Management of the rumen in cattle and sheep is crucial for achieving the required growth rates with multiple studies linking good rumen development to higher average daily liveweight gains. The focus in terms of management should therefore not only be on protecting rumen integrity during periods of elevated stress such as during weaning, but also on maintaining it throughout the fattening period. This is key if livestock are to grow at planned rates to reach target slaughter weights. Recently, Caitlyn De Vos, Ruminant Development Manager at Vitam International, worked with her team on a trial looking at the rumen of fattening lambs in a feedlot system, she explains the findings.
Ruminant Development Manager
Vitam International
The health and performance of sheep, like dairy cows and beef cattle, heavily depends on the rumen’s ability to facilitate digestion and absorption, as well as provide a barrier against the transmission of pathogens and toxins.
Rumen microbes break down dietary polysaccharides into volatile fatty acids (VFAs); most importantly propionate, acetate, and butyrate. Between 50 and 85% of VFAs produced in the rumen are absorbed in that chamber of the stomach (Aschenbach et al., 2011) and this process relies on having well developed rumen papillae to maximize the surface area.
The absorption of VFAs impacts lamb growth because they are responsible for up to 75% of metabolizable energy in ruminants (Bergman, 1990). This means that having well developed rumen papillae is essential for lambs to have sufficient energy to fatten as well as grow in frame and stay healthy.
However, there is a fine line to tread between providing a diet that generates sufficient VFAs for growth and maintaining rumen wall integrity. VFAs are weak acids which means that they dissociate in the rumen and release a proton. This decreases the ruminal pH and results in ruminal acidosis which damages the ruminal epithelium and impacts the rumen microbes, ultimately reducing feed intakes and so reducing the potential for VFA- and so energy- production (Penner, 2014).
Small ruminants and lambs are more sensitive to stress, which is why the acidosis risk is high in feedlot lambs due to a combination of environmental and dietary risk factors.
Fattening lambs are typically fed with high fiber and dam milk, until they are moved to finishing feedlot pens, where they will receive a high starch, low- fiber diet. The stresses of weaning, transport and diet transition during this period increase the risk of acidosis, which can result in decreased growth and feed efficiency, and ultimately production margins.
RUMEN ACIDOSIS
As ruminants, sheep have evolved to eat diets that are forage based. The inclusion of cereal in diets is necessary for feedlot lambs to grow at the required rate, but the high levels in their rations can result in acidosis. The signs of acidosis can vary from subtle drops in performance to more significant rumen inflammation caused by the acidic environment which can result in diarrhea, dehydration, and sometimes even death.
Lallemand Animal Nutrition’s rumen specific live yeast, LEVUCELL SC, can support the feeding of a high energy diet while minimizing the risk to rumen. The yeast stabilizes rumen pH which protects rumen wall integrity and papillae length through reducing the risk of acidosis and the damage it can inflict on the lamb’s rumen. This allows lambs to cope with a high-starch, low-fiber diet to encourage rapid growth, without compromising the rumen.
LEVUCELL SC FEEDLOT LAMB TRIAL
The feedlot trial took place over a period of 32-46 days in October and November 2022 in Hartbeesfontein in the North West Province of South Africa. It involved 600 Dohne Merino lambs who entered the trial at between 90 and 150 days of age.
The trial split the lambs into a control group of 300 and a treatment group of 300. Both groups were fed a basal feedlot ration, but the treatment group were also given the equivalent of 0.4g/lamb/day of LEVUCELL SC 10 ME Titan in both their grower and finisher feeds.
The lambs were all reared on ad-lib lucerne hay and adaptation TMR before transitioning to a grower feed for 8-30 days (Figure 1).
Both the control and treatment group were split into three pens; one each of small, medium and large lambs with 100 animals in each pen. The trial weighed the lambs at day 0, the day before being transported off site, and at the slaughterhouse the day after transport. Dry matter intake per day was measured through weighing the TMR distributed and any refusals. Individual hot carcass weights were recorded after slaughter and evisceration. The rumens and livers of the slaughtered lambs were also scored and the average daily gain, feed conversion ratio, and return on investment calculated.
LEVUCELL SC IMPROVES RUMEN HEALTH AND LAMB PERFORMANCE
The trial showed that adding LEVUCELL SC to the diet delivered a clear benefit to lamb health and growth. It increased average daily gain by 2% across the recorded period and gave a better feed conversion ratio- 4.8 compared to 5.1- which increased the margin over feed from 8.09 US$ per lamb to 10.35 US$ per lamb. This gave a return on investment of 3:1 with an average feed cost during the trial of 317 US$ per ton.
The increase in margin over feed cost is linked to improved rumen health supporting better nutrient absorption. The rumen scoring at slaughter showed a statistically significant reduction in star scars in the lambs fed LEVUCELL SC compared to the control group (Figure 2), which indicated a reduction in severe acidosis. There was also a numerical reduction in ulcers and hyper-keratinized rumen papillae.
Overall, the rumen observations showed fewer mid or severe rumen scores in the lambs fed LEVUCELL SC compared to those that weren’t (Figure 2).
CONCLUSION
Feedlot lambs face environmental and dietary stresses that can compromise rumen wall integrity and papillae length through an increased risk of rumen acidosis. As a result, lamb health and growth rates can be negatively impacted, resulting in poorer financial performance.
By adding a rumen specific live yeast to stabilize rumen pH, lambs experience less rumen damage associated with acidosis. This in turn has a positive impact on lamb performance through better average daily weight gain and improved feed conversion rates. Better absorption of food nutrients through the rumen also results in a higher return on investment in purchased feed, meaning a better financial margin per lamb.
Using LEVUCELL SC in feedlot lamb diets was shown in this trial to positively impact lamb health and growth leading to greater profitability and performance.
References:
1. Aschenbach J.R., Penner G.B., Stumpff F., Gabel G. Ruminant Nutrition Symposium: Role of fermentation acid absorption in the regulation of ruminal pH. J. Anim. Sci. 2011; 89:1092–1107
2. Bergman, E.N. 1990. Energy contributions of volatile fatty acids from the gastrointestinal tract in various species. Physiol. Rev. 70:567-590.
3. Penner G.B. (2014) Mechanisms of volatile fatty acid absorption and metabolism and maintenance of a stable rumen environment. IFAS Animal Sciences
About Caitlyn de Vos
Caitlyn de Vos has over five years of experience in the animal feed industry, specialising in feed additives. As the Ruminant Development Manager at Vitam International, she oversees technical support for ruminant solutions in the Sub-Saharan African market. de Vos plays a key role in marketing, technical, and R&D projects. She holds a master’s degree in animal nutrition and is passionate about ruminant nutrition, with a particular focus on digestive efficiency, mycotoxin management, and the role of feed additives to optimise the production of nutritious and hygienic animal protein.
Vitam International is a leading provider of feed additives and services in Sub-Saharan Africa. Lallemand Animal Nutrition and Vitam International have established a joint venture to bring Lallemand Animal Nutrition solutions to promote the South-African market.
