High-yielding Holstein Cows Research Articles

Associations of lameness with milk composition, fatty acid profile, and milk coagulation properties in mid-lactation high-yielding Holstein cows

Lameness, an animal welfare and profitability related problem in dairy industry, was evaluated on 126 multiparous Estonian Holstein cows on a 5-point scale; score three or above indicated lameness. Milk samples of the cows were analysed for basic composition, content of mineral elements, fatty acid (FA) profile and coagulation properties (MCP). Lame cows had lower milk yield and a lower milk protein and milk fat yield compared to non-lame cows. MCP and content of mineral elements were not affected by lameness. The concentrations of most individual milk FA, their groups formed by chain length, degree of saturation or by origin were not affected by the lameness. Lameness was associated with a higher concentration of odd- and branched-chain fatty acids and C18:0. Milk from lame cows is suitable for consumers as lameness did not impair nutritional value nor MCP of the milk.

Longitudinal characterization of the metabolome of dairy cows transitioning from one lactation to the next: Investigations in the liver

This study aimed to investigate the metabolic changes in the livers of dairy cows from 1 wk before dry-off to 1 wk after calving. Twelve high-yielding Holstein cows were included in a longitudinal study and housed in a tie-stall barn. The cows were dried off at 6 wk before the expected calving date (dry period length = 42 d). During the entire lactation, the cows were milked twice daily at 0600 and 1700 h. Liver biopsies were taken from each cow at 4 different times: wk -7 (before drying off), -5 (after drying off), -1 and +1 relative to calving. A targeted metabolomics approach was performed by liquid chromatography and flow injection with electrospray ionization triple quadrupole mass spectrometry using the MxP® Quant 500 kit. A total of 185 metabolites in the liver were used for the final data analysis. Principal component analysis (PCA) revealed a clear separation by days of sampling, indicating a notable shift in metabolic phenotype from late lactation to dry period and further changes after calving. Changes were observed in several classes of compounds, including amino acids and biogenic amines. In particular, the changes in acylcarnitines (AcylCN), phosphatidylcholines (PC), sphingomyelins (SM) and bile acids (BA) indicated extensive remodeling of the hepatic lipidome. The changes in AcylCN concentrations in early lactation suggest incomplete fatty acid oxidation in the liver, possibly indicating mitochondrial dysfunction or enzymatic imbalance. In addition, the changes in PC and SM species in early lactation indicate altered cell membrane composition, which may affect cell signaling and functionality. In addition, changes in BA concentrations and profiles indicate dynamic adaptations in BA synthesis, lipid digestion and absorption during the observation period. In particular, PCA analysis showed an overlapping distribution of liver metabolites in primiparous and multiparous cows, indicating no significant difference between these groups. In addition, Volcano plots showed similar liver metabolism between primiparous and multiparous cows, with no significant fold changes (>1.5) in any metabolite at significant P-values (false discovery rate <0.05). These results provide valuable insight into the physiological ranges of liver metabolites during dry period and calving in healthy dairy cows and should contribute to the design and interpretation of future metabolite-based studies of the transition dairy cow.

Eficácia do HoofCare® no tratamento da dermatite digital em vacas leiteiras

ABSTRACT This study aimed to determine the effectiveness of topical HoofCare® in the treatment of digital dermatitis (DD) in dairy cows. Thirty-six high-yielding Holstein cows with DD in at least one limb were included and randomly divided into two groups, making 42 limbs. The alternating treatment group consisted of 21 limbs treated for three alternating days every 48h, and the continuous treatment group consisted of 21 limbs treated every 24h for five days. The cows underwent lameness examination, thermographic analysis, and qualitative and quantitative analysis of the lesions on D0 (time of identification of the lesion and prior to treatment), D4 (fourth day of treatment), and D10 (five days after the end of treatment). The data were compared between different time points and groups. There was no significant difference between the groups for the variables evaluated. However, both groups presented a reduction in the degree of lameness around the lesion, in the local temperature, and regression from the active to the inactive stage of the lesions. Thus, this short-term study demonstrates the suggestive efficacy of HoofCare® in treating DD and recommends conducting further long-term studies.

Effect of co-positivity for brucellosis and tuberculosis on milk yield and fertility of Holstein cows.

