INTRODUCTION

The profitability and sustainability of a cow–calf operation are dependent on the longevity of each breeding female person and the production of a live dogie every yr. If a heifer calves before in the calving season (offset 21-twenty-four hour period period), they take more time to heal and resume cycling before the next breeding flavour commences in lodge to maintain a 365-d calving interval. A limited number of reports are bachelor regarding the human relationship between cow calving time every bit a heifer and subsequent longevity and production every bit cows (Burris and Priode, 1958; Wiltbank, 1970; Lesmeister et al., 1973; Sprott, 2000; Funston et al., 2012; Cushman et al., 2013). Burris and Priode (1958) showed that cows calving late in i twelvemonth tended to go along that trend, calving belatedly in the following year or coming up open. Similarly, Wiltbank (1970) stressed the importance of heifers conceiving early in their first breeding in order to have good lifetime production functioning and was 1 of the first to suggest calving heifers earlier than the balance of the herd given their longer postpartum interval (fourscore–100 d vs. 50–sixty d for cows). Lesmeister et al. (1973) demonstrated the importance of breeding heifers to calve early to maintain calving catamenia throughout their time in the herd and that heifers that calve early will produce more kilograms of calf in their lifetime than heifers that calve later in their first calving. Sprott (2000) analyzed calving records from five Texan herds to show that average lifetime calf weight is highest for females whose first calf was born in the start 21 d of the calving season. Similarly, Funston et al. (2012) reviewed 13 years of production records from Gudmundsen Sandhills Laboratory and constitute calving period influenced a heifer's herd performance with heifers that were born in the first calving menstruation having college kickoff conception rate, per centum calving in first 21 d, start calf weaning weight and 2nd conception charge per unit than heifers built-in in the second or third calving flow. Furthermore, Cushman et al. (2013) showed that having heifers calve early in their first calving resulted in increased herd retentiveness and the additional kilograms of calf weaned by an early-calving heifer equated to the product of an actress calf during her lifetime. The objective of this ongoing written report is to investigate the influence of calving early equally heifer on her lifetime reproductive performance and productivity using a western Canadian data ready.

MATERIALS AND METHODS

Source of Data

Data were aggregated into a database from the Western Beef Evolution Centre's (WBDC; Saskatchewan, Canada) beef cattle research herd product records. The WBDC follows typical management practices of western Canada for beef heifer evolution, cow breeding, and nutrition, equally described elsewhere (Krause et al., 2013; Lardner et al., 2014; Damiran et al., 2016). Data for the spring calving herd collected betwixt 2001 and 2017 were used for this report. The breeding flavor at WBDC began approximately June 20 each yr and lasted for ~65 days. Weaning occurred each yr in late October (at ~160 d of age). Data were trimmed to remove heifers that produced a twin at whatsoever point during their life. Females sold or culled for non-breeding reasons (due east.1000., mothering, milk, conformation, temperament) were removed from the data set. Heifers were likewise eliminated from the data set if proper consignment to an initial calving group was not possible due to abortion, or birth of an abnormal or premature calf. The final information set for this study consisted of 211 Blackness Angus and Angus crossbred heifers born from 1999 to 2008.

Each female person's calving engagement was assigned a number (Julian appointment) respective with calving span. Postpartum recovery period was estimated by subtracting 282 d (average gestation length) from the calving interval (Damiran et al., 2016). Two-year-old first-dogie heifers were assigned to one of three 21-day calving periods based on the engagement their first dogie was born. Each subsequent calf born to the cow was also assigned to a calving group (or flow), but for assay purposes the female person remained in the group number assigned for her beginning parturition. For example, a moo-cow that calved in menstruation two as a heifer simply then had her next three calves in period three was analyzed as a period 2 female. Boilerplate lifetime product was calculated equally the mean production of all calves whose dams were classified in a detail calving group every bit heifers. Weaned calf revenue was calculated, $/cow = Calf cumulative weaning BW, kg/cow × WCP, $/kg, where WCP = weaned 249.4 kg (550 lb) calf prices, over the last ix years (2008–2017) in Saskatchewan, Canada, have averaged $3.68/kg (CANFAX, 2017). All dollar values are in Canadian dollars.

