Effects of pelleted timothy hay on pair-housed Holstein calf performance

This randomized control trial evaluated the effects of feeding pelleted hay to paired dairy calves on body weight (BW), average daily gain (ADG), calf starter dry matter intake (DMI), and solid feed efficiency (FE) up to one week after weaning (75 d of age; mean ± SD). Holstein heifer calves (n = 32 pairs; 64 calves) were enrolled at pairing (5 ± 3 d of age; referred to hereafter as day 0 of the study) and randomly assigned in blocks of four pairs to a control (CON; no hay) or treatment (HAY; timothy hay). All calves received 7.4 L/d of milk replacer (MR; 22% crude protein [CP], 20% fat) until 56 d, 3.2 L/d from day 57 to 62, and were weaned on day 63. The HAY group had a trough with pellets until day 59, then they were transitioned to long-stem timothy hay until study completion on day 70 (7 d postweaning). Starter and hay intake and refusals were recorded daily. We measured BW twice weekly until 30 d, then weekly, and a final BW was recorded on day 70. We calculated the average pair starter DMI, solid FE, ADG, and BW by period where period 1 = birth to day 26, period 2 = day 27 to 60, period 3 = day 61 to 67, and period 4 = day 68 to day 75 ± 3 d of age. We used mixed linear regression models to assess the impact of HAY, period, and the HAY × period interaction on ADG, BW, solid FE, and starter DMI, adjusting for birthweight, season, serum total protein, and period with period as a repeated measure, calf as the subject and pair nested within block as a random effect. We used Tukey adjustments to correct for multiple mean comparisons. There was no association of HAY with ADG (CON; 0.88 ± 0.03 vs. HAY; 0.88 ± 0.03 kg/d), starter DMI (CON 2.68 ± 0.15 vs. HAY 2.50 ± 0.14 kg/d), or solid FE (CON 0.65 ± 0.07 vs. HAY 0.73 ± 0.07). We suggest that pelleted timothy hay offered to paired calves warrants further research on behavior and health outcomes, and it does not impact calf starter intake, BW, or average daily gains.