Interaction of Dietary Grain and Forage Sources on Performance and Feeding Behavior of Dairy Cows

Grains are typically used as energy-efficient ingredients for high-yielding cows. On the other hand, the use of forage sources in the diet is recommended to improve ruminally fermentation and ultimately maintain health and improve livestock production. Given the contradictory results reported in recent research on the effects of feeding of different sources of grain and forage in dairy cows, we conducted a study aimed at investigating the interaction effects of grain (barley and corn) and forage (alfalfa and corn silage) source in rations on the productive performance of Holstein dairy cows.

Eight Holstein dairy cows (milk production: 46.2 ± 2 kg / day) were used to investigate the interactions between dietary source of grain and forage on productive performance. This experiment was conducted in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement with 4 treatments over 4 periods of 21 days (15 days for dietary adaptation and 6 days for data collection). The first factor was the source of grain used in the diet (barley or corn) and the second factor was the source of forage used (alfalfa or corn silage). Experimental diets were fed as total mixed ration twice daily (7:00, 17:00) and milking was done 4 times daily (4:00, 10:00, 16:00, 22:00). Sampling was performed to collect feed samples and their residues, milk production and composition, rumen fluid, and animal feeding behaviors.

Dry matter intake (23.4 vs. 21.9 kg / day), milk yield (46.9 vs. 44.5 kg / day) and milk fat percentage (3.12 vs. 2.88%) in treatments containing corn grain were more than treatments containing barley grain (P <0.05). Nitrogen uptake was higher in corn-based treatments, but milk nitrogen, an indicator of feed nitrogen utilization efficiency, was lower in these treatments compared to barley grain. The effects of dietary forage source on feed intake and milk production were not significant, but dry alfalfa hay increased the percentage of milk fat compared to corn silage (3.08 vs. 2.92 percent). The use of corn silage forage increased the rumination time and total chewing time as minute per day and minute per kg of dry matter consumed (P <0.05). Although cows consuming corn silage spent more time for eating per kg of dry matter, but cows consuming alfalfa hay consumed more dry matter per meal. Consumption of corn compared to barley tended to increase dry matter intake per meal (P = 0.1). Percentage and amount of milk fat produced as well as fat-corrected milk production had a direct relationship with ruminal pH at three hours after morning feeding (P <0.05).

Although the interaction of main factors in this experiment on functional parameters of dairy cows was not significant, but dry matter intake at each meal when using barley grain in treatments based on corn silage as forage source compared to dry forage Alfalfa was lower but not affected by forage source in treatments based on corn grain. This demonstrates the positive effects of using corn grain in corn silage-based diets to prevent reduced feed intake. Because diets containing corn silage compared to dry alfalfa hay are expected to decrease feed intake due to increased feed particle size as well as higher rumen acidity, however, this higher acidic state will be exacerbated if ground barley grain be used in the diet.