Long-term effects of dietary calcium and phosphorus level, and feed form during rearing on egg production, eggshell quality and bone traits in brown laying hens from 30 to 89 weeks of age

The effects of feeding strategies during rearing (0-16 wk) of brown laying hens on mid and end laying performance (30-89 wk) were studied. The rearing feeding strategies followed a 3 × 2 factorial arrangement with feed form; mash with inclusion of 3% finely ground wheat straw (MWS), crumbles with inclusion of 3% finely ground wheat straw (CWS), and crumbles with inclusion of 3% unground oat hulls as fiber sources (COH) at 2 dietary Ca and P levels (high or low Ca-P). Feed conversion ratio improved with COH and MWS compared with CWS from 30 to 59 wk. Rate of lay and egg mass production showed a feed form × Ca-P interaction from 60 to 89 wk. Low Ca-P led to a higher egg production, but only when COH and MWS were fed. BW at 89 wk was higher with CWS compared to COH and MWS. BW uniformity was better with COH compared to MWS at 51 wk and both CWS and MWS at 67 wk. Tibia characteristics were not clearly affected by treatment, although there was a feed form × Ca-P interaction on compression at 89 wk, where compression was lower with MWS and low vs. high Ca-P. Low Ca-P during rearing led to higher eggshell thickness, compared to high Ca-P at 45 wk of age, but breaking strength was lower with low vs. high Ca-P at 75 wk. Although eggshell quality was affected by Ca-P and there were some interactions with feed form at some ages, the effect was not consistent. There was no clear relationship between eggshell quality and tibia characteristics. It was concluded that feeding low Ca-P in combination with COH and MWS during the rearing period positively affects egg production during late lay. Also, dietary Ca-P levels, compared to commercial practice, can be lowered during rearing, as this will not affect eggshell quality and bone mineralization at later ages.

Low-calcium diets increase duodenal mRNA expression of calcium and phosphorus transporters and claudins but compromise growth performance irrespective of microbial phytase inclusion in broilers

The hypothesis that dietary inclusion of microbial phytase improves apparent calcium (Ca) digestibility thereby allowing a lower dietary Ca inclusion without compromising growth performance was tested. One-day-old male Ross 308 broilers (25 birds/pen, 9 pens/treatment) were assigned to 8 experimental diets containing one of 4 dietary Ca to retainable P (rP) ratios (1.3, 1.8, 2.3, and 2.8) with (1,000 FTU/kg) or without microbial phytase. On d 21 to 23, digesta from different intestinal segments of 8 birds per pen were collected to determine apparent Ca and P digestibility. Mid duodenal mucosa was collected for expression of Ca (CaBP-D28k, PMCA1) and P (NaPi-IIb, PiT-1, PiT-2, and XPR1) transporters by RT-qPCR. Dietary phytase inclusion in low Ca/rP diets increased Ca digestibility in the distal ileum (P_interaction = 0.023) but not the proximal or distal jejunum. Broilers receiving the lowest Ca/rP displayed the lowest body weight gain, highest feed conversion ratio (P < 0.001), and lowest tibia strength, irrespective of dietary phytase inclusion. Incremental dietary Ca/rP linearly reduced P digestibility to a greater extent in the absence of phytase in the distal jejunum and ileum (P_interaction = 0.021 and 0.001, respectively). Incremental dietary Ca/rP linearly reduced serum P more in phytase-free diets (P_interaction < 0.001), and lowered duodenal expression of P transporters NaPi-IIb, PiT-2, and XPR1 (P = 0.052, 0.071 and 0.028, respectively). Incremental dietary Ca/rP linearly increased (P < 0.001) serum Ca irrespective of phytase inclusion, accompanied by a lower (P < 0.001) duodenal expression of Ca transporters CaSR, CaBP-D28k and PMCA1 and Ca-pore forming claudins CLDN-2 and CLDN-12. Dietary phytase increased (P = 0.026) NaPi-IIb but reduced (P = 0.029) CLDN-2 expression. Incremental Ca/rP reduced Ca and P digestibility, increased serum Ca, lowered serum P and inhibited mRNA levels of Ca and P-related transporters, indicating that these transporters and CLDN contribute to the observed effect of dietary Ca and phytase on Ca and P absorption. Despite the improvement in Ca digestibility, dietary phytase did not restore the compromised growth performance and tibia strength of broilers fed a Ca-deficient diet, leading to rejection of the hypothesis.

The effects of dietary calcium and phosphorus level, and feed form during rearing on growth performance, bone traits and egg production in brown egg-type pullets from 0 to 32 weeks of age

