Pregnancy Obstructs Involution Stage II of the Mammary Gland in Cows: General Biological Implications

*Background*
Repeated research findings over the last 4 decades show that involution of mammary glands in dairy cows did not regress to same extend as that noticed in other mammalian species.

*Methodology/Principal Findings*
We took an advantage of a rare event in the normal modern dairy farming: A cow that was false-positively identified as being pregnant was "dried up" (i.e., induced into involution) conventionally about 60 before her expected parturition. This cow was culled, and samples of her mammary gland tissue were examined for gross histology. In this study we demonstrate for the first time that modern dairy cow may undergo extensive obliteration of the lobular-alveolar structure, as expected in involution stage II. 

*Conclusions/Significance*
We conclude that lack of histological evidence for the appearance of involution stage II in the vast majority of modern cow's population is related to the peculiar modern dairy husbandry, in which dairy cows are induced into involution still pregnant. Because retardation of involution stage II in pregnant mammals is most likely a general physiological phenomena, it might occurs in other mammals, particularly in lactating humans. Thus, based on basic comparative physiology considerations, we suggest that concurrent lactation and pregnancy should be considered as an independent risk factor for breast cancer

An evaluation of casein hydrolyzate in combination with antibiotic for bacterial cure and subsequent increase in milk yield in dairy cows

<p>Abstract</p> <p>Background</p> <p>A 3-yr study examined whether prepartum treatment with casein hydrolyzate in combination with antibiotic, as routinely used in Israel for dry cow therapy, improved bacterial cure and increased milk yield in subsequent lactations in comparison with treatment with antibiotic alone. The vast majority of bacterial isolates in samples collected prior to drying-off comprised coagulase-negative staphylococci, mostly as <it>Staph. chromogenes</it>.</p> <p>Results</p> <p>Bacterial cure associated with the combined treatment was 73.8% in cows, significantly higher than the 51.7% cure recorded when cows were treated only with antibiotic. During the study, the annual milk yield of non-casein hydrolyzate treated and treated control cows increased at ~2% per year, which is consistent with the national annual increase attributed to genetic selection. In cows treated with casein hydrolyzate the increase was 9% (above the 2% expected) in the first lactation after the treatment, and 6.3% (above the 4% expected for 2 years) in the second lactation after treatment. These increases were significantly higher than those in the controls and those expected through genetic improvement.</p> <p>Conclusions</p> <p>Treatment with casein hydrolyzate at dry-off was shown to be a viable mean to eliminate existing environmental bacterial infection, and to improve milk yield in the next lactation.</p

Acute heat stress brings down milk secretion in dairy cows by up-regulating the activity of the milk-borne negative feedback regulatory system

<p>Abstract</p> <p>Background</p> <p>The objective of this study was to determine if acute heat stress (HS) decreases milk secretion by activating the milk-borne negative feedback system, as an emergency physiological response to prevent a life-threatening situation. To induce HS, summer acclimatized dairy cows were exposed to full sun under mid-summer Mediterranean conditions, with and without conventional cooling procedures.</p> <p>Results</p> <p>Exposure to HS induced a rapid and acute (within 24 h) reduction in milk yield in proportion to the heat load. This decrease was moderated by cooler night-time ambient temperature. The reduction in milk yield was associated with corresponding responses in plasminogen activator/plasminogen-plasmin activities, and with increased activity (concentration) of the (1–28) N-terminal fragment peptide that is released by plasmin from β-casein (β-CN (1–28)). These metabolites constitute the regulatory negative feedback system. Previously, it has been shown that β-CN (1–28) down-regulated milk secretion by blocking potassium channels on the apical aspects of the mammary epithelial cells.</p> <p>Conclusion</p> <p>Here we demonstrate that the potassium channels in mammary tissue became more susceptible to β-CN (1–28) activity under HS. Thus, the present study highlighted two previously unreported features of this regulatory system: (i) that it modulates rapidly in response to stressor impact variations; and (ii) that the regulations of the mammary epithelial potassium channel sensitivity to the inhibitory effect of β-CN (1–28) is part of the regulatory system.</p

Milk yield estimation during suckling using the double oxytocin injection-milking and the double weighing-suckling methods in dairy goats

