Achieving Body Weight Adjustments for Feeding Status and Pregnant or Non-Pregnant Condition in Beef Cows

Abstract

BackgroundBeef cows herd accounts for 70% of the total energy used in the beef production system. However, there are still limited studies regarding improvement of production efficiency in this category, mainly in developing countries and in tropical areas. One of the limiting factors is the difficulty to obtain reliable estimates of weight variation in mature cows. This occurs due to the interaction of weight of maternal tissues with specific physiological stages such as pregnancy. Moreover, variation in gastrointestinal contents due to feeding status in ruminant animals is a major source of error in body weight measurements.ObjectivesDevelop approaches to estimate the individual proportion of weight from maternal tissues and from gestation in pregnant cows, adjusting for feeding status and stage of gestation.Methods and FindingsDataset of 49 multiparous non-lactating Nellore cows (32 pregnant and 17 non-pregnant) were used. To establish the relationships between the body weight, depending on the feeding status of pregnant and non-pregnant cows as a function of days of pregnancy, a set of general equations was tested, based on theoretical suppositions. We proposed the concept of pregnant compound (PREG), which represents the weight that is genuinely related to pregnancy. The PREG includes the gravid uterus minus the non-pregnant uterus plus the accretion in udder related to pregnancy. There was no accretion in udder weight up to 238 days of pregnancy. By subtracting the PREG from live weight of a pregnant cow, we obtained estimates of the weight of only maternal tissues in pregnant cows. Non-linear functions were adjusted to estimate the relationship between fasted, non-fasted and empty body weight, for pregnant and non-pregnant cows.ConclusionsOur results allow for estimating the actual live weight of pregnant cows and their body constituents, and subsequent comparison as a function of days of gestation and feeding status.

Nutrient Requirements of Zebu and Crossbred Cattle - BR-CORTE

“…The concept of pregnant compound was adopted (PREG) to estimate the energy and protein accumulation rate related to pregnancy or to the maternal tissues, presented by Gionbelli et al (2015a) and discussed in Chapter 1. The PREG represents the true quantities of components that grow directly related to pregnancy.…”

“…The estimates for the nutritional requirements for pregnant and non-pregnant Zebu cows discussed next are derived from recently published studies (Gionbelli, 2013;Gionbelli et al, 2013;Gionbelli et al, 2014;Gionbelli et al, 2015a;Gionbelli et al, 2015b).…”

“…The experiment used as base to estimate the metabolizable requirement for Zebu cows (Gionbelli et al, 2015a) ) can reach up to 50% in late pregnancy in beef cattle Ferrell et al 1976c;BCNRM, 2016), such an increase has not been directly considered in comparative slaughter experiments carried out on pregnant cows (Ferrell et al 1976c;Gionbelli et al 2015b). In these cases, the additional energy spent on maintenance relative to pregnancy is quantified in the calculation of the nutritional requirements for pregnancy.…”

“…To estimate the quantities of energy and protein retained in constituents related to pregnancy, the compound pregnancy or pregnant compound concept (PREG) was adopted. The PREG concept was presented by Gionbelli et al (2015a) and also described in Chapter 1 of the BR-CORTE. Based on the PREG, the quantities of energy and protein used to calculate the net requirements for pregnancy are those truly related to the pregnancy, which include: the gravid uterus minus the non-pregnant uterus (estimated) and the addition of the udder relative to the pregnancy.…”

Intestinal development of bovine foetuses during gestation is affected by foetal sex and maternal nutrition

“…Both groups received the same experimental diet, but differed in feed intake level. Restricted feeding level (CO) was planned for the gestation maintenance with a minimal body tissue gain (Gionbelli et al., ), whereas the ad libitum feeding treatment (ON) was planned to allow a body reserve deposition.…”