No abstract

One in vitro assay and one in vivo trial with ruminally cannulated Holstein steers were conducted to evaluate the effects of a dietary substitution of soybean meal by a urea and slow-release urea source of fermentation and degradation of diets for cattle. The experimental diets consisted of the total mixed rations defined as the control with soybean meal (SBM), U (urea), SRU (slow-release urea), and SRU+U+AA (0.42% + 0.42% + 1% amino acids methionine and lysine). The dietary substitution of SBM by U or SRU reduced (P < 0.05) the total gas production (V), microbial mass and degradation at 72 h incubation under the in vitro conditions, as well as the degradation rate (c) and the total volatile fatty acids (VFA) in the rumen of the steers; however, when the dietary substitution of SBM was by U+SRU+AA, those values did not decrease. In the steers, the dietary substitution of SBM by U and SRU reduced the ruminal degradation rate and the total VFA, and increased the ammonia N, but when SBM was substituted by U+SRU+AA in the diets, these changes were not observed. No advantage of SRU over U was found. The dietary substitution of SBM by U, SRU, U+SRU+AA did not modify the molar proportion of the VFA in the rumen nor were there changes in the nutrient digestion or excretion. Both the in vitro assay and the in vivo trial indicated that replacing SBM with U or SRU increases the ruminal ammonia N concentrations and reduces the degradation rate in the rumen, although those undesirable findings were not found when the SBM was replaced by U+SRU+AA. Therefore, it is feasible to replace the SBM with a combination of urea, slow-release urea, lysine and methionine in the diet for the ruminants.

Growing lambs were evaluated for the effect of increasing dietary levels of beef tallow (BT) on performance, rumen fermentation, and carcass and meat characteristics. Twenty-one 5-month-old male Rambouillet lambs were assigned randomly to one of three diets with 0, 20, and 40 g BT/kg dry matter (DM) and similar energy and protein contents. Lambs were adapted to the diets for 15 days, followed by a 45-day evaluation trial. Data were analysed using a mixed model. Growth, feed intake and ruminal fermentation were not affected by the dietary level of BT. Daily metabolizable energy intake (MEI), carcass yield and degree of fatness, increased linearly as the BT level increased. Carcass classification and muscle conformation were not affected by BT. Most meat characteristics (texture, pH, myoglobin, protein content, colour, cathepsins, and chemical composition) five and eight days post-mortem were not affected, except for fat content in meat, which increased linearly as diet BT level increased. Fatty acid (FA) profiles of the meat from lambs fed the three diets were similar. In conclusion, addition of BT at 20 and 40 g/kg DM to diets for growing lambs allowed reduced grain usage and increased forage levels (from 0 to 270 g/kg DM), increasing energy intake, carcass yield and fatness, and intramuscular fat without causing harmful effects on growth, feed intake or ruminal fermentation characteristics. Keywords: dietary fat, fatty acids, meat colour, sheep

In order to evaluate the ethnoveterinary effect of Macleaya cordata extract on bacteria colony forming units (CFU) in different organs of gastrointestinal tract and productive parameters of broilers challenged with Salmonella typhimurium, eighty one day old Cobb broilers were randomly assigned either to a diet without additive or with additive at 50 g/ton during 21 days. The count of CFU of Salmonella typhimurium in crop, gizzard, and duodenum, at 21 days, showed broilers that received the Macleaya cordata extract had a reduction. The broilers also had higher final body weight, total gain, average daily gain and better feed conversion value as compared with those that had not received it. Feed intake was not affected. Results concluded that Macleaya cordata extract is an ethnoveterinary alternative efficient for control of Salmonella typhimurium and a growth promoter in broilers.

Growing lambs were used to evaluate the effects of dietary inclusion of yellow grease (YG) on performance and carcass yield. Sixteen male hair lambs were assigned randomly to one of two diets with 0 or 30 g YG/kg DM and similar energy and protein content. Lambs underwent adaptation to diets for 12 d and fasting for 75 d. Dietary inclusion of YG did not affect growth performance or feed intake. Feed conversion, hot and cold carcass weight and yield improved by YG. The dietary addition of 30 g YG/kg DM allowed reducing the proportion of dietary grain without causing harmful effects on growth performance and feed intake but improving carcass dressing in finishing hair lambs. Given that its inclusion in grain-based diets improved carcass weights and yield. We can conclude that YG would be an efficient alternative energy source for hair lambs under tropical conditions. Nevertheless, further research is required to determine the effect of YG on meat and carcass quality.