Quantification of horizontal transmission of Salmonella enterica serovar Enteritidis bacteria in pair-housed groups of laying hens.

An important source of human salmonellosis is the consumption of table eggs contaminated with Salmonella enterica serovar Enteritidis. Optimization of the various surveillance programs currently implemented to reduce human exposure requires knowledge of the dynamics of S. Enteritidis infection within flocks. The aim of this study was to provide parameter estimates for a transmission model of S. Enteritidis in laying-type chicken flocks. An experiment was carried out with 60 pairs of laying hens. Per pair, one hen was inoculated with S. Enteritidis and the other was contact exposed. After inoculation, cloacal swab samples from all hens were collected over 18 days and tested for the presence of S. Enteritidis. On the basis of this test, it was determined if and when each contact-exposed hen became colonized. A transmission model including a latency period of 1 day and a slowly declining infectivity level was fitted. The mean initial transmission rate was estimated to be 0.47 (95% confidence interval [CI], 0.30 to 0.72) per day. The reproduction number R(0), the average number of hens infected by one colonized hen in a susceptible population, was estimated to be 2.8 (95% CI, 1.9 to 4.2). The generation time, the average time between colonization of a "primary" hen and colonization of contact-exposed hens, was estimated to be 7.0 days (95% CI, 5.0 to 11.6 days). Simulations using these parameters showed that a flock of 20,000 hens would reach a maximum colonization level of 92% within 80 days after colonization of the first hen. These results can be used, for example, to evaluate the effectiveness of control and surveillance programs and to optimize these programs in a cost-benefit analysis.

Nutritional evaluation of high-digestible sorghum for pigs and broiler chicks.

Two experiments were conducted to evaluate the nutritional quality of 2 varieties of Purdue high-digestible sorghum (PHD1 and PHD2) and a normal sorghum, compared with corn, in diets of pigs and broiler chicks. In Exp. 1, 12 pigs (average BW, 55 kg) fitted with ileal T-cannula were fed 4 diets containing 946 g of corn or sorghum (PHD1, PHD2, and normal) per kg in a 2-period crossover design (i.e., each pig received 2 diets over a 2-wk period with 6 pigs per dietary treatment) to determine apparent ileal or total tract digestibility of nutrients and energy. There was no difference in the ileal or total tract digestibility of DM, energy, P, Ca, or N among dietary treatments. In Exp. 2, a total of 192 broiler chicks were grouped by weight into 8 blocks of 4 cages each with 6 chicks per cage, and cages were assigned randomly to 1 of the 4 dietary treatments within each block. Chicks were fed corn-soybean meal (SBM) or sorghum-SBM diets for 21 d to determine apparent total tract retention and then switched to diets containing 935 g of the corresponding corn or 1 of the 3 sorghum varieties per kg for 7 d to determine apparent ileal digestibility and total tract retention. Apparent ileal digestibilities of DM and P, as well as energy, were not different in chicks fed diets containing 935 g of corn or 1 of the 3 sorghum varieties per kg. However, apparent total tract retention of DM, energy, and N in chicks fed corn was greater (P < 0.05) than those fed 1 of the 3 sorghum varieties. Although the apparent ME content of corn was greater than PHD1 and normal sorghum (P < 0.01), it was not different from PHD2 sorghum. There was no difference in apparent total tract retention of DM between chicks fed the corn-SBM and PHD-SBM diets, but it was greater (P < 0.05) in chicks fed the corn-SBM diet than those fed the normal sorghum-SBM diet. Apparent total tract retention of N in chicks fed the PHD1-SBM diet was lower (P < 0.05) than in those fed the corn-SBM diet but greater (P < 0.05) than in chicks fed the normal sorghum-SBM meal diet. No difference in the apparent ME content between the corn-SBM and PHD2-SBM diets was observed, but it was greater (P < 0.05) for the corn-SBM diet than the PHD1- or normal sorghum-SBM diet. Weight gain, feed intake, and feed efficiency were not different in chicks fed the corn-SBM or sorghum-SBM diets. Sorghum could serve as a substitute for corn in cereal grain-SBM diets for pigs and broiler chicks.

