The use of glycerin in diets for dairy cows initially emerged as an alternative for the prevention and control of ketosis. However, despite some controversy, there are still several studies associating glycerin with increases in daily milk yield, with possible changes in its constituents. Therefore, the objective of this study was to evaluate, using a meta-analysis approach, the effect of glycerin inclusion in dairy cow diets on milk fatty acid. Twenty-two peer-reviewed publications with 66 treatment means were included in data set. The effect of glycerin inclusion in diet (treatment) were evaluated using random-effect models to examine the weighted mean differences (WMD) between a control diet (without glycerin in the diet) and the treatment diet. Heterogeneity was explored by meta-regression and subgroup analysis performed for: genetic type; days in milk; experimental period; glycerin in diet; glycerin type and concentrate in diet. Inclusion of glycerin in the diet increased the digestibility of dry matter and protein, as well as ruminal propionate. It did not affect dry matter intake (P=0.351) and milk yield (P=0.730). The effect of glycerin inclusion on the milk fat yield is dependent on the genetic group, in which Holstein (WMD= -0.04 kg/d; P=0.010) and Holstein-crossbreed (WMD= -0.10 kg/d; P<.0001) cows produced less fat in milk compared to Jersey cows, when glycerin was included in the diets. Glycine inclusions of up to 100 g/kg in the diet of dairy cows did not negatively affect milk production and composition. However, inclusions above 150 g/kg of glycerin in the diet reduced the concentration of fat, and of unsaturated, monounsaturated, polyunsaturated fatty acids and conjugated linoleic acid (CLA C18: 2 cis-9 and trans-11) in milk. The results reported in our meta-analysis does not demonstrate the effectiveness of glycerin in improving the composition of milk and a group of fatty acids of importance for human health such as C18: 2 cis-9, trans-11 CLA.

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Soybean molasses (SBM) is a byproduct of the manufacture of soy protein concentrate and has high energy value. This byproduct has a high potential for use in the nutrition of ruminant animals, mainly in the replacement of other energy feeds such as corn grain. The objective of this study was to evaluate the inclusion of SBM to replace corn grain up to 30% dry matter (DM) in the total diet on growth performance, feeding behavior, carcass characteristics, and meat quality of feedlot lambs (½ Santa Inês × ½ Dorper). Forty intact male lambs with an initial average body weight of 20.6 ± 2.5 kg and approximate age of 120 d were used. The animals were distributed in four treatments (0%, 10%, 20%, and 30% SBM), divided into five randomized blocks according to the initial weight and adapted for 16 d, with diets containing increasing concentrations of concentrate and SBM. Feeding behavior was analyzed at the beginning, middle, and final of the finishing period, and when animals reached 42 d on the finishing diet they were slaughtered. Data were evaluated using SAS software (version 9.4), by polynomial orthogonal contrasts, where the growth performance, carcass characteristics, and meat quality values were analyzed as randomized blocks, and the feeding behavior data as randomized blocks with a repeated measure over time. Significant differences were detected for the contrast 0 vs. SBM treatments, which the inclusion of SBM caused an increase (P ≤ 0.05) in ash intake but decreased the ether extract intake. The intake of DM in % body weight was higher for SBM treatments than 0% treatment (P ≤ 0.05). Feeding behavior, ruminating while lying down and drinking water presented a decreasing linear effect (P ≤ 0.05), and for feeding, efficiency increased with the addition of SBM (P ≤ 0.05). Fatty acids C14:0, C17:0, C17:1, C18:2n6c, C20:2, and C20:3n6 showed lower values ​​with the inclusion of SBM (P ≤ 0.05), while fatty acids C22:0 and C22:6n3 increased. The values ​​of n6 polyunsaturated fatty acids and n-6/n-3 ratio were lower (P ≤ 0.05) for SBM treatments. The values ​​of total polyunsaturated fatty acids showed a decreasing linear effect (P ≤ 0.05) with the inclusion of SBM. The use of up to 30% SBM in DM did not impair animal growth performance and feeding behavior did not cause damages to carcass parameters and still made the meat healthier, improving the n-6/n-3 ratio, therefore can be used to feed finishing lambs.

The goal of this study was to assess the effects of increasing levels of soybean molasses (SM) on ruminal parameters of feedlot sheep. Nine crossbred ruminally-cannulated male sheep (73.3 ± 2.5 kg BW) were randomly distributed in a triple 3 × 3 Latin square design. The treatments consisted of isonitrogenous (18% CP) and isoenergetic (2.7 Mcal/kg) diets, containing 0, 15 or 30% SM (DM basis). After 14 d of adaptation period, rumen fluid samples were collected in each experimental period, at 0, 2, 4, 6, 8 and 10 h after feeding, to evaluate ruminal pH, NH3-N and VFA concentrations. The pH was measured immediately after rumen fluid sampling, and NH3-N concentrations were determined with micro-Kjeldahl apparatus. The concentration of VFA was assessed by gas chromatography. Data were evaluated using the MIXED procedure of SAS, with repeated measures over time. Orthogonal contrasts were used to determine the linear and quadratic effects of SM inclusions, as well as the contrast Control × SM treatments. There was no interaction of time of sampling × treatment for all variables evaluated (P > 0.05). The inclusion of SM increased linearly (P = 0.02) the ruminal pH (5.92 to 5.21 – 0 and 30%, respectively), and decreased linearly (P = 0.006) the NH3-N concentration (32.19 to 21.78 mg/dL – 0 and 30%, respectively). The addition of SM did not alter most of VFA, with exception for valeric acid (quadratic, P = 0.05), with the higher value observed in 15% SM-fed animals (1.33 mMol/L). However, when the percentage of each VFA was evaluated, the inclusion of SM increased linearly the butyric acid (P = 0.05), from 14.1 to 16.9%. The results indicate that the inclusion of soybean molasses at up to 30% (DM basis) improves the ruminal fermentation of diets in feedlot crossbred sheep.