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Well-managed irrigated pasture production can be optimized without nitrogen (N) fertilizer. The objective was to determine mixture and planting ratios of tall fescue (Schedonorus arundinacea Schreb.) (TF), meadow brome (Bromus riparius Rehm.) (MB), orchardgrass (Dactylis glomerata L.) (OG), timothy (Phleum pratense L.) (TIM), and perennial ryegrass (Lolium perenne L.) (PRG) with alfalfa (Medicago sativa L.) (ALF), birdsfoot trefoil (Lotus corniculatus L.) (BFTF), or cicer milkvetch (Astragalus cicer L.) (CMV) that maximize productivity. Planting ratios were 0:100 (grass:legume), 25:75, 50:50, 75:25, and three 100:0 grass monocultures fertilized at 0, 67, and 134 kg N ha-1. Seasonal production of TF-ALF was 12.69 Mg ha-1, equal to TF fertilized at 134 kg N ha-1. ALF mixtures with MB, OG, TIM, and PRG produced 12.57, 10.97, 11.77, and 10.74 Mg ha-1, respectively, and 8 to 40% more than grasses receiving 134 kg N ha-1. Production of BFTF mixtures with TF, MB, and OG were 11.69, 11.45, and 9.95 Mg ha-1, respectively, equal to their respective grass monoculture receiving 134 kg N ha-1. The BFTF-TIM and BFTF-PRG mixtures averaged 12% more forage than grass monocultures receiving 134 kg N ha-1. Production of CMV-grass was similar to that of grasses receiving 67 kg N ha-1. Seasonal forage distribution was more uniform in ALF- and BFTF-grass mixtures, averaging 30% more at the second and third harvests than fertilized grasses. The TF and MB legume mixtures averaged 7% more production in the 50:50 planting ratios than the other two grass-legume mixtures, while the 50:50 and 25:75 ratios of OG and TIM-legume mixtures averaged 12% more than the 75:25 and the 25:75 PRG-legume planting ratio averaged 9% more than the 50:50 and 75:25. Forage production of grass-legume mixtures can equal or exceed fertilized grass monocultures and with more uniform distribution over the growing season. [ABSTRACT FROM AUTHOR]

Insufficient dry matter intake (DMI) of pasture by dairy cattle is a major factor limiting growth and milk production; however, it has been hypothesized that some dairy breeds may be more efficient grazers than others. This study was conducted to determine whether dairy breed types differ in DMI and feed efficiency when grazing either grass monoculture or grass-legume mixed pastures. The experiment compared 4 different dairy breed types (Jersey, Holstein, Holstein-Jersey crossbreds, and Montbéliarde-Swedish Red-Holstein 3-breed crossbreds) and 2 levels of pasture type [grass monoculture (MONO) and grass-birdsfoot trefoil (BFT) mixture (MX)] for a total of 8 treatments. Pastures were rotationally stocked with groups of 4 prepubertal heifers for 105 d for 3 yr, and DMI was determined from herbage disappearance. Feed conversion efficiency (FCE) and residual feed intake (RFI) were then derived from DMI, and heifer body weights (BW) and normalized to animal units (AU) as 40% metabolic mature BW of the corresponding dairy breed type to account for inherent differences in size and growth rates. We observed differences in DMI and feed efficiency among breed types and between pasture types. On average, Holsteins had the greatest overall DMI (4.4 kg/AU), followed by intermediate DMI by the crossbreds (4.0 kg/AU), and Jerseys had the least DMI (3.6 kg/AU). Heifers grazing MX pastures had on average 22% greater DMI than those grazing MONO, but heifers on grass monocultures were more efficient in converting DMI to BW gain (i.e., RFI/AU of 0.27 and −0.27, respectively; more negative RFI numbers indicate less DMI to achieve the expected gains). Overall, Jerseys had the most favorable feed efficiency; however, ranking of Holsteins and crossbreds depended upon the feed efficiency metric. This study is one of the first to compare the interaction of dairy breed and pasture quality on grazing efficiency. However, the lack of a breed type × pasture type interaction for DMI, FCE, or RFI indicated that none of these dairy breed types were better adapted than another breed type to pastures with contrasting levels of nutritive value. [ABSTRACT FROM AUTHOR]