Seasonal variations of physiological responses, milk production, and fatty acid profile of local crossbred cows in Tunisia

The study investigates the seasonal variations of physiological responses, milk yield, milk composition, and milk fatty acid profile of local crossbred cows (Friesian × Brown Atlas) in northwestern Tunisia. A total of 80 multiparous cows from smallholder farmers were sampled between 2018 and 2019. The cows were feed the same diet ad libitum and exposed to the same Mediterranean climatic conditions. Weekly rectal temperature (RT; °C), respiratory rate (RR; rpm), and heart rate (HR; bpm) were measured per cow in each season. Individual milk yield and samples were recorded bi-weekly and collected in duplicate for chemical analyses. Milk fatty acids (FAs) were analyzed using gas chromatography-mass spectrometry (GC-MS). Results showed an increase (P < 0.05) in RT (+ 1.3%), RR (+ 12.1%), and HR (+ 9.9%) when the temperature-humidity index (THI) increased from winter (53.6) to summer (74.4) in response to heat stress. Milk yield did not vary significantly between seasons (8.3 L/day on average). Summer milk contained more fat (+ 7.8%) and log SCC (+ 13.7%). The proportion of the monounsaturated (31.2 vs. 27.2%) and polyunsaturated (4.29 vs. 3.86%) FAs decreased (P < 0.05) between winter and summer. Saturated FAs (64.5 vs. 67.7%) were higher (P < 0.05) in summer than in winter. Winter milk fat contained higher levels of C18:2cis-9 trans-11 (CLA) (0.73 vs. 0.56%) and ω-3 FA (0.83 vs. 0.63%), but a lower ω-6/ω-3 ratio (4.07 vs. 6.17%) compared to summer. As the cows were fed the same diet throughout the two seasons, the performances obtained were mainly due to the resistance of the local crossbred cow to the hot conditions. It is concluded that the local crossbred cow maintains its productivity and tolerate the hot Mediterranean climate.

When to shear dairy ewes: before breeding, during pregnancy or let them unshorn?

Shearing dairy ewes may improve their fitness and heat tolerance during late pregnancy, with positive effects on lambs and lactation performances. To test this hypothesis, two Mediterranean breeds (MN, Manchega, n = 43; LC, Lacaune, n = 28), differing in lactation performances and fleece traits, were submitted to three shearing strategies: (i) shorn before breeding (SBB), (ii) shorn at day 100 of pregnancy (S100) and (iii) unshorn (CO). Ewes were bred in spring and gestated during summer. Fleece traits and respiratory rate were measured on pregnant (107-121 days) resting ewes at different barn temperatures. Blood and colostrum were sampled at lambing. Ewes suckled their lambs (28 days) and were machine-milked until 180 days of lactation. Lamb and ewe weights, and condition score of the ewes, were recorded throughout the experiment. Milk yield was assessed during suckling (fortnightly) and milking (daily), and milk was sampled for composition (fortnightly). Fleece extension and wool weight at S100 were 13 and 45% greater in MN than in LC ewes, respectively, but the ewe's respiration rate at late pregnancy, between 20 and 25 °C, did not vary among shearing treatments nor breeds. Nevertheless, S100 ewes had a 37% lower respiration rate than SBB and CO ewes at 28 °C. At lambing, SBB and S100 ewes had 86% higher glycaemia than CO in MN, but LC ewes did not vary. Shearing treatment had no effect in plasma insulin, β-hydroxybutyrate or non-esterified fatty acids (NEFAs) at lambing in both breeds. Lamb's birthweight and growth during suckling did not differ by shearing treatment in both breeds. Colostrum composition and milk yield during suckling were not modified by shearing treatment in either breed, although S100 suckling milk composition increased in MN (protein and casein, 6%) and LC ewes (total solids, 8%; fat, 18%), compared to CO and SBB. No effects were detected in milk yield or composition during milking, but S100 tended to yield 28% more milk than CO in the LC ewes. The S100 treatment improved the body reserves in late pregnancy, when compared to CO and SBB in both breeds. In conclusion, shearing dairy ewes in late pregnancy was a recommendable management practice under summer conditions, because alleviated heat stress and improved the weight of the ewes, without detrimental effects on lambing and lactational performances, the last tending to increase milk yield in high-yielding dairy ewes.

