been released through public and private breeding programs. Differences among annual ryegrass (Lolium multiflorum Lam.)To date, most studies on annual ryegrass have focused cultivars for weight gain of grazing steers have been reported, even on critical establishment factors, such as sod-suppresthough plot experiments suggest that forage dry matter yield among sion and tillage (Cuomo and Blouin, 1997; Cuomo et cultivars should not be a limiting factor. Likewise, forage nutritive value differences among cultivars have not been assessed. The objec- al., 1999; Lang, 1989). There have been few studies contives of this research were to evaluate differences in cumulative forage ducted to determine animal performance (Hafley, 1996; yield, yield distribution, and nutritive value among 'Gulf', 'Jackson', Hoveland et al., 1991) and these have evaluated a mini-'Marshall', 'Rio', 'Rustmaster', and 'Surrey' annual ryegrass. Plots mal number of cultivars due to the expense of conductwere harvested six times beginning in December at approximate 30-d ing these studies. Recent reports indicate annual ryeintervals during the 1997-1998 and 1998-1999 growing seasons. Nutrigrass cultivar differences for gains by growing cattle tive value measurements included crude protein (CP), neutral deter-(Bransby et al., 1997; Wyatt and Granger, 2001). The gent fiber (NDF), in vitro true digestibility (IVTD), and digestible increased animal gain on Marshall versus Gulf pasture NDF (DNDF). There were no differences among cultivars for cumulahas ranged from 77 to 27% in Alabama (Bransby et al., tive forage yield (P ϭ 0.99). However, for the January harvest, Surrey 1997) and 16% to essentially no difference over 3 yr in and Gulf averaged 1030 (Ϯ65) kg DM ha Ϫ1 , whereas Marshall yielded only 672 (Ϯ79) kg DM ha Ϫ1 . For the March harvest, yields of all Louisiana (Wyatt and Granger, 2001). Gains were simivarieties were similar and averaged 1350 (Ϯ95) kg DM ha Ϫ1 .A tt h e lar for cattle grazing Marshall and Jackson (Wyatt and May harvest, Marshall and Jackson yielded 1232 (Ϯ123) kg DM ha Ϫ1 , Granger, 2001) and for cattle grazing Marshall and Surwhereas Gulf yielded only 929 (Ϯ74) kg DM ha Ϫ1 . Crude protein rey (Hafley, 1996). Animal performance advantages apconcentration differed significantly among harvests with a general pear to be associated with forage mass as suggested decrease from 260 to 120 g CP kg Ϫ1 as the growing season progressed. by plant height differences (Bransby et al., 1997) and Similar declines in nutritive value occurred for NDF, IVTD, and measurements using a rising plate meter (Wyatt and DNDF. Trends in yield distribution and forage quality may indicate Granger, 2001). Possible contributions of nutritive value a need for cultivar specific recommendations based on intended forage differences among annual ryegrass cultivars to differneed and season of use.
Infection by an endophyte [Neotyphodium coenophialum (Morgan‐Jones & Gams.) Glenn, Bacon, & Hanlin comb. nov.] can improve persistence of tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire = Festuca arundinacea Schreb.). Novel endophytes may minimize toxicity problems associated with wild‐type endophytes, thus encouraging tall fescue use in the south central USA. The objectives of these studies were to compare stand persistence and grazing animal performance among tall fescue cultivars with different fungal endophyte combinations in the south central USA. Trials were planted in 1999 in Oklahoma and Louisiana. Tall fescue entries contained no endophyte (‘GA‐5’ E−, ‘Dovey’), a novel endophyte (‘Jesup’ MaxQ, ‘GA‐5’ MaxQ), or a wild‐type endophyte (‘KY‐31’ E+, ‘GA‐5’ E+). Weight gain data for beef cattle (Bos taurus) were collected during fall and/or spring. Estimates of stand persistence were collected periodically. In Oklahoma, average daily gain (ADG), at 0.71 kg d−1, did not differ between entries in fall. During spring, ADGs (kg d−1) were greater from Dovey (0.64), GA‐5 MaxQ (0.67), and GA‐5 E− (0.56) than from KY‐31E+ (0.29) and were intermediate for GA‐5E+ (0.47). In Louisiana, ADGs were greater from GA‐5 E− (1.20), GA‐5 MaxQ (1.06), and Jesup MaxQ (1.12) than from GA‐5E+ (0.76). In Oklahoma, stands were greater than 80% 4 yr after establishment. In Louisiana, stands declined in some E− paddocks 3 yr after planting. Thus, E− and novel endophyte–infected tall fescue resulted in greatest animal performance, whereas wild‐type and novel endophyte infection led to enhanced stand longevity. However, improved persistence is needed for broader adaptation of tall fescue to the south central USA.
A field study was conducted from 1991 through 1997 to evaluate the use of pyrethroid and organophosphate (OP) ear tags, alternated yearly, for the control of a pyrethroid resistant horn fly, Haematobia irritans (L.), population in Louisiana. Fly resistance was monitored by weekly fly counts, filter paper bioassays and diagnostic polymerase chain reaction (PCR) assays for the presence of pyrethroid resistance-associated mutations in the sodium channel gene coding region. Fly control in the first study year was poor, as pyrethroid ear tags were effective for only 7 wk. The following year, OP ear tags provided 15 wk of fly control. However, in all subsequent years, fly control was poor with both types of ear tags. The PCR assays showed that there were very few female flies homozygous for the pyrethroid susceptible sodium channel allele, never rising above 10% of the total females in the population. A fitness cost appeared to be associated with the pyrethroid resistant allele, as the resistant form was selected against in the absence of the pyrethroid ear tags. Despite this selection in favor of the susceptible allele and the annual alternation of pyrethroid and OP ear tags, the percentage of homozygous susceptible flies never reached over 19% of the population, resistant alleles of the sodium channel remained at high levels in the population, and horn fly control on cattle with either type of tag quickly became minimal.
is considered the primary weakness of white clover branched and rooted, particularly during the summer. White clover (Gibson and Cope, 1985), and producers often cite perecotypes represent a valuable source of germplasm to incorporate into breeding programs or to develop directly into more persistent culsistence as more important than productivity when tivars.contemplating establishment of a forage crop (D.M. Ball, 1998, personal communication). A detailed evaluation of white clover ecotypes found in Southeastern pastures and comparison with commer-
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