Source: Michigan State University Extension, Jerad Jaborek
Over the course of the year the number of natural daylight hours changes from 9 to 16 hours in Michigan, with the shortest day in mid-December and the longest day in mid-June. Previous research has reported increased productivity from many livestock species in response to photoperiod manipulation. This includes greater egg production for chickens and greater milk production for dairy cows exposed to a greater photoperiod length. This article will review some studies investigating the effects of photoperiod on the performance of growing cattle and discuss the impact for beef producers.
According to a 1984 article “The influence of photoperiod on body weight gain, body composition, nutrient intake and hormone secretion” by the Journal of Animal Science, a large quantity of the research investigating the effects of photoperiod on cattle production compares short-daylength (SDL; 8 hours light:16 hours darkness) with long-daylength (LDL; 16 hours light:8 hours darkness). Therefore, this type of research is primarily conducted during the winter months that have SDL and artificial lighting is used to extend the photoperiod to emulate LDL. Much of the early research investigating the effects of photoperiod on cattle performance was conducted at Michigan State University (MSU) using Holstein heifer and bull calves. Initial studies reported a 16% greater body weight gain for Holstein heifer calves exposed to LDL compared with SDL. Interestingly, 24 hours of continuous light exposure resulted in a similar performance response between Holstein heifer calves receiving SDL, whereas heifer calves exposed to LDL had a 10-15% greater average daily gain (ADG) and 7% greater feed intake compared with SDL and 24 hours of continuous light. Improved growth in these experiments occurred after the initiation of 14 to 17 hours of light exposure or the initiation of 8 to 10 hours of darkness. Therefore, the regulation of growth in cattle appears to be regulated in a circadian rhythm requiring both periods of light and dark.
The use of continuous lighting has been practiced for many years, anticipating increased hours of light exposure would increase cattle performance by encouraging a greater number of bunk visits and greater feed intake. A study done by Tucker and others in the Journal of Dairy Science, no differences were observed for the eating behavior, including total eating time, number of meals, and average time spent eating for Holstein cows when exposed to either 24 hours of continuous light or LDL. Studies from Tucker and others reported more eating events during daylight hours for Holstein heifers exposed to LDL compared with SDL, but no differences in the amount of total feed consumed. When offered a similar amount of feed, high energy diets comprised of mostly high moisture corn resulted in a 18% greater ADG and lower energy diets containing mostly corn silage resulted in a 11% greater ADG for Holstein heifer calves exposed to LDL compared with SDL. A 1996 article “The influence of day length and temperature on food intake and growth rate of bulls given concentrate or grass silage ad libitum in two housing systems” by Animal Science, reported that for bulls in Sweden, ADG increased as daylength increased (December to May) and ADG decreased as daylength decreased (June to November). Similarly, energy intake slightly lagged ADG, such that energy intake was greatest in June and lowest in December for bulls offered a high concentrate diet. It appears that a greater voluntary feed intake may not be necessary for the improvement of growth rate due to LDL when compared with SDL, as the increase in feed intake typically lags the change in ADG.
In agreement, a 1992 article “Random variation in voluntary dry matter intake and the effect of day length on feed intake capacity in growing cattle” by Acta Agriculturae Scandinavica A-Animal Sciences, reported a relatively small increase (+0.32%) in dry matter intake per hour of increased day length for bulls consuming a low energy diet, which would correspond to a 2.24% difference in dry matter intake between December and June in Michigan. In contrast, a 1990 article “Dry matter intake by feedlot beef steers: Influence of initial weight, time on feed, and season of year received in yard” by the Journal of Animal Science, reported a 10% difference in dry matter intake between the highest and lowest months, with a greater feed intake occurring during the fall and spring and a lesser feed intake occurring during the winter and summer months by feedlot cattle consuming a high concentrate diet. While no reports were made because of daylength, the same researchers suggest heat stress decreased feed intake in heavier cattle, while cold stress tended to decrease the feed intake of lighter weight cattle in Oklahoma. The effect of confounding or uncontrolled variables, such as temperature, quite possibly influence or mask the effect of daylength on cattle growth and performance, which likely contributes to some of the conflicting results.
Cattle are not distinct seasonal breeders like other livestock species such as sheep, goats, and horses. Although, daylength appears to elicit some regulation of reproductive processes in cattle. Tucker and others, reported that LDL resulted in Holstein heifers reaching puberty sooner than heifers exposed to SDL. Additionally, prepubertal Holstein heifers demonstrated a 9% greater ADG in two experiments and a 3% greater ADG in a third experiment when exposed to LDL compared with SDL. In agreement, when exposed to LDL, Canadain Journal of Animal Science, reported earlier puberty attainment and a 12% greater ADG for prepubertal beef heifers compared with SDL. Interestingly, postpubertal Holstein heifers had a 13% greater ADG in the third experiment when exposed to SDL instead of LDL. For Holstein bull calves, LDL hastened the onset of puberty and increased ADG by 10% compared with SDL. In contrast, a 1980 article “Effect of extended photoperiod in winter on performance of cattle” by Irish Journal of Agricultural Research, reported no effect of photoperiod on growth for Holstein bull calves and for finishing steers. Similarly, no differences in steer performance have been observed due to photoperiod length at MSU. These results would indicate the effects observed in response to photoperiod length are possibly gonadal dependent in cattle.
Carcass composition was reported to differ for cattle when exposed to different photoperiod lengths. Canadain Journal of Animal Science reported a 15% reduction in backfat thickness gain for prepubertal beef heifers exposed to LDL compared with SDL and no differences after beef heifers had attained puberty. However, research from MSU reported the increased body weight gain attained by postpubertal Holstein heifers exposed to SDL resulted in a greater rate of carcass fat deposition and a lesser rate of carcass protein deposition compared with postpubertal heifers exposed to LDL. A 1989 article “Failure of photoperiod to alter body growth and carcass composition in beef steers” by the Journal of Animal Science, shared research from MSU with the use of steers reported no differences for performance or carcass composition due to photoperiod manipulation. A 1997 article “The effect of supplementary light during winter on the growth, body composition and behaviour of steers and heifers”, by Animal Science, reported when exposed to natural day light, a greater rate of fat deposition for postpubertal beef heifers when daylength was decreasing (November to January) and a lesser rate of fat deposition when daylength was increasing (January to March) in the United Kingdom. Likewise, beef steers exposed to LDL had less carcass fat compared with steers receiving natural daylength (SDL) exposure from November to March. Overall, it appears LDL exposure reduces carcass fat accumulation in cattle compared with SDL.
In conclusion, cattle growth and performance is influenced by circadian rhythm, and therefore, can be manipulated with the use of artificial lighting. Heifers and bulls demonstrated a greater growth response to long photoperiods (16 hours) compared with short photoperiods (8 hours) more frequently in studies than compared with steers. This possibly indicates the effects of the photoperiod on cattle growth and performance are partially regulated or influenced by the gonadal sex hormones. Increasing day length results in a greater feed intake for cattle in both open feedlots and covered barns. Additionally, increasing daylength results in greater rate of carcass muscle compared with a greater rate of carcass fat with decreasing daylength. Future research on this topic should attempt to determine the physiological cause of the effect of daylength on cattle growth and performance and demonstrate whether the application of increasing photoperiod via artificial lighting (e.g., LED lights) is a cost-effective practice for the improvements of cattle growth and performance.