63 Impacts of protein supplementation frequency on animal performance, rumen fermentation and methane emission from growing beef cattle
Authors: Alemu Aklilu W , Iwaasa Alan D 
Published: September 2024

Abstract
Nutrient supplementation is one of largest expenditure in forage-based beef production systems, especially when forage quality is poor or limited. Decreasing supplementation frequency may have a role in improving sustainability by increasing animal performance and minimizing cost of labor and fuel. This study evaluated the impacts of protein supplementation frequency (canola meal pellet; CMP) on animal performance, rumen fermentation, and enteric methane production from beef cattle fed forage-based diet. A total of 60 crossbred backgrounding steers [body weight (BW) = 278 ± 10 kg) was randomly assigned to one of the three treatments (n = 20/treatment): i) control (no CMP supplementation), ii) control + everyday CMP supplementation (0.83 kg/d per steer), and iii) control + every other day supplementation of CMP. The study was comprised of 21 d of adaptation followed by three 21-d periods, with enteric methane measured for 7 d per period. Animals were fed grass hay-based diets once a day at 0800 h and remained on their respective diets throughout the 63-d study. Diets were formulated considering animal BW, feed nutrient density and environmental condition in accordance with the National Academies of Sciences, Engineering and Medicine. Each treatment group was assigned to a pen, with the cattle and diets rotated among pens weekly to allow the animals to access the GreenFeed system stationed in one of the pens for enteric methane measurement. For measurement of rumen fermentation products, three ruminally canulated steers (BW = 350 ± 20 kg) were allocated to the three treatments using a 3 x 3 Latin Square Design with 21-d periods so that one animal received all the treatments over the three experimental periods. Animals were adapted to the treatments for 17 d and rumen samples were collected between d 19 and 21 at 0700 h, 1000h, 1300 h, 1600 h and 1900 h. Data were analyzed using the Mixed procedure of SAS. Relative to the control treatment (9.9 kg/d), DM intake was 4 to 5% greater (P &lt; 0.001) following CMP supplementation regardless of supplementation frequency. Similarly, average daily gain was greater (7 to 11%, P = 0.01) for CPM supplemented treatments as compared with control (1.04 kg/d) irrespective of supplantation frequency. Rumen fermentation was affected by treatments. Total VFA concentration was greater (P = 0.01) for the every other day supplementation of CMP as compared with control and daily supplementation treatments. Conversely, rumen ammonia concentration was not affected by treatments. The control group had greater acetate and reduced propionate molar proportions that resulted in a 5 to 6% greater acetate:propionate ratio (P &lt; 0.01) as compared with the CMP supplemented groups. Enteric methane production (g/d) was greater for the daily CMP supplementation (P = 0.02) while yield (g/kg daily weight gain) was not affected by treatment. Our results indicated that reduction of protein supplementation frequency improved animal performance without negatively impacting rumen fermentation.