High-digestible silages: Maintaining milk yield and viable methane levels

Nonetheless, various studies have shown the advantages of including high-digestible silages in dairy cow diets, exhibiting improved milk yields (Randby et al., 2012; Alstrup et al., 2014; Weisbjerg and Johansen, 2017). Álvarez et al. (2020) established a mathematical correlation showing that high-digestible silages can induce high milk yields with lower concentrate levels compared with low-digestible silages. At low levels of concentrate, higher milk yields were achieved with increased silage digestibility. As concentrate intake levels increase, energy-corrected milk (ECM) differences between silages disappear due to a lower ECM marginal response with high-digestible silages.

The effect of silage digestibility and concentrate level on methane emissions requires a combined evaluation.

The objective of the following study was to test the meta-analysis of Álvarez et al. (2020) by challenging cows with different silage digestibility and evaluating the interaction between silage digestibility and concentrate level on cow responses. Assessing the effects of changes in silage digestibility and concentrate supply on milk yield, feed intake, body weight, and methane production. The aim was to investigate further and evaluate such scenarios from a climate perspective, measuring methane emissions for different silage digestibility and concentrate levels.

Materials and Methods

The experiment was conducted at the Animal Production Experimental Center at the Norwegian University of Life Sciences.

60 Norwegian red cows were used for the experiment. Comprised by: 26 first lactation cows, 22 second lactation cows, and 12 older cows which were loosely housed with concrete floors and rubber mats with sawdust for the whole experiment.

The experiment was a complete randomized block design including 3 periods:

• The pre-experimental period lasted 20 d and all the cows were fed a common silage for ad libitum intake and concentrate according to yield.
• Next, response period 1 lasted 17 d. Cows were divided into 2 treatments, where a low-digestible silage (LDS) was fed to half of the cows, and the other half were fed a high-digestible silage (HDS). Both groups were fed silage for ad libitum silage intake. Concentrate was optimized according to yield and type of silage offered. During this period, the effect of silage was evaluated using a mixed model, including the results from pre-experimental period, with parity as a covariate and animal as a random effect.
• In response period 2, which lasted 20 d, the concentrate level was evaluated by dividing the silage digestibility treatments further into 3 subgroups. Concentrate was increased by 2 kg of dry matter (DM) per day, decreased by 2 kg of DM/d, or remained unchanged.

Results and Discussion

Intake

Total DMI was, on average, 3.0 kg of DM/d higher for cows in the HDS than those in the LDS (P < 0.001). Also, DMI increased 0.53 kg of DM/d with each increase in kilograms of DM/d of concentrate offer (P < 0.001), regardless of silage digestibility treatments, as no interaction was found between silage digestibility and change in concentrate offer (P = 0.76). Higher DMI for the HDS group could be explained by DMIs, which was, on average, 3.8 kg of DM/d higher for the HDS group than for the LDS group (P < 0.001). No interaction was found for DMIs between silage digestibility and concentrate offer.

Milk Production and Composition

Milk yield was, on average, 3.0 kg higher for the HDS than the LDS treatment (P = 0.001) and increased linearly by 0.49 kg of milk per kg increased offer of concentrate (P = 0.01), regardless of silage digestibility, as no interaction was found (P = 0.90). Similar response was found for ECM, with, on average, a 3.5 kg higher yield for the HDS than the LDS treatment. Irrespective of silage digestibility, ECM showed a linear increase in 0.66 kg per kg of DM of concentrate offer increase, as no interaction was found (P = 0.13). Silage digestibility did not affect fat and protein concentrations.

For both silage digestibility treatments, the lactose concentration increased with an increased concentrate offer (P = 0.02). Fat, protein, and lactose yield were highest for the HDS treatment (P = 0.03 for fat yield and P = 0.003 for protein and lactose yield) and were affected by concentrate offer (P < 0.05), although no interaction was detected for any of these parameters (P > 0.10).

Methane emissions

Total methane production increased with increased concentrate intake, regardless of silage digestibility. Methane emissions per unit of milk were affected by total DM intake rather than by changes in silage digestibility and concentrate level.

CONCLUSIONS

• Researchers aimed to make a better assessment regarding the relationship between silage digestibility and concentrate supply levels on different parameters such as feed intake, milk yield, and methane production.
• From the obtained results, it was seen that unlike low-digestible silages, high yields can be maintained with low concentrate levels with HDS. This demonstrates the benefits of feeding high-digestible silages with low concentrate levels, which tend to disappear if concentrate levels are increased.
• Results from this study also revealed that methane production was not affected by the feeding of high-digestible silages with low concentrate levels. Researchers found that total feed intake has greater influence on methane production, than silage digestibility and concentrate levels when silage is fed ad libitum.
• Finally it must be highlighted that the results for this study are based on short-term periods. Therefore, these could change and exhibit differences if study periods are extended. Taking this into consideration, the aforementioned results must be interpreted accordingly.

Source: Abstract taken from “High-digestible silages allow low concentrate supply without affecting milk production or methane emissions.”