The aim was to verify the validity of the double oxytocin-milking (DOT) method as milk yield estimator during the suckling period of lactating dairy goats. To this end, it was necessary to determine whether the weighing suckling weighing (WSW) and DOT methods of milk yield estimation satisfied the criteria to be considered valuable, the accuracy between both methods and the suitability of DOT to evaluate actual milk. At parturition, sixty lactating Murciano Granadina breed goats were separated into 2 groups, in mixed (MS; n = 24) and artificial rearing (ARS; n = 36) management systems. Until the sixth week of lactation (weaning), MS goats suckled one kid while kids from ARS goats were artificially reared; moreover, goats in both systems were submitted to once-a-day milking. Once per week, actual milk yield for ARS goats and potential milk yield were recorded using DOT method for all goats, except for 12 goats in ARS which remained as a control. Twelve goats from each management system were used to evaluate diurnal variation in milk production (DVM) by DOT method for 6 consecutive days in week 4 of lactation. No difference in DVM was found by DOT method in 4-h milk production of goats in MS (P = 0.099) or ARS (P = 0.220), which allowed sixfold multiplication of milked milk volume to obtain potential milk per day. ARS goats subjected to a weekly DOT and control group goats showed a similar (P = 0.379) lactation curve for the first 6 weeks of lactation. The DOT method slightly overestimated (3.4%, P = 0.005) the milk yield evaluated by WSW method for goats under an MS, but fitted the actual milk obtained by common milk records for the group of goats in an ARS submitted to the DVM test (P = 0.357) and the group in ARS alone (P = 0.163). The DOT method applied for 8 consecutive days led to a drop of 6 12% in milk yield during the following week for both production systems. In conclusion, DOT was an accurate method to estimate milk yield during the first weeks of lactation both in MS and ARS under the conditions of this experiment. © 2013 Elsevier B.V. All rights reserved.Fernández Martínez, N.; Balasch Parisi, S.; Pérez Baena, I.; Rodríguez Garcia, M.; Peris Ribera, CJ. (2013). Milk yield estimation during suckling using the double oxytocin injection-milking and the double weighing-suckling methods in dairy goats. Small Ruminant Research. 112(1-3):181-185. doi:10.1016/j.smallrumres.2012.12.023S1811851121-

The effects of tannin-containing ground pine bark diet upon nutrient digestion, nitrogen balance, and mineral retention in meat goats

Background Pine bark is a rich source of phytochemical compounds including tannins, phenolic acids, anthocyanins, and fatty acids. These phytochemicals have potential to significantly impact on animal health and animal production. The goal of this work is to measure the effects of tannins in ground pine bark as a partial feed replacement on feed intake, dietary apparent digestibility, nitrogen balance, and mineral retention in meat goats. Results Eighteen Kiko cross goats (initial BW = 31.8 ± 1.49 kg) were randomly assigned to three treatment groups (n = 6). Dietary treatments were tested: control (0 % pine bark powder (PB) and 30 % wheat straw (WS)); 15 % PB and 15 % WS, and 30 % PB and 0 % WS. Although dry matter (DM) intake and digestibility were not affected (P > 0.10) by feeding PB, neutral detergent fiber (linear; P = 0.01), acid detergent fiber (linear; P = 0.001) and lignin digestibility (linear; P = 0.01) decreased, and crude protein (CP) digestibility tended to decrease (P = 0.09) as PB increased in the diet, apparent retention of Ca (P = 0.09), P (P = 0.03), Mg (P = 0.01), Mn (P = 0.01), Zn (P = 0.01) and Fe (P = 0.09) also increased linearly. Nitrogen intake and fecal N excretion were not affected (P > 0.05) by addition of PB in the diet, but N balance in the body was quadratically increased (P < 0.01) in the 15 % PB diet compared to other diets. This may be due to more rumen escape protein and less excreted N in the urine with the 15 % PB diet. The study showed that a moderate level of tannin-containing pine bark supplementation could improve gastrointestinal nitrogen balance with the aim of improving animal performance. Conclusion These results suggest that tannin-containing PB has negative impact on fiber, lignin, and protein digestibility, but positively impacted on N-balance

2 Contribution Number 1328-E from the Agricultural Research Organization, The Volcani Center

ABSTRACT We studied the balance of Na + , K + , Cl -, and water in six high yielding (&gt;39 kg/d of milk) cows between wk 2 to 1 prepartum and at 2 and 7 wk postpartum during winter in Israel. Cows were fed complete diets; Na + and Cl -contents exceeded dietary recommendations, and K + content was equal to dietary recommendations. Milk yield was related positively and significantly to retention of Cl -and K + , indicating that ions that are the main constituents of sweat can limit the ability of cows to express full genetic potential. The highest ion retention was recorded for cows that had the highest dry matter intake and, hence, the highest ion intake. Retention of Cl -was highest for cows that were most efficient in retaining Cl -in the kidney. In hot climates, increasing the concentrations of ions in the diet of early lactation cows according to the actual dry matter intake could prevent or reduce the severity of ion deficiencies. Water turnover rate of the cows was dependent on dry matter intake, milk yield, and respiratory-cutaneous water loss. The milk-free water balance (water turnover rate minus water secreted in milk) could be very efficiently predicted for lactating and nonlactating cows by the following equation: milk-free water balance (kilograms per day) = digestible energy intake (megacalories per day) × 0.58 + respiratory-cutaneous loss (kilograms per day) × 0.97 ( n = 18; R 2 = 0.97). This formula provides a tool to assess the evaporative-cutaneous water loss from feed and water intake measurements to evaluate the severity of heat stress. ( Key words: water, ions, metabolism, lactation) Abbreviation key: FWI = free water intake, MFWB = milk-free water balance, RCW = respiratorycutaneous water, WTO = water turnover