Afternoon Milking Research Articles

Milk and dairy product analyses at the Dairy Chemistry Division in Mauritius: an overview

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Effects of space allowance in the waiting area on agonistic interactions and heart rate of high and low ranking horned dairy cows

One possible alternative to avoid the disbudding of calves is to keep the cows horned. This, however, requires adapted housing conditions. An important aspect to reduce agonistic interactions that may lead to injuries is to provide appropriate space allowances in all parts of the stable. This study investigated the influence of three different space allowances in the waiting area of the milking parlour (4.0, 2.5, 1.7m²/cow) on the risk of injury and stress. In a research herd of 85–87 horned dairy cows, heart rate and number of physical agonistic interactions (“butting” and “being butted”) per cow and hour during waiting were recorded in nine lower and nine higher ranking focal cows. Furthermore, heart rate in the milking parlour and the number of flinches, steps and kicks per cow and minute (“FSK-reponses”) in eight to nine lower and 11 higher ranking focal cows were collected.Results showed that social rank had no influence on heart rate and FSK. being butted (p=0.029), FSK-responses (p=0.002) and heart rates in the waiting area and parlour (p=0.000) were significantly affected by space allowance. the lowest space allowance of 1.7m² per cow resulted in Higher values, although for heart rates there were significant interaction effects with time of day (morning or afternoon milking) (p=0.021 to p=0.000): Less clear Results and generally Higher values were found in the afternoon. in terms of animal welfare, a larger space allowance than 1.7m²/cow in the waiting area appears beneficial. under the conditions investigated, except for FSK-responses, no consistent benefit could be detected by providing 4.0m²/cow instead of 2.5m²/cow.

The relationship between fatty acid profiles in milk identified by Fourier transform infrared spectroscopy and onset of luteal activity in Norwegian dairy cattle

To investigate the feasibility of milk fatty acids as predictors of onset of luteal activity (OLA), 87 lactations taken from 73 healthy Norwegian Red cattle were surveyed over 2 winter housing seasons. The feasibility of using frozen milk samples for dry-film Fourier transform infrared (FTIR) determination of milk samples was also tested. Morning milk samples were collected thrice weekly (Monday, Wednesday, Friday) for the first 10 wk in milk (WIM). These samples had bronopol (2-bromo-2-nitropropane-1,3-diol) added to them before being frozen at −20°C, thawed, and analyzed by ELISA to determine progesterone concentration and the concentrations of the milk fatty acids C4:0, C14:0, C16:0, C18:0, and cis-9 C18:1 as a proportion of total milk fatty acid content using dry-film FTIR, and averaged by WIM. Onset of luteal activity was defined as the first day that milk progesterone concentrations were >3 ng/mL for 2 successive measurements; the study population was categorized as early (n=47) or late (n=40) OLA, using the median value of 21 DIM as the cutoff. Further milk samples were collected 6 times weekly, from morning and afternoon milkings, these were pooled by WIM, and one proportional sample was analyzed fresh for fat, protein, and lactose content by the dairy company Tine SA, using traditional FTIR spectrography in the wet phase of milk. Daily energy-balance calculations were performed in 42 lactations and averaged by WIM. Animals experiencing late OLA had a more negative energy balance in WIM 1, 3, 4, and 5, with the greatest differences been seen in WIM 3 and 4. A higher proportion of the fatty acids were medium chained, C14:0 and C16:0, in the early than in the late OLA group from WIM 1. In WIM 4, the proportion of total fatty acid content that was C16:0 predicted late OLA, with 74% sensitivity and 80% specificity. The long-chain proportion of the fatty acids C18:0 and cis-9 C18:1 were lower in the early than in the late OLA group. Differences were greatest in WIM 4 and 5. Differences in concentrations of cis-9 C18:1 were seen between the groups from WIM 1. No relationship was seen between OLA and milk concentrations of either protein or fat, or between OLA and the milk fat:protein ratio. The differences in milk fatty acid proportions between the 2 groups are most likely related to differences in energy balance. The study shows that frozen milk samples can be tested for fatty acids by FTIR spectroscopy and that FTIR spectroscopy of milk can be used to provide real-time information about cow reproductive function.

Release of β-endorphin, adrenocorticotropic hormone and cortisol in response to machine milking of dairy cows.

Aim:The present study was undertaken with the objective to obtain insight into the dynamics of the release of β-endorphin, adrenocorticotrophic hormone (ACTH) and cortisol in response to machine milking in dairy cows.Materials and Methods:A total of 10 healthy multiparous lactating Italian Friesian dairy cows were used in the study. Animals were at the 4th-5th month of pregnancy and were submitted to machine milking 2 times daily. Blood samples were collected in the morning: In baseline conditions, immediately before milking and after milking; and in the early afternoon: In baseline conditions, before milking and after milking, for 2 consecutive days. Endocrine variables were measured in duplicate, using a commercial radioimmunoassay for circulating β-endorphin and ACTH concentrations and a competitive enzyme-linked immunoassay for cortisol concentration.Results:Data obtained showed a similar biphasic cortisol secretion of lactating dairy cows, with a significant increase of cortisol concentration after morning machine milking, at both the 1st and the 2nd day (p<0.05), and a decrease after afternoon machine milking at the 2nd day (p<0.01). One-way RM ANOVA showed significant effects of the machine milking on the cortisol changes, at both morning (f=22.96; p<0.001) and afternoon (f=15.10; p<0.01) milking, respectively. Two-way RM ANOVA showed a significant interaction between cortisol changes at the 1st and the 2nd day (f=7.94; p<0.0002), and between the sampling times (f=6.09; p<0.001). Conversely, no significant effects of the machine milking were observed on β-endorphin and ACTH changes, but only a moderate positive correlation (r=0.94; p<0.06) after milking stimuli.Conclusions:A wide range of cortisol concentrations reported in this study showed the complex dynamic patterns of the homeostatic mechanisms involved during machine milking in dairy cows, suggesting that β-endorphin and ACTH were not the main factors that caused the adrenocortical response to milking stimuli.

Effect of feed allowance at pasture on lying behaviour and locomotory ability of dairy cows

In temperate climates where cows are primarily managed at pasture shortages of grass could result in nutritional deficits for the cow and thus pose a challenge to her welfare. This study investigated the effect of daily herbage allowance (DHA) on dairy cow lying behaviour, locomotory ability, and some aspects of hoof health. Ninety-six cows were randomly assigned to one of eight treatments in a 2×4 factorial design; experimental duration (2 week (2W) or 6 week (6W)), and nutritional levels (DHA) (60%, 80%, 100% or 120% of intake capacity). Cows were assigned to treatment on 25 March (36±16 days in milk). Lying behaviour was recorded using modified voltage dataloggers over 7×24h periods at approximately 4d intervals for cows on the 6W treatments. Locomotory ability (including overall locomotion, ab/adduction, tracking, speed, head carriage and spine curvature scores) was assessed four times at approximately 16d intervals. Hoof health (heel erosion and dermatitis scores) were recorded in the milking parlour on four occasions at approximately 19d intervals. Although there was no effect on daily lying time, DHA tended to affect the duration of lying bouts (P=0.1). Cows allocated the highest DHA (120%) had shorter bouts than all other treatments (P=0.05), whereas cows allocated the lowest DHA (60%) had fewer lying bouts than all other treatments (P<0.05). In general, cows allocated a lower DHA took longer to lie down after milking than cows fed at or above intake capacity. The effect was greatest in the afternoon when there was an effect of DHA (P<0.05); cows on the 60% DHA stood for longer after afternoon milking than all other treatments (P<0.01). There was no effect of DHA on locomotory ability for either 2W or 6W cows. However, in the 2W treatment, cows on the 120% DHA had the best spine arch scores (P=0.01), and cows in the 60% treatment had the worst tracking (P<0.05). Likewise in the 6W treatment cows on the 60% DHA had the worst spine arch scores (P<0.05), yet cows allocated a higher DHA tended to have worse ab/adduction scores (P=0.10). There was no effect of DHA on hoof health. The differences in lying behaviour and locomotion do not imply impaired welfare per se. However, altered lying behaviour could indicate hunger, and impaired locomotion could be a result of a thin digital cushion, which is associated with lameness. This study provides valuable information about how DHA can affect the dairy cow, and can be used to formulate further hypotheses to investigate effects on hunger-satiety status and hoof health.

Short communication: Milk fat depression induced by conjugated linoleic acid and a high-oil and low-fiber diet occurs equally across the day in Holstein cows

Recently, a circadian rhythm of milk and milk component synthesis has been characterized that is partially dependent on the timing of feed intake. Our objective was to determine if inhibition of milk fat synthesis during diet-induced milk fat depression occurred to a higher degree during certain phases of the day. A retrospective analysis was conducted on 2 experiments that induced milk fat depression while milking cows 3 times per day at equal intervals. The response at each milking was analyzed using mixed model ANOVA with repeated measures. In experiment 1, nine multiparous Holstein cows were arranged in a 3×3 Latin square design, and treatments were control, 3-d intravenous infusion of 10g/d of trans-10,cis-12 conjugated linoleic acid (CLA), and a low-forage and high-fat diet for 10 d. In experiment 2, ten multiparous ruminally cannulated cows were arranged in a replicated design and milk samples were collected during a control period or after 5 d of abomasal infusion of 10g/d of CLA. The daily pattern of milk fat concentration and yield did not differ between treatments in either experiment. In experiment 1, an effect was found of treatment and milking time on milk fat concentration and yield. Similarly, in experiment 2, main effects were found of treatment and milking time on milk fat concentration and an effect of treatment, but no effect of milking time on milk fat yield. Milk fat percent was increased from 3.41 to 4.06% and 3.25 to 3.48% from the morning to the afternoon milking in experiments 1 and 2, respectively. Additionally, milk fatty acid profile, including trans intermediates, was changed over the day in experiment 1, but the magnitude of the changes were small and the pattern did not differ among treatments. A daily rhythm of milk fat concentration and yield was observed in cows milked 3 times a day, but milk fat depression decreases milk fat yield equally over the day.

Lactose and milk urea nitrogen: fluctuations during lactation in Holstein cows

The objective of this study was to evaluate lactose and milk urea nitrogen (MUN) in milk from Holstein cows and their relationship with days in milk (DIM), milk yield, milk fat, milk protein, and somatic cell count (SCC). A total of 1,034 records corresponding to morning and afternoon milkings of 148 Holstein cows were used. Records were taken from 16 herds located in the Northern and Eastern dairy regions of Antioquia (Colombia). The curves were fitted using a generalized additive mixed model with smoothed estimates to find the best smoothing intensity factors involved in MUN and lactose concentration. Regarding MUN, the contemporary group effect was highly significant, but the parity effect was not significant. The DIM, lactose and milk fat smoothed covariates were highly significant, while milk yield and fat and SCC showed no statistical difference. Regarding lactose content, the contemporary group effect was highly significant, while the parity effect was not significant. Days in milk, MUN, milk fat, milk protein, and afternoon-milking SCC smoothed covariates were highly significant, while milk yield and morning-milking SCC were not significant. Lactose and milk urea nitrogen concentrations are affected by various factors throughout lactation, mainly by days in milk.

Changes in lying behavior after abrupt cessation of milking and regrouping at dry-off in freestall-housed cows: A case study

The objectives of this case study were to evaluate differences between primiparous and multiparous cows in milk production over the last 10 days before abrupt cessation of routine milking to end lactation and to assess the effect of parity and milk production on changes in lying behavior around the routine on-farm practice of abrupt cessation of milking and regrouping in 1 freestall herd in Ontario (Canada). Lying behavior and milk production were monitored in 33 primiparous and 75 multiparous cows. Cows were dried-off abruptly (i.e., no longer milked) after the afternoon milking, regrouped with dry cows, and switched to high-forage diet. At the time of dry-off, cows were producing more than 20 kg/day on average. However, there was great variability across cows, with some cows producing over 35 kg/day on the day before dry-off. After removing 3 outliers, there was no difference between parities in the slope of the milk decrease over the last 10 days before dry-off. There was a negative association between the milk produced on the day before dry-off and lying time on the day of dry-off (coefficient estimate = −11.6 ± 4.7 minute/day) in primiparous cows only. Multiparous cows increased their daily lying time after dry-off; this increase leveled off 2 days after dry-off (lying time [minute/day] = 750.6 + 47.8 day − 9.9 day2). In contrast, primiparous cows decreased their daily lying time on the day of dry-off; however, daily lying time then increased until day 3 after dry-off (lying time [minute/day] = 641.6 − 11.9 day + 19.9 day2). Overall, the frequency of lying bouts increased on the day of dry-off, decreasing over the next days (lying bouts/day = 9.7 + 0.5 day − 0.3 day2). Although average lying bout duration decreased on the day of dry-off and increased over the subsequent days for all cows, the initial decrease was greater in primiparous cows (lying bout duration [minute] = 82.5 − 0.7 day + 1.8 day2 and 68.0 − 3.2 day + 3.6 day2 for multiparous and primiparous cows, respectively). The lying behavior diurnal patterns illustrated a decrease in lying time associated with each milking session on the 2 days before dry-off. Interestingly, similar patterns persisted after dry-off, although the magnitude of the decrease in lying time associated with each omitted milking was lower. Given that lying is a high-priority behavior in dairy cattle, these results suggest that the welfare of cows around the routine on-farm practice of abrupt cessation of milking and regrouping at dry-off, particularly after their first lactation, may be compromised.

Within-milking variation in milk composition and fatty acid profile of Holstein dairy cows

Changes in milk composition during a milking are well characterized, but variation in milk fatty acid (FA) profile is not well described and may affect the accuracy of in-line milk composition analyzers and could potentially be used for selective segregation of milk. Within-milking samples were collected from 8 multiparous high-producing Holstein cows (54.86±6.8kg of milk/d; mean ± standard deviation). A milk-sampling device was designed to allow collection of multiple samples during a milking without loss of vacuum or interruption of milk subsampling. Milk was collected during consecutive morning and afternoon milkings (12-h intervals) and was replicated 1wk later. Each sample represented approximately 20% of the milking and was analyzed for fat, true protein, and lactose concentration and FA profile. Milk fat concentration markedly increased over the course of milk let down (4.4 and 4.2 percentage units at the a.m. and p.m. milking, respectively), whereas milk fat globule size did not change. Milk protein and lactose concentration decreased slightly during milking. Modest changes in milk FA profile were also observed, as milk de novo and 16-C FA concentrations increased approximately 10 and 8%, respectively, whereas the concentration of preformed FA decreased about 7% during the milking. In agreement, mean milk FA chain length and unsaturation modestly decreased during milking (0.59 and 0.014 U, respectively). The observed changes in milk fat concentration during a milking are consistent with previous reports and reflect the dynamic nature of milk fat secretion from the mammary gland. Changes in milk FA profile are not expected to practically affect the accuracy of spectroscopy methods for determination of milk fat concentration. Furthermore, the small variation in FA profile during a milking limits the use of within-milking milk segregation to tailor milk FA profile.

Feasibility of using alternate control as a dairy control system in goats

The feasibility of alternate dairy control as an alternative to traditional dairy control was evaluated. Adjustment factors were obtained for morning (AM) and afternoon (PM) milkings and applied to animals subjected to alternate dairy control to estimate uncontrolled milking and total daily milk yield. Data was compiled from six dairy goat farms in the Metropolitan Region of Chile for animals with completed lactations (of 305 days) and with recorded date of birth and parturition, parity and a minimum of six controls per lactation (used to determine AM, PM and total production). Values were sorted by productive factors parity and lactation month. Statistical analysis was performed using the Number Crunchers Statistical System ®2000 (Kaysville, UT, USA) to obtain mean values and adjustment factors for each productive factor and to make possible their application on any animal presenting the minimum required information. Adjustment factors were applied to 8788 values to estimate total daily milk yield. AM values estimated more accurate totals than PM values. Analysis provided r2 values of 0.9083 and 0.7593, respectively, and supported the reliability of applying calculated adjustment factors to one of two daily milkings. The alternate dairy control system represents a viable alternative for estimation of total daily milk yield.

Pasture intake and milk production of dairy cows grazing annual ryegrass with or without corn silage supplementation

The use of corn silage to supplement grazing dairy cows can improve milk production and nutrient intake when the substitution rate is low. This enhancement occurs by increasing the total DM intake. The hypothesis tested in this study was that increasing corn silage supplementation level of dairy cows grazing annual ryegrass at medium pasture allowance could increase substitution rate and decrease milk production response. Three supplementation levels (0, 4 and 8 kg DM/day) were compared for dairy cows strip-grazing annual ryegrass (Lolium multiflorum cv. Common). The study was arranged as a 3 × 3 Latin square design, repeated three times using nine Holstein lactating cows. The supplement was a 7 : 1 mixture based on the DM of corn silage and soybean meal and was offered individually twice daily after the morning and afternoon milkings. Each treatment group of cows grazed separately at a common daily pasture allowance of 35 kg DM/cow to ground level. Each experimental period was 12 days, with an 8-day adaptation and a 4-day measurement period. The individual pasture intake was measured from Day 9 to Day 12 using the n-alkane technique. The daily pattern of grazing and ruminating times were measured by visual observations. The supplement DM intake was lower than expected, averaging 3.0 and 4.3 kg DM/day for cows receiving 4 and 8 kg DM/day, respectively. Pasture and supplement energy value were 7.0 and 6.3 MJ of NEL/kg DM, respectively. The substitution rate averaged 0.2 and was unaffected by the supplementation level. The pasture intake was similar for all treatments (14.0 kg of DM/day), and total DM intake and milk production (+0.5 kg of milk/kg DM of supplement) increased linearly with increasing supplementation level. The daily grazing time was shorter by 111 min/day for the supplemented cows than for the unsupplemented cows. Cows grazing the annual ryegrass at medium pasture allowance improved their total DM intake and individual performance when supplemented with corn silage.

Siyah Alaca İneklerde Meme Ölçülerinin Somatik Hücre Sayısı ve Günlük Süt Verimi Üzerine Etkisi

This study was carried out to investigate the effect of udder measurements group on somatic cell count (SCC) and daily milk production. Milk samples and udder measurements were collected monthly from 79 lactating Holstein cows on commercial dairy in the province of Niğde. In the study, front teat length (FTL), rear teat length (RTL), front teat diameter (FTD), rear teat diameter (RTD), distance between front teats (DBFT), distance between rear teats (DBRT), front udder height, (FTH), rear udder height (RUH), distance between front and rear teats (DBST) were obtained in before afternoon milking. Udder measurements were divided into 5 groups according to the measurements. The effect of DBFT, DBRT, FTH, RTD, FTD and DBRT groups on daily milk production were statistically significant, while FTH, RUH and DBRT were found non-significant. The effect of udder measurements groups on SCC was found not significant, except rear teat diameter (RTD). Average daily milk production and SCC were estimated as 28.25 kg/day and 274.90 cell/ml, respectively. In conclusion, it can be said that the distance between teats, teat’s diameter and front udder height of Holstein cattle is important factor for milk yield of Holstein dairy cattle. Also, SCC is effected by rear teat diameter.

Ruminal pH and whole-tract digestibility in dairy cows consuming fresh cut herbage plus concentrates and conserved forage fed either separately or as a partial mixed ration

The objective of this experiment was to compare ruminal pH and whole-tract digestibility in cows consuming fresh cut herbage plus concentrates and silage or hay fed either separately or as a partial mixed ration (PMR). Fourteen rumen-fistulated Holstein-Friesian cows that had calved in late winter were housed in metabolism stalls for 9-day experiments in spring (97 days in milk (DIM)) and autumn (237 DIM). All cows were offered 8 kg dry matter (DM)/day of fresh cut perennial ryegrass (Lolium perenne L.) herbage, provided in two equal portions after each milking. Seven cows were assigned to each of two diets: (i) Control: 8.8 kg DM/cow.day milled wheat grain in two equal portions at milking, plus 3.2 kg DM/cow.day perennial ryegrass silage, with all cows receiving the silage portion of their diet after their grain but before their fresh herbage at the afternoon milking; and (ii) PMR: 12 kg DM/cow.day of a PMR containing similar ME as the Control supplements, but comprising maize grain, maize silage, wheat grain, lucerne hay (spring) and pasture silage (autumn). Intake and faecal output was measured on 5 days during each experiment, and ruminal pH was measured every 2 h for a 24-h period. Degradability of wheat and maize grain was measured using standard in sacco techniques. In both experiments, cows fed PMR had higher ruminal fluid pH than Control cows for at least part of the day. Apparent whole-tract digestibilities of DM, organic matter, nitrogen, neutral detergent fibre and starch were greater for Control than PMR cows in spring and not different in autumn (except starch). Ruminal pH was increased by feeding a maize-based PMR but this was not associated with increased whole-tract digestibility. We conclude that the ruminal pH in the Control cows was not low enough for long enough to compromise digestion, or that there was compensatory post-ruminal digestion.

Effects of feeding algal meal high in docosahexaenoic acid on feed intake, milk production, and methane emissions in dairy cows

This study examined effects on milk yield and composition, milk fatty acid concentrations and methane (CH4) emissions when dairy cows were offered diets containing different amounts of algal meal. The algal meal contained 20% docosahexaenoic acid (DHA) and cows were offered either 0, 125, 250, or 375g/cow per d of algal meal corresponding to 0, 25, 50, or 75g of DHA/cow per d. Thirty-two Holstein cows in mid lactation were allocated to 4 treatment groups, and cows in all groups were individually offered 5.9kg of dry matter (DM) per day of concentrates [683g/kg of cracked wheat (Triticum aestivum), 250g/kg of cold-pressed canola, 46g/kg of granulated dried molasses, and 21g/kg of mineral mix] and ad libitum alfalfa (Medicago sativa) hay. The algal meal supplement was added to the concentrate allowance and was fed during the morning and afternoon milking, whereas the alfalfa hay was fed individually in pens. Cows were gradually introduced to their diets over 7d and then fed their treatment diets for a further 16d. Dry matter intake and milk yield were measured daily, and milk composition was measured on a sample representative of the daily milk yield on Thursday of each week. For the last 2d of the experiment, cows were individually housed in respiration chambers to allow measurement of CH4 emissions. Dry matter intake, milk yield and milk composition were also measured while cows were in the respiration chambers. Cows ate all their offered concentrates, but measured intake of alfalfa decreased with increasing dose of DHA by 16.2, 16.4, 15.1, and 14.3kg of DM/d, respectively. Milk yield (22.6, 23.5, 22.6, and 22.6kg/cow per d) was not affected by DHA dose, but milk fat concentrations (49.7, 37.8, 37.0, and 38.3g/kg) and, consequently, milk fat yields (1.08, 0.90, 0.83, and 0.85kg/d) decreased with addition of DHA. The feeding of algal meal high in DHA was associated with substantial increases in the concentrations of DHA (0.04, 0.36, 0.60, and 0.91g/100g of milk fatty acids) and conjugated linoleic acid C18:2 cis-9,trans-11 (0.36, 1.09, 1.79, and 1.87g/100g of milk fatty acids). Addition of DHA did not affect total emissions of CH4 (543, 563, 553, and 520g/cow per d), nor emissions in terms of milk production (24.9, 22.1, 24.3, and 23.4g of CH4/kg of milk), but emissions were increased with respect to total intake (22.6, 23.5, 24.5, and 24.4g of CH4/kg of DM). These findings indicate that CH4 emissions were not reduced when dairy cows were fed a forage-based diet supplemented with DHA from algal meal.

Dietary glutamine enhances immune responses of dairy cows under high ambient temperature

The objective of the study was to determine the effects of adding Gln or Gln in combination with flaxseed to the diet on milk production and immune response of dairy cows during the summer season. The experiment lasted 60d and involved 24 lactating Friesian cows, divided into 4 groups of 6 animals, fed as follows: (1) control diet, (2) control diet supplemented with 160g/d of rumen-protected Gln (GLN), (3) control diet supplemented with whole flaxseed (FS), and (4) control diet supplemented with both flaxseed and Gln (FS+GLN). Individual milk samples were collected at morning and afternoon milkings every 14d throughout the experiment and analyzed for pH, total protein, casein, fat, lactose content, and somatic cell count. Milk samples were also analyzed for milk fatty acid profile. Monitoring of cow immune responses was carried out by the determination of lymphocyte response to phytohemagglutinin in vivo on each animal by measurement of skin-fold thickness at site of phytohemagglutinin injection. A humoral response to chicken egg albumin (OVA) was determined following a subcutaneous injection with OVA. Plasma samples were measured for the presence of anti-OVA IgG, IL-1β, IL-6, and IL-10. Results indicate that Gln administration can be used to support dairy cows under a hot climate, because Gln was able to enhance cow immune reactions in terms of a strengthening of cell-mediated immune response, which is weakened in cows under heat stress. In addition, an increase in milk and fat, protein, and casein yields in response to GLN was observed. When administrating Gln in combination with flaxseed, milk production and milk fat profile did not further increase compared with FS milk, and a reduction in immune reactivity compared with FS and GLN cows was found.

Exploring the Novel Genetic Variant of PITX1 Gene and Its Effect on Milk Performance in Dairy Goats

Paired-like homeodomain transcription factor 1 (PITX1) plays an important role in pituitary development by indirectly regulating the expression of the GH and PRL genes, and therefore PITX1 gene is regarded as a potential candidate gene for building the relationship between the gene polymorphism and milk traits. The aim of this study was to explore the novel genetic variant in PITX1 gene and its effect on milk performance in dairy goats. Herein, a novel genetic variation (NW_00314033: g.201G>A or IVS1+41G>A) located at nt41 position of the first intron of the goat PITX1 gene was reported at the P1 locus, which can be genotyped by the Msp I PCR-RFLP. In the Msp I PCR-RFLP analyis, the GG variant was a major genotype, and the A variant was a minor allele in Guanzhong dairy goats which was at Hardy-Weinberg disequilibrium (chi-square χ2=140, P<0.01). The establishment of associations between different genotypes and milk performance was performed in the analyzed population. A total of three significant associations of the polymorphism with average milk fat content (%) (P=0.045), morning milk fat content (%) (P=0.049), and afternoon milk fat content (%) (P=0.050), were found, respectively. A significant relationship between the polymorphism and average total solid content (P=0.029) was also detected. This novel single nucleotide polymorphism (SNP) extended the spectrum of genetic variation of the goat PITX1 gene, and its significant association with milk performance would benefit from the application of DNA markers related to improving milk performance through marker-assisted selection (MAS) in dairy goats.

Effects of an evaporative cooling system on plasma cortisol, IGF-I, and milk production in dairy cows in a tropical environment

Access to an evaporative cooling system can increase production in dairy cows because of improved thermal comfort. This study aimed to evaluate the impact of ambient temperature on thermoregulation, plasma cortisol, insulin-like growth factor 1 (IGF-I), and productive status, and to determine the efficiency of an evaporative cooling system on physiological responses under different weather patterns. A total of 28 Holstein cows were divided into two groups, one with and the other without access to a cooling system with fans and mist in the free stall. The parameters were analyzed during morning (0700 hours) and afternoon milking (1430 hours) under five different weather patterns throughout the year (fall, winter, spring, dry summer, and rainy summer). Rectal temperature (RT), body surface temperature (BS), base of tail temperature (TT), and respiratory frequency (RF) were lower in the morning (P < 0.01). The cooling system did not affect RT, and both the groups had values below 38.56 over the year (P = 0.11). Cortisol and IGF-I may have been influenced by the seasons, in opposite ways. Cortisol concentrations were higher in winter (P < 0.05) and IGF-I was higher during spring-summer (P < 0.05). The air temperature and the temperature humidity index showed positive moderate correlations to RT, BS, TT, and RF (P < 0.001). The ambient temperature was found to have a positive correlation with the physiological variables, independent of the cooling system, but cooled animals exhibited higher milk production during spring and summer (P < 0.01).

An unprotected conjugated linoleic acid supplement decreases milk production and secretion of milk components in grazing dairy ewes

Feeding conjugated linoleic acid (CLA) in a rumen-inert form to dairy ewes has been shown to increase milk production, alter milk composition, and increase the milk fat CLA content. However, few studies have tested ruminally unprotected CLA sources. The objective of this study was to evaluate the effects of an unprotected CLA supplement (29.8% of cis-9,trans-11 and 29.9% of trans-10,cis-12 isomers as methyl esters) on milk yield and composition of dairy ewes. Twenty-four lactating Lacaune ewes were used in a crossover design and received 2 dietary treatments: (1) control: basal diet containing no supplemental lipid and (2) basal diet plus CLA (30g/d). The CLA supplement was mixed into the concentrate and fed in 2 equal meals after morning and afternoon milkings. Each experimental period consisted of 21 d: 7 d for adaptation and 14 d for data collection. The CLA supplement decreased milk fat content and yield by 31.3 and 38.0%, respectively. Milk yield and secretion of milk lactose and protein were decreased by 8.0, 9.8, and 5.6%, respectively. On the other hand, milk protein content and linear SCC score were 1.8 and 17.7% higher in ewes fed the CLA supplement. The concentration of milk fatty acids originating from de novo synthesis (<C16) was decreased by 25%, whereas the concentration of milk fatty acids taken up preformed from the plasma (>C16) was increased by 22.6% in ewes fed the CLA supplement. The CLA supplement decreased C14:1/C14:0, C16:1/C16:0, and C18:1/C18:0 desaturase indexes by 25, 18.7, and 0.1%, respectively, but increased the cis-9,trans-11 CLA/trans-11 C18:1 ratio by 8.6%. The concentrations of trans-10,cis-12 CLA and cis-9,trans-11 CLA in milk fat was 309 and 33.4% higher in ewes fed CLA. Pronounced milk fat depression coupled with the deleterious effects on milk yield, milk SCC, and secretion of all milk solids observed in ewes fed an unprotected CLA supplement is likely to be associated with high doses of trans-10,cis-12 CLA reaching the mammary gland, corroborating previous results obtained with dairy cows.

