Characterization of the nongenetic causes of variation in the calcium content of bovine milk on French farms

Abstract

Milk is an important source of Ca in Western diets. Milk Ca is important for the cheesemaking process and could be a useful biomarker of Ca regulation in cows. The objective of this study was to identify and quantify nongenetic factors affecting the variation of Ca content in bovine milk. During the PhénoFinLait program, a survey was performed in 3 major areas of milk production in France. This survey consisted of collecting milk samples, together with information about herd management and cow nutrition, from 924 commercial farms. More than 200,000 individual milk samples were collected, and Ca content was measured by mid-infrared spectroscopy. Each farm was surveyed several times during the year, and 3 to 6 milk samples were collected from each cow. An equation to predict milk Ca content from mid-infrared spectra was developed based on the Ca contents of 292 milk samples, and the milk Ca contents of the 200,000 samples were then predicted. Milk Ca content was lowest in Holstein cows, intermediate in Montbéliarde cows, and highest in Normande cows. For all 3 breeds, milk Ca decreased during the first month of lactation and increased after the fourth month of lactation, with the range between minimum and maximum values largest in Holsteins, intermediate in Montbéliardes, and smallest in Normandes. Milk Ca content also decreased with parity in all 3 breeds. By using multiple factorial analysis, 6 major feeding strategies employed on French dairy farms were characterized based on the data from the survey. Calendar month and cow feeding strategy affected milk Ca content, which dropped in the spring during grazing turnout and was lower when cows were fed fresh and conserved grass rather than corn silage. In conclusion, environmental factors induce variations in milk Ca content in addition to the genetics of the cows, which to date have been identified as a main factor of variation of milk Ca content in dairy cows. In several of the tested conditions, increases in milk production and in the amount of Ca daily secreted in milk were associated with a decrease in milk Ca content as though the mammary gland operated to limit the exportation of Ca when milk production rapidly increased. This result would suggest that milk Ca content could be a biomarker of Ca regulation in dairy cows.

Effects of dietary Zeolite supplementation on milk yield and composition and blood minerals status in lactating dairy cows

“…In our study, the range of Ca concentration for all milk samples collected over the experimental period (900-1290 mg/kg, data not shown) was lower in magnitude to that (1110-1470 mg/kg) reported by O'Brien et al (1999), Auldist et al (1999) and Gulati et al (2018). Variations in milk Ca content have been clearly related to the breed, season, stage of lactation, parity, and feed strategy (Nogalska et al 2017;Gaignon et al 2018). In addition, it is well established that the secretion of Ca into milk was regulated by mammary gland secretion of parathyroid hormone-related protein (PTHrP), bone accretion and resorption dynamics, the digestive tract, and kidneys (Boudon et al 2016;Gaignon et al 2018).…”

“…The lower milk Ca content in Tunisian dairy heard was most probably related to the intensive production system based on conserved grass (such as silage or hay), and high quantities of concentrates (Nogalska et al 2017;Gaignon et al 2018).…”

“…Variations in milk Ca content have been clearly related to the breed, season, stage of lactation, parity, and feed strategy (Nogalska et al 2017;Gaignon et al 2018). In addition, it is well established that the secretion of Ca into milk was regulated by mammary gland secretion of parathyroid hormone-related protein (PTHrP), bone accretion and resorption dynamics, the digestive tract, and kidneys (Boudon et al 2016;Gaignon et al 2018).…”

Effect of calcium intake and dietary cation anion difference in early lactation on bone mobilization dynamics all over lactation in dairy cows

“…Cows were assigned to the three treatments to allow a homogenous representation of groups and parity within each treatment, and as similar as possible, similar averages of mature equivalent milk production and milk protein contents as observed in the first 32 weeks of the previous lactation. The mature equivalent milk production was estimated as equivalent to milk production for a third lactation cow, i.e., 120% of the milk production for primiparous cows and 104% for cows lactating for a second time, as established from the data used by Gaignon et al (24). Measurement started 3 weeks before the average expected date of calving for each group, on 5 cows of the initial 6, with the extra cow being kept only for blood analyses to replace a cow whose actual calving date might occur too far from the expected date.…”

“…VanHouten et al (22) showed that a decrease in Ca intake in mice induced a lower Ca secretion in milk and a higher bone resorption mediated by PTHrP secretion, with both mediated by the Ca-sensing receptor ( CaSR ) in the mammary gland; those results suggest that the monitoring of milk Ca content during lactation could be an inexpensive way to indirectly estimate the dynamics of bone resorption. Mid-infrared spectra technology allows a rapid and inexpensive way to determine the milk Ca content (23,24). Data collected during several stages of lactation in dairy cows with different parities (25) suggested that milk Ca and P contents could be related to the plasma concentrations of biomarker of bone formation and resorption.…”