Developing a tall fescue for reduced grass tetany risk

Tall fescue (Festuca arundinacea Schreb.) is an important forage grass, and like other C3 grasses, has the potential to cause grass tetany in grazing ruminants. Genetic variation in cation uptake by fescue was exploited by selecting for high Mg and Ca relative to K concentration in fescue. The grass tetany ratio. K/(Ca+Mg), was reduced about 18% after 2 selection cycles. The mean Mg and K(Ca+Mg) values for 20 C1 plants, grown at pH 6.4, were-weakly related (r2=0.42 and 0.48) to those of plants grown in calcareous sail pH 82. The P, Na, Mn, Fe, Cu, and Zn concentrations were not affected by the selection process

Genetic variation for selenium content in tall fescue

Selenium is an element necessary for good animal health. No information is available on inheritance of Se concentration in tall fescue (Festuca arundinacea Shreb.). Therefore, the purpose of this investigation was to determine the nature of genetic variation of Se concentration in tall fescue. To accomplish this objective, 15 parental clones were randomly chosen from a broad-based population, and their half-sib (HS) progenies were generated using a polycross mating design. Selenium analysis was determined flourometrically by digesting dried, ground herbage samples in 3:1 HNO3/HCIO4 . Significant genetic variation was observed among HS families in the fall for Se concentration. Heritability, calculated using parent-offspring (PO) regression, gave estimates of 18% for summer and 68% for the fall. Heritability and genetic gain estimates were maximized in the fall, as compared with the summer, largely because of a large environmental component. Genetic gain, expressed as a percentage of the mean of parents, predicted an advance of 1 9 % for fall herbage. Progress in selecting for improved concentrations of Se in the fall in this population of tall fescue is likely

Using plant breeding and genetics to overcome the incidence of grass tetany

Plant breeders developing cultivars to minimize the hazards of grass tetany are concentrating largely on increasing herbage Mg concentrations in cool-season (C3) grasses. Significant genetic variation has been found for Mg, Ca and K concentrations within C3 grass species studied to date. For most C3 forage grass species, heritability estimates are highest for Mg, slightly lower for Ca and lowest for K concentrations. The largest genotype x environmental interactions are found for K values, whereas small environmental effects have been observed for Mg and Ca values. No C3 forage grass cultivar has been developed to date that would eliminate hypomagnesemia. Grass breeders need to develop more experimental C3 plant populations that have high Mg and Ca concentrations. These experimental synthetics with genetically altered mineral concentrations need to be fed to ruminants susceptible to grass tetany to determine whether grass tetany can be eliminated or reduced. Limited feeding trials using ruminants show that improved animal performance can be expected when feeding forage grasses bred for higher Mg concentrations

Use of an experimental high-magnesium tall fescue to reduce grass tetany in cattle

Grass tetany (hypomagnesemia) continues to be a problem for the livestock industry. An experimental cultivar of tall fescue (Festuca arundinacea Shreb.) selected for high Mg concentration, HiMag, was compared against four other cultivars for its ability to increase serum-Mg and reduce the risk of grass tetany. Forage from HiMag contained 22% more Mg, 183% more Ca, and 9% more P than other cultivars; K levels were not different. Regardless of cultivar, concentrations of Ca and Mg were lower while K and P were higher during the spring than the autumn. The tetany ratio IK/(Ca + Mg) on basis] was lower for HiMag than for other cultivars (1.34 vs. 1.65); all cultivars had a higher ratio during spring than autumn (1.91 vs. 1.31). In cattle (Bos taurus) grazing trials, blood serum from steers grazing HiMag contained 8% more Mg in autumn 1993 but was not different in spring 1994. Blood serum Mg was not different for cows (either dry or nursing calves) during autumn grazing, but approached significance (P = 0.09) during the spring 1995 calving season (2.32 vs. 2.07 mg/dL for HiMag vs. other cultivars). Except for differences between calves on HiMag compared with Kentucky-31 in autumn 1995 (58 vs. 43 lb, respectively), animal weight change was not affected by cultivar. Normal forage Mg concentrations (>0.20%) and tetany ratios below 2.2 for all cultivars in every season except spring 1995 may explain the lack of consistent animal response. No clinical symptoms of grass tetany were observed at any time during these studies. However, the higher Mg concentration and lower tetany ratio suggest that HiMag could provide a means of reducing the incidence of grass tetany in livestock during periods when risk of the disorder is high

