Delay implant strategy in calf-fed Holstein steers: growth performance and carcass characteristics

ABSTRACT

The influence of live weight (LW) at first implanting on growth performance and carcass characteristics was evaluated in calf-fed Holstein fed a steam-flaked corn-based diet. Treatments were: (1) control (not implanted); (2) first implanted at 267 kg LW; (3) first implanted at 291 kg LW, and (4) first implanted at 321 kg LW. All implanted cattle were re-implanted on d-112 of trial. Both the initial and final implants contained 120 mg of trenbolone acetate and 24 mg of oestradiol. Compared with non-implanted controls, implanting increased (P < .01) overall dry matter intake (DMI, 5.9%), average daily gain (ADG,16.7%), gain efficiency (ADG:DMI; 9.4%), and estimated dietary net energy for maintenance (NE_m, 8.6%) and gain (NE_g, 9.7%). Increasing LW at first implanting decreased overall DMI (linear effect; P = .01), but did not affect overall ADG (P = .17) or gain efficiency (P = .32). Within the range of 267–321 kg, weight at first implanting did not affect growth-performance or carcass characteristics. Interval growth performance of implanted and non-implanted calves was a predictable function of LW.

KEYWORDS:

• Holstein cattle
• feedlot
• implants
• performance