Average daily gain among calves fed a high plane of milk replacer during the pre-weaning period is not associated with improved reproductive efficiency or lactational performance in Holstein heifers
The objective was to determine if increased ADG while on a high plane of nutrition during the pre-weaning period is associated with improved reproductive efficiency as a heifer and improved reproductive efficiency or lactational performance as a primiparous cow. Seventy-two Holstein calves from a single herd in western Texas (2 ± 1 d old) were fed a high plane of nutrition (28/20 milk replacer fed at 756 g/d DM and 1,010 g/d DM for the first wk and wks 2-6, respectively, with ad-libitum access to calf starter grain during the pre-weaning period. Weaning was initiated at wk 7 with the removal of PM milk replacer feeding and was completed when starter intake was 800 g/d DM after d 53. Daily milk replacer and starter intakes were recorded, and ADG was calculated for the pre-weaning period (wks 1-7). All calves were returned to the dairy of origination 3 months after weaning and were managed according to their standard procedures. Reproductive efficiency as a heifer, as well as first lactation reproductive efficiency and milk production were collected from DairyComp305 records. All descriptive data will be reported as [0, 25, 50, 75, and 100 percentile]. The pre-weaning ADG was [0.144, 0.491, 0.560, 0.636, and 0.827 kg / d]. There was no relationship between pre-weaning ADG and age at first calving [647, 672, 685, 721, and 776 d; P = 0.14]. Reproductive performance as a primiparous cow was not affected by pre-weaning ADG, as no relationship was observed for average days open [61, 83, 104, 173, 298 d; P = 0.14. In addition, there was no relationship between pre-weaning ADG and first lactation production metrics of peak milk [28.2, 35.9, 39.1, 41.8, and 50 kg; P = 0.15] and estimated 305 d mature equivalent [8191, 10827, 11914, 13407, 16073 kg; P = 0.32]. Additional research is needed to evaluate the relationship between post-weaning heifer nutrition and health statuses and subsequent reproductive and lactational performance.
Keywords: calf, lactation performance, plane of nutrition