Effects of type of glucogenic feed additive on reproductive performance of young postpartum range cows

Abstract

Objective

This study evaluated the effects of the in- clusion of either monensin (Rumensin 90, Elanco Animal Health) or propionate salt (NutroCal 100, Kemin Indus- tries) in protein supplements on BW change, BCS, en- ergy metabolism, reproduction, milk production, and calf weaning BW in young 2- and 3-yr-old postpartum range cows.

Materials and Methods

In a 3-yr study at the Gud- mundsen Sandhills Laboratory near Whitman, Nebraska, March-calving, young range cows (n = 189) were individu- ally supplemented 908 g/d with a 30% CP supplement with the addition of either (1) 160 mg·cow⁻¹·d⁻¹ monensin (MON) or (2) 40 g·cow⁻¹·d⁻¹ propionate salt (CAP). Sup- plementation started approximately 10 d after parturition and continued for an average of 70 d postpartum. Cow BW and BCS data were collected weekly. Weekly blood samples were taken beginning 45 d postpartum. A com- pletely randomized design was used and data were ana- lyzed using MIXED procedure (SAS Institute Inc., Cary, NC). All binomial data were analyzed using PROC GLIM- MIX. Cow served as experimental unit, with supplemental treatment, year, and cow age set as fixed effects.

Results and Discussion

Cow BW (P ≥ 0.19) and BCS (P ≥ 0.11) were not affected by postpartum supple- mentation during the study. However, BW change from calving to breeding was influenced (P = 0.04; −7 vs. −2 kg for CAP and MON; respectively) by supplementation, with cows receiving CAP losing greater BW. Calf BW at birth, weaning, or 205 d were not affected (P ≥ 0.68) by the postpartum supplementation strategy. Cows fed CAP had lower (P = 0.01; Table 4) circulating blood serum BHB concentrations than their counterparts. Cows receiving CAP supplementation had an increase (P = 0.04; 89% vs. 80% for CAP and MON; respectively) in overall pregnancy rate.

Implications and Applications

This study implies that feeding young postpartum cows additional glucogenic precursors in the form of propionate salts increased re- productive efficiency without affecting BW or BCS. This increase in reproductive performance may have been en- hanced by improved dietary energy utilization as seen by decreased blood serum BHB concentration. In addition, economic efficiency was increased due to the increased re- productive performance and timing of when cows were bred.