Responses to melatonin of 2 breeds of dairy ewes in early lactation under autumn photoperiod conditions

A total of 72 dairy ewes of 2 breeds (MN, Manchega, 72.4 ± 1.9 kg of body weight, n = 36; LC, Lacaune, 77.7 ± 2.3 kg of body weight; n = 36) were used to evaluate the lactational effects of melatonin implants in early lactation and under the short-day photoperiod conditions of autumn (experiment was centered on the winter solstice). Ewes lambed in autumn and were penned indoors in 12 balanced groups of 6 ewes by breed, body weight, age, and number of lambs, and randomly assigned to a 2 × 2 × 3 factorial design (treatment × breed × replicate). Ewes suckled their lambs for 28 d. Treatments were (1) melatonin (MEL), which received 1 subcutaneous implant of melatonin (18 mg/ewe) in the ear base at 35 ± 1 d (1 wk after lamb weaning), and (2) control, which did not receive any treatment. Ewes were fed ad libitum a total mixed ration (forage:concentrate, 60:40) and machine milked twice daily. Daily milk yield was automatically recorded from d 29 to 105 of lactation and sampled every 2 wk for composition. Jugular blood was sampled for plasma hormone analyses at 30, 50, 80, 110, and 124 d of lactation. Body reserves were assessed every 2 wk. Feed intake was measured by pen during 3 separated periods after the start of the treatments (wk 2 to 3, wk 6 to 7, and wk 10 to 11). Feed intake, and milk yield and composition varied by breed, but no MEL effects were detected on dry matter intake, milk yield, milk composition, or fat and protein standardized milk in either breed. As a result of the unique composition of the implants and the variable body weights of the ewes, the MEL treatment dose (on average, 0.24 mg/kg of body weight) was 6.8% greater in the MN (lighter) than in the LC (heavier) ewes. Plasmatic melatonin markedly increased in the MEL-treated ewes (on average, 111%), but despite the amount of MEL used, the MN responded greatly compared with the LC ewes (150 vs. 63%, respectively). No differences in basal plasmatic melatonin were detected between breeds (6.4 ± 1.1 pg/mL, on average), indicating the greater responsiveness to the implants of the lighter MN ewes. Plasmatic prolactin tended to decrease in the MEL-treated ewes (-35%, on average), but the effect was significant only in the MN ewes (-54%), in agreement with their greater response to MEL. No effects of MEL treatment were detected on plasmatic IGF-I in either breed. Moreover, body reserves did not vary by effect of MEL treatment or breed throughout the experiment. In conclusion, the use of exogenous melatonin as MEL implants, together with the endogenous melatonin naturally produced under short-day photoperiod conditions, had no effects on the early-lactation performances of dairy sheep, despite their breed and level of production.

Suppression of prolactin and reduction of milk secretion by effect of cabergoline in lactating dairy ewes

The effects of cabergoline, an ergot derivative and dopamine receptor agonist, were investigated in 30 ewes of 2 dairy breeds (Manchega; MN, n = 15; Lacaune; LC, n = 15). Ewes were in a similar late-lactation stage, but differed in milk yield according to breed (MN vs. LC, 1.02 ± 0.03 vs. 2.27 ± 0.05 kg/d). Treatments consisted of a single intramuscular injection of cabergoline at different doses per ewe. Cabergoline doses (per ewe) were: low (0.56 mg), high (1.12 mg), and control (CON; 0 mg; 1 mL of saline). Milk yield was recorded daily (d -14 to 25), milk and blood were sampled, and udder traits were measured from d -2 to 14 after injection. No local reaction at the injection site, nor behavior and metabolic indicators of the ewes were detected after the cabergoline injection, but milk yield fell rapidly in both breeds (MN vs. LC, -54% vs. -27%) when compared with CON ewes. Cabergoline effects progressively disappeared after d 5, and no milk yield differences between treatments were detected from d 8 to 25 after injection. Milk fat and protein contents increased similarly (22% and 23%; respectively) in both breeds and at both cabergoline doses until d 5, and the effects disappeared thereafter. Plasma prolactin (PRL) decreased dramatically in the low- and high-treated ewes the day after injection when compared with the CON ewes, and reached values below the detection limit of the assay between d 1 and 5, increasing similarly thereafter. On d 14, PRL values were 58% greater in the low- and high-treated than in the CON ewes, showing that PRL concentrations rebounded when the cabergoline effects ceased. Total udder volume correlated with milk accumulated in the udder (r = 0.77) of all groups of ewes throughout the experiment, suggesting its use as a noninvasive method for the estimation of milk stored in the udder. Udder volume was similar for the low and high ewes, but both values were lower than those of the CON ewes from d 1 to 14 after injection. No other effects on udder size were detected. Cabergoline dramatically inhibited PRL secretion and decreased milk yield and udder volume of lactating dairy ewes. The low dose of cabergoline was as effective as the high dose in the 2 breeds of dairy ewes. These results suggest the use of cabergoline to facilitate the decrease of milk production in dairy ewes (e.g., dry-off, illness care), although further research in pregnant dairy ewes and during the following lactation is still needed.

