Corn harvested as grain is a relatively new crop for the province of New Brunswick. The recent availability of local corn has the potential to improve the sustainability of the dairy industry in New Brunswick, but there is debate within the industry concerning the value and best use of the grain. This experiment was conducted to assess the feeding value of locally-produced corn grain stored as dry grain, ensiled high moisture corn, or ensiled as high moisture corncob meal (HMCCM, unhusked ears sometimes referred to as snaplage) relative to dry grain obtained from Ontario. Three samples of each were evaluated In Sacco. Rates and extent of digestion were similar for local and Ontario corn regardless of presentation for crude protein and starch, but acid detergent fiber, neutral detergent fiber and dry matter digestibility values were lower for HMCCM than other treatments. A 4 × 4 Latin square study was conducted with 16 Holstein cows and 28 day feeding periods. Milk production and milk protein production were higher (P < 0.05) with the locally produced dry corn than with other treatments. Energy corrected milk was lowest with the HMCCM diet. These results indicated that the value of corn produced in New Brunswick is similar to that produced in Ontario.
Corn is the primary grain used in animal feed in North America, supplying a greater energy density than smaller grains. New earlier maturing corn hybrids are now being grown in New Brunswick (NB) and other Maritime provinces of Canada, reducing the need to import corn from the United States and more temperate Central Canada, thereby improving the sustainability of the local dairy industry.
Once harvested, corn may be stored as dry corn, or ensiled as (high moisture) HM shelled corn, HM ear corn or high moisture corncob meal (HMCCM, unhusked ears also called snaplage). Greater amounts of feed are harvested and available for feeding with high moisture ear corn than with HM shelled corn, and with HMCCM relative to HM ear corn. However, each successive increase in feed volume results in a dilution of the grain with fiber, and it is not known which form offers the greatest economic opportunities for dairy producers under Maritime Canada conditions.
For as much corn as is fed to dairy cows in North America, there is surprisingly little comparative information on its comparative feeding value. Wilkerson et al. [
HM corn has been shown to have a more rapid rate of digestion than dry corn, resulting in a greater portion digested in the rumen. Cooper et al. [
HMCCM is often a means of salvaging a significant part of a corn crop when it cannot be harvested as silage [
A survey of dairy producers and corn growers in New Brunswick found that most have or can readily access equipment to harvest HM shelled corn and HMCCM, without large capital investments in harvesting equipment (personal communication with Milk 2020). The survey also found that dairy producers and feed suppliers suspected that locally grown hybrids of corn differed nutritionally from corn produced in traditional geographic areas. This study was conducted to determine the nutritive value and assess lactational performance of cows provided with imported dry corn, local dry corn, HM shelled corn and HMCCM.
Locally produced samples of dry shelled corn, HM shelled corn, and HMCCM were evaluated, and compared to imported dry shelled corn (Southwest Ontario, Canada). Three samples of each product were obtained for the study. All samples were submitted to New Brunswick Agriculture Laboratory in Fredericton for wet chemistry analyses. Four replicate sub-samples of each product were incubated in the rumens of two, lactating Holstein cows for 6, 12, 18, 24 and 48 hours, using the procedure developed by McQueen et al. [
Residue weights were used to determine dry matter (DM) disappearance. After DM disappearance was determined, residues were pooled by cow and time and analyzed for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and starch. Rates of disappearance of each nutrient were determined using the model described by Orskov and McDonald [
where, A = the soluble fraction, B = the slowly degraded fraction and k = the fractional rate of disappearance of fraction B, e = the exponential function and t = time in hours. Extent of digestion (potential digestibility) for each nutrient pool was computed as the residue remaining after 48 hours, and C = 100-extent of digestion.
Sixteen high producing Holstein cows were used in a replicated 4 × 4 Latin Square experiment, with periods of 28 days. Cows were blocked by age and production. Diets were formulated using the CPM platform of the Cornell Net Carbohydrate-Protein System (CPM Dairy Version 3.01, Cornell, Penn Miner, University of Pennsylvania, Philadelphia, PA, USA) to contain similar levels of net energy and nutrients using the differing grain forms. All corn products were ground to pass through a 4 mm screen prior to feeding, while the HMCCM was processed through a kernel processor at harvest. Diets were mixed and issued twice daily in sufficient quantities to permit approximately 10% orts. Forage DM was determined twice/week and were used to adjust rations as necessary. Each total mixed ration (TMR) was sampled weekly, with the samples stored frozen for analysis. Treatments were: Imported corn-dry shelled corn purchased from a grain elevator in Ontario (ON), Local corn-dry shelled corn produced in NB, Local HM-HM shelled corn grown in NB and HMCCM-snaplage produced in NB.
Cows were weighed at the beginning of each period and at the end of the trial in order to determine change in body weight. Milk weights, feed issued, orts and feed consumed were determined daily. On the last two days of each period, samples of milk were obtained from AM and PM milking. Milk samples were submitted to the Valacta analysis laboratory in Prince Edward Island, Canada for component analysis. Energy corrected milk (ECM) was calculated according to Shirley [
In Sacco digestibility data were analyzed using the ANOVA procedure of Minitab 16 (Minitab Inc., State College, PA, USA) with samples as random variables.
Animal performance parameters were analyzed using the GLM procedure of Minitab. The model included the main effects of animal, period, blocks and treatment. In the model, animals and periods were random and treatment and blocks was computed as fixed effects.
While there were some differences in pool sizes, rates of digestion and digestibility values for nutrients as determined by region, differences much greater than these have been found for corn planted in the same region and crop year [10,11]. Common corn varieties are composed of varying combinations of two types of starch: starch that is made up of highly branched amylopectin is floury and readily holds water while starch that is made up of straight chains of glucose is flinty and does not hydrate well [
ZA = soluble pool, B = insoluble pool, C = unavailable pool, K = rate of digestion (%/h) of the insoluble pool.
ZN = 24 for dry matter and 3 for the remaining nutrients due to pooling of residues for analysis.
Physical form is likewise an important determinant of the rate and extent of digestion of corn in the rumen. Nocek [
Nutrient values for the materials used in the feeding study are given on
All diets were formulated to meet requirements for 35 liters of milk containing 3.6% butterfat and 3.30% total protein. The imported corn was replaced by local shelled corn and local high moisture shelled corn for treatments 2 and 3, respectively. For treatment 4, the HMCCM replaced the imported corn and a part of the corn silage in the diet. The intended nutrient profiles were similar for all treatments (
Results from the feeding experiment are provided in
Processing can contribute to overcoming suspected differences in accessibility to starch in the rumen and to the overall availability of energy from the grain. Ekinci and Broderick [
The authors are indebted to Growing Forward and Milk 2020 for funding this research.