Interaction between feed use efficiency and level of dietary crude protein on enteric methane emission and apparent nitrogen use efficiency with Norwegian Red dairy cows1

Abstract

We assessed the interactive effects of gross feed use efficiency (FUE, milk yield/kg DMI) background (“high” = HEFF vs. “low” = LEFF) and graded levels of dietary CP (130, 145, 160, and 175 g/kg DM) on milk production, enteric methane (CH4) emission, and apparent nitrogen use efficiency (NUE, g milk protein nitrogen/g nitrogen intake) with Norwegian Red (NRF) dairy cows. Eight early- to mid-lactation cows were used in a 4 × 4 Latin square design experiment (2 efficiency backgrounds, 4 dietary treatments, and 4 periods each lasting 28 d). The diets were designed to be identical in physical nature and energy density, except for the planned changes in CP, which was a contribution of slight changes in other dietary constituents. We hypothesized that HEFF cows would partition more dietary energy and nitrogen into milk components and, as such, partition less energy in the form of methane and excrete less nitrogen in urine and feces compared with their LEFF contemporaries. We observed no interactions between dietary CP level and efficiency background on DMI, other nutrient intake, NUE, CH4 emission, and its intensity (g CH4/kg milk). Gradually decreasing dietary CP from 175 to 130 g/kg DM did not affect DMI, milk and energy-corrected milk yield, and milk component yields and daily CH4 emission. However, decreasing dietary CP increased NUE and reduced urinary nitrogen (UN) excretion both in quantitative terms and as proportion of nitrogen intake. The HEFF cows showed improved NUE and decreased CH4 emission intensity compared with the LEFF cows. In the absence of interaction effects between efficiency background and dietary CP level, our results suggest that CH4 emission intensity and UN excretions can be reduced by selecting dairy cows with higher FUE and reducing dietary CP level, respectively, independent of one another. Furthermore, UN excretion predictions based on milk urea nitrogen (MUN) and cow BW for NRF cows produced very close estimates to recorded values promising an inexpensive and useful tool for estimating UN excretion under the Nordic conditions where ordinary milk analysis comes with MUN estimates.

Relationship between feed protein content and faeces nitrogen content in early lactation dairy cows

“…Results from previous studies supported that decreasing CP content in feed decreases faeces nitrogen content (Arunvipas et al, 2008). Indeed, Norway researchers found a tendency for increased faeces nitrogen excretion with increasing CP level in ration (P=0.063; Kidane, 2018). Nitrogen excretion in faeces in the present study ranged from 0.16 kg d -1 in B group to 0.15 kg d -1 in C group, but the difference was not significant.…”

“…Milk urea content was higher in dietary group C probably due to insufficient NEL content in ration, which is related to differences in chemical content of dietary group C. The ECM in dietary group C was reduced by 5.4% compared with group B. Milk traits did not differ among dietary groups consistently with previous studies where the decrease of CP in feed ration did not lead to significant effects on milk production traits (Kalscheur et al, 1999, Amanlou et al, 2017, Kidane et al, 2018.…”

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

“…Mean intake of DM and other constituents, except for the planned difference in N ( Table 3 ), were not different between dietary treatments, suggesting that neither the dietary CP content nor the way CP is delivered in diet restricts or stimulates intake parameters. As such, the absence of the effects of dietary CP content in voluntary intake suggests that the dietary inclusion of 105 g CP/kg DM, even though considered the lowest CP content relative to other treatments, fulfilled minimum requirements for microbial growth and feed degradation in the rumen ( Kidane et al, 2018 ). It is suggested ( Marini and Van Amburgh, 2003 ; Brake et al, 2010 ) that under such low CP diets, it is expected that the higher turnover rate of urea N with reduced clearance in the kidneys and increased clearance from the digestive tract would compensate for the low level of dietary CP for rumen microbes.…”

Fourier transform infrared spectroscopy of milk samples as a tool to estimate energy balance, energy- and dry matter intake in lactating dairy cows

“…Silage consumption was automatically recorded through feeding troughs placed on weighing cells (BioControl AS, Rakkestad, Norway) and calculated as described by Kidane et al . (2018). Concentrate was provided in the AMS and in separate concentrate feeding stations.…”

“…For analysis of nutrient composition, the monthly samples of silages and concentrate were analyzed as described by Kidane et al . (2018).…”