Association of cow, feeding, and environmental conditions with milk performance in organic dairies, rumen-protected amino acids supplementation in mid-lactation cows, and feeding practices management in Brazilian dairies
Authors:   , Abreu Marcelo de Barros 
Published: December 2022

Our objectives with this study were 1) evaluate the effects of lactation number, somatic cells count (SCC), season, production system, and breed on milk yield (MY), and fat and protein milk concentrations of cows in organic herds, 2) evaluate the effects of supplementing methionine (Met) and lysine (Lys) as rumen-protected AA on milk yield and composition of mid-lactating Holstein cows in a commercial dairy feeding a low-forage diet, and 3) gather information of feeding practices in Brazilian dairies and identify whether those practices are associated with herd milk production level. In the first study, a Wood model was used to fit an average lactation curve for MY and milk fat and protein from a data set containing individual monthly cow’s milk test days from 14 organic dairies collected between 2012 to 2015. Overall, MY and milk fat and protein were affected by lactation number, breed, feed condition, season, and somatic cell count. Greater milk yield was found for cows in the fourth lactation, for Holstein cows, in the winter and spring season, and for cows under grazing feed conditions, and for cows with low SCC. In the second study, a total of 314 multiparous cows were randomly assigned to control [CON; 107 g of dry distillers grains (DDG)] or rumen protected Met and Lys (RPML; 107 g DDG + 107 g of RPML). Throughout 42 d of study, cows were grouped in a single dry lot pen and fed the same TMR diet twice daily. Milk components from a.m. and p.m. milkings were determined from samples collected at d 0, 14, 28, and 42 of the study. Treatments effects were evaluated at the cow-level considering milk yield and composition taken at baseline (1 wk before the experiment) as a covariate in the models. Clinical mastitis risk was assessed by Poisson regression. Plasma Met increased (26.9 vs. 36.0 µmol/L), and Lys tended to increase (102.5 vs. 121.1 µmol/L) with RPML supplementation. Cows supplemented with RPML had higher milk yield (46.0 vs. 45.4 kg/d); however, milk components yield and concentration were not affected by RPML supplementation. Although somatic cell count was not affected by RPML supplementation, the risk of clinical mastitis was 0.39 times lower for RPML than CON cows (95% CI: 0.17-0.90). Results suggest that RPML supplementation increased milk yield and decreased the risk of clinical mastitis in mid-lactation cows. In the third study, an online survey was performed to assess Brazillian dairy farmers' most common feeding practices in confined systems. The survey consisted of 38 questions divided into 4 sections to assess feeding practices performed in high milk- production pens. The questionnaire was mailed to 500 dairy producers, and 135 responses (27.6%) were returned. After data screening, the remaining 82 responses were analyzed. From the 82 responses, 56 (68%) and 26 (32%) were answered by the dairy manager and nutritionists, respectively. Dairies were categorized according to their 305-day milk production (kg) as low production (LP; <7,000; n = 27), medium production (MP; 7,000 to 10,000; n = 35), and high production (HP; >10,000; n = 20). Overall, herd size averaged 175 lactating dairy cows containing Holstein (n = 52; 63%), Holstein × Gyr (n = 22; 27%), and Jersey (n = 8; 10%) herds. High production cows were housed on compost barn (n = 42; 51%), dry lot (n = 24; 29%), and free- stall (n = 16; 20%). The HP and MP herds had a greater risk ratio to have a trough wash protocol than LP herds. The HP herds had a greater risk ratio to evaluate TMR physically effective fiber NDF (peNDF) than LP herds. The MP herds had a greater risk ratio to measure feed efficiency, check forage dry matter (DM), and evaluate corn processing compared to LP herds. The risk ratio was not different among the 3 herds groups regarding the use of mixer wagon, evaluating TMR DM, evaluating particle size distribution, calibration of the wagon scale, use of TMR stabilizers, feedstuffs composition analysis, feed after milk time, feed push-ups, feed bunk cleaned-up, and feed for refusals, have employee´s training protocol, group primiparous separately from multiparous, and have a colling system. Althougt most of risk ratio were similar between herds, the HP and MP herds had greater frequencies on the most feeding practices compated LP herds. In summary, survey results can be used to develop and disseminate target information on feeding practices and feed bunk in Brazilian dairies. Keywords: Organic milk production. Rumen-protected amino acids. Feed bunk practices.