Effect of physical form of feed and Hay Particle Size on Digestibility, Milk Yield and Nutritional Behavior of Holstein Lactating Cows

In spite of the advantages of total mixed ration compared to the traditional diet, the problem of bulking the diet has not yet been resolved. Moving, storing and transporting of low density crop residues is one of the major problems in using them in feeding animals, especially sending it to distant areas. One of the suggested ways to overcome these problems is to compress this material into a high-density complete feed block. Complete feed block with respect to its distinctive characteristics can affect the milk yield and nutritional behavior of lactating cows and alter the eating behavior of the animal. Changing the particle size of the fodder in complete feed block may also cause different performance – digestive responses in the animal.

Eight Holstein lactating dairy cows (106±25.5 days in milk, 23.18±3.30 kg milk production and 492.66±38.15 kg body weight) were housed in individual pen randomly, and assigned to a 4×4 Latin square change-over design. Four experimental rations were: complete feed blocks containing forage with a geometric mean of 4.15 mm (long block) and 2.68 mm (short block), mesh complete feeds containing forage with a geometric mean of 4.15 mm (long mesh) and 2.68 mm (short mesh). The effect of two physical forms of the feed, including mixed feed in the form of block and mesh as well as the particle size of short or long on nutritional behavior, digestibility of feed and milk yield of Holstein lactating cows were investigated.

Dry and organic matter intake in cows fed short CFBs were greater than cows fed short mash (P <0.05), but the difference between in dry matter intake of this two groups with other groups were not significant. The reduction in particle size of forage increased the digestibility of the feed (P<0.05), however, feed compression had no significant effect on this parameter. Daily yield of raw milk in cows fed short CFBs were about two percent higher than cows fed on short mash (P<0.05), but were not significant difference between groups concerning corrected milk based on four percent fat or milk adjusted for energy. The use of CFBs resulted in a decrease of 2.21% in daily production of milk fat (P = 0.006). Complete feed block increased the duration of eating and the meal size by 18.42 and 21.21 percent respectively, reduced the number of meals by 16.14 percent and increased the eating rate by 10.79% (P <0.05). Increasing the particle size of forage increased the duration of eating and decreased eating rate by 25.55% and 20.2%, respectively (P<0.05), but did not affect the number and size of meals. Compression of complete diet had no effect on the time spent for eating, rumination and total chewing time, but increasing the particle size of forage increased these parameters (P<0.05).

The results of this study showed that using the complete feed block in feeding of Holstein lactating cows compared to the complete feed of mash, had no significant differences in digestibility of diet. However, milk production increased and the amount of milk fat dropped. The complete feed block reduced the number of meals, increased feed intake per meal, and increased feed intake rate.