Evaluation of the dietary interaction of calcium and phosphorus in the high producing laying hen

Abstract

1. In a 6 x 7 factorial experiment using 2688 22-week-old laying hens of the Lohmann-SL strain kept in cages (4 birds/cage), diets containing six calcium (20, 25, 30, 35, 40, 45 g calcium/kg) and seven phosphorus concentrations (3.2, 4.2, 5.2, 6.2, 7.2, 8.2, 16.2 g total phosphorus/kg (Pt)) were combined orthogonally. The resulting 42 treatments were replicated 8 times so that a replicate consisted of a double cage of 2 x 4 hens. The experiment lasted 40 weeks (10 x 28 days). 2. The experimental diets, based on maize and soyabean meals contained 11.5 MJ metabolisable energy/kg and 175 g/kg protein. Different dietary calcium and phosphorus contents were obtained by substituting oat hulls with limestone and dicalcium phosphate. 3. Mortality, egg production, egg weight, egg mass, food intake and food conversion efficiency were determined as well as the breaking strength, thickness of shells and the percentage of eggs with defective shells. 4. All responses measured were significantly influenced by the variance sources (calcium, phosphorus, interaction). Most of the production traits responded asymptotically to increasing dietary phosphorus concentration, the greatest increases or decreases generally being seen between 3.2 and 5.2 g Pt/kg. Further but weaker increases were seen between 5.2 and 8.2 or 16.2 g Pt/kg. 5. Increases in dietary calcium content always resulted in curvilinear responses. In all cases optimal effects were obtained with diets containing 25 g calcium/kg and the worst values at 45 g calcium/kg. The interaction between calcium and phosphorus was recognised by strong performance depressions and a high mortality at combinations of the lowest phosphorus concentration (3.2 g/kg) with high calcium contents (35 to 45 g/kg). These were largely offset by increasing dietary phosphorus. Thus, between 7.2 and 16.2 g Pt/kg and 25 and 45 g Ca/kg a plateau was formed where only small differences in egg production were observed. 6. From the three egg shell characteristics measured, breaking strength and shell thickness responded differently to the percentage of eggs with defective shells. While breaking strength and shell thickness were respectively negatively and positively influenced by increasing dietary phosphorus and calcium contents, both elements affected the proportion of eggs with defective shells.(ABSTRACT TRUNCATED AT 400 WORDS)

Sprinkling coarse marble powder during the afternoon, toward the end of the laying period, may increase eggshell quality

“…(1992) who reported that the extra calcium feeding increased shell weight. Our results with respect to egg production and FE obtained from the 1.50 g marble added group are in line with Hartel (1990) who showed that high levels of dietary calcium (3.5–4.5%) slightly decreased egg mass. The high dose of marble (1.50 g) in the present study decreased egg production possibly because of disruption to Ca : P ratios, and/or dilution of protein and energy in the complete diet which had a fixed Ca : P ratio.…”

“…Previous studies report that high levels of dietary calcium do not affect eggshell breaking strength, thickness (Hartel 1990) or quality (Keshavarz 1986), and that a step‐up phase feeding system (3.5, 4.5, 5.5% Ca) is also without effect on eggshell quality (Keshavarz & Nakajima 1993). However, in the present study, the 0.75 and 1.5 g marble addition to complete diet improved eggshell quality (i.e.…”

“…Several studies have been carried out to alleviate the decrease in egg production and eggshell quality observed in old hens (Lennards & Roland 1981; Keshavarz 1986; Roland 1986; Hartel 1990; Keshavarz et al . 1993; Richter et al .…”

“…In old hens (80 weeks of age), 5% dietary calcium had a little effect on eggshell quality (Keshavarz 1986). Hartel (1990) reports that the increase from 3.5–4.5% calcium in hens fed 0.27–0.47% available phosphorus does not affect shell breaking strength or thickness, but tends to slightly decrease food intake and egg mass. Calcium consumed by laying hens during the afternoon is used for shell formation.…”

Effects of calcium diet supplements on egg strength in conventional and furnished cages, and effects of 2 different nest floor materials

“…The dietary level of calcium affects the feed and energy intake of hens, as, for example, Härtel (1990) and Roland and Bryant (1994) demonstrated. Feed intakes lower in FC than in CC have been reported by Elson and Croxall (2006) and Valkonen et al (2006), whereas others (Hetland et al, 2004) have reported higher feed intakes in FC than in CC.…”