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. 2023 Jan 3:101:skad330.
doi: 10.1093/jas/skad330.

Effects of early weaning on the reproductive performance of suckled Nelore cows in the subsequent breeding season

Thiago Kan Nishimura  1 , Amanda Guimarães da Silva  1 , Gabriela Abitante  2 , Carl Robertson Dahlen  3 , Rodrigo Silva Goulart  2 , Germán Darío Ramírez Zamudio  2 , Saulo Luz Silva  2 , Miguel Henrique de Almeida Santana  2 , Arlindo Saran Netto  2 , Paulo Roberto Leme  2 , Guilherme Pugliesi  1
Affiliations

Effects of early weaning on the reproductive performance of suckled Nelore cows in the subsequent breeding season

Thiago Kan Nishimura et al. J Anim Sci. .

Abstract

This study aimed to evaluate the effects of early weaning (EW) on body composition, hormone concentrations and metabolites, and reproductive performance of Nelore cows in the subsequent breeding season (BS). Suckled cows that became pregnant by timed-AI (TAI) in the 2020-BS were exposed in 2021 to early weaning at 150 d (27 primiparous [PRI] and 74 multiparous [MUL]) or conventional weaning (CW) at 240 d postpartum (30 PRI and 77 MUL). Body weight (BW) and body condition score (BCS) were determined at 2020-BS, EW, CW, prepartum, and 2021-BS. Blood samples were collected at EW, CW, prepartum (54.75 ± 0.56 d prepartum), and 2021-TAI and assayed for insulin-like growth factor-1 (IGF-I), non-esterified fatty acid (NEFA), and β-hydroxybutyrate (BHB) concentrations. In 2021-BS, cows were exposed to a P4/E2-based protocol for TAI at day 0 (D0), and a second TAI was performed at D22 in females detected with luteolysis (D20) by Doppler ultrasound. The presence of corpus luteum (CL) on D10, estrous expression, and dominant follicle (DF) diameter, and blood perfusion (BP) on D2 and D0 were determined. Data were analyzed by ANOVA or logistic regression of SAS as a 2 × 2 factorial with main factors of parity (PRI or MUL) and weaning strategy (EW or CW). An interaction of parity and weaning strategy was not observed (P > 0.1), but the weight (kg) and BCS were greater (P < 0.05) in MUL cows at the five timepoints, and EW cows were heavier than CW at the moment of CW (541 vs. 493 kg; and 5.3 vs. 4.3), prepartum (551 vs. 506 kg; and 5.2 vs. 4.4) and 2021-BS (475 vs. 450 kg; and 4.5 vs. 3.7). Plasma urea concentration at 2021-BS was greater (P = 0.01) for PRI than for MUL. A parity-by-time interaction was observed (P ≤ 0.05) for concentrations of IGF-I, NEFA, and BHB. PRI cows had greater (P ≤ 0.05) concentrations of IGF-I at EW and greater (P ≤ 0.05) prepartum concentrations of NEFA and BHB than MUL cows. The proportion of cows with CL at D10 was not affected (P > 0.1) by weaning but was greater (P < 0.05) in MUL than in PRI cows (40.4 vs. 15.7%). The diameter of DF and proportion of BP on D0 were greater (P < 0.05) in EW cows than in CW cows. The pregnancy rate (P/AI, %) at the first TAI was greater (P < 0.05) in EW cows (60% vs. 45%), whereas no difference (P > 0.1) was observed at the second TAI. Cumulative P/AI (first and second TAIs) was greater (P < 0.05) in EW cows (81% vs. 63%). In conclusion, weaning at 150 d in Nelore cattle is a strategy to successfully recover the parous cow's body condition and to improve pregnancy success in the next BS, regardless of the cow's parity order.

Keywords: Beef cattle; body condition score; metabolic status; multiparous cows; nutritional status; primiparous cows.

