Anatomical characterization of hoof growth pattern in six Iranian sheep breeds and its possible implication for trimming recommendations.

The objective of this study was to compare hoof anatomy, hoof growth pattern, and hoof weight-bearing surface of six different Iranian sheep breeds to identify possible differences in the hoof anatomical features that could help to minimize adverse effects of hoof trimming methods. Front and hind hooves of 2-year-old, previously untrimmed, pastured dairy ewes of six Iranian breeds (Afshari, Moghani, Kurdi, Makoui, Chaleshtori, and Lori-Bakhtiari; n = 180 ewes; 30 ewes per breed) were collected after slaughter. Medial and lateral claws were incised sagittally and anatomical measurements such as toe length, heel height, toe height, sole thickness, sole length, and toe angle were recorded in each claw. Data were analyzed using mixed model equations including breed, claw (lateral or medial), hoof (front or hind) and their interactions as fixed effects, and ewe as random effect. Breed differences were observed for all hoof measurements (P < 0.05). Chaleshtori sheep had higher measurements for most of the traits studied while Afshari and Makoui sheep had lower measurements. All measurements, except for toe length and toe height to solar surface to heel height ratio, were significantly greater in the front hooves than in the hind hooves (P < 0.05). Soles were longer in the medial claws compared to the lateral claws of the front hooves (P < 0.05). Results suggest the observed breed differences could interfere with establishing a standard, uniform hoof trimming method for sheep. For instance, it might be possible that while Afshari and Makoui sheep could require more conservative trimming, Chaleshtori sheep could require to be trimmed more. In consequence, hoof trimming methods might need to be adjusted to specific breed characteristics to avoid possible tissue damage.

Seroprevalence and risk factors associated with bovine herpesvirus 1 and bovine viral diarrhea virus in North-Eastern Mexico.

Bovine herpesvirus 1 (BoHV-1) and bovine viral diarrhea virus (BVDV) are well known etiological agents of cattle that produce important economic losses due to reproductive failures and calf mortality, as well as enteric and respiratory disease. Tamaulipas is located northeast of Mexico, an important cattle production and the principal exporter of calf and heifer to the United States. The objectives of this study were to estimate the seroprevalence of BoHV-1 and of BVDV, and to determine the effects of risk factors on these infections. Blood samples of cattle from 57 farms from rural districts of Tamaulipas were collected. The samples were tested for antibodies against BoHV-1 and BVDV using commercial ELISA kits. Data on potential risk factors were obtained using a questionnaire administered to the farmer at the time the blood samples were taken. The seroprevalences for BoHV-1 and BVDV were 64.4% and 47.8%, respectively. In the logistic regression analysis, the significant risk factors were rural district, herd size and cattle introduced to the farm. This study confirms the high seroprevalence of BoHV-1 and BVDV in unvaccinated cattle in Tamaulipas, Mexico. The results of this study could be used for the development of BoHV-1 and BVDV prevention and control program in North-Eastern, Mexico.

Prevalence and risk factors of Toxoplasma gondii in fattening pigs farm from Yucatan, Mexico.

The objective of this study was to estimate the prevalence and identify risk factors associated with the presence of Toxoplasma gondii in pig-fattening farms from Yucatan, Mexico. A cross-sectional study was conducted with a two-stage sampling. There were 429 pigs sampled from 39 farms randomly selected. Blood samples were collected to obtain DNA and serum. The presence of IgM and IgG antibodies was determined by indirect ELISA. Prevalence was estimated by diagnostic test. Potential risk factors to be included in a marginal logistic regression were tested by chi-square or Fisher. The prevalence of IgM and IgG was 92.5% (397/429) (CI 89.9-95.1%) and 95.8% (411/429) (CI 93.7-97.8%), respectively. Regarding PCR, a prevalence of 50.8% (218/429) (CI 45.9-55.6%) was found. The logistic regression showed an association with herd size and type of feeder (P < 0.05). The risk of a case in farms with ≤400 pigs was 27.9 times higher than in farms with >400 pigs. The manual feeder was a significant protective factor associated with the seropositive against T. gondii. Results indicate a high circulation of T. gondii in pig-fattening farms from Yucatan, finding an increased risk of infection for those farms with less than 400 animals and automatic feeders.