Statistical Analysis

Data (heifer age of birth, Julian twenty-four hour period of calving, calf birth weights, calving interval, calf weaning historic period and weight, adjusted 205-d weaning weight of all calves that survived until weaning, and longevity of cows) were analyzed using the MIXED process of SAS 9.2 (SAS, 2003). The model used for the analysis was: Y ij = µ + T i + e ij ; where Y ij was an observation of the dependent variable ij ; µ was the population mean for the variable; T i was the fixed effect of the contemporary heifer calving group (menstruation 1, flow ii, and period 3); and eastward ij was the random error associated with the observation ij. Heifer was considered an experimental unit. For all statistical analyses, significance was alleged at P < 0.05.

RESULTS AND DISCUSSION

Cow Retentiveness and Longevity

As indicated previously, in this written report, cows were culled or sold from the herd if they failed to be get meaning (e.1000., open). Figure 1 depicts percentages of cows remaining in the herd over time out to ninth calving based on retentivity information. Retaining percentage of catamenia one cows was 6.five–18.3% and 2.nine–24.i% units greater than those of period 2 and period 3 cows, respectively. Thus, heifers that calve later at their commencement calving neglect to remain in the herd equally long every bit heifers that calve before (offset 21 days) at their get-go calving. The results of this study agree with the previous findings (Cushman et al., 2013) in that having heifers calve early in their commencement calving would increase their retention in the herd.

Effigy 1.

Analysis of the influence of calving period on herd survival from Western Beef Development Centre, Saskatchewan, Canada. Results from Angus and Angus crossbred heifers (n = 211) from WBDC. Period 1 = calved in the first 21 days; Period 2 = calved in the second 21 days; Period 3 = calved in the third 21 days and after as heifer.

Analysis of the influence of calving period on herd survival from Western Beef Development Center, Saskatchewan, Canada. Results from Angus and Angus crossbred heifers (n = 211) from WBDC. Menstruation 1 = calved in the first 21 days; Period 2 = calved in the second 21 days; Period three = calved in the third 21 days and afterward as heifer.

Effigy one.

Analysis of the influence of calving period on herd survival from Western Beef Development Centre, Saskatchewan, Canada. Results from Angus and Angus crossbred heifers (n = 211) from WBDC. Period 1 = calved in the first 21 days; Period 2 = calved in the second 21 days; Period 3 = calved in the third 21 days and after as heifer.

Analysis of the influence of calving flow on herd survival from Western Beef Development Heart, Saskatchewan, Canada. Results from Angus and Angus crossbred heifers (due north = 211) from WBDC. Menstruation 1 = calved in the first 21 days; Menstruation 2 = calved in the second 21 days; Period three = calved in the third 21 days and after as heifer.

The longevity of a beefiness female is important to the sustainability and profitability of any beef operation (Cushman et al., 2013). Increasing longevity by improving retention of females tin increase herd size. Figure 2 presents influence of calving period on beefiness cow average longevity from WBDC. In this study, heifers that had their first calf during the first 21-day period of the calving season had increased (P < 0.05) longevity compared with heifers that calved in the second and tertiary 21-day periods (7.2 ± 0.3, 6.5 ± 0.4, and vi.2 ± 0.iv year for period 1, menstruation 2, and period 3, respectively). However, no departure (P > 0.05) was observed betwixt period 2 and menstruation 3 groups in longevity. The reason for the obtained results on cow retentivity time and longevity can exist explained as Bridges (2013) noted, if a heifer conceives late and later calves belatedly, she has less time from calving until the start of the subsequent breeding season, and then she is more likely to be anestrus, or non having estrous wheel, at the starting time of the breeding flavor and volition likely conceive late over again in the second convenance flavor; this cycle continues to repeat until eventually she fails to conceive in a confined convenance menstruation and is culled from the herd.

Effigy ii.

Influence of calving menstruum on average lifetime in herd from Western Beefiness Development Centre, Saskatchewan, Canada. Menses 1 = calved in the first 21 days; Period ii = calved between 24-hour interval 22 and 43; Menses three = calved afterwards day 44. a,bBars with different superscripts are dissimilar at P < 0.05.

