PSIII-5 Metabolic hormones, live weight, grazing behaviour and offspring distance of primiparous beef cows grazing grasslands at two herbage allowances

Abstract

Abstract The objective of this study was to evaluate the effect of herbage allowance (HA; herbage mass in kg DM/ha: stocking rate in kg LW/ha ratio) during gestation and lactation on cow and calf LW, body condition score (BCS), insulin, IGF-1, and leptin concentrations, daily grazing, ruminating and idling proportion cow-calf distance in primiparous beef cows from -10 to 70 days from temporary suckling restriction (nose plates on calves during 12 days=TW; day 0=initiation of TW at 86 ± 10 postpartum) and flushing (2 kg FB/cow/day whole-rice bran for 22 days). Thirty-three cows were allocated to HA treatments during gestation and lactation (-150 to 195 days relative to calving), that annually averaged 2.5 (low HA) and 4 kg DM/kg LW (high HA). Data were analyzed using mixed models with repeated measures and general linear mixed models. Cows LW and BCS did not differ during the -10 to 50 day period but were greater in high HA at the end of the study. Concentrations of IGF-I were greater in high HA (80 vs 70 ± 3 ng/mL), but insulin and leptin did not differ. Daily grazing proportion was lower in high HA (0.64 vs 0.68 ± 0.06; P < 0.05), and the opposite occur with rumination and idling (P < 0.05). Cow-calf distance was greater in low HA cows (0.57 vs 0.75 ± 0.006; P < 0.05) and increased greatly in this group after flushing. Milk yield was greater (3.7 vs 3 ± 0.3; P > 0.05) and calf weight did not differ between treatments from -10 to 35 day and was greater after 45 days in high HA compared to low HA. Thus, increasing HA resulted in greater IGF-1 concentrations and milk yield, and induced changes in grazing and maternal behavior that were associated with increased cow and calf LW and BCS.