Near-Infrared Spectroscopy Integration in the Regular Monitorization of Pasture Nutritional Properties and Gas Production

Abstract

Nutrition has a very significant impact on animal performance. Given the limited agricultural area of the Azores, the optimization of forage quality, quantity, and availability is key for the local livestock industry’s ability to respond to the challenges of an increasingly globalized market. This work’s goal was to evaluate the use of near-infrared spectroscopy to determine several chemical and biological parameters of pastures under the agroclimatic conditions of the Azores, and to compare its predicative ability when applied to dry homogeneous samples and to fresh inhomogeneous samples, so that we can assess the feasibility of using it to predict new samples on-site in the future. Infrared spectra of 400 fresh and dried grass samples were collected and associated with the corresponding reference values, determined through conventional methods. Mathematical models were created that established relationships between these readings and the values of the properties of interest. Predictive capacity proved especially good for crude protein, neutral detergent fiber, acid detergent fiber, ash, and dry matter, but insufficient for the biological parameters included in the study related to gas production. Near-infrared spectroscopy proved to be useable on-site as a quick, non-destructive, and cost-effective technique to monitor forage quality on a regular basis, enabling forage management and diet design optimizations.

Seasonal Effect of Grass Nutritional Value on Enteric Methane Emission in Islands Pasture Systems

“…The agricultural area of the Azores is divided into four categories: arable land, without irrigation; grasslands; agricultural land, with natural vegetation areas; and natural grasslands, as presented in Figure 1. Permanent grasslands represent 43% of the region's land area [13], mostly located at medium and high altitudes, with sub-spontaneous or even semi-natural grasslands, where grazing is less intensive [14]. Most of the arable land and improved pastures are in low-altitude and medium-altitude areas.…”

“…A total of 300 pasture samples representative of the Azorean grasslands were collected between autumn 2020 and summer 2021. The samples were collected according to the methodology presented by [14]. Briefly, 25 samples were taken from three different altitudes, low (below 200 m), medium (between 200 and 400 m), and high (above 400 m) each season (25 samples × 3 altitudes × 4 seasons), to ensure the variability and heterogeneity of the pastures ingested by the cattle.…”

“…high altitudes, with sub-spontaneous or even semi-natural grasslands, where grazing is less intensive [14]. Most of the arable land and improved pastures are in low-altitude and medium-altitude areas.…”

“…After being collected, the samples were dried at 65 • C in an oven with forced air circulation until a constant weight was reached [14,17]. They were then cut into small pieces and ground with a Retsch mill (GmbH, Hann, Germany), sieved using a 1 mm sieve, and stored in tightly closed bags.…”

“…The biological parameters, more specifically, in vitro dry matter digestibility and organic matter digestibility, were determined using the method described by [20], with modifications outlined in [21]. The rumen liquid used in the determinations was collected from a local bovine slaughterhouse, following the procedure described in [14,22]. The conditions for obtaining rumen liquid were detailed in [22], with rumen samples collected from five healthy dairy cattle (Holstein-Friesian) that had been fed ryegrass.…”