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

Abstract

An evaluation of the factors affecting silage dry-matter intake (SDMI) of dairy cows was conducted based on dietary treatment means. The data were divided into six subsets based on the silage treatments used in the experiments: concentration of digestible organic matter in dry matter (D-value) influenced by the maturity of grass ensiled (n ¼ 81), fermentation quality influenced by silage additives (n ¼ 240), dry matter (DM) concentration influenced by wilting of grass prior to ensiling (W; n ¼ 85), comparison of silages made from primary growth or regrowth of grass (n ¼ 46), and replacement of grass silage with legume (L; n ¼ 53) or fermented whole-crop cereal (WC; n ¼ 37) silages. The data were subjected to the mixed model regression analysis. Both silage D-value and fermentation quality significantly affected SDMI. The average effects of D-value and total acid (TA) concentration were 17.0 g and 2 12.8 per 1 g/kg DM, respectively. At a given D-value, silage neutral-detergent fibre (NDF) concentration tended to decrease SDMI. Silage TA concentration was the best fermentation parameter predicting SDMI. Adding other parameters into the multivariate models did not improve the fit and the slopes of the other parameters remained insignificant. Total NDF intake was curvilinearly related to silage D-value the maximum intake being reached at a D-value of 640 g/kg DM. Results imply that physical fill is not limiting SDMI of highly digestible grass silages and that both physical and metabolic factors constrain total DM intake in an interactive manner. Silage DM concentration had an independent curvilinear effect on SDMI. Replacing primary growth silage with regrowth, L or WC silages affected SDMI significantly, the response to regrowth silage being linearly decreasing and to L and WC quadratically increasing. The outcome of factors affecting SDMI was used to update the relative SDMI index as follows: SDMI index ¼ 100 þ 10 £ [(D-value 2 680) £ 0.0170 2 (TA 2 80) £ 0.0128 þ (0.0198 £ (DM 2 250) 2 0.00002364 £ (DM 2 2 250 2 )) 2 0.44 £ a þ 4.13 £ b 2 2.58 £ b 2 þ 5.90 £ c 2 6.14 £ c 2 2 0.0023 £ (550 2 NDF)], where a, b and c represent the proportions (0-1) of regrowth, L or WC silages from total silage DM. For the whole data set, one index unit corresponded to the default value of 0.10 kg in SDMI. The SDMI index explained proportionally 0.852 of the variation in SDMI with 0.34 kg DM per day residual. The updated SDMI index provides improved basis for the practical dairy cow ration formulation and economic evaluation.

The effects of and interactions between the maturity of grass silage and concentrate starch source when offered as total mixed rations on the performance of dairy cows

“…The responses in DMI and MY of the cows to improved forage digestibility in this work were similar to the results reported in other studies (Rinne et al, 1999;Kuoppala et al, 2008). The positive linear relationship between silage DMI and digestibility was one of the most important factors related to the intake potential of grass silages identified by Huhtanen et al (2007). Delaying the harvest date decreased the estimated in vitro OMD value of the LGS by ,100 g/kg, which corresponded to a similar decrease in the apparent total diet OMD and probably accounted for the 3-kg decrease in daily DMI of cows fed the LGS diets.…”

Evaluation of concentrate factors affecting silage intake of dairy cows: a development of the relative total diet intake index

“…The model predicting the TDMI by combining the effects of silage and concentrate parameters included 943 diets in 202 studies. The additional data have been described in conjunction with the SDMI index development by Huhtanen et al (2007).…”

“…concentrate supplementation and feeding management) are constant. The model was recently updated and extended to include additional silage variables, such as grass harvest (primary growth v. regrowth), herbage species and silage DM and NDF concentration (Huhtanen et al, 2007).…”

Effects of physical form and stage of maturity at harvest of whole-crop barley silage on intake, chewing activity, diet selection and faecal particle size of dairy steers

“…However, NDFI was higher for the steers fed heading-stage silage, which probably was due to the higher digestibility of the NDF, as reflected by the lower concentration of INDF. According to Huhtanen et al (2007), NDFI in dairy cows is negatively correlated with the concentration of INDF.…”

“…These changes during maturation can affect dry matter (DM) intake (DMI) which is negatively related to dietary concentrations of neutral detergent fibre (NDF), when intake is limited by physical factors (Mertens, 1994). The NDF intake (NDFI) is negatively related to the concentration of indigestible neutral detergent fibre (INDF) (Huhtanen et al, 2007).…”