The Importance of B Vitamins in Enhanced Precision Nutrition of Dairy Cows: The Case of Folates and Vitamin B12

Dairy cow diets are generally balanced for energy and major nutrients with B vitamins generally assumed not to be limiting, in spite of their role as coenzymes, essential to many metabolic reactions in protein, carbohydrate and lipid metabolism. Assuming adequacy of B-vitamin supply may explain some of the discrepancies between the outcomes of metabolic prediction models and measured cow performance. In lactating dairy cow, the amount of B vitamins from the diet and synthesized by the ruminal microbiota is generally sufficient to prevent deficiency symptoms and, as such, is assumed to fulfill requirements. However, reports of beneficial effects of B-vitamin supplementation on dairy cow performance suggest that B-vitamin supply is sometimes lower than its needs, as an insufficient B-vitamin supply decreases metabolic efficiency by driving a shift towards alternative metabolic pathways with greater energy cost. Using information on folates and vitamin B12 illustrated how meeting dairy cow needs for B vitamins should not be overlooked in formulation of rations for lactating dairy cattle. The present review discusses current knowledge and indicates areas presently impeded by the lack of research results, especially the limitations on the ability to estimate B vitamin need and supply.

Effects of housing beef cow-calf pairs on drylot or pasture in the Midwest on production parameters and calf behavior through feedlot receiving

The objectives were to analyze the effects of housing cow-calf pairs in drylots (DL) or pasture (PAST) on cow performance and reproduction as well as calf performance and behavior through feedlot receiving. Simmental × Angus (2 yr; 108/yr; 81 ± 15.3 d postpartum) spring-calving cows were stratified by age, body weight (BW), body condition score (BCS), and calf sex and allotted to 6 groups/yr. Groups were randomly assigned to 1 of 2 treatments: DL or PAST. Cows in DL were limit-fed at maintenance and calves had ad libitum access to the cow diet in an adjacent pen. Pairs on PAST were rotationally grazed and calves received creep ad libitum three weeks prior to weaning. On d 110 calves were fence-line weaned and behavior was observed on d 111 and 112. On d 116 calves were transported 272 kilometers to a feedlot for a 42-d receiving period. Behavior was evaluated again on d 117 and 118. Data were analyzed using the MIXED procedure of SAS except reproductive data which was analyzed using the GLIMMIX procedure. Cows on DL had greater (P ≤ 0.01) BW and BCS at weaning. There were no differences (P ≥ 0.42) detected in reproductive data. Cows on DL had greater (P = 0.02) milk production. Calves on DL had greater BW (P ≤ 0.01) on d 55 and at weaning and greater preweaning average daily gain (ADG). There were treatment × time effects (P = 0.01) for lying and eating on d 111 and 112. More DL calves were eating in the morning and lying in the evening. More (P < 0.01) PAST calves were walking on d 111. Pasture calves vocalized more (P ≤ 0.01) on d 112. On d 117, more (P ≤ 0.05) pasture calves were lying and eating, and DL vocalized more. On d 118, treatment × time and treatment effects were detected (P ≤ 0.02) for lying and walking. More PAST calves were lying and more DL calves were walking. Drylot calves had greater (P ≤ 0.02) BW at the beginning and end of the receiving phase. Pasture calves had greater (P < 0.01) ADG and tended (P = 0.10) to have greater gain efficiency during feedlot receiving phase. In conclusion, housing cow-calf pairs in drylots improved BW, BCS, and milk production of cows but did not affect reproductive performance. Drylot calves had increased BW and ADG during the preweaning phase. Calf behavior at weaning and receiving was influenced by preweaning housing. Pasture calves had improved receiving phase ADG and feed efficiency but were still lighter than drylot calves after 42 d receiving phase.

143 Effect of Supplementary Selenium Source on Dairy Cow Performance, Antioxidant Status, and Apparent Absorption and Retention

The objective of this experiment was to determine how source of selenium (Se) affects dairy cow performance, antioxidant status, and apparent absorption and retention. Multiparous Holstein cows (n = 24; 597 ± 49 kg BW) were blocked by days in milk (161 ± 18) and randomly assigned to receive 0.3 mg/kg of either: 1) organic Se (selenized yeast; ORG; Sel-Plex-Alltech); or, 2) inorganic Se (sodium selenite; INO) premix, top dressed and mixed into a ration daily. After an 11-week adaptation period (blood and milk sampled monthly), cows received an intraruminal dose of Se77 (either Se77 yeast or NaSe77O3) followed by a 4-day period of blood and rumen fluid sampling, and total collection of feces, urine, and milk. Data were analyzed using PROC GLIMMIX in SAS with fixed effects of treatment, time, and their interaction, and random effect of block. Daily DMI (23 ± 0.6 kg), milk yield (35 ± 1.2 kg), plasma glutathione peroxidase (64 ± 4.2 U), and serum Se (0.11 ± 0.003 µg/g) were not different between treatments during the adaptation period. Serum Se77 maximum concentration and area under the curve (AUC) were not different between treatments for 72 hours following infusion, but rumen fluid Se77 AUC was higher (P = 0.02) for ORG cows. Apparent absorption (64 ± 1.3%) and retention (44 ± 1.5%) of the Se77 dose did not differ between treatments. The ORG cows had lower urinary excretion (13 vs. 17 ± 0.6%; P < 0.01), higher milk excretion (6 vs. 2 ± 0.3%; P < 0.01), and similar fecal excretion (36 ± 1.3%; P = 0.9) of Se77 compared to INO cows. These results indicate that ORG Se increased Se content of milk and decreased Se excretion in urine, but did not alter performance, antioxidant status, and apparent absorption and retention of Se in mid-lactation cows.

321 Extrusion of Grass Silage Increase Intake and Milk Yield in Dairy Cows

This research evaluated effects of grass silage extrusion on dairy cow performance. A grass dominated (70% timothy, 26% meadow fescue, 3% red clover and 1% undefined) first cut ley was harvested on June 13, 2019, and 10 days later near Uppsala, Sweden (58°83′ N, 17°82′ E). Crops were wilted (45% DM for early cut, 50% DM for late cut), round baled and wrapped into plastic film for ensiling. At feeding out, bales were chopped in a TMR feeder, and a portion was processed in an extruder, where screws shear the material under pressure, for further particle size reduction and cell wall break up. Eight Swedish Red cows in two blocks (4 ruminally fistulated, 143 ± 38 DIM and 4 intact, 68 ± 10 DIM) were used in a Latin square design experiment with 4 periods of three weeks each and 4 treatments. The 2x2 factorial arrangement of treatments included silage from early or late harvest that was chopped or extruded. Silage was fed separately ad libitum and supplemented (daily amounts on an as fed basis) with 2 kg of soybean meal, a compound feed (6 kg for fistulated and 8 kg for intact cows), and 120 g of a mineral mix. Extrusion increased silage DMI (1.8 kg/d, P < 0.001) with greater effect at late harvest (P = 0.021 for interaction between processing and harvest) and milk yield (1.8 kg ECM/d, P = 0.004) with a tendency to greater effect at late harvest (P = 0.055). Extrusion depressed total tract OM digestibility (2.3 percentage points, P < 0.001), eating time (0.5 h/d, P = 0.014), rumination time (2.0 h/d, P < 0.001) and rumen pH (0.1 units, P = 0.008). Extrusion improves intake and milk production in dairy cows, despite depressed digestibility.

PRINCIPLES OF FORMING A REFERENCE DATABASE TO ASSESS THE REEDING VALUE OF CATTLE

Проведены исследования по результативности линейной оценки телосложения (ОТТ) в зависимости от источника учетной информации. Установлено, что результаты оценки типа телосложения молочных коров представителями собственников племенных животных на 2 категории выше в сравнении с результатами ОТТ, полученными в ходе работы независимых бонитеров (классификаторов). Допуск представителей собственников племенных животных к оценке ОТТ коров собственных стад привносит элементы субъективизма в оценку экстерьера молочных коров, не обеспечивает в должной мере получение достоверной информации о качестве племенной продукции и негативно влияет на результативность комплексной оценки племенной ценности молочного скота. В Архангельской области принято решение об официальном использовании данных ОТТ коров, полученных только в ходе работ независимых бонитеров. Ручной ввод данных по ОТТ коров и их корректировка на уровне хозяйств региона закрыты для пользователя. Участие представителей собственников племенных животных в оценке типа телосложения коров в селекционируемых стадах является основным сдерживающим фактором в становлении отечественной службы бонитеров и искажает реальную племенную ценность оцениваемых животных. At the present time in the system of organization of pedigree work with dairy cattle of Russia new normative legal base of branch is being prepared. The main goal of conducted work is creation of highly reliable data bases for organization of complex evaluation of breeding value of breeding groups of controlled animals. In connection with the fact that the newly developed Russian system of complex evaluation of breeding value of dairy cows will include data on evaluation of their exterior appearance, obtained by the system of linear evaluation of body type (BTB), we have conducted research on the performance of BTB depending on the source of accounting information. It was found that the results of evaluation of body type of dairy cows by representatives of breed owners are two categories higher in comparison with the results of OBT obtained in the work of independent bonifiers (classifiers). Allowing representatives of pedigree animal owners to evaluate body type of cows in their own herds introduces elements of subjectivity in evaluating the exterior of dairy cows and does not provide reliable information about the quality of pedigree products, which in turn can negatively affect the effectiveness of comprehensive evaluation of the pedigree value of dairy cattle. At the regional level (Arkhangelsk Region) there was made a decision to officially use data on cow sow performance evaluation, which was obtained only in the course of independent bonifiers' work. At the same time, manual entry of data on cow performance data and its adjustment at a farm level in the region is closed to the user. Participation of the representatives of breeding animals owners in the evaluation of body type of cows in breeding herds is the main restraining factor in the establishment of national bonifers service and distorts the real breeding value of the evaluated animals.

