Evaluation of camelina meal as a feedstuff for growing dairy heifers.

The objective of this research was to compare the growth performance, metabolic profile, and nutrient utilization of dairy heifers fed camelina meal (CAM), linseed meal (LIN), or distillers dried grains with solubles (DDGS). A 12-wk randomized complete block design study was conducted using 33 Holstein and 9 Brown Swiss heifers (144.8±22d of age) with 3 treatments. Treatments were 10% of the diet as CAM, LIN, or DDGS (dry matter basis). All diets contained 60% grass hay and 40% concentrate mix. Diets were balanced with corn and soybean meal to be isonitrogenous and comparable in energy content. Diets were individually limit-fed to 2.65% of body weight using a Calan gate feeding system. Frame sizes, body weights, and body condition scores were measured on 2 consecutive days during wk 0, 2, 4, 6, 8, 10, and 12. Jugular blood samples were taken at the beginning of the study and then every 4wk throughout at 3.5h postfeeding for analysis of blood metabolites and metabolic hormones. Rumen fluid samples were taken at the same time as blood sampling via an esophageal tube during wk 8 and 12. Over the duration of the study, dry matter intake and average daily gain were similar among treatments. Body weights tended to be less for heifers fed CAM and greatest for LIN. Gain to feed was similar for the CAM and DDGS and greatest for the LIN. Overall, most frame measurements were similar among treatments. Body length had a tendency to be greater for CAM compared with LIN with DDGS similar to both. Body condition scores were greater for CAM and DDGS compared with LIN. Rumen total volatile fatty acids, acetate:propionate, and pH were similar among treatments. Butyrate was less in the CAM treatment, intermediate for LIN, and greatest for DDGS. Rumen ammonia was less in DDGS compared with CAM and LIN, which were similar. Blood concentrations of glucose, triglycerides, plasma urea N, and cholesterol were similar among treatments. Metabolic hormones, including insulin-like growth factor-1 and thyroid hormones triiodothyronine and free thyroxine, were similar among treatments. Heifers fed CAM had lesser insulin concentration than other treatments. Total-tract digestion of nutrients were similar among treatments, but CAM tended to have greater digestion of organic matter compared with LIN, with DDGS similar to both. Feeding CAM maintained growth performance compared with DDGS and LIN. This study demonstrates that CAM can be used as a protein source for growing dairy heifers.