The nutritive value of Rhodes grass (Chloris gayana) when treated with CaO, NaOH or a microbial inoculant and offered to dairy heifers as big-bale silage

A series of laboratory and animal studies examined the use of chemical and biological agents to enhance the digestibility of Rhodes grass (grass) cut at 60 (young) and 100 (mature) days of regrowth and ensiled as big round ba les. The treatments included an untreated control (C), a microbial inoculan t (I), NaOH, CaO and NaOH plus inoculant (NaOH + I). Inoculant was grown an aerobically, using a starter culture of rumen fluid from cattle given Rhode s grass. Treatments C, 1, NaOH, NaOH + I, were offered separately to twelve dairy heifers, in a 3 X 4 randomized complete block design, repeated twice for each grass silage. C and I had substantial mould growth, compared with no visible mould in NaOH or NaOH + 1. CaO treatment was effective in preve nting mould growth, but had little effect on the chemical composition and i n sacco digestibility of mature grass silage. NaOH reduced NDF content and increased in sacco digestibility (P < 0.05) but not the in vivo digestibili ty (P > 0.05) of both mature- and young-grass silage. The effects of other treatments on nutritive value were non-significant at both stages of maturi ty. NaOH increased the intake of mature-grass silage by 24-26% (P < 0.05), but had little effect on the intake of young-grass silage (P > 0.05). Treat ment I consistently reduced grass silage intake (P < 005) for young-grass s ilage. The findings of these studies show that treating mature Rhodes grass with NaOH will improve its nutritive value and reduce mould growth in cons erved herbage. However none of the treatments in this study had any consist ently positive effects on the in vivo nutritive value or storage quality of young-grass silage.