A formal method of determining the dietary amino acid requirements of laying‐type pullets during their growing period

1. The amino acid requirements of laying type pullets during the growing period can be estimated by measuring the growth of different components of the body and making use of nutritional constants that define the amount of each amino acid that is required for the production of the tissues being formed.

2. In this experiment, carcase analyses of each of three breeds of pullets were conducted at weekly intervals throughout the growth of the pullets, to 18 weeks of age. Measurements were made of body weight, gut‐fill and feather weight, and chemical analyses consisted of water, protein, lipid and ash measurements of both the body and the feathers. Each age group comprised 10 birds of each breed.

3. Gompertz functions accurately estimated the growth of both body protein and feather protein, to 18 weeks of age, from which the rate of growth of these two components of the body could be estimated. The mature weight of pullets was overestimated by the Gompertz growth curve, which may indicate that a pullet ceases to increase in body protein content once sexual maturity has been reached.

4. Using allometric relationships between the chemical components of the body and of feathers, all the components of growth could be estimated from the growth of body protein and feather protein. These components were then added together to determine the growth rate of the body as a whole.

5. The daily amino acid requirements for 4 functions were calculated, namely, those for the maintenance of body protein and feather protein, and for the gain in body protein and feather protein. These requirements were then summed to determine the requirement of pullets on each day of the growing period.

6. Using the ‘effective energy’ system, the amount of energy required by these pullets was calculated for each day of the growing period, from which the desired daily food intake of the pullets could be predicted. By dividing the amino acid requirement by this daily food intake it was possible to determine the concentration of amino acids that would be needed in the diet in order to meet the requirements of a pullet.

7. The results indicate that the ratio between the requirement for lysine and for methionine and cysteine changes dramatically during the growing period, negating the concept of a fixed ratio between all the amino acids during growth.

8. The above process is the first step in determining the optimal feeding programme for a population of pullets of a given genotype. The constraining effects, of the diet being offered and of the environment in which the pullets are housed, on the food intake and growth rate of each pullet have to be estimated, and such a theory can then be expanded to include all the individuals in the population. Only by the use: of simulation models can all these constraining effects be considered simultaneously.     

Onondaga Lake and the dynamics of chloride in the Oswego River

The temporal distribution of chloride concentration in the Oswego River was determined at 6 hr intervals for a 3 mo period during the summer of 1982. The dynamics of relative flow and chloride contributions from the three major sources forming the Oswego River, and the dynamics of flow releases from one of the sources, chloride-polluted Onondaga Lake, were determined from the above measurements, available chloride concentrations, and flow data for the system, through application of a simple mass balance on chloride. The chloride concentration and load in the Oswego River were found to be highly variable with time, and largely due to the dynamics of flow release from Onondaga Lake. The chloride distribution in the Oswego River, with its unique dynamics and chemically conservative nature, make it a valuable hydraulic tracer for the system.     

Comparison of two radiographic techniques for evaluation of hip joint laxity in 10 breeds of dogs

OBJECTIVE: To evaluate hip joint laxity in 10 breeds of dogs via 2 radiographic techniques. ANIMALS: 500 clinically normal dogs. DESIGN: Prospective study. PROCEDURE: Radiographs obtained via routine hip joint evaluations performed in sedated dogs of 10 popular breeds were randomly selected from a database. Measurements of distraction index (DI) and hip-extended index (HEI) on 1 hip joint radiograph randomly chosen from each dog were made. RESULTS: Mean age of dogs was 20.7 months. Mean HEI was 0.17 (range, 0.0 to 0.72) and mean DI was 0.44 (range, 0.07 to 0.96). Borzois had uniformly tight hip joints as judged by use of both methods and were considered the gold standard by which hip joint laxity was judged (all Borzois had DI < or = 0.32). Overall, DI was significantly greater than HEI. Within each breed, mean DI was always greater than mean HEI. Significant differences were detected among breeds for HEI; however, compared with DI, the magnitude of differences among breeds was less. CONCLUSIONS AND CLINICAL RELEVANCE: Distraction radiography detected the greatest range and magnitude of passive hip laxity in the 10 breeds of dogs. The difference in values between breeds known to have high prevalence of canine hip dysplasia and those in Borzois was greater for DI than for HEI. Breeds must be evaluated individually because of inherent differences in hip joint laxity.     

Risk of human immunodeficiency virus (HIV-1) infection among laboratory workers

In a prospective cohort study of 265 laboratory and affiliated workers, one individual with no recognized risk factors for human immunodeficiency virus type 1 (HIV-1) infection was HIV-1 seropositive at the time of entry into the study. Molecular analyses of two HIV-1 isolates derived in two independent laboratories from a blood sample from this worker showed that the isolates were indistinguishable from a genotypic form of HIV-1 present in the H9/HTLV-IIIB cell line. Exposure to this strain of virus most probably occurred during work with concentrated virus or culture fluids from virus-producing cell lines under standard Biosafety Level 3 containment. Although no specific incident leading to this infection has been identified, undetected skin contact with virus culture supernatant might have occurred. This worker was the only one found to be positive among the subgroup of 99 workers who shared a work environment involving exposure to concentrated virus. The incidence rate of 0.48 per 100 person-years exposure indicates that prolonged laboratory exposure to concentrated virus is associated with some risk of HIV-1 infection, which is comparable to the risk for health care workers experiencing a needle stick exposure. While none of the ten workers with parenteral exposure to HIV-1 in this cohort became infected, a worker in another laboratory did seroconvert following an injury with a potentially contaminated needle. Strict Biosafety Level 3 containment and practices should be followed when working with concentrated HIV-1 preparations, and further refinement of the procedures may be necessary.     

Use of the caudolateral curvilinear osteophyte as an early marker for future development of osteoarthritis associated with hip dysplasia in dogs

OBJECTIVE: To determine the relationship between the caudolateral curvilinear osteophyte (CCO) and osteoarthritis associated with hip dysplasia in dogs. DESIGN: Longitudinal cohort study. ANIMALS: 48 Labrador Retrievers from 7 litters. PROCEDURE: In each of 24 sex- and size-matched pairs fed the same diet, a restricted-fed dog was fed 25% less than a control dog for life. The dogs' hips were evaluated in the standard ventrodorsal hip-extended radiographic projection at 16, 30, and 52 weeks of age and then yearly for life. Histologic examination of hip joint tissues was performed on 45 dogs. RESULTS: Median age at death was 11.2 years. Adjusting for feeding group, dogs with a CCO were 3.7 times as likely to develop radiographic signs of osteoarthritis than those without a CCO. Stratified by diet, 100% of the control dogs with a CCO developed radiographic signs of osteoarthritis and 55% of restricted-fed dogs with a CCO developed radiographic signs of osteoarthritis. The CCO was the first radiographic change seen in 22 of 29 (76%) dogs with osteoarthritis. Overall, 35 of 37 (95%) dogs with a CCO had histopathologic lesions of osteoarthritis. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate a relationship between a CCO on the femoral neck and subsequent development of radiographic signs of osteoarthritis in Labrador Retrievers evaluated over their life span. A CCO is an important early radiographic indication of osteoarthritis associated with canine hip dysplasia.     

Breaking the ice: the introduction of biofouling organisms to Antarctica on vessel hulls

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