Intraherd correlation coefficients and design effects for bovine viral diarrhoea, infectious bovine rhinotracheitis, leptospirosis and neosporosis in cow-calf system herds in North-eastern Mexico.

Knowledge of the intraherd correlation coefficient (ICC) and design (D) effect for infectious diseases could be of interest in sample size calculation and to provide the correct standard errors of prevalence estimates in cluster or two-stage samplings surveys. Information on 813 animals from 48 non-vaccinated cow-calf herds from North-eastern Mexico was used. The ICC for the bovine viral diarrhoea (BVD), infectious bovine rhinotracheitis (IBR), leptospirosis and neosporosis diseases were calculated using a Bayesian approach adjusting for the sensitivity and specificity of the diagnostic tests. The ICC and D values for BVD, IBR, leptospirosis and neosporosis were 0.31 and 5.91, 0.18 and 3.88, 0.22 and 4.53, and 0.11 and 2.68, respectively. The ICC and D values were different from 0 and D greater than 1, therefore large sample sizes are required to obtain the same precision in prevalence estimates than for a random simple sampling design. The report of ICC and D values is of great help in planning and designing two-stage sampling studies.

Seroprevalence of and risk factors for brucellosis of goats in herds of Michoacan, Mexico.

Our objectives were to estimate the seroprevalence of Brucella melitensis, and to identify some risk factors associated with goat seropositivity in Michoacan, Mexico. Blood samples were collected from 5114 animals from 79 herds. Sera were tested for antibodies against B. melitensis using the Rose Bengal plate test and the complement-fixation test. Information regarding the herds and each animal sampled were recorded through a personal interview at the farm. We used random-effects multivariable logistic regression to analyze our data. Fifty-six herds of the 79 tested had at least one seropositive animal. The animal-level true seroprevalence was 9.8% (CI=8.8, 10.7). Animals in large herds (>34 animals), in herds with high stock density (>3.5 animals/m(2)) or animals >24 months old had higher odds of seropositivity (2.0, 1.7 and 1.8, respectively) than those in small herds, in herds with low stock density or animals < or =24 months old.

Detection of antibodies and risk factors for infection with bovine respiratory syncytial virus and parainfluenza virus-3 in beef cattle of Yucatan, Mexico.

We collected blood samples from 756 > or =2-year-old cattle in 54 herds in Yucatan, Mexico, and used all of those to determine the antibody seroprevalences (in an indirect enzyme-linked inmunosorbance assay) to bovine respiratory syncytial virus (BRSV) and risk factors for animal-level seropositivity. We used 728 of the same samples (from 52 of the same herds) to do the same for parainfluenza virus-3 (PIV3). Cattle were selected by two-stage cluster sampling. Herd-level and animal-level risk factors were obtained through a personal interview. We analyzed the data by using a random-effects multivariable logistic regression model for clustered observations. All herds had at least 3 (BRSV) or 5 (PIV3) seropositive animals. The animal-level true seroprevalences were: 90.8% (86.5, 95.2%) and 85.6% (80.9, 90.4%) for BRSV and PIV3, respectively. Animals in large herds and old animals had the highest odds of being seropositives to BRSV, and those risk factors plus animals born on the farm for PIV3 infection.

Reproductive patterns and reproductive pathologies of stray bitches in the tropics.

The objectives of this study were to determine the annual reproductive pattern and to estimate the frequency of reproductive pathologies in female mongrel stray dogs under tropical conditions. The genital tracts of 300 mongrel bitches from a municipal dog pound were examined post-mortem from January to December 2003. Season of the year, age, size, and body condition score (BCS) were recorded for each dog. The year was divided into three seasons: warm-dry (March-June), warm-humid (July-October), and fresh-humid (November-February). Distribution of estrus periods was not influenced by any of the factors studied (i.e. season, age, size, BCS). A significantly lower number of pregnancies were recorded during the warm-dry season, probably as a consequence of embryo resorption. Underweight animals had a significantly lower percentage of pregnancies than bitches of ideal BCS. More ovulations per bitch occurred during the warm-humid season than during the other seasons of the year, probably due to climatic factors. Bitches of medium and large size had more ovulations than those of small size. Of the 300 bitches examined, 43.5% had one or more genital pathologies. The most frequent pathologies found in the ovary, uterus, and vagina were epoöphoron cysts (6.7%), serosal inclusion cysts (5.0%), and transmissible venereal tumors (15.3%), but the capacity of the females to come into estrus or to become pregnant was not affected by these conditions. We concluded that stray domestic bitches in the tropics were not seasonal breeders, but their reproductive pattern was apparently modified by environmental factors such as temperature and probably photoperiod. Although several bitches in the present study had reproductive pathology, the most prevalent pathologies did not adversely reproductive capacity.

