Effects of manipulating the protein content of white clover on silage quality

Abstract

White clover nitrogen N content is generally high and constant throughout the growing season. It is also difficult to manipulate, as N 2 fixation tends to maintain a high N supply to the plant. White clover is a highly heterozygous, natural out-breeder, but self-fertile lines have recently been developed, including one which fails to develop nodules when grown under appropriate physiological conditions. An advantage of this line is that leaf protein content can be manipulated by altering the N supply to the plant and, in addition, it offers the opportunity to examine the effect of protein content on silage quality. This line was grown under varying levels of nitrate-N, giving rise to plants with a range of protein contents which were subsequently conserved as silage in two separate experiments. In experiment 1, both herbage protein and water-soluble carbohydrate (WSC) content varied, with values ranging from 17 to 31 g/kg dry matter (DM) and 52 to 72 g/kg DM, respectively. Protein content also varied in herbage grown for experiment 2, ranging from 20 to 33 g/kg DM, but variation in WSC content (91-101 g/kg DM) was not statistically significant. Silage quality was dependent on the protein content of the fresh herbage in both experiments. A comparison of herbages with high and low initial protein content, from experiments 1 and 2, respectively, revealed that a high protein content resulted in silages with a higher pH .L. Winters et al. / Animal Feed Science and Technology 116 (2004) 319-331 versus 659 g/kg TN), and an increase in free amino acid content when expressed as a proportion of total N (267 g/kg versus 90 g/kg and 323 g/kg versus 200 g/kg TN). A higher initial protein content results in a higher proportion of protein degradation during ensiling.

Nitrogen fertilizer application and developmental stage affect silage quality of timothy (Phleum pratense L.)

“…These results agree with those from other studies where the BC of herbage was higher at higher rates of N‐fertilizer application (Podkowka and Potkanski, 1991; O'Kiely et al. , 1997; Winters et al. , 2004).…”

“…These results agree with reports that increasing the rate of N‐fertilizer application generally reduces the concentration of WSC in grass herbage (Jones, 1970b; Smith, 1973; Wilman and Wright, 1983; Podkowka and Potkanski, 1991; Keating, 1997; O'Kiely et al. , 1997) and also in a non‐nodulating line of white clover (Winters et al. , 2004); a limiting N supply results in slower growth and increased accumulation of fixed carbon in the form of WSC.…”

“…Silage pH increased with increasing N‐fertilizer application rate and this increase was more pronounced at the first three developmental stages at Normandin in 1999 (Table 5). Increasing the rate of N‐fertilizer application to white clover (Winters et al. , 2004) or perennial ryegrass (Keady and O'Kiely, 1996) also resulted in silages with higher pH values.…”

Assessing the impacts of agricultural intensification on biodiversity: a British perspective

“…Biodiversity benefits can be obtained without sacrificing production by controlling losses of nutrients and pesticides through, for example, developments in precision agriculture (Godwin et al 2003), the use of buffer areas (Correll 2005;Bradbury & Kirby 2006) and increasing the nitrogen use efficiency of livestock by manipulating their feed (Winters et al 2004). It is also possible to benefit biodiversity by allowing more non-crop species to persist within the field, for example, by allowing weeds and invertebrates to build up in some parts of the field (Sotherton 1991;Haysom et al 2004), or at some times of the year (Moorcroft et al 2002).…”

Direct acquisition of organic N by white clover even in the presence of inorganic N

“…It can fix nitrogen (N) directly from the air via symbiosis with Rhizobium (Oldroyd and Downie 2004), which is also reflected in the generally high N content of plants (Winters et al 2004). All N-rich compounds may be released to surrounding plants either after clover decay or through exudation of nitrogenous compounds when the source plant is still growing and can act as a source of nutrients for subsequent crops (Paynel and Cliquet 2003;Rasmussen et al 2013).…”