This study aimed to determine whether cows detected as tuberculosis (bTB) reactors and seropositive to brucellosis (bBR), as well as co-positive to bBR and bTB (bBR-bTB) and with a complete lactation before slaughter, were associated with reduced milk production and fertility. A total of 8068 productive and reproductive records of high-yielding Holstein cows from a single large dairy herd with a high prevalence of bTB and bBR were collected from 2012 to 2015. Lactation derived either from calving (n = 6019) or hormonally induced lactation (n = 2049), and all cows received growth hormone throughout lactation. For cows not induced into lactation, pregnancy rate to first service for healthy cows (C; 26.6%) was higher (P < 0.01) than bBR (15.2%), bTB (15.8%), and bBR-bTB (1.3%) cows. For induced cows, pregnancy rate to first service did not differ significantly among C, bBR, and bTB (14.5-17.3%) cows, but the percentage success of first service was extremely low (1.3%; P < 0.01) in bBR-bTB cows. Services per pregnancy (only pregnant cows) were lowest for C (3.3 ± 2.9; P < 0.01) and highest (6.4 ± 3.4) for bBR-bTB non-induced cows. This variable was lowest for C (2.9 ± 2.5; P < 0.01) and highest for bBR-bTB non-induced cows (6.3 ± 3.1). Pregnancy rate to all services did not differed for C (79.5%), bBR (76.7%), and bTB (75.9%) but was lower (58.9%; P < 0.01) for bBR-bTB non-induced cows. For induced cows this variable was highest for bBR (53.3%) and lowest for bBR-bTB (34.1%; P < 0.01) non-induced cows. 305-d milk production was increased by 4%, and total milk yield by 7% in TB-positive cows compared to that of the negative cows non-induced hormonally into lactation. This study showed the negative impact of the co-positivity for bTB and bBR on the reproductive efficiency of Holstein cows, although positive bTB and bBR tests enhanced milk yield.

Digestibility of substances, balance of Nitrogen, Zinc and Manganese in highly productive cows of the Holstein breed of German selection in the first period of lactation for feeding mixed ligand complexes of Zinc, Manganese and Co-balt

The article deals with the results of research to study the digestibility of nutrients in the ration and metabolism of Nitrogen, Zinc and Manganese in high-yielding Holstein cows of German selection in the first period of lactation for feeding mixed ligand complexes of Zinc, Manganese and Cobalt. The research was performed in the conditions of Terezyne Ltd., Bila Tserkva district, Kyiv region. There was an increase in the coefficients of digestibility of dry matter in cows of the 2nd-5th experimental groups compared with animals of the 1st control group, respectively by 1.8–3.5 % (P &lt; 0.05); organic matter by 0.3–2.5 %; crude protein by 0.5–4.2 % (P &lt; 0.05 – P &lt; 0.01); crude fat by 1.1–1.8 %; crude fiber by 1.3–3.3 % and nitrogen-free extractives by 2.1–4.2 %. Cows of the experimental groups consumed more Nitrogen than the cows of the control group: 20.18 g or 2.4 % – the 2nd group, 55.06 g or 6.6 % – the 3rd, 42.52 g or 5, 1 % – 4th and 28.98 g or 3.5 % – 5th experimental group due to better eating of the feed mixture. General consumption level of Nitrogen in relation to excreted with milk and deposited in the body of cows of the control group was 32.02 %, and in animals of the 2nd, 3rd, 4th and 5th experimental groups – 33.59 %; 37.31; 36.99 and 34.97 %. In relation to the total digested amount, the proportion of Nitrogen deposited in the body and excreted with milk in animals of the control group was 42.38 %, and in the experimental – 44.25–47.34 %. Doses of Zinc, which provided its existing rate of 54–85 % due to the mixed ligand complex, positively influenced on the the metabolism of trace elements in the organism of experimental cows. Assimilation of Zinc in the organism was determined by the amount of its secretions with milk and deposits in the body and in absolute terms it was the lowest in cows of the 4th and 5th experimental groups – 562.7 mg and 671.6 mg against 740.8 mg in the 1st control group and the largest – 784.7 mg and 801.3 mg in animals of the 2nd and 3rd experimental groups. The use of a mixed ligand complex of manganese ensured its positive balance in the organism of cows and the absorption of the trace element in the organism of experimental cows ranged from 22.5 % in the 2nd experimental group to 33.2 % in the 3rd experimental group. The best indicators for the metabolism of Nitrogen, Zinc and Manganese were got in the third experimental group whose cows were fed a feed mixture, that in 1 kg of DM contained, mg: Zinc – 54.7; Manganese – 54.7; Cobalt – 0.7; Selenium – 0.3; Copper – 12 and Iodine – 1.1.