Pathological conditions of the reproductive organs of male stray dogs in the tropics: prevalence, risk factors, morphological findings and testosterone concentrations.

The objective of this study was to estimate the prevalence of and risk factors for pathological conditions of the reproductive organs in stray dogs under tropical conditions. Three hundred and eighteen dogs were examined post-mortem in the period from 1 July 2002 to 30 June 2003. Before killing, a blood sample (from the cephalic vein) for testosterone assay was taken. Pathological conditions of the reproductive organs were found in 135 of the dogs (42.5%) and in 175 of the testes (64.8%). The most frequent pathologies found were testicular degeneration, cryptorchidism, testicular hypoplasia and testicular tumours (in 15.1%, 6.6%, 6.6% and 5.4% of the dogs and 15.1, 4.6, 6.0 and 3.5 of the testes, respectively). Transmissible venereal tumour (TVT) was seen in 5.4% of the dogs. Testicular degeneration was more common in old dogs and underweight dogs (p < 0.05). Testicular tumours were 14.3 times more common in cryptorchid dogs. Age was another important factor for the development of testicular tumours (p < 0.05). Lower levels of testosterone concentration (p < 0.05) were observed in dogs with advanced testicular degeneration (0.7 +/- 0.8 nM), dogs with hypoplastic testicles (0.8 +/- 0.9 nM) and dogs with one degenerated and one retained testis or with bilateral cryptorchidism (1.2 +/- 0.9 nM) compared to dogs with one or two normal testes (7.0 +/- 5.5 nM). Testicular volume and weight were significantly lower in degenerated, hypoplastic and retained testes compared with the contralateral normal testis. Some spermatogenic activity was found in three of the retained testes, producing oligozoospermic smears with a high percentage of sperm abnormalities. No comparable epidemiological data about male pathological conditions of the reproductive organs in the dog is available. The prevalence found in this study, yet, appears high.

Reproductive patterns of stray male dogs in the tropics.

Two studies were performed to determine annual reproductive patterns in stray male dogs in the tropics. In Study 1, four dogs housed individually outdoors were monitored once monthly for 12 months, including collection and assessment of semen, measurements of scrotal width, and determination of serum testosterone and prolactin concentrations. In Study 2 (conducted concurrently), a single blood sample (for serum testosterone concentration) was collected from 220 clinically healthy dogs, and after euthanasia, scrotal width and morphology of epididymal sperm were determined. The year was divided into three seasons: warm-dry (March to June); warm-humid (July to October) and fresh-humid (November to February). In Study 1, scrotal width, ejaculate volume, sperm count and motility were significantly lower during the fresh-humid season and sperm midpiece abnormalities were significantly more common during the warm-humid and fresh-humid seasons. Serum testosterone concentrations remained constant during the year. Prolactin concentrations did not differ significantly among seasons, but had a well-defined increase from the beginning of March to the end of August. In Study 2, sperm morphology was similar to in Study 1 and serum testosterone concentrations varied nonsignificantly during the year. Environmental factors, e.g. daylength may have influenced circannual changes in prolactin secretion. Seasonal variations in some reproductive tract and seminal traits were significant but of small magnitude and the percentage of morphologically normal sperm did not vary significantly among seasons. In conclusion, healthy male dogs constantly produced sperm and were apparently fertile throughout the year.

Prevalence of fetal resorption in stray dogs in Yucatan, Mexico.

