Body condition scoring of sheep was first developed as a technique in the 1960s. Unlike live weight, it circumvents the issues of skeletal size, breed and physiological state and is not influenced by gut fill or the length and wetness of the fleece. This review outlines the use of the technique and the relationships between body condition score and other physical measures. In addition, it summarises the literature, across a range of breeds and environments, on the effects of body condition score on reproductive and lactational performance, and the growth and survival of the offspring to weaning. We have proposed that while the relationship between body condition and production traits is positive, it is unlikely to be linear. Where appropriate, the review outlines areas that would benefit from further research. Finally, it outlines what a suitable body condition score profile might be for a ewe over the entire breeding cycle.

Management, nutrition, production, and genetics are the main reasons for the decline in fertility in the modern dairy cow. Selection for the single trait of milk production with little consideration for traits associated with reproduction in the modern dairy cow has produced an antagonistic relationship between milk yield and reproductive performance. The outcome is a multi-factorial syndrome of subfertility during lactation; thus, to achieve a better understanding and derive a solution, it is necessary to integrate a range of disciplines, including genetics, nutrition, immunology, molecular biology, endocrinology, metabolic and reproductive physiology, and animal welfare. The common theme underlying the process is a link between nutritional and metabolic inputs that support complex interactions between the gonadotropic and somatotropic axes. Multiple hormonal and metabolic signals from the liver, pancreas, muscle, and adipose tissues act on brain centers regulating feed intake, energy balance, and metabolism. Among these signals, glucose, fatty acids, insulin-like growth factor-I, insulin, growth hormone, ghrelin, leptin, and perhaps myostatin appear to play key roles. Many of these factors are affected by changes in the somatotropic axis that are a consequence of, or are needed to support, high milk production. Ovarian tissues also respond directly to metabolic inputs, with consequences for folliculogenesis, steroidogenesis, and the development of the oocyte and embryo. Little doubt exists that appropriate nutritional management before and after calving is essential for successful reproduction. Changes in body composition are related to the processes that lead to ovulation, estrus, and conception. However, better indicators of body composition and measures of critical metabolites are required to form precise nutritional management guidelines to optimize reproductive outcomes. The eventual solution to the reduction in fertility will be a new strategic direction for genetic selection that includes fertility-related traits. However, this will take time to be effective, so, in the short term, we need to gain a greater understanding of the interactions between nutrition and fertility to better manage the issue. A greater understanding of the phenomenon will also provide markers for more targeted genetic selection. This review highlights many fruitful directions for research, aimed at the development of strategies for nutritional management of reproduction in the high-producing subfertile dairy cow.

In mature male sheep, the level of nutrition acutely influences the secretion of reproductive hormones. The mechanism involved is not fully understood but findings in humans and laboratory rodents would suggest a major role for leptin that is secreted from adipose tissue and then travels via the circulation to the central nervous system. Before we can begin to test this hypothesis, we need to be able to measure leptin concentrations in blood plasma and cerebrospinal fluid. We have therefore developed a radioimmunoassay using antibodies raised against biologically active recombinant bovine-ovine leptin. Using this assay, we found that plasma concentrations of leptin were highly correlated to back-fat thickness and to the ratio of back-fat thickness to liveweight, in female and castrated male sheep. Plasma concentrations of leptin were higher in female sheep than in castrated or intact male sheep. Serial samples (every 5 min) suggested that the secretion of leptin in male sheep is episodic but it does not appear to show clear pulsatility, increases post-prandially, or a diurnal rhythm. Leptin concentrations in both plasma and cerebrospinal fluid increased within 5 days in male sheep fed a diet with a high content of energy and protein that also stimulates the secretion of LH pulses. These data suggest that in sheep, as in other species, leptin production is correlated with the mass of adipose tissue and that the hormone passes from the circulation to the cerebrospinal fluid and then to hypothalamic sites. There, it may affect appetite and perhaps GnRH secretion. The role of leptin in the link between nutrition and reproduction needs further investigation.

The present study examined whether observers could distinguish between cattle that are naïve to road transport and the same cattle after becoming more habituated to transport. The behavioural expression of cattle was assessed through the method of qualitative behavioural assessment (QBA), and these assessments were correlated with various physiological parameters. Fourteen Angus steers were assessed during their first road trip and then again on their ninth trip, 15 days later. Blood samples were collected immediately before and after transport, and heart rate and core body temperature were measured continuously throughout each trip. Video footage recorded during each trip was edited and clips showing each individual within the first 30 min of departure were randomly ordered and shown to observers for QBA. There was significant (P < 0.001) consensus among 40 observers in their assessment of behavioural expression of the cattle. Transport-naïve cattle were described as more ‘agitated’, while transport-habituated were described as more ‘calm’. Core body temperature (P < 0.01), plasma glucose (P < 0.05) and the neutrophil : lymphocyte ratio (P < 0.01) were higher for the first trip than for the habituated trip (P < 0.01). QBA were significantly correlated with core body temperature (P < 0.01), heart rate (P < 0.01), plasma glucose (P < 0.05) and the neutrophil : lymphocyte ratio (P < 0.01). QBA appears to be a valid and integrative method of assessing cattle welfare under the conditions tested within the present study. There was significant consensus in the ability of human observers to interpret behavioural expression of cattle during this experiment. In addition, observers could identify differences in behavioural expression between cattle that were naïve versus habituated to transport, and these differences were supported by physiological measurements.