Nitrate supplementation at two forage levels in dairy cows feeding: milk production and composition, fatty acid profiles, blood metabolites, ruminal fermentation, and hydrogen sink

Nitrate may reduce the ruminal methane emission by competing methanogenesis to achieve more hydrogen. For this purpose, twenty Holstein lactating cows were examined using a 2×2 factorial design in 4 groups for 60 days with two forage levels (40% and 60%) and supplemental nitrate 0% (F40 and F60) and 3.5% (F40N and F60N) of diet dry matter (DM). Then, the effect of nitrate and forage levels on cow performance, ruminal fermentation, methane emission, and metabolic hydrogen sink were evaluated. The nitrate supplementation did not significantly affect milk yield and ECM/DMI while, milk urea nitrogen was increased. Lowest quantity of milk vitamins (A and E) was observed in nitrate groups. The nitrate supplementation increased c9-C18:1, unsaturated fatty acids, and n-6/n-3 contents of the milk. Blood parameters were affected by nitrate supplementation. Blood met-Hb concentration was increased, while blood glucose was decreased in nitrate groups. High forage and nitrate fed animals (F60N) had higher ruminal acetate and lower propionate concentration, and higher acetate+butyrate to propionate ratio than other groups. Nitrite and NH3-N concentrations were higher in the rumen of nitrate fed animals. Nitrate supplementation inhibited gas volume and methane emission without affecting volatile fatty acids at 12 and 24 h of incubation. The H2 balance, H2 production and consumption, and recovery percentage were significantly lower in F60N group. In conclusion, nitrate supplementation can be employed as an alternative strategy for improving ruminal fermentation, milk quality and methane inhibition.

Effects of supplements differing in fatty acid profile to late gestational beef cows on cow performance, calf growth performance, and mRNA expression of genes associated with myogenesis and adipogenesis

Background Maternal nutrition during gestation affects fetal development, which has long-term programming effects on offspring postnatal growth performance. With a critical role in protein and lipid metabolism, essential fatty acids can influence the development of muscle and adipose tissue. The experiment investigated the effects of late gestation supplements (77 d prepartum), either rich in saturated and monounsaturated fatty acids (CON; 155 g/cow/d EnerGII) or polyunsaturated fatty acids (PUFA; 80 g/cow/d Strata and 80 g/cow/d Prequel), on cow performance and subsequent calf growth performance as well as mRNA expression in longissimus muscle (LM) and subcutaneous adipose tissue at birth and weaning. Results There was no difference (P ≥ 0.34) in cow body weight (BW) or body condition score from pre-supplementation through weaning. Relative concentrations of C18:3n-3 and C20:4n-6 decreased (P ≤ 0.05) to a greater extent from mid-supplementation to calving for PUFA compared with CON cows. Cow plasma C20:0, C20:5n-3, and C22:6n-3 were increased (P ≤ 0.01) in PUFA during supplementation period. At birth, PUFA steers had greater (P = 0.01) plasma C20:5n-3. No differences (P ≥ 0.33) were detected in steer birth BW or dam milk production, however, CON steers tended (P = 0.06) to have greater pre-weaning average daily gain and had greater (P = 0.05) weaning BW compared with PUFA. For mRNA expression in steers: MYH7 and C/EBPβ in LM increased (P ≤ 0.04) to a greater extent from birth to weaning for PUFA compared with CON; MYF5 in LM and C/EBPβ in adipose tissue tended (P ≤ 0.08) to decrease more from birth to weaning for CON compared with PUFA; SCD in PUFA adipose tissue tended (P = 0.08) to decrease to a greater extent from birth to weaning than CON. In addition, maternal PUFA supplementation tended (P = 0.08) to decrease MYOG mRNA expression in LM and decreased (P = 0.02) ZFP423 in adipose tissue during the pre-weaning stage. Conclusions Late gestation PUFA supplementation decreased pre-weaning growth performance of the subsequent steer progeny compared with CON supplementation, which could have been a result of downregulated mRNA expression of myogenic genes during pre-weaning period.