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

Abstract

Effects of dietary crude protein (CP) supply on intake, digestibility, performance, and N balance were evaluated in young Nellore bulls consuming static or oscillating CP concentrations. Forty-two young bulls (initial BW of 260 ± 8.1 kg; age of 7 ± 1.0 mo) were fed ad libitum and were randomly assigned to receive one of six diets with different CP concentrations for 140 d: 105 (LO), 125 (MD), or 145 g CP /kg DM (HI), and LO to HI (LH), LO to MD (LM), or MD to HI (MH) oscillating CP at a 48-h interval for each feed. At the end of the experiment, bulls were slaughtered to evaluate carcass characteristics. Linear and quadratic effects were used to compare LO, MD, and HI, and specific contrasts were applied to compare oscillating dietary CP treatments vs. MD (125 g CP/kg DM) static treatment. Dry matter intake (DMI) was not affected (P > 0.26) by increasing or oscillating dietary CP. As dietary N concentration increased, there was a subsequent increase in apparent N compounds digestibility (P = 0.02), and no significant difference (P = 0.38) was observed between oscillating LH and MD. Daily total urinary and fecal N increased (P < 0.01) in response to increasing dietary CP. Significant differences were observed between oscillating LM and MH vs. MD, where bulls receiving the LM diet excreted less (P < 0.01; 71.21 g/d) and bulls fed MH excreted more (P < 0.01) urinary N (90.70 g/d) than those fed MD (85.52 g/d). A quadratic effect was observed (P < 0.01) for retained N as a percentage of N intake, where the bulls fed LO had greater N retention than those fed HI, 16.20% and 13.78%, respectively. Both LH and LM had greater (P < 0.01) daily retained N when compared with MD. Performance and carcass characteristics were not affected (P > 0.05) by increasing or oscillating dietary CP. Therefore, these data indicate that although there is no alteration in the performance of growing Nellore bulls fed with oscillating CP diets vs. a static level of 125 g CP/kg DM, nor static low (105 g CP/kg DM) and high (145 g CP/kg DM) levels; there may be undesirable increases in environmental N excretion when the average dietary CP content is increased. The results suggest that dietary CP concentrations of 105, 125 g/kg DM, or within this range can be indicated for finishing young Nellore bulls, since it reaches the requirements, reduces the environmental footprint related to N excretion, and may save on costs of high-priced protein feeds.

Dietary protein oscillation: Effects on feed intake, lactation performance, and milk nitrogen efficiency in lactating dairy cows

“…Increased CP digestibility in OS cows is consistent with similar experiments that observed improvements in CP digestibility with sheep [Kiran and Mutsvangwa, 2009 (trend for reduced fecal N); Doranalli et al, 2011] and steers (Archibeque et al, 2007a). However, other studies report unaffected (Collins and Pritchard, 1992;Cole, 1999;Ludden et al, 2002b;Cole et al, 2003;Menezes et al, 2019) or decreased CP digestibility (Ludden et al, 2002a; restricted feeding) when feeding oscillating compared with static CP diets. Inconsistent effects of dietary CP oscillations on CP digestibility may be due to different ingredients or nutrients used when oscillating CP, and higher CP digestion may be observed when oscillating primarily RUP concentrations (Collins and Pritchard, 1992;Tebbe and Weiss, 2020).…”

Oscillating and static dietary crude protein supply: II. Energy and protein requirements of young Nellore bulls

“…The EE was estimated by the solvent extraction method (Socsplus, SCS-08-As, Pelican equipment, Chennai, India) and the assay comprised extraction of lipid with an organic solvent (petroleum ether) at 40–60 °C temperature using a soxhlet apparatus. Digestible energy (DE) intake was obtained by multiplying digestible nutrients by their respective energy values ( NRC, 2001 ): DE = (5.6 × CPI digestible ) + (9.4 × EEI digestible ) + (4.2 × NDFI digestible ) + (4.2 × NFCI digestible ), where the respective digestibility values can be find in Menezes et al (2019 , submitted). The concentration of metabolizable energy intake (MEI) was estimated according to the following equation, MEI = (0.9455 × DE) – 0.3032, as proposed by Detmann et al (2016) .…”

Influence of crude protein content and flint maize processing methods on the performance of early-weaning Nellore calves

“…A similar pattern was observed by Menezes et al . (2019) where young Nellore bulls fed high CP diet (145 g CP/kg DM) had greater apparent CP digestibility than bulls fed diets based on medium (125 g CP/kg DM) or low CP content (105 g CP/kg DM).…”

“…The increase in dietary CP content did not affect the intake and digestibility of DM, OM, NDF and starch, suggesting that intake variable are not restricted or stimulated by dietary CP content (Menezes et al ., 2019). However, as would be expected, the planned difference in dietary N content resulted in a tendency of the linear increase in N intake as dietary CP content increased.…”

“…Similarly, Menezes et al . (2019) suggested that the protein requirements for finishing young Nellore bulls can be met through dietary CP concentrations of 105–125 g/kg DM. Therefore, these data suggest that CP requirements decrease with age and as cattle reach final body weight (BW) (Todd et al ., 2008; Amaral et al ., 2018), it being possible to adjust diets according to the phase of the production system.…”