The effect of protein and energy self-selection on the reproductive performance of turkey hens

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Virginia Polytechnic Institute and State University


Two experiments were conducted to determine the effect of dietary self-selection of protein and energy on the reproductive performance of Large White turkey hens. The first study examined the effect of self-selection on reproductive performance during a production cycle that started in July and ended in December. Hens were maintained on one of two dietary regimes for a 20-week production cycle. Control birds were fed a conventional diet (18% crude protein, 2700 kcal/kg) which contained nutrients at levels recommended by the National Research Council (NRC, 1984). The remaining hens were allowed to select their diet from two feed sources: one relatively high in protein and low in energy (35% crude protein, 1850 kcal/kg) and the other relatively low in protein and high in energy (8% crude protein, 3220 kcal/kg). Hens fed the split diet produced an equal number of eggs as control hens but consumed significantly less feed (p≤.05). The diet that was selected contained approximately 40% less protein than the control diet (p≤.001) which resulted in significantly increased efficiency of protein utilization (eggs/kg protein) for hens fed the split-diet (p≤.001). In addition, the incidence of broodiness was significantly reduced in the split-diet treatment (p≤.10). Egg weight, fertility, hatchability and hatch of fertile eggs were not significantly effected by the dietary regimes. There was significantly greater body weight loss in hens fed the split-diet (p≤.05). Increasing trends in feed, energy, and protein consumptions were noted over the course of production. For this reason a second experiment was conducted to determine if these trends were the result of seasonal affects, due to changing ambient temperatures, or the result of changes in nutrient requirements of the turkey hen occurring with different stages of production.

The second experiment was similar to Experiment 1 except that the production period started in March and ended in July. As in the first experiment, egg production was equal for hens in the two treatment groups. Feed intake and energy intake were not significantly different for hens fed the split and complete diets. However, as in the previous experiment, protein intake was significantly reduced in the split-diet treatment (p≤.001). The incidence of broodiness was again attenuated among split-fed birds (p≤.10). Average daily feed and energy intake appeared to decrease over the course of production which was presumed to be related to increasing ambient temperatures. As in the previous experiment, protein intake increased over the course of production despite increasing environmental temperatures. Therefore, the increased protein selection noted in these two experiments does not seem to be related to hot weather and may indicate an increased protein requirement in the later stages of egg production.

Based on the finding that the incidence of broodiness was reduced among hens fed the split-diet, blood sera from hens in both experiments were analyzed for luteinizing hormone (LH) and prolactin (PRL). Although the incidence of broodiness was significantly reduced among birds fed the split-diet, there was no significant difference in serum LH and PRL concentrations. Therefore, the reduction in the incidence of broodiness that was noted in these experiments was not correlated with changes in the blood concentration of these hormones.