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At least 19 recordsLinked to original sources
PubMed1977

[Productive life-span of dairy cows and its economic significance. I. Disposal of dairy cows: the current situation (author's transl)].

The current situation regarding the replacement of dairy cows is discussed. Attention is successively paid to the duration of herd life and the replacement rate, the reasons for disposal and the relationship between age and the probability of disposal. Little research including all the required elements at the same time has been done in this field. Therefore, the literature can offer only a rough idea of the current situation regarding the replacement of dairy cows (Tables 1 and 2). Further research along a few lines presented in this paper is advocated. However, the findings derived from the literature may be used in an economic model to quantify the economic significance of differences in the herd life of dairy cows. This subject will be elaborated in two subsequent papers.

Animals↗
PubMed1977

Estimation of the prevalence of udder infection in dairy herds based on a single-quarter sample from each cow in the dairy herd.

Individual quarter milk samples were taken from 719 cows in 7 dairy herds and examined for mastitis-causing pathogens. Analyses were made to ascertain the prevalence of mastitis infection when the results from a single quarter were compared with those from all 4 quarters. There was a very close similarity between the 2 methods of assessment. When the number of samples is limited, sampling of a single quarter instead of all 4 quarters permits more cows to be examined.

Animals↗
PubMed1977

[Productive life-span of dairy cows and its economic significance. II. The replacement of dairy cows: an economic model (author's transl)].

A model, initially based on the work of Zeddies (10), is presented , by which the economic aspects of the replacement problem may be studied. First, the principle underlying the replacement decision is discussed. Then, the data to be included in the model are determined. This mainly concerns the elements associated with age, such as milk production, the value of newborn calves, the slaughter of the cows, the feed cost and the cost of a pregnant heifer just before calving. The age-associated probability of culling is also included in the model. A number of questions regarding the economic importance of the duration of herd life have been studied using this model. In the third paper, the results of this application of the model will be presented.

Animal Feed↗
PubMed2026

Isolation, identification, and genomic characterization of Staphylococcus aureus phage vB_SauL_202595 and its bacteriostatic application in dairy products.

Staphylococcus aureus is an important pathogen associated with bovine mastitis and dairy product contamination, posing economic and public health risks through the food chain. In this study, a temperate phage, vB_SauL_202595, was isolated from a dairy farm environmental sample using S. aureus SHZ-0127 as the host, and its biological characteristics, genomic features, and antibacterial activity in dairy matrices were evaluated. vB_SauL_202595 lysed 18 of 66 tested S. aureus strains, with a lysis susceptibility rate of 27.3%, including 5 highly susceptible strains, indicating a relatively limited host range. The optimal multiplicity of infection was 0.01, the latent period was approximately 30 min, and the burst size was approximately 316 PFU/cell. The phage remained stable at 4°C-37°C and pH 6-10. Genome analysis showed that vB_SauL_202595 belongs to the class Caudoviricetes, has a genome of 44,503 bp with 33.59% GC content, and encodes 63 predicted proteins. No typical antibiotic resistance genes or major virulence factors were detected; however, integrase and repressor genes were identified, supporting its temperate nature. vB_SauL_202595 inhibited S. aureus SHZ-0127 growth, reduced mature biofilm biomass, and decreased viable bacterial counts in milk and yogurt, with reductions of 1.23 and 1.42 log10 CFU/mL under representative conditions, respectively. From a One Health perspective, these findings provide foundational evidence for reducing S. aureus contamination and related antimicrobial resistance risks along the dairy chain. Overall, vB_SauL_202595 represents a candidate phage resource for dairy-associated S. aureus biocontrol research, but its limited host range and lysogeny-related genes require further safety assessment before food-related applications.IMPORTANCEStaphylococcus aureus is a major pathogen associated with bovine mastitis and a common contaminant in dairy products, causing economic losses and public health risks through the food chain. Although phage-based biocontrol has emerged as a promising strategy for controlling S. aureus contamination in dairy products, systematic evidence regarding phage activity in actual dairy matrices remains limited. In this study, we isolated and characterized a dairy farm environment-derived temperate phage, vB_SauL_202595, and evaluated its biological characteristics, genomic features, host range, stability, biofilm removal ability, and antibacterial performance in milk and yogurt. These findings provide foundational experimental evidence for phage-based dairy biocontrol against S. aureus. However, due to its limited host range and lysogeny-related genomic features, vB_SauL_202595 should be considered a candidate phage resource for further study. Broader validation, including phage-cocktail testing, long-term storage assays, product quality assessment, and regulatory safety evaluation, is needed before practical application.

Staphylococcus aureus↗
PubMed2026

Comparative analysis of rumen metagenomes with dietary supplementation of 3-nitrooxypropanol revealed divergent modes of action in hydrogen metabolism and reductant pathways between beef and dairy cattle.

BACKGROUND: The compound 3-nitrooxypropanol (3-NOP), an inhibitor of methyl-coenzyme M reductase (MCR), reduces enteric methane production in both beef and dairy cattle. Although the proposed mechanisms of 3-NOP involve on inhibiting the activity of MCR in vivo, it is unknown how this process could affect rumen microbiome as a whole and if it differs between beef and dairy cattle. This study conducted a comparative analysis of the rumen microbiome and its functional shifts in four different cattle studies (two beef and two dairy cattle studies) that evaluated 3-NOP supplementation using metataxonomics and metagenomics. RESULTS: Comparative analysis of 281 rumen metataxonomic datasets (143 beef and 138 dairy cattle) revealed that dietary supplementation with 3-NOP affected rumen bacteria and methanogens. Further, comparative analysis of 54 metagenomic datasets (24 beef and 30 dairy cattle) revealed that 3-NOP inhibited mcrA, decreased the abundances of Methanobrevibacter gottschalkii and the protozoal species Isotricha prostoma, while increased the abundances of Methanobrevibacter ruminantium and Methanosphaera sp., Prevotella sp. was a significant bacterial taxon in both beef and dairy cattle, contributing to various pathways such as propionate and butyrate production. Its increased abundance after 3-NOP supplementation may also be linked to the decrease in Isotricha prostoma. Hydrogenotrophic methanogenesis decreased after 3-NOP supplementation with the abundance of genes involved in methylenetetrahydromethanopterin dehydrogenase decreased in beef cattle, while that of 4Fe-4S ferredoxin gene decreased in dairy cattle. The abundance of protozoal Polyplastron multivesiculatum increased after long-term 3-NOP supplementation in beef cattle, potentially due to changes in hydrogen (H2) partial pressure. During 3-NOP-mediated methanogenesis reduction, abundance of genes encoding methanogenic hydrogenase and H2 producing hydrogenase were decreased, while those encoding H2 sensory hydrogenase increased. Acyl-CoA dehydrogenase gene involved in propionate and butyrate production pathways increased in both beef and dairy cattle, while nitrite reductase increased specifically in beef cattle, indicating a rise in alternative H2 sinks. Video Abstract CONCLUSION: Our findings revealed broad effects of 3-NOP on rumen microbiome and functions in vivo, with varied effects in beef and dairy cattle, which provide mechanistic insights into the supplementation of 3-NOP in both beef and dairy cattle, supporting its more sustainable and effective use in the future.

Metagenome↗
PubMed1978

[Economic evaluation of the method of gradual formation of groups of dairy cows from primiparae free of infectious mastitis].

Employing the turnover of a dairy-cow herd with primiparas to control infectious mastitis is beneficial because young dairy cows, as a rule free of inflammations of the mammary gland, are not included among dairy cows already infected or suspected of being infected and so it is possible to form groups of dairy cows free of mastitis. For this intention an agricultural enterprise was chosen in potato production region I. In the given period 316 to 336 dairy cows of Bohemian Spotted breed were followed. To express the impact of the infection on the milk efficiency and to draw economic conclusions on the efficiency of treating infectious mastitis we observed the total milk yield of the different dairy cows in one lactation. In the given enterprise unsuccessful treatment of an infected dairy cow in three lactations resulted in a total loss of 4,648 Kcs. Therefore from the economic aspect it appears to be profitable to replace productive, but ill, older dairy cows by healthy first-calvers because the negative effect of the mastitis on the production of milk increases with every successive lactation.

Animals↗
PubMed1992

[Biologic quality of colostrum and calves from dairy cows injected with zinc during pregnancy].

The effects of an administration of the Zindep inj. preparation (Biotika) were evaluated in pregnant dairy cows as exerted on specific weight, total protein (TP) content, total immunoglobulin (IgC) and albumin (ALB) contents in colostrum. These parameters were also followed: calf's health, live weight, leucocyte (Lc) counts, T-lymphocyte (T-Ly) counts, contents of TPs, IgCs and ALBs in the blood serum of calves. Zinc concentrations were determined in colostrum, milk and calf blood serum. Our observations included 16 dairy cows in the seventh month of pregnancy in the second lactation and their calves in the winter feeding season. Eight experimental dairy cows were treated with the Zindep preparation in form of an injection to the neck muscles at a dose of 3 mg Zn/kg live weight in the mid-seventh month of pregnancy. Blood samples were taken from v. jugularis from all calves before their first drinking, on days 5, 15 and 30 of age. Colostrum, and/or milk samples were obtained by drawing of the colostrum or milk from the udder quarters within 60 minutes after parturition, on days 5 and 15 of lactation. Zn levels at birth were 16.48 +/- 2.67 mumol/l in experimental calves and 13.84 +/- 3.19 mumol/l in control calves. Zincaemia decreased slightly in both groups on days 5 and 15 of age, but it was insignificantly higher in calves coming from Zindep-treated dairy cows. Zn levels in the blood serum on the 30th day of age were 18.45 +/- 2.44 mumol/l in experimental animals and 15.73 +/- 3.11 mumol/l in control animals. Zn content in the colostrum of experimental cows was 2.40 +/- 0.42 mg/l and in the control it was 1088 +/- 0.52 mg/l (P < 0.05). On day 5 of lactation, Zn amounts in the milk of experimental dairy cows decreased to 0.95 +/- 0.12 mg/l and to 0.76 +/- 0.10 mg/l in the control (P < 0.01). Zn levels in the milk of experimental cows on day 15 of lactation were 0.95 +/- 0.13 mg/l and in the milk of control group they were 0.82 +/- 0.14 mg/l. Colostrum specific weight from zinc-treated cows was 1,067.86 +/- 0.75 g/cm3 and 1,056.8 +/- 13.53 g/cm3 in the control. TP and IgC concentrations were 137.81 +/- 38.11 g/l and 110.13 +/- 29.91 U ZST, respectively, in the colostrum of experimental group, and 105.98 +/- 32.02 g/l and 85.53 +/- 25.42 U ZST, resp., in control animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1976

Circulating placental lactogen levels in dairy and beef cattle.

Levels of bovine placental lactogen (bPL) have been measured in the serum of dairy and beef cattle and in the milk and amniotic fluid of pregnant animals with a highly specific radioimmunoassay. In both dairy and beef cows, serum bPL levels remain low (less than 50 ng/ml) during the first two trimesters and then rise rapidly between 160 and 200 days of gestation to a plateau. The bPL levels do not decline prior to parturition. During the last trimester, serum levels in dairy cows, 1103+/-342 ng/ml, are significantly higher than those in beef cattle, 650+/-37 ng/ml (P less than 0.01); furthermore, dairy cows having a high milk production also tend to have high bPL levels. Serum levels are almost twice as high in twin pregnancies and are not correlated with fetal sex or birth weight. bPL levels in milk and amniotic fluid from dairy cattle during the last trimester are approximately 86% and 25% of the serum values, respectively, suggesting that bPL enters these fluids by passive diffusion.

Amniotic Fluid↗
PubMed1977

Vaccination of dairy cattle against Q fever (Coxiella burneti): results of field trials.

A phase I formalin-inactivated Q fever vaccine, using the Nine Mile strain of the organism, was tested for its ability to prevent dairy cows from shedding Coxiella burnetti in their milk. More than 1,400 Holstein-Friesian dairy calves and heifers from 5 dairies were used in field trials lasting over a 3-year period. Vaccination of 476 calves resulted in a geometric mean antibody titer of 1:123.3 compared with 1:2.4 for 486 nonvaccinated calves. The milk samples from 163 vaccinated calves were tested by mouse inoculation after the cows commenced lactation and were placed in their respective milking herds. Of these vaccinated animals, only 2 cows (1%) from 1 herd were suspected shedders, but on subsequent testing gave negative results. Among 164 nonvaccinated (control) cows, 39 (24%) were shedding C burnetii in their milk; this figure corresponded to the prevalence (23%) of shedders in the general population of dairy cows in California. The results of the current field trials indicated that vaccination greatly reduced the shedding of the Q fever organism in the milk of dairy cows.

Animals↗
PubMed2026

Multi-omics revealed the effects of rumen to blood path on early lactation performance in transition dairy cows.

BACKGROUND: The transition period is vitally important to the life cycle of dairy cows. However, the function of the microbiota during both pre- and post-partum and their relationship with ruminal, plasma, and milk metabolites still require systematic investigation. To address this, the 7 highest- and 7 lowest-performing animals among a cohort of 100 dairy cows were selected based on their postpartum energy-corrected milk yield. Rumen fluid and plasma samples were collected during both pre- and post-partum periods, whereas milk samples were obtained postpartum. Shotgun metagenomics of rumen contents in addition to metabolomics of rumen, plasma, and milk samples were performed to evaluate the associations between ruminal microbes and early lactation performance in transition dairy cows. RESULTS: Compared with prepartum cows, postpartum high-yield cows had greater concentrations of ruminal volatile fatty acids and plasma total bile acid. Moreover, plasma urea nitrogen and most amino acids, peptides, and their derivatives in plasma and milk were increased in postpartum high-yield cows, relative to postpartum low-yield cows. Metagenomic analysis revealed that the relative abundances of several species within the Prevotella, Succinimonas, Succinatimonas, and Methanosphaera increased, while other bacteria belong to Alistipes and Bacteroides, and archaeal Methanobrevibacter species decreased in postpartum cows, particularly in postpartum high-yield cows. Co-occurrence network and correlation analysis suggested that Prevotella and Succinatimonas were negatively correlated to Alistipes, Bacteroides, and Methanobrevibacter, potentially contributing to the nutritionally efficient phenotype of postpartum high-yield cows. A metabolic pathway analysis of our metagenomic data revealed that postpartum high-yield cows possessed more microbial genes involved in starch utilization and amino acid synthesis, while a wide range of microbial genes involved in cellulose utilization, acetogenesis, and amino acid degradation were found in prepartum cows with low-yield in postpartum. A structural equation model analysis showed that the increased relative abundances of Prevotella tf.2-5 and Succinatimonas CAG_777 were related to greater concentrations of plasma chenodeoxycholic acid glycine conjugate, milk 5-Methoxytryptophan, and energy-corrected milk yield. Finally, pan-genomic analysis confirmed that Alistipes, Bacteroides, and Methanobrevibacter possess genetic conservation of both hydrogenases and dehydrogenases, which may contribute to energy loss in the rumen via hydrogen dissipation. CONCLUSION: In summary, our findings provide a fundamental understanding of how microbiome-dependent mechanisms contribute to early lactation performance in dairy cows during the transition period. The increased abundance of Prevotella, Succinimonas, and Succinatimonas in postpartum cows suggest that they are important microbes during the transition period and may help in coping with metabolic challenges, while improving nutrient utilization efficiency during this period. Our study underscores the importance of the ruminal microbiome during the transition period and highlights the need for rumen-based nutritional intervention strategies to improve production efficiency in ruminants. Video Abstract.

