Major Nutritional Metabolic Alterations Influencing the Reproductive System of Postpartum Dairy Cows

Early successful conception of postpartum dairy cows is crucial in determining the optimum reproductive efficiency and profitability in modern dairy farming. Due to the inherent high production potential of modern dairy cows, the extra stress burden of peri-parturient events, and associated endocrine and metabolic changes causes negative energy balance (NEBAL) in postpartum cows. The occurrence of NEBAL is associated with excessive fat mobilization in the form of non-esterified fatty acids (NEFAs). The phenomenon of NEFA mobilization furthers with occurrence of ketosis and fatty liver in postpartum dairy cows. High NEFAs and ketones are negatively associated with health and reproductive processes. An additional burden of hypocalcemia, ruminal acidosis, and high protein metabolism in postpartum cows presents further consequences for health and reproductive performance of postpartum dairy cows. This review intends to comprehend these major nutritional metabolic alterations, their mechanisms of influence on the reproduction process, and relevant mitigation strategies.

Healthy Cattle Microbiome and Dysbiosis in Diseased Phenotypes

: Cattle farming is an ancient practice, with roots in the early Neolithic era that has retained its status in the food industry today, with global beef market revenue amounting to $385.7B, as of 2018. Hence, cattle maintenance is naturally essential to cater to nutritional requirements of modern civilization. This extensive review aims to provide a holistic overview of cattle microbiome, analysing the native microbial composition within respiratory tract, gastrointestinal tract, reproductive tract, and skin. The dysbiosis associated with various diseases such as bovine respiratory disease, bovine digital dermatitis, mastitis, Johne's disease, uterine diseases (metritis and endometritis) and metabolic disorders (ruminal acidosis and ketosis) has been discussed. Moreover, various non-antibiotic microbial therapies including phage therapy, prebiotics and probiotics have been examined as potential means to reduce disease-associated dysbiosis. In general, this review highlights the importance of the microbiome in maintenance of health in cattle and its potential in alleviating bovine diseases, with an aim to enhance cattle health and production.

Prior Forage Type Influences Ruminal Responses to a Wheat Grain Challenge in Lactating Dairy Cows

To increase the dry matter and metabolisable energy intake of cows, dairy farmers often supplement pasture with concentrates and conserved fodder. Feeding large amounts of highly fermentable concentrates to cows can result in metabolic issues, such as ruminal acidosis, and thus safer but more efficient introduction strategies are desirable. We assessed the role that forages play in ruminal, behavioural and production responses to a wheat grain challenge in dairy cows with no previous wheat adaptation. Multiparous lactating Holstein dairy cows (n = 16) were fed a forage-only diet of either lucerne (Medicago sativa) hay, perennial ryegrass (Lolium perenne L.) hay or one of two cultivars of zero-grazing fresh perennial ryegrass herbage (Bealey or Base), for 3 weeks. The forage diet was then supplemented with crushed wheat grain at 8 kg dry matter/cow day−1, with no adaptation period. Wheat comprised between 32 and 43% of total dry matter intake. Cows fed hay maintained a higher mean ruminal fluid pH than those fed herbage, on both the forage-only diet (6.43 vs. 6.17) and the forage plus wheat diet (6.03 vs. 5.58). Following supplementation of wheat, cows fed herbage exhibited minimum ruminal fluid pH levels indicative of acute ruminal acidosis, at 5.15 and 5.06 for cultivars Bealey and Base, respectively. Furthermore, for both herbage cultivars, adding wheat resulted in a ruminal fluid pH under 6 for >20 h/day. The ruminal environment of cows fed lucerne hay remained most stable throughout the grain challenge, spending the least amount of time below pH 6.0 (9.0 h/day). Hay created a ruminal environment that was better able to cope with the accumulation of acid as wheat was digested. A combination of increased ruminating time and a slower rate of fermentation, due to higher neutral detergent fiber and lower metabolisable energy concentrations in the hays, is likely responsible for the higher ruminal fluid pH values. Forage plays a critical role in wheat introduction strategies; aggressive adaptation strategies could be implemented when a hay such as lucerne is used as the base forage.

