Journal of animal science最新文献

Feedlot cattle in the U.S. have been progressively fed to heavier, more extreme endpoints (EPs) in recent decades. The primary objective was to evaluate economic risk associated with extending days-on-feed (DOF) by characterizing net return distributions of feedlot steers fed to later EPs, compared to current industry standards. Stochastic simulation modeling was employed to simulate a variety of conditions, including cattle performance, health, carcass characteristics, and economic market variability at the pen-level. The model was parameterized using data from a large commercial feedlot trial and industry reports. The trial involved cattle harvested at four EPs (EP1, EP2, EP3, EP4), each separated by 14 DOF. EP1 represented the industry standard, with live and carcass weights reflective of industry averages from 2021 to mid-2024. The model's final outcome was net return difference - the difference in net returns for EP2, EP3, and EP4 compared to if pens had alternatively been marketed at EP1 under a given set of simulated conditions. Conditional random forest models were used to compute variable importance scores to determine the most influential factors on net return differences. Results indicated that as steers were fed to later EPs, net return distributions widened, reflecting increased economic risk. Steers marketed on a dressed (carcass) basis using a grid for premiums and discounts showed a higher frequency of negative net returns compared to a live marketing basis, primarily due to discounts for Yield Grade and heavyweight carcasses. Across both sale basis, negative net returns became more frequent with increasing EPs. The most influential variable was the difference in fed cattle prices received between later-fed EPs and EP1, accounting for price changes when delaying marketing. Other important economic factors included base fed cattle prices, corn prices, and the Quality Grade grid when grid marketing. Mortality risk was the most important non-economic variable, while other animal performance variables, such as weight and carcass traits, were of marginal to minimal importance. These findings highlight the dominant role of economic factors on net returns when feeding steers to later EPs, emphasizing the need to prioritize market conditions in EP management decisions.

Two experiments were conducted to determine the energy content and amino acid (AA) digestibility of 10 brewer's spent grain (BSG) for growing pigs, with the goal of developing predictive models for these digestible nutrients based on their chemical composition. In Exp. 1, 66 crossbred barrows (initial body weight (BW): 35.5±4.5 kg) were randomly assigned to 1 of 11 diets, including a corn basal diet and 10 test diets in which 20% of the corn was replaced with BSG. Difference method was employed to calculate the digestible energy (DE) and metabolizable energy (ME) of BSG. In Exp. 2, 11 crossbred barrows (initial BW: 32.3±3.8 kg) were surgically fitted with T-cannulas in the distal ileum and randomly assigned to an 11×6 incomplete Latin square design with 11 diets and 6 experimental periods, including a nitrogen-free diet and 10 test diets formulated with BSG as the sole nitrogen source, with 0.4% titanium dioxide added as an indigestible marker to calculate the standardized ileal digestibility (SID) of AA. Results showed that there was considerable variation in the chemical composition of BSG, with all coefficient of variation exceeding 10%. On a dry matter basis, the mean DE and ME values were 2,771 and 2,610 kcal/kg, respectively. The best prediction equations for DE and ME were: DE=-1698+(1.21×GE)-(27.02×NDF) (R2=0.99, P<0.01), and ME=-1800+(1.18×GE)-(25.11×NDF) (R2=0.99, P<0.01). The mean SID values of Lys, Met, Thr, Trp, and Val was 63.1%, 73.4%, 63.8%, 77.7%, and 72.8%, respectively, both were positively correlated (P<0.05) with gross energy, ether extract and crude protein content, and negatively correlated (P<0.05) with fiber content. In conclusion, predictive models for DE, ME, and SID of AA can be developed based on the nutrient composition of BSG in growing pigs. However, considering the inherent variability in nutrient composition, the accuracy and applicability of these models in practical feed formulation require validation using samples from an independent data set.

Commercial cat foods contain a greater carbohydrate content, as nitrogen-free extract (NFE), compared to a typical prey species. This has led to postulations that increased carbohydrate intake is causing a rise in obesity and insulin resistance in cats. Studies investigating high carbohydrate diets on insulin and glucose responses show inconsistent results. A meta-analysis using 16 studies was conducted to elucidate the relationship between NFE content and body fat mass (BFM, n=9), fasted insulin (n=12), and fasted glucose concentrations (n=14). Dietary NFE, fat, and protein content (% metabolizable energy), as well as daily energy intake (DEI), body weight, body condition (lean, obese), and study design metrics were considered as fixed effects in univariate and multivariate models using proc mixed in SAS, treating study as a random effect. Model evaluation was conducted using corrected Akaike Information Criteria, concordance correlation coefficient, and the root mean square prediction error. The best fitting model for BFM was the interaction between NFE content and DEI, predicting BFM to decrease when NFE content increased as a proportion of the DEI (P<0.05). From univariate models, fasted insulin was positively associated with BFM and dietary fat content (P<0.05), whereas an increase in NFE content was associated with a decrease in fasted insulin in a subgroup of studies (n=6) of only lean cats (P<0.05). No significance was observed for models predicting fasted glucose from diet or body composition variables (P>0.05). The results of this meta-analysis indicate that dietary carbohydrates (NFE), included between 2.8 - 57 % ME, are not a risk factor for greater BFM, fasted insulin, and glucose concentrations in cats, suggesting that NFE does not pose a risk for feline obesity, IR, or hyperglycemia. However, future studies should consider post-prandial responses of insulin and glucose to macronutrient compositions to further investigate the role of dietary carbohydrates on IR in cats, with particular attention to the role of dietary fat, and the role of body condition.