OBJECTIVES: To determine the prevalence of fetal resorption in 77 pregnant bitches and its association with the age, size and body condition score of the bitch and to determine the frequency of transuterine migration of embryos. METHODS: The number and position of embryos or fetuses and placental zones were registered postmortem. The prevalence of fetal losses was determined by comparing the number of corpora lutea with the number of embryos or fetuses in each bitch. The prevalence of transuterine migration of embryos was determined by correlating the number of fetuses in each horn and the number of corpora lutea in the ipsilateral ovary. RESULTS: Fetal resorption zones were demonstrated in 42.9 per cent of the bitches. However, pregnancy continued in 84.9 per cent of cases. Of the fetal losses, 25.9 per cent were determined by counting the number of corpora lutea and viable embryos or fetuses. Young bitches tended to have a higher probability of fetal resorption than adult bitches (P<0.06). The presence of fetal resorption zones was not associated with size or body condition. Transuterine migration of embryos had occurred in 15.8 per cent of the bitches. CLINICAL SIGNIFICANCE: This study demonstrated that embryo resorption is a normal event in the bitches, with a higher prevalence than previously thought.

Body weights at weaning and 18 months of Zebu, Brown Swiss, Charolais and crossbred heifers in south-east Mexico.

The objective of this study was to evaluate the body weights up to 18 months of age of 12 breed groups of Zebu (Z), Brown Swiss (BS) and Charolais heifers (CH), and their crosses under tropical conditions. A total of 1434 data on weaning weights adjusted to 240 days (WW8), average daily gain to 240 days (ADG8) and 1025 body weights adjusted to 550 days (BW18) and average postweaning daily gain (ADG18) of heifers born from 1981 to 1995 were used. Cows and calves remained together from birth to weaning and grazed on Guinea grass (Panicum maximum). Years of birth were grouped in three periods, because of the small numbers of observations per year (1981-85, 1986-90 and 1991-95). Similarly, months of birth were grouped in three seasons: dry (February to May), rainy (June to September) and windy and rainy (October to January). Ages of dams were classified in six groups (or=8 years). Breed groups were animals with 12.5%, 25.0%, 50.0%, 62.5%, 75.0% and 100% BS genes and 25.0%, 50.0%, 75.0% and 100% CH genes and also Z and undefined crossbred animals. Data were analysed using a fixed model that included effects of period, and season of birth, age of dam and breed group of heifer. Analyses of variance showed significant (p < 0.05) effects of period, season and breed group for all traits. However, parity was significant (p < 0.05) only for WW8 and ADG8. Interactions among main factors were not significant (p > 0.05). Z heifers gained the least weight to weaning but were similar to BS at 18 months of age. CH were heavier at 18 months of age than BS heifers, but not at weaning. Body weights at 18 months of age of 1/8 and 1/4 BS crossbred heifers were similar (p > 0.05) and lower than F1 (BS x Z) (p < 0.05); however, the later and higher grades of BS had the highest body weights at 18 months of age and were similar to CH and 1/4 CH x 3/4 Z heifers. Undefined crossbred heifers had better performance than the Z breed group. Environmental factors were important sources of variation for pre- and postweaning traits. Under the conditions of this study, crossbred heifers generally performed better than Z heifers up to 18 months of age.

Incidence of salmonellosis and identification of serogroups and serotypes in a pig commercial farm in Yucatan.

A study was conducted in order to detect the presence of Salmonella spp in fattening pigs, to identify the serogroups present and to determine the sensibility to the antibiotics more used in the region. The farm was a breeding farm of a multiple-site system. Of the total farrowings of a week, 55 sows and one piglet from each sow were selected. All pigs were negative to Salmonella spp. at the star of the study. Piglets were monitored from day two of age (six times; every 23 days approximately) up to finishing (23 weeks of age). Samples of feces (1 g/animal) were collected directly from the pig's rectum. The first positive pig was found at the second sampling (25 days) and the highest number of positive cases in the fifth sampling (117 days). The cumulative incidence was 52.7%. Thirty-four out of the 40 Salmonellas isolated corresponded to the B serogroup and 6 to the C2 serogroup. The serotypes found in the B serogroup were: S. typhimurium (28/34) and S. agona (6/34). Regarding serogroup C2 these were: S. romanby and S ajiobo. Salmonella spp B serogroup included three of the serotypes more commonly isolated in humans: S. typhimurium, S. agona and S. heidelberg.

Genetic and non-genetic effects on productive and reproductive traits of cows in dual-purpose herds in southeastern Mexico.

