The effects of high-sugar ryegrass/red clover silage diets on intake, production, digestibility, and N utilization in dairy cows, as measured in vivo and predicted by the NorFor model

Abstract

Grass silage-based diets often result in poor nitrogen utilization when fed to dairy cows. Perennial ryegrass cultivars with high concentrations of water-soluble carbohydrates (WSC) have proven potential for correcting this imbalance when fed fresh, and have also been shown to increase feed intake, milk production, and N utilization. The possibility of achieving corresponding effects with silage-based diets was investigated in change-over experiments in an incomplete block design with 16 (yr 1) or 12 (yr 2) Swedish Red dairy cows in mid lactation. Measurements on N excretion and rumen parameters were performed on subgroups of 8 and 4 cows, respectively. In yr 1, 2 ryegrass cultivars (standard = Fennema; high-WSC = Aberdart) and 2 cuts (first and second) were compared. In all treatments, ryegrass silage was mixed 75/25 on a dry matter (DM) basis, with red clover silage before feeding out. In yr 2, 1 basic mixture from the different cuts of these 2 cultivars was used and experimental factors were red clover silage inclusion (25 or 50%) and sucrose addition (0 or 10%) on a silage DM basis. Differences in WSC concentration in the silage mixtures in yr 1 were minor, whereas the differences between cuts were more substantial: 100 compared with 111 g/kg of DM for first-cut silage and 39 compared with 47 g/kg of DM for second-cut silage. The silages fed in yr 2 had a WSC concentration of 115 or 102 g/kg of DM (25 or 50% red clover, respectively), but when sucrose was added WSC concentration reached 198 and 189 g/kg of DM, respectively. Milk production (kg/d) did not differ between treatments in either year. Red clover inclusion to 50% of silage DM increased milk protein. Nitrogen efficiency (milk N/feed N) increased from 0.231 to 0.254 with sucrose inclusion in yr 2 (average for the 2 red clover levels). Overall rumen pH was 5.99 and increased sucrose level did not affect pH level or daily pH pattern. Sucrose addition reduced neutral detergent fiber digestibility, particularly at higher inclusion rates of clover. Rumen pool of total purines did not differ between treatments, nor did protein production assessed from urinary allantoin. The NorFor feed evaluation model overestimated digestibility of neutral detergent fiber and N, but underestimated N excretion in feces. We concluded that addition of WSC to dairy cow diets at levels up to 3 kg of WSC per day (>14% of DM) does not dramatically affect cow performance.

Macronutrient balancing in free‐ranging populations of moose

“…As we used proportions-based nutritional geometry, an error in the estimation of one parameter affects the relative value of another parameter. In addition, although our estimates of microbial-N resemble those from comparable studies of dairy cows (Bertilsson et al, 2017;Bertilsson & Murphy, 2003;Eriksson et al, 2004), there are some uncertainties related to how well our method estimated the amount of microbial-N/mg purine marker in moose rumen. Much of what is known about interactions between diet and rumination comes from studies of domestic grazers, whose digestive physiology differs significantly from the moose (Clauss et al, 2011).…”

“…Selected samples were analyzed for dm, ash, Kjeldahl nitrogen (total N), crude fat (hereafter called “lipids”), neutral‐detergent fiber (NDF), acid‐detergent fiber (ADF), and lignin using conventional wet chemistry techniques (see Appendix S1 Supplementary methods) described by Bertilsson et al. ( 2017 ). To estimate the portion of nondigestible protein, we measured insoluble nitrogen remaining in acid‐detergent fiber (ADF‐N).…”

“…We also analyzed in vitro organic matter digestibility of the plant material, using conventional wet chemistry techniques (see Appendix S1 , Supplementary methods) described by Bertilsson et al. ( 2017 ). We report estimates of the digestible fraction of plants’ NDF (dNDF), based on this in vitro analysis.…”

“…We refer to this estimate as TNC1 to clarify the methodological difference of estimation of TNC of rumen samples, for which we used the subtraction method (TNC2, see above). We also analyzed in vitro organic matter digestibility of the plant material, using conventional wet chemistry techniques (see Appendix S1, Supplementary methods) described by Bertilsson et al (2017). We report estimates of the digestible fraction of plants' NDF (dNDF), based on this in vitro analysis.…”

A review on the potentials of using feeds rich in water‐soluble carbohydrates to enhance rumen health and sustainability of dairy cattle production

“…As an illustration, two experiments testing ryegrass, either fresh or ensiled with a WSC intake of 3.2 to 4.1 kg day −1 , observed no change in ruminal pH. 58,59 In two independent studies, we also found no risk of SARA as a result of feeding WSC-rich ryegrass hay at WSC intake levels up to 3.3 kg day −1 , even in combination with starch (WSC of 2.7 kg day −1 plus starch of 3.6 kg day −1 , exceeding 300 g kg −1 DM in starch plus WSC). 60 One reason why WSC-rich ryegrass hay alone or with starch did not lead to SARA is the still high level of peNDF contained in hay, which helps maintain a high chewing index, 61 as well as the high CP content of the WSC-rich hay, adding to the ruminal buffering capacity.…”