The objective was to test the hypothesis that standardized ileal digestibility (SID) of amino acids (AA), metabolizable energy (ME), and standardized total tract digestibility (STTD) of P in soybean expellers produced from a new variety of high-oil soybeans (SBE-HO) are not different when compared with expellers produced from conventional soybeans (SBE-CV). In Exp. 1, nine barrows (30.0 ± 1.5 kg) that had a T-cannula installed in the distal ileum were allotted to a triplicated 3 × 3 Latin Square design with three diets and three periods in each square. An N-free diet and two diets containing SBE-CV or SBE-HO were used. Pigs were housed individually in fully slatted pens and ileal digesta were collected on d 6 and 7 of each period. Ileal digesta and diets were analyzed for AA, and SID of AA was calculated. Results indicated that the SID of Arg, Ile, and Lys was not different between the two sources of soybean expellers, but the SID of other indispensable AA were greater (P < 0.05) in SBE-CV compared with SBE-HO. However, because of greater AA concentration, SBE-HO had greater concentrations of digestible Arg, Lys, Met, and Trp compared SBE-CV. In Exp. 2, thirty pigs (18.3 ± 1.3 kg) were randomly allotted to three diets containing corn, corn and SBE-CV, or corn and SBE-HO as energy sources. Pigs were housed in metabolism crates and feces and urine were separately collected for 4 d after 5 d of adaptation. Feces, urine, and diets were analyzed for gross energy and ME was calculated. Results indicated that ME in SBE-HO was not different from ME in SBE-CV. In Exp. 3, forty-eight barrows (12.0 ± 1.6 kg) were allotted to six diets. The SBE-CV and SBE-HO were included in diets with three levels of microbial phytase (i.e., 0, 500, or 1,000 units/kg). Pigs were housed in metabolism crates and feces were collected quantitatively for 4 d after 5 d of adaptation. Feces and diets were analyzed for P and the STTD of P was calculated. Results indicated that inclusion of phytase in the diets linearly (P < 0.001) increased the STTD of P regardless of source of soybean expellers, but STTD of P was not different between SBE-HO and SBE-CV. It is concluded that if SBE-HO is included in diets for pigs instead of SBE-CV, slightly less soybean expellers is needed due to greater concentration of limiting AA, but ME and STTD of P will not be changed.

A total of 352 sows were used to investigate the effect of soybean meal (SBM) level and adjusted branched-chain amino acid (BCAA) balance on lactating sow and piglet performance. On day 112 ± 1.5 of gestation, sows were randomly assigned, within parity, to one of four dietary treatments: low SBM (LSBM), high SBM (HSBM), LSBM with adjusted BCAA (LSBM+BCAA), or HSBM with adjusted BCAA (HSBM+BCAA). The BCAA balance was adjusted to achieve equal standardized ileal digestible (SID) Ile:Leu:Val in the LSBM and HSBM+BCAA diets (SID Ile:Leu:Val 0.49:1.00:0.73) and in the HSBM and LSBM+BCAA diets (SID Ile:Leu:Val 0.54:1.00:0.58). All diets were formulated to be equal in SID Lys, isocaloric, and meet or exceed NRC (2012) recommendations for all other essential amino acids, vitamins, and minerals. Sow body weight (BW) and backfat thickness (BF) were measured at the time of entry into the farrowing room and at weaning. Litter weights were captured after cross-fostering and at weaning to calculate litter growth rate. Data were analyzed using generalized linear mixed models in R (v4.4.1; R Core Team, 2024) with fixed effects of dietary treatment, parity group, and their interaction and a random effect of lactation group. The sow and her litter were the experimental unit, and results were considered significant if P ≤ 0.05. There was an effect of the dietary treatments on sow average daily feed intake (ADFI; P < 0.001). Sows consuming the LSBM diet exhibited greater ADFI compared to HSBM (7.43 vs. 7.05 kg/d; P = 0.024) or HSBM+BCAA (7.43 vs. 6.87; P < 0.001), while sows fed LSBM+BCAA showed greater ADFI than HSBM+BCAA (7.24 vs. 6.87; P = 0.025), but similar ADFI to LSBM- (P = 0.515) and HSBM-fed (P = 0.466) fed sows. Despite differences in ADFI, sows gained an average of 7.1 kg of BW (P = 0.682) and lost 1.3 mm of BF (P = 0.928) through the lactation period. Sows started the trial with an average of 14.0 piglets/sow (P = 0.787) and weaned 12.6 piglets/sow (P = 0.875) with a piglet average daily gain of 0.22 kg/d (P = 0.646). Increasing SBM inclusion by 14% reduced sow ADFI in lactation by approximately 5%, but did not alter sow BW or BF loss or piglet growth rate. While adjusting BCAA in the LSBM diet slightly reduced sow feed intake, adjusting BCAA in the HSBM diet did not alleviate the reduction in ADFI caused by elevated SBM, suggesting the balance of BCAA does not contribute to the feed intake response observed with elevated SBM inclusion in lactation diets.