Enhanced supply of methionine or arginine alters mechanistic target of rapamycin signaling proteins, messenger RNA, and microRNA abundance in heat-stressed bovine mammary epithelial cells in vitro

Heat stress (HS) causes reductions in milk production, but it is unclear whether this effect is due to reduced number or functional capacity (or both) of mammary cells. Methionine supplementation improves milk protein, whereas Arg is taken up in excess by mammary cells to produce energy and nonessential AA that can be incorporated into milk protein. To evaluate molecular mechanisms by which mammary functional capacity is affected by HS and Met or Arg, mammary alveolar (MAC-T) cells were incubated at thermal-neutral (37°C) or HS (42°C) temperatures. Treatments were optimal AA profiles (control; Lys:Met = 2.9:1.0; Lys:Arg = 2.1:1.0), control plus Met (Lys:Met = 2.5:1.0), or control plus Arg (Lys:Arg = 1.0:1.0). After incubation for 6 h, cells were harvested and RNA and protein were extracted for quantitative real-time PCR and Western blotting. Protein abundance of mechanistic target of rapamycin (MTOR), eukaryotic initiation factor 2a, serine-threonine protein kinase (AKT), 4E binding protein 1 (EIF4EBP1), and phosphorylated EIF4EBP1 was lower during HS. The lower phosphorylated EIF4EBP1 with HS would diminish translation initiation and reduce protein synthesis. Both Met and Arg had no effect on MTOR proteins, but the phosphorylated EIF4EBP1 decreased by AA, especially Arg. Additionally, Met but not Arg decreased the abundance of phosphorylated eukaryotic elongation factor 2, which could be positive for protein synthesis. Although HS upregulated the heat shock protein HSPA1A, the apoptotic gene BAX, and the translation inhibitor EIF4EBP1, the mRNA abundance of PPARG, FASN, ACACA (lipogenesis), and BCL2L1 (antiapoptotic) decreased. Greater supply of Met or Arg reversed most of the effects of HS occurring at the mRNA level and upregulated the abundance of HSPA1A. In addition, compared with the control, supply of Met or Arg upregulated genes related to transcription and translation (MAPK1, MTOR, SREBF1, RPS6KB1, JAK2), insulin signaling (AKT2, IRS1), AA transport (SLC1A5, SLC7A1), and cell proliferation (MKI67). Upregulation of microRNA related to cell growth arrest and apoptosis (miR-34a, miR-92a, miR-99, and miR-184) and oxidative stress (miR-141 and miR-200a) coupled with downregulation of fat synthesis-related microRNA (miR-27ab and miR-221) were detected with HS. Results suggest that HS has a direct negative effect on synthesis of protein and fat, mediated in part by coordinated changes in mRNA, microRNA, and protein abundance of key networks. The positive responses with Met and Arg raise the possibility that supplementation with these AA during HS might have a positive effect on mammary metabolism.

Comparison of visual and electronic devices for individual identification of dromedary camels under different farming conditions

The camel industry uses traditional (i.e., iron brands and ear tags) and modern (i.e., microchips) identification (ID) systems without having performance results of reference. Previously iron-branded ( = 45; 1 yr) and microchipped ( = 59; 7 yr) camels showed problems of healing (8.6% of brands) and reading (only 42.9% of brands and 69.5% of microchips were readable), which made their use inadvisable. With the aim of proposing suitable ID systems for different farming conditions, an on-field study was performed using a total of 528 dromedaries at 4 different locations (Egypt, = 83; Spain, = 304; Saudi Arabia, = 90; and Tunisia, = 51). The ID devices tested were visual (button ear tags, 28.5 mm diameter, = 178; double flag ear tags, 50 by 15 mm, = 83; both made of polyurethane) and electronic (ear tags, = 90, and rumen boluses, = 555). Electronic ear tags were polyurethane-loop type (75 by 9 mm) with a container in which a 22-mm transponder of full-duplex technology was lodged. Electronic boluses of 7 types, varying in dimensions (50 to 76 mm length, 11 to 21 mm width, and 12.7 to 82.1 g weight) and specific gravity (SG; 1.49 to 3.86) and each of them containing a 31-mm transponder of half-duplex technology, were all administered to the dromedaries at the beginning of the study. When a low-SG bolus was lost, a high-SG bolus was readministered. Readability rates of each ID system were evaluated during 1 to 3 yr, according to device and location, and yearly values were estimated for comparison. On a yearly basis, visual ear tag readability was not fully satisfactory; it was lower for rectangular ear tags (66.3%) than for button ear tags (80.9%). Yearly readability of electronic ear tags was 93.7%. Bolus readability dramatically varied according to their SG; the SG < 2.0 boluses were fully lost after 8 mo. In contrast, the SG > 3.0 boluses were efficiently retained (99.6 to 100%) at all locations. In conclusion, according to the expected long lifespan of camels, low ID performances were observed for iron brands, injectable microchips, and ear tags (visual and electronic), making their use inadvisable as unique ID systems in camels. The high readability of dense electronic boluses recommended their use as a permanent ID device of reference in camels.

Implementing electronic identification for performance recording in sheep: II. Cost-benefit analysis in meat and dairy farms

Costs and secondary benefits of implementing electronic identification (e-ID) for performance recording (i.e., lambing, body weight, inventory, and milk yield) in dairy and meat ewes were assessed by using the results from a previous study in which manual (M), semiautomatic (SA), and automatic (AU) data collection systems were compared. Ewes were identified with visual ear tags and electronic rumen boluses. The M system used visual identification, on-paper data recording, and manual data uploading to a computer. The SA system used e-ID with a handheld reader in which performances were typed and automatic uploaded to a computer. The use of a personal digital assistant (PDA) for recording and automatic data uploading, which transformed M in a SA system, was also considered. The AU system was only used for BW recording and consisted of e-ID, automatic data recording in an electronic scale, and uploading to a computer. The cost-benefit study was applied to 2 reference sheep farms of 700 meat ewes, under extensive or intensive production systems, and of 400 dairy ewes, practicing once- or twice-a-day machine milkings. Sensitivity analyses under voluntary and mandatory e-ID scenarios were also included. Benefits of using e-ID for SA or AU performance recording mainly depended on sheep farm purpose, number of test days per year, handheld reader and PDA prices, and flock size. Implementing e-ID for SA and AU performance recording saved approximately 50% of the time required by the M system, and increased the reliability of the data collected. Use of e-ID increased the cost of performance recording in a voluntary e-ID scenario, paying only partially the investment made (15 to 70%). For the mandatory e-ID scenario, in which the cost of e-ID devices was not included, savings paid 100% of the extra costs needed for using e-ID in all farm types and conditions. In both scenarios, the reader price was the most important extra cost (40 to 90%) for implementing e-ID in sheep farms. Calculated extra costs of using the PDA covered more than 100% of the implementation costs in all type of sheep farms, indicating that this device was cost-effective for sheep-performance recording.

Thermographic variation of the udder of dairy ewes in early lactation and following an Escherichia coli endotoxin intramammary challenge in late lactation

A total of 83 lactating dairy ewes (Manchega, n=48; Lacaune, n=35) were used in 2 consecutive experiments for assessing the ability of infrared thermography (IRT) to detect intramammary infections (IMI) by measuring udder skin temperatures (UST). In experiment 1, ewes were milked twice daily and IRT pictures of the udder were taken before and after milking at 46 and 56d in milk (DIM). Milk yield was 1.46 ± 0.04 L/d, on average. Detection of IMI was done using standard bacterial culture by udder half at 15, 34, and 64 DIM. Twenty-two ewes were classified as having IMI in at least one udder half, the others being healthy (142 healthy and 24 IMI halves, respectively). Four IMI halves had clinical mastitis. No UST differences were detected by IMI and udder side, being 32.94 ± 0.04°C on average. Nevertheless, differences in UST were detected for breed (Lacaune - Manchega=0.35 ± 0.08°C), milking process moment (after - before=0.13 ± 0.11°C), and milking schedule (p.m. - a.m.=0.79 ± 0.07°C). The UST increased linearly with ambient temperature (r=0.88). In experiment 2, the UST response to an Escherichia coli O55:B5 endotoxin challenge (5 μg/udder half) was studied in 9 healthy Lacaune ewes milked once daily in late lactation (0.58 ± 0.03 L/d; 155 ± 26 DIM). Ewes were allocated into 3 balanced groups of 3 ewes to which treatments were applied by udder half after milking. Treatments were (1) control (C00, both udder halves untreated), (2) half udder treated (T10 and C01, one udder half infused with endotoxin and the other untreated, respectively), and (3) treated udder halves (T11, both udder halves infused with endotoxin). Body (vaginal) temperature and UST, milk yield, and milk composition changes were monitored by udder half at different time intervals (2 to 72 h). First local and systemic signs of IMI were observed at 4 and 6h postchallenge, respectively. For all treatments, UST increased after the challenge, peaking at 6h in T 0055 (which differed from that in C00, C01, and T10), and decreased thereafter without differences by treatment. Vaginal temperature and milk somatic cell count increased by 6h postchallenge, whereas lactose content decreased, in the endotoxin-infused udder halves. Effects of endotoxin on lactose and somatic cell count values were detectable in the infused udder halves until 72 h. In conclusion, despite the accuracy of the camera (± 0.15°C) and the moderate standard errors of the mean obtained for UST measures (± 0.05 to 0.24°C), we were unable to discriminate between healthy and infected (subclinically or clinically) udder halves in dairy ewes.

Physiological responses and lactational performances of late-lactation dairy goats under heat stress conditions

Eight Murciano-Granadina dairy goats in late lactation were exposed to different ambient conditions, using metabolic cages in a climatic chamber. The experimental design was a crossover (2 periods of 35 d and 4 goats each) and conditions were (1) thermal neutral (TN; 15 to 20 °C day-night) and (2) heat stress (HS; 12-h day at 37 °C and 12-h night at 30.5 °C). Humidity was maintained at 40% and light-dark was constant (12-12h). The forage:concentrate ratio was adjusted daily for maintaining similar value in TN and HS goats (70:30). Water was freely available at ambient temperature. Rectal temperature and respiratory rate (0800, 1200 and 1700 h) and milk yield were recorded daily, whereas milk composition, nonesterified fatty acids and haptoglobin in blood were analyzed weekly. At d 25, additional blood samples were taken for analysis of metabolites and indicators of the acid-base balance. Digestibility coefficients and N balance were determined (d 31 to 35) and body weight was recorded (d 35). Compared with TN goats, HS goats experienced greater rectal temperature (+0.58 °C), respiratory rate (+48 breaths/min), water intake (+77%) and water evaporation (+207%). Intake of HS goats rapidly declined until d 7 (-40%), partially recovered from d 7 to 19, and steadied thereafter (-14%). No changes in digestibility or N balance were detected. Blood nonesterified fatty acids and haptoglobin peaked at d 7 in HS goats but did not vary thereafter. Although milk yield did not vary by treatment, milk of HS goats contained -12.5% protein and -11.5% casein than TN goats. Panting reduced concentration and pressure of CO₂ in the blood of HS goats, but they were able to maintain their blood pH similar to the TN group by lowering HCO₃(-) and increasing Cl(-) concentrations in their blood. In conclusion, HS dairy goats showed dramatic physiological changes during the first week of treatment and partially recovered thereafter. They were able to maintain milk yield by losing body mass, but milk protein content and protein yield were depressed. Further research is needed to assess the response of dairy goats to HS at earlier stages of lactation.

Readability of visual and electronic leg tags versus rumen boluses and electronic ear tags for the permanent identification of dairy goats

Murciano-Granadina dairy goats (n=220) were used to assess the performance of visual and electronic identification devices: 1) leg tags (LT) on the shank of the right hind leg (metatarsus) consisting of plastic bands (181 × 39mm, 21g; n=220) printed with a 3-digit code and closed with 2 types of electronic button tags (ET1, 3.9 g, 26 mm o.d., n=90; ET2, 5.5 g, 25 mm o.d., n=130); 2) electronic rumen boluses (RB, 75 g, 68 × 21 mm, n=220) containing 32 × 3.8 mm transponders; 3) electronic ear tags (EE, button-button, 4.8 g, 24 mm, n=47); and 4) visual plastic ear tags (VE, flag-button, 4.2 g, 40 × 38 mm, n=220). The shank circumference of 47 replacement kids (5 to 6 mo of age) and 103 adult goats was measured to evaluate the proper circumference for fastened LT. Goats were identified with RB and VE before the experiment. Time for leg tagging, reading, and data recording with a handheld transceiver was measured. Readability [(read/readable) × 100] was monitored for 1 yr with goats restrained in the milking parlor. Reading time and errors of RB and ET2 in the milking parlor using the handheld transceiver were recorded. Shank circumference of kids (70±1 mm) was 79.5% of that in adult goats (88±1 mm), thus LT (107±1 mm inner circumference) were only applied to adult goats as they were inadequate for 6-mo-old kids. Time for leg tagging and data recording was 53±3 s. At 1 yr, readability of RB was 96.5%. No LT losses occurred and all were visually readable, although 3 (1.5%) had to be removed due to limping, leading to a final LT retention of 98.5%. Moreover, 7 (3.6%) LT were found open and electronically unreadable. Readability of button transponders, excluding removed LT, was 93.6% (3 lost and 2 unreadable) for ET1, and 98.3% (2 lost) for ET2. Readability was 95.7 and 97.0% in EE and VE ear tags, respectively. Only LT and ET1 readabilities differed. Reading time and reading errors (0.3 vs. 0%) in the milking parlor were greater for RB (61.2s) than for ET2 (45.9s). In conclusion, LT were not adequate for the identification of goat kids under 6 mo of age. Only LT with ET2 transponders met International Committee for Animal Recording requirements for official identification of adult goats (readability >98%) under the conditions of this experiment.

Long- and short-term effects of omitting two weekend milkings on the lactational performance and mammary tight junction permeability of dairy ewes

The long- and the short-term effects of omitting 2 milkings weekly in early (wk 8 to 14) and mid lactation (wk 15 to 22) were investigated in an experiment conducted with a total of 58 dairy ewes (40 Manchega and 18 Lacaune). Ewes submitted to 2 milking omissions were milked twice daily from Monday to Friday (0800 and 1800 h), and once daily on Saturday and Sunday (1600 and 1400 h, respectively). Individual data were collected for milk yield (weekly), milk composition (biweekly), and somatic cell count (SCC; monthly). Omitting 2 milkings per week in early lactation tended to decrease milk yield in Manchega ewes (-15%), whereas no effects were observed in Lacaune ewes. Averaged milk composition was not modified by milking omissions in either breed. Milking omissions in late lactation did not affect milk yield and milk composition in either breed. The SCC were unaffected by milking omissions in both breeds and in both stages of lactation. A sample of 22 Manchega and 11 Lacaune ewes were used to evaluate the short-term (daily) effects of the 2 milking omissions per week on milk yield and composition, udder health, and tight junction permeability, both in early lactation (wk 12) and in mid lactation (wk 20). Milking omission decreased milk yield, milk fat, and milk lactose contents on the first omission day in both breeds, with losses being more noticeable in early lactation than in mid lactation. Milk protein content and SCC did not vary by effect of the weekend milking omissions. After restoring the twice-daily milking routine on Monday, milk yield showed a compensatory increase that was greater in the large-cisterned than in the small-cisterned ewes, which allowed milk yield to return to Friday values in both breeds. Milk fat content increased during Sunday and Monday, reestablishing Friday values thereafter in both breeds. Weekend milking omissions in early lactation caused tight junction leakiness in both breeds, but mammary epithelia adapted to extended milking intervals when applied successively, recovering their tight state after milking. In mid lactation, the mammary tight junction showed leakiness only in Manchega ewes. In conclusion, 2 milkings per week could be omitted with no negative effects on milk yield, milk composition, and milk SCC values in large-cisterned dairy ewes, as observed in Lacaune and large-cisterned Manchega ewes. Losses in milk yield could be reduced if milking omissions were done from mid lactation in small-cisterned ewes.

