畜産学

An investigation of the effects of feeding management on the milk production and reproductive efficiency of Holstein cattle reared in University Farm, Faculty of Agriculture, Kyushu University was conducted. The intake and nutritive value were estimated for the roughages fed from July to December, 1991. Milk yield was recorded daily and milk quality and body size were measured twice and once in every month, respectively. Calving intervals were calculated from the record of reproduction from 1983. Forage oats (Avena sativa) and Italian ryegrass (Lolium multiflorum) silage followed by Sudangrass (Sorghum sudanense) and corn (Zea mays) silage were fed through the year with the hay of Italian ryegrass or of Sudangrass or of bahia grass (Paspalum notatum) dominated pasture. A commercial formula feed, wheat bran, barley, flaked corn and lucern pellet were used as concentrates. The crude protein and DCP contents were low in the roughages especially in the hay. Silage quality was good for corn but the content of acetic acid was relatively high and a small amount of butyric acid was produced in Italian ryegrass silage. The supply of nutrient was relatively lower than the requirements of the individuals of large body size and high milk yield during early lactation for about 5 months after calving. The lowered fertility caused by prolonged nutrient deficiency resulted the longer calving intervals of more than 20 months. Milk fat percentages for most of the individuals of less than 15kg/ day milk in late lactation were higher than 3.5%, though those for the individuals of higher milk yield at peak lactation occasionally showed lower values than 3.5%. As the amount of provided fiber was not less than 20% for ADF in dry matter of all the feed, the low content of digestible fiber in forage was supposed to be associated with the milk fat depression. To achieve a good reproductive efficiency and higher yield and quality of milk, it was concluded that the improvement of nutritive value of hay fed with silage was necessary to encourage higher dry matter and nutrient intake meeting the body size and phase of lactation cycle of an individual.