Differences during the first lactation between cows cloned by somatic cell nuclear transfer and noncloned cows

Abstract

Lactation performance is dependent on both the genetic characteristics and the environmental conditions surrounding lactating cows. However, individual variations can still be observed within a given breed under similar environmental conditions. The role of the environment between birth and lactation could be better appreciated in cloned cows, which are presumed to be genetically identical, but differences in lactation performance between cloned and noncloned cows first need to be clearly evaluated. Conflicting results have been described in the literature, so our aim was to clarify this situation. Nine cloned Prim' Holstein cows were produced by the transfer of nuclei from a single fibroblast cell line after cell fusion with enucleated oocytes. The cloned cows and 9 noncloned counterparts were raised under similar conditions. Milk production and composition were recorded monthly from calving until 200d in milk. At 67d in milk, biopsies were sampled from the rear quarter of the udder, their mammary epithelial cell content was evaluated, and mammary cell renewal, RNA, and DNA were then analyzed in relevant samples. The results showed that milk production did not differ significantly between cloned and noncloned cows, but milk protein and fat contents were less variable in cloned cows. Furthermore, milk fat yield and contents were lower in cloned cows during early lactation. At around 67 DIM, milk fat and protein yields, as well as milk fat, protein, and lactose contents, were also lower in cloned cows. These lower yields could be linked to the higher apoptotic rate observed in cloned cows. Apoptosis is triggered by insulin-like factor growth binding protein 5 (IGFBP5) and plasminogen activator inhibitor (PAI), which both interact with CSN1S2. During our experiments, CSN1S2 transcript levels were lower in the mammary gland of cloned cows. The mammary cell apoptotic rate observed in cloned cows may have been related to the higher levels of DNA (cytosine-5-)-methyltransferase 1 (DNMT1) transcripts, coding for products that maintain the epigenetic status of cells. We conclude, therefore, that milk production in cloned cows differs slightly from that of noncloned cows. These differences may be due, in part, to a higher incidence of subclinical mastitis. They were associated with differences in cell apoptosis and linked to variations in DNMT1 mRNA. However, milk protein and fat contents were more similar among cloned cows than among noncloned cows.

Assessment of the Growth and Reproductive Performance of Cloned Pietrain Boars

“…Cloned Pietrain boars grew slower and exhibited smaller body size than the conventionally bred boars, suggesting that cloning manipulation might impair the growth performance of animals. Similarly, cloned cows have been found to exhibit a lower growth rate [35] and even reach puberty later than non-cloned cows [36]. However, these results were inconsistent with other previous studies, indicating that clones grow normally and have similar characteristics to those of non-clones [19][20][21].…”

“…Our study made a series of comparisons between the clones and age-matched non-clones. Such a comparison was also performed in previous studies to assess the applicability of cloned animals [12,21,[34][35][36][37][38]. We aim to investigate whether clones and their progeny keep behaving better than the "normal boars", which is important for the application of cloning to expand the elite genetic resources and improve the economic value of selection and production in the pig industry.…”

Genome‐wide comparison of DNA methylation patterns between yak and three cattle strains and their potential association with mRNA transcription

“…These results suggested that there might be complicated reasons underlying the hypomethylation of yak. In cattle, DNMT1 expression was reported to regulate lactation and milk production (Montazertorbati et al, 2016; J. Wang et al, 2014). How the lowered level of DNMT1 affects the mammary tissue functions in yak required further investigations.…”

Epigenetics: New Insights into Mammary Gland Biology

“…DNMT1 is expressed at a higher rate in cloned lactating cows than in non-cloned lactating cows. This is linked to a higher apoptotic rate and lower rate of αS2-casein transcription [59].…”