Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems

Abstract

Climate change is a reality and global surface temperature is projected to rise substantially in the next 80 years. Agriculture practices will have to adapt to climate change, and also help to mitigate this effect using, among other strategies, forest conservation and management. Silvopastoral systems have been adopted in tropical climate livestock areas but their benefits on thermal comfort and reproductive performance of beef cows are not completely known. Therefore, our aims were to compare the microclimate of silvopastoral and intensive rotational unshaded grazing systems in different months and to evaluate physiological variables (Exp. 1 and 2), metabolism, and in vitro embryo production (Exp. 2) in crossbred beef females. Our hypothesis is that the silvopastoral system can improve the thermal comfort of beef heifers and cows and, consequently, also improve dry matter intake, body weight gain, and in vitro embryo production when compared to the unshaded rotational grazing system. In Exp 1, the silvopastoral system decreased body temperature and increased welfare and performance of heifers. In Exp. 2, the silvopastoral system enhanced the body weight but did not affect metabolism and the general reproductive performance, but increased the recovery rate of oocytes in primiparous cows.

Figure 1

Hypothetical model. Natural shade in pasture areas improves the thermal comfort of beef heifers and beef cows due to both reduced black globe humidity index (BGHI) and heat load index (HLI). It consequently determines reduction in heart rate, respiratory rate, rectal and body surface temperatures, cortisol, heat shock proteins expression (HSP90AA) and increases dry matter intake (DMI), body weight, and in vitro embryo recovery. BHBA β-hydroxybutyrate, NEFAs non-esterified fatty acids.

Figure 2

Microclimate characterization of pasture systems in silvopastoral (SP) or intensive rotational (IR) grazing systems according to black globe humidity index (a) and heat load index (b) registered from December 2015 to May 2016. There was an interaction between system and month on black globe humidity index and heat load index. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,bDifferent lowercase letters indicate a significant difference between months.

Figure 3

Rectal (a) and back line (b) temperatures of heifers kept in the silvopastoral (SP) or intensive rotational (IR) grazing systems. For rectal temperature, main effects were observed. For backline temperature, an interaction between system and month was observed. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 4

Serum cortisol concentration of heifers raised on silvopastoral (SP) or intensive rotational (IR) systems from December to April. There was an interaction between system and month. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 5

Body weight (a) and body condition score (b) evolution of heifers kept in the silvopastoral (SP) or intensive rotational (IR) grazing systems from December 2015 to May 2016. There was a significant effect of system and month on body weight and body condition score. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 6

Microclimatic characterization of pasture systems in silvopastoral (SP) or intensive rotational (IR) grazing systems according to black globe humidity index (a) and heat load index (b) recorded from January to May 2017. Main effects were observed for black globe humidity index, while an interaction was observed for heat load index. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 7

Rectal (a), trunk (b), and back line (c) temperatures of cows kept in the silvopastoral (SP) or intensive rotational (IR) grazing systems from January to May 2017. An effect of month was observed for rectal temperature. Trunk and back line temperatures were affected by both main effects. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 8

Serum cortisol concentration of heifers kept in the silvopastoral (SP) or intensive rotational (IR) grazing systems from January to May 2017. Cortisol levels were influenced by the system (P = 0.08) and the month (P = 0.02). ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 9

Body weight (a) and body condition score (b) of females kept in the silvopastoral (SP) or intensive rotational grazing (IR) systems from January to May 2017. Body weight was influenced by system, and body condition score by an interaction between system and month. ^A,BDifferent capital letters indicate a significant difference between systems. ^a,b,cDifferent lowercase letters indicate a significant difference between months.

Figure 10

Serum concentration of progesterone (a), glucose (b), non-esterified fatty acids (c), and β-hydroxybutyrate (d) of beef cows kept in the silvopastoral (SP) or intensive rotational (IR) grazing systems from January to May 2017. All variables were affected by month. ^a,b,cDifferent lowercase letters indicate a significant difference between months.