Yield, Nutritional Composition, and Digestibility of Conventional and Brown Midrib (BMR) Pearl Millet as Affected by Planting and Harvesting Dates and Interseeded Cowpea

SIMPLE SUMMARY: A major challenge for farming systems is the seasonality of forage production, in particular, the quantity and quality gap that usually occurs during mid to late summer. Pearl millet is a drought-tolerant, warm-season annual crop that adapts well to relatively infertile and acidic soils and can potentially be mixed with summer annual legumes. In this study, we evaluated in field plots the effect of conventional and brown midrib (BMR) pearl millet on yield, nutritional composition, and fiber digestibility when planted at different dates, harvested at different maturity stages, and when mixed with cowpea. We determined the degradability of neutral detergent fiber under in vitro conditions (IVNDFD) using rumen fluid from lactating dairy cows. The results of this study showed that the BMR pearl millet had a consistently higher IVNDFD compared to a conventional genotype. Delaying pearl millet planting had a significant impact on forage yield. Under the conditions of this study, mixing cowpea with pearl millet had little effect on quality but penalized forage yield. ABSTRACT: The objective of this study was to evaluate the yield, nutritional composition, and digestibility of conventional (CON) and brown midrib (BMR) pearl millet (PM) with different establishment dates, maturity at harvest and when mixed with cowpea (CWP). In trial 1, CON and BMR were planted on two different dates. In trial 2, CON and BMR, mixed or not with CWP, were harvested when PM was at the boot or heading stages. In trial 1, dry matter (DM) yield was similar between both PM genotypes but delaying establishment reduced DM yield by 30%. Additionally, BMR had a lower concentration of acid detergent lignin (ADL) and a higher in vitro neutral detergent fiber digestibility (IVNDFD) compared to CON. In Trial 2, the DM yield was 7.3% higher for CON compared to BMR, and PM with the BMR trait had a lower level of ADL and higher IVNDFD compared to CON. Mixing PM with CWP had negligible effects on nutritional composition but reduced DM yield by 8.3%. Results of these studies indicated that fiber from BMR PM is more digestible than CON but, in one of the trials, this occurred at the expense of lower DM yield. Mixing CWP with PM negatively impacted DM yield.