Animals↗
PubMed1979

Nutritional and healthful aspects of cultured and culture-containing dairy foods.

Nutritional and therapeutic qualities of fermented dairy products are reviewed. Partial hydrolysis of milk constituents (proteins, fats, and lactose) in yogurt, cheese, and other cultured dary foods appears to contribute to their increased digestibility. Lactase and other constituent enzymes of various culturing organisms should contribute to assimilation of lactose by lactose intolerant individuals. Several lactic cultures synthesize certain B-vitamins in fermented dairy products. In contrast, directly acidified dairy products do not exhibit such enhancement in B-vitamins. The hypocholestremic effect of milk is enhanced by fermentation or inclusion of lactic cultures. Lactobacillus acidophilus, Lactobacillus bulgaricus and other lactic organisms produce antimicrobial agents and natural antibiotics. However, production of natural antibacterial substances by different strains of the same species vary widely. These metabolites in cultured dairy products may be responsible for increased shelf life of the foods by inhibiting a wide spectrum of food spoilage organisms. Also, consumption of cultured products containing such natural antibacterial substances may provide the consumer with protection against disease organisms. Unfermented milk containing a specific culture or strain may be consumed to invest organisms for projected beneficial effects.

Animals↗
PubMed2025

Landscape genomics analysis reveals the genetic basis underlying cashmere goats and dairy goats adaptation to frigid environments.

Understanding the genetic mechanism of cold adaptation in cashmere goats and dairy goats is very important to improve their production performance. The purpose of this study was to comprehensively analyze the genetic basis of goat adaptation to cold environments, clarify the impact of environmental factors on genome diversity, and lay the foundation for breeding goat breeds to adapt to climate change. A total of 240 dairy goats were subjected to genome resequencing, and the whole genome sequencing data of 57 individuals from 6 published breeds were incorporated. By integrating multiple approaches such as phylogenetic analysis, population structure analysis, gene flow and population history exploration, selection signal analysis, and genome-environment association analysis, an in-depth investigation was carried out. Phylogenetic analysis unraveled the genetic relationships and differentiation patterns among dairy goats and other goat breeds. Through signal analysis (&#x3b8;&#x3c0;, FST, XP-CLR), we identified numerous candidate genes associated with cold adaptation in dairy goats (STRIP1, ALX3, HTR4, NTRK2, MRPL11, PELI3, DPP3, BBS1) and cashmere goats (MED12L, MARC2, MARC1, DSG3, C6H4orf22, CHD7, MYPN, KIAA0825, MITF). Genome-environment association (GEA) analysis confirmed the link between these genes and environmental factors. Moreover, a detailed analysis of the critical genes C6H4orf22 and STRIP1 demonstrated their significant roles in the geographical variations of cold adaptation and allele frequency differences among different breeds. This study contributes to understanding the genetic basis of cold adaptation, providing crucial theoretical support for precision breeding programs aimed at improving production performance in cold regions by leveraging adaptive alleles, thereby ensuring sustainable animal husbandry.

Environmental adaptation↗
PubMed2026

The Puerperium in the Modern Dairy Cow: A Review.

The puerperium represents a critical physiological period during which the bovine reproductive tract transitions from pregnancy to renewed fertility. In the modern high-producing dairy cow, this transition is challenged by profound metabolic, endocrine, immunological, and structural demands that collectively influence uterine health, ovarian function, and subsequent reproductive performance. This review examines current understanding of the physiology of the puerperium in dairy cattle, with particular emphasis on uterine involution, immune clearance of postpartum contamination, endocrine regulation, and resumption of ovarian cyclicity. Further, it contrasts high-yielding Holsteins with fertility selected dairy populations. Normal uterine involution involves coordinated myometrial contraction, tissue remodelling, endometrial regeneration, and tightly regulated inflammatory responses. Failure of these processes predisposes cows to postpartum uterine disorders, including retained fetal membranes, metritis, endometritis (purulent vaginal discharge with cytological confirmation), and pyometra, which remain major contributors to subfertility and economic loss. Central to the pathophysiology of puerperal disease is negative energy balance, which disrupts immune competence, alters hepatic steroid metabolism, impairs ovarian signalling, and compromises oocyte and embryo quality. Emerging evidence highlights the complex interplay between metabolism, immunity, and the uterine microbiome, shifting current perspectives away from pathogen-centric models toward host resilience. Advances in biomarkers, genomic selection, and precision monitoring offer new opportunities for targeted reproductive management. Ultimately, optimisation of transition period management remains the cornerstone of supporting physiological puerperal recovery and sustaining reproductive efficiency in modern dairy systems.

Animals↗
PubMed2026

Gut microbiota-driven indole-3-propionic acid and kynurenine production is associated with improved metabolic adaptation in periparturient dairy cows.

BACKGROUND: Gastrointestinal microbes convert tryptophan into various bioactive metabolites that influence host energy metabolism; however, these mechanisms are not well understood in periparturient dairy cows, which experience marked metabolic challenges during this period. RESULTS: In this study, we used periparturient dairy cows with rumen and ileal cannulas as in vivo models. Blood, rumen fluid, ileal digesta, and fecal samples were collected at four time points during the periparturient period. By combining metagenome-assembled genomes (MAGs) and targeted metabolite quantification, we&#xa0;characterized microbial tryptophan metabolism and associated metabolite profiles during the periparturient period. The results showed that postpartum cows exhibited significantly increased serum concentrations of triglyceride (TG), aspartate aminotransferase (AST), &#x3b2;-hydroxybutyrate (BHBA), and total bilirubin (T-Bil) compared with prepartum cows, together with decreased levels of several tryptophan metabolites, including indole-3-propionic acid (IPA) and kynurenine (KYN), indicating that tryptophan deficiency might aggravate metabolic disturbances. Metagenomic analysis identified 578 high-quality MAGs, of which 461 contained genes involved in microbial tryptophan metabolic pathways. Among these, the ruminal taxon CAG-791 harbors acdA and contributes to IPA production, whereas the hindgut taxon Treponema_D harbors kynB and promotes KYN formation. Decreases in both taxa were consistent with the reduced levels of these metabolites observed above. In a follow-up in vivo trial with tryptophan supplementation, the abundance of CAG-791 and Treponema_D&#xa0;increased, along with tryptophan-derived metabolites (IPA and KYN), which further partially mitigated metabolic disturbances. CONCLUSIONS: These findings characterize spatial and temporal changes in tryptophan metabolites and gut microbial features in periparturient dairy cows, and provide integrated evidence that alterations in tryptophan metabolism are associated with postpartum metabolic adaptation, thereby supporting the potential of tryptophan-targeted nutritional strategies to improve metabolic health in dairy cows.

Gastrointestinal microbiome↗
PubMed2026

Accounting for voluntary waiting period changes in US dairy herds: Adjusting daughter pregnancy rate and introducing first-service to conception.

