Effects of concentrate crude protein content on nutrient digestibility, energy utilization, and methane emissions in lactating dairy cows fed fresh-cut perennial grass

Abstract

Although many studies have investigated mitigation strategies for methane (CH) output from dairy cows fed a wide variety of diets, research on the effects of concentrate crude protein (CP) content on CH emissions from dairy cows offered fresh grass is limited. The present study was designed to evaluate the effects of cow genotype and concentrate CP level on nutrient digestibility, energy utilization, and CH emissions in dairy cows offered fresh-grass diets. Twelve multiparous lactating dairy cows (6 Holstein and 6 Holstein × Swedish Red) were blocked into 3 groups for each breed and assigned to a low-, medium-, or high-CP concentrate diet [14.1, 16.1, and 18.1% CP on a dry matter (DM) basis, respectively], in a 3-period changeover study (25d per period). Total diets contained (DM basis) 32.8% concentrates and 67.2% perennial ryegrass, which was harvested daily. All measurements were undertaken during the final 6d of each period: digestibility measurements for 6d and calorimetric measurements in respiration chambers for 3d. Feed intake and milk production data were reported in a previous paper. We observed no significant interaction between concentrate CP level and cow genotype on any parameter. Concentrate CP level had no significant effect on any energy utilization parameter, except for urinary energy output, which was positively related to concentrate CP level. Similarly, concentrate CP content had no effect on CH emission (g/d), CH per kg feed intake, or nutrient digestibility. Cross breeding of Holstein cows significantly reduced gross energy, digestible energy, and metabolizable energy intake, heat production, and milk energy output. However, cow genotype had no significant effect on energy utilization efficiency or CH parameters. Furthermore, the present study yielded a value for gross energy lost as CH (5.6%) on fresh grass-based diets that was lower than the widely accepted value of 6.5%. The present findings indicate that reducing concentrate CP content from 18.1 to 14.1% may not be a successful way of alleviating CH emissions from lactating dairy cows offered good-quality fresh grass, but grazing cows could be offered a low-CP concentrate without compromising energy utilization efficiency. Further research is needed to investigate whether larger differences in dietary CP content may yield positive results.

Oscillating and static dietary crude protein supply. I. Impacts on intake, digestibility, performance, and nitrogen balance in young Nellore bulls1

“…A possible explanation for the lack of effect of dietary treatments obtained in the present study is that the total dietary CP content of the low CP treatment (105 g CP/kg DM) may be sufficient to supply degradable CP for rumen microbial activity and MP for muscle production, as proposed by Hynes et al (2016) . The present study found that increasing dietary CP concentration had no significant effect on total DMI or ADG; however, it increased N retention ( Table 3 ).…”

Effect of grain- or by-product-based concentrate fed with early- or late-harvested first-cut grass silage on dairy cow performance

“…Although decreases in dietary CP concentration can increase the risk of restricted microbial activity in the rumen, the PBV values for all diets in this study were still above zero, the recommended minimum allowance (LUKE, 2017). The major increase in manure N excretion can be attributed to urinary N excretion, as observed by Gordon et al (1995) and in other studies with high CP diets (Hynes et al, 2016a(Hynes et al, , 2016b. According to , who reviewed a wide range of dietary treatments (n = 277), on average 84.4% of the incremental N from diets is excreted in urine when using N intake and DMI as independent variables in a bivariate model.…”

Mowing Rice Crop as Ratoon and Applying Chromolaena odorata Compost to Support Food Security

“…Determination of pH (soil and water) 1:10 (v/v) using a pH electrode. According to (Hynes et al, 2016); (Goering & Soest, 1970) the acid-detergent fiber (ADF) procedure provides a rapid method for lignocellulose determination in feedstuffs. The residue also includes silica.…”

“…Rice straw can also be used as animal feed but must be supplemented if used as forage. Rice straw is low in protein and high in crude fiber, so the quality is low, therefore only 20 -30% of the nation's straw production is used for forage, and the rest is composted or burned (Jamilah, Fadhila, and Mulyani, 2017); (Hynes, Stergiadis, Gordon, and Yan, 2016); (Harrell, Bond, and Blanche, 2009).…”