Factors influencing the response in intake of silage and animal performance after wilting of grass before ensiling: a review

Abstract

This review examines the response in intake of silage and animal performance after wilting of grass before ensiling. It uses data from eighty‐five published comparisons. Initial analysis identified those variables having the greatest influence on the increase in dry‐matter (DM) intake of grass silage owing to wilting. Total water loss, drying rate of the wilted material and ammonia‐N concentration of the unwilted material were the variables most closely and positively correlated to the proportional increase in DM intake as a result of wilting, with r2 values of 0·344, 0·393 and 0·240 respectively. There was little evidence of curvilinearity in any of the relationships. Stepwise regression analysis was used to identify the best multiple linear regressions for predicting the proportional increase in intake owing to wilting. Factors associated with the extent and rate of water loss in the field (total water loss and drying rate) and the quality of the unwilted material ensiled and its subsequent fermentation pattern (DM digestibility, crude protein, ammonia‐N content of unwilted silage) were the key variables in the relationship. Subsequent analysis related the increase in output of milk energy of dairy cows and liveweight gain of beef cattle to the same independent variables. This indicated that variables shown to describe the response in DM intake in the previous analysis were among those most closely related to the increases in animal performance owing to wilting of grass. To assess whether the increase in animal performance owing to wilting could be explained as a direct response to increased metabolizable energy (ME) intake of wilted compared with unwilted silages, linear relationships were derived between the increase in milk and beef production parameters and the increase in ME intake owing to wilting. From these, it was concluded that there was no clear evidence that wilting reduced the efficiency of utilization of ME in beef or dairy cattle. The present study showed that the increase in milk energy output (measured in MJ) per increase in ME intake (measured in MJ) owing to wilting was linear, with a slope of 0·19. This response from additional ME intake owing to wilting is in line with what would be anticipated when increasing ME intake by other methods.

Qualidade e valor nutritivo de silagens de capim-marandu (B. brizantha cv. Marandu) produzidas com aditivos ou forragem emurchecida

“…Silveira et al (1980) e Narciso Sobrinho et al (1998 verificaram melhora significativa no consumo de MS da silagem de capim-elefante em resposta ao emurchecimento. Wright et al (2000) revisaram 85 trabalhos sobre os fatores que afetam o consumo e o desempenho de animais alimentados com silagem de capim produzida com forragem emurchecida e concluíram que a perda total de água, a velocidade de perda de água da forragem emurchecida, as características da forragem (como teores de PB e N-NH 3 ) e a digestibilidade da MS da silagem proveniente da forragem não-emurchecida são as variáveis mais exatas e positivamente correlacionadas ao aumento do consumo de MS, como resultado do emurchecimento.…”

Ammonia-N concentration in alfalfa silage and its effects on dairy cow performance: a meta-analysis

“…Van Os et al (1995) demonstrated a signifi cant DMI reduction and a trend for decreased milk production in cows fed grass silages with 13 vs 6% ammonia-N. In their study, rumen ammonia was higher in cows fed silage with 13% ammonia-N. Dry matter intake dropped 0.3 Kg/d when ammonia-N in grass silage fed to dairy cows increased from 7 to 20% (Wright et al 2000). The analysis of 47 experiments indicated that high concentrations of ammonia-N in grass silage fed to dairy cows had a negative eff ect on DMI, milk production and milk composition (Huhtanen et al, 2003).…”

Evaluation of the factors affecting silage intake of dairy cows: a revision of the relative silage dry-matter intake index

“…Huhtanen, 1994;Offer et al, 1998;Steen et al, 1998;Wright et al, 2000). These studies have used comparisons between direct-cut v. slightly or heavily wilted silages and direct-cut silage v. field-or barn-dried hay harvested at the same stage of grass maturity.…”

“…Generally the DM intake of wilted silages have exceeded that of directcut silages the magnitude of wilting response being affected by the fermentation quality of direct-cut silage, type of additive used and weather conditions during the wilting period. Most likely a significant part of the wilting response in these studies on SDMI is related to changes in the extent and type of fermentation owing to lower water activity in wilted silages, especially when direct-cut silages are preserved without additives (Yan et al, 1996;Wright et al, 2000). To avoid this problem, we used a statistical model to account for separate effects of silage fermentation quality and DM concentration in the present evaluation.…”