Physiological and cellular requirements for successful elongation of the preimplantationconceptus and the implications for fertility in lactating dairy cows

Elongation of the preimplantation conceptus is a prerequisite for maternal recognition of pregnancy and implantation in ruminants. Failures in this phase of development likely contribute for the subfertility of lactating dairy cows. This review will discuss our current understanding of the physiological and cellular requirements for successful elongation of the preimplantation conceptus and their potential deficiency in subfertile lactating dairy cows. Major requirements include the priming of the endometrium by ovarian steroids, reprogramming of trophectoderm cells at the onset of elongation, and intensification of the crosstalk between elongating conceptus and endometrium. Conceptus elongation and survival in dairy cows does not seem to be affected by lactation per se but seem to be altered in subgroups of cows with endocrine, metabolic and nutritional imbalances or deficiencies. These subgroups of cows include those suffering diseases postpartum, anovular cows enrolled in synchronization programs, and cows with low concentration of circulating steroids and IGF1. Success of conceptus elongation starts long before breeding and entails optimization of health and nutrition programs, especially during the transition period, and might be extended to the supplementation of endocrine and nutritional shortages at the time of breeding. Genetic selection will eventually become more important as researchers unravel the molecular control of reproduction and develop new fertility traits focused on pregnancy survival.

Physiological and cellular requirements for successful elongation of the preimplantationconceptus and the implications for fertility in lactating dairy cows

Elongation of the preimplantation conceptus is a prerequisite for maternal recognition of pregnancy and implantation in ruminants. Failures in this phase of development likely contribute for the subfertility of lactating dairy cows. This review will discuss our current understanding of the physiological and cellular requirements for successful elongation of the preimplantation conceptus and their potential deficiency in subfertile lactating dairy cows. Major requirements include the priming of the endometrium by ovarian steroids, reprogramming of trophectoderm cells at the onset of elongation, and intensification of the crosstalk between elongating conceptus and endometrium. Conceptus elongation and survival in dairy cows does not seem to be affected by lactation per se but seem to be altered in subgroups of cows with endocrine, metabolic and nutritional imbalances or deficiencies. These subgroups of cows include those suffering diseases postpartum, anovular cows enrolled in synchronization programs, and cows with low concentration of circulating steroids and IGF1. Success of conceptus elongation starts long before breeding and entails optimization of health and nutrition programs, especially during the transition period, and might be extended to the supplementation of endocrine and nutritional shortages at the time of breeding. Genetic selection will eventually become more important as researchers unravel the molecular control of reproduction and develop new fertility traits focused on pregnancy survival.(AU)

Probability, odds and random chance: the difficult task of modulating the epigenetic profile of cloned embryos

Since the beginning of modern embryology, scientists have wondered about how a small number of totipotent embryonic cells can become an individual with a wide variety of organs and tissues with distinct functions. Also, the idea of generating a cloned animal using a nucleus from a donor cell is not recent. However, it has taken years of research to achieve this goal, especially regarding mechanisms of cell reprogramming required to return a differentiated cell to totipotency. Cloning by somatic cell nuclear transfer (SCNT) has been a valuable tool to understand epigenetic mechanisms related to cellular reprogramming. However, cloning efficiency is still low, with a low percentage of embryos resulting in healthy animals. The high attrition rate is associated with incomplete or abnormal epigenetic reprogramming, such that many cloned embryos have DNA methylation patterns different than controls, resulting in faulty gene expression and subsequent developmental failures. Attempts to improve genome reprogramming by modulation of oocyte quality and/or somatic cell plasticity, thereby increasing cloning efficiency and preventing detrimental effects on development, have proven ineffective. The recent development of DNA editing techniques may facilitate an improved understanding of cellular reprogramming and the role of DNA methylation in development. These novel tools may lead to new means to modulate epigenetic programming and inheritance, and hold great promise to assist in epigenetic remodeling of the donor nucleus. Such strategies are likely to improve the odds for successful cloning.