Data on productive and reproductive performance of cows in dual-purpose herds were analyzed to determine the effect of some environmental and genetic factors on saleable milk yield (SMY), lactation length (LL), daily saleable milk per lactation (DMYL), calving interval (CI), and daily saleable milk per calving interval (MYCI) in dual-purpose herds in Yucatan, Mexico. Repeatabilities (re) for these traits were also estimated. Data were obtained from monthly visits to 162 herds from 1996 to 2000. The fixed factors studied were: region (central, eastern and southern), parity number (1 to 6), calving year (1996 to 2000) and calving season (dry, rainy and windy and rainy), genetic group (low- (< 0.50%), medium- (50%) and high- (> 50%) grade cows with European genes). About 2700 to 7700 cows were evaluated for each trait. All factors had significant effects (P < 0.05) on the traits except for region on CI and calving season on DMYL. The overall means for SMY, LL, DMYL, CI, and MYCI were: 1322.3 +/- 80.5 kg, 224.8 +/- 1.3 days, 5.8 +/- 0.1 kg, 555.1 +/- 16.5 days, and 3.0 +/- 0.1 kg, respectively. The re values for SMY, LL, DMYL, CI, and MYCI traits were: 0.19 +/- 0.03, 0.08 +/- 0.04, 0.16 +/- 0.04, 0.00 +/- 0.08, and 0.08 +/- 0.07, respectively. First parity cows had lower SMY, shorter LL, longer CI, and lower MYCI means than cows with more than one parity. Medium grade cows produced more SMY, DMYL and MYCI and had shorter CI than low- and high-grade cows. Therefore, under Yucatan conditions medium-grade cows should be exploited, and more attention should be given to first parity cows in order to improve the productivity in the herd. The relatively high re estimates for SMY and DMYL can be used to calculate most probable producing abilities, in order to identify which cows should be culled.

Bovine viral diarrhoea virus in beef cattle herds of Yucatan, Mexico: seroprevalence and risk factors.

A survey of bovine viral diarrhoea virus (BVDV) infection was carried out from June 2001 to July 2002 in a non-vaccinated beef cattle population from the livestock region of Yucatan, Mexico, to assess seroprevalence and identify risk factors related to seroprevalence. The aim was also to estimate the intra-herd correlation (r(e)) and design effect (D) of BVDV seropositivity. Cattle were selected by a two-stage cluster sampling. Blood samples were collected from 560 animals originating from 40 herds. Sera were tested for antibodies against BVDV using an indirect ELISA test. The sensitivity and specificity of the test was 97.9 and 99.7%, respectively. Risk factors regarding the herd and each animal sampled were recorded through a personal interview at the time of blood sampling. Twenty-four of the 40 herds had at least one seropositive animal. The animal true seroprevalence was estimated as 14%. The marginal logistic regression model used to describe the data found a significant (p<0.05) association of herd size-cow-origin interaction. The interaction was due to a higher risk of seropositivity in the category of herds with 196 animals. The r(e) and D values were 0.17+/-0.05 and 3.16+/-0.57, respectively.

Genetic and non-genetic effects on productive and reproductive traits of cows in dual-purpose herds in southeastern Mexico

Data on productive and reproductive performance of cows in dual-purpose herds were analyzed to determine the effect of some environmental and genetic factors on saleable milk yield (SMY), lactation length (LL), daily saleable milk per lactation (DMYL), calving interval (CI), and daily saleable milk per calving interval (MYCI) in dual-purpose herds in Yucatan, Mexico. Repeatabilities (re) for these traits were also estimated. Data were obtained from monthly visits to 162 herds from 1996 to 2000. The fixed factors studied were: region (central, eastern and southern), parity number (1 to 6), calving year (1996 to 2000) and calving season (dry, rainy and windy and rainy), genetic group (low- (< 0.50%), medium- (50%) and high- (> 50%) grade cows with European genes). About 2700 to 7700 cows were evaluated for each trait. All factors had significant effects (P < 0.05) on the traits except for region on CI and calving season on DMYL. The overall means for SMY, LL, DMYL, CI, and MYCI were: 1322.3 +/- 80.5 kg, 224.8 +/- 1.3 days, 5.8 +/- 0.1 kg, 555.1 +/- 16.5 days, and 3.0 +/- 0.1 kg, respectively. The re values for SMY, LL, DMYL, CI, and MYCI traits were: 0.19 +/- 0.03, 0.08 +/- 0.04, 0.16 +/- 0.04, 0.00 +/- 0.08, and 0.08 +/- 0.07, respectively. First parity cows had lower SMY, shorter LL, longer CI, and lower MYCI means than cows with more than one parity. Medium grade cows produced more SMY, DMYL and MYCI and had shorter CI than low- and high-grade cows. Therefore, under Yucatan conditions medium-grade cows should be exploited, and more attention should be given to first parity cows in order to improve the productivity in the herd. The relatively high re estimates for SMY and DMYL can be used to calculate most probable producing abilities, in order to identify which cows should be culled.

