Performance of calves in dry season feedlot according to genetic group and sex

doi:10.21203/rs.3.rs-4732062/v1

The aim of this study was to evaluate the feedlot strategy for beef calves as an alternative during the dry season, as well as differences in the performance between genetic groups: Caracu, Nellore, crossbred Caracu x Nellore, and sex. Fifty-four calves were distributed in a completely randomized design in a 3x2 factorial scheme. The diet was formulated for an average body weight gain of 0.5 kg/day. Average daily gain (ADG), dry matter intake (DMI), and feed conversion ratio (FCR) were evaluated. The data was subjected to analysis of variance, and when significant at the 5% level, means were compared using the SNK (Student-Newman-Keuls) test. There was an interaction (p<0.05) between genetic group and sex only for ADG. Crossbred Caracu x Nellore calves male had the highest (p<0.05) gain (0.75 kg/day). Caracu males and crossbred females did not differ (p>0.05) from each other, showing gains of 0.66 and 0.63 kg/day, respectively. Caracu females had intermediate gains (p<0.05) of 0.52 kg/day. While the lowest gains were in Nellore, males and females, which did not differ from each other (p>0.05) and showed 0.42 and 0.38 kg/day, respectively. There was an effect (p<0.05) due to genetic groups, with crossbred calves showing higher (p<0.05) gain (0.70 kg/day), followed by Caracu (0.58 kg/day) and Nellore (0.41 kg/day). There was effect (p<0.05) on DMI (5.86 versus 6.58 kg/animal/day) and FCR (13.76 versus 12.39 kg of DM/kg of body weight gain) for males and females, respectively. There was also effect (p<0.05) of DMI for genetic groups, with crossbred and Caracu calves not differing (p>0.05) from each other (6.80 and 6.43 kg/animal/day), respectively, and having higher (p<0.05) intake than Nellore calves (5.91 kg/animal/day). For FCR, there was also effect (p<0.05) for genetic groups, with crossbred calves showing better (p<0.05) FCR (9.83 kg of DM/kg of gain), followed by Caracu (11.16 kg of DM/kg of gain), which in turn had better (p<0.05) FCR than Nellore (14.95 kