Greenhouse gas emissions and nutrient use efficiency assessment of six New York organic dairies.

Improving nutrient use efficiency and reducing greenhouse gas (GHG) emissions are important environmental priorities for organic-certified dairy operations. The objectives of this research were to quantify annual nutrient use and GHG emissions in 6 organic New York dairy farms. Farm-gate nutrient mass balances (NMB) were estimated with the Cornell NMB calculator. Whole-farm GHG emissions were estimated using Cool Farm Tool (CFT) and COMET. Farm-gate NMBs were low, ranging from -6.5 to 19 kg N ha-1 for N1 (without legume N fixation), 26 to 71 kg N ha-1 for N2 (including N fixation), -2.4 to 8.2 kg P ha-1 for P, and 1.1 to 19.8 kg K ha-1 for K. Additional nutrient imports, coupled with nutrient management planning, adequate legume stands and diet balancing may help improve P balances, and ensure no N deficiencies in the system. Estimates of annual GHG emission intensity ranged from 0.98 to 2.10 kg CO2-eq per kg of fat and protein corrected milk (FPCM) estimated by CFT, and from 0.69 to 2.48 kg CO2-eq kg FPCM-1 estimated by COMET. Enteric fermentation, feed production and fuel and energy use represented the largest sources of GHGs. For farms with liquid manure storages, manure management was also a significant source. Estimates of soil carbon (C) stock changes from CFT were in agreement or smaller than previous studies, and estimates from COMET were in agreement or greater. Variability and uncertainty in the results for soil C stock change indicate more research and new protocols are needed. Impact of individual management changes on GHG emissions intensity were small, ranging from -8 to +7% in CFT, and -8% to +8% in COMET. The management changes that resulted in the largest reductions in GHG emissions intensity included increasing individual cow productivity and milk to total feed ratio, and implementation of manure treatment systems.

Non-linear models of 15N partitioning kinetics in late lactation dairy cows from individually-labeled feed ingredients.

Few studies have examined the N kinetics of individual feeds with stable isotope tracing. We hypothesized that N partitioning to milk and excreta pools as well as the rates of the processes that drive this partitioning would differ for alfalfa silage, corn silage, corn grain, and soybean meal. Feed ingredients were endogenously labeled with 15N and included in 4 diets to create treatments with the same dietary composition and different labeled feed. Diets were fed to 12 late-lactation dairy cows for 4 d (96 h) and feces, urine, and milk collection proceeded during the 4 d of 15N enrichment and for 3 d (80 h) after cessation of label feeding. Nonlinear models of 15N enrichment and decay were fit to milk (MN), urine (UN), and fecal N (FN) in R with the nlme package and feed-specific parameter estimates were compared. The estimated proportions of feed N that were excreted in feces supported our understanding that N from soybean meal and corn grain is more digestible than N from alfalfa and corn silage. Estimates for the N partitioning between milk (MN) and urine (UN) from the 2 concentrate feeds (soybean meal and corn grain) indicated that UN:MN ratios were less than or equal to 1:1 indicating either more or equal nitrogen partitioning to milk compared with urine. It is important to maintain factual accuracy in representing the results rather than implying a desired outcome unsupported by the data. In contrast, UN:MN ratios for forage feeds (corn and alfalfa silage) were > 1:1, indicating more N partitioning to urine than milk. The modeled proportion of total FN that originated from feed N was 82.2% which is in line with previous research using a similar 15N measurement timeframe. However, the proportion of urinary and MN originating from feed N was much lower (60.5% for urine, 57.9% for milk), suggesting that approximately 40% of urinary and MN directly originate from body N sources related to protein turnover.

Effect of rumen-protected lysine supplementation of diets based on corn protein fed to lactating dairy cows.

This trial tested whether rumen-protected Lys (RPL) supplementation would improve the nutritive value of rumen-undegradable protein (RUP) from corn protein. Thirty-two lactating Holstein cows were blocked by days in milk and parity into 8 squares of 4 cows each in replicated 4 × 4 Latin squares. Treatments provided all supplemental crude protein from: (1) soy protein (67% expeller soybean meal plus 33% solvent soybean meal); (2) a blend of soy and corn protein (33% expeller soybean meal, 17% solvent soybean meal, 25% corn gluten meal plus 25% distillers dried grains with solubles); (3) corn protein (50% corn gluten meal plus 50% distillers dried grains with solubles); or (4) corn protein plus RPL [diet 3 top-dressed with RPL (125 g/d of AjiPro-L Generation 1, supplying an estimated 20 g of absorbable Lys/d)]. Diets contained (dry matter basis) 22% alfalfa silage, 43% corn silage, 18% ground high-moisture and dry corn, 2.4% mineral-vitamin premix, 1.5 to 3.9% soy hulls, 15% crude protein, 30 to 32% neutral detergent fiber and predicted to contain equal rumen-degradable protein, RUP, and metabolizable protein. Cows within squares were randomly assigned to treatment sequences and fed diets for 4-wk periods before switching; production data and blood samples were collected during last 2 wk of each period. Data were analyzed using the mixed procedures of SAS. Intake was highest on diet 1, intermediate on diets 2 and 3, and lowest on diet 4; body weight gain was highest on diet 3, intermediate on diets 1 and 2 and lowest on diet 4. Intakes and body weight changes were reflected by differences in milk/dry matter intake, which was highest on diets 2 and 4 and lowest on diet 3. Milk yield was lower on diet 3 (44.3 kg/d) than on diets 1, 2, and 4 (average 45.8 kg/d) and protein yield was highest on diets 1 and 2 (average 1.35 kg/d), intermediate on diet 4 (1.30 kg/d), and lowest on diet 3 (1.25 kg/d). No effects of diet were detected on ruminal metabolites. Free nonessential amino acids and total protein AA were elevated in blood plasma on diet 3, reflecting reduced utilization for milk protein synthesis. These results indicated that 50% dilution of soybean meal RUP with that from corn protein did not reduce yield and that supplementing RPL to the corn protein-based diet increased yield 1.1 kg of milk/d and 50 g of true protein/d.

Effects of Amount and Profile of Amino Acids Supply on Lactation Performance, Mammary Gland Metabolism, and Nitrogen Efficiency in Holstein Dairy Cows.

To evaluate the effects of amount and profile of amino acid (AA) on milk protein yield (MPY), mammary metabolism, and efficiency of nitrogen use (ENU), ten cows were used in 5 × 5 replicated Latin squares and fed a positive control (16.1% crude protein-CP) or two lower CP diets (14.6 and 13.2%) with or without essential AA (EAA) infusion. The EAA solutions provided predicted limiting EAA in each treatment and were continuously infused into the abomasum of the cows. Milk production and MPY were not affected by treatment (mean 35.4 kg/d and 1.03 kg/d, respectively). Efficiency of nitrogen utilization was increased as dietary CP decreased but was not affected by EAA infusion (p < 0.01). Energy-corrected milk production was increased by EAA infusion into 13.2% CP, but not into 14.6% CP diet (p = 0.09), reaching the positive control value. Infusions increased mammary affinity for non-infused EAA (Ile, Phe, Thr, and Trp), allowing the same MPY despite lower arterial concentrations of these AA. Higher arterial concentrations of infused EAA did not increase their mammary uptake and MPY (p = 0.40; p = 0.85). Mammary metabolism did not fully explain changes in N efficiency, suggesting that it might be driven by less extramammary catabolism as AA supply was reduced.

Local feeding strategies and milk composition in small-scale dairy production systems during the rainy season in the highlands of Mexico.

The objective of the work was to identify local feeding strategies in small-scale dairy production systems during the rainy season in the highlands of Mexico, and to determine their effects on milk yields (MY), milk composition and economic viability. Twenty-two dairy farms were monitored by monthly visits, recording and sampling milk from between two and six cows in each farm, live-weight was also recorded. Samples from feeds used in that month were taken and feeds given to the dairy herd were weighed. Economic data was also recorded. Milk composition and milk urea nitrogen were determined, as well as chemical composition of feeds. Eighteen feedstuffs were identified, grouped in: HNH feeds-high in neutral detergent fibre (NDF) and in DM matter; HNL feeds-high in NDF but low in DM; HCh feeds-high in non-fibrous carbohydrates; and HCP feeds-high in crude protein. Four feeding strategies were identified: strategy 1 uses HND, HNL and HCP; strategy 2-HND, HNL, HCh and HCP; strategy 3 HNH and HCP; and strategy 4 HNL and HCP. Of participating farms, 73.4% followed strategy 1, 11.3% strategy 2, 11.3% strategy 4 and 3.8% strategy 3. There were no statistical differences (P > 0.05) between strategies for MY and milk composition, but there were differences (P < 0.05) for ration costs. Multiple regression analysis showed no significative (P > 0.05) model relating intake of feed groups and milk fat content, but milk protein and SNF contents were significantly explained by intake of HCP. When expressed as MY and milk components yield, milk fat yield was significantly explained by intake of all four feed groups, but milk protein and SNF yields were explained only by intake of HCP and LW. MUN excretion was explained also by HCP intake. All feeding strategies produced positive economic returns, on average generating the equivalent of 3.45 minimum wages of the area.

Brief, Written Reflections Improve Interest of Introductory Animal Science Undergraduates.

In addition to stimulating interest through experiential means, educators can support interest development through structured reflection. Our randomized controlled intervention study assessed the effectiveness of 10-minute written utility-value reflections designed to enhance the interest of introductory animal science students. During the Spring 2019 semester, we randomly assigned participating students into two blocks, utility-value reflection (n = 39) and control (n = 34), at the beginning of the course. In week 6 during the 16-week semester, students completed corresponding tasks: either written reflections on the personal value of course laboratory material or a control picture-summarization task. Results showed that the utility-value reflection intervention tended to improve situational interest and was most effective for students with low pretest individual interest. Neither the intervention nor the interest variable predicted course performance. In utility-value reflection responses, we catalogued themes aligned with a range of task-value components beyond utility-value. Our results reinforce previous work indicating that utility-value reflections support low individual interest students in developing academic motivation.