This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.
Effect of initial time of forage supply on growth and rumen development in preweaning calves
To determine the effects of the initial timing of forage supply on growth, ruminal fermentation parameters and rumen development in preweaning calves, eighteen 42±3 kg 7-day-old Holstein calves were randomly divided into three treatment groups. The dietary treatments were: 1) milk and commercial starter diet (MS) control; 2) milk and starter diet supplemented with oat hay at two weeks (MSO2); 3) milk and starter diet supplemented with oat hay at six weeks (MSO6). Starter feed and oat hay were provided ad libitum, and 2L milk was provided twice daily. Samples were collected at 64 days age. Supplementing with hay increased the dry matter intake (DMI) (P<0.05). The height, body length, heart girth, and cannon bone circumference were similar among the three treatments (P>0.05). Compared with the MS and MSO2 groups, serum glucose (P=0.07) and β-hydroxybutyric acid (BHBA) concentrations (P<0.05) were lower in the MSO6 group. Rumination time was longer, and time spent on nonnutritive oral behavior (licking surfaces, tongue rolling, wood shaving consumption, etc.) was lower for hay supplemented calves relative to the control (P<0.05). Although ruminal pH of hay supplemented calves were significantly higher than that of the control, total rumen fluid VFA concentrations were not significantly different among treatments. MSO2 group calves had a smaller proportion of empty weight to slaughter weight (P<0.05) and a larger total digestive tract weight (P<0.05); the empty gastrointestinal tract weights were similar among the three treatments, suggesting that MS02 calf weight gain may have resulted from intestinal chyme accumulation. Compared with the control, hay supplemented calves had reduced rumen papilla width and epithelium thickness (P<0.05), and no discernable plaque formation. Hay supplementation in the diet of preweaning calves improved the overall DMI, improved rumination, reduced nonnutritive oral behaviors, improved rumen pH, and ensured healthy rumen development; furthermore, productivity and rumen development were better in calves supplemented with hay from the second week.
AN16667 Accepted 20 June 2017
© CSIRO 2017