Temporal feed restriction and overstocking increase competition for feed by dairy cattle

Dairy cows are often overstocked. Some managers are now using “slick bunk” (i.e., feeding for 0% orts) management to save on feed costs, but this reduces the time that cows have access to feed. Both practices may increase competition and affect feeding behavior in dairy cows. The aim was to determine the effects of temporal and spatial restrictions on the feeding and competitive behavior of group-housed cows. Treatments were 2 levels of stocking (2:1 versus 1:1 cows:feed bin) and 2 levels of feed access time (14 versus 24h/d access). Eight groups (each of 6 cows) were tested on each of the 4 treatment combinations for 1 wk, with treatment order assigned using a replicated 4×4 Latin square design. Dry matter intake (DMI), feeding time, and feeding rate were measured for the last 4d of each week, and data were summarized daily and for the 2-h period immediately after the morning feeding. Displacements were recorded for 2h after the delivery of morning feed (peak feeding period) and 2h following the afternoon milking. The DMI did not decline when temporal access was restricted (27.0 vs. 25.7±0.5kg/d), and was not affected by overstocking (26.4±1.9, mean ± SD). Cows with restricted temporal access spent less time feeding (190.9 vs. 207.9±6.1min). Overstocked cows that were temporally restricted had greater feeding rates during the day (156 vs. 137±4g/min) and especially during the peak feeding period (175 vs. 146±4g/min) compared with cows that were not restricted. In the peak feeding period, overstocked cows had reduced DMI (3.0 vs. 3.4±0.1kg/h) and feeding times (20.8 vs. 25.8±1.0min/h) and increased feeding rates (161 vs. 138±4g/min). Cows with restricted temporal access had greater DMI (3.9 vs. 2.6±0.2kg/h) and time spent feeding (27.3 vs. 19.2±1.3min/h) during the peak feeding period compared with cows that had continuous access to feed. Restricting temporal access in conjunction with overstocking resulted in the greatest increase in daily displacements (15.0 vs. 3.8±1.4 displacements/d); the majority of these occurred during the peak feeding period. Adequate space and time to access feed is essential to minimize feed bunk competition in indoor group housing systems.

Effect of solar radiation and flaxseed supplementation on milk production and fatty acid profile of lactating ewes under high ambient temperature

The objectives of this study were to evaluate the effects of protection from solar radiation and whole flaxseed supplementation on milk yield and milk fatty acid profile in lactating ewes exposed to high ambient temperature. The experiment was conducted during summer and involved 40 ewes divided into 4 groups. The ewes were either exposed (not offered shade) or protected from solar radiation (offered shade). For each solar radiation treatment, ewes were supplemented with whole flaxseed or not. Milk samples from each ewe were collected at the morning and afternoon milking every week, and analyzed for pH, total protein, casein, fat, and lactose content, somatic cell count, and renneting parameters (clotting time, rate of clot formation, and clot firmness after 30min). At the beginning of the experiment, and then at d 23 and 44, milk samples were analyzed for milk fatty acids using gas chromatography. Flaxseed supplementation significantly increased milk yield, fat, protein, and casein yields, and somatic cell count, and increased fat and lactose contents of milk. A decrease of saturated fatty acids from C6:0 to C16:0 and an increase of C18:1 trans-11 and C18:2 cis-9,trans-11 was observed in milk from flaxseed-supplemented ewes. Flaxseed supplementation decreased saturated fatty acids content and increased total monounsaturated fatty acids content, the total content of isomers of conjugated linoleic acid, and polyunsaturated fatty acids content in milk. Flaxseed also increased the α-linolenic acid content of milk. As a result, milk from supplemented groups showed an increase in n-3 fatty acid content. Flaxseed supplementation decreased short-chain and medium-chain fatty acids, and increased long-chain fatty acid content of milk. On average, flaxseed supplementation increased the C18:2 cis-9,trans-11/C18:1 trans-11 Δ9-desaturase index starting from d 23 of the experiment, in correspondence with the highest C18:2 cis-9,trans-11 content of milk from flaxseed-supplemented ewes. Flaxseed decreased atherogenic and thrombogenic indices of milk. Protection from solar radiation during summer did not improve yield and composition of ewe milk. Nevertheless, milk from ewes exposed to solar radiation showed decreased long-chain fatty acid and polyunsaturated fatty acids contents, and in particular, decreased vaccenic acid, rumenic acid, and total conjugated linoleic acid contents.