Effects of Oil Supplements on Growth Performance, Eating Behavior, Ruminal Fermentation, and Ruminal Morphology in Lambs during Transition from a Low- to a High-Grain Diet

Abstract

The objectives of this study were to investigate the effect of a maximum recommended oil supplementation on growth performance, eating behavior, ruminal fermentation, and ruminal morphological characteristics in growing lambs during transition from a low- to a high-grain diet. A total of 21 Afshari male lambs with an initial body weight (BW) of 41.4 ± 9.1 kg (mean ± SD) and at 5–6 months of age were randomly assigned to one of three dietary treatments (n = 7 per group), including (1) a grain-based diet with no fat supplement (CON), (2) CON plus 80 g/d of prilled palm oil (PALM), and (3) CON plus 80 g/d soybean oil (SOY); oils were equivalent to 50 g/kg of dry matter based on initial dry matter intake (DMI). All lambs were adapted to the high-grain diet for 21 d. In the adaptation period, lambs were gradually transferred to a dietary forage-to-concentrate ratio of 20:80 by replacing 100 g/kg of the preceding diet every 3 d. Thereafter, lambs were fed experimental diets for another 22 days. Fat-supplemented lambs had greater DMI, body weight (BW), and average daily gain (ADG), with a lower feed to gain ratio (p < 0.05), compared to CON lambs. The highest differences of DMI between fat-supplemented and CON-lambs were observed in week 3 of the adaptation period (p = 0.010). PALM- or SOY-supplementation lowered DM and NDF digestibility compared with CON (p < 0.05), and SOY caused the lowest organic matter (OM) digestibility compared with CON and PALM lambs (62.0 vs. 67.6 and 66.9; p < 0.05). Ruminal pH was higher for PALM and SOY compared with CON (p = 0.018). Lambs in SOY tended to have the highest ammonia-N concentrations (p = 0.075), together with a trend for higher concentrations of propionic acid, at the expense of acetic acid in ruminal fluid, on the last day of the adaptation period (diet × time, p = 0.079). Fat-supplemented lambs had lower isovaleric and valeric acid concentrations compared with CON on d 40 (diet × time, p < 0.05). PALM and SOY-fed lambs had a longer eating time (min/d and min/kg of DMI), chewing activity (min/d), meal frequency (n), and duration of eating the first and second meals after morning feeding (p < 0.05), and the largest meal size (p < 0.001). Fat supplemented lambs had greater ruminal papillary length (p < 0.05) and width (p < 0.01), and thicker submucosal, epithelial, and muscle layers, compared with the CON (p < 0.01). Blood metabolites were not influenced by dietary treatments (p > 0.05). The results from this study suggest that fat supplementation to high-grain diets may improve the development of ruminal epithelia and modify ruminal fermentation via optimized eating behavior or the direct effect of oils on the ruminal environment, resulting in better growth performance in growing lambs.

The type of lipid supplement has crucial implications for forage particle size in calf starter diets

“…Although limited documents are available on the effect of supplemental lipid on oxidative stress indicators in dairy calves [ 48 ], Tsai et al [ 49 ] indicated that SBO rich in linoleic acid has some pro-inflammatory effect in young ruminants that can modulate intake and performance in pre-weaning calves. The ruminal metabolism of FA should also be considered with caution when lipid supplementation is provided to dairy cows [ 50 , 51 ], calves [ 52 ] or lambs [ 14 , 15 ]. Most of the negative responses to supplemental unsaturated FA had been attributed to its negative influence on ruminal fermentation and microbial activity in calves under 2 months of age [ 13 , 46 ]; however, it seems that additional effects on energy metabolism and its hormonal regulation, as well as on oxidative stress and possibly inflammation, should receive additional attention in future studies.…”

“…Some previous studies addressed the interaction effect of forage source and lipid supplement on performance of dairy calves [ 11 , 13 ]; however, the combined effects of forage particle size and lipid supplement need to be evaluated in dairy calves. In addition, as stated in previous studies [ 12 , 14 , 16 ], lipid supplement may have different impacts from the oxidative stress perspective, which can eventually influence whole animal body metabolism. The interactive effect of FPS with different lipid supplement on the oxidative stress of young calves also needs to be evaluated in dairy calves.…”

“…The biological activities of lipids extend beyond serving as an energy source and maintaining normal biological functions; however, there is limited understanding of how they are utilized by developing dairy calves. In recent studies, oil supplementation to growing lambs’ diet improved ruminal health and development, feeding behavior and animal performance [ 14 ], as well as ruminal epithelial function and metabolism [ 15 ]. A better understanding of lipid metabolism and the impacts of supplementation of dietary fats or manipulations of energy sources may offer new ways to enhance development and improve performance of growing replacement heifers through nutritional strategies [ 16 ].…”