Impacts of rumen degradable or rumen undegradable protein supplement on supplement intake behavior and performance of yearling heifers and cows grazing dryland pastures

Authors: MANOUKIAN, MARLEY - Montana State University; DELCURTO, TIM - Montana State University; KLUTH, JANESSA - Montana State University; CARLISLE, TANNER - Montana State University; DAVIS, NOAH - Montana State University; NACK, MAKAE - Montana State University; WYFFELS, SAM - Montana State University; VAN EMON, MEGAN - Montana State University; Geary, Thomas; SCHEAFFER, ABE - Sweetpro

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2022
Publication Date: 11/29/2022
Citation: Manoukian, M.K., Delcurto, T., Kluth, J., Carlisle, T., Davis, N., Nack, M., Wyffels, S., Van Emon, M.L., Geary, T.W., Scheaffer, A. 2022. Impacts of rumen degradable or rumen undegradable protein supplement on supplement intake behavior and performance of yearling heifers and cows grazing dryland pastures. Animals. 12. Article 3338. https://doi.org/10.3390/ani12233338.
DOI: https://doi.org/10.3390/ani12233338

Interpretive Summary: This study was conducted to evaluate intake and performance of beef cattle provided different protein supplements on pasture. Protein sources were rumen degradable protein (RDP) and rumen undegradable protein (RUP) supplied as pressed blocks provided in two time periods. Protein supplement was provided before and during the breeding season. Intake, intake behavior, and weight gain were compared between cattle offered either protein type. Heifers ate more RDP than RUP in the first period than the second. The heifers ate the RUP pressed blocks faster than the RDP pressed blocks throughout the trial. The cows ate more RUP in the first period than the second. Body weight and body condition of cows and heifers were not different between RUP and RDP fed animals throughout the experiment. The cows fed the RDP pressed block gained more body weight each day (ADG) than cows fed the RUP pressed block. There was greater variation in individual intake among cows eating RUP than RDP during period 2. In conclusion, protein type impacted intake behavior of cows and heifers and RDP cows had greater ADG, but protein type had little impact on performance.

Technical Abstract: The objectives of this study were to evaluate the differences between rumen degradable protein (RDP) and rumen undegradable protein (RUP) on supplement intake behavior and animal performance. Angus and Red Angus-based yearling heifers (n = 40), two-year old cows (n = 36) and three-year old cows (n = 24) were used in a randomized complete block design and stratified by weight and body condition score to one of two treatments: 1) pressed supplement block containing RUP (RUP) and 2) pressed supplement block containing RDP (RDP). Individual supplement intake variables were measured using the SmartFeed Pro trailers (C-Lock Inc., Rapid City, SD) during an 84-d trial separated into two periods: Period 1) d 4 – d 45 and Period 2) d 46 – d 84. Statistical analysis was completed in R. Heifer and cow supplement intake (kg/d) displayed (P < 0.01) a treatment × period interaction. The RUP heifers and RDP cows consumed more in Period 2 than Period 1, whereas RDP heifers and RUP cows consumed more in Period 1 than Period 2. Intake rate (g/min) demonstrated (P < 0.01) a treatment effect for heifers, with RUP consuming supplement faster compared to the RDP treatment in both periods. Intake rate for cows demonstrated (P < 0.01) a treatment × period interaction with RUP cows in Period 1 having faster intakes than Period 2, and RDP cows having the inverse. Cow intake variation (% CV) also displayed (P < 0.01) a treatment × period interaction with RUP cows having more variation in Period 2, while RDP cows had less variation in intake in Period 2. There were no differences (P = 0.40) in heifer or cow initial and final BW or BCS. There was no difference (P = 0.23) in heifer ADG. Cows supplemented with RDP had greater (P < 0.01) ADG than RUP supplemented cows. In conclusion, RDP and RUP impacted intake behavior of cows and heifers but had minimal impacts on performance.