1- Department of Animal Science, Faculty of Animal Science and Food Technology, Agricultural Sciences and Natural Resources University of Khuzestan
Abstract: (22 Views)
Introduction and Aim: The rumen is one of the key physiological systems adversely affected by heat stress in ruminants. Given that fattening lamb production is a critical and highly sensitive aspect of livestock management, its success largely depends on optimal rumen digestive and fermentative function. Implementing appropriate nutritional strategies during heat stress can enhance the ruminal ecosystem, promoting microbial activity and proliferation. This study aimed to investigate the effects of dietary supplementation with protected methionine and live yeast on ruminal digestive and fermentative activity in heat-stressed lambs.
Materials and Methods: Forty fattening lambs were acclimatized to experimental conditions for two weeks and subsequently randomly assigned to one of four dietary treatments:1- Control: Basal diet (no additives), 2- PM: Basal diet + 4 g protected methionine, 3- LY: Basal diet + 5.5 g Saccharomyces cerevisiae (live yeast), 4- PM+LY: Basal diet + 4 g protected methionine + 5.5 g Saccharomyces cerevisiae. On day 55 and 70 of the experimental period, rumen fluid samples were collected from all lambs per treatment group. Samples from each treatment were pooled to assess the effects on digestive and fermentative activity of wheat straw as a fibrous substrate. The cumulative gas production was measured at 2, 4, 6, 8, 10, 12, 24, 48, 72, and 96 h. The gas production parameters, Organic matter digestibility (OMD), apparent OMD, metabolizable energy (ME), net energy for lactation (NEL), Dry matter intake (DMI), digestible DMI, growth rate, pH, ammonia nitrogen (NH₃-N) concentration, and protozoal population were estimated. Data were analyzed using a completely randomized design via the PROC GLM procedure in SAS (version 9.4). Treatment means were compared using the Duncan test (α = 0.05).
Results: The protected methionine + live yeast (PM+LY) treatment exhibited the highest gas production potential and rate, while the control treatment showed the lowest values. The difference between the PM+LY treatment and all other treatments was significant. Although the PM treatment produced more gas than the control (P<0.05), it produced less gas than the LY treatment and the PM+LY combination (P < 0.05). In the experimental diets, the partitioning factor (PF), microbial biomass production, and microbial biomass production efficiency were significantly higher in additive-containing treatments than in the control (P<0.05). In this regard, the control had the lowest values, and the PM+LY treatment had the highest. However, for PF, microbial biomass production, and microbial biomass production efficiency, no significant differences were observed between the PM treatment and the control. Furthermore, the results showed that truly degraded organic matter (TDOM) was significantly higher in the control than in all other treatments; the control had the highest TDOM, and the PM+LY treatment had the lowest. Among the additive-containing treatments, TDOM also differed significantly from one another (P < 0.05). Dry matter intake (DMI), digestible dry matter intake (DDMI), and estimated growth rate were significantly lowest in the control and highest in the PM+LY treatment. The LY treatment showed higher DMI, DDMI, and growth rate compared to the protected methionine treatment and the control (P < 0.05). Metabolizable energy (ME), net energy for lactation (NEL), apparent organic matter digestibility, organic matter digestibility, and short-chain fatty acids (SCFA) were lowest in the control and highest in the PM treatment; the differences between the PM treatment and both the control and the LY treatment were significant (P < 0.05). The effect of treatments on culture pH was not significant. Ammonia‑nitrogen concentration was higher in additive‑containing treatments than in the control, with the PM+LY treatment having the highest concentration. The results also indicated that the populations of Holotrichs, Entodiniomorphs, cellulolytic protozoa, and total rumen protozoa were lowest in the control and highest in the PM+LY treatment. No significant difference was found between the control and the PM treatment. However, a significant difference existed between the PM treatment and the LY treatment, with the LY treatment having higher populations of Holotrichs, Entodiniomorphs, cellulolytic protozoa, and total rumen protozoa than the PM treatment.
