Effects of S6-strain Mycoplasma gallisepticum inoculation at ten, twenty-two, or forty-five weeks of age on the blood characteristics of commercial egg-laying hens.

In 2 consecutive trials of the current study, the effect of the age of application of S6-strain Mycoplasma gallisepticum (S6MG) inoculation on the blood characteristics of commercial layers housed and maintained under controlled conditions was determined. The ages of inoculation compared were those before lay at 10 wk of age, during onset of lay at 22 wk of age, and during postpeak lay at 45 wk of age. In each trial, hematocrit, plasma protein, and serum cholesterol, triglycerides, and Ca were determined at 20, 24, 32, 43, 47, and 58 wk of age. The data from both trials were pooled then analyzed together, whereas, data from wk 20 (effect of 10-wk S6MG inoculation); data from wk 24, 32, and 43 (effects of 10- and 22-wk S6MG inoculations); and data from wk 47 and 58 (effects of 10-, 22-, and 45-wk S6MG inoculations) were analyzed separately. At wk 20, hematocrit was higher in birds inoculated with S6MG at 10 wk compared with sham-inoculated birds, and across wk 24, 32, and 43, serum Ca was higher in birds inoculated with S6MG at 10 or 22 wk compared with those that were sham-inoculated. Serum Ca level across wk 47 and 58 was higher in birds inoculated with S6MG at 10 wk compared with sham-inoculated controls and birds inoculated with S6MG at 22 wk, with 45-wk S6MG-inoculated birds being intermediate. The response of serum cholesterol level at 47 wk to S6MG inoculation at either 10, 22, or 45 wk compared with controls was nearly opposite to that of the response observed at 58 wk. However, serum triglycerides were depressed only at wk 47 due to the 45-wk S6MG inoculation compared with all other treatments. Variable post-peak alterations in serum Ca and lipids occur in response to the timing of S6MG inoculation in layers housed under controlled conditions.

Effects of S6-strain Mycoplasma gallisepticum inoculation at ten, twenty-two, or forty-five weeks of age on the egg yolk composition of commercial egg-laying hens.

Commercial laying hens maintained under controlled conditions were experimentally inoculated with the S6 strain of Mycoplasma gallisepticum (S6MG) at 45 wk of age. This resulted in depressed liver lipid concentration, and inoculations at 20 and 45 wk affected the size of various portions of the reproductive tract. In 2 consecutive trials of the current study, the effect of age of application of S6MG inoculation on the egg yolk characteristics of commercial layers similarly housed and maintained under controlled conditions was determined. The ages of inoculation compared were prior to lay at 10 wk of age, during onset of lay at 22 wk of age, and during postpeak lay at 45 wk of age. In each trial, yolk moisture and total lipid content were determined at 24, 32, 43, 47, and 58 wk of age. Yolk cholesterol concentration and yolk fatty acid profiles at wk 47 and 58 were also examined. Data from wk 24, 32, and 43 (effects of S6MG inoculations at 10 and 22 wk) and data from wk 47 and 58 (effects of S6MG inoculations at 10, 22, and 45 wk) were analyzed separately. The data of both trials were pooled then analyzed together. Across wk 47 and 58, percentage yolk lipid was significantly lower in eggs laid by birds inoculated at 10 wk compared with those inoculated at 45 wk. Sham-inoculated control and 22-wk inoculated groups had intermediate percentage yolk lipids. Compared with sham-control and 10-wk S6MG inoculation groups across wk 47 and 58, yolk myristic, oleic, and linolenic acid concentrations were reduced, whereas yolk stearic and arachidonic acid levels were increased by either 22- or 45-wk S6MG inoculations. In comparison with all other treatment groups at wk 47, yolk linoleic acid concentration was reduced by S6MG inoculation at 45 wk. Variable postpeak alterations in yolk total lipid and fatty acid content occur in response to the timing of S6MG inoculation in layers housed under controlled conditions.

Effects of S6-strain Mycoplasma gallisepticum inoculation at 10, 22, or 45 weeks of age on the digestive and reproductive organ characteristics of commercial egg-laying hens.

Experimental inoculation of commercial laying hens with the S6-strain of Mycoplasma gallisepticum (S6MG) at 20 wk of age, while being maintained under ideal conditions, has previously been shown to affect the lengths and weights of various portions of the reproductive tract. Two trials were conducted in the current study to compare the effects of S6MG inoculation prior to lay at 10 wk of age, during onset of lay at 22 wk of age, and during lay at 45 wk of age on the digestive and reproductive organs of commercial layers similarly housed and maintained under ideal conditions. In each trial, liver weight, liver moisture and lipid concentration, incidence of fatty liver hemorrhagic syndrome, ovary weight, ovarian mature follicle numbers, weights and lengths of the oviduct and oviductal regions, and weights and lengths of the small intestine and small intestinal regions were examined at 60 wk of hen age. At 60 wk, liver lipid concentration was depressed, and isthmus weight, as a percentage of total oviduct weight, was increased in birds that had been inoculated with S6MG at 45 wk. Alterations in liver lipid content and weight of the isthmal portion of the oviduct may occur in response to S6MG inoculation during the later stages of production in layers housed under ideal conditions.

Effects of S6-strain Mycoplasma gallisepticum inoculation at ten, twenty-two, or forty-five weeks of age on the performance characteristics of commercial egg laying hens.

Experimental inoculation of commercial laying hens, maintained under controlled conditions, with the S6-strain of Mycoplasma gallisepticum (S6MG) at 10 wk of age has previously been shown to affect the lengths and weights of various portions of the reproductive tract without affecting subsequent performance. Two trials were conducted to compare the effects of S6MG inoculation at 10 wk of age (prior to lay), 22 wk of age (onset of lay), and 45 wk of age (during lay) on performance characteristics in commercial layers housed and maintained under controlled conditions, as in previous studies. In each trial, BW, mortality, egg production, egg weight, eggshell weight per unit of surface area, percentage eggshell weight, percentage albumen weight, percentage yolk weight, and yolk weight per albumen weight ratio were examined at various ages throughout an entire laying cycle. Across wk 47 and 58 (age periods after the last 45 wk inoculation), eggshell weight per unit of surface area and percentage eggshell weight were significantly reduced in birds that had received an S6MG inoculation at 45 wk of age when compared with birds that had not received an S6MG inoculation or had been inoculated with S6MG at either 10 or 22 wk of age. Alterations in eggshell quality in response to S6MG may become evident only in older birds that are experiencing declines in production when housed under controlled conditions.