323 Effect of an Acidogenic Diet with Phytogenic Supplementation on in Situ Degradability of Corn and Wheat Grain, and Grass Silage in Dairy Cows

Modern dairy production systems require larger inputs of energy in diets to increase milk yield. Therefore, dairy cows are at risk of experiencing subacute ruminal acidosis (SARA). The objective of this study was to evaluate grains and forage rumen degradability in cows fed different diets supplemented with a phytogenic (PHY) feed additive. The experiment was conducted with nine rumen-cannulated non-lactating Holstein cows blocked in two groups of four and five animals, and were part of a cross-over design. This study consisted in 2 runs separated by a 12-week washout period, in which cows grazed on pasture. Each experimental run had one week of forage (F) feeding, one week of transition to a high grain (HG) diet, and four weeks of HG (65:35 concentrate to forage ratio in dry matter basis). Cows were supplemented with PHY (a blend of menthol and thymol) or a control carrier (CON) from week F. Corn and wheat grain were ground through a 4 mm screen, while grass silage was ground through a 6 mm screen. Sampling for in situ degradability was performed in F and in week four of HG diet. Data were analyzed with SAS with week of feeding and supplementation as fixed effects and cow as random effect. Corn and wheat 24-h dry matter (DM) and organic matter (OM) degradability increased during HG diet compared with F (P < 0.05), grass silage DM and OM 48-h degradability was reduced by HG diet compared to F (P < 0.01). Additionally, wheat grain 24-h OM degradability was higher for PHY compared to CON under F and HG diet conditions (P = 0.05). Overall, diet composition and SARA conditions can influence grains and fiber degradability in the rumen.

325 The Diagnosis of Sub-acute Ruminal Acidosis (SARA) in Dairy Cows on Commercial Farms Using the Milk Fatty Acid Profile

The accuracy of the milk fatty acid profile as a diagnostic tool for the diagnosis of sub-acute ruminal acidosis (SARA) has been determined when SARA was experimentally induced. This had not yet been done not on commercial dairy farms, where SARA can occur naturally. The objective of this study was to determine this accuracy in individual cows on commercial dairy farms. A total of 336 cows from 24 commercial dairy farms in Quebec were included. Farms were blocked based on geographical location and management, with each block having one high risk SARA farm and one low risk SARA farm. Farm Risk of SARA was determined based on the milk fat content and the proportions of de novo fatty acids and long chain unsaturated fatty acids in the bulk tank. On each farm, 7 early/mid-lactation (< 150 days in milk DIM) and 7 mid/late lactation (< 150 DIM) cows were randomly selected. The fatty acid profile of pooled milk samples from these cows were determined by gas chromatography. Farm risk of SARA did not affect the milk fat proportion of fatty acids, with the exception of trans 10 cis 12 C18:2, which was higher in At Risk Farms. Later lactation cows had a higher milk fat content and higher milk fat proportions of de novo, C16 fatty, and odd and branch chain fatty acids. The prevalence of SARA was likely higher in earlier lactation cows than in later lactation cows, but non-SARA related animal and dietary factors also affect the milk fatty acid profile. Hence, the milk fatty acid profile alone may not be accurate enough to diagnose SARA on farm. This profile can, however, contribute to this diagnosis, the identification of causes of milk fat depression, and the development of strategies to optimize the milk fatty acid profile.