Changes in alveolar and cisternal compartments induced by milking interval in the udder of dairy ewes

The aim of this work was to evaluate the effects of milking interval (4, 8, 12, 16, 20, and 24 h) on cisternal size and milk partitioning (cisternal and alveolar) in the udders of dairy ewes. Twenty-four dairy ewes (Manchega, n = 12; Lacaune, n = 12) were used in a 2-wk experiment during mid-lactation. Cisternal and alveolar milk yields were measured and milk samples from each udder fraction were collected for analysis. Cisternal milk was obtained after i.v. injection of an oxytocin receptor antagonist, and alveolar milk was obtained after i.v. injection of oxytocin. Enlargement of the cisternal compartment due to milking intervals was measured by ultrasonography for each half udder. Volumes of cisternal and alveolar milk differed according to breed, being greater in Lacaune (888 +/- 43 and 338 +/- 25 mL, respectively) than in Manchega ewes (316 +/- 43 and 218 +/- 25 mL, respectively). Alveolar milk increased linearly to 16 h in Manchega and 20 h in Lacaune and remained constant thereafter. Cisternal milk accumulated linearly to 24-h milking intervals in both breeds. Cisternal area (values per udder half) increased as milking interval increased, reaching a plateau at 20 h in Manchega (21 +/- 1 cm(2)) and 16 h in Lacaune (37 +/- 1 cm(2)). Correlation between cisternal area and cisternal milk was the greatest at 8 h (Manchega: r = 0.70 and Lacaune: r = 0.56). Cisternal area correlated with total milk (r = 0.80). Milk fat content varied markedly with milking intervals, increasing in alveolar milk (until 12 h in Manchega, 8.90 +/- 0.18%; and 20 h in Lacaune, 8.67 +/- 0.19%) and decreasing until 24 h in cisternal milk (5.74 +/- 0.29% and 4.85 +/- 0.29%, respectively). Milk protein content increased in alveolar milk until 24 h (Manchega, 6.46 +/- 0.11%; Lacaune, 5.95 +/- 0.11%), but did not vary in cisternal milk. Milk lactose content only decreased at the 24-h milking interval in the cisternal milk of Manchega ewes (4.60 +/- 0.04%). In conclusion, our results suggest that cisterns play an important role in accommodating secreted milk during extended milking intervals. Thus, long milking intervals could be a recommended strategy for large-cisterned dairy sheep. Evidence indicates that ultrasonography provides accurate estimations of udder cistern size and could be used as an indicator for selecting large-cisterned dairy ewes.

Omitting the dry-off period negatively affects colostrum and milk yield in dairy goats

Seventeen pregnant multiparous Murciano-Granadina dairy goats, kept in a semi-intensive exploitation system with once daily milking throughout lactation and 1 kidding per year (milk yield, 577 L/300 d), were used to study the effects of dry-off period length on performance during the subsequent lactation. Goats were mated at wk 29 of lactation and were assigned to 2 experimental groups according to dry-off treatment: goats that were dried off 56 d before expected kidding (D56; n = 9) and goats without dry-off (D0; n = 8). After parturition, kids were removed from their mothers and weighed before suckling. Goats were hand milked to obtain colostrum and were machine milked thereafter. Colostrum was sampled for composition and IgG analysis. Milk yield was recorded weekly during the preceding and subsequent lactations. Udders were biopsied in a sample of goats at d -65 (late lactation), d -49 (during dry-off), and d 48 (early lactation) to kidding (d 0). Apoptotic and proliferating cells in mammary tissues were detected immunohistochemically. Five goats (63%) in the D0 group dried off spontaneously at 27 +/- 4 d before kidding and were considered separately (D27). The rest of the D0 goats yielded 0.86 L/d from d -56 to kidding. Goats kidded 2.25 kids/goat, but the D0 kids had smaller birth weights (1.7 kg) than the D27 (2.2 kg) and D56 (2.1 kg) kids. Colostrum of the D0 goats contained less IgG (5.6 mg/mL) than the D27 (32.9 mg/mL) and the D56 (42.4 mg/mL) goats. In the subsequent lactation (210 d), the D0 goats produced less milk (1.78 L/d) than the D27 (2.51 L/d) and D56 (2.24 L/d) goats, with no detectable difference between the D27 and D56 goats. Apoptosis and proliferation indices increased from 0.51 and 2.09%, at d -65, to 1.75 and 7.12% at d -49 (d 7 of dry-off) in D56 goats. Despite differences in daily milk yield during early lactation (d 48) between the D0, D27, and D56 treatments (1.73, 2.68, and 2.53 L/d, respectively), no differences in apoptosis or proliferation indices were detected (D0: 0.65 and 2.48%; D27: 0.68 and 1.37%; and D56: 0.71 and 2.95%), indicating that duration of the dry period did not affect mammary cell turnover during the subsequent lactation. Omitting the dry period between lactations reduced the quality of colostrum and had negative effects on milk yield in dairy goats. Goats dried off spontaneously for 27 d were as productive as goats dried off for 56 d, indicating that less than 2 mo of dry-off may be sufficient in practice.