Probability, odds and random chance: the difficult task of modulating the epigenetic profile of cloned embryos

Since the beginning of modern embryology, scientists have wondered about how a small number of totipotent embryonic cells can become an individual with a wide variety of organs and tissues with distinct functions. Also, the idea of generating a cloned animal using a nucleus from a donor cell is not recent. However, it has taken years of research to achieve this goal, especially regarding mechanisms of cell reprogramming required to return a differentiated cell to totipotency. Cloning by somatic cell nuclear transfer (SCNT) has been a valuable tool to understand epigenetic mechanisms related to cellular reprogramming. However, cloning efficiency is still low, with a low percentage of embryos resulting in healthy animals. The high attrition rate is associated with incomplete or abnormal epigenetic reprogramming, such that many cloned embryos have DNA methylation patterns different than controls, resulting in faulty gene expression and subsequent developmental failures. Attempts to improve genome reprogramming by modulation of oocyte quality and/or somatic cell plasticity, thereby increasing cloning efficiency and preventing detrimental effects on development, have proven ineffective. The recent development of DNA editing techniques may facilitate an improved understanding of cellular reprogramming and the role of DNA methylation in development. These novel tools may lead to new means to modulate epigenetic programming and inheritance, and hold great promise to assist in epigenetic remodeling of the donor nucleus. Such strategies are likely to improve the odds for successful cloning.(AU)

Perfil genético das linhagens de touros leiteiros Holandês e Jersey disponíveis no Brasil / Genetic profile of Holstein and Jersey dairy bull lines available in Brazil

As raças de bovinos de leite Holandesa e Jersey estão entre as mais prevalentes no Brasil. Para avaliar as diferenças entre as PTAs (habilidades de transmissão preditas) destas raças e suas linhagens, foram coletadas informações de 385 touros Holandês e 82 touros Jersey disponibilizados por nove empresas comercializadoras de sêmen no Brasil. Três diferentes linhagens de cada raça foram encontradas. O método dos modelos lineares generalizados foi utilizado para a comparação entre linhagens e entre raças. As duas linhagens da raça Holandesa mais prevalentes apresentaram as maiores PTAs médias para produção de leite (1.061,04 libras e 975,32 libras) e as menores PTAs para a porcentagem de sólidos no leite (de -0,05% a -0,0003%)(AU)

The Holstein and Jersey dairy cattle breeds are among the most prevalent in Brazil. To evaluate differences among the PTAs (predicted transmitting abilities) of these breeds and their lines, data were collected on 385 Holstein bulls and 82 Jersey sires with semen commercially available from nine Brazilian companies. Three different sire lines for each breed were found. The general linear models method was used for the comparison among lines and between breeds. The two most prevalent lines of Holstein breed presented higher average PTAs for milk yield (1,061.04 pounds and 975.32 pounds) and lower PTAs for percentage of milk solids (from -0.05% to -0.0003%)(AU)

Genetic profile of Holstein and Jersey dairy bull lines available in Brazil

The Holstein and Jersey dairy cattle breeds are among the most prevalent in Brazil. To evaluate differences among the PTAs (predicted transmitting abilities) of these breeds and their lines, data were collected on 385 Holstein bulls and 82 Jersey sires with semen commercially available from nine Brazilian companies. Three different sire lines for each breed were found. The general linear models method was used for the comparison among lines and between breeds. The two most prevalent lines of Holstein breed presented higher average PTAs for milk yield (1,061.04 pounds and 975.32 pounds) and lower PTAs for percentage of milk solids (from -0.05% to -0.0003%) (P 0.05). These results indicate the supply of sires that mostly increase the milk yield in the Brazilian market. The Jersey breed presented a higher inbreeding coefficient (6.62%) than the Holstein breed (5.14%) (P 0.05). Although the Holstein breed presented higher PTAs for milk yield and lower PTAs for percentage of milk solids (P 0.05), the productive life of the Jersey breed (1.17 months) was longer than it was in the Holstein breed (0.40 months) (P 0.05). We identified the existence of an important variability of the available genetic profiles, what allows the Brazilian producers to choose the most adequate semen for their production system. It is necessary to consider the genetic profiles of sires' lines offered for artificial insemination in Brazil to understand and direct the genetic pattern of Brazilian dairy cattle.

