Meta-analysis of concentrate supplement effects on voluntary intake in high and low quality pastures

Abstract Text:

The objective was to evaluate the effects of level of supplementation and forage quality on forage and total dry matter intake (DMI). Individually intakes from 1153 beef animals reported in forty five articles published from 1974 to 2011 were compiled. Forage was classified as high quality (more than 9% of CP) and low (less than 9% of CP). A meta-analysis approach was used according to St. Pierre (2001). For high quality pastures forage DMI decreased linearly as the supplementation level increased (-0.651% BW for energy 1% BW supplementation level) (P<0.05). However, total DMI increased linearly (P<0.05) as supplementation level increased (0.348% BW for energy 1% BW supplementation). On the other hand, for low quality pastures forage DMI was increased up to 0.25% BW supplementation level and it was decreased (P<0.05) with high levels of supplementation. Total DMI was increased linearly (P<0.05). The positive effect of supplementation fed up to 0.25% BW on low quality forage intake is due to the high CP content of these supplement supplying RDP to microbes. The negative effect of supplementation on forage DMI occurs when doses are greater than 0.25% BW, and energy is included in the supplement.

Table 1. Best-fit equations for simple regression of response to concentrate supplementation on voluntary intake in different pastures quality

Pasture quality	Variable	Intercept	SE	Slope						r2	RMSE
				β1	SE	β2	SE	β3	SE
High	TI	2.35	0.15	0.348	0.242	-	-	-	-	0.66	0.462
	FI	2.35	0.15	-0.651	0.242	-	-	-	-	0.35	0.465
Low	TI	1.70	0.13	0.900	0.122	-	-	-	-	0.65	0.338
	FI	1.63	0.14	1.732	0.789	-5.281	2.670	3.384	2.126	0.30	0.372

FI= forage intake, TI= total intake, SE= standard error, RMSE= root means square error.

Keywords: pasture, protein, supplementation