Registration of HiMag Tall Fescue Germplasm

HiMag (Reg. no. GP-79, PI 615587) tall fescue (Festuca arundinacea Schreb.) was developed and released by the Missouri Agricultural Experiment Station and the USDA-ARS in 1997. HiMag has relatively high Mg and Ca concentrations and low tetany ratio [K/(Ca + Mg)] expressed as moles of charge. Parental germplasm for the Co cycle of selection for HiMag included 950 plants from 'Kenhy' (Buckner et al., 1977), 831 plants from 'Kentucky-31', and 688 plants from `Missouri-96' (Asay et al., 1979). All plants were endophyte free [ Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin comb. nov.]. Parental plants were transplanted to the field near Columbia, MO, in the fall of 1983. The soil was a Mexico silt loam (a fine, montmorillonitic, mesic Udollic Ochraqualf) with a pH of 6.4. Selection was applied against crown rust (caused by Puccinia coronata Corda. var. coronata), leaving 1011 plants which were harvested in the fall of 1984 and analyzed for elemental concentrations of Mg, Ca, K, and the tetany ratio. Sixty-five plants (11 from Kentucky- 31, 54 from Missouri-96, and 0 from Kenhy) were chosen to generate the C1 cycle of selection. These 65 plants contained 5.0 to 7.0 g kg-1 Mg, 5.0 to 10.2 g kg' Ca, 20 to 33 g K, and had K/(Ca + Mg) values of 0.61 to 0.99. These were allowed to open-pollinate in the greenhouse during the winter of 1985/86. Harvested seeds were germinated in the greenhouse and seedlings were transplanted to the field in the fall of 1986. During the fall of 1987 approximately 1000 plants were analyzed from the CI cycle to determine elemental concentrations of Mg, Ca, K, and the tetany ratio. Forty-six plants chosen for the C2 contained 4.4 to 6.1 g kg -' Mg, 5.5 to 8.1 g kg-' Ca, 17.2 to 30.9 g kg' K, and had tetany ratios of 1.06 to 2.13. These were allowed to open-pollinate in the greenhouse in the winter of 1988-1989. Approximately 1000 seedlings were transplanted to the field having areas of Creldon silt loam (Mollic Fragiudalf) and Hobert silt loam (Umbric Fragiaqualf) at the Southwest Research Center, located near Mt. Vernon, MO, in the fall of 1989. In the summer of 1990, seed was harvested from these spaced plants and planted into an irrigated Portneuf silt loam soil (Durinodic Xeric Haplocalcid) to establish a seed increase block at Kimberly, ID, in April 1991. In 1992, seed from HiMag was harvested with the following characteristics: 1635 kg ha-1, 400 seeds g-1, 2.5 g 1000 seeds-1, and 302 kg m-3

Daily carbohydrate accumulation in eight tall fescue cultivars

Eight cultivars of tall fescue (Loliumarundinaceum Schreb., S.J. Darbyshire = Festuca arundinacea Schreb.), Barcel, Kenhy, Kentucky-31, Missouri-96, Mozark, Stargrazer, C-1 (an experimental selection), and HiMag, were sampled at 2-h intervals during daylight on four cutting dates. Cultivars varied in concentrations of carbohydrate fractions but accumulation rates were not different. Daily mean total non-structural carbohydrate (TNC) concentrations for cutting dates in May, July, August and September declined from 239 to 231, 143 and 120 g TNC kg?1 adjusted dry weight (ADW) respectively. Concentrations of fructans were highest in July but sucrose, glucose and starch concentrations were highest in May. Sucrose was the largest contributor proportionately to TNC daily means across accessions in May (0·33), August (0·30) and September (0·38). Glucose composed an equivalent proportion of TNC in the August harvest. Starch concentration was highest in May at 53 g kg?1 ADW and lowest in August at 23 g kg?1 ADW. The TNC concentration increased by 22·4 (May), 16·8 (July), 21·0 (August) and 30·8 g kg?1 ADW (September) from dawn to dusk. Forage samples taken to estimate preference by ruminants or for TNC analyses should be cut and preserved within 1 h to control the diurnal variation of TNC proportionately within 0·05. Tall fescue should generally be cut between noon and sunset for TNC concentrations to be greater than the daily mean

Use of a Prepaid Cellulase Solution for Screening Forage Grass Germplasm for Digestibility

