Selection for a high (H) or low (L) incidence of tibial dyschondroplasia (TD) at 7 wk of age was practiced for four generations in broiler breeders using low intensity x-ray imaging (Lixiscope) for TD diagnosis. As a result, broiler lines with H or L incidence of TD at 7 wk of age were developed keeping a randomly selected control (C) broiler line. A total of 4,232 chicks were hatched representing 172 sires and 612 dams over four generations for the H, L, and C lines. The TD scores at 7 wk were collected on 4,056 broilers. Incidence of TD at 4 and 7 wk of age were studied in the C, H, and L lines of broilers. Direct response to selection in the H and L lines were estimated per generation and per weighted cumulative selection differential (WCSD). Total WCSD deviation from the C line for incidence of TD at 7 wk of age was 1.496 and -.42 units for the H and the L lines, respectively. The response per generation for incidence of TD at 7 wk of age for the H line was .153 +/- .028 units. The realized heritability for the H line for incidence of TD at 7 wk of age was .437 +/- .065. The incidence of TD was not significantly decreased in the L line at 7 wk of age.

The relative biological availability of Mn in reagent-grade (RG) Mn sources was tested using 41 Rambouillet crossbred wether lambs in a completely randomized design. Lambs were fed a basal corn-soybean meal-cottonseed hull diet (37.6 ppm Mn, DM basis) or this basal diet supplemented with 0, 1,500, 3,000 or 4,500 ppm Mn from RG MnSO4.H20 or 3,000 ppm Mn from RG MnO, MnO2 and MnCO3. Feed intake was restricted to 1,000 g/hd daily during the 21-d experimental period. There was a decrease (P less than .01) in daily feed intake by sheep fed 4,500 ppm Mn from MnSO4. Liver, kidney and bone Mn concentrations increased (P less than .05) with MnSO4 supplementation. Liver was most responsive to dietary Mn, followed by kidney and bone. Based on multiple linear regression slopes for liver, kidney and bone Mn concentrations, relative bioavailability of Mn from MnO, MnO2 and MnCO3 averaged 57.7, 32.9 and 27.8%, compared with 100% for MnSO4.

Selection for a high or a low incidence of tibial dyschondroplasia (TD) at 7 wk of age was practiced for four generations in broiler breeders keeping an unselected control (C) line and using low intensity X-ray imaging for TD diagnosis. The incidence of TD, BW at 4 and 7 wk of age, age at first egg, and egg production for the first 12 wk of production were determined in the four generations. Age at initial semen production and semen volume and concentration of males were determined only in Generations 3 and 4. The TD scores and BW at 7 wk were collected on 1,366, 1,301, and 1,389 broilers from the C, high (H), and low (L) incidence of TD lines. Incidence of TD at 7 wk in the fourth generation was 16.1, 61.9, and 3.5% for the C, H, and L lines, respectively. There were no significant differences in BW between the H and L lines in Generations 1, 3, or 4. However, in Generation 2, the H line was heavier (P < .01) than the L line. Second generation H line broilers with TD were heavier than those without TD at 4 and 7 wk of age (P < .01). There were no significant differences in age at first egg, age at semen production, or in semen volume between the H and the L lines. Egg production in the L line was greater (P < .01) than that of the H line in all four generations, and semen concentration was also greater (P < .01) in Generations 3 and 4.(ABSTRACT TRUNCATED AT 250 WORDS)

An experiment was conducted to study the relative biological availability of Mn from inorganic Mn sources using 288, 1-day-old male Cobb feather-sexed chicks. Chicks were fed a basal corn-soybean meal diet (82.5 ppm Mn, as-fed basis) ad libitum or the basal diet supplemented with 0, 1,000, 2,000, or 3,000 ppm Mn from reagent grade (RG) MnSO4.H2O, MnO RG, or feed grade (FG) Oxide A, B, or C for 21 days. Bone and kidney Mn concentrations were used to estimate bioavailability. Manganese source and level had no effect on chick performance. Uptake of dietary Mn by bone and kidney from all sources was highly linear (P less than .001). Based on multiple linear regression slopes from bone Mn concentrations, the relative bioavailability values of MnO RG and MnO FG A, B, and C were 81.9 +/- 6.0, 93.1 +/- 6.7, 75.0 +/- 3.6, and 70.3 +/- 5.7, respectively, compared with 100% for MnSO4; those based on kidney Mn were 85.7 +/- 7.9, 68.0 +/- 7.5, 52.2 +/- 4.2, and 53.0 +/- 7.3, respectively.

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