Distribution of brucellosis among small ruminants in the pastoral region of Afar, eastern Ethiopia.

A cross-sectional study was conducted in the pastoral region of Afar, in eastern and central Ethiopia, to determine the distribution of brucellosis in small ruminants. Between December 2005 and June 2006, 1,568 serum samples were taken: 563 samples from sheep and 1,005 from goats. One hundred and forty-seven of these (9.4%) tested positive using the Rose Bengal plate test (RBPT), and 76 (4.8%) also tested positive by the complement fixation test (CFT). Brucellosis was detected in all five administrative zones of the region. The difference in prevalence (P) among the zones was not statistically significant (P > 0.05). The seroprevalence of Brucella infection was found to be 5.8% (n = 58) in goats and 3.2% (n = 18) in sheep. A prevalence rate of 5.3% was observed in adult animals and 1.6% in younger sheep and goats. Caprine species (chi2 = 5.56) and adult goats and sheep (chi2 = 4.84) were found to be at higher risk of Brucella infection (P < 0.05). No statistically significant difference was found between males and females (chi2 = 2.57, P > 0.05). The study showed that small-ruminant brucellosis is a widely distributed disease in Afar. The authors recommend the implementation of well-organised disease control and prevention methods to mitigate the economic losses and public health hazard caused by the disease.

The effects of tannins on nutrient utilisation in the White Pekin duck.

1. Two experiments were conducted to determine the effects of tannins on nutrient utilisation in the White Pekin duck. 2. Experiment 1 was a rapid nutrient balance assay to determine the nitrogen (N) retention and metabolisable energy (ME) of maize, low-tannin sorghum (P-954063) (Sorghum bicolor (L). Moench) and high-tannin sorghum (IS-4225) cultivars for ducks. The assay lasted 120 h, with an initial 24 h food-deprivation period, a 48 h excreta collection period for endogenous losses and a 48 h excreta collection period for ingredient losses. The true metabolisable energy (TMEn) content was lower (P<0.05) in the high-tannin sorghum cultivar (13.85 MJ/kg) than the maize (14.94 MJ/kg) and the low-tannin sorghum cultivar (14.39 MJ/kg). True N retention was lower (P<0.05) for the high-tannin sorghum (0.24 g) than for maize (1.33 g) and low-tannin sorghum (1.1 g). 3. In experiment 2, the brush-border membrane vesicles technique was used to determine whether tannic acid caused inhibition of L-threonine transport across duck intestinal brush-border membrane. The brush-border membrane vesicles were mixed with tannic acid solutions (pH 7.4) to give gradient tannic acid concentrations of 0, 0.05, 0.10, 0.25, 0.50, 1.00 and 2.50%. As a fraction of the control (no tannic acid), the maximal inhibition of L-threonine transport (Imax) under the sodium-gradient condition was 77.10% (P<0.05). Under the sodium-free condition, the maximal inhibition of L-threonine transport (Imax) was 45.15% (P<0.05). 4. These results demonstrated that nutrient utilisation in the White Pekin duck was lower from the high-tannin sorghum cultivar than from the low-tannin sorghum cultivar. The results also suggested that the antinutritive effects of tannins in foodstuffs are due partly to their inhibitory action on intestinal brush-border bound amino acid transporter proteins.

Screening for grain polyphenol variants from high-tannin sorghum somaclones.