Influence of calving menstruum on average lifetime in herd from Western Beef Development Heart, Saskatchewan, Canada. Flow i = calved in the beginning 21 days; Period 2 = calved between mean solar day 22 and 43; Period 3 = calved after day 44. a,bBars with different superscripts are different at P < 0.05.

Figure 2.

Influence of calving menses on average lifetime in herd from Western Beefiness Evolution Centre, Saskatchewan, Canada. Period one = calved in the outset 21 days; Catamenia 2 = calved betwixt day 22 and 43; Menstruation 3 = calved after day 44. a,bBars with different superscripts are unlike at P < 0.05.

Influence of calving catamenia on boilerplate lifetime in herd from Western Beef Evolution Center, Saskatchewan, Canada. Period 1 = calved in the first 21 days; Flow ii = calved betwixt day 22 and 43; Period 3 = calved subsequently 24-hour interval 44. a,bConfined with different superscripts are different at P < 0.05.

Effect of Initial Calving Group on Cow Lifetime Productivity

Effects of first calving catamenia on a beef cow's lifetime productivity are presented in Table one. When product data for each year were pooled, cow groups were different from each other (P < 0.05) in calving appointment; and were 107 (± 0.ix), 110 (± 1.1), and 119 (± 1.3) d for menses 1, period ii, and period 3 cows, respectively. This outcome indicated that the females that calved early every bit heifers tended to calve earlier throughout the remainder of their productive lives than the females that calved later in their commencement calving. The interval between postpartum heat and beginning of pregnancy is the other component of the reproductive bicycle. In this report, period one (95 d) and period 2 (90 d) cows were similar (P > 0.05) in the length of estimated postpartum interval; both groups were greater (P < 0.01) than menses three cows (76 d). A shorter calving interval was also observed for period 3 (belatedly calving) females. These 2 results may seem counter intuitive at first, but can be explained past fall out with a defined 65 d breeding season. Only the most reproductive females from period 3 remained in the study (the ones with curt postpartum intervals), while females in periods 1 and 2 had the leeway to non conceive in their outset (and even second) cycle of the breeding season and still cease upward pregnant at the terminate of the breeding flavor. Equally cows (2nd through 9th calving), estimated postpartum interval did not differ (P > 0.05; data non shown) past heifer calving grouping and averaged ~81 d (catamenia 3 grouping) to 87 d (period 1 group).

Table 1.

Result of get-go calving period on beef cow lifetime productivity

Particular Calving catamenia 1 SEM 2 P value
Period 1 Period 2 Period 3
Initial heifer, due north 87 66 58
Age at starting time calving, d 731 a 751 b 778 c three.6 <0.01
Calving interval, d 376 a 372 a 358 b 1.viii <0.01
Postpartum interval, 3 d 95 a 90 a 76 b ii.ane <0.01
Calf birth engagement, Julian day 107 b 110 b 119 a 1.1 <0.01
Calf birth BW, kg 40 forty twoscore 0.5 0.80
Dogie age at weaning, Julian day 167 a 164 a 149 b two.0 <0.01
Calf weaning BW, kg 218 a 217 a 202 b 2.v <0.01
Pre-weaning ADG, kg/d one.1 ab 1.1 a 1.0 b 0.02 0.06
Calf adjusted 205-d weaning BW, kg/moo-cow 264 a 264 a 255 b two.1 <0.02
Calf cumulative weaning BW, kg/cow 1157 a 947 ab 841 b 84.v 0.04
Calf cumulative adapted 205-d weaning BW, kg/cow 1401 a 1156 ab 1064 b 97.4 0.03
Total produced calves, northward/moo-cow v.iv a 4.v b four.2 b 0.36 0.03
Weaned calves acquirement, $/cow 4251 a 3478 ab 3091 b 294.7 0.01
Item Calving period one SEM ii P value
Period 1 Menstruum two Menstruum 3
Initial heifer, n 87 66 58
Age at start calving, d 731 a 751 b 778 c 3.vi <0.01
Calving interval, d 376 a 372 a 358 b 1.8 <0.01
Postpartum interval, 3 d 95 a 90 a 76 b 2.one <0.01
Calf birth appointment, Julian 24-hour interval 107 b 110 b 119 a 1.one <0.01
Calf nativity BW, kg 40 xl forty 0.5 0.lxxx
Calf historic period at weaning, Julian day 167 a 164 a 149 b ii.0 <0.01
Calf weaning BW, kg 218 a 217 a 202 b ii.v <0.01
Pre-weaning ADG, kg/d 1.i ab 1.1 a one.0 b 0.02 0.06
Calf adjusted 205-d weaning BW, kg/cow 264 a 264 a 255 b 2.one <0.02
Calf cumulative weaning BW, kg/moo-cow 1157 a 947 ab 841 b 84.5 0.04
Calf cumulative adjusted 205-d weaning BW, kg/cow 1401 a 1156 ab 1064 b 97.four 0.03
Full produced calves, north/cow 5.4 a 4.5 b 4.ii b 0.36 0.03
Weaned calves revenue, $/cow 4251 a 3478 ab 3091 b 294.7 0.01

