Influence of different sources of zinc and protein supplementation on digestion and rumen fermentation parameters in sheep consuming low-quality hay

Sheep Methane Emission on Semiarid Native Pasture-Potential Impacts of Either Zinc Sulfate or Propylene Glycol as Mitigation Strategies

The aim of this study was to evaluate the effects of Zinc sulfate and propylene glycol (PG) on methane (CH₄) emission, nutrient intake, digestibility, and production in sheep grazing on a native Caatinga (Brazilian semi-arid savannah) pasture during the rainy season (from March to June 2014). Fifteen mixed Santa Inês sheep, all non-castrated males, with initial body weight of 19.8 ± 1.64 kg, and 4 ± 0.35 months of age, were distributed in a complete randomized design into three treatments: control (CT)-concentrate supplemented at 0.7% of body weight; CT + 300 mg of Zn/day; and CT + 2.5 mL of propylene glycol/kg LW^0.75/day. Measurements were done in four periods during the rainy season, with 28 days of interval between each measurement. CH₄ emission was measured using the SF₆ tracer gas technique. CH₄ emission per day was greater in PG than in CT and Zn (p < 0.05). However, no additive effect was observed on the intakes of organic matter (OM) and neutral detergent fiber (NDF), or on CH₄ emission expressed as a function of OM and NDF intakes (p > 0.05). Across the months of the trial, OM and NDF intakes were greater in March, while the greatest emission of CH₄ (g/day and g by g/OM intake) was observed in May (p < 0.05). Total CH₄ emission (kg) from March to June (112 days of evaluation) was greater in PG compared with CT and Zn (p < 0.05). Zinc and PG had no effect on total CH₄ emission when it was expressed per unit of body weight gain or carcass production (p > 0.05). The results of this study indicate that Zinc sulfate and propylene glycol have no beneficial effects in mitigating sheep CH₄ emission. The CH₄ emissions originated from sheep grazing native Caatinga pasture change throughout the rainy season due to fluctuations in availability and quality of pasture biomass. Moreover, the inclusion of zinc sulfate or propylene glycol did not improve animal feed intake, nutrient digestibility, and animal performance.

Effects of Zinc Sulfate or Propylene Glycol on Intake, Digestibility, and Forage Selection by Grazing Sheep in a Semi-Arid Region During the Rainy Season

Simple Summary

Caatinga is an important biome in Brazil’s semi-arid region, it is characterized by low precipitation and great plant availability seasonality. In this context, mineral and energy supplementation may improve pasture consumption and nutrient utilization. The objective of this study was to determine intake, nutrient availability, and animal selection of major forage species by sheep supplemented with zinc sulfate or propylene glycol in Caatinga-native pastures during the rainy season. Twenty-four sheep were distributed into three treatments (control, Zn, and propylene glycol supplement) in this 112-day study. There was no effect of treatments on plant selection. However, plant species selected by sheep changed over time. Generally, greater intakes were found in April compared to May. In conclusions, based on the finding of this study, Zn and PG supplementation did not improve sheep nutrient intake when grazing Caatinga-native pasture in the rainy season.

Abstract

The objective of this study was to determine intake, nutrient availability, and animal selection of major forage species in sheep supplemented with zinc sulfate or propylene glycol in Caatinga-native pastures during the rainy season. Twenty-four mixed Santa Inês sheep, all non-castrated males, with initial weight of 19.3 ± 2.52 kg and 4 ± 0.35 months of age, were distributed in a complete randomized design into three treatments: Control (CT)—concentrate supplemented at 0.7% of body weight; CT + 300 mg of Zn day⁻¹; CT + 2.5 mL of propylene glycol/kg LW^0.75·day⁻¹. Measurements were done in four periods during the rainy season, with 28 days of interval between each measurement. Differences were observed in the composition of the ruminal extrusa samples from pastures for crude protein (CP) (192 to 131 g kg⁻¹), in vitro dry matter digestibility (IVDMD) (537 to 441 g kg⁻¹), and in vitro organic matter digestibility (IVOMD) (468 to 359 g kg⁻¹) in March and June, respectively. There was no effect for treatments, neither for the treatment x period interaction on organic matter (OM), CP, and fibrous fraction intake (p > 0.05). Organic matter intake (OMI) was, on average 23.9% greater in March compared to June. CP intake decreased monthly (p < 0.05). Fibrous fraction intake was greater in March (p < 0.05), with reductions of 34.8, 33.3, and 39.4% in June, respectively, for neutral detergent fiber (NDF), acid detergent fiber (ADF), and cellulose (CEL) fractions. There was no effect of treatments (p > 0.05) on selection of vegetal species present in the pasture. On the other hand, the proportion between ingested species changed over the experimental period. Greater intakes were found in April compared to May, except for Zizyphus joazeiro intake, which was greater in March (p < 0.05). In conclusion, based on the finding of this study, Zn and propylene glycol (PG) supplementation did not improve sheep nutrient intake when grazing Caatinga-native pasture in the rainy season. Caatinga-native pasture biomass has adequate protein and digestible organic matter levels during early rainy season. Over this period, however, the advanced maturity of the plants and the reduced availability of pasture may result in variations of intake by the animals. In the months of April to June, a reduced energy supply is caused by reduced nutritive values of pastures, which contributes to inefficient protein utilization and reduced feed intake.