Plain language summary

The nutritional condition and body energy reserves at parturition are important factors that can affect the reproductive performance of suckled Nelore cows. Also, decreasing the weaning time can benefit the cow’s metabolic status. The present study evaluated the effect of two periods of weaning (150 vs. 240 d) on the reproductive performance of the Nelore dam in the subsequent breeding season. The results of the present study indicate that early weaning: 1) improves the body condition, rump fat thickness, and metabolic condition of Nelore cows for the subsequent breeding season; 2) provides better ovarian follicle growth and blood perfusion during the subsequent timed artificial insemination program; 3) enhances the pregnancy rates in the subsequent breeding season.

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Conflict of interest statement

The authors declare no real or perceived conflicts of interest.

Figures

Figure 1.
Figure 1.
Schematic of experimental design to evaluate the reproductive performance of Nelore cows exposed to early (150 d) or conventional (240 d) weaning strategies in the previous production cycle. Abbreviations: BCS, body condition score; BS, blood samples; RFT, rump fat thickness; US OV, ovary ultrasonography; PD, pregnancy diagnosis; TAI, timed artificial insemination.
Figure 2.
Figure 2.
Mean ± SEM of body weight and body condition score in primiparous and multiparous Nelore cows that were weaned at early (150 d of age) or at conventional (240 d of age) time points during the previous production cycle. Main effects of weaning strategy (W), dam’s parity (D), time (T), and interactions (W*T and D*T) that were significant or approached significance are shown. *Indicates difference (P < 0.05) in weight among times. a,b,c,d,e Within a group, means without a common letter differed (P < 0.05).
Figure 3.
Figure 3.
Mean ± SEM of pregnant shrunk body weight, non-pregnant shrunk body weight, and pregnant compounds in primiparous and multiparous Nelore cows that were weaned at early (150 d of age) or at conventional (240 d of age) time points during the previous production cycle. Main effects of weaning strategy (W), dam’s parity (D), time (T), and interactions (W*T and D*T) that were significant or approached significance are shown. *Indicates difference (P < 0.05) in weight among times. a,b,c,dWithin a group, means without a common letter differed (P < 0.05).
Figure 4.
Figure 4.
Mean ± SEM average daily gain (ADG) in primiparous and multiparous Nelore cows that were weaned at early (150 d of age) or at conventional (240 d of age) time points during the previous production cycle. Main effects of weaning strategy (W), dam’s parity (D), time (T), and interactions (W*T and D*T) that were significant or approached significance are shown. Upper panel: Main effects of dam’s parity-by-time interaction (D*T). Different uppercase letters indicate difference between time and dam’s parity (P < 0.05) in ADG in primiparous cows. Different lowercase letters indicate difference between dam’s parity-by-time (P < 0.05) in ADG in multiparous cows. Bottom panel: Main effects of weaning strategy by time interaction (W*T). *Indicates difference (P < 0.05) in ADG among times in between dam’s parity (Upper panel), and between weaning strategy (Bottom panel).
Figure 5.
Figure 5.
Mean ± SEM rump fat thickness in primiparous and multiparous Nelore cows that were weaned at early (150 d of age) or at conventional (240 d of age) time points during the previous production cycle. The main effects of weaning strategy (W), dam’s parity (D), time (T), and interactions (W*T and D*T) that were significant or approached significance are shown. Main effects of weaning strategy by time interaction (W*T). *Indicates difference (P < 0.05) in RFT among times between weaning strategy. a,b,cWithin a group, means without a common letter differed (P < 0.05).
Figure 6.
Figure 6.
Mean ± SEM plasma NEFA, BHB, Urea, and IGF-I concentration in primiparous and multiparous Nelore cows that were weaned at early (150 d of age) or at conventional (240 d of age) time points during the previous production cycle. Main effects of weaning strategy (W), dam’s parity (D), time (T), and interactions (W*T and D*T) that were significant or approached significance are shown. *Indicates difference (P < 0.05) in weight among times. a,b,cWithin a group, means without a common letter differed (P < 0.05).
Figure 7.
Figure 7.
Proportion (%) of pregnant Nelore cows after first TAI and second TAI, or cumulative pregnancy rate [1stTAI + 2ndTAI] in early and conventional groups. *Significant differences were declared at P ≤ 0.05 and a tendency was declared when P ≤ 0.1 and P > 0.05.
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