Risk factors associated with testing positive for tuberculosis in high-yielding Holstein cows

Tuberculosis remains a significant infectious disease of farm animals and humans worldwide. The objective of this study was to assess various risk factors associated with testing positive for bovine tuberculosis (bTB) in high-yielding Holstein cows in an intensive dry-lot dairy operation. In a retrospective observational study, 9312 records from Holstein cows from a large dairy herd in northern Mexico were used. The incidence rate of lactating cows reactor to bTB was 7.3 cases/100 cow years (95% CI = 6.7-7.9%). Multiple logistic regression models indicated that cows with total milk yield during the first lactation >10,200 kg were 1.3 times (95% confidence intervals (CI) for odds ratio (OR) = 1.2-1.6) more likely to be detected as bTB reactors than cows with total milk yield <10,200 kg (8.2 vs. 6.4%; P < 0.01). The risk of being reactor to bTB increased with x̅ total milk yield/lactation >11,500 kg (OR=2.7, 95% CI = 2.3-3.3; 10.4 vs. 4.2%) compared with cows with x̅ total milk yield/lactation <11,500 kg. Cows with >10,200 kg 305-day milk yield in the last lactation was associated (P < 0.01) with 1.3 times higher odds (95% CI for OR = 1.1-1.5) of being classed as reactors than cows with <10,200 kg. Cows with peak milk yield >48 kg were 1.9 times (95% CI for OR = 1.6-2.2) more likely to be reactor to bTB than cows with peak milk yield <48 kg (9.2 vs. 5.1%; P < 0.01). Cows with either puerperal metritis (OR = 0.07, 95% CI = 0.5-0.9) or carrying twins (OR = 0.05, 95% CI = 0.01-0.19) had a protective role for being reactor to bTB. This study showed that increased milk production was associated with a higher risk of becoming positive to tuberculin skin test in high-yielding Holstein cows.

Effectiveness of feed nitrogen use depending on the level of raw protein and the ratio of protein fractions in the rations of cows

Protein nutrition of ruminants as well as other animal species, should be considered as an amino acid nutrition, since not protein as such, but amino acids are the main material for the synthesis of milk proteins, tissues, enzymes, many hormones, neuropeptides and others that play an important role in ensuring the vital functions of the body. Studying the eff ects of diff erent levels of DPR and ratios UPR:DPR with diff erent content of raw protein in rations for nitrogen metabolism, eff ectiveness of feed protein use and dairy productivity of cows is of great scientifi c and practical importance. The purpose of the researches was to determine the optimal levels of undigested protein in rumen (UPR) and digested protein in rumen (DPR) and to determine the possibility of reducing protein consumption in the rations of high-yielding Holstein cows during the early lactation period. It has been found that in rations with 15,7 % crude protein (CP) the optimal ratio was UPR:DPR = 35:65 (UPR – 5,44 %, DPR – 10,3 % DM), which has been confi rmed by the more active formation of free lysine and methionine in the rumen, the yield of microbial protein, higher coeffi cients of digestibility of dry matter, nitrogen, fi ber, higher yield of lysine and methionine in the duodenal chyme, as well as the lowest losses of protein consumed in the process of rumen digestion. Dairy productivity of cows on this ration was at the level of that of cows on rations with 17,7 % CP – 38,7 kg/day when it contains 3,72 % fat and 3,27 % protein. On the ration with the same CP content (15,7 %), but the ratio of UPR:DPR = 50:50 there was a signifi cant decrease in feed consumption (P &lt; 0,01) and the decrease in dairy productivity of cows, which was probably due to the low level of formation of ammonium nitrogen NH3 -N in the rumen.

Effects of heat stress on reproductive efficiency in Holstein dairy cattle in the North African arid region.

