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The main objective of the present study was to determine the minimum level of dietary plant oil supplementation that results in full recovery from loss of hatchability induced by conjugated linoleic acid (CLA). Another objective was to define the changes in egg yolk fatty acid composition associated with the loss and recovery of hatchability. Shaver hens were assigned to groups of 8 and were fed a diet containing either no CLA plus 0.5% soybean oil (control) or 0.5% CLA (1:1 mixture of cis-9, trans-11 and trans-10, cis-12 CLA) plus 0, 2, 4, 6, or 8% soybean oil for 15 d. Supplementation with CLA (CLA plus 0% soybean oil) resulted in complete loss of hatchability of fertile eggs. Hatchability was progressively improved by increasing doses of soybean oil, and full recovery of hatchability compared with the control levels was achieved at 6% soybean oil. There was no further improvement in hatchability when 8% soybean oil was added to the CLA-supplemented diet. Loss of hatchability was associated with a 2- to 3-fold decrease in desaturase ratios (cis-9 C16:1/C16:0 and cis-9 C18:1/C18:0) in the egg yolk total lipids, indicating marked inhibition of delta-9 desaturase in the chicken liver. In addition, the concentration of arachidonic acid was observed to decrease. Recovery of hatchability was associated with an increased proportion of linoleic acid and linolenic acid in the egg yolk. However, there was no change in desaturase ratios, suggesting that delta-9 desaturase inhibition persisted. Increased incorporation of dietary linoleic and linolenic acids might have compensated for the reduced levels of palmitoleic and oleic acid, thus allowing for the improvement in hatchability.

1. Effects of preservation method (drying or air-tight storage of whole grain and ensiling of rolled high-moisture grain) and beta-glucanase supplementation (Econase) on apparent ileal amino acid digestibilities and metabolisable energy content of barley were evaluated with Ross broiler chickens. In addition, the effect of barley preservation method was assessed using Leghorn cockerels. 2. Birds were given either a semi-purified soyabean meal basal diet or a mixture of the basal diet and barley (50:50 on dry matter basis). Apparent ileal digestibilities (AID) of nutrients were assessed using the slaughter technique. AID of nutrients and nutrient digestibility measured using excreta (AED) were determined using chromium mordanted straw as an indigestible marker. 3. In broilers, AID of amino acids, dry matter and organic matter were lower for dried than air-tight stored barley, particularly for diets based on ensiled barley. In cockerels, barley preservation method had no effect on amino acid AID. The AED of nutrients and nitrogen corrected apparent metabolisable energy content (AMEn) was highest for ensiled barley across both experiments. 4. beta-glucanase supplementation increased nutrient digestibility, phosphorus retention and AMEn content of air-tight stored and dried barley diets in particular but had only negligible effects on ensiled barley. Beta-glucanase improved the AID of amino acids in dried barley but not in air-tight stored or ensiled barley. 5. Amino acid digestibilities were lower in broilers than cockerels and the effect of barley preservation on feeding value of barley was different for broilers and cockerels.

Digesta viscosity, ileal transit time of digesta, apparent ileal protein digestibility and apparent metabolisable energy (AME(N)) of diets based on wheat and dehulled barley (WB), oats (O) or a mixture of these (WBO) fed as such or with enzyme supplementation in three- and six-week old turkeys and broilers were investigated. In addition, differences between ileal digestibility and AME(N) calculated by using titanium dioxide (TiO2), chromic oxide (Cr2O3) or acid insoluble ash (AIA) as indigestible markers were compared. Digesta viscosities were generally moderate reaching from 2.5 mPa x s to 7.3 mPa x s. The highest viscosities were observed in WBO diets. Viscosities were reduced with age in broilers, and were generally higher in turkeys than in broilers, especially at six weeks of age. Digesta retention time in ileum was elongated with age of the birds, pronouncedly in broilers. Oat inclusion to the diets decreased retention time especially in broilers at six weeks of age. Apparent ileal digestibility of protein ranged from 0.64-0.83, was lower at six weeks of age than at three weeks of age and generally lowest in O diets, especially in turkeys. AME(N) of the diets ranged from 11.2-13.4 MJ/kg being higher at six weeks of age than at three weeks of age. AME(N) of Diets O was the lowest but AME(N) of WBO diets was higher than that of WB diets indicating a synergistic interaction of cereals, this trend being more pronounced in broilers. Enzyme supplementation decreased viscosity and improved AME(N) in most diets, but did not affect ileal protein digestibility. Differences between ileal digestibility estimates obtained with TiO2 or Cr2O3 were small and mainly not significantly different from 0. AME(N) estimates were generally higher when calculated with Cr2O3 than with TiO2. AIA gave remarkably lower AME(N) values than TiO2 (the significant differences ranging from 0.24-0.94 MJ/kg). In addition, effects of markers on AME(N) estimates interacted with age of the birds and dietary treatments.