At two months of age, 48 Holstein-Friesland heifers were randomly allocated to four treatments comprising untreated wheat straw (WS), oven-ammoniated wheat straw (AWS), lucerne hay (LH) or oat hay (OH). Least cost nutrient balanced complete diets were formulated for heifers of different age groups, i.e. 2-6, 6-10, 10-13, 13-18 months and 18 months to first calving. Dry matter (DM) intakes of individual heifers were determined twice weekly. Animals were weighed once weekly, and girth circumference and wither height were measured monthly. From 13 months of age, heifer were observed daily for oestrus and inseminated provided that a minimum live weight of 290 kg had been attained. At two months of age, heifers weighed (mean Â± s.e.) 69 Â±1.1 kg and wither height and girth circumference measured 84.6 ± 0.4, and 94.1± 0.6 cm respectively. The average daily gain of heifers receiving diets containing LH was higher (P < 0.001) from two months of age to calving than that of heifers receiving diets containing WS, AWS or OH (0.76 vs. 0.68, 0.64 and 0.68 kg/day respectively). Heifers receiving LH diets were heavier (P < 0.001) at first calving than heifers fed diets containing other roughages. Wither height at 22 months of age did not differ (P > 0.05) between treatments, the overall mean being 129.3 ± 0.5 cm. Girth circumference of heifers fed diets containing WS, AWS and OH was smaller (P < 0.001) than that of heifers fed LH (179.2, 177.3 and 176.7 cm. vs. 188.3 cm. respectively). Heifers fed diets containing LH also had higher (P < 0.01) condition scores thanheifers fed diets containing other roughages. The lower feeding cost of AWS diets in comparison to other diets should be utilized fully in the rearing of replacement heifers.
"Experientia docet" - Experience is the best teacher