Mammogenesis and induced lactation with or without reserpine in nulliparous dairy goats

Nulliparous goats were used to evaluate the effects of a standard protocol for inducing lactation with or without using a prolactin-releasing agent (reserpine). Estrus was synchronized and goats were submitted to daily s.c. injections of estradiol-17beta and progesterone (0.5 and 1.25 mg/kg of body weight, respectively) for 7 d. The goats were divided into 2 groups and injected i.m. with 1 mg/d of reserpine (n = 7) or the vehicle (n = 7) on d 12, 14, 16, 18, and 20. Lactation was initiated by i.m. injections of dexamethasone (10 mg/d) from d 18 to 20. Goats were machine milked once daily from d 21 to 120, at which time they were mated with herd sires. Milk was measured and sampled daily during wk 1 of lactation and weekly thereafter. Udder traits were measured in all goats at d -2 (before the induction treatment) and on d 35 and 100 (during lactation). Goats initiated lactation on d 21 (100%) and milk yield increased thereafter. The milk yield of control and reserpine-treated goats increased as lactation advanced, peaking at wk 10 of lactation, when reserpine-treated goats yielded 1,079 +/- 89 mL/d of milk compared with 850 +/- 96 mL/d for control goats. Yet milk yield at the peak was only 55% of the peak milk yield observed in contemporary primiparous goats. The composition of initial milk (d 21) was different from that expected for colostrum. Milk composition stabilized after d 3 of lactation. There were no differences among groups for milk fat, protein, casein, or whey protein, but milk from control goats contained greater nonprotein nitrogen than that from reserpine-treated goats (0.48 +/- 0.02 vs. 0.41 +/- 0.02%). Teat length increased from 24.7 +/- 1.1 to 34.5 +/- 2.4 mm in control goats during mammogenesis (d -2 to 35), but stabilized in reserpine goats (25.2 +/- 2.2 mm). The distance between teats (11.5 +/- 0.4 cm), and the volume (922 +/- 63 mL) and depth (15.6 +/- 0.60 cm) of the udder increased similarly in both groups during mammogenesis and lactation. After mating, 82% of herdmates became pregnant, whereas only 21% of the lactation-induced goats conceived (1 reserpine-treated and 2 control goats). In conclusion, lactation induction was effective in nulliparous goats, but neither milk yield nor the side effects on fertility seem to support its recommendation.

Effect of pregnancy and extended lactation on milk production in dairy goats milked once daily

Thirty multiparous Murciano-Granadina dairy goats milked once daily were used to study the lactational effects of an extended 24-mo kidding interval (K24; n = 14) compared with the traditional 12-mo kidding interval (K12; n = 16). Goats were divided into 2 groups at wk 29 of lactation balanced with respect to parity, milk yield, and somatic cell count. Over a period of 92 wk, K12 goats were mated twice, at wk 29 during the first lactation and at wk 79 during the second lactation, whereas K24 goats were mated once, at wk 79 of extended first lactation. The K12 goats were dried off from wk 14 to 21 of pregnancy (wk 43 to 50 of lactation). Milk yield was recorded from wk 2 to 92, and milk composition was studied from wk 29 to 92. Milk fatty acids were analyzed in milk samples taken at wk 39 (wk 10 of pregnancy) and 55 (wk 5 of subsequent lactation), when milk in udder compartments (cisternal and alveolar) was also evaluated. Average milk yield during the first 29 wk was 2.23 +/- 0.13 L/d. Pregnancy reduced milk yield in K12 goats from wk 39 to 42 of lactation compared with K24 goats. During the dry period for K12 goats, milk yield of K24 goats averaged 1.53 +/- 0.10 L/d. From wk 51 to 79, K12 goats produced 32% more milk than did K24 goats, but their milk contained lower fat and protein than that of K24 goats. No changes were detected for milk lactose and somatic cell count from wk 51 to 79. From wk 80 to 92, differences in milk yield and milk composition between groups were not significant. Milk of pregnant K12 goats contained higher C16:1 and conjugated C18:2 fatty acids, and had a higher desaturase index than milk of open K24 goats at wk 39. In the following lactation (wk 55), milk of K12 goats contained higher C18:2 and C18:3, and lower C16:0 fatty acids, resulting in a lower atherogenicity index compared with K24 goats. Cisternal milk at wk 39 was lower for K12 than K24 goats, whereas alveolar milk did not differ. In K12 goats, values of cisternal milk tripled, but alveolar milk only doubled at wk 55 (wk 5 of subsequent lactation) compared with wk 39, indicating the importance of the cistern in accommodating high milk yield in early lactation. Values of cisternal and alveolar milk did not differ between wk 39 and 55 for K24 goats. Fat content was higher for alveolar milk than cisternal milk for K12 goats at wk 55 and for K24 goats at wk 39 and 55. No differences in milk protein or lactose were detected between cisternal and alveolar milk. In conclusion, pregnancy reduced milk yield from wk 10 after conceiving onwards. Extended lactation did not significantly decrease milk yield (-8.2%), but increased milk components that may contribute to cheese yield, and may be a useful strategy for reducing metabolic stress in early lactation and for simplifying herd management in dairy goats.