A reliable rapid and inexpensive laboratory procedure is needed to screen native African forage grass species for forage quality. This study determined the potential of using a prepared cellulase solution to assess in vitro dry matter solubility of 22 native Kenyan forage grasses and 18 native warm season grasses from Missouri, USA. A prepared cellulase solution was used for screening the grass species for digestibility using two procedures. One procedure involved digesting grass samples in prepared cellulose solution without any pre-treatment (CSD), and the other procedure used an acid pepsin pretreatment prior to digestion in the prepared cellulose solution (APCS). The CSD procedures in comparison to APCS generally underestimated in vitro dry matter solubility by a rand of up to 23%. The variations were highly species dependent. Although the APCS procedure more time consuming, it made it possible to identify a group of species resolvable into high (42.6-61.4%), medium (36-40%) and low (29-34%) digestibility. With intensified efforts it is possible for one person to obtain in vitro dry matter solubility estimates on up to 200 samples in 30 days with minimal expense. Results of this investigation points to the end need for further research on the potential of the two digestibility procedures for rationalizing numbers in germplasm collection for initial screening

Use of a Prepaid Cellulase Solution for Screening Forage Grass Germplasm for Digestibility

A reliable rapid and inexpensive laboratory procedure is needed to screen native African forage grass species for forage quality. This study determined the potential of using a prepared cellulase solution to assess in vitro dry matter solubility of 22 native Kenyan forage grasses and 18 native warm season grasses from Missouri, USA. A prepared cellulase solution was used for screening the grass species for digestibility using two procedures. One procedure involved digesting grass samples in prepared cellulose solution without any pre-treatment (CSD), and the other procedure used an acid pepsin pretreatment prior to digestion in the prepared cellulose solution (APCS). The CSD procedures in comparison to APCS generally underestimated in vitro dry matter solubility by a rand of up to 23%. The variations were highly species dependent. Although the APCS procedure more time consuming, it made it possible to identify a group of species resolvable into high (42.6-61.4%), medium (36-40%) and low (29-34%) digestibility. With intensified efforts it is possible for one person to obtain in vitro dry matter solubility estimates on up to 200 samples in 30 days with minimal expense. Results of this investigation points to the end need for further research on the potential of the two digestibility procedures for rationalizing numbers in germplasm collection for initial screening

Genetic variation for selenium content in tall fescue

Selenium is an element necessary for good animal health. No information is available on inheritance of Se concentration in tall fescue (Festuca arundinacea Shreb.). Therefore, the purpose of this investigation was to determine the nature of genetic variation of Se concentration in tall fescue. To accomplish this objective, 15 parental clones were randomly chosen from a broad-based population, and their half-sib (HS) progenies were generated using a polycross mating design. Selenium analysis was determined flourometrically by digesting dried, ground herbage samples in 3:1 HNO3/HCIO4 . Significant genetic variation was observed among HS families in the fall for Se concentration. Heritability, calculated using parent-offspring (PO) regression, gave estimates of 18% for summer and 68% for the fall. Heritability and genetic gain estimates were maximized in the fall, as compared with the summer, largely because of a large environmental component. Genetic gain, expressed as a percentage of the mean of parents, predicted an advance of 1 9 % for fall herbage. Progress in selecting for improved concentrations of Se in the fall in this population of tall fescue is likely

Use of an experimental high-magnesium tall fescue to reduce grass tetany in cattle

Grass tetany (hypomagnesemia) continues to be a problem for the livestock industry. An experimental cultivar of tall fescue (Festuca arundinacea Shreb.) selected for high Mg concentration, HiMag, was compared against four other cultivars for its ability to increase serum-Mg and reduce the risk of grass tetany. Forage from HiMag contained 22% more Mg, 183% more Ca, and 9% more P than other cultivars; K levels were not different. Regardless of cultivar, concentrations of Ca and Mg were lower while K and P were higher during the spring than the autumn. The tetany ratio IK/(Ca + Mg) on basis] was lower for HiMag than for other cultivars (1.34 vs. 1.65); all cultivars had a higher ratio during spring than autumn (1.91 vs. 1.31). In cattle (Bos taurus) grazing trials, blood serum from steers grazing HiMag contained 8% more Mg in autumn 1993 but was not different in spring 1994. Blood serum Mg was not different for cows (either dry or nursing calves) during autumn grazing, but approached significance (P = 0.09) during the spring 1995 calving season (2.32 vs. 2.07 mg/dL for HiMag vs. other cultivars). Except for differences between calves on HiMag compared with Kentucky-31 in autumn 1995 (58 vs. 43 lb, respectively), animal weight change was not affected by cultivar. Normal forage Mg concentrations (>0.20%) and tetany ratios below 2.2 for all cultivars in every season except spring 1995 may explain the lack of consistent animal response. No clinical symptoms of grass tetany were observed at any time during these studies. However, the higher Mg concentration and lower tetany ratio suggest that HiMag could provide a means of reducing the incidence of grass tetany in livestock during periods when risk of the disorder is high