Dietary protein levels during the pullet phase (8–18 week) influence the mortality during laying stage

Integrated Assessment of Productive, Environmental, and Social Performances of Adopting Low-Protein Diets Technology for Laying Hens

China, the world's largest egg producer, faces challenges of protein feed shortages and nitrogen pollution from manure. Low-protein diets (LPDs) offer potential solutions, but their adoption by small-scale farmers is uncertain. This study used surveys, meta-analysis, life-cycle assessment, and life-cost analysis to address these gaps. A field survey in Quzhou County (a typical representative of small- and medium-scale farmers in China's egg farming industry) found that 84% of egg farmers were unfamiliar with LPDs and believed higher protein levels were better. On average, pre-laying and late-laying diets exceeded national LPD recommendations by 0.3% and 0.5% crude protein (CP), respectively. The main barriers to LPD adoption were perceived low quality, lack of veterinary recommendations, and limited technical support. A meta-analysis of 30 studies (published before July 2024) showed that reducing CP by less than 1% did not compromise productivity. Local LPD demonstrations and training improved farmer confidence. Results indicated a 10% reduction in the nitrogen footprint and a 115% increase in earnings for LPD-demonstration farmers. The study suggests a coupled pathway integrating research and technology diffusion, highlighting the need for collaboration among scientists, feed companies, and technical experts to overcome misconceptions and promote LPD adoption. This integrated framework offers valuable insights for sustainable agricultural development in China and other resource-limited countries.

The effect of diet density on allometry in pullet growth and early egg production

Understanding the effect of nutrition on pullet growth curves and body composition may help to design new feeding strategies that influence body composition and (long-term) laying performance. Therefore, this study examined the effect of nutrient density (low, medium or high metabolizable energy and essential amino acids), fed in the rearing phase until 17 wk of age, on Hy-Line white W80 pullet growth, body composition development and egg production performance until wk 35. Data were subjected to mixed model analyses. To determine a multiphasic allometric relationship between body components, an overall growth curve was established and inflection points were determined. The linear higher BW at the end of the rearing phase, due to increased diet density, was maintained during the peak production phase until wk 35. Egg production parameters were not affected by rearing diet density. Breast and body crude protein percentages were not influenced by dietary treatments, whereas body crude fat and abdominal fat pad percentages were linearly increased with diet density from early age onward. Body crude protein was initially deposited at the same rate as body dry matter. In a second phase of growth from wk 12 onward, crude protein deposition was lower than body dry matter deposition, but was not influenced by rearing diet. Body crude fat, on the other hand, initially grew at a lower rate than body dry matter, but increased in deposition rate during a second phase of growth starting at wk 2 to 5. Pullets fed the high density diet showed higher deposition of crude fat vs. dry matter as compared to pullets fed the medium density diets in the first phase until wk 2, but exhibited lower crude fat deposition in the second phase until wk 8. These results indicate that until approximately wk 12, crude protein deposition was mainly driving growth and was not influenced by diet density. From wk 5 to 6 onward, crude fat deposition relative to protein deposition increased and this was influenced by diet density from an early age.

Dietary protein levels during 12 to 26 wk improve the growth performance, bone quality, and testosterone in Pearl Gray male guinea fowl (Numida meleagris)

Guinea fowl (Numida meleagris), although native to Africa and despite its many potentials, does not represent the dominant species on the continent because of its seasonal reproductive nature and high keets mortality. This study was conducted to assess the effect of crude protein levels on growth performance, bone characteristics and reproductive activity of Pearl Gray male breeder guinea fowl from 12 to 26 wk of age. A total of 120 twelve-wk-old guinea fowls were randomly allotted to 3 dietary treatments with 8 replicates each and 5 birds per replicate using a completely randomized design. The dietary treatments comprised low level (LL), normal level (NL), and high level (HL) with diets respectively containing 15, 17, and 19% crude protein (CP). The results showed that guinea fowl in the HL treatment had a significantly lower feed conversion ratio (P = 0.008) than those in the other treatments. The birds fed the HL diet had significantly higher concentrations of testosterone (P < 0.05) than in the other treatments. High levels of calcium and phosphorus were observed in the femur of the HL group relative to the LL group. The birds in the LL treatment had a significantly higher (P = 0.007) femur robusticity index than those in the HL treatment. In conclusion, feeding 19% crude protein to Pearl Gray male guinea fowl from 12 to 26 wk of age improves growth performance, the density and strength of the femur and tibia and the reproductive tract. The CP level for the best performance of male guinea fowl from 12 to 26 wk of age is 19%.

Effects of dietary protein levels on performance, nitrogen excretion, and odor emission of growing pullets and laying hens

The objective of this study was to determine the effects of dietary crude protein (CP) levels on production performance, nitrogen balance, and odor emission of excreta in growing pullets and laying hens from 13 to 32 wk of age. Two hundred and forty pullets (Hy-Line Brown) were randomly assigned to 1 of 4 dietary groups with 10 replicates per group, and 6 birds per replicate. Experimental diets were formulated to contain 4 graded CP levels in the diets of pullets ranging from 180, 160, 140, and 120 g/kg of diet during 13 to 18 wk (phase 1) and in the diets of laying hens from 190, 170, 150, and 130 g/kg of diet during 19 to 32 wk (phase 2). The limiting amino acids including lysine, methionine, and threonine were supplemented to maintain constant equal amino acid concentrations in all experiment diets. In phase 1, decreasing dietary CP levels did not affect growth performance but increased (linear and quadratic effect, P < 0.05) the relative abdominal fat contents and triglyceride concentration in serum samples. High-density lipoprotein cholesterol in serum samples decreased as the CP levels decreased in the diets of pullets. Dietary CP levels quadratically increased (P < 0.05) the villus height and the villus height to crypt depth ratio but did not affect tibia traits and relative organ weights in pullets at 18 wk. Apparent digestibility of dry matter and ether extract increased with decreasing dietary CP levels in pullets. Graded CP levels linearly increased the digestibility of dry matter, CP, and ether extracts but lowered that of crude ash in laying hens. Nitrogen excretion was linearly decreased (P < 0.05) as the dietary CP levels decreased in both pullets and laying hens. Dietary CP levels only affected carbon dioxide emission in pullets. In phase 2, dietary CP levels did not affect growth performance and the ages at first egg laying and to reach 50% egg production in laying hens. However, egg weights were decreased (linear and quadratic effect, P < 0.05) as the dietary CP level decreased in laying hens. Increasing dietary CP levels increased Haugh unit at 26 wk but lowered corticosterone concentrations in yolk samples at 22 wk. Collectively, this study shows that dietary CP levels could be decreased to reduce nitrogen excretion without adverse effects on performance and egg quality of growing pullets and laying hens.