Forage quality of genetically diverse alfalfa germplasms at four phenological growth stages

Abstract

Forage quality of various alfalfa (Medicago sativa L.) cultivars has been determined under different environmental conditions, and numerous trials with alfalfa have documented an inverse relationship between forage quality and maturity. Little information is available, however, regarding the comparative forage quality of the germplasm sources from which most USA cultivars were developed. We compared forage quality of these germplasm sources at four phenological stages under disease-and insect-free conditions in a greenhouse. Germplasm sources (cultivars) tested were: Indian (Sirsa # 9), African (African), Peruvian (Hairy Peruvian), Flemish (DuPuits), Turkistan (Lahontan), Chilean (Kansas Common), M. varia (Grimm), and Ladak (Ladak). Four harvests were taken and forage was separated into four phenological stages: vegetative, early bud (1-3 buds-per-stem), late bud (> 3 buds-per-stem), and bloom. The germplasm source X phenological stage interaction was significant for crude protein (CP) and in vitro digestible dry matter (IVDDM) concentrations. M. varia showed the least decline in IVDDM and CP with increasing maturity. M. varia had higher IVDDM than did African and Indian at late bud and bloom stages. Indian and Flemish had higher CP than did Turkistan and Peruvian at late bud and bloom stages. Alfalfa germplasm sources differ in forage quality when comparisions are made within similar stages of phenological development.

Strategies of plant breeding for improved rumen function

“…Advances in understanding the genetic control of forage maize traits relating to yield, silk date, protein content and digestibility may be directly transferable to other monocots such as the forage grasses Lubberstedt et al, 1997;Burstin et al, 1995;Stuber, 1995). Although QTLs can vary according to stage of growth (Lenssen et al, 1990) in alfalfa the protein content was found to be inversely correlated with maturity regardless of genetic background, although part of this effect could be due to change in leaf:stem ratio (Lenssen et al, 1990). From a gene bank search, 272 genes suitable for cloning were identified having originated from alfalfa (Volenec et al, 2002).…”

“…The forage needs sufficient mechanical strength to be self-supporting as it grows, but it is desirable if it can also be easily broken down in the rumen. These parameters vary considerably between forages and plant parts and measures of in vitro digestibility are generally positively correlated with the protein content of the feed (Riday et al, 2002;Argillier et al, 1998;Lenssen et al, 1990;Buxton & Casler, 1983). There is a need to increase the proportion of the forage protein that is undegradable in the rumen, especially for legumes (Smith et al, 1997).…”

“…Improvements have previously been realised based on selection for lines with low initial rates of fibre digestion, suggested to be due to increased thickness of cell walls . Further advances are likely to come about via increases in stem length or composition based on natural variation in the gene pool of collections, avoiding coincident decreases in protein content (Riday et al, 2002;Jung et al, 1997;Lenssen et al, 1990). A further way to increase the quality of alfalfa is to address morphological traits, such as changing the leaflet size or number, as leaf quality declines through the growing season to a lesser extent than does stem quality (Buxton, 1996).…”

Critical Harvest Stage Improves Alfalfa Production Performance, Overwintering Rate and Economic Benefits under Drip Irrigation

“…The growth and development of alfalfa plants are closely linked to the harvest stage. Alfalfa varies greatly in morphological structure, and physiological and biochemical characteristics at different harvest stages (Lenssen et al 1990). Additionally, some reports have shown that alfalfa has higher crude protein content and lower crude fiber content at budding stage and early flowering stage than at its full bloom stage, while the forage yield of alfalfa at flowering stage is higher, but the feeding value of alfalfa at flowering stage is lower than that at budding stage and early flowering stage (Lamb et al 2003;Testa et al 2011).…”