Abstract
Inadequate estimates of fiber and dry matter intake of sheep raised in tropical conditions may explain part of the inefficiency of those production systems. Therefore, we aimed to estimate dry matter intake (DMI) and neutral detergent fiber intake (NDFI) of hair sheep raised under tropical conditions. A meta-analysis of 61 independent performance experiments, comprising a total of 413 experimental units (treatment means or animals), was performed. Trials were conducted in tropical conditions, using hair sheep in growing and finishing phases and endowed with the following information: neutral detergent fiber (NDF) in diet, initial and final body weight (BW), average daily gain (ADG), DMI and NDFI of treatment means (51 studies) or individual data (10 studies). Data on organic matter and NDF digestibilities were collected to estimate D-value (Dv) and B-value (Bv) (20 and 33 studies, respectively). The equations obtained were: DMI (g/kg BW) as a function of Dv (g/kg DM) revealed a quadratic relationship, whose point of maximum DMI (38.69 g/kg BW) was obtained at 634.1 g/kg DM Dv. On the other hand, DMI decreased linearly as Bv (g/kg DM) increased. In conclusion, equations to predict DMI from BW and ADG as well to predict NDFI from dietary NDF were fitted with great accuracy and are recommended for hair sheep raised in tropical regions. DMI values were, in general, greater than those reported by the NRC, AFRC and INRA systems, which may be a reflection of the sheep breeds used in this study. Using Dv and Bv concepts was satisfactory to describe an integrated mechanism between metabolic and bulking regulation of DMI in sheep.
Highlights
Feed intake is one of the most important variables for nutrition and metabolism, since it defines the quantity of ingested nutrients, determining the animal’s response [1]
All studies were conducted under tropical conditions, were published from 2002 to 2019 in English or Portuguese using hair sheep in growing and finishing phases, and endowed with the following quantitative information: neutral detergent fiber (NDF) in diet, initial and final body weight (BW), average daily gain (ADG), dry matter intake (DMI) and neutral detergent fiber intake (NDFI) of treatment means (51 studies) or individual data (10 studies)
Dry matter intake estimates were expressed in g/day and g/kg BW
Summary
Feed intake is one of the most important variables for nutrition and metabolism, since it defines the quantity of ingested nutrients, determining the animal’s response [1]. DMI is supposed to be regulated by metabolic feedbacks when diets with greater digestibilities are fed to ruminants [3]. Such a concept does not assume that both approaches could be integrated to modulate DMI [4,5,6,7]. In this sense, a study on the voluntary intake regulation of cattle, considering dietary total tract digestibility and bulkiness, concluded that physical constraints and metabolic feedbacks work together in the regulation of voluntary intake [8]. The integration of these characteristics is fundamental in mathematical models aiming to estimate animals’ feed intake
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