Screening of antifreeze-thawed lactic acid bacteria and their effects on oat silage fermentation quality and aerobic stability北大核心CSCD

The effects of freeze-thaw conditions on the fermentation quality and aerobic stability of oat silage were investigated. Four strains of freeze-thaw-resistant lactic acid bacteria（LAB）with rapid growth and efficient acid production were screened from 437 strains,which had been isolated from the Qinghai-Tibetan Plateau. Based on physiological and biochemical characteristics and 16S rRNA gene sequence alignment,the four strains were identified as Lactobacillus plantarum 157（LP157）,L. plantarum 160（LP160）,Lactobacillus brevis 248（LB248）,and Lactobacillus pentosus 260（LPE260）. In order to investigate their effects on the fermentation quality,nutrient composition,microbial counts and aerobic stability of oat silage under freeze-thaw conditions,seven treatments were tested as follows：1）LP157;2）LP160;3）LB248;4）LPE260;5）LP160+Lactobacillus rhamnosus 753 mixture （MIX）;6）A commercial bacterial silage additive（COM）;7）The same amount of sterilized distilled water（CK）. All treatments were ensiled for 60 days at a constant temperature of 20 ℃ and under a 20 ℃/-5 ℃ regime alternating every 12 h（freeze-thaw）. LP inoculation improved silage quality：The pH and dry matter loss in silages inoculated with LP157,LP160,LB248 and LPE260 were significantly lower than CK（P<0. 05）and lactic acid and acetic acid contents were significantly higher than CK（P<0. 05）,and the growth of spoilage micro-organisms such as coliform bacteria,yeast and mold were inhibited,both with fermentation at constant 20 ℃ and under freeze-thaw conditions. After aerobic exposure for 5 days,the pH and NH3-N of silages treated with LP157,LP160,LB248 and LPE260 were significantly（P<0. 05） lower than CK,MIX and COM. The aerobic stability of oat silage was improved,especially when inoculated with LP160（70 h vs. CK 11 h）. The results show that the four screened strains can be used as effective LAB inoculants for silage preparation in the freeze-thaw environment of the Qinghai-Tibetan Plateau. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Nitrogen metabolism in dairy cows fed restricted amounts of grass–clover silage supplemented with seeds from narrow-leafed lupin or pea

Twelve dairy cows in mid to late lactation were fed iso-nitrogenous diets (161 g CP/kg DM, forage:concentrate ratio 65:35) where rolled barley and coarsely ground seeds from either narrow-leafed lupin or field pea supplemented grass–clover silage. Feed allowance was individually restricted and fixed (18.8 ± 0.6 kg dry matter/day) throughout the experiment to avoid refusals. The experiment was of 2 × 2 change-over design and utilized a previous change-over experiment with 3 periods as covariate. Nitrogen balance was assessed by quantitative urine sampling and fecal spot sampling in eight cows whereas rumen metabolism was studied in four cannulated cows. Production of energy corrected milk was 24.3 kg/day with the lupin diet and 23.2 kg/day with the pea diet (P < 0.05). Daily milk fat yield was also higher (P < 0.05) with the lupin diet. Proportion of feed N excreted in milk did not differ between diets. Milk urea concentration, as well as the amounts of total urinary N and urinary urea were higher (P < 0.05) for the lupin diet, while urinary N proportion of feed N only tended (P = 0.08) to be higher with the lupin diet. N balance was lower with the lupin diet. Digestibilities of organic matter, neutral detergent fiber and crude protein did not differ between diets and neither did ruminal pools of these constituents. In addition, there were no differences between the diets with respect to the ruminal concentrations of NH₃-N and total volatile fatty acids, and only minor differences in ruminal pH and ruminal concentrations of iso-acids and α-amino-N. It is concluded that the higher fat content in lupins compared to peas is an advantage in typical Scandinavian home-grown rations and probably explains the higher milk yield in this experiment. Differences in protein utilization between lupins and peas are of small magnitude when fed ground without thermal processing. In practical feeding, ad libitum forage allowance may create response differences between lupin seeds and peas not observed in this experiment.     

Replacement levels of elephant grass by moist pineapple by-product silage in diets of Santa Inês crossbred sheep: performance and digestibility

The present study evaluated the effect of replacing elephant grass (EG) with moist pineapple by-product silage (PS) on the apparent digestibility, consumption of digestible nutrients and performance of 25 castrated male lambs Santa Ines crossbreds. The lambs had an initial body weight of 20.2?±?3.5 kg and were housed in individual pens in a completely randomised design with five treatments (replacement of EG by PS at five proportions of 0, 25, 50, 75 and 100 %) and five replicates during 74 days. There was no significant effect of PS replacement proportions on the intake of dry matter (DM), organic matter (OM), total carbohydrates (TC), non-fibrous carbohydrates or total digestible nutrients (TDN). The consumption of crude protein (CP) decreased linearly with the inclusion of PS in the diets. The digestibility of DM, OM and TCs as well as levels of TDN increased linearly with the addition of PS. The use of PS in the diets had no significant effect on the digestibility of CP and neutral detergent fibre corrected for ashes and protein (NDFom(n)). These results demonstrated that there was no difference in the performance of animals fed diets with or without PS.     

Fatty acid profile as affected by fat depot and the sex category of Polish Holstein-Friesian × Limousin fattening cattle fed silage ad libitum

This study was designed to compare the fatty acid profiles of four types of fat depots from bulls, steers, and heifers. All animals were Polish Holstein-Friesian and Limousin crossbreds fattened semi-intensively—silage at libitum and concentrate in the amount corresponding to 30% of their net energy requirements. The fatty acid profile in intramuscular, intermuscular, and external and internal fat was determined. The intramuscular fat of bulls was most abundant in total PUFAs and n-6 PUFAs, and functional fatty acids C 18:2, C 20:4, and C 22:5 in comparison with steers and heifers. Regardless of sex category, intramuscular and external fat were characterized by higher levels of UFAs and a more desirable MUFA/SFA ratio than the remaining fat types. It should also be noted that external fat was more abundant in CLA than other fat types, and that the highest CLA content was found in bull fat, compared with the remaining sex categories of cattle.