As raças de bovinos de leite Holandesa e Jersey estão entre as mais prevalentes no Brasil. Para avaliar as diferenças entre as PTAs (habilidades de transmissão preditas) destas raças e suas linhagens, foram coletadas informações de 385 touros Holandês e 82 touros Jersey disponibilizados por nove empresas comercializadoras de sêmen no Brasil. Três diferentes linhagens de cada raça foram encontradas. O método dos modelos lineares generalizados foi utilizado para a comparação entre linhagens e entre raças. As duas linhagens da raça Holandesa mais prevalentes apresentaram as maiores PTAs médias para produção de leite (1.061,04 libras e 975,32 libras) e as menores PTAs para a porcentagem de sólidos no leite (de -0,05% a -0,0003%) (P 0.05). Estes resultados sugerem a oferta de touros no mercado nacional que são capazes principalmente de aumentar a produção de leite. A raça Jersey apresentou um coeficiente de endogamia mais elevado (6,62%) que o da raça Holandesa (5,14%) (P 0.05). Embora a raça Holandesa tenha apresentado maiores PTAs para produção de leite e as menores PTAs para a porcentagem de sólidos no leite, a vida produtiva da raça Jersey apresentou-se mais longa (1,17 meses) (P 0.05) que a da raça Holandesa (0,40 meses). Houve uma importante variabilidade do material genético disponível, permitindo a escolha do sêmen mais adequado para cada sistema de produção. Faz-se necessário conhecer o perfil genético dos touros disponibilizados para inseminação artificial no Brasil, com vistas ao conhecimento e direcionamento do padrão genético dos bovinos leiteiros no país.

Perfil genético das linhagens de touros leiteiros Holandês e Jersey disponíveis no Brasil / Genetic profile of Holstein and Jersey dairy bull lines available in Brazil

As raças de bovinos de leite Holandesa e Jersey estão entre as mais prevalentes no Brasil. Para avaliar as diferenças entre as PTAs (habilidades de transmissão preditas) destas raças e suas linhagens, foram coletadas informações de 385 touros Holandês e 82 touros Jersey disponibilizados por nove empresas comercializadoras de sêmen no Brasil. Três diferentes linhagens de cada raça foram encontradas. O método dos modelos lineares generalizados foi utilizado para a comparação entre linhagens e entre raças. As duas linhagens da raça Holandesa mais prevalentes apresentaram as maiores PTAs médias para produção de leite (1.061,04 libras e 975,32 libras) e as menores PTAs para a porcentagem de sólidos no leite (de -0,05% a -0,0003%)

The Holstein and Jersey dairy cattle breeds are among the most prevalent in Brazil. To evaluate differences among the PTAs (predicted transmitting abilities) of these breeds and their lines, data were collected on 385 Holstein bulls and 82 Jersey sires with semen commercially available from nine Brazilian companies. Three different sire lines for each breed were found. The general linear models method was used for the comparison among lines and between breeds. The two most prevalent lines of Holstein breed presented higher average PTAs for milk yield (1,061.04 pounds and 975.32 pounds) and lower PTAs for percentage of milk solids (from -0.05% to -0.0003%)

Persistência da lactação e composição do leite em ovelhas leiteiras das raças Lacaune e East Friesian

The objective of this study was to evaluate the lactation persistency and milk composition in East Friesian and Lacaune dairy ewes. Twenty one East Friesian and forty six Lacaune ewes on 44±7.2 days in milk (DIM) were used in a rotational system grazing paddocks of Panicum maximum jacq. cv. 'Aruana'. Milk yield (MY) was measured every four days throughout the experiment (92 days). Milk samples for composition analysis were collected on days 1, 25, 50, 75, and 92. The best fit prediction equations for MY were MY=1.42-0.02* DIM, r²;=0.20 for East Friesian; and MY=2.03-0.08* DIM, r²;=0.22 for Lacaune. At the beginning of the experimental period Lacaune MY was 30% higher. Lacaune ewes showed lower persistency and higher milk yield (1.67 vs. 1.35kg day-1, P 0.001), milk fat yield (114.80 vs. 102.85g day-1, P 0.001) and protein yield (82.82 vs. 73.10g day-1, P 0.001). East Friesian ewes had greater milk fat (7.31 vs. 6.86%, P 0.0008) and protein concentrations (5.18 vs. 4.93%, P 0.001). Overall, the East Friesian ewes showed more persistency than Lacaune, but the milk yield and milk yield composition was greater in Lacaune.

