title: Further investigations on the effect of dietary manipulation of protein, phosphorus, and calcium for reducing their daily requirement for laying hens.
abstract: Experiments were conducted to determine the possibility of reducing the daily requirement of laying hens for Ca, available P (AP), and protein by providing the hens with adequate levels of these nutrients only during those hours of the day that the physiological need for these nutrients for formation of various components of the eggs are increasing. The results of the Ca experiment indicated that the daily Ca requirement cannot be reduced by providing the hens with adequate levels of Ca during the afternoon (1500 to 2100 h) and inadequate Ca level during the morning (0500 to 1500 h). Providing the hens with most of the daily Ca need during the afternoon did not have a beneficial effect on shell quality as compared to the control group that received a diet with 3.5% Ca during the morning and the afternoon. On the other hand, inadequate Ca intake during the afternoon adversely affected shell quality as compared to the control group (P < 0.05). The AP experiment indicated that egg production performance and shell quality can be maintained satisfactorily as long as the daily intake of AP is adequate, regardless of whether most of the AP is consumed during the morning or the afternoon. Egg production and shell quality of hens fed a diet with 0.4% AP during the morning and 0.1% AP during the afternoon or 0.1% AP during the morning and 0.4% AP during the afternoon were not different than the control group that received a diet with 0.25% AP during the morning and the afternoon. The results of two protein experiments failed to indicate that egg production performance of laying hens can be maintained satisfactorily by providing them with an adequate level of protein (16%) only during the morning and inadequate level of protein (10%) during the afternoon or, conversely, compared to the control group that received a diet with 16% protein both during the morning and afternoon (P < 0.05). The supply of adequate protein with sufficient amino acids, during the morning and the afternoon, was required for satisfactory maintaining egg production performance. Under the conditions selected for the conduct of this study, the results of the current experiments, combined with those of a previous report, failed to support the hypothesis that satisfactory performance may be maintained by providing the hens with adequate levels of protein, AP, and Ca only during those hours of the day when the physiological need for these nutrients for formation of various components of the egg are increasing.
authors.affiliation: Department of Animal Science, Cornell University, Ithaca, New York 14853, USA. kk33@cornell.edu
authors.forename: K
authors.initials: K
authors.lastname: Keshavarz
mesh_terms: D000821:Animal Feed; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002645:Chickens / Q000502:physiology*; D002940:Circadian Rhythm; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D004435:Eating; D004528:Egg Shell / Q000502:physiology; D005260:Female; D009751:Nutritional Requirements; D010058:Oviposition; D010758:Phosphorus / Q000008:administration & dosage*; D012621:Seasons
chemical_list: D002136:Calcium, Dietary; D004044:Dietary Proteins; D010758:Phosphorus