"Benchmark" - a large observational study of Ontario beef breeding herds: Study design and collection of data

The methods used in a large field study which investigated the health and productivity of Ontario beef breeding herds are described. Beginning in the calving season of 1986, 180 breeding herds on 170 randomly sampled farms were followed for a two year period, using producer records and annual farm visits.

The response (cooperation) rate among the eligible producers initially contacted was 70%. Approximately two-thirds of producers maintained individual animal records, primarily calving season records. Approximately 40% recorded disease occurrences.

The advantages, disadvantages, and interpretation of “on-farm” observational studies are discussed.

     

Relationship between equivalent salt solution series of different soils

Equivalent salt solution series have been previously defined as solutions with combinations of sodium absorption ratio (SAR) and electrolyte concentration (E_c) producing the same extent of clay swelling in a given soil. The present study shows that there is a high (r²>0.96) positive correlation between log E_c and log SAR of equivalent salt solutions series, in the equation: where a₁ and b₁ are constants for each equivalent salt solution series for a given soil. Log a₁ could also be represented as a linear function of b₁ resulting in the equation: where a₂ and b₂ are constants for a given soil. Solving this equation using any given value of b₁ yields the combinations of SAR and E_c which make up each equivalent salt solution series for a given soil. The relationship between log a₁ and b₂ for three soils from western United States, namely Waukena, Pachappa and Grangeville, was similar, with their combined data having a r² value of 0.96. This indicated that a single set of equivalent salt solution series values could be used for these three soils which have different clay contents and clay mineralogy. Prediction of hydraulic conductivity decreases with E_c reduction at given values of SAR in red-brown and alluvial soils from southern Tasmania, using the equivalent salt solution series values for Waukena soil, showed similar patterns to measured values and also to those predicted using the equivalent salt solution values applicable to the respective Tasmanian soils. Thus, available data indicate that the same set of equivalent salt series could be applied to the five soils studied. If further testing shows that a single set of equivalent salt solutions values could be applied to all or large groups of soils, this would facilitate the application of the equivalent salt solution concept to predict salt solution flow in the field.     

Divergent selection for postweaning feed conversion in Angus beef cattle: II. Genetic and phenotypic correlations and realized heritability estimate.

A single generation divergent selection study, replicated four times (1983, 1984, 1985, and 1986), was conducted to assess genetic differences between progeny of high and low feed conversion sires in Angus beef cattle and to determine correlated response for weight gain (ADG140), feed intake (AVFD140), and BW (OFFTSTWT) in a time- (140-d) and fat-constant (8.9 mm) period. Realized heritability estimates for unadjusted (feed/gain; FEFF140; .26) and adjusted feed conversion (adjusted as recommended by the BIF, 1986; ADJFDEFF; .46) were obtained. The difference in heritability estimates reflects variation accounted for by adjustment for BW differences, and thus maintenance requirements, of individual progeny. Phenotypic and "pseudo" realized genetic correlations of FEFF140 with ADG140, AVFD 140, and OFFTSTWT were -.33 and -.66, .49 and -.26, and .15 and -.41, respectively. Phenotypic and "pseudo" realized genetic correlations of ADJFDEFF with ADG140, AVFD140, OFFTSTWT, and FEFF140 were -.54 and -.59, .30 and -.23, .27 and -.36, and .97 and .49, respectively. Subcutaneous fat (as estimated by ultrasonic measurement; BF140) had phenotypic and "pseudo" realized genetic correlations with FEFF140 of -.33 and .66, respectively, and with ADJFDEFF of -.44 and -.58, respectively.     

Husbandry of animals on land and in water: similarities and differences.

The husbandry of aquatic animals originated in China in approximately 1,100 B.C., thousands of years after the beginning of animal agriculture. The practice did not reach Europe until the Middle Ages. Aquaculture apparently was not very important in Western Europe. The early immigrants from that region did not include fish with the other food animals that they brought with them to the New World. The practice of aquaculture finally came to the United States in the mid-nineteenth century, where it was used for the production of trout for stocking coldwater ponds and streams for sport fishing. Later, cultural practices were extended to warmwater species such as the largemouth black bass and the channel catfish. Thus, aquaculture in the United States was derived from recreational fishing rather than from food production, and from fisheries management rather than from animal science. There are important differences in the hydrosphere and atmosphere as cultural environments. Differences in composition, density, response to physical force, latent heat of fusion, specific heat, transparency, viscosity, and erosiveness of air and water result in different problems for land animal and aquatic animal culturists. Aquaculturists work primarily with "cold-blooded" ("lower") animals, whereas agriculturists work with "warm-blooded" ("higher") animals. In comparison with warm-blooded land animals, cold-blooded aquatic animals are less independent of changes in their environment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clearance of ovine isolates of Bordetella parapertussis from murine trachea and lungs

Thirty-six mice were inoculated intranasally with Bordetella parapertussis organisms (isolated from sheep with chronic non-progressive pneumonia) to study their deposition and clearance in the lower respiratory tract. The deposition of the organism was greater in the trachea than in the lungs. At 48 hours after inoculation, almost 100% of organisms were cleared from the trachea but only 55% of organisms were cleared from the lungs. This result correlates well with the morphological changes seen previously in the pulmonary parenchyma and airways of mice and lambs experimentally infected with this organism.