Productive performance of Creole chickens and their crosses raised under semi-intensive management conditions in Yucatan, Mexico.

1. The productive performance of 4 chicken breed groups managed under semi-intensive conditions in Yucatan, Mexico was evaluated. Thirty-six mixed chickens, one week of age of each of the 4 breed groups (Creole, F1 Hubbard x Creole, 7/8 Hubbard x 1/8 Creole and Hubbard) were used. 2. During 1 to 3 weeks of age all birds were fed on a diet containing 210 g/kg crude protein (CP) and 12.95 MJ/kg metabolisable energy (ME). From weeks 4 to 7, they were given a diet with 190 g/kg CP and 12.55 MJ/kg ME. Food consumption and live body weight were recorded weekly. Statistical analysis of the data was performed according to complete randomised design and means comparison using Tukey test was carried out when necessary. 3. Creole chicks had the lightest weights at all ages as compared to their crosses and the Hubbard birds. At 7 weeks of age, Creole chicks were 2.11, 2.44 and 2.90 times lighter than their contemporary F1, 7/8 Hubbard x 1/8 Creole and Hubbard birds, respectively. Hubbard birds were heavier than F1 and 7/8 commercial x 1/8 Creole birds, and the latter group heavier than the F1 birds. Similarly, Creole chicks had the lowest growth rate compared to the other genetic groups. Heterosis for body weight up to 7 weeks of age was 8.2%. 4. Feed consumption was also lower for the Creole chicks at all ages. Food:gain ratio, however, was higher for the Creole chicks at all ages. Food:gain ratios from weeks 2 to 7 were 2.18, 2.65, 3.04 and 4.36 for the Hubbard, 7/8 Hubbard x 1/8 Creole, F1 and Creole birds, respectively. Heterosis for food:gain ratio from 2 to 7 weeks of age was -7.0%. 5. Crossbreeding of Mexican Creole birds with commercial type broilers might improve productive performance.

Seroprevalence of and risk factors for leptospiral antibodies among cattle in the state of Yucatan, Mexico.

Sera obtained from cattle in the state of Yucatan, Mexico, were screened using the microscopic agglutination test against 13 serovars of Leptospira interrogans. A total of 62.8% (461/734) cows were positive for one or more serovars. This seroprevalence probably reflects infection because vaccination against leptospirosis has not been practised in Yucatan. The most common antibodies detected were those against antigens of serovars hardjo (54.1%) and tarassovi (53.3%). Region was the only risk factor associated with the seroprevalence of leptospirosis (p < 0.05).

Seroprevalence of and risk factors for infectious bovine rhinotracheitis in beef cattle herds of Yucatan, Mexico.

The main objective of this cross-sectional study was to estimate the seroprevalence of infectious bovine rhinotracheitis (IBR) in a population of non-vaccinated beef cattle in the livestock region of Yucatan, Mexico and to determine potential risk factors related to the seroprevalence. Also, we estimated the intraherd correlation (r(e)) and design effect (D) of IBR seropositivity. Cattle were selected by two-stage cluster sampling. Blood samples were collected from 564 animals from 35 herds. Sera were tested for antibodies against IBR using the serum-neutralisation test. Information regarding the herd and each animal sampled were recorded through a personal interview with the farmer or farm manager. The data were analysed using fixed-effects logistic multiple regression. Thirty-four of the 35 herds had at least one seropositive animal. The animal true seroprevalence was 54.4%. Animals in large herds or in production had higher odds of seropositivity than those in small herds or growing. The r(e) and D were 0.17 and 3.62, respectively.