Effect of local stimulation of one quarter on milk production and milk components

Mammary serum amyloid A3 activates involution of the mammary gland in dairy cows

The dry period is a nonlactating phase in which senescent mammary cells are regenerated, which is thought to optimize milk production in the subsequent lactation. In bovines, the dry period normally coexists with pregnancy and the lactogenic hormones delay mammary gland involution and impair the activation of immune system to fight the risk of intramammary infections. Conventionally, long dry periods of up to 60 d are required to allow sufficient mammary regeneration for full milk yield in the next lactation. The aim of this study was to evaluate the potential of mammary serum amyloid A3 (M-SAA3) as an activator of the involution of the mammary gland. One milligram of recombinant M-SAA3 and the corresponding negative controls (saline solution and lipopolysaccharide) were infused into the mammary gland via the teat canal, and mammary secretion samples were taken during the first 3 d after drying off to analyze metalloproteinase activity, somatic cell count, protein, and fat contents. Primary mammary gland epithelial cell cultures and bovine dendritic cells, obtained from necropsy tissue and blood, respectively, were incubated with and without M-SAA3 and cytokine expression was quantified. Last, the protective role of the M-SAA3 against infections was evaluated after a Staphylococcus aureus challenge. Matrix metalloproteinase 9 activity, a key protein that directly participates in the onset of the involution process, was greater in quarters treated with the M-SAA3. Protein content was increased in mammary secretions compared with control quarters. M-SAA3 increased cytokines directly related to innate immunity in both epithelial and dendritic cells and reduced the infection by Staphylococcus aureus.

How does the milk removal method affect teat tissue and teat recovery in dairy ewes?

The aim of this work was to study how machine milking (MM) carried out in suitable conditions affects teat wall thickness and teat canal length and their return after milking to pre-milking conditions, in comparison with other milk extraction methods considered biological referents: lamb suckling (LS), milk removal by catheter (RC) and hand milking (HM). Three Latin square experiments were designed, using 11 ewes in the first experiment (LS), 13 in the second (RC) and 12 in the third (HM). Each of the Latin squares was divided into two periods: in the first, the left gland of each animal was machine milked and the corresponding treatment (LS, RC and HM) was applied to the right gland. Subsequently, in the second period the extraction methods were interchanged. During the experimental period, 4 sampling days were carried out (2 in each experimental period), where ultrasound scans were taken before (B) and immediately after milking (A) and at 1 (1 h), 2 (2 h), 3 (3 h), 4 (4 h), 6 (6 h), 8 (8 h) and 10 (10 h) hours after milking finished. Teat wall thickness (TWT), teat wall area (TWA), teat end area (TEWA) and teat canal length (TCL) were measured in all the ultrasound images. MM increased TWT after milking compared with RC. TWT, TWA, TEWA and TCL were lower (P<0.05) in HM than in MM. No significant differences (P>0.05) were found between LS and MM for any variable. The extraction method affected the recovery time of the variables, with total teat recovery at 6 h after RC and 4 h after HM. In the case of LS, the TEWA and TCL values were recovered sooner, as of 3 h. Teat recovery time after MM was similar to the extraction method with which it was compared in each experiment. Thus, considering the similar increase in wall thickness and their recovery time compared with the reference methods, it was concluded that machine milking, carried out in optimum conditions and respecting the time interval between milkings usually applied on sheep farms (8-12 h), would not affect teat integrity. Moreover, given the variability observed in teat thickness recovery time between the different experiments, further research should be carried out to study which factors intrinsic and extrinsic to the animal may affect the teat wall thickness and recovery time after machine milking.

Effect of different hand-milking techniques on milk production and teat treatment in Zebu dairy cattle

The aim of the study was to test three different hand-milking techniques ("pull down", "thumb in", and "full hand grip") and their effects on milk production and teat treatment. This is important since milk production in many tropical areas still rely on hand-milking. The study was carried out at a peri-urban farm in the Bobo-Dioulasso area in Burkina Faso. Twelve indigenous Zebu cows in early lactation were used in the study. The sequences of the treatments (hand-milking techniques) and the milkers were balanced for carry-over effects between successive periods and days, respectively. The sequences were constructed by using special Latin squares. Yield and composition of saleable milk was not affected by milking technique but there were differences between the milkers in milk yield. There was also a significant interaction for saleable milk yield between milker and milking technique. Hemoglobin in milk was measured as an indicator of teat damage. The hemoglobin content was numerically higher in post-milking strip milk samples than in saleable milk. It was concluded that the amount of milk removed depends mainly on the milker and how well the milking technique works for the individual milker. No effect of milking technique was observed on teat treatment.

Use it or lose it: Enhancing milk production efficiency by frequent milking of dairy cows1

In the past century, great strides have been made toward optimizing milk production efficiency of dairy cows. One of the key findings that has emerged is that the milk yield of dairy cows is responsive to demands of offspring or milk removal; hence, milk production can be increased by frequent milking. Early studies illustrated the galactopoietic effect of frequent milking during the entire lactation, with 3 times daily milking increasing milk yield by up to 20% relative to twice daily milking. Later studies reported that cows produced more milk during the entire lactation if they were allowed to suckle a calf for the first 3 to 4 mo of lactation. The results of these experiments laid the groundwork for current research, which has identified a time during early lactation wherein the mammary gland of dairy cows is especially receptive to the stimulus of frequent milking. This window of time has been slowly whittled down from the first 10 wk of lactation to the first 6 wk, and it was subsequently established that frequent milking for a short duration within the first 3 wk of lactation can increase milk production through the remainder of lactation [corrected] In addition, there is strong evidence that this milk yield response is locally regulated. Consequently, the concept of "use it or lose it" is becoming more clearly established; that is, the stimulus of frequent milking during early lactation permanently increases the milk production capacity of the mammary gland. Exciting research opportunities now present themselves, and ongoing experiments seek to identify the local factors that are involved in the regulation of milk production efficiency of dairy cows.

Mammary Response to Exogenous Prolactin or Frequent Milking During Early Lactation in Dairy Cows

Frequent milking of dairy cows during early lactation results in a persistent increase in milk yield; however, the mechanism underlying this effect is unknown. We hypothesized that increased exposure of the mammary gland to prolactin (PRL) mediates the milk yield response. Fifteen multiparous Holstein cows were assigned to 3 treatments for the first 3 wk of lactation: twice daily milking with (2x + PRL) or without (2x) supplemental exogenous PRL, or 4 times daily milking (4x). Mammary biopsies were obtained at 7 DIM, and rates of [(3)H]thymidine incorporation into DNA in vitro were determined. Mammary expression of suppressors of cytokine signaling (SOCS)-1, -2, and -3; the long form of PRL-receptor; and alpha-lactalbumin mRNA was measured by real-time reverse-transcription PCR. Incorporation of [(3)H]thymidine into DNA was not affected by frequent milking or PRL treatment; however, analysis of autoradiograms revealed that stromal cell proliferation was greater in 4x cows. Mammary expression of SOCS-1 was not affected by milking frequency or PRL treatment. Expression of SOCS-2 mRNA was increased with frequent milking or PRL treatment, whereas expression of SOCS-3 mRNA was reduced by frequent milking or exogenous PRL. Abundance of PRL-receptor mRNA was reduced, whereas alpha-lactalbumin mRNA was increased with PRL treatment. These results demonstrate that the bovine mammary gland is responsive to exogenous PRL during early lactation. In addition, differences in the response to frequent milking or exogenous PRL during early lactation indicate distinct effects of PRL and milk removal on the mammary function of dairy cows.

Endocrinology of milk production

The physiology of lactation includes development of the mammary gland from the foetal to the adult stage, further development during pregnancy and onset of lactation, with the accompanying metabolic and behavioural adaptation. At the onset of pregnancy the endocrine system undergoes dramatic changes. The growth of the mammary gland is stimulated by growth hormone and prolactin, adrenocortical steroids, oestrogens and progesterone, and that of the gastrointestinal (GI) tract by gastrin, CCK and secretin. The onset of lactation is accompanied by increases in the blood volume, cardiac output, mammary blood flow and blood flow through the GI-tract and liver, aiming to provide the udder with nutrients and hormones for regulation of milk synthesis. Food intake and distribution of nutrients to the mammary gland are partially regulated by hormones as well as the repartitioning of nutrients away from body stores towards the udder. To improve milk production, administration of growth hormone has been practised, but also much discussed. Besides central mechanisms, local mechanisms within the mammary gland regulate initiation of lactation, maintenance, regulation of blood flow and mammary gland cell apoptosis. Most of the milk in a filled dairy cow udder is stored in the alveolar compartments. The milk ejection reflex must be activated to gain access to the udder milk, i.e. oxytocin contracts the myoepithelial cells. Recent studies show that vasopressin may also elicit milk ejection. More efficient oxytocin release is achieved if the cows are fed during milking. Beyond milk let down, oxytocin influences maternal behaviour and metabolism. Furthermore, it has been indicated that suckling or milking activates a vagal reflex, which may link the milk production to the endocrine system of the GI-tract. The question has been raised whether the mammary gland is a supporting or consuming organ.

Oxytocin facilitates behavioural, metabolic and physiological adaptations during lactation

The aim of this article is to propose that oxytocin not only stimulates milk let down, but also adapts behaviour and physiology to facilitate lactation in mammals including dairy cattle. Circulating oxytocin as well as neurogenic oxytocin participates in these regulatory processes. In short, oxytocin stimulates maternal interaction and attachment between mother and young. It also participates in the metabolic prerequisites for milk production by e.g. stimulating glucagon release and thereby, mobilisation of glucose. Digestive and anabolic aspects of metabolism are also stimulated, e.g. by increased vagal nerve activity. Adaptations consistent with an antistress like pattern are also induced. Cortisol levels are decreased as well as blood pressure, and behaviours characterised by calm, reduced levels of anxiety and more social activity are promoted. These effects seem to be present in monogastric animals as well as in ruminants. The expression of various aspects of these adaptations vary according to the special needs and living environmental circumstances of different species. The mechanisms behind the effect spectrum of oxytocin are being explored in other experimental models. A second aim of this paper is to suggest that efficiency of lactation can be promoted by facilitating oxytocin release in connection with milking by enhancing the amount of sensory stimulation.

Effect of milking frequency on oxytocin release and milk production in dairy ewes

The experiment was conducted to investigate the effectiveness of milking stimulus on oxytocin release and to compare the effect of milking frequency on plasma levels of oxytocin and milk parameters. Twelve Lacaune ewes were subjected to six treatments (T1, T2, T3, T4, T5 and T7 daily milkings) during 6 days. At each milking, blood was sampled and plasma oxytocin levels were determined by enzyme immunoassay. Baseline levels of oxytocin were similar for all milking frequencies. The start of milking was followed by a significant increase in oxytocin levels for all milking frequencies. One daily milking induced significantly higher oxytocin levels than 2, 3, 4, 5 and 7 daily milkings. Milk yield was significantly increased between 4 (1787.0+/-141.5ml) and 7 (1780.0+/-53.6ml) daily milkings compared to 1 (1104.0+/-81.2ml) daily milking. Total concentration of milk protein did not change, but the total milk fat yield for 5 (73.0+/-2.0g/l) and 7 (72.8+/-1.4g/l) daily milkings were significantly higher than for 1 (58.1+/-4.3g/l) daily milking. This study confirmed milk yield gains caused by frequent milk ejection and also showed that oxytocin release was not a limiting factor for milk yield gain when daily milking frequency was increased.

Endocrine responses in cows milked by hand and machine

Plasma concentrations of oxytocin, prolactin, and cortisol were compared in five Swedish Red and White cows milked by hand versus machine. Cows were divided into two groups. One group was hand-milked; the other group was machine-milked. Treatments were switched every other day. The experiment was carried out for 6 d. Blood samples were taken prior to, during, and after milking and were assayed for hormones. More oxytocin and prolactin were released in hand-milked cows. There were no significant diurnal differences between the total amount of oxytocin released for the different treatments, but prolactin tended to be higher during hand-milking in the evening than in the morning milking. Cortisol concentrations were greater during hand-milking than during machine-milking. There were no significant treatment differences with regard to the total amount of cortisol released. During morning milking, cortisol concentrations were higher during hand-milking than during machine-milking. Our data show that hand-milking results in a pronounced and prolonged release of oxytocin and prolactin.