Pasture productivity, cattle productivity and metabolic status following fertilization of a grassland with liquid hog manure: A three-year study

Abstract

Forage yield and quality, cattle and pasture productivity, and enteric methane (CH4) emissions were determined from grass pastures receiving liquid hog manure. Three treatments were evaluated: grass pastures receiving no manure (Control), grass pastures receiving liquid hog manure applied as a single application of 142 ± 20 kg available N ha-1 in the spring (Single) or a split application of 70 ± 6 kg available N ha-1 in both the spring and autumn (Split). Each treatment was represented by two paddocks. The study was carried out over three grazing seasons, from 2004 to 2006, with each grazing season divided into three, 28-d periods. Growing steers (338 ± 32 kg) were introduced into pastures in early summer (May-June) of each year. Standing biomass, measured using quadrats, averaged 1.2, 2.6, and 2.0 ± 0.44 t dry matter (DM) ha-1 for Control, Split and Single pastures, respectively, and was not influenced (P = 0.13) by liquid hog manure application. Liquid hog manure application caused a shift in pasture grasses resulting in a predominance of quackgrass [Elytrigia repens (L.) Nevski]. Nutrient profiles of forage samples collected by hand plucking showed no treatment response for forage gross energy (GE; P = 0.18) and neutral detergent fibre (NDF; P = 0.19), but forage crude protein (CP) (P = 0.027) as well as ash (P = 0.002), K (P = 0.001), P (P = 0.001), and Mg (P = 0.001) concentrations increased with manure application. Liquid hog manure application did not influence dry matter intake (DMI) (P = 0.56), GE intake (P = 0.58), and NDF intake (P = 0.79) of grass forages. Higher CP intake of steers on Split and Single pastures resulted in higher (P = 0.001) serum urea N (5.7 and 5.9 ± 0.42 mmol L-1, respectively) compared with steers grazing Control pastures, 2.5 ± 0.42 mmol L-1. Enteric CH4 emissions (L d-1) tended to be lower (P = 0.09) in cattle grazing the Split pasture treatment. Though application of liquid hog manure did not improve individual animal gains, pasture carrying capacity increased (P = 0.001) from 89 to 324 grazing days ha-1 and liveweight gain increased (P = 0.001) from 100 to 329 kg ha-1 in Control and manured pastures, respectively. Application of liquid hog manure to grasslands generated significant benefits through improved forage quality and pasture productivity measured as carrying capacity and liveweight gain. Split liquid hog manure application may have a further benefit in terms of improved carrying capacity and lower enteric CH4 emissions. Key words: Liquid hog manure, enteric methane, beef cattle, carrying capacity, serum urea nitrogen