In a 3 × 2 factorial arrangement, effects of feed form (crumbles (CWS), mash (MWS), both with inclusion of 3% finely ground wheat straw, or crumbles with inclusion of 3% oat hulls (COH)), and dietary Ca and P (high and low Ca-P) from 0 to 16 wk of age were studied on growth performance, bone characteristics, and gizzard development of egg-type pullets. The cross-over effect of feeding strategy during rearing on laying performance and egg shell quality was studied from 19 to 32 wk of age. From 0 to 16 wk, ADG, ADFI, and feed conversion ratio (FCR) were improved with CWS and COH compared to MWS, but ADG and FCR were improved with MWS compared to CWS and COH from 11 to 16 wk. Uniformity of BW till 11 wk, and tibia breaking strength at 6 and 16 wk were higher with CWS and COH compared to MWS. Tibia ash content at 11 wk and relative empty proventriculus + gizzard weight (EPG) were lower with CWS and COH compared to MWS, also relative EPG at 11 and 16 wk was higher with COH compared to CWS. At 25 wk BW was lower with MWS compared to CWS and COH, but BW was equal for all treatments at 32 wk. The FCR for egg production was improved with COH compared to MWS. Egg shell parameters were not affected by feed form during rearing. Low Ca-P decreased BW uniformity at 6 wk, relative keel bone weight and ash content at 11 wk, tibia ash content at 11 and 16 wk, increased relative EPG at 6 wk, and improved egg shell quality at 32 wk of age. It was concluded that feeding CWS and COH compared to MWS increased growth performance, but had no clear cross-over effect on egg production. Low dietary Ca-P led to a lower bone mineralization during rearing, nevertheless improved egg shell quality at 32 wk.

The effects of coarse and wet feeding on performance parameters, gastrointestinal tract and tibia traits, and digesta phytase activity in egg-type pullets, either fed a low or moderate phosphorus diet

In a 2 × 2 × 2 factorial design, the effects of dietary non-phytate phosphorus (NPP) levels, 0.17% (low) and 0.33% (moderate), diet moisture (dry and wet), and diet particle size (coarse and fine), were studied on egg production, characteristics of gastrointestinal tract (GIT) and tibia, digesta pH, and phytase activity in layer pullets (16 to 28 wk of age). The low NPP diet increased average daily water intake (ADWI) to ADFI ratio (4.2%) from 16 to 17 wk, but decreased this ratio (2.8%) from 23 to 27 wk. It decreased ADFI (1.5%) and egg mass production (3.8%) from 19 to 22 wk. It decreased egg weight (0.29 g) and ADWI (2.1%) from 23 to 27 wk. At 22 wk, the GIT relative empty organ weights were (g/kg BW) higher for proventriculus + gizzard (0.96), duodeneum (0.94), and jejunum + ileum (1.95) with the low vs. moderate NPP diet. The low NPP diet decreased digesta phytase activity in crop and proventriculus+gizzard at 28 wk. The wet diet increased ADFI, ADWI, and ADWI/ADFI ratio from 16 to 27 wk, egg mass production (3.0%) from 19 to 22 wk, and egg weight (0.45 g) from 23 to 27 wk. The wet diet also increased digesta phytase activity in proventriculus+gizzard. The coarse diet decreased ADFI from 19 to 22 wk (1.7%) and 23 to 27 wk (1.2%). The coarse diet caused reduced egg mass production (2.6%) from 23 to 27 wk. Egg shell breaking strength was increased on the coarse diet (0.9 Newton). The coarse diet increased ADWI/ADFI ratio from 16 to 27 wk, and increased relative gizzard weight by 1.95 and 0.81 g/kg BW at 22 and 28 wk, respectively. The coarse diet increased jejunal/ileal pH with 0.16 units at 28 wk. None of the tested parameters affected tibia characteristics. It was concluded that a low NPP diet did not clearly affect the studied parameters. The wet diet increased ADFI, ADWI, and egg production. The coarse diet increased ADWI, egg shell breaking strength, relative gizzard weight, and reduced ADFI and egg production.

Effect of low protein diets supplemented with free amino acids on growth performance, slaughter yield, litter quality, and footpad lesions of male broilers

A study with 884 Ross 308 male broilers, housed in 68 floor pens (0.75 m²) from 0 to 35 days of age was conducted to evaluate the effects of low crude protein (CP) diets, with partial replacement of soybean meal by free amino acids (AA), on performance, slaughter yields, litter quality and footpad lesions. During the first 11 d, all broilers received the same control starter diet (216 g/kg CP, 11.5 g/kg apparent fecal digestible (AFD) lysine, and 2900 kcal/kg AMEn). Thereafter, four experimental feeding programs with different levels of dietary CP (control and control with 1% (CP-1%), 2% (CP-2%) and 3% (CP-3%) less CP units) were provided in both the grower and finisher phase. In the control grower and finisher diet, the CP content was 208 and 198 g/kg, respectively. All diets were formulated to meet or exceed the recommendations concerning AFD AA, and to be iso-caloric within each feeding phase. Feed and water were provided for ad libitum intake during the entire experimental period.

None of the low CP feeding programs affected body weight gain, feed intake or mortality from 0 to 35 d. However, CP conversion was improved with the reduction of CP content of the diet. Broilers fed the CP-2% or CP-3% feeding program had an improved feed conversion ratio. Broilers fed the low CP protein feeding programs had a better litter quality and less footpad lesions, compared to broilers fed the control feeding program. Broilers fed the CP-3% feeding program had a lower breast meat yield than broilers fed the control feeding program. Slaughter yields of broilers fed CP-1% or CP-2% feeding program did not differ from the control feeding program. This study demonstrated that the CP content of grower and finisher diets can be reduced by 2.2–2.3% units without adverse effects on growth performance of broilers, while CP reduction seems promising to reduce nitrogen excretion from broiler houses, improve bird welfare, and reduces dependence on vegetable protein sources.