乳量の25および35%相当量の濃厚飼料を給与した泌乳牛のエネルギー利用効率に関する一考察

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To study the energetic efficiency of lactation for cows fed concentrate at rates of 25% and 35% of milk yield, 12 Holstein cows were assigned randomly to either a group fed concentrate at 35% of milk produced (C) or at 25%(R).The experimental period was divided into such three stages of lactation as early (calving to 80 days), middle (81 to 210 days) and late (211 to 305 days) stages. The roughage used was corn silage, 1st cut orchardgrass hay and pasture forage for grazing.Allowances for roughage were determined so that animals were to produce 10 kg and 15 kg of milk daily for C and R, respectively.Ten-day metabolism trials were conducted in the periods of 60, 180 and 280 days on milk. The following results were obtained.Milk yield tended to be higher in C than R without statistical significance.Although peak yield was slightly higher in C than in R, there was no difference in persistency of lactation. Digestibility and metabolizability of energy did not differ significantly between the groups.Milk energy yield (Ym, MJ/kg0.75) regressed on intake of metabolizable energy (ME, MJ/kg0.75) without consideration on live weight gains.The following equation was obtained for pooled results: Ym=0.54 (±0.07) ME-0.23, r=0.840**(P<0.01). Using the regression equation for group R in which cows showed fairly constant live weight throughout the lactation period, metabolizable energy for maintenance was calculated to be 437 k J/kg0.75. Consumption of milk and milk products has grown at a least rate in this decade. In addition, increasing competition for grains between livestocks and people will force ruminants to subsist more on forages than cereals in the near future.Thus, a study on ruminant nutrition should focus on reducing the amount of grain to be fed and increasing the efficiency of utilization of nutrients supplied by roughage. HOLTER et al. found that reducing concentrate feeding for lactating dairy cattle resulted in no detrimental effects on milk production, health and reproductive efficiency of the herd.They reported that production responses to increased concentrate feeding were expected to be minimum when cows were fed high quality forages in free choice, which partly explained the inconsistency on the optimum level of concentrate. The present study purposed to investigate the energetic efficiency of lactating cows fed concentrate at rates of 25% and 35% of milk yield for the first step to minimize grain feeding without reducing the efficiency of utilization of energy for lactation.
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乳量の25および35%相当量の濃厚飼料を給与した泌乳牛のエネルギー利用効率に関する一考察

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