Several hundred somaclones established from plants regenerated from embryogenic callus cultures of six high tannin sorghum lines were screened for variants with altered levels of polyphenols in the grain. Grain from over 6000 plants including the R 1 (primary), R2, and R3 generations were analyzed for total phenols, flavan-4-ols, and proanthocyanidins (condensed tannins). Although many variants which had lost the ability to synthesize chlorophyll were found, none of the somaclones tested had lost or greatly reduced the ability to synthesize any of the polyphenols assayed. However, we did observe statistically significant differences in polyphenol concentration between tissue culture-derived R1 plants and the parental controls. In the R2 generation the proportion of somaclones which differed significantly from the parents varied from 47% to 68% depending upon genotype. The average somaclonal variation rate and somaclonal variant frequency estimated in the tested population for the three polyphenol characteristics ranged from 37.3% to 40.7% and 5.3% to 7.8%, respectively. Variants with decreased levels of polyphenols were usually epigenetic and reverted back to normal levels in subsequent generations, but those with increased levels usually persisted after two meiotic cycles, indicating they are heritable. Variants with polyphenol levels increased up to 80% or decreased by 30% were selected for in the R3 generation.

Development and maturation of surghum seeds on detached panicles grown in vitro.

A procedure for culturing detached panicles of sorghum, Sorghum bicolor (L.) Moench, was developed to achieve flowering, fertilization, and subsequent seed development and maturation in vitro. Sixteen sorghum genotypes (five high and eleven low in tannin) were tested for their ability to develop normally in culture. Panicles collected one to two days before the initiation of anthesis were cultured in flasks containing liquid medium. Contamination and medium darkening were the major obstacles encountered. Up to 55% of the panicles cultured reached physiological maturity in vitro. The frequency of seed set ranged from 30 to 97% depending upon genotype and medium. Seed and glume color were normal. Seed produced in vitro resembled those grown in vivo and germinated well, but were smaller than normal (100 kernel weight reached 50 to 70% of the control). Grain polyphenols were synthesized in the cultured panicles. Seed of high tannin genotypes produced in vitro were lower in total phenols and tannins and higher in flavan-4-ols and the 3-deoxyanthocyanidin pigments than control seed. This technique can be used for harvesting late-maturing stocks and for various sorghum studies.

Somaclonal variation in high tannin sorghums.

Genetic variants were found among over 6,000 primary plants (R1) regenerated from embryogenic tissue cultures of eight high tannin sorghums [Sorghum bicolor (L.) Moench]. Field assessment of somaclonal variation has progressed to the R2 population, with over 48,000 R2 seedlings (27,000 plants) in 1,126 rows from 1,055 R1 plants. A total of 43 variant phenotypes was recovered, including several types of chlorophyll deficiencies, dwarfism, short culm, sterility, narrow leaf, and several previously unreported variants, such as ragged leaf, multibranched heads, and Hydra, a developmental variant which produces large numbers of panicles. Variation production greatly depends on parent genotype and appears to increase with increasing time in cultures. The toal average somaclonal variation rate (based per 100 R1 plants) and somaclonal variant frequency (based per 100 R2 plants) estimated in the tested population were 11.3 and 1.6, respectively. Chimerism was found in regenerants. The estimated size of the mutated sector carried by mutant regenerants ranged from the whole plant to less than 3% of a single head. The average proportion of mutated R1 heads carrying large (80%-100%), medium (40%-80%), and small (<40%) mutated sectors was 38.7%, 26.0% and 35.3%, respectively. Some sector mutations do not appear until the R3 generation. In order to avoid losing variants, the population for selecting somaclonal variation should be as large as possible. Some of these variants found may be useful for further study or for use in breeding programs.

In vitro digestibility and amino acid composition of pearl millet (Pennisetum typhoides) and other cereals.

The purpose of this study was to compare in vitro digestibility, protein distribution patterns, and amino acid composition of pearl millet with other major cereals. Digestibility values for the pearl millet varieties were higher than that of sorghum and comparable to that of maize. In contrast to sorghum, digestibility of pearl millet and maize did not decrease significantly upon cooking. Protein distribution patterns of uncooked pearl millet and shifts in the different fractions as a result of cooking also resembled that of maize and not sorghum. The amino acid profile of pearl millet is more favorable than that of normal sorghum and normal maize and is comparable to the small grains, wheat, barley, and rice. On the basis of these findings, it appears that pearl millet is a nutritious and well-digested source of calories and proteins for humans.