The human population is ever increasing while the quality and quantity of natural resources used for livestock production decline. This calls for improved product efficiency and the development of improved and sustainable cattle production methods to produce higher quality products to satisfy the demands of both the modern and transient world. The goal of this review was to summarize the interactions, challenges, and opportunities in cattle production relating to their endocrine system, and how reproductive hormones and others impact economically important traits, animal welfare, and human health. A comprehensive literature search was conducted with a focus on analysis of natural hormones and the use of exogenous hormone administration for reproduction, growth, and development of beef and dairy cattle. Hormones regulate homeostasis and enhance important traits in cattle, including fertility, growth and development, health, and the production of both meat and milk products. Reproductive hormones such as testosterone, estradiol, progesterone, and related synthetics like trenbolone acetate and zeranol can be strategically utilized in both beef and dairy cattle production systems to enhance their most valuable traits, but the impact of these substances must account for the welfare of the animal as well as the health of the consumer. This scientific review provides a comprehensive analysis of the bovine endocrine system’s impact on food animals and product quality which is vital for students, researchers, livestock producers, and consumers. Although important advances have been made in animal science and related technological fields, major gaps still exist in the knowledge base regarding the influence of hormones on the production and welfare of food animals as well as in the public perception of hormone use in food-producing animals. Filling these gaps through transformative and translational research will enhance both fundamental and applied animal science to feed a growing population.
The objectives of this study were to (1) evaluate the effect of rate of winter hair growth on Angus cow performance and (2) estimate the correlation between rate of winter growth and other physiological parameters. Data were collected on fall-calving Angus females (n = 127) approximately every 60 d from August to February from 2011 to 2019. Animals were observed by trained technicians for winter growth (WG) and length (WL) scores from 1 to 5. A 1 for winter growth indicated no winter growth and a 5 indicated a full winter coat. For winter length, a 1 indicated short hair and a 5 indicated long. At scoring, a 5.08 cm by 10.16 cm hair sample was clipped directly behind the left shoulder below the top line and weighed. A thermal image was taken to determine average surface temperature of both the shaved (SHAVE) and unshaved (UNSHAVED) areas. Month of first winter growth (MFWG) was determined when the female reached an average winter growth score of 2.5 or higher. Calf performance was considered a trait of the dam and included AdjBW and d205wt. Phenotypic correlations were estimated on SHAVE, UNSHAVED, WG, WL, MFWG, hair weight, and month of first shedding (MFS), which was assessed during the spring of each year. Data were analyzed using the MIXED procedure of SAS with AdjBW and d205wt as response variables. The model included fixed effects of calf sex and MFWG with sire as a random effect. SHAVE was weakly positively associated with WG, WL (P < 0.05). There was no association between MFWG and MFS. MFWG was significant for AdjBW and d205wt with females starting winter growth in October having lighter calves at birth and weaning compared to those in December. Results suggest an association between MFWG and performance traits in Angus dams.
The objective of this study was to evaluate winter hair coat shedding ability and the association to cow production performance. This work was a collaborative effort from the S-1064 multi-state research project. Data were collected on spring and fall-calving purebred and commercial Angus females with calves (n = 1192) from March until July from 2008 to 2018 in Mississippi, Arkansas and Texas. Dams were observed once monthly by two trained technicians for winter hair coat shedding and give a visual hair shedding score of 1 to 5 with 1 indicating 100% shed, 2 = 75% shed, 3 = 50% shed, 4 = 25% shed, and 5 indicating 0% shedding of the winter hair coat. Month of first shedding (MFS) was determined once a female reached an average hair shedding score of ≤ 3.5 for any given month. Calf birth and weaning weights were considered as performance of the dam. For cow performance, the response variables included AdjBW and d205wt of the calf. Data were analyzed using the MIXED procedure of SAS with significance declared at P ≤ 0.05. The model included MFS as a fixed effect with calf sex as a covariate and calf sire as a random effect. Females that obtained a shedding score of ≤ 3.5 by May had heavier calves at birth (P ≤ 0.01) when compared with those that shed in June and July, with July weights being the lightest. Females that scored ≤ 3.5 by May has significantly heavier d205wt (P ≤ 0.01) when compared to those that shed by June and July. When comparing locations, females in Arkansas shed later (P ≤ 0.01) when compared with both Mississippi and Texas, which were similar. Shedding ability could be an important economic trait to be considered in cow-calf operations.
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