2020) Effect of tannins and monensin on feeding behaviour, feed intake, digestive parameters and microbial efficiency of nellore cowsABSTRACT This study aimed to evaluate the associative effect of monensin and tannins on intake, feeding behaviour, digestibility, rumen kinetics, microbial protein synthesis and nitrogen balance. In a 2 Â 4 factorial arrangement, 8 rumen cannulated Nellore cows were distributed in 2 contemporary 4 Â 4 Latin squares and received 8 diets that differed in the level of tannins (0.00, 0.75, 1.50 and 2.25% DM) and presence of monensin. Monensin was daily administered to each cow in one square (about 32 mg/kg DM). No interaction between monensin and tannins was observed (p > .05). Tannins linearly reduced feed intake, but linearly increased daily eating time (p < .05), although these did not alter the number of meals. Monensin increased CP digestibility by 6% (p ¼ .0387) while tannins linearly reduced digestibility of DM, CP, OM and TDN, whereas the reduction was quadratic for ADF and NDF. Tannins linearly reduced the rumen disappearance rate by linearly reducing both passage and digestion rates. Tannins also linearly reduced urinary urea, though neither additive affected microbial protein synthesis. Monensin reduced the proportion of N excreted in faeces, whereas tannins linearly increased faecal N and linearly reduced both urinary and retained N. Monensin and tannins have shown independent effects on feeding behaviour, feed intake, digestive parameters, microbial protein synthesis and N balance, but they did not improve nutrient usage, although monensin alone has shown to have potential to promote N utilisation. Tannins may play an important role in reducing the excretion of N in urine. HIGHLIGHTSTannins reduce the efficiency of nutrient usage in cattle. Tannins change the pathway of the excretion of the feeding nitrogen. The emission of N 2 O from the urine may be reduced by the use of tannins in cattle feeding. ARTICLE HISTORYpromoting the production of propionate (Duffield et al., 2008a). This may alter the feeding behaviour and reduce DMI by a metabolic-feedback effect. The meta-analysis of Duffield et al. (2012) shows that monensin reduces DMI and improves average daily gain through improvement of feed efficiency. But other studies, such as of Hamilton et al. (2010), Mullins et al. (2012) and Perna Junior et al. (2017 found no effect, suggesting that the effect may vary among studies. Monensin also reduces rumen protein digestion with a consequent reduction of rumen ammonia production CONTACT Dr.

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The present study aimed to evaluate the effects of different doses of a spray-dried polyclonal antibody preparation against specific ruminal bacteria on rumen fermentation parameters as well as protozoa counts, in situ degradability of sugarcane NDF and total tract apparent digestibility of total diet in cattle fed high concentrate diets. Eight ruminally cannulated cows were used in a replicated 4x4 Latin square design with four periods of 21d. The treatments were T1: 0.0 g/d of PAP-MV, (control); T2: 1.5 g/d of PAP-MV; T3: 3.0 g/d of PAP-MV; T4: 4.5 g/d of PAP-MV. Sample collection for rumen fermentation parameters was carried out at the last day of each period at 0, 2, 4, 6, 8, 10 and 12 h after morning meal. Independently from sampling time, there was no linear or quadratic effect on rumen pH, total concentration of short chain fatty acids, molar proportion of acetate, propionate and butyrate, ammonia nitrogen or lactate. No treatment effects were detected for protozoa counts, in situ degradability of sugarcane NDF and total tract apparent digestibility of total diet. Thus, it can be concluded that different levels of spray-dried PAP-MV were not sufficient to alter rumen environment.

The effect of a polyclonal antibody preparation (PAP) against Streptococcus bovis and Fusobacterium necrophorum on ruminal fermentation and digestion in ruminally cannulated cows was investigated in two 3 × 3 Latin squares in factorial arrangement of treatments 3 × 2 regarding two feed additives (PAP in powder (PAPP) and in liquid (PAPL) presentation) plus control (CON) and two managements of diets (with or without adaptation to highly fermentable carbohydrate diets). Adapted group had greater DMI (p < 0.0001) and DM (p < 0.0001), NDF (p = 0.03) and total carbohydrates (p < 0.0001) apparent digestibility when compared to non-adapted group. PAPL had greater DM (p = 0.02), NDF (p = 0.03) and total carbohydrates apparent digestibility when compared to PAPP or CON. Adapted animals had lower (p < 0.0001) rumen pH when compared to non-adapted animals. Moreover, PAPL group had greater (p = 0.04) rumen pH values when compared to PAPP and CON. PAPL showed potential effect as an additive by increasing apparent digestibility of DM, NDF and total carbohydrates and also for being more efficient to prevent the drop in rumen pH during the peak of fermentation. ARTICLE HISTORY

Objective: Feed additives that modify rumen fermentation can be used to prevent metabolic disturbances such as acidosis and optimize beef cattle production. The study evaluated the effects of liquid and powdered forms of polyclonal antibody preparation (PAP) against <i>Streptococcus bovis</i> and Fusobacterium necrophorum on rumen fermentation parameters in ruminally cannulated non-lactating dairy cows that were adapted or unadapted to a high concentrate diet.Methods: A double 3×3 Latin square design was used with three PAP treatments (control, powdered, and liquid PAP) and two adaptation protocols (adapted, unadapted; applied to the square). Adapted animals were transitioned for 2 weeks from an all-forage to an 80% concentrate diet, while unadapted animals were switched abruptly.Results: Interactions between sampling time and adaptation were observed; 12 h after feeding, the adapted group had lower ruminal pH and greater total short chain fatty acid concentrations than the unadapted group, while the opposite was observed after 24 h. Acetate:propionate ratio, molar proportion of butyrate and ammonia nitrogen concentration were generally greater in adapted than unadapted cattle up to 36 h after feeding. Adaptation promoted 3.5 times the number of <i>Entodinium</i> protozoa but copy numbers of <i>Streptococcus bovis</i> and Fibrobacter succinogens genes in rumen fluid were not affected. However, neither liquid nor powdered forms of PAP altered rumen acidosis variables in adapted or unadapted animals.Conclusion: Adaptation of cattle to highly fermentable carbohydrate diets promoted a more stable ruminal environment, but PAP was not effective in this study in which no animal experienced acute or sub-acute rumen acidosis.