Dietary cation–anion difference of Timothy (Phleum pratense L.) as influenced by application of chloride and nitrogen fertilizer

Abstract

The effectiveness of forages to prevent post-calving hypocalcaemia, when used as a feed source for nonlactating dairy cows, can be predicted by the dietary cation-anion difference (DCAD). Three to four weeks before calving, the ration of non-lactating dairy cows should have a DCAD around )50 mmol c kg )1 DM. In an experiment, swards, based on Timothy (Phleum pratense L.), were used to (i) evaluate the impact of two types (CaCl 2 and NH 4 Cl) and four application rates of chloride fertilizer per season (0, 80, 160 and 240 kg Cl ha )1 ) in combination with two N application rates (70 and 140 kg N ha )1 ) on mineral concentrations and DCAD in the herbage, and (ii) determine the economically optimal rate of chloride fertilizer (Cl op ) for DCAD in herbage. Chloride and N fertilizers were applied in the spring and, after the first harvest in 2003 and 2004 at four locations that differed in K content of their soils. Two harvests were taken during each year. Averaged across N-fertilizer application rates, harvests and locations, the highest rate of chloride fertilizer increased chloride concentration in herbage by 8AE5 g kg )1 dry matter (DM) and decreased DCAD in herbage by 190 mmol c kg )1 DM to values as low as )9 mmol c kg )1 DM. Both types of chloride fertilizer had the same effect on chloride concentration and DCAD in herbage and had no effect on DM yield. When no chloride fertilizer was applied on soils with a high content of available K, application of N fertilizer increased DCAD in herbage by 47 mmol c kg )1 DM at both harvests. Herbage DCAD was lower in summer than in spring by 47-121 mmol c kg )1 DM depending on the location. Application of chloride fertilizer can effectively lower the DCAD of Timothybased herbages; the economically optimal rate of chloride fertilizer in the spring varied from 78 to 123 kg Cl ha )1 , depending on soil K and chloride contents and expected DM yield.

Dietary cation - anion differences in some pasture species, changes during the season and effects of soil acidity and lime amendment

“…The strong relationship between K concentration and DCAD is consistent with earlier work on herbage grasses DCAD Tremblay et al 2006;Pelletier et al 2006Pelletier et al , 2007aPelletier et al , 2007b. In the subset of species sampled over the growing season (Fig.…”

“…It is thus important to consider to what extent the differences between species were due to the time they were harvested. In addition, our observation that lime application to an acid soil can alter the DCAD of grass herbage and the earlier work of Pelletier et al (2007aPelletier et al ( , 2007b, showing that chloride application to grass pastures can lower the DCAD, raise the question of the consistency of the species differences over different environments.…”

“…The mineral balance and DCAD of herbage is known to be strongly influenced by the species in the pasture and the timing of the harvest in the growing season (Braschkat and Randall 2004;Tremblay et al 2006;Pelletier et al 2007a). In addition, fertiliser application can have a substantial effect on DCAD (Pelletier et al 2007a).…”

“…In addition, fertiliser application can have a substantial effect on DCAD (Pelletier et al 2007a). It is thus likely that soil properties such as pH could have an impact on herbage DCAD through effects on the availability of nutrients (Thomas and Hargrove 1984), or because low pH soils often have high soil aluminium (Al), which reduces root growth and thus may affect the mineral nutrition of plants (Delhaise and Ryan 1995).…”

Timothy mineral concentration and derived indices related to cattle metabolic disorders: A review

“…This effect is due to the natrophobic nature of timothy (Griffith and Walters 1966), although it may also be due to timothy adapting to some particular and undetermined conditions. Wide variation in the Na concentration of timothy grown under different conditions (soils, mineral availability, and environments) supports this hypothesis (Huhtanen et al 2000;Du¨rr et al 2005;Pelletier et al 2007aPelletier et al , b, 2008a.…”