A team of researchers from the University of Georgia in the US explored the use of dry-extruded cottonseed cake as an alternative to soybean meal in the diets of lactating dairy cows. The study was published in Applied Animal Science.
“The objective of this trial was to evaluate the performance of lactating cows fed diets in which cottonseed cake (CSC) completely replaced either solvent-extracted soybean meal (SBM) or expeller SBM (ESM) to evaluate value of CSC as either source of ruminal degradable or undegradable protein supplement,” the researchers said.
They found there were no differences in cows’ dry matter intake or milk yield based on diet. Energy corrected milk (ECM) yield, the yield and percentage of milk fat, lactose and solids not fat were the same for cows regardless of diet and there were no differences in the change to body weight or body condition score.
However, the percentage of milk protein dropped for cows on the diet with CSC and ESM compared to the control diet. The milk protein percentage for the CSC and SBM diet was similar to the control.
Milk urea nitrogen (MUN) concentrations were reduced for cows on the CSC and ESM diet (CSRDP) compared to levels from cows on the control and CSC and SBM diets, they added.
“Results of the current trial suggest that CSC could be substituted for SBM or ESM in diets fed to mid-lactation dairy cows. However, diets may require additional RDP or lysine to support milk protein synthesis and maintain adequate degradable protein in diets formulated with low CP concentrations.”
“This is also evident by the lower MUN concentrations observed for CSRDP,” they added.
What role for cottonseed in dairy diets?
More than half of the cottonseed generated annually is processed to make cottonseed oil, the researchers said. However, the process leaves a residual cottonseed meal (CSM) that contains fat, protein, fiber and minerals.
Previous research has shown that milk yield and composition from cows receiving diets with CSM was similar to results from cows on diets with solvent-extracted soybean meal and canola meal, they said. However, the efficiency of nitrogen use was better for canola meal and SBM in high producing cows.
More recently, producers have started to use a dry extrusion process to generate cottonseed oil leaving a product higher in oil and containing less protein, they said. The ingredient is considered cottonseed cake rather than cottonseed meal.
“Limited data are available on the nutrient composition of CSC or the response of lactating cows fed diets containing this protein supplement,” the researchers said.
The study sought then to provide more information regarding the use of CSC as a protein ingredient in lactating cow diets.
Feeding trial details
During the feeding trial, 48 mid-lactation dairy cows received one of three diets for eight weeks, the researchers said. “The CSC was produced by dry extruding whole cottonseed at 121 to 149°C for 12 to 20 s,” they added.
The diets included a control diet (CONT) with both soybean meal (SBM) and soybean expeller meal (ESM), a diet (CSRDP) with cottonseed cake (CSC) and ESM, or a diet (CSRUP) with both CSC and SBM, they said. Soybean hulls were used to balance the level of crude protein (CP) and neutral detergent fiber concentrations.
“All diets were calculated to contain 1.56 Mcal of NEl/kg,” they added.
Feed and feed ingredient samples were collected throughout the trial for analysis, the researchers said. Feed intake was tracked, and milk production was noted for each cow at every milking and milk samples were gathered each week to check for fat, protein, lactose, MUN and somatic cell count (SCC).
Cow initial body weight was measured and a body condition score (BCS) established, they said. Final body weight and BSC were recorded at the end of the trial.
During the ingredient analysis, CSC was found to have concentrations of rumen undegradable protein (RUP) and rumen degradable protein (RDP) between those of SBM and ESM, the researchers said.
“The intestinal digested protein concentration in CSC was 30.20% of CP, which was slightly greater than that in SBM (25.85% of CP) but less than that in ESM (65.90% of CP),” they said. “Total-tract digestible protein was less for CSC compared with SBM and ESM.”
Overall, no differences were noted for dry matter intake (DMI) during the feeding trial based on diet, they said. The yields of milk, protein, fat, lactose, solids not-fat and ECM were similar for all diets and the percentages of milk fat, lactose and solids not-fat were “not different.”
“However, milk protein percentage was less for CSRDP (2.84%) compared with CONT (2.96%) but was not different from CSRUP (2.90%),” the researchers said. “Concentrations of MUN were lowest for CSRDP compared with CONT and CSRUP (7.58, 8.56, and 9.27 mg/dL, respectively).”
Body weight and body condition score changes based on treatment were not observed, they said. “Efficiency of production (ECM/DMI) was not different among treatments and averaged 1.27,” they added.
“Results of this trial indicate that the CSC can be substituted for SBM or ESM without affecting intake or milk yield and composition,” the researchers said. “The lower MUN observed for CSRDP suggests that substituting the CSC for SBM may have limited degradable N [nitrogen].”
Source: Applied Animal Science
Title: Production responses to diets supplemented with soybean meal, expeller soybean meal, or dry-extruded cottonseed cake by lactating dairy cows
Authors: N.W. Webb, J.K. Bernard, S. Tao