A meta-analysis and meta-regression of the effect of forage particle size, level, source, and preservation method on feed intake, nutrient digestibility, and performance in dairy cows

Abstract

A meta-analysis of the effect of forage particle size (FPS) on nutrient intake, digestibility, and milk production of dairy cattle was conducted using published data from the literature (1998-2014). Meta-regression was used to evaluate the effect of forage level, source, and preservation method on heterogeneity of the results for FPS. A total of 46 papers and 28 to 91 trials (each trial consisting of 2 treatment means) that reported changes in FPS in the diet of dairy cattle were identified. Estimated effect sizes of FPS were calculated on nutrient intake, nutrient digestibility, and milk production and composition. Intakes of dry matter and neutral detergent fiber increased with decreasing FPS (0.527 and 0.166kg/d, respectively) but neutral detergent fiber digestibility decreased (0.6%) with decreasing FPS. Heterogeneity (amount of variation among studies) was significant for all intake and digestibility parameters and the improvement in feed intake only occurred with decreasing FPS for diets containing a high level of forage (>50%). Also, the improvement in dry matter intake due to lowering FPS occurred for diets containing silage but not hay. Digestibility of dry matter increased with decreasing FPS when the forage source of the diet was not corn. Milk production consistently increased (0.541kg/d; heterogeneity=19%) and milk protein production increased (0.02kg/d) as FPS decreased, but FCM was not affected by FPS. Likewise, milk fat percentage decreased (0.058%) with decreasing FPS. The heterogeneity of milk parameters (including fat-corrected milk, milk fat, and milk protein), other than milk production, was also significant. Decreasing FPS in high-forage diets (>50%) increased milk protein production by 0.027%. Decreasing FPS increased milk protein content in corn forage-based diets and milk fat and protein percentage in hay-based diets. In conclusion, FPS has the potential to affect feed intake and milk production of dairy cows, but its effects depend upon source, level, and the method of preservation of forages in the diet.

Effects of forage source and particle size on feed sorting, milk production and nutrient digestibility in lactating dairy cows

“…Similarly, a reduction in FPS has been reported to increase milk yield (Kmicikewycz & Heinrichs, ) or to have no effect on milk yield (Bhandari, Ominski, Wittenberg, & Plaizier, ; Jarrett et al., ; Maulfair & Heinrichs, ). The inconsistency among these studies may be due to differences in the source, level, and method of preservation (i.e., hay vs. silage) of the forage in the diets (Nasrollahi, Imani, & Zebeli, ). Moreover, most of these studies estimated the effect of particle size of silage in diet rather than hay.…”

Meta-analysis of corn plants, green fodder (ensilage), and silages of different types of maize hybrids used in experimental conditions in Brazil

“…In the international literature, several metaanalysis studies have been conducted on corn silage (Ferraretto & Shaver, 2015;Hollmann, Allen, & Beede, 2011;Kleinschmit & Kung, 2006;Phuong, Friggens, Boer, & Schmidely, 2013;Nasrollahi, Imani, & Zebeli, 2015) to determine the factors that interfere with the composition and quality of the silage produced. However, much of the information contained in these previous publications cannot be extrapolated to the Brazilian conditions because of vast differences, for example, in weather, soil fertility, and the characteristics of maize hybrids.…”

Strategies to improve kernel processing and dairy cow performance in whole-plant corn silage based on vitreous endosperm hybrid

“…however, greater protein content has been reported for cows fed finer particles (Nasrollahi et al, 2015). The lactose content was lower for SP18 and milk yield tended to be reduced in comparison with SP12; thereby the lactose excretion per day was also reduced.…”

“…The milk fat content did not change within SPFH treatments (SP6, SP12, and SP18) at different TLOCs. The meta-analysis conducted by Nasrollahi et al (2015) with purpose to evaluate the impact of TMR MPL in the performance of dairy cows revealed a reduction of 0.06 percentage units in fat content when cows were fed finer particles. A similar ruminal VFA profile for WPCS with varying TLOCs have been reported Onetti et al, 2003) and may explain the lack of effect of TLOC on milk fat content .…”

“…reported no effect of kernel processing and TLOC on DMI. However, Nasrollahi et al (2015) observed through a meta-analysis of 46 studies that the decrease in MPL enhanced DMI and this effect was pronounced in diets containing high levels of forage (>50% of DM). Summarizing studies conducted mainly with WPCS as the forage source revealed that when TLOC was reduced from 23.3 ± 8.22-mm to 10.2 ± 6.78-mm the DMI was increased by 0.6 kg ranging from -1.1 kg to + 2.3 kg/d (Zebeli and Humer, 2017).…”