The genetic evaluation of female fertility traits in dairy cattle in the United States has progressed over the past 2 decades, with 4 additional traits integrated into the national evaluation system since the introduction of daughter pregnancy rate (DPR) in 2004. However, concerns have arisen in the dairy sector, with reports of producers extending the voluntary waiting period (VWP), which is the time of initial breeding after calving, due to more persistent lactation yields. Since its inception, DPR calculations in the US evaluation have assumed a fixed 50-d VWP, which may not reflect modern reproductive strategies. Furthermore, producers may determine that some of their cows should have their VWP extended while others may follow the standard time. A re-evaluation of the current female fertility evaluation is necessary to ensure traits align with current management practices. Therefore, this study explores the addition of a potential new trait, First Service to Conception (FSC), along with a revised DPR formula that permits more flexibility with VWP. About 32 million records from the National Cooperator Database, covering 5 major dairy breeds (2003-2023), were used for this study. Data for cows calving before 2003 were unavailable because insemination records were not recorded prior. The findings suggest FSC enhances female fertility evaluations, providing a more comprehensive reproductive assessment independent of VWP. Another approach was an adjustment to the DPR calculation (DPRadj) to account for herd VWP on a herd-year and lactation group basis. The mean DPR value was 45.06%, while DPRadj increased the mean value to 52.58%. The mean FSC was 62.64 d. In an analysis using first lactation cows for cow traits and heifers for heifer traits, genetic correlations of FSC with other fertility traits were 0.97 with Cow Conception Rate (CCR) and DPR, 0.98 with DPRadj, 0.40 with Heifer Conception Rate (HCR), and 0.32 with Early First Calving (EFC). Predicted transmitting abilities (PTA) were calculated to assess the implications of adding FSC to, or replacing DPR with DPRadj within the CDCB multi-trait evaluation index, Net Merit $ (NM$). The highest correlation among the top 10% of bulls occurred when replacing DPR with DPRadj (0.99). Adding FSC to the original model reduced the latter correlation to 0.88, which indicates slight re-ranking of top bulls. Among animals with PTA reliability above 50%, the lowest correlation was between the original index and the index replacing DPR with FSC (0.95). This work advances genetic evaluation in dairy cattle, improving reproductive efficiency and productivity.

daughter pregnancy rate↗
PubMed1975

Nitrogen requirement and utilization in dairy cattle.

Formulation of dairy cow rations should consider the following points regarding nitrogen utilization by lactating cows. (a) Maintenance of ruminal ammonia nitrogen in excess of 5 mg/100 ml rumen fluid has no effect on microbial protein production. (b)Supplemental nonprotein nitrogen is not utilized in typical dairy and feedlot beef rations containing more than 12 to 13% crude protein(dry matter basis). (c)Nonprotein nitrogen is approximately equal to true protein as a source of nitrogen in typical dairy and feedlot rations containing not more than 12 to 13% crude protein. (d)A scheme based upon metabolizable protein (absorbable protein) for calculating requirements and comparing protein sources is superior to crude or digestible protein designations. Ultimate expression of the requirement may be in terms of crude protein for the sake of simplicity. (e)One kilogram of crude protein, regardless of nitrogen source, equals about .75kg metabolizable protein in typical dairy and feedlot beef rations containing not more than 12 to 13% crude protein. One kilogram of plant protein (true protein) fed in excess of an amount equivalent to 12 to 13% dietary protein equals about .3 kg metabolizable protein. (f)Protein supplementation of lactating cows might be related more to stage of lactation than to milk production. (g)Lactating cows having above average lactational ability may benefit from dietary protein as high as 16 to 17% (dry matter basis) during the first third of lactation. (h)Cows in the latter two-thirds of lactation appear to require 12.5% dietary protein or less. (i)Plant protein (true protein) should be the supplemental sources of nitrogen during the first third of lactation, with NPN providing most, if not all, the supplemental nitrogen during the last two-thirds of lactation.

Ammonia↗
PubMed1978

Sources of potential residue problems in dairy herds.

Drugs and chemicals provide economic benefit to animal and crop production; to derive this benefit they must be used appropriately. Data from the United States Department of Agriculture, Food Safety and Quality Service residue monitoring program indicates certain drugs and chemicals are not being used appropriately by the dairy industry, and residues are occurring in cow carcasses at slaughter. Residues of antibiotics and certain pesticides which are administered intentionally are being found. Dairy cows are also particularly susceptible to inadvertant exposure to chemicals because of certain management practices and physiologic characteristics of dairy cows. Contamination of Michigan dairy cows with polybrominated biphenyls is an example. Methods of controlling both intentional and unintentional exposure of cows to drugs and chemicals will require considerable involvement of producers.

Animals↗