[Lactation Success 哺乳母豬成功飼養(yǎng)的關(guān)鍵]

11 September 2014

A review of recent research on mammary gland development in the sow and gilt was presented by Chantal Farmer of Agriculture and Agri-Food Canada's Dairy and Swine R&D Centre at the London Swine Conference 2014.

Abstract

摘要

Lactation success is key to the profitability of a farrowing unit and producers are now faced with an increased challenge because of the current use of hyperprolific sow lines.Numerous factors come into play to affect lactation success and one major aspect which has been overlooked in the past is mammary development.The current overview will succinctly cover various factors that can affect sow milk yield and will then focus on mammary development, namely, when it happens, how it happens and what can be done to stimulate it.Lastly, results from a project looking at the importance of teat use in first lactation for its milk yield in second lactation will be presented.

隨著高產(chǎn)母豬飼養(yǎng)的普及，如今豬場面臨越來越大的挑戰(zhàn)，而哺乳母豬的成功飼養(yǎng)是提高胎產(chǎn)小豬效益的關(guān)鍵。影響哺乳母豬飼養(yǎng)的因素眾多，過去一直被忽視的其中一個重要方面就是母豬乳腺的發(fā)育。項目測試結(jié)果顯示，第一胎次哺乳期母豬乳腺的發(fā)育及產(chǎn)奶情況將對下一胎次哺乳造成相應(yīng)的影響。下文將概述影響母豬乳腺發(fā)育和產(chǎn)奶量的因素及管理方案。

Sow Milk Yield

母豬的產(chǎn)奶量

Sow milk yield is the main determinant of piglet growth rate as it is the only source of energy for suckling piglets.Sows do not produce enough milk to sustain optimal growth of their litter and this problem was made worst with the current use of hyperprolific sow lines.Milk yield is influenced by numerous factors such as litter size, parity, nutrition, genetics, management, environment and endocrine status. Yet, one important factor that is often overlooked is mammary development. Indeed, sow milk yield is dependent on the number of milk-producing cells that are present in mammary glands at the onset of lactation.There is a positive correlation between the number of mammary cells and piglet growth rate. Periods with relatively high mammary growth are of particular interest since it is during those periods that mammary growth may be susceptible to being stimulated by nutritional or hormonal manipulations.

母乳是未斷奶仔豬的唯一能量來源，母豬的產(chǎn)奶量決定了哺乳期仔豬的生長速度。目前，高產(chǎn)母豬普遍面臨的一個嚴(yán)重問題是無法分泌足夠的奶水來滿足仔豬發(fā)揮最優(yōu)生長潛力的需要。影響母豬產(chǎn)奶的因素眾多，如產(chǎn)仔數(shù)（仔豬的大小）、胎次、營養(yǎng)、遺傳、管理、環(huán)境和內(nèi)分泌狀態(tài)等。然而，母豬乳腺的發(fā)育情況卻常常被忽視。事實上，母豬的產(chǎn)奶量取決于乳腺中泌乳細(xì)胞的數(shù)量。乳腺細(xì)胞和小豬生長速率之間呈正相關(guān)關(guān)系。乳腺快速增長的時期容易受到營養(yǎng)和激素刺激的影響。

Mammary Development in Swine: Hormonal Control

母豬的乳腺發(fā)育：激素控制

Mammary development in swine occurs at three developmental stages: from three months of age until puberty, during the last third of pregnancy, and during lactation.It is controlled by a complex interaction of various hormones. During gestation, oestrogens and prolactin are essential for mammary development and relaxin is also needed to stimulate total mammary gland growth.Few studies have looked at the effect of providing hormones on mammary development. Gilts receiving injections of porcine prolactin for a period of 28 days, as of 75kg bodyweight, increased their mammary development (based on visual appraisal) and also had lacteal secretions already present (McLaughlin et al., 1997).Interestingly, the degree of mammary gland development did not appear to be related to the dose of prolactin injected.A further study where gilts were slaughtered and mammary development actually measured, confirmed that injections of porcine prolactin to gilts for a period of 29 days, starting at 75kg bodyweight, stimulate mammary development at puberty (Farmer et al., 2005). Yet, the impact of such a treatment on subsequent milk yield is not known. Furthermore, porcine prolactin is not currently available commercially.

母豬的乳腺發(fā)育主要發(fā)生在三個時期：從三月齡到配種前期、妊娠期的后三分一階段和哺乳期間。這是復(fù)雜的由各種激素相互作用產(chǎn)生的結(jié)果。在妊娠期分泌的雌激素、催乳素和恥骨松弛激素等可有效刺激乳腺的增長。關(guān)于激素對乳房發(fā)育影響的相關(guān)研究很少。

McLaughlin等，在1997研究發(fā)現(xiàn)，給75公斤體重的母豬連續(xù)28天注射催乳素，能促進母豬乳腺的發(fā)育（基于視覺評價），并且（在母豬乳房中）已經(jīng)存在乳狀分泌物(McLaughlin et al., 1997)。有意思的是，乳腺的發(fā)育程度似乎并未與催乳素的劑量有關(guān)。

Farmer 等，于2005做了進一步的研究，將試驗?zāi)肛i屠宰并進行乳腺發(fā)育的實質(zhì)測量，證實從75公斤體重開始給母豬連續(xù)29天注射催乳素，能刺激青春期乳腺的發(fā)育。然而，這種操作方案對后續(xù)母豬泌乳可能造成的影響尚不明確。此外，豬用催乳素目前并沒有開始商業(yè)化。

Can Pre-pubertal Nutrition Affect Mammary Development?

青春期前的營養(yǎng)會影響乳腺的發(fā)育嗎？

Nutrition does influence mammary development in growing gilts, yet, data on thesubject is sparse (see review by Farmer, 2013).

Either a 20 per cent or a 26 per cent feed restriction from 90 days of age until puberty drastically reduces mammary tissue mass (Table 1).

營養(yǎng)會影響生長期母豬的乳腺發(fā)育，但是相關(guān)研究數(shù)據(jù)卻很少。(see review by Farmer, 2013)

從90日齡開始至青春期，對小母豬進行20%或26%的限飼，將大大降低乳腺組織的質(zhì)量（表1）。

On the other hand, earlier feed restriction, from 28 to 90 days of age, did not affect mammary development at puberty (Table 1).

Furthermore, lowering protein intake (14.4 versus 18.7 per cent crude protein) during the period from 90 days of age until puberty does not hinder mammary development of gilts (Table 1).

Composition of diets fed to prepubertal gilts influences their mammary development.Phytoestrogens are naturally-occurring plant compounds that can have oestrogenic properties. They are present in large amounts in soya and one class of these phytoestrogens comprises the molecule genistein. Gilts fed 2.3g per day of genistein from three months of age until puberty had a 44 per cent increase in the number of mammary cells at 183 days.

On the other hand, dietary supplementation with flax as seed, meal or oil during prepuberty brought about the expected changes in circulating fatty acids without any alteration in mammary development. Yet, when 10 per cent flaxseed was supplemented from day 63 of gestation until weaning, beneficial effects (30.9 per cent increase in parenchymal mass and 11.6 per cent increase in number of parenchymal cells) were noted in the mammary tissue of the female offspring of these sows at puberty.This was the first demonstration of such an in-utero effect and it opens new avenues in terms of potential management schemes to stimulate mammary development of gilts.

一方面，在28-90日齡間控料，對母豬乳腺發(fā)育影響不明顯。（表1）

此外，在90-202日齡降低粗蛋白攝入量(14.4 vs. 18.7%)，對母豬乳房發(fā)育的影響也不明顯。

日糧的組成成分對青春前期母豬乳腺發(fā)育有一定的影響。植物雌激素是自然產(chǎn)生的化合物，具有雌激素的特性。他們大量存在于大豆和由植物激素類組成的染料木黃桐中。小母豬從三月齡開始至青春期每天飼喂2.3g染料木黃桐，在183天中母豬乳腺細(xì)胞數(shù)量增加了44%。

另一方面，在母豬青春前期階段日糧中添加亞麻種子、油等，帶來可預(yù)見的脂肪酸循環(huán)變化，而對乳腺的發(fā)育沒有影響。但是，在母豬妊娠63天直至斷奶每天補充10%的亞麻籽，能給這些母豬所產(chǎn)的小母豬乳腺發(fā)育帶來有利的影響（乳腺實質(zhì)質(zhì)量增長30.9%和實質(zhì)細(xì)胞數(shù)量增加11.6%）。這是第一個關(guān)于在子宮內(nèi)影響（乳腺發(fā)育）的示例，將為刺激小母豬乳腺發(fā)育打開新的管理途徑。

Nutrition in Late Gestation and Lactation: Effects on Mammary Development

妊娠后期和哺乳期營養(yǎng)對乳腺發(fā)育的影響

Effects of late gestation and lactation feeding on mammary development in swine were recently reviewed by Farmer (2013).During gestation, feeding very high energy levels (44 versus. 24MJ ME per day) may have detrimental effects on mammary development and subsequent milk production whereas increasing the amount of dietary protein (16 versus 4g lysine per day) did not affect mammary development but may increase subsequent milk production.

When manipulating body composition of gilts by changing their protein and energy intakes during pregnancy, overly fat gilts (36mm backfat at the end of gestation) on a high-energy–low-protein diet had reduced mammary development (Head et al., 1991) and produced less milk than leaner gilts (25mm backfat) at the same bodyweight (Head and Williams, 1991). However, backfat of gilts in that study was much thicker than what is normally seen and the ideal body condition required to ensure maximal mammary development in late gestation should be investigated further.

Feeding in lactation also affects mammary development; an increase in weight of functional mammary glands is seen when sows are fed either more protein (65 versus 32g of lysine per day) or more energy (17.5 versus 12Mcal ME per day; Kim et al., 1999).It is, therefore, imperative to maximise sow feed intake during lactation.

Farmer (2013)對關(guān)于妊娠后期和哺乳期母豬采食對乳腺發(fā)育的影響進行了綜述。妊娠期間，飼喂高能飼料（44與24MJ ME/天）將會對乳腺的發(fā)育及哺乳期的產(chǎn)奶量產(chǎn)生不利的影響。而增加蛋白質(zhì)的量（16與4g賴氨酸/天）對乳腺的發(fā)育不產(chǎn)生影響，但可能會增加哺乳期的產(chǎn)奶量。

當(dāng)通過改變?nèi)焉锲诘鞍准澳芰康臄z入來調(diào)控母豬的體況，飼喂高能量低蛋白日糧的母豬過肥（妊娠后期背膘厚達(dá)36毫米）及乳腺發(fā)育水平降低(Head 等, 1991) ，而且產(chǎn)奶量也低于同樣體重但較瘦（背膘厚25毫米）的母豬。然而，在這項研究試驗中的母豬背膘比實際生產(chǎn)中常見的要厚很多，需要做進一步的試驗來確定促進母豬乳腺發(fā)育所需的最佳體況。

哺乳期的飼養(yǎng)管理也會影響乳房的發(fā)育，當(dāng)哺乳母豬飼喂更高蛋白（65與32g賴氨酸/天）或更高能量（17.5與12Mcal ME/天；Kim 等, 1999）日糧時，可見功能性乳腺的重量增加。因此，必須讓哺乳母豬的采食量最大化。

Involution of Mammary Glands

乳腺的退化

Mammary involution at weaning is an essential process of the mammary gland and much remains to be learned about it in swine.It is associated with dramatic changes occurring rapidly in the seven to 10 days following weaning, with a loss of more than two-thirds of the weight of mammary glands (Ford et al., 2003).

Mammary gland involution also takes place in early lactation when a gland is not being suckled. It occurs rapidly during the first seven to 10 days after farrowing and was irreversible after three days of non-suckling.

On the other hand, involution is reversible after 24 hours of non-suckling but the 'rescued' gland will never produce as much milk as if used right from the onset of lactation (see review by Farmer 2013).

乳腺退化是斷奶過程中不可避免的一個現(xiàn)象，在豬方面的相關(guān)研究仍比較缺乏。這是發(fā)生在斷奶后7到10天的一個急劇變化，乳腺重量下降超過三分之二（Ford 等, 2003）。

乳腺退化也發(fā)生在哺乳早期母豬不喂奶，在分娩7-10天后停止哺乳3天則不可逆轉(zhuǎn)地發(fā)生乳腺退化。另一方面，停止哺乳24小時后發(fā)生的乳腺退化是可逆的，但是“獲救”的乳腺產(chǎn)奶量將會打折扣。

Does Teat Use in First Lactation Affect Its Milk Yield in Second Lactation?

第一胎次哺乳母豬的乳房使用程度對第二胎次的產(chǎn)奶量有影響嗎？

With today's hyperprolific sow lines, swine producers are faced with a problem in their farrowing rooms: should they “l(fā)oad” the primiparous sows with as many piglets as possible or should they leave some teats unused to give these sows a “respite”. This is particularly important in first parity sows with poor body condition, to avoid the “l(fā)ean sow syndrome” that potentially leads to reproductive problems.

New findings demonstrate for the first time that teats that are used in first lactation will produce more milk in the second lactation (Farmer et al., 2012). Indeed, piglets suckling teats which were previously used weighed 1.12 kg more on day 56 than piglets suckling a previously unused teat.Furthermore, development of a teat that was previously used is improved in the second lactation and piglets suckling teats which were not used previously show a greater level of hunger in second lactation.Interestingly, piglets seem to be able to differentiate between previously-used and -unused teats.

