Table 3 Overview of included articles/studies concerning the effects of supplementary feeding in semi-natural pastures
Article | Setup (relevant for this review) | Q | Results (relevant for this review) | Risk of bias |
|---|---|---|---|---|
Avondo 2002 [70] | Eight-year study with data from nine feeding trials with data on the effect of in-house (in pen) supplementation on forage intake of sheep grazing semi-extensive pasture systems on Sicily, Italy. There are no data on number of pastures, just that there were 670 forage intake data from 210 animals | 3 | The provision of a supplement caused a reduction in pasture intake in pastures. Statistically significant (2) model improvements by including crude protein (CP) of supplement as a predictor, not dry matter (DM) of supplement. Separate results for pastures with less than or equal to, or more than, 16% CP content | High |
Bowman 1999* [71] | Experiment 2: Three-month study on the effect of two supplementary feeding methods (same supplement formulation) on cattle forage intake on native range pastures, among other variables, in Montana, USA | 3 | Both feeding methods resulted in statistically significantly (2) higher forage intake compared to the control group. There was no statistically significant (2) difference between the feeding methods | Medium |
Clariget 2016* [72] | One-year study of the effects of different types/combinations of supplementation on dry matter intake (DMI) of forage by cattle grazing a natural pasture in Cerro Largo, Uruguay | 3 | All treatments resulted in lower DMI compared to the non-supplemented control, with the lowest DMI for cattle fed crude glycerin, which was the only DMI estimate statistically significantly (2) lower than the control group | High |
Da Ronch 2005 [50] | Two-year study on the effects of concentrate supplementation on plant species richness in three pairs of near-alpine (plateau) pastures in Vicenza, Italy, grazed by cattle | 1 | Data indicate (3) that on average the pastures where cattle were fed supplements, the species richness was higher. However, that difference seems to be driven by a big difference in species richness between the third pair of pastures | High |
Guerrero 2018* [73] | Three-month study on the effect of supplementation with either sugarcane and urea or sugarcane only on sheep forage intake on natural pastures in Huambo, Angola | 3 | Non-supplemented sheep consumed statistically significantly (2) more forage than supplemented sheep. Among the supplemented sheep, the group supplemented with sugarcane and urea consumed statistically significantly (2) less forage than the group supplemented with sugarcane only | High |
Mosley 2017* [51] | Two-year study of the effect of barley-based commercial sheep pellet supplement, compared to salt supplement only, on forage intake by sheep, plant community composition and plant yield in a highland rangeland in Montana, USA. Sheep were handfed in paddock. Data from two periods in summer | 1 | There were no statistically significant (2) differences in the plant community in the first period. In the second period, there were statistically significantly (2) more perennial graminoids and less other forbs in the plant community where sheep were supplemented | Medium |
2 | The only statistically significant (2) difference in plant yield was that there were less other forbs where sheep were supplemented in the second year (measured separately for perennial graminoids, annual grasses and other forbs) | Medium | ||
3 | Supplemented sheep statistically significantly (2) preferred annual grasses and avoided perennial graminoids in the first period, but avoided annual grasses in the second period, when non-supplemented sheep avoided perennial graminoids (no between-group test). There were no statistically significant (2) differences in dry matter intake in any period | Medium | ||
Niemelä 2008 [52] | One-year study on the effect of supplementation of cattle (creep feeding of either flattened oat as the supplement or a commercial concentrate) on the nutritional status of the vegetation of four semi-natural coastal meadows along the Bothnian Bay, Finland | 2 | Data indicate (3) that the four meadows, two with supplementation and two without, differed in their vegetation nutrient status (P, K, Ca, Mg, S, Na, Fe, Zn, Cu, Mn). They also belonged to different farms, and hence locations. For details on the differences, see Table 2 in article | High |
Ormaechea 2021 [74] | Two-year study of the effects of supplement blocks on sheep use of two steppe pasture paddocks in Santa Cruz, Argentina. GPS tracking was used to estimate animal movements before and after supplement blocks were placed in the two pastures | 3 | Sheep spent statistically significantly (2) more time in the area around the target sites and used a statistically significantly (2) larger proportion of the paddock area when supplement blocks were present | High |
Souza 2023 [75] | Three-month study on the effect of supplementation on sheep movement on Caatinga rangeland in Pernambuco, Brazil. Nutrient intake also studied but interpreted as total intake (including supplement). The study was conducted in three periods, from rainy to drought period | 3 | Supplemented animals showed statistically significantly (2) lower concentration in their movement (lower Kernel density) compared to non-supplemented animals, especially in the rainy period | High |
Sowell 2003* [76] | Two-year study on the effect of two supplementary feeding methods (same supplement formulation) on cattle forage intake on six native range pastures, among other variables, in Montana, USA | 3 | Supplemented cattle had statistically significantly (2) higher forage dry matter intake than non-supplemented cattle, both concerning dry matter intake and dry matter intake per kg body weight, in both years. A restricted supplement method resulted in the highest intake values | Medium |
Yang 2020 [53] | Four-year study on the effect of supplementation on nutrient cycling, focusing on carbon (C), in six alpine pastures grazed by yak in Gansu province, China. Yaks were fed oat hay in overnight shelters | 2 | There were statistically significantly (2) higher litter C return and forage biomass in the grazing system with oat hay supplementation | Medium |
3 | Conclusions from the structural equation model states (4) that yaks supplemented with oats hay increased the C return from litter and dung, thereby enhancing forage biomass in the next year | Medium | ||
Yang 2021 [54] | Four-year study on the effect of supplementation on nutrient cycling, focusing on nitrogen (N), in six alpine pastures grazed by yak in Gansu province, China. Yaks were fed oat hay in overnight shelters | 2 | There were statistically significantly (2) higher litter N return and forage biomass in the grazing system with oat hay supplementation, but there was no statistically significant (2) effect on soil N stock | Medium |
3 | Authors conclude that soil N stock was relatively insensitive to grazing intensity influenced by supplementation with hay | Medium |