AN EVALUATION OF THREE STAGES OF MATURITY OF HAY FED WITH TWO CONCENTRATE LEVELS FOR LACTATING DAIRY COWS

Abstract

Two experiments were conducted on a mixed brome-alfalfa hay grown on the University of Saskatchewan farm in 1977. The hay was cut at three stages of maturity: alfalfa at 10% bloom (cut 10 June); alfalfa at 50% bloom (cut 30 June); alfalfa at full bloom or early seed set (cut 22 July). Intake and apparent digestibility were determined for each of the three stages of maturity (exp. 1) using growing Hereford steers. Voluntary intakes per unit of metabolic body size (g DM/W0.75) were 127.9, 128.1 and 114.0 for the 10 June, 30 June and 22 July cuttings, respectively. Digestibility of dry matter was 70.7%, 67.0% and 58.0%; crude protein digestibility was 70.8%, 66.4% and 53.3% for the respective cuttings. Percent total digestible nutrients were 69.0%, 66.5% and 56.6%. A dairy production trial (exp. 2) was also conducted using the three stages of maturity of hay each fed with a low and a high concentrate level in an incompletely replicated 6 × 6 Latin square design experiment using six cows, six rations (three hays × two concentrate levels) and four feeding periods. Voluntary intakes of hay varied (P < 0.05) as a result of concentrate feeding level (15.0 kg DM/day on low concentrate level vs. 11.9 kg DM/day on the high concentrate level) although total dry matter intakes did not differ (21.7 kg DM/day on low concentrate vs. 21.6 kg DM/day on high concentrate). Total milk production was higher (P < 0.05) on the high concentrate feeding level (25.5 kg/day) than on the low concentrate feeding level (22.9 kg/day) although the low concentrate-early maturity hay combination did not reduce milk production significantly. Milk fat percent was lowest (P < 0.05) for the high concentrate-late maturity hay combination while all other hay-concentrate combinations resulted in similar milk fat percentages. No differences were observed in kilograms of feed dry matter consumed per 100 kg of 4% fat-corrected milk produced. Key words: Maturity, hay, concentrate, dairy cow