Omission of dry period and effects on the subsequent lactation curve and on milk quality around calving in Italian Holstein cows

Determining the Association of the Dry Period Duration with Dystocia and Stillbirths in Dairy Cows by Considering Parity, Season, and Gestation Length

This study aimed to assess the relationship between the length of the dry period (DL) and the risks of dystocia and stillbirths in Holstein cows. A total of 1072 healthy cows in lactations 1 and ≥2 were categorized based on the DL (mean: 58.07 ± 0.33 days) into three groups: short DL (<40 days; 13.0% of cows), medium DL (40-70 days; 60.1%), and long DL (>70 days; 26.9%). Dystocia occurred in 12.4% of cows, while stillbirths accounted for 4.1% of calves. The medium DL group had the highest number of unassisted calvings. The dystocia rates were 11.4% for cows with gestation (GA) ≤ 274 days; 6.0% for cows with GA = 275-282 days; and 19.9% for cows with GA ≥ 283 days (p < 0.001). In season 1 (November-April), dystocia occurred in 15.0% of cases compared to 8.8% in season 2 (May-October) (p < 0.001). The stillbirth rates ranged from 3.6% to 4.0% for cows with medium and long DLs; while those with a short DL had 5.8% (p < 0.05). The stillbirth rates were 5.2% for cows with GA ≤ 274 days; 3.2% for cows with GA = 275-282 days; and 5.1% for cows with GA ≥ 283 days (p < 0.001). Season 1 had a stillbirth rate of 4.8%, while season 2 had a stillbirth rate of 3.3% (p < 0.001). This research provides insights that could assist the dairy industry in making informed decisions to reduce the incidence rates of dystocia and stillbirths in cows.

Metabolic and production parameters of dairy cows with different dry period lengths and parities

To assess the effects of dry period (DP) length on metabolic, reproductive, and productive parameters, second- (SP) and third- (TP) parity cows were assigned to a traditional (9 weeks, T) or short (5 weeks, S) DP, obtaining four subgroups: second-parity cows with traditional (SPT = 8) and short (SPS = 8) DP, third-parity cows with traditional (TPT = 8) and short (TPS = 10) DP. Plasma insulin-like growth factor-I (IGF-I) and non-esterified fatty acid (NEFA) levels were assessed from 5 weeks before to 14 weeks after parturition. IGF-I concentrations were affected by parity (P < 0.05) and by the interaction of time and DP length (P < 0.01). NEFA levels were affected only by time (P < 0.01). S DP cows showed a shorter interval between calving and ovarian cyclicity resumption (P < 0.01) and a higher milk yield (P < 0.01) and fat and protein corrected milk (P < 0.01) compared with T DP cows. Decreased milk protein content was found in the SPS group compared to the SPT (P < 0.05) and the TPS (P < 0.05) group. In conclusion, a short DP length does not affect reproductive performances, except for hastening the resumption of ovarian cyclicity. A short DP appears to increase milk production and is associated with higher IGF-I levels both in the prepartum and the postpartum period.

Consequences of dietary energy source and energy level on energy balance, lactogenic hormones, and lactation curve characteristics of cows after a short or omitted dry period

Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source-glucogenic (G) or lipogenic (L)-and energy level-standard (std) or low-on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A 30-d DP decreased both the increasing and the declining slope parameters of the lactation curve and the relative rate of decline in milk yield (indicating greater lactation persistency) compared with a 0-d DP, and decreased plasma insulin and IGF-1 concentration, and EB. In conclusion, feeding a G ration after wk 7 in milk improved energy intake and milk production, but did not affect EB compared with an L ration. For cows without a DP, a reduced dietary energy level did not affect milk production and lactation curve characteristics, but did decrease EB and weekly body weight gain. A 30-d DP increased milk yield and lactation persistency, but decreased milk fat and protein content, EB, and plasma insulin and IGF-1, compared with a 0-d DP.

