1a. Objectives (from AD-416):
The objective of the proposed research is to determine the nutritional value of canola meal, relative to other protein supplements, and to assess whether feeding this protein source to lactating dairy cows will increase yield of milk and milk components, improve N efficiency and reduce urinary N excretion.
1b. Approach (from AD-416):
Preliminary in situ assessment of variation in ruminal protein degradation in canola meal will be carried out with samples collected from a range of canola production plants. Samples will be chemically analyzed for DM, ash, NDF, NDIN, ADIN, total N, buffer-soluble N, NPN and amino acid (AA) composition. Initial degradability screening of canola samples (plus standard soybean meals) will be conducted by incubating replicates in the in situ rumen for 12 hr in ruminally cannulated cows. Based on these results, a subset representing the range of in situ degradabilities in the sample set will be incubated with the Michaelis-Menten inhibitor in vitro procedure to estimate protein degradation rates and RUP. Degradability of canola meals fed in the in vivo trials will be determined to confirm that the meals have similar degradability. A feeding study will assess canola meal (CM) value, relative to solvent soybean meal (SSBM), as a protein supplement for dairy cows. Five protein sources and amounts will be fed: 2 supplemental proteins (SSBM and CM), at 2 CP levels (15 and 17% CP), with all added CP from SSBM (15 and 17% CP), CM (15 and 17% CP), or half from SSBM and half from CM (17% CP). Additional diets with the same CP sources, but with supplemental rumen-protected Met + Lys (RPML), will also be fed. We hypothesize that if canola meal supplies greater amounts of absorbed His, then that effect would only be apparent after any Met + Lys deficiency were corrected. Basal diets will be composed of alfalfa and corn silages plus high-moisture corn. These dietary treatments will be fed as 2 parallel sets of 5x5 Latin squares; the study will have 5, 3-wk periods. Forty cows will be grouped by parity and days-in-milk into 8 blocks of 5. Ten ruminally cannulated cows, fed the same diets, will also be used in 2 replicated 5x5 Latin squares for omasal and ruminal sampling. Production data from the last week of each period will be analyzed using mixed procedures of SAS. Cows will be fed individually for ad libitum intake; intake and milk yield data will be collected daily. Milk samples will be taken mid-week at 4 milkings during week 3 of each period and analyzed for fat, protein, lactose, SNF and urea. Cows will be weighed 3 consecutive days at start and end of each period. Blood samples and spot samples of feces and urine will be collected at the end of each period. Blood plasma will be deproteinized and analyzed for urea and free AA. Internal markers in urine (creatinine) and feces (indigestible ADF) will be used to estimate urinary excretion of urea and total N, apparent nutrient digestibility, and fecal N excretion. Omasal sampling will quantify ruminal flows of RDP, RUP, microbial protein and AA. Ruminal samples will be analyzed for metabolite concentrations. Samples of all feeds will be analyzed for DM, ash, NDF, ADF, CP, ADIN, NDIN, indigestible ADF, and ether extract. Silage extracts will be analyzed for pH, NPN and fermentation products. Results of the initial production-omasal sampling trial will dictate the subsequent experiments to be conducted.
3. Progress Report:
This project is related to the following objective and sub-objective of the parent project: Objective 1. Improve accuracy, reproducibility, and ease of measuring/estimating feed digestibility; sub-objective 1.B.: Develop and evaluate in vitro methods for assessment of ruminal degradability of dietary proteins. Research is continuing to address both the objective and sub-objective of the parent project. In vitro incubations measured the rumen degradability of protein in canola meal samples that were collected from 12 different manufacturing plants. Estimates of rumen-undegraded protein ranged from 37 to 47%, indicating substantial differences among the plants in the value of the canola meal that they produce. A second set of canola meal samples is being tested to confirm the large degree of variation in nutritional value of this protein supplement. A feeding study conducted with 50 lactating dairy cows tested the relative protein value of canola meal and soybean meal. Compared to soybean meal, feeding canola meal increased yield of milk and milk protein. These effects were similar at both lower and higher total protein contents of the diet. A second study was started in June 2012 using 48 lactating dairy cows to compare the protein value of canola meal and soybean meal when cows were fed different forages: all alfalfa silage, half alfalfa silage plus half corn silage, or all corn silage.