This work aims to study the relationship between variations of the Temperature-Humidity Index (THI) and the parameters of reproduction especially the first conception rate (FCR) and to determine the threshold THI value where cows' fertility rate dropped in 12 Holstein dairy herds raised in the arid climatic conditions of Tunisia. THI values were calculated over 22years (1996-2018), and the mean monthly temperature and relative humidity data were obtained from the Meteorological Institute of Tunisia. A total of 20,396 individual records (Insemination and calving dates) were extracted from the Livestock and Pasturing Office (OEP, Tunisia) with regard to the highest THI before breeding, on the breeding day, and after breeding. Statistical analysis was performed using the GLM procedure of SAS software. Results point to the fact that a summer heat stress exists in southeast Tunisia and lasts for 4months starting from June until September with THI values fluctuating between 73±2.38 and 79±3.01 exceeding, therefore, THI threshold of 72. Increased THI from ≤70 to ≥80 units was associated with drops in conception rate (CR) and fertility rate (FR) of 49% and 45% giving a correlation with the THI of (r=-.72, p<.05) and (r=-.74, p<.05), respectively. When cows were inseminated on extremely hot days (THI≥80) preceded by cooler temperatures, pregnancy by service (P/AI) was 7% points higher than for other cows that were exposed to high temperatures before breeding. The average number of insemination was higher (p<.05) from THI≤70 (2.01) compared to THI≥80 (3.41). Cows calving during an absence of heat stress (THI≤70) have the shortest average calving intervals (CI: 420±15.1days). Contrastly, calving in the condition of heat stress (THI≥80) has the longest CI (487±12.8days). For each point increase in the THI value above 67, there is a decrease in the first conception rate by 1.39%. In this particular arid environment, high-yielding Holstein cows' breeding success is strongly affected by heat stress that takes place just before or after breeding.

THE INDICES OF MILK QUALITY, REPRODUCTION, BLOOD AND RUMEN LIQUID IN HIGHLY PRODUCTIVE COWS IN THE FIRST PERIOD OF LACTATION FOR FEEDING OF MIXED-LIGANDE COMPLEXES OF ZINC, MANGANESE AND COBALT

The article presents data on milk productivity, reproductive function and chemical composition of milk, as well as hematological parameters of blood and rumen liquid in high-yielding Holstein cows of German selection, Ukrainian black-spotted dairy and Ukrainian red-spotted dairy breeds in the first lactation period for feeding them different doses of mixed-ligand complexes of Zinc, Manganese and Cobalt.&#x0D; It is established that the use of mixed-ligand complexes of Zinc, Manganese and Cobalt in the feed mixture in comparison with their sulfates has a positive effect on milk productivity and reproductive function of cows and the chemical composition of their milk, and feed costs decrease with increasing productivity.&#x0D; The use of different forms and levels of Zinc, Manganese and Cobalt in the diets of experimental cows affected protein and carbohydrate-fat metabolism and the best results were obtained when using different levels of these trace elements in the feed due to their mixed-ligand complexes.&#x0D; In the rumen liquid of experimental cows, the pH value increased in the alkaline direction and the difference to the control group was statistically significant. There was also a tendency to increase residual nitrogen compared to control. There was a significant difference in the reduction of ammonia nitrogen in the rumen liquid of cows of experimental groups, which indicates better use and assimilation of crude protein.&#x0D; The best indicators of milk productivity, chemical composition of milk, reproductive function, blood and rumen liquid were obtained when using mixed-ligand complexes of Zinc, Manganese and Cobalt in the feed mixture when the concentration of these trace elements in 1 kg of DM was, mg: Zinc – 60.8; Manganese – 60.8; Cobalt – 0.78; Selenium – 0.3; Copper – 12 and Iodine – 1.1. This concentration of trace elements was achieved due to their mixed-ligandent complexes, copper – its sulfate, iodine – potassium iodide, selenium – selenium suplex.

Відтворна здатність голштинських різновікових корів в умовах промислового комплексу

The article presents studies results on the subject of reproductive capacity indicators of different ages high-yielding Holstein cows in the conditions of an industrial complex for milk production. The study was conducted on the basis of PJSC (Private Joint Stock Company) Agro-Soyuz in the Sinelnikovsky district of the Dnipropetrovsk region (Ukraine). The experimental groups of animals were formed in the following way: group I (n = 35) – first-calving heifers; group II (n = 35) – animals of the second lactation; group III (control), (n = 35) – animals of the third lactation; group IV (n = 35) – cows of the fourth lactation. Certain age dependence of the insemination index has been established. Young first-calving heifers and adult cows of the fourth lactation (groups I and IV) had a relatively better value of this indicator – 4.5 units. At the same time, cows of the second and third lactation (group II; group III – control) were characterized by a sharp decline in reproductive ability, therefore, for one fertilization it was necessary to carry out 5.8 artificial inseminations for them. Based on the level of the insemination index by research groups, it was logical that the calving-to-conception interval for all experimental animals was much lower than the stereotyped value (60–80 days) and averagely amounted to almost 8 months. Infertility in animals of experimental groups was directly determined by the calving-to-conception interval duration and the average value of which was within 165 days. More infertile days were recorded in the dairy complex with group III cows (control) – 195 days. The value of the adaptation index in the experimental groups was unaligned. Cows of the first two lactations (groups I and II) were characterized by this stable value of 7.6 units. After that, during the third lactation (group III – control), it was increased by 2 units – 9.6, and in adult cows of the fourth lactation (group IV), it had a tendency to rapidly decrease to 4.8 units. First-calving heifers (group I) and adult cows (group IV) had the lowest production losses because they had the fewest infertile days. Animals of the third lactation (group III – control) were characterized by the highest production losses – 0.68 calves and 3 166 kg of milk.

Injectable organic and inorganic selenium in dairy cows - Effects on milk, blood and somatic cell count levels.

Mastitis is the most costly disease of dairy cows. A pro-active approach includes insuring adequate levels of selective trace minerals. The aim of this study was to determine the effect of two different commercially available, injectable selenium products, (sodium) Na-selenite (inorganic) and (selenium) Se-methionine (organic), on milk composition and on serum and milk selenium concentrations in high-yielding Holstein cows on total mix ration. Sixty multiparous cows were randomly selected into three groups of 20, one control group and two groups supplemented with injectable trace minerals. Blood and milk samples were collected over a period of 60 days. No specific change was indicated in milk yield, lactose, milk urea nitrogen (MUN) and milk pH levels compared with baseline values. The Se-methionine supplemented group showed a numerical increase in total milk protein percentage. In the group injected with Se-methionine, a negative correlation was present for the initial 72 hours between serum selenium concentration and somatic cell count (SCC) and a highly significant (p < 0.001) increase in milk selenium concentration for the initial 24 hours. Serum selenium concentration of Se-methionine-supplemented cows was however not significantly changed. Injection of Na-selenite led to a 60-day initial increase in serum selenium concentration above baseline levels and a significant milk selenium concentration on day 1 but to a negative correlation between serum selenium concentration and SCC. Differences in serum and milk selenium concentrations followed with the use of organic and inorganic selenium injectables. Injectable Na-selenite, as selenium, can be of important value for cattle farmers if supplemented on strategically physiological periods to improve production, reproduction and immunity.

Milk yield, periparturient diseases and body condition score as factors affecting the risk of fetal losses in high-yielding Holstein cows

The objective of this study was to assess various risk factors affecting fetal losses in high-yielding Holstein cows in a hot environment. In a retrospective observational study, 14,384 records from Holstein cows from a large highly technified dairy herd in northern Mexico were used. Logistic multivariate multiple-group response model indicated that fetal losses between 43 and 260 days of pregnancy were 23.8%. Dry periods &gt;60 d were associated (p&lt;0.05) with 0.8 (confidence interval CI=0.8–0.9) times lower incidence of fetal losses compared to cows with dry periods &lt;60 d. Cows with body condition score (BCS) &gt;3 at calving and 15 days postpartum had about half the risk of suffering fetal losses than cows with BCS &lt;3.0. Cows with peak milk yield &gt;38 kg were 5.5 times more likely to have a fetal loss than cows with peak milk yield &lt;38 kg (36.9 vs. 9.6%; p&lt;0.01). The risk of fetal loss increased with 305-d milk yield &gt;9,000 kg (OR=2.1) compared with cows with milk yield &lt;9,000 kg. Retained placenta was (p&lt;0.05) associated with 1.2 (CI=1.1–1.4) times higher fetal losses than cows without this reproductive disorder. Cows suffering premature parturition had 1.2 (CI=1.0–1.4) greater (p&lt;0.05) risk of suffering fetal losses than cows with normal parturition. Cows with twin pregnancies had significantly increased chances of losing their fetuses than cows with a single fetus (31.1 vs. 15.9 p&lt;0.01). A bimodal distribution of fetal losses was observed with peaks around 50 and 220 days of pregnancy. It was concluded that in this particular hot environment fetal losses were associated with high milk yield, low body energy reserves at calving, reduced dry periods, occurrence of retained placenta, twin pregnancies and premature calving.

Phenotypic relationships, genetic parameters, genome-wide associations, and identification of potential candidate genes for ketosis and fat-to-protein ratio in German Holstein cows

Energy demand for milk production in early lactation exceeds energy intake, especially in high-yielding Holstein cows. Energy deficiency causes increasing susceptibility to metabolic disorders. In addition to several blood parameters, the fat-to-protein ratio (FPR) is suggested as an indicator for ketosis, because a FPR >1.5 refers to high lipolysis. The aim of this study was to analyze phenotypic, quantitative genetic, and genomic associations between FPR and ketosis. In this regard, 8,912 first-lactation Holstein cows were phenotyped for ketosis according to a veterinarian diagnosis key. Ketosis was diagnosed if the cow showed an abnormal carbohydrate metabolism with increased content of ketone bodies in the blood or urine. At least one entry for ketosis in the first 6 wk after calving implied a score = 1 (diseased); otherwise, a score = 0 (healthy) was assigned. The FPR from the first test-day was defined as a Gaussian distributed trait (FPRgauss), and also as a binary response trait (FPRbin), considering a threshold of FPR = 1.5. After imputation and quality controls, 45,613 SNP markers from the 8,912 genotyped cows were used for genomic studies. Phenotypically, an increasing ketosis incidence was associated with significantly higher FPR, and vice versa. Hence, from a practical trait recording perspective, first test-day FPR is suggested as an indicator for ketosis. The ketosis heritability was slightly larger when modeling the pedigree-based relationship matrix (pedigree-based: 0.17; SNP-based: 0.11). For FPRbin, heritabilities were larger when modeling the genomic relationship matrix (pedigree-based: 0.09; SNP-based: 0.15). For FPRgauss, heritabilities were almost identical for both pedigree and genomic relationship matrices (pedigree-based: 0.14; SNP-based: 0.15). Genetic correlations between ketosis with FPRbin and FPRgauss using either pedigree- or genomic-based relationship matrices were in a moderate range from 0.39 to 0.71. Applying genome-wide association studies, we identified the specific SNP rs109896020 (BTA 5, position: 115,456,438 bp) significantly contributing to ketosis. The identified potential candidate gene PARVB in close chromosomal distance is associated with nonalcoholic fatty liver disease in humans. The most important SNP contributing to FPRbin was located within the DGAT1 gene. Different SNP significantly contributed to ketosis and FPRbin, indicating different mechanisms for both traits genomically.

Effect of growth hormone on milk yield and reproductive performance of subfertile Holstein cows during extended lactations

The objective of this study was to determine the effects of the administration of recombinant bovine somatotropin (rbST) throughout lactation to high-yielding subfertile (conception &gt; 270 days postpartum) Holstein cows undergoing extended lactations (≥480 d) on milk production and reproductive performance. The study used two large adjacent commercial herds with similar management in a hot area of northern Mexico (25° N). Cows in one herd (n=2341) received a 500-mg dose of rbST every 14 d until dried off, starting 60 days postpartum. The other herd served as control (n=984). Across parity, rbST-treated cows produced 20% greater milk yield than control cows in 305-d lactations. Across parities, milk yield from 305 d postpartum to the end of lactation was 2734 kg higher in rbST-treated cows than control cows. Across parities rbST-treated cows produced 4777 more kg of milk during the entire lactation (mean 605 d) than the control group (mean 572 d). Conception rates (CR) at first service were only 3.2% and 5.9% (p&lt;0.05) for control and rbST-treated cows, respectively. Overall CR was 43.5% and 61.6% (p&lt;0.05) for control and treated cows, respectively. Control cows required 2.4 more (p&lt;0.01) services per conception than rbST-treated cows. It was concluded that in this hot environment, the use of rbST suits dairy producers because it substantially improves both milk yield and reproductive performance in subfertile high-yielding Holstein cows. By markedly increasing lactation length and lactation persistency farm efficiency is greatly improved due to extended herd life.

ГЕНЕТИЧЕСКИЙ ПОТЕНЦИАЛ БЫКОВ-ПРОИЗВОДИТЕЛЕЙ, ИСПОЛЬЗУЕМЫХ В СТАДЕ ВЫСОКОПРОДУКТИВНЫХ КОРОВ ГОЛШТИНСКОЙ ПОРОДЫ

ГЕНЕТИЧЕСКИЙ ПОТЕНЦИАЛ БЫКОВ-ПРОИЗВОДИТЕЛЕЙ, ИСПОЛЬЗУЕМЫХ В СТАДЕ ВЫСОКОПРОДУКТИВНЫХ КОРОВ ГОЛШТИНСКОЙ ПОРОДЫ

Extended lactation in high-yielding dairy cows. I. Effects on reproductive measurements

The objective of this prospective field study was to evaluate the effects of extending the lactation period on various reproductive measurements of high-yielding Holstein cows. On 40 d in milk (DIM), cows were gynecologically examined (transrectal palpation, sonography, vaginoscopy). Cows without signs of clinical endometritis were blocked by parity and were randomly allocated to 1 of 3 experimental groups with a voluntary waiting period (VWP) of 40, 120, and 180 d, respectively (G40, n = 135; G120, n = 141; G180, n = 139). Cows of G120 and G180 were reexamined at the end of the VWP. If natural estrus was detected within 46 d after the end of the VWP, an artificial insemination was performed. If no estrus was detected, the respective cows were synchronized by applying the classical Ovsynch protocol. We found no difference in the proportion of cows in which estrus was detected between 40 to 86 DIM or in the days to first estrus between the 3 groups. Estrus detection in this period was lower in cows with body condition score <3 on 90 DIM compared with body condition score ≥3 (61.5 vs. 76.0%) and in cows with high energy-corrected milk production (ECM) on 92 DIM [58.6 vs. 70.1%, for cows with higher and lower than the median (39.9 kg) ECM, respectively]. The proportion of cows that estrus was detected within 46 d after the VWP was greater in G120 (88.9%) and G180 (90.8%) compared with G40 (70.4%). These effects were more apparent in cows with high ECM. The rate of estrus detection and of becoming pregnant in this period was greater for G120 (hazard ratio = 2.2 and 1.6, respectively) and for G180 (hazard ratio = 2.4 and 1.8) compared with G40. Cows in both groups with extended lactation had greater overall first service conception rates (G120 = 48.9%; G180 = 49.6%) and a lower number of services per pregnant cow (G120 = 1.56 ± 0.1; G180 = 1.51 ± 0.1) compared with G40 (36.6%; 1.77 ± 0.1). We observed no difference in pregnancy loss or in the proportion of cows culled up to 305 d of lactation between the 3 groups. The number of Ovsynch protocols per 1,000,000 kg of ECM was reduced by 75% in G180 and by 74% in G120 compared with G40 (5.9 vs. 7.1 vs. 25.1). In conclusion, extending the lactation of dairy cows can improve main reproductive measurements in high-yielding cows.

Risk factors for clinical ketosis and association with milk production and reproduction variables in dairy cows in a hot environment.

The aims of the present study were to investigate (1) the risk factors that influence the occurrence of clinical ketosis (CK; blood β-hydroxybutyrate > 3.0mmol/L) and (2) to determine the influence of subclinical ketosis (SCK; 1.2 ≤ β-hydroxybutyrate ≤ 2.9mmol/L) and CK on reproductive performance and milk yield in high-yielding Holstein cows in a hot environment. Cows (n = 345) were blood sampled from 6 to 15days postpartum for β-hydroxybutyrate (BHB) determination with a hand-held meter. Cows calving in spring had 3.7 increased odds of having CK (20.7% incidence) than cows calving in summer (3.9% incidence) and autumn (9.4% incidence). Temperature-humidity index < 83 was associated with 1.6 times higher risk for CK compared with cows calving in warmer days. First-service conception rate was 12 and 16 percentage point higher (P < 0.05) in nonketotic cows compared with cows with SCK and CK, respectively. Actual 305-day milk yields for healthy, SCK, and CK cows were 9991 ± 1411, 10,123 ± 1442, and 10,386 ± 1435kg (mean ± SD), respectively, with no difference (P > 0.05) between groups. In conclusion, this study documented that ketosis was seasonal with lower incidence of this metabolic disease during hot seasons and with increased ambient temperature at calving. Also, 305-day milk yield of Holstein cows was not related to blood BHB content early in lactation in this hot environment. However, elevated circulating BHB was negatively associated with conception rate at first service and fetal losses.

Good sensory quality and cheesemaking properties in milk from Holstein cows managed for an 18-month calving interval.

