Role of suckling in regulating cell turnover and onset and maintenance of lactation in individual mammary glands of sows1

Abstract

This study addressed the mechanisms by which suckling regulates cell turnover and onset and maintenance of lactation of individual mammary glands of sows. The effects of no, transient (through 12 to 14 h postpartum), or regular suckling of individual glands during d 0 to 6 of lactation were studied in 5 sows. Nonsuckling was obtained by taping the glands to prevent access to the nipples. Visual scores confirmed that regularly suckled glands maintained lactation, whereas transiently suckled and nonsuckled glands regressed during lactation. Mammary gland biopsies were collected on d -5, 1, 2, 4, and 6 relative to farrowing in order to evaluate the cell turnover and to quantify the transcription of genes potentially involved in mammary cell turnover and function. The proportion of proliferating cells was greatest prepartum (13.1%). After farrowing, the proportion of proliferating cells declined in all glands, then remained low (5.6%) in nonsuckled glands and increased (P < 0.01) from an average of 7.5% on d 1 to 9.9% on d 6 in regularly suckled and transiently suckled glands. Transcriptional data were analyzed using a gamma-distributed, generalized linear mixed model. Abundance of alpha-lactalbumin mRNA (P < 0.01) increased in regularly suckled glands within the first day of lactation and remained elevated, whereas the expression in taped glands remained at the prepartum level. Prolactin receptor mRNA abundance decreased (P < 0.001), and IGFBP-5 mRNA abundance increased (P < 0.01) in nonsuckled and transiently suckled glands after parturition compared with regularly suckled glands. Mammary mRNA abundances of IGF-I, IGF-II, type I IGF receptor, and caspase 3 were minimally or inconclusively affected by the suckling regimens. In conclusion, suckling during the first 12 to 14 h postpartum is insufficient to initiate and maintain lactation until 24 to 36 h postpartum but sufficient to induce mammary cell proliferation for at least 6 d postpartum. Furthermore, a high prolactin receptor transcription and a low IGFBP-5 transcription seem important for maintaining a functional mammary gland during lactation.

Neonatal piglet survival: impact of sow nutrition around parturition on fetal glycogen deposition and production and composition of colostrum and transient milk

“…This was illustrated in an experiment where suckling was prevented in selected mammary glands by taping the nipples for 6 days, beginning either 12 or 24 h after onset of parturition. Suckling is an important signal to stimulate mammary expression of prolactin receptors and α-lactalbumin and to maintain mammary function (Theil et al, 2006). As mentioned previously, it seems that low amounts of colostrum are available from the udder from 16 until 34 h after birth of the first piglet (Figure 3).…”

Efecto de la adición de nopal (Opuntia ficus-indica) a la dieta de cerdas lactantes sobre la producción y calidad de la leche

“…Con et al, 2010, 3154). Por lo cual, el descenso de la producción láctea coincide con el inicio del consumo de alimento sólido por parte de los lechones (Hurley et al, 2003, 80;Theil et al, 2006Theil et al, , 1697. Sin embargo, Farmer y Quesnel (2009, 59) y Devillers et al (2011Devillers et al ( , 1605, determinaron que el cambio de la alimentación de la cerda, en la fase de lactación, puede afectar no sólo la producción de leche, sino también la calidad láctea.…”

Suckling effects in sows: importance for mammary development and productivity

“…In a later trial, Theil et al (2006) showed the importance of suckling intensity for mammary regression. They compared no suckling, transient suckling (until 12 to 14 h postpartum) or regular suckling of mammary glands and reported that, based on visual scoring, regularly suckled glands maintained lactation whereas transiently suckled and non-suckled glands regressed during lactation.…”

“…One main factor having an impact on both mammary development and mammary involution is suckling of mammary glands by piglets. Suckling of a mammary gland in one lactation increases milk production in that gland during the next lactation (Farmer et al, 2012) and suckling is crucial for the prevention of involution in lactation (Theil et al, 2006). This review will briefly describe mammary gland development in swine, including involution, and then focus on the effect of suckling on involution and future mammary gland development and milk production.…”