307 Effect of Feeding Distilllers Grain from Wheat on Growth Performance of Growing and Finishing Beef Cattle

The uniqueness of wheat-based distiller grain (wDG) with high protein and digestible fibre gives great feeding opportunities for cattle as energy, protein or fiber source. This abstract summarizes recent research findings on the use of wDG in beef cattle diets. For growing beef cattle, steers fed diets (forage:concentrate, 55:45) with increasing replacement of barley grain with wDG from 0, 8, 16, 24 to 32% (DM basis) linearly (P < 0.01) increased average daily gain (ADG) from 1.09 to 1.28 kg/d and DM intake (DMI) from 7.26 to 7.94 kg/d without affecting gain:feed (0.158). By comparing protein source of canola meal and corn DG in diets containing 60% of silage and 40% of barley grain, steers fed wDG diet had similar ADG (1.46 kg/d) with corn DG (1.51 kg/d), and had no differences in gain:feed (0.178) with canola meal (0.183). For finishing beef cattle, with increasing wDG from 10, 20 to 40% in the place of barley grain of finishing diets, the DMI linearly (P < 0.01) increased from 10.2 to 10.9 kg/d, whereas, the gain:feed linearly (P < 0.01) decreased from 0.172 to 0.159 without altering the ADG (1.74 kg/d). The wDG was also suggested to be fed as fiber source to replace roughage in finishing diet. Entirely substitution of wDG for roughage of finishing diet decreased (P < 0.01) ruminal pH from 5.95 to 5.75 of beef heifers; however, the ADG and gain:feed of steers were not affected. The results suggested that although substitution of wDG for roughage in finishing diets may increase the incidence of ruminal acidosis, this outcome does not appear to adversely impact the performance of the cattle. The wDG can be successfully incorporated to substitute a portion of grain or roughage within growing and finishing diets with minimal or no adverse impact on cattle growth performance.

Alfalfa preservation methods and use in ruminants’ diet

В статье представлены материалы, характеризующие основные способы консервирования люцерны, такие как заготовка на сено, сенаж и силос. Консервирование — это процесс создания условий, которые подавляют рост и активность патогенных микроорганизмов. Люцерна важна для животных из-за высокого содержания белка и аминокислот, но нуждается в эффективных методах консервирования с тем, чтобы использоваться крупным рогатым скотом в течение всего года. В обзорной статье авторами отмечается важность заготовки кормов в оптимальные сроки созревания растений для снижения уровня сырой клетчатки и повышения переваримости питательных веществ. По данным зарубежных исследователей, большое значение для сохранности питательных веществ корма имеет содержание влаги: в сене — не более 15%, в силосе — 45–65% и в сенаже — 35–40%. В настоящем обзоре представлены сведения о важности использования при заготовке корма консервантов, таких как бактериальные инокулянты и химические вещества, для ингибирования нежелательных микроорганизмов. В статье рассматривается значительное влияние люцерны и кормов из неё в качестве единственного корма на увеличение потребления сухого вещества, переваримость питательных веществ, прирост живой массы, утилизацию азота, удой молока, более полноценный состав жирных кислот в мышцах животных, а также на значительное снижение выбросов СН4 и снижение риска развития руминального ацидоза. Люцерна — наиболее перспективный корм для животных, поэтому основное внимание следует уделять факторам, влияющим на процесс консервирования и использования консервантов для лучшей сохранности питательных веществ. This article deals with the production of hay, haylage and silage from alfalfa. Preservation is a process preventing growth and activity of pathogenic flora. Alfalfa is a valuable crop due to high concentrations of protein and amino acids. However, effective preservation techniques are required allowing its availability throughout the year. To reduce crude fiber content and increase nutrient digestibility plant material should be harvested at optimal times. According to foreign literature water content has the most significant impact on feed nutritional value: in hay — up to 15%, silage — 45–65%, haylage — 35–40%. Bacterial strains and chemicals have the ability to inhibit the spread of pathogenic microorganisms and are the most common preservatives. Including alfalfa in livestock diet positively affects dry matter consumption, nutrient digestibility, weight gain, nitrogen utilization, milk yield, fatty acid composition in muscles but at the same time significantly reduces СН4 emission and the risk of ruminal acidosis. Alfalfa is the promising forage and therefore, its preservation needs to be accurately performed to maintain its nutritional value.