title: Effects of feeding strategy on milk production, reproduction, pasture utilization, and economics of autumn-calving dairy cows in eastern North Carolina.
abstract: A balance among stocking rate (SR), pasture management, and supplementary feeding is required to optimize overall farm performance and profitability in pasture-based dairying. Beginning in September 2003, a seasonal, autumn-calving, pasture-based farming system was established to address the effects of feeding strategy (FS; i.e., a unique combination of stocking and supplementation rate) on productive, reproductive, and economic performance of lactating herds over 3 yr. Eighty lactating cows (1/3 Holsteins, 1/3 Jerseys, and 1/3 crosses of those breeds) were randomly assigned to either a lesser stocking, lesser supplementation group [LSR; 2.2 cows/ha, 6.3 kg of dry matter (DM) of a corn-based concentrate consumed daily, n=40] or a greater stocking, greater supplementation group (HSR; 3.3 cows/ha, 9.2 kg of DM of a corn-based concentrate consumed daily, n=40). Pasture/forage crop rotations included annual ryegrass and sorghum-Sudan (50%), annual ryegrass and bermudagrass (20%), and a tall fescue-white clover pasture (30%). Pre- and postgrazing herbage mass values and grazing intervals (3,347±255.8 kg of DM/ha, 1,861±160.6 kg of DM/ha, 23.6±1.9 d) did not differ between FS. The nutritive value of fresh and conserved forages was similar between feeding strategies, except for acid detergent fiber in freshly grazed bermudagrass (29.6 vs. 26.3% of DM for LSR and HSR, respectively). Cows on HSR tended to spend more time on an adjacent feeding area where conserved forages were offered (85 vs. 61 d/yr) as opposed to grazing paddocks (204 vs. 228 d/yr). Lactation performance was greater for HSR; cows on HSR produced 10.8% more milk fat and 6.3% more milk protein than cows on LSR. Holstein cows produced the greatest amounts of mature-equivalent milk, but did not differ from crossbred cows in terms of energy-corrected milk, and mature-equivalent fat and protein yields. Reproductive efficiency did not differ among feeding strategy, but breed differences were observed; conception rates at first and all services, as well as pregnancy rates, were greater for Jersey and crossbred cows compared with Holsteins. The greater stocking rate required additional supplemental concentrate and time away from grazing paddocks, but reproductive efficiency was similar and overall lactation performance was greater. The greater stocking rate resulted in increased productivity and greater income over feed costs per unit of land.
authors.affiliation: AgResearch Limited, Grasslands Research Centre, Palmerston North 4442, New Zealand.
authors.forename: R E
authors.initials: RE
authors.lastname: Vibart
authors.forename: S P
authors.initials: SP
authors.lastname: Washburn
authors.forename: J T
authors.initials: JT
authors.lastname: Green
authors.forename: G A
authors.initials: GA
authors.lastname: Benson
authors.forename: C M
authors.initials: CM
authors.lastname: Williams
authors.forename: D
authors.initials: D
authors.lastname: Pacheco
authors.forename: N
authors.initials: N
authors.lastname: Lopez-Villalobos
mesh_terms: D000821:Animal Feed / Q000191:economics; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000191:economics / Q000379:methods*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000378:metabolism; D009657:North Carolina; D012098:Reproduction / Q000502:physiology*; D012621:Seasons