1 Menses ane = calved in the showtime 21 days, Menstruation 2 = calved between day 22 and 43, Period 3 = calved day 44 or later.

2 SEM, pooled standard error of means.

3 Estimated postpartum interval from calving to conception based on consecutive calving dates and assuming a 282-d gestation length.

abc Means without a mutual superscript differ (P ≤ 0.05).

Table 1.

Issue of commencement calving flow on beefiness cow lifetime productivity

Particular Calving period 1 SEM ii P value
Period 1 Menstruation two Period iii
Initial heifer, n 87 66 58
Historic period at first calving, d 731 a 751 b 778 c three.6 <0.01
Calving interval, d 376 a 372 a 358 b 1.8 <0.01
Postpartum interval, 3 d 95 a 90 a 76 b 2.1 <0.01
Calf nativity date, Julian day 107 b 110 b 119 a 1.1 <0.01
Calf birth BW, kg 40 twoscore xl 0.five 0.80
Calf age at weaning, Julian day 167 a 164 a 149 b two.0 <0.01
Calf weaning BW, kg 218 a 217 a 202 b 2.5 <0.01
Pre-weaning ADG, kg/d 1.i ab 1.i a 1.0 b 0.02 0.06
Calf adjusted 205-d weaning BW, kg/moo-cow 264 a 264 a 255 b 2.one <0.02
Dogie cumulative weaning BW, kg/cow 1157 a 947 ab 841 b 84.5 0.04
Calf cumulative adjusted 205-d weaning BW, kg/moo-cow 1401 a 1156 ab 1064 b 97.four 0.03
Total produced calves, n/cow v.4 a 4.5 b four.two b 0.36 0.03
Weaned calves revenue, $/cow 4251 a 3478 ab 3091 b 294.seven 0.01
Particular Calving menstruation 1 SEM two P value
Period 1 Menses two Menstruation 3
Initial heifer, n 87 66 58
Age at first calving, d 731 a 751 b 778 c iii.6 <0.01
Calving interval, d 376 a 372 a 358 b 1.8 <0.01
Postpartum interval, 3 d 95 a 90 a 76 b 2.one <0.01
Calf birth date, Julian day 107 b 110 b 119 a 1.1 <0.01
Dogie nascency BW, kg twoscore xl 40 0.5 0.fourscore
Calf age at weaning, Julian solar day 167 a 164 a 149 b 2.0 <0.01
Calf weaning BW, kg 218 a 217 a 202 b 2.5 <0.01
Pre-weaning ADG, kg/d 1.1 ab i.i a one.0 b 0.02 0.06
Calf adjusted 205-d weaning BW, kg/cow 264 a 264 a 255 b ii.1 <0.02
Calf cumulative weaning BW, kg/cow 1157 a 947 ab 841 b 84.5 0.04
Calf cumulative adapted 205-d weaning BW, kg/cow 1401 a 1156 ab 1064 b 97.4 0.03
Total produced calves, n/cow 5.four a iv.5 b 4.2 b 0.36 0.03
Weaned calves revenue, $/moo-cow 4251 a 3478 ab 3091 b 294.vii 0.01

ane Period one = calved in the first 21 days, Menses 2 = calved betwixt twenty-four hours 22 and 43, Period three = calved day 44 or later.