Conclusion: According to the results of the present experiment, it can be stated that the use of live yeast and methionine in livestock diets under heat stress conditions could have positive effects on the digestive and fermentation performance of rumen microorganisms and improve the digestibility and fermentation of wheat straw as a fiber material
Materials and Methods: Forty fattening lambs were acclimatized to experimental conditions for two weeks and subsequently randomly assigned to one of four dietary treatments:1- Control: Basal diet (no additives), 2- PM: Basal diet + 4 g protected methionine, 3- LY: Basal diet + 5.5 g Saccharomyces cerevisiae (live yeast), 4- PM+LY: Basal diet + 4 g protected methionine + 5.5 g Saccharomyces cerevisiae. On day 55 and 70 of the experimental period, rumen fluid samples were collected from all lambs per treatment group. Samples from each treatment were pooled to assess the effects on digestive and fermentative activity of wheat straw as a fibrous substrate. The cumulative gas production was measured at 2, 4, 6, 8, 10, 12, 24, 48, 72, and 96 h. The gas production parameters, Organic matter digestibility (OMD), apparent OMD, metabolizable energy (ME), net energy for lactation (NEL), Dry matter intake (DMI), digestible DMI, growth rate, pH, ammonia nitrogen (NH₃-N) concentration, and protozoal population were estimated. Data were analyzed using a completely randomized design via the PROC GLM procedure in SAS (version 9.4). Treatment means were compared using the Duncan test (α = 0.05).
Results: The protected methionine + live yeast (PM+LY) treatment exhibited the highest gas production potential and rate, while the control treatment showed the lowest values. The difference between the PM+LY treatment and all other treatments was significant. Although the PM treatment produced more gas than the control (P<0.05), it produced less gas than the LY treatment and the PM+LY combination (P < 0.05). In the experimental diets, the partitioning factor (PF), microbial biomass production, and microbial biomass production efficiency were significantly higher in additive-containing treatments than in the control (P<0.05). In this regard, the control had the lowest values, and the PM+LY treatment had the highest. However, for PF, microbial biomass production, and microbial biomass production efficiency, no significant differences were observed between the PM treatment and the control. Furthermore, the results showed that truly degraded organic matter (TDOM) was significantly higher in the control than in all other treatments; the control had the highest TDOM, and the PM+LY treatment had the lowest. Among the additive-containing treatments, TDOM also differed significantly from one another (P < 0.05). Dry matter intake (DMI), digestible dry matter intake (DDMI), and estimated growth rate were significantly lowest in the control and highest in the PM+LY treatment. The LY treatment showed higher DMI, DDMI, and growth rate compared to the protected methionine treatment and the control (P < 0.05). Metabolizable energy (ME), net energy for lactation (NEL), apparent organic matter digestibility, organic matter digestibility, and short-chain fatty acids (SCFA) were lowest in the control and highest in the PM treatment; the differences between the PM treatment and both the control and the LY treatment were significant (P < 0.05). The effect of treatments on culture pH was not significant. Ammonia‑nitrogen concentration was higher in additive‑containing treatments than in the control, with the PM+LY treatment having the highest concentration. The results also indicated that the populations of Holotrichs, Entodiniomorphs, cellulolytic protozoa, and total rumen protozoa were lowest in the control and highest in the PM+LY treatment. No significant difference was found between the control and the PM treatment. However, a significant difference existed between the PM treatment and the LY treatment, with the LY treatment having higher populations of Holotrichs, Entodiniomorphs, cellulolytic protozoa, and total rumen protozoa than the PM treatment.
Conclusion: According to the results of the present experiment, it can be stated that the use of live yeast and methionine in livestock diets under heat stress conditions could have positive effects on the digestive and fermentation performance of rumen microorganisms and improve the digestibility and fermentation of wheat straw as a fiber material
Type of Study: Applicable |
Subject:
تغذیه نشخوارکنندگان
Received: 2025/08/12 | Accepted: 2026/06/21
Received: 2025/08/12 | Accepted: 2026/06/21
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