Changes in Cisternal Udder Compartment Induced by Milking Interval in Dairy Goats Milked Once or Twice Daily

Fourteen Murciano-Granadina dairy goats were used to evaluate udder compartments (cisternal and alveolar) and cisternal recoil after an oxytocin (OT) challenge at different milking intervals (8, 16, and 24 h) during wk 7 of lactation. Goats were milked once (1x; n = 7) or twice (2x; n = 7) daily from wk 2 of lactation. Average milk yields for wk 4 and 8 were 1.76 and 2.24 L/d, for goats milked 1x and 2x, respectively. For each half udder, cisternal area was measured by ultrasonography and cisternal milk was measured by machine milking after i.v. injection of an OT receptor blocking agent. Alveolar milk was then obtained after i.v. injection of OT. Regardless of milking frequency, alveolar milk increased from 8 to 16 h after milking, but did not change thereafter. Cisternal area and cisternal milk increased linearly (R2 = 0.96 to 0.99) up to 24 h, indicating continuous milk storage in the cistern at any alveoli filling degree. Cisternal to alveolar ratio increased with milking interval (from 57:43 to 75:25), but differences between milking intervals were significant at 8 h only, at which time goats milked 2x showed a greater ratio (1x = 51:49; 2x = 62:38). Despite extended milking intervals, cisterns of goats milked 1x did not become larger than cisterns of goats milked 2x after 5 wk of treatment. The highest correlation between cisternal area and cisternal milk was detected at 8 h after milking (r = 0.74). Primiparous goats had smaller cisternal areas and less cisternal milk than multiparous goats at all milking intervals. Cisternal recoil was studied in a sample of multiparous goats milked 1x (n = 4) and 2x (n = 4) by scanning cisterns by ultrasonography at 0, 5, 15, and 30 min after an OT challenge for each milking interval. Cisternal area increased after OT injection for the 8- and 16-h milking intervals, but no differences were observed for the 24-h interval. Unlike cows, no changes in cisternal area were observed after OT injection, indicating the absence of cisternal recoil in goats. We conclude that goats show a large cisternal compartment that increases linearly after milking. Nevertheless, cisternal size did not increased after 1x milking, probably because of lesser milk yield. Multiparous goats had larger cisterns than primiparous goats and were able to store more milk in their cisterns at all milking intervals. Because of the high capacity of goat cisterns, no milk return from cistern to alveoli is expected if milking is delayed after milk letdown.

Effects of once versus twice daily milking throughout lactation on milk yield and milk composition in dairy goats

The effects of once (1X) vs. twice (2X) daily milking throughout lactation on milk yield, milk composition, somatic cell count (SCC), and udder health were studied in 32 Murciano-Granadina dairy goats. Goats were assigned at wk 2 of lactation to two treatment groups; once daily milking at 0900 (1X, n = 17), or twice daily milking at 0900 and 1700 (2X, n = 15). Milk yield was recorded weekly until wk 28, and milk composition and SCC were evaluated for each individual udder half at each milking at wk 2 and 4 of lactation and then, monthly until the end of the experiment. Once daily milking resulted in an 18% reduction in the yield of 4% fat-corrected milk compared to twice daily milking (1.61 vs. 1.95 L/d, respectively). This reduction was more marked from wk 2 to 12 than in mid and late lactation. Response to milking frequency also varied according to parity number where goats of less than four parities suffered more milk yield losses during 1X than older goats. Milk of 1X goats contained higher percentages of total solids (13.6 vs. 12.9%), fat (5.10 vs. 4.62%) and casein (2.57 vs. 2.35%) than milk of 2X goats, but milk protein percentage did not differ between treatments (3.28 vs. 3.20%). Yields of total solids, fat, protein and casein tended to be higher for 2X than 1X. Milk SCC did not differ between treatments. We conclude that application of once daily milking in Murciano-Granadina dairy goats moderately reduced milk yield without negative effects on milk composition and udder health. Losses in milk yield would be reduced if 1X is practiced during mid- or late lactation and in older goats. An increase in labor productivity and a higher farmer's standard of living is also expected.