2 SEM, pooled standard error of means.

3 Estimated postpartum interval from calving to formulation based on consecutive calving dates and assuming a 282-d gestation length.

abc Means without a common superscript differ (P ≤ 0.05).

In beef cattle, prolonged postpartum intervals can subtract the proportion of cows that are cycling at the beginning of the convenance season thereby decreasing pregnancy rates and kilogram of calf weaned per cow exposed during a breeding season. Postpartum interval length is influenced by several factors, including suckling, diet, age, dystocia, genetic variation, stress, and illness (Short et al., 1990; Yavas and Walton, 2000). In improver, postpartum interval to first behavioral oestrus decreases every bit cows calve later in the calving flavor and varies with brood (Short et al., 1990; Cushman et al., 2007), but averages ~62 d (Cushman et al., 2007). When lifetime productivity for each animal was pooled, dogie actual average weaning weights were 15 kg heavier (P < 0.01) and average adjusted 205-d weaning weights were 9 kg heavier (P < 0.01) for period one and ii cows (Tabular array 1) than period 3 cows. Calf gain to weaning (ADG) was lower (P < 0.05) for the calves from period three cows (1.05 kg/d) than for the calves built-in to catamenia one (ane.08 kg/d) and menses 2 cows (1.09 kg/d) (Tabular array 1).

Reproductive functioning is one of the biggest factors affecting beef cow production efficiency and profitability. Reproduction has been estimated to exist three to ix times more influential on profitability than other production traits (Melton, 1995). Average lifetime calves weaned for WBDC cows that calved in the start, second, and third 21-day periods was 5.4 ± 0.32, 4.5 ± 0.37, and iv.two ± 0.39/cow, respectively (Tabular array 1). Due to combined effects of greater average number of calves weaned over lifetime and actual dogie weaning weights, cows that had their first calf during the first 21-24-hour interval period had (P < 0.01) greater total weight weaned (1157.1 ± 70.0 kg) compared with heifers that calved in the 2d (946.6 ± 82.1 kg) or third (841.4 ± 87.six kg) 21-d period (Table 1).

One of the almost important findings of this report was females that calve early when they are heifers can produce more cumulative kilograms of weaned calf in their lifetime than females that calved subsequently (after first 21 days) as heifers (i.e., cumulative kilograms of calf was xviii.2% and 27.three% greater than that of catamenia 2 and catamenia 3 cows, respectively), which agrees with others' findings (Lesmeister et al., 1973). Period ane cows were either numerically or significantly greater than catamenia 2 (P > 0.05) and period iii cows (P < 0.01); this generated an additional $773 to $1160 in weaned calf revenues over their lifetime. This represents a large financial advantage for cow–calf producers.

The differences in average lifetime production betwixt cow groups in this study were probable associated with differences in total number of calves weaned over lifetime, but some differences were associated with calf weaning weight. In full general, in western Canada, where price of production has been measured at simply under $962 per cow wintered (AAF, 2016) a heifer will need to wean a minimum of v consecutive calves to recoup her development costs (K. Larson, Western Beef Development Centre, Humboldt, SK, Canada, personal communication). This economic threshold of needing to wean v calves was simply reached by the females that calved early as heifers. Thus, the findings of this study demonstrate why it is so important for cow–dogie producers to ensure that their replacement heifers conceive as early as possible in their first breeding exposure.

CONCLUSIONS AND IMPLICATIONS

As evidenced by the findings of this written report, heifers that calved early in their first calving season had increased longevity (pregnancy rates) and weaned more calves, compared with heifers that calved afterward in the calving season. Moreover, in her lifetime, heifers that calved during the first 21-mean solar day catamenia of their first calving flavour weaned approximately one more calf compared with heifers that calved subsequently in the calving season. Therefore, developing heifers and then that they conceive early in the breeding flavor and subsequently calve early in the calving flavor is disquisitional for heifer longevity in the herd as well every bit the operation of her progeny in subsequent generations.

ACKNOWLEDGMENTS

We give thanks the staffs of the Western Beef Development Centre for their conscientious husbandry and information drove over the decades. Amartuvshin Daalkhaijav helped in data grooming. This study was funded past the Saskatchewan Agronomics Evolution Fund (ADF#20150160).

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