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The objectives of this study were to compare estimates of greenhouse gas emissions (GHG) as CH 4 (enteric-manure), N 2 O (manure), and CO 2 (fuel and energy use), the use of water and soil, the excretion of nutrients in manure, and feed efficiency from Mexican intensive dairy farms. Data from 26 dairy farms were analysed with a multivariable cluster analysis. Three grades of intensifications were identified (low, medium and high). Mathematical models were used to estimate GHG. Feed efficiency (kg milk per kg DMI) was better in high intensive production systems. Enteric methane was identified as the major source of GHG in all types of systems. High intensive dairies generated the lowest emissions of CH 4, N 2 O and CO 2 equivalent by unit of product, 18.6 g, 0.12 g and 828 g, respectively. Water footprint was lower in low intensive dairies using 427 L of water/L of milk. Cropland was highest in intensive systems but milk yield per area was better (30,938 kg/ha). Excretions of N, P, and K were lower in intensive dairies per kg of milk, at 13.2, 2.4, and 6.4 g, respectively. As intensification in the dairy system increased feed efficiency (kg milk/kg DMI) was better. Per unit of product (kg of milk), dairies with the highest intensification generated the lowest GHG emissions, nutrient excretion values and land and water use as compared to dairies with medium and low intensification. Increasing intensification and therefore feed efficiency of Mexican dairy systems could help to decrease GHG emissions, natural resources use and nutrient excretion. ____________________________________________________________________________________

The aim of this research was to determine fatty acid profiles in piglet brain, skin, and muscle, and in the milk of sows fed fat with different saturation grades during gestation and lactation. At 42 days of gestation, 50 multiparous sows were randomly allocated to one of two treatments, namely a diet containing pork lard (n = 25) and a diet containing soybean oil (n = 25). The fats were provided at 3.6% during gestation and at 4% during lactation. The experimental diets were offered through the weaning of the piglets. The fatty acid profile of the milk was determined fourteen days after parturition. At weaning (21 days postpartum) and seven days later, one of the piglets (n = 64) from 16 sows allocated to each treatment was selected at random to determine fatty acid profiles in brain, skin and muscle. Saturated and monounsaturated fatty acids were higher in the diet with pork lard than in that with soybean oil, in which the polyunsaturated fat content was higher. A higher saturation of fatty acids was found in milk from the sows that consumed pork lard, which contained more saturated fatty acids than the milk from sows that consumed soybean oil. The fatty acid profiles in muscle and skin of the piglets were affected by the diet of the sows. However, the fatty acid profile of the piglets’ brains was not affected by the diet of their mothers. Keywords: fat saturation, lard, piglet survival, sow feeding, soybean oil

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

It was hypothesized that feeding mesquite pods to male Rambouillet lambs would have no negative effects on carcass characteristics, meat chemical composition and fatty acid composition of Longissimus thoracis et lumborum (LTL). Twenty-one male lambs (2.5 months old and 21 ± 1.44 kg bodyweight) were randomly assigned to one of three experimental diets, two of which replaced maize grain and stover with mesquite pods (Prosopis laevigata) (PL): 0 g PL/kg feed (PL0), 250 g PL/kg feed (PL250) and 500 g PL/kg feed (dry matter basis). The feeding trial lasted 72 days. Carcass traits, chemical composition, fatty acid profile, and sensory characteristics of meat were measured. Carcass linear dimensions, non-carcass components, digestive tract and offal, compression value, and chemical composition of meat were similar in all treatments. Dietary inclusion of PL decreased carcass shrinkage loss. Lambs fed PL500 had better muscle conformation and degree of fat. Meat produced by PL-fed lambs was well accepted by panellists who judged meat appearance, colour, flavour, juiciness, toughness, and stringiness. In lambs fed PL0, the LTL muscle was lighter and yellower than that of animals fed PL250 and PL500 diets. Fatty acid composition was altered. The PL0 diet resulted in lower percentages of total trans fatty acids (TFA) and saturated fatty acids (SFA) and higher percentages of most unsaturated fatty acids (UFA) and polyunsaturated fatty acids (PUFA) n-6 compared with PL250 and PL500 diets. Mesquite diets of up to 500 g/kg dry matter (DM) for growing lambs improved carcass quality and nutritional parameters of the meat.

To evaluate the dietary inclusion of mesquite pods (Prosopis laevigata) on the growth performance, rumen fermentation, nitrogen balance, blood metabolites and carcass traits, 15 Creole goat kids (12.1 ± 2.8 kg body weight) were randomly assigned to one of three experimental diets with 0, 300 and 600 g of mesquite pods (dry matter basis). The study lasted 80 days. At the end of this period, the blood and ruminal fluid were sampled and the nitrogen (N) balance was calculated. The growth performance and feed intake were not affected by the mesquite pods. The nitrogen digestibility, N absorbed, and N retained increased linearly (P < 0.05) with the increasing amounts of mesquite pods in the diet. The serum glucose and triglycerides were not affected by the mesquite pods, but the creatinine and uric acid decreased linearly (P < 0.05) as the mesquite pods increased in the diet. The highest (P < 0.05) rumen pH value, ammonia-N concentration, molar proportion of the acetate and the acetate : propionate ratio was found in the goat kids fed the diet with 600 g when compared to those fed diets with 0 and 300 g mesquite pods. Beneficial dietary effects of mesquite pods on the blood metabolites and N retention of the goat kids were found in this study; therefore, the dietary inclusion of mesquite pods at 600 g/kg can be used as a feed alternative for growing goat kids.

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