The present study was conducted to evaluate the effects of feeding whole linseed on the laying performance and egg characteristics in laying hens kept at high ambient environmental temperatures (average 34 ºC; the diurnal temperature range 26 ºC to 41 ºC). Two hundred and forty 38-wk-old white Leghorn laying hens were fed diets containing 0, 5, 10 or 15% whole linseed (as a source of n-3 polyunsaturated fatty acids) for a period of 12 weeks. Egg production was recorded daily, while feed intake and egg characteristics were monitored on weekly basis. The results of the study demonstrated that egg production and feed intake decreased, while feed conversion ratio (FCR) per dozen of eggs increased (p ≤ 0.05) with increasing dietary linseed levels. Egg weight, yolk weight, albumen height, eggshell weight, and eggshell thickness were not influenced (p > 0.05) by linseed levels in the diets offered to the laying hens. The results of the present trial suggest that feeding linseed to the laying hens in hot climates has no detrimental effects on egg characteristics, but has suppressive effects on egg production, feed intake and feed efficiency of laying hens.
With the growing awareness among the general public, the demand for food products rich in omega-3 polyunsaturated fatty acids (n-3 PUFA) has increased over the years. Hen eggs enriched with n-3 PUFA are serving this purpose. Several earlier trials indicated that the addition of n-3 PUFA-enriched feed stuffs in laying hen rations readily promoted the n-3 PUFA contents of egg yolks. A major increase was noticed for linolenic acid content in the egg yolk and also for long chain n-3 PUFA. The egg cholesterol was also decreased to some extent by feeding n-3 PUFA-enriched diets to laying hens. However, the production performance and egg characteristics have been questioned in some of the studies conducted on n-3 PUFA feeding to laying hens. The major problem mentioned was a decrease in the egg weight and egg-yolk weight. It is suggested that more consideration should be given to the performance and egg characteristics in future studies on feeding n-3 PUFA to laying hens.
Despite intense study of neurotransmitters mediating hypothalamic controls of food intake, little is known about which second messengers are critical for these mechanisms. To determine whether adenosine 3',5'-cyclic monophosphate (cAMP) might participate in these mechanisms, we injected the membrane-permeant cAMP analog 8-bromo-cAMP (8-BrcAMP) hypothalamically in satiated rats. Injection of 8-BrcAMP (10-100 nmol) into the perifornical (PFH) and lateral hypothalamus (LH) dose dependently stimulated food intake of up to 15.7 g in 2 h. Significantly smaller responses were obtained with thalamic injections. In contrast to the strong stimulatory effects of PFH and LH 8-BrcAMP, cAMP and 8-bromo-guanosine 3',5'-cyclic monophosphate (100 nmol) were ineffective, suggesting a chemically specific, intracellular action. Consistent with this, combined PFH injection of 7-deacetyl-7-O-(N-methylpiperazino)-tau-butyryl-forskolin dihydrochloride and 3-isobutyl-1-methylxanthine, agents that increase endogeneous cAMP, stimulated eating of up to 9.9 g in 2 h. These results demonstrate that increases in PFH/LH cAMP can elicit complex, goal-oriented behavior, suggesting an important role for cAMP in hypothalamic mechanisms stimulating food intake.
Vitamin C (L-ascorbic acid) was evaluated for its effects on production performance, and plasma ascorbic acid, blood glucose and serum cholesterol levels in heat-stressed laying hens. One hundred and fifty, 72-week-old single comb white Leghorn hens in their second laying year cycle were kept at high ambient environmental temperature (average of 34.5°C; range 28–42°C) throughout the experimental period of 12 weeks. Three levels of vitamin C, 0, 1,000, or 1,200 ppm, were supplemented through drinking water to the treatment groups A (control), B and C, respectively. Hen-housed egg production, efficiency for feed conversion, egg weight and egg mass were improved (P<0.01) in birds receiving vitamin C supplementation when compared to the control birds. Shell thickness was higher (P<0.01) in birds receiving 1,000 ppm vitamin C supplementation compared to those of other groups. However, feed intake, water consumption and rectal temperature of hens were not influenced (P >0.05) by vitamin C supplementation. The birds without vitamin C supplementation showed a higher mortality (P<0.05) among them. The birds receiving vitamin C supplementation had significantly (P<0.01) increased plasma ascorbic acid while decreased blood glucose and serum cholesterol levels when compared to the birds of control group.
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