O objetivo deste estudo foi avaliar a persistência da lactação e a composição do leite em ovelhas leiteiras das raças East Friesian e Lacaune. Foram usadas 21 ovelhas East Friesian e 46 ovelhas Lacaune com 44±7,2 dias em lactação (DEL), mantidas em pastagem de Panicum maximum Jacq. cv. 'Aruana' em um sistema rotacionado. A produção de leite (PL) foi medida a cada quatro dias durante todo o período experimental (92 dias). Amostras de leite foram coletadas no 17°, 25°, 50°, 75° e 92° dia. As equações descrevendo a lactação foram diferentes (East Friesian: PL=1,42-0,02 * DEL, r²;=0,20; Lacaune: PL=2,03-0,08 * DEL, r²=0,22). Ao início do período experimental, a produção de leite das ovelhas Lacaune foi 30% superior. As ovelhas Lacaune apresentaram menor persistência, maiores produções de leite (1,67 vs. 1,35kg dia-1, P 0,001), de gordura (114,80 vs. 102,85g dia-1, P 0,001) e de proteína (82,82 vs. 73,10g dia-1, P 0,001). As ovelhas East Friesian apresentaram maiores teores de gordura (7,31 vs. 6,86%, P 0,0008) e proteína (5,18 vs. 4,93%, P 0,001). No geral, as ovelhas East Friesian mostraram maior persistência, mas a produção de leite e componentes do leite foram maiores para as ovelhas Lacaune.

Persistência da lactação e composição do leite em ovelhas leiteiras das raças Lacaune e East Friesian

The objective of this study was to evaluate the lactation persistency and milk composition in East Friesian and Lacaune dairy ewes. Twenty one East Friesian and forty six Lacaune ewes on 44±7.2 days in milk (DIM) were used in a rotational system grazing paddocks of Panicum maximum jacq. cv. 'Aruana'. Milk yield (MY) was measured every four days throughout the experiment (92 days). Milk samples for composition analysis were collected on days 1, 25, 50, 75, and 92. The best fit prediction equations for MY were MY=1.42-0.02* DIM, r²;=0.20 for East Friesian; and MY=2.03-0.08* DIM, r²;=0.22 for Lacaune. At the beginning of the experimental period Lacaune MY was 30% higher. Lacaune ewes showed lower persistency and higher milk yield (1.67 vs. 1.35kg day-1, P 0.001), milk fat yield (114.80 vs. 102.85g day-1, P 0.001) and protein yield (82.82 vs. 73.10g day-1, P 0.001). East Friesian ewes had greater milk fat (7.31 vs. 6.86%, P 0.0008) and protein concentrations (5.18 vs. 4.93%, P 0.001). Overall, the East Friesian ewes showed more persistency than Lacaune, but the milk yield and milk yield composition was greater in Lacaune.

O objetivo deste estudo foi avaliar a persistência da lactação e a composição do leite em ovelhas leiteiras das raças East Friesian e Lacaune. Foram usadas 21 ovelhas East Friesian e 46 ovelhas Lacaune com 44±7,2 dias em lactação (DEL), mantidas em pastagem de Panicum maximum Jacq. cv. 'Aruana' em um sistema rotacionado. A produção de leite (PL) foi medida a cada quatro dias durante todo o período experimental (92 dias). Amostras de leite foram coletadas no 17°, 25°, 50°, 75° e 92° dia. As equações descrevendo a lactação foram diferentes (East Friesian: PL=1,42-0,02 * DEL, r²;=0,20; Lacaune: PL=2,03-0,08 * DEL, r²=0,22). Ao início do período experimental, a produção de leite das ovelhas Lacaune foi 30% superior. As ovelhas Lacaune apresentaram menor persistência, maiores produções de leite (1,67 vs. 1,35kg dia-1, P 0,001), de gordura (114,80 vs. 102,85g dia-1, P 0,001) e de proteína (82,82 vs. 73,10g dia-1, P 0,001). As ovelhas East Friesian apresentaram maiores teores de gordura (7,31 vs. 6,86%, P 0,0008) e proteína (5,18 vs. 4,93%, P 0,001). No geral, as ovelhas East Friesian mostraram maior persistência, mas a produção de leite e componentes do leite foram maiores para as ovelhas Lacaune.