Effects of non-lactating period length on the subsequent calving ease and reproductive performance of Holstein, Brown Swiss and the crosses

The aim of this study was to evaluate the effects of the non-lactating period (NLP) length on the subsequent calving ease and reproductive performance of the purebred Holstein (HO), Brown Swiss (BS) and F1 crosses (BF) of these breeds. The NLP length was classified into four categories: D1: <45d; D2: 45-60d; D3: 60-75d; and D4: >75d. The lesser incidence of calving difficulty in the purebred HO and BF crossbred cows was recorded at D3, with no significant differences with D2 [11.6% and 9.5%; Crude Odds Ratio (COR)=1.10 and 0.84, respectively]. However, the minimum incidence of calving difficulty in the purebred BS cows was at the same NLP length with significant differences with D2 (3.8%; COR=0.31). All reproductive indices of the purebred HO cows were less as the NLP length increased. However, lesser estimates of calving interval and days non-pregnant in purebred BS and BF crossbred cows were recorded at longer (D3) NLP (350 and 328d; 112 and 133d, respectively). Purebred HO cows had decreased milk production at extremely short (D1) and long (D4) NLP. Purebred BS cows, however, were more persistent in milk production and had more consistent body condition scores (BCS). In conclusion, shortening the NLP of the purebred HO cows in addition to making minimum changes in diet composition could be an appropriate solution for improving reproduction. Purebred BS and BF crossbred cows were more persistent in milk production and tolerated the diet changes during the NLP.

Effects of shortening the dry period of dairy cows on milk production, energy balance, health, and fertility: a systematic review

A dry period of 6-8 weeks for dairy cows is generally thought to maximise milk production in the next lactation. However, the value of such a long dry period is increasingly questioned. In particular, shortening the dry period shifts milk production from the critical period after calving to the weeks before calving. This shift in milk production could improve the energy balance (EB), health and fertility of dairy cows. The objective of this study was to systematically review the current knowledge on dry period length in relation to milk production, EB, fertility, and health of cows and calves. A meta-analysis was performed for variables where at least five studies were available. Overall, both shortening and omitting the dry period reduces milk production, increases milk protein percentage and tends to reduce the risk of ketosis in the next lactation. Individual studies reported an improvement of EB after a short or no dry period, compared with a conventional dry period. Shortening or omitting the dry period did not affect milk fat percentage and shortening the dry period did not alter the odds ratio for mastitis, metritis, or fertility measures in the next lactation. So, current evidence for an improvement of health and fertility of dairy cows is marginal and may be partly explained by the limited number of studies which have evaluated health and fertility in relation to dry period length, the limited number of animals in those studies and the variable responses reported.

Association between dry period length and lactation performance, lactation curve, calf birth weight, and dystocia in Holstein dairy cows in Iran

In this study, 65,971 lactations on 41,842 cows in 64 herds were used to determine the association between dry period length (DPL) and lactation performance, lactation curve, calf birth weight, and the incidence of calving difficulty during the subsequent parity in Holstein dairy cows in Iran. The length of the dry period was classified into 7 categories: 0 to 35d, 36 to 50d, 51 to 60d, 61 to 70d, 71 to 85d, 86 to 110d, and 111 to 160d. Cows with the standard DPL (51 to 60d) produced more 305-d milk, fat, and protein over the next lactation compared with those with shorter dry periods. Shorter dry periods (0 to 35d and 36 to 50d) were associated with lower initial milk yield, steeper inclining and declining slopes of the lactation curve, and higher milk persistency compared with dry period length of 51 to 60d. Peak lactation was achieved later in cows with 0- to 35-d and 36- to 50-d dry period length than in those with dry period length of 51 to 60d. We also observed a relationship between DPL and calf birth weight: smaller calf birth weight was recorded with a dry period of 51 to 60d compared with longer dry periods. The incidence of calving difficulty did not differ in cows with 51- to 60-d dry period compared with cows with 0- to 35-d and 36- to 50-d dry periods. In conclusion, the results of this study did not support previous findings that suggested a shorter dry period could be beneficial to dairy production.