現(xiàn)今的高產(chǎn)母豬在產(chǎn)房正面臨著一個問題：初產(chǎn)母豬應(yīng)該盡可能多帶仔還是少帶仔以便讓母豬的部分乳房得到休息？為了避免因哺乳掉膘嚴(yán)重而影響下一胎次的繁殖，這對于體況較差的初產(chǎn)母豬來說是特別重要的一個問題。

新的研究發(fā)現(xiàn)，讓初產(chǎn)母豬在首個哺乳期所有乳頭都得到仔豬的充分吸允，會使下一胎次的產(chǎn)奶量得到提高(Farmer 等, 2012)。事實上，吸允以前經(jīng)過哺乳的乳房的小豬與吸允（前一胎次）未經(jīng)哺乳的乳房的小豬相比，在56日齡時的體重多1.12㎏。此外，第一胎次得到充分使用的乳房在第二胎次產(chǎn)奶量會更高，而且第二胎次的小豬吸允第一胎次未經(jīng)哺乳的乳房時饑餓感會比較強（吃不飽）。有趣的是，小豬似乎能夠區(qū)分以前曾哺乳和未曾哺乳的乳房。

Conclusions

總結(jié)

A combination of factors are involved in the control of sow milk yield and with the current use of hyperprolific sow lines it has become imperative to provide the best-adapted management and feeding strategies to improve upon it.

Nutrition of replacement gilts and of late-pregnant sows requires special attention to ensure maximal mammary development and future milk yield potential.

Management of first-litter sows can also impact subsequent lactation performances.

We now know that teats which were suckled in first lactation produce more milk and have a greater development in second lactation than teats which were not suckled in first lactation.

Such knowledge is critical for producers to make the best decision in terms of management strategies for their first-parity sows.

影響母豬產(chǎn)奶的因素眾多，當(dāng)務(wù)之急是尋找適用的飼養(yǎng)管理方案來改善高產(chǎn)母豬的哺乳問題。

后備母豬和妊娠后期母豬的營養(yǎng)設(shè)定特別要注意以確保母豬乳腺的發(fā)育和促進產(chǎn)奶潛力的發(fā)揮為前提。

初產(chǎn)母豬的飼養(yǎng)管理會對下一胎次的產(chǎn)奶造成影響。

我們現(xiàn)在知道，在第一胎次得到充分使用的乳房產(chǎn)奶量會更高，而且在第二胎次哺乳期時會比第一胎次未經(jīng)哺乳的乳房發(fā)育得更好。

這些知識可以為生產(chǎn)者做好母豬的飼養(yǎng)管理決策方案提供重要的參考。

Literature Cited文獻引用

· Farmer, C. 2013. Review: Mammary development in swine: effects of hormonal status, nutrition and management. Can. J. Anim. Sci. 93:1-7.

· Farmer, C. and M.F. Palin. 2005 Exogenous prolactin stimulates mammary development and alters expression of prolactin-related genes in prepubertal gilts. J. Anim. Sci. 83:825-832.

· Farmer, C., M.F. Palin, P.K. Theil, M.T. Sorensen and N. Devillers, N. 2012 Milk production in sows from a teat in second parity is influenced by whether it was suckled in first parity. J. Anim. Sci. 90:3743-3751.

· Farmer, C., D. Petitclerc, M.T. Sorensen, M. Vignola and J.Y. Dourmad. 2004. Impacts of dietary protein level and feed restriction during prepuberty on mammogenesis in gilts. J. Anim. Sci. 82:2343-2351.

· Ford, J.A. Jr., S.W. Kim, S.L. Rodriguez-Zas and W.L. Hurley. 2003 Quantification of mammary gland tissue size and composition changes after weaning in sows. J. Anim. Sci. 81:2583-2589.

· Head, R.H. and I.H. Williams. 1991. Mammogenesis is influenced by pregnancy nutrition. p. 33. Manipulating Pig Production III. Australasian Pig Science Association, Werribee, Australia.

· Head, R.H., N.W. Bruce and I.H. Williams. 1991. More cells lead to more milk. p. 76. Manipulating Pig Production III. Australasian Pig Science Association, Werribee, Australia.

· Kim, S.W., W.L. Hurley, I.K. Han, H.H. Stein and R.A. Easter. 1999. Effect of nutrient intake on mammary gland growth in lactating sows. J. Anim. Sci. 77:3304-3315.

· McLaughlin, C.L., J.C. Byatt, D.F. Curran, J.J. Veenhuizen, M.F. McGrath, F.C. Buonomo, R.L. Hintz and C.A. Baile. 1997 Growth performance, endocrine, and metabolite responses of finishing hogs to porcine prolactin. J. Anim. Sci. 75:959-967.

· Sorensen, M.T., C. Farmer, M. Vestergaard, S, Purup and K. Sejrsen. 2006. Mammary development in prepubertal gilts fed restrictively or ad libitum in two sub-periods between weaning and puberty. Livest. Sci. 99:249-255.

Reference

Farmer C. 2014. Lactation success. Proceedings of the London Swine Conference. London, Ontario, Canada. 26 to 27 March 2014. p23-26.

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