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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

This study was carried out to evaluate the use of tannin extract from Acacia mearnsii as a strategy to reduce methane (CH4) in two distinct cattle genotypes and its effect on intake, digestibility, microbial efficiency and ruminal fermentation. Four Nellore (Bos indicus) and four Holstein (Bos taurus) dry cows fitted with rumen cannula were assigned to two 4 × 4 Latin square design, in a 2 × 4 factorial arrangement, where each genotype represented a square receiving four tannin levels (commercial extract of A. mearnsii) in the diet (0%, 0.5%, 1.0% and 1.5% of dry matter). Tannin levels used did not cause a reduction in feed intake or rumen passage rate for both genotypes (p > 0.05), although there was a linear reduction in the degradation rate and ruminal disappearance of diet (p < 0.05). The increase in tannin levels reduced the amount of entodiniomorph protozoa in the Nellore cattle (p < 0.05). There was no change in N retention or microbial efficiency (p > 0.05), despite the linear reduction of nutrient digestibility and the synthesis of microbial nitrogen (p < 0.05). The ruminal CH4 production was reduced (p < 0.05) without reducing the short‐chain fatty acid production. The threshold of 0.72% of tannin in the diet was estimated as the starting point for the reduction of ruminal CH4 production with long‐term efficacy. Therefore, the use of low levels of tannin extract from A. mearnsii is a potential option to manipulate rumen fermentation in Nellore and Holstein cattle and needs to be further investigated.

Objective. To evaluate the effect of three energy sources on the intake, total apparent digestibility and excretion of nutrients in cattle diet. Materials and methods. Six ruminally cannulated cows (730 ± 70 kg) were distributed into three treatments in a replicated 3x3 Latin square experimental design, where: (I) Control: Low ether extract diet (3.50% EE); (II) Soybean: High ether extract diet (5.30% EE) with inclusion of 15% soybean and (III) Citrus pulp: Low ether extract diet (3.00% EE) and high pectin involvement with inclusion of 15% citrus pulp. To determine the digestibility of DM and its fractions, chromic oxide was used as a marker. Nutrient excretion was calculated from the digestibility coefficient of each fraction. Results. The soybean treatment reduced (p<0.05) dry matter, crude protein, nitrogen-free extract and organic matter intake and increased ether extract intake. There was no effect (p>0.05) of the energy source on the digestibility coefficients of DM, CP, NDF, EE, NFE or OM. The TDN value was higher for the soybean treatment. The excretion of DM, NFE and OM was lower (p<0.05) for the soybean treatment. All energy sources influenced the excretion of crude protein. Conclusions. The energy sources used did not affect the digestibility of the diets and are indicated as high potential sources to be used in cattle.