Colostrum is essential to neonatal survival and future performance, providing energy and immunity in early life. Late gestation nutrition has been shown to influence colostrum production and immunoglobulin G yield (IgGY). This study aims to determine the key drivers of colostrum production, specifically the relationship with dry matter intake (DMI), crude protein intake (CPI), and body reserve mobilization during the final 6 weeks of gestation. Data from 7 late pregnancy nutrition studies carried out over 12 years using twin-bearing ewes were merged into a single data set. All studies recorded ewe colostrum production and IgGY at one, 10 and 18 h postpartum. Regression coefficients were estimated using PROC MIXED (SAS v9.4). The model included the fixed effects of ewe, year, ewe breed (Belclare, Leicester and Suffolk crosses) and time point as well as the continuous variables of gestation length, maternal age, average lamb birth weight (BW), live weight change (LWC) and body condition score change (BCSC) during late gestation. Colostrum volume changed by 0.02 l for every 10 g change in CPI (P < 0.01), and 0.02 l for every 100 g change in DMI (P < 0.01). Body reserve mobilization (LWC and BCSC) did not influence colostrum volume (P > 0.10). Breed (P < 0.01), time point (P < 0.01), breed by time point interaction (P < 0.01) and maternal age (P < 0.05) had significant effects on the effect of CPI and DMI on the volume of colostrum produced by the ewe. The IgGY was also driven by CPI and DMI (P < 0.05). Each 10g change in CPI gave a 0.50 g change in IgGY (P < 0.05) and there was 0.80 g change in IgGY for each 100 g change in DMI (P < 0.01). Breed did not influence IgGY (P > 0.10) despite a breed by time point interaction (P < 0.01). Gestation length did not affect colostrum volume or IgGY (P > 0.10). These results indicate that intake as opposed to body reserve mobilization is the major driver of colostrum production by the ewe.