Growth, Luteal Activity, and Pregnancy Rates of Three Breed Types of Dairy Heifers in a Forage-Based Development Program

Growth, luteal activity, and pregnancy rates were evaluated in 89 dairy heifers raised as contemporaries. Breed types were Holstein (H, n=35), Jersey × H (JH, n=30), and Brown Swiss × H (BSH, n=24); they ranged in age from 129 to 205 d at the beginning of the trial. Heifers grazed pasture and received grain supplementation to ensure 0.9kg of daily BW gain. Hip height, chest depth, and BW were obtained monthly; BCS was recorded at ca. 14 mo of age. At ca. 12 mo of age, two blood samples for each heifer were collected (10 d apart) by jugular vein puncture for progesterone assay. Heifers were considered cycling if progesterone concentrations were ≥1 ng/mL in either of the two serum samples. Heifers were bred artificially (AI) on a synchronized estrus starting at 14 mo of age, and pregnancy status was determined ultrasonically 60 d after breeding. The BSH and H had similar (P>0.05) weights and hip heights; whereas JH were lighter and shorter (P<0.05). No differences (P>0.05) occurred for depth of chest and mean BCS. Estrus occurrence by 12 mo of age was greater (P<0.05) for JH (90%) than for BSH (75%) and lowest ( P <0.05) for H (47%). Pregnancy rates did not differ (BSH = 96%, JH=87%, H=77%). These data suggest that genetic effects of crossbreeding influence early growth and cyclicity at 12 mo of age for replacement dairy heifers. Forage-based development of dairy heifers may be a suitable option to concentrate feeding for dairy producers in Arkansas and the Southern Region.