Effects of Laying-Hen Strain on Manure Properties and Ammonia Emission

Ammonia (NH3) emissions from laying hens are affected by nutrient content of the diet, manure quantity, and manure properties such as moisture content, nitrogen content, and pH. These production traits may vary with strain of the hen. However, limited information is available concerning the effects of laying-hen genetics on manure properties and NH3 emission. This study was conducted to comparatively quantify production performance, manure properties, and NH3 emissions (through N mass balance) of four white-egg-laying strains (Hy-Line W-36, Hy-Line W-98, Lohmann LSL Lite, and Bovans White) and four brown-egg-laying strains (Hy-Line Brown, Lohmann Brown, ISA Brown, and Bovans Brown) during two production periods of 27-28 weeks (P1) and 35-36 weeks (P2) of age. The diets were formulated to meet the nutritional needs of the brown and white hens. As a result, crude protein contents during P1 and P2 were, respectively, 13.2% and 15.2% for the brown hens but 14.5% and 17.4% for the white hens. The results showed that the brown and white hens had similar hen-day egg production (97.5% to 89.2% for brown hens and 96.0% to 88.2% for white hens) and egg mass output (57.1 to 52.6 g d-1 hen-1 for brown hens and 55.6 to 51.2 g d-1 hen-1 for white hens) but different feed consumption (112 to 98 g d-1 hen-1 for brown hens and 101 to 93 g d-1 hen-1 for white hens, p < 0.01) and feed efficiency (1.97 to 1.87 g feed g-1 egg for brown hens and 1.82 g feed g-1 egg for white hens, p < 0.0001 and p = 0.11). The higher feed consumption for the brown hens stemmed from their heavier body mass (1.81 to 1.78 kg vs. 1.56 to 1.53 kg for white hens). Manure moisture content was higher for the brown hens than for the white hens, although the dry-matter manure production was not significantly different. The results further revealed that under the experimental conditions (i.e., higher CP contents of the diet for the white hens than for the brown hens) the white hens had higher NH3 emissions than the brown hens as expressed per hen (37% to 19% higher, p = <0.001 to 0.016), per animal unit (AU, 500 kg live body mass; 59% to 39% higher, p = 0.0007 to 0.007), per unit of egg mass output (41% to 24% higher, p = 0.01 to 0.09), per unit of feed N consumed (39% to 27% higher, p = 0.01 to <0.0001), and per unit of dry manure (56% to 39% higher, p = 0.001 to 0.007). Certain differences existed in production performance among strains within the brown or white hens, but no differences in NH3 emissions were detected. Because of the relatively small sample size (number of hens involved) and the relatively short monitoring period, the results should be referenced with these limitations in mind. Further larger-scale studies with longer monitoring periods to verify these findings are warranted.