Diferentes ofertas de forragem e a produção de leite em vacas mestiças Holandês x Gir

The objective of this study was to evaluate different herbage allowances in stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis), on the herbage disappearance rate (HDR) and milk yield in crossbred Holstein x Gir cows. Thirty animals were assigned to three different herbage allowances (HA), ranging from 10.0, 12.5 and 15.0% BW. There was effect of HA on the HDR (P 0.001). Increasing the HA in one unit had effect on the HDR increasing by 140.0kg ha-1 day-1. There was effect of leaf:stem ratio on milk yield (P 0.05). The increasing in supplying herbage allowances did not resulted in increased milk yield because the management for herbage allowance and herbage growth.

Objetivou-se avaliar o efeito de diferentes ofertas de forragem em pastagem de estrela africana (Cynodon nlemfuensis Vanderyst var. nlemfuensis), sobre a taxa de desaparecimento de forragem (TDF) e a produção de leite de vacas mestiças Holandês x Gir. Trinta animais foram submetidos a três ofertas de forragem (OF) distintas, sendo 10,0 12,5 e 15,0% do peso corporal. Houve influência da OF sobre a TDF (P 0,001). Para cada unidade de acréscimo da OF, a TDF aumentou 140,0kg ha-1 dia-1. Houve efeito da relação folha:colmo sobre a produção de leite (P 0,05). O aumento da oferta não refletiu em incremento da produção de leite em função do manejo empregado para obtenção das ofertas e estádio de crescimento das plantas.

Diferentes ofertas de forragem e a produção de leite em vacas mestiças Holandês x Gir

The objective of this study was to evaluate different herbage allowances in stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis), on the herbage disappearance rate (HDR) and milk yield in crossbred Holstein x Gir cows. Thirty animals were assigned to three different herbage allowances (HA), ranging from 10.0, 12.5 and 15.0% BW. There was effect of HA on the HDR (P 0.001). Increasing the HA in one unit had effect on the HDR increasing by 140.0kg ha-1 day-1. There was effect of leaf:stem ratio on milk yield (P 0.05). The increasing in supplying herbage allowances did not resulted in increased milk yield because the management for herbage allowance and herbage growth.

Objetivou-se avaliar o efeito de diferentes ofertas de forragem em pastagem de estrela africana (Cynodon nlemfuensis Vanderyst var. nlemfuensis), sobre a taxa de desaparecimento de forragem (TDF) e a produção de leite de vacas mestiças Holandês x Gir. Trinta animais foram submetidos a três ofertas de forragem (OF) distintas, sendo 10,0 12,5 e 15,0% do peso corporal. Houve influência da OF sobre a TDF (P 0,001). Para cada unidade de acréscimo da OF, a TDF aumentou 140,0kg ha-1 dia-1. Houve efeito da relação folha:colmo sobre a produção de leite (P 0,05). O aumento da oferta não refletiu em incremento da produção de leite em função do manejo empregado para obtenção das ofertas e estádio de crescimento das plantas.

Diferentes ofertas de forragem e a produção de leite em vacas mestiças Holandês x Gir

The objective of this study was to evaluate different herbage allowances in stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis), on the herbage disappearance rate (HDR) and milk yield in crossbred Holstein x Gir cows. Thirty animals were assigned to three different herbage allowances (HA), ranging from 10.0, 12.5 and 15.0% BW. There was effect of HA on the HDR (P 0.001). Increasing the HA in one unit had effect on the HDR increasing by 140.0kg ha-1 day-1. There was effect of leaf:stem ratio on milk yield (P 0.05). The increasing in supplying herbage allowances did not resulted in increased milk yield because the management for herbage allowance and herbage growth.

Objetivou-se avaliar o efeito de diferentes ofertas de forragem em pastagem de estrela africana (Cynodon nlemfuensis Vanderyst var. nlemfuensis), sobre a taxa de desaparecimento de forragem (TDF) e a produção de leite de vacas mestiças Holandês x Gir. Trinta animais foram submetidos a três ofertas de forragem (OF) distintas, sendo 10,0 12,5 e 15,0% do peso corporal. Houve influência da OF sobre a TDF (P 0,001). Para cada unidade de acréscimo da OF, a TDF aumentou 140,0kg ha-1 dia-1. Houve efeito da relação folha:colmo sobre a produção de leite (P 0,05). O aumento da oferta não refletiu em incremento da produção de leite em função do manejo empregado para obtenção das ofertas e estádio de crescimento das plantas.