Bonus Tydskrif WINTER 2024

www.deheus.co.za | 031 785 1575 | infosa@deheus.com milk production, which increases milk quantity. As the days are shorter in winter cows are exposed to less light, which reduces the length of their internal clock, and they produce less milk. This may not be a benefit in early lactation but does have its place in the drying off phase. Although milk production is negatively affected by the winter season, it does have a positive influence on fertility. At lower temperatures, cows have an easier time re-conceiving, as they are not under heat stress. Heat stress can reduce the prevalence of oestrus symptoms (resulting in lower oestrus detection rates) as well as compromising hormone status and blood flow, which also reduce the chances of conception. It has also been shown that ovulation rates are increased during shorter photoperiods. Dry cows The impact of temperature and photoperiods on dry cows differs from its impact on cows in milk. Some studies show that shorter photoperiods allow for greater recovery of the mammary tissue in the dry period. This may be due to shorter daylengths which decrease prolactin secretion. Prolactin is a hormone that helps induce milk production. By suppressing this hormone, milk production is halted, and mammary involution occurs. There is some evidence that suggests this leads to increased milk production during the early stages in the next lactation because the mammary tissue has been given time to fully recuperate. Regardless of the exact cause, it has been proven that shorter photoperiods in the dry period help with greater milk volumes in the next lactation. Another factor that influences dairy cows during the dry period is heat stress. Heat stress increases prolactin concentration. Again, prolactin is a hormone that stimulates milk production. During winter, the effects of heat stress are not present, therefore prolactin secretion decreases quicker than during a typical drying-off period. This allows the cow to complete mammary involution sooner and allows for better recovery of the mammary tissues, as with the shortened photoperiods. How winter impacts the producer Environmental factors are among the greatest challenges milk producers face. Deciding how best to use those factors to one’s advantage is important. Generally speaking, autumn calving is more popular than spring calving for seasonal farms. Looking back at the effects of winter on a dairy cow, this makes sense. Cows that calve down in autumn have a lower demand for DMI as production is lower, reducing the need for sufficient feed. Re-conception rates are also higher during winter, which is when a cow would be artificially inseminated, had it calved down in autumn. Yet, there is also an argument for spring calving, as winter seems to be the best season for drying off. Ultimately, each milk producer should look at his or her entire production system to decide how best he/she can use the influence of winter to positively impact the herd. Contact your local De Heus technical advisor to help identify how winter impacts the dairy cow. Visit https:// www.deheus.co.za/meet-our-team/.