Extended calving interval (CInt) for high-yielding dairy cows beyond the traditional 12mo has been suggested as a profitable, environmentally and welfare-friendly production strategy. However, concerns exist on whether extending cow CInt, and consequently prolonging lactation length, impairs milk quality. The aim of this study was to compare the quality of milk produced during the extended lactation period to mid lactation. In particular, milk indicators related to udder integrity and cheesemaking properties when cows were fed low- or high-energy diets in early lactation mobilization period. Forty-seven healthy Danish Holstein cows (15 primi- and 32 multiparous) were fed 2 distinct weight-adjusted diets in early lactation: either a high-density diet for approximately 42d in milk (DIM) followed by a low-density diet (n=22), or a low-density diet throughout the whole experiment (n=25). Milk quality was explored at 3 lactation periods: 140 to 175 DIM (P1), 280 to 315 DIM (P2), and 385 to 420 DIM (P3). Lactation period was found to be the main factor affecting milk yield, quality, and cheesemaking properties. Primiparous cows kept the same daily milk yield throughout the studied periods, whereas multiparous cows produced, on average, 10.2kg/d less in P3 compared with P1. Fat, protein, and casein concentrations increased, respectively, by 18, 16, and 16%, from P1 to P3. Cheesemaking properties, such as curd-firming rate, gel strength, and wet and dry curd yield, got an improvement from P1 to P3 and were strongly correlated with milk concentrations of protein and casein. The udder integrity indicators, somatic cells count, level of free amino terminals as an index of proteolysis, and milk pH, remained unchanged throughout the studied lactation periods. Feeding cows either high- or low-density diets during the early lactation mobilization period did not exert any relevant carryover effect on milk composition, and thus had no effect on cheesemaking properties in extended lactation. Further, sensory quality of mid- and extended-lactation milk was assessed by a trained sensory panel. The sensory quality of milk from P3 reflected sensory descriptors related to the increased levels of fat and protein over lactation, but, importantly, milk produced in P3 did not present sensory demerits when compared with milk produced in P1. In conclusion, high-yielding Holstein cows undergoing an 18-mo CInt produced high-quality milk from mid to extended lactation.

Climatic conditions, twining and frequency of milking as factors affecting the risk of fetal losses in high-yielding Holstein cows in a hot environment.

An epidemiological study of risk factors for fetal losses was carried out on 62,403 high-yielding Holstein cows in 29 large highly technified dairy herds in northern Mexico (25° N; 23.5°C mean annual temperature). Multivariate multiple-group response model indicated that fetal losses between 43 and 260days of pregnancy were 23%. Heat-stressed cows at conception (temperature-humidity index, THI >82) were 14 times more likely (P < 0.01) to present fetal losses than not heat-stressed cows (27 vs. 18%). Heat-stressed cows at 60days of pregnancy (THI >82) were 4.5 times more likely (P < 0.01) to present fetal losses than cows suffering heat stress in early gestation (29.1 vs. 17.7%). The proportion of cows experiencing fetal loss was lower for multiparous than primiparous cows (odds ratio; OR = 0.7). Cows with twin pregnancies had significantly increased chances of losing their fetuses than cows with a single fetus (33.6 vs. 20.7%; P < 0.01). Cows with three milkings per day were 30% more likely (P < 0.01) to lose their fetuses than cows milked twice daily. Cows calving in winter and spring had significantly increased chances of losing their fetuses than cows calving in summer and fall (30-35 vs. 4-5%; P < 0.01). It was concluded that, in this particular environment, heat stress exert a great influence on fetal losses in high producing Holstein cows.

Extended lactation in high-yielding Holstein cows: Characterization of milk yield and risk factors for lactations >450 days

Two data files consisting of 3278 (one herd) and 4393 lactations (three herds) were used to characterize milk production of high-yielding Holstein cows milked three times per day and experiencing extended lactations (up to 1399 days) in a hot environment. Additional objectives were to identify risk factors for the occurrence of extended lactations, to assess the association between lactation length and milk yield and to determine the conception rates of cows with extended lactations and with multiple services. Thirty percent of lactations were between 450 and 1399 days. Lactation yield of cows with lactations >900 days was over 30,000kg. Average daily milk yield from 305 to >450 days in milk was 29.9 and 31.9kg for primiparous and multiparous cows, respectively. The epidemiological analysis of risk factors for extended lactations using a multiple variable logistic regression indicated that ketosis (OR=1.4), peak milk yield (<50 vs >50kgd−1, OR=1.4), temperature-humidity index at 60 days postpartum (<82 vs >82 units, OR=1.4), retained placenta (odds ratio (OR)=1.5), 305-d milk yield (<11,000 vs >11,000kg, OR=1.6) and the occurrence of metritis (OR=1.8), significantly increased the risk for lactations >450 days. Primiparous cows had less than half the risk of extended lactations (OR=0.3) compared to multiparous cows. Conception rate in cows with extended lactations decreased as number of services increased (conception rate=50.5% for 4 services and 13% for ≥14 services). The data showed that well-managed Holstein cows milked three times daily were capable of lactating for over 1200 days with remarkably high persistency and with high milk yield at drying-off. Reproductive and metabolic disorders associated with calving were important risk factors for extended lactations.