Management Strategies for Lamb Production on Pasture-Based Systems in Subtropical Regions: A Review

Abstract

Sheep production on pasture plays an important role in subtropical climates around the world, with great economic and environmental relevance to those regions. However, this production is much lower than its true potential in subtropical regions, largely due to lack of knowledge of how to feed grazing lambs, and mitigate gastrointestinal parasite infections. Due to weather instability and the high growth rate of tropical grasses, it is difficult to adjust the quality and quantity of feed consumed by lambs. In addition, due to warm, wet weather during spring, summer, and autumn, gastrointestinal parasite infection can be intense on subtropical pastures. Thus, the objective of this paper is to summarize 17 years of research in southern regions of Brazil testing alternative management for sheep farmers under these challenging conditions. Our review indicates that ewes play important roles raising their lambs. Besides protecting and providing milk, they leave a better pasture structure for lamb nutrition. The use of creep feeding and creep grazing are additional alternatives to improve lamb growth. However, feeding supplementation with concentrate can deteriorate pasture quality at the end of the summer–autumn season. Gastrointestinal parasitic infections can be reduced with improved lamb nutrition, although L3 larvae of Haemonchus contortus can be present at various pasture heights. This indicates that it is difficult to control L3 ingestion solely by manipulating grazing heights. We summarize important technologies for raising lambs on pasture-based systems to make the best of high herbage growth and minimize intense parasitic infections common in subtropical regions. We discuss research results in light of the latest studies from other ecoregions and climates, although there is a lack of similar research in subtropical regions of the world.

The effects of protein supplementation and pasture maintenance on the growth, parasite burden, and economic return of pasture-raised lambs

“…Moreover, supplementation feeding rate has also shown to affect lamb growth as lambs on grass pasture provided supplemental protein (190 g/kg DM) at 2% BW had greater BW gains when compared with lambs supplemented at 1% BW ( Crawford et al, 2020 ). Although providing additional protein in the diet allows for lambs to increase BW gains on pasture, as lambs consume more supplemental feed the less forage they will consume ( Newton and Young, 1974 ; Dove, 2002 ; Poli et al, 2020 ). When less forage is consumed, pasture utilization, forage quality, and the proportion of parasitic nematodes consumed decreases as a greater amount of residual forage and parasitic larvae remain on pasture post grazing ( Dove, 2002 ).…”

“…In intensive grazing management systems, grazing is considered a high-risk practice when factors of forage quality and pasture parasite burden are unknown ( Poli et al, 2020 ). Providing lambs grazing on pastures of poor quality with supplemental plant-derived protein primarily using soybean meal has shown to increase lamb body weight (BW) gain ( Wallace et al, 1995 ; Wallace et al, 1996 ; Kahn et al, 2000 ; Felix et al, 2012 ).…”

Influence of tropical upright pasture structural and chemical characteristics on lamb grazing time

“…This is one of the reasons why they have small mouths with the ability to select parts of a plant, generally resulting in a nutritional quality superior to the average offered in the pasture as a whole [ 19 ]. Therefore, to generate sustainable sheep production systems in tropical and subtropical environments, it is important to understand the factors that affect grazing lamb ingestive behavior [ 20 , 21 ]. There is a lack of studies that show how lambs, which are highly selective, have high feed quality requirements compared to adults, and possess small mouths, graze upright tropical pastures with variable structure and nutritive value.…”

Weaning and concentrate supplementation on the characteristics of carcass cuts and longissimus muscle of Suffolk lambs finished on pasture

“…In addition, concentrate supplementation may be necessary to meet the nutritional requirements of breeds specialized for meat production, such as Suffolk, allowing these animals to express their growth potential under grazing conditions. Studies performed in the Brazilian subtropical region showed that Suffolk lambs finished at 32-37 kg of body weight (BW) on Tifton 85 pasture presented an average daily gain of 135 -280 g day -1 in systems without weaning; 50 -110 g day -1 in systems with weaning and without supplementation; and around 150 g day -1 when they received concentrate supplementation post-weaning (Silva et al, 2014;Poli et al, 2020). In systems without weaning, the proteinenergy supplementation offered in creep feeding has been widely used to improve lambs' growth, resulting in…”