Mexico, all three isolates appeared to circulate with a low seroprevalence. In general, the analysed sera from the four states displayed a porcine rubulavirus serological prevalence ranging from 9% to 23.7%. These data indicate that there is not complete antibody cross-antigenicity among the three isolates, and the antigenic variations in the antibody response found in this study implies that the use of a monovalent vaccine would not generate complete protection against the different antigenic subtypes.

Vascular endothelial growth factor isoforms 120, 164 and 205 are reduced with atresia in ovarian follicles of sheep.

Vascular endothelial growth factor (VEGF) is a potent stimulator of endothelial cell proliferation and neo-vasculogenesis. In the ovary, VEGF mRNA is localised in the follicle, and it is associated with follicular growth and dominance. Alternative splicing of VEGF mRNA produces eight mature forms of mRNA for equal number of VEGF isoforms. In the present study, the VEGF isoforms in granulosa and theca cells of large (4-6mm) and preovulatory (>6mm) sheep follicles were studied during the process of atresia. Follicles were classified as healthy, early atretic and atretic, and the granulosa and theca cells were isolated. The mRNA for three of these isoforms was found in both theca and granulosa cells, and was quantified by image analysis after RT-PCR using primers that amplified VEGF120, VEGF164, VEGF188 and VEGF205 isoforms. The mRNA for these three isoforms was found in both theca and granulosa cells of healthy and atretic follicles. Atresia was accompanied with a reduction in mRNA for VEGF164 and VEGF120 in granulosa and theca cells (P<0.05). Amounts of both isoforms were reduced with the extent of atresia in the granulosa cells, whilst in the theca cells this reduction was only evident in advanced atretic follicles. Furthermore, after the onset of atresia, VEGF205 was not detectable in the granulosa cells. Follicle size did not affect the amount of VEGF mRNA. Hence, the onset of atresia in follicles of sheep is coupled with a reduction in VEGF mRNA. The decrease in VEGF observed with atresia in follicles of sheep was greater in granulosa than in theca cells.

Genetic and environmental parameters for milk production, udder health, and fertility traits in Mexican Holstein cows.

Genetic and phenotypic parameters for Mexican Holstein cows were estimated for first- to third-parity cows with records from 1998 to 2003 (n=2,971-15,927) for 305-d mature equivalent milk production (MEM), fat production (MEF), and protein production (MEP), somatic cell score (SCS), subsequent calving interval (CAI), and age at first calving (AFC). Genetic parameters were obtained by average information matrix-REML methodology using 6-trait (first-parity data) and 5-trait (second- and third-parity data) animal models. Heritability estimates for production traits were between 0.17+/-0.02 and 0.23+/-0.02 for first- and second-parity cows and between 0.12+/-0.03 and 0.13+/-0.03 for third-parity cows. Heritability estimates for SCS were similar for all parities (0.10+/-0.02 to 0.11+/-0.03). For CAI, estimates of heritability were 0.01+/-0.05 for third-parity cows and 0.02+/-0.02 for second-parity cows. The heritability for AFC was moderate (0.28+/-0.03). No unfavorable estimates of correlations were found among MEM, MEF, MEP, CAI, and SCS. Estimates of environmental and phenotypic correlations were large and positive among production traits; favorable between SCS and CAI; slightly favorable between MEM, MEF, and MEP and SCS, between AFC and SCS, and between SCS and CAI; and small but unfavorable between production traits and CAI. Estimates of genetic variation and heritability indicate that selection would result in genetic improvement of production traits, AFC, and SCS. Estimates of both heritability and genetic variation for CAI were small, which indicates that genetic improvement would be difficult.

Selection response for milk production in conventional production systems in Mexico, using genetic evaluations of Holstein sires from Canada and the United States.

Polynomial regression models of the first, second, and third order were used to fit milk production deviations of daughters in Mexico on Canadian and US predicted transmitting ability values for 305-d mature-equivalent milk production (kg). For the pairs Canada-Mexico and Mexico-United States, 40 and 73 bulls with a minimum reliability of 0.75 were analyzed, respectively. Genetic correlations between pairs of countries were also estimated. The parameters were evaluated for all data, and for sires grouped according to the mean of the average phenotypic milk production (high and low) of their daughters' herd mates. Quadratic and cubic effects were not significant in any analysis. From linear regression models, slopes of Mexican daughter deviations on US and Canadian predicted transmitting abilities were 1.01 and 0.93, respectively. Slopes were greater but intercepts were smaller for the high versus low level of production of the sires' herd mates in Mexico. A greater difference between the genetic correlations was found for the high versus low environmental level than for the low level (0.79 vs. 0.70) for Mexico-US data compared with Canada-Mexico data (0.81 vs. 0.78). Genetic correlations between Mexico and the United States (0.74), and between Mexico and Canada (0.77), were smaller than the genetic correlation between the same Canadian and US sires (0.92), suggesting the presence of a moderate degree of genotype-environment interaction for milk production between Canada and the United States, and Mexico.

Short communication: Changes in the association between milk yield and age at first calving in holstein cows with herd environment level for milk yield.

The aim of this study was to evaluate the effect of herd environment class on the genetic and phenotypic relationships of mature equivalent milk yield (MY) on age at first calving (AFC). Data analyzed were 248,230 first parity records of Holstein cows, daughters of 588 sires in 3,042 herds in the United States. Heritability for AFC was 0.33 +/- 0.01 and 0.20 +/- 0.01 in high and low environment herds, respectively, and 0.47 +/- 0.01 in the complete data set. The correlation between AFC sires' predicted breeding values of low and high classes was 0.69. Genetic correlations between MY and AFC were -0.52 +/- 0.02 and -0.31 +/- 0.03 in high and low environment herds, respectively, and -0.44 +/- 0.02 in the complete data set representing intermediate environments. If selection is based on the whole data set, expected correlated responses for AFC estimated as a result of 1,000 kg of genetic gain in MY, for high and low herd environment herds were -26.1 and -15.3 d, respectively, and -32.6 for the complete data set; hence the highest reduction in AFC occurs in intermediate environment herds. Different estimates of the heritability of AFC, the correlation between AFC breeding values of low and high classes as well as changes in the genetic correlation between MY and AFC across environments indicate genotype x environment interaction. Caution in interpretation is warranted because genetic relationships are dynamic, especially in populations undergoing selection. Current relationships may differ from those during the time period of the present study (1987-1994). Notwithstanding this possibility, methods and findings from the present study provide insight about the complexity of genetic association and genotype x environment interactions between AFC and MY.

Porcine circovirus type 2 antibody detection in backyard pigs from Mexico City.

PCV2 antibodies have been found in pigs from all continents. However, this finding has been mainly studied in domestic swine reared under intensive production conditions. Mexico City, with a human population over 19 million in 2005, has both urban and rural areas. The pig production in its rural area is based on small family backyard farms. Taking into account this rather unique form of rearing pigs, the objective of this study was to determine the seroprevalence in backyard pigs from the rural area of Mexico City. A total of 695 backyard pig serum samples from 108 small family farms belonging to seven municipal areas were studied by immunoperoxidase monolayer assay technique. One hundred six out of the 108 family farms (98.14%) had at least one positive serum sample. On the other hand, 136 (19.57%), 264 (37.99%) and 248 (34.82%) pigs had low, intermediate and high titres to PCV2, respectively. Only 53 samples (7.63%) were negative for PCV2 antibodies. No apparent differences in antibody titre groups were observed among backyard pigs from the different municipal areas. In conclusion, the present study, the first one performed in this kind of extensively produced pigs, indicates that PCV2 is ubiquitous in backyard pigs from Mexico City.

Fertility responses of Mexican Holstein cows to US sire selection.

Genetic relationships between 2 fertility traits and milk production were investigated using mature-equivalent lactation records of 55,162 daughters of 1,339 Holstein sires in Mexico and 499,401 daughters of 663 Holstein sires in the northeastern United States. Data sets contained yields in first and second lactation, age at first calving (AFC), and calving interval (CI). There were 474 US sires in common between countries. A herd-year standard deviation criterion defined nonoverlapping low- (< or = 1,300 kg) and high- (> or = 1,600 kg) opportunity Mexican herd environments and a low-opportunity (< or = 1,024 kg) US environment. Genetic variances for the average Mexican herd (all data) for AFC and CI were 65 and 85% as large as those obtained from half-sisters in the average US herd. Genetic correlations for first-lactation milk in the average US herd and AFC and CI in the average Mexican environment were unfavorable (0.18 and 0.10). Regression coefficients of AFC in Mexican environments on US genetic gain in milk ranged from 2 to 7 d/1,000 kg. However, the favorable predicted response in AFC from genetic gain in milk in Mexican environments, like those in average US herds, ranged from -4 to -7 d/1,000 kg (r(g) = - 0.20). This unequal AFC response may indicate genotype by environment interaction in fitness performance or differential breeding management of high and low yielding Mexican cows. The potential effects of age at first service of breeding females need to be disentangled to accurately assess genetic improvement needs for Mexican Holstein herds.

Genetic effects on sperm design in the zebra finch.

Sperm design and function are important determinants of male reproductive success and are expected to be under strong selection. The way that spermatozoa phenotypes evolve is poorly understood, because there have been few studies of the quantitative genetics of sperm. Here we show, in the zebra finch Taeniopygia guttata, an extraordinary degree of inter-male variation in sperm design that is independent of sperm swimming velocity. A quantitative genetics study using data from over 900 zebra finches in a complex breeding experiment showed that sperm head, mid-piece and flagellum length are heritable, that negative genetic correlations exist between sperm traits, and that significant indirect (maternal) genetic effects exist. Selection on the zebra finch sperm phenotype may be low because sperm competition is infrequent in this species, and this, in combination with negative genetic correlations and maternal genetic effects, may account for the variation in sperm phenotype between males. These results have important implications for the evolution of sperm in other taxa.

Heritability of plasma von Willebrand factor antigen concentration in German Wirehaired pointers.

We applied quantitative genetic analyses to a population of German Wirehaired pointer dogs affected with type 2 von Willebrand disease. Plasma von Willebrand factor (vWF) protein concentration measured as vWF antigen (vWF:Ag), clinical history, and pedigree data were compiled for 331 dogs over a 5-year test period. Eight dogs had histories of abnormal bleeding and had markedly decreased plasma vWF:Ag concentrations (<1%). Four per cent of the dogs were inbred, with an average inbreeding of 2.52%. The estimated heritability of plasma vWF concentration was 0.52. We found a major gene effect on vWF concentration. Using a single gene locus model and two different prediction methods, the upper threshold value for the aa genotype was less than 1% vWF:Ag, and the optimal threshold value for discrimination between the AA and Aa genotypes was between 68% and 72% vWF:Ag. Our analyses indicate that phenotype, assigned on the basis of a single vWF:Ag determination, is heritable and can be applied for selective breeding in a von Willebrand disease test programme.

Effect of herd environment on the genetic and phenotypic relationships among milk yield, conception rate, and somatic cell score in Holstein cattle.

A total of 248,230 primiparous records of Holstein cows calving from 1987 to 1994 (daughters of 588 sires in 3042 herds) was used to evaluate potential genotype by environment interactions among mature equivalent milk yield, lactation mean somatic cell score, and conception rate at first service. Herds were classified into low and high environmental groups using three different criteria: standard deviation of herd mature equivalent milk yield, a combination of herd mature equivalent milk yield mean and standard deviation, and the herd mean of body weight at first calving divided by age at first calving. Genetic parameters were modeled by using multiple-trait linear mixed models and were fitted using the multiple-trait derivative-free software. Heritabilities for mature equivalent milk yield, lactation mean somatic cell score, and conception rate at first service were 0.221, 0.106, and 0.015 in low environment herds and 0.300, 0.093, and 0.009 in high environment herds, respectively. Genetic (and phenotypic) correlations between mature equivalent milk yield and lactation mean somatic cell score, mature equivalent milk yield and conception rate at first service, and lactation mean somatic cell score and conception rate at first service were 0.277, -0.417, and -0.209, (-0.049, -0.180, and -0.040) and 0.173, -0.318, and -0.144, (-0.087, -0.166, and -0.035) in low and high environment herds, respectively. The genetic correlations between pairs of traits were consistently smaller in high environment herds, suggesting that differences in management between the two environment levels lessened the antagonistic genetic association between the traits studied. A long-range plan for low environment herds should focus on improving the level of management, which would greatly reduce the unfavorable correlated changes in lactation mean somatic cell score and conception rate at first service associated with the genetic improvement of mature equivalent milk yield.

Variation in the volume of zebra finch song control nuclei is heritable: developmental and evolutionary implications.

In many songbird species, females prefer males that sing a larger repertoire of syllables. Males with more elaborate songs have a larger high vocal centre (HVC) nucleus, the highest structure in the song production pathway. HVC size is thus a potential target of sexual selection. Here we provide evidence that the size of the HVC and other song production nuclei are heritable across individual males within a species. In contrast, we find that heritabilities of other nuclei in a song-learning pathway are lower, suggesting that variation in the sizes of these structures is more closely tied to developmental and environmental differences between individuals. We find that evolvability, a statistical measure that predicts response to selection, is higher for the HVC and its target for song production, the robustus archistriatalis (RA), than for all other brain volumes measured. This suggests that selection based on the functions of these two structures would result in rapid major shifts in their anatomy. We also show that the size of each song control nucleus is significantly correlated with the song related nuclei to which it is monosynaptically connected. Finally, we find that the volume of the telencephalon is larger in males than in females. These findings begin to join theoretical analyses of the role of female choice in the evolution of bird song to neurobiological mechanisms by which the evolutionary changes in behaviour are expressed.

Interaction between milk yield of Holstein cows in Mexico and the United States.

Genotype by environment interaction for milk yield was investigated by analyzing 55,162 mature equivalent, first lactation records of daughters from 1339 Holstein sires in Mexico and 499,401 daughters from 663 Holstein sires in the northeastern US. There were 474 US sires in common. Herd-year standard deviation was used to define non-overlapping high (> or = 1600 kg) and low (< or = 1300 kg) Mexican environments and a low (< or = 1025 kg) US environment. Variance components across Mexican environments were about 40% less than those of the US environment. Genetic correlation coefficients between milk yield in various Mexican environments and all US environments ranged from 0.60 to 0.71 and were different from unity (P < 0.001). Genetic correlation coefficients with low environment in the US ranged between 0.69 and 0.93; the largest correlation was between the low US and high Mexico environments. Both reductions in the size of genetic variance in Mexican environments relative to the US and genetic correlation coefficients less than unity were indicative of genotype by environment interaction. A significant rank change in estimated breeding values (EBV) of sires in Mexican environments relative to the US was another indicator of genotype of EBV of a sire estimated from daughters performances in low and high environments in Mexico were 0.46 and 0.62 against EBV of sires estimated from all data in the US. Against EBV estimated from the low environment in the US they were 0.57 and 0.83. The US low environment was a better predictor of performance in Mexican environments.