Comparison of two forage sorghum varieties with corn and the effect of feeding their silages on eating behavior and lactation performance of dairy cows

This study examined the biomass yield and nutritive value for lactating cows of two sorghum silages, a new brown mid-rib BMR-101 variety (BMR) and the commercial hybrid FS-5 widely used in Israel, in comparison with the corn Oropesa silage. Forages were grown in a Mediterranean climate in five replicate plots, harvested by a combine harvester at the soft dough stage and ensiled in bunker silos. The BMR plants had high degree of lodging, and the yield of forage dry matter (DM) was highest for corn, intermediate for FS-5 and lowest for BMR. Ensiling resulted in moderate DM losses for corn and FS-5 and higher losses for BMR, but all silages were stable after exposure to air. The in vitro DM digestibility (IVDMD) of BMR and corn silages were similar and higher than that of the FS-5 silage. Forty-two milking cows were assigned into three groups of 14 cows each, that were similar in their initial performance and DM intake, and fed three total mixed rations (TMR) containing either BMR, FS-5 or corn silages as the basal forage, in a 3 × 3 Latin square design. Each period consisted of 2 adaptation weeks to the TMR plus 5 data collection weeks. There were no differences in DM intake among cows fed the three silage-based TMR, but the number of voluntary daily meals per cow was higher for the FS-5-fed group versus the BMR and corn groups. In contrast, DM intake per meal and average meal duration were higher for the cows fed the corn and BMR-based TMR. Rate of feed consumption and daily eating duration were similar in the three treatments. Milk yield of the cows fed the corn-based TMR was higher than that of the FS-5 group, while that of BMR group was intermediate (42.1 vs. 40.7 and 41.4 kg /d, respectively). The two groups fed the sorghum TMR had higher milk fat production, while the group fed corn silage TMR had higher milk and milk protein production and moderate milk fat yield and content, as well as the lowest loss of body weight (BW). However, silage yield per hectare, digestibility of the silage, and availability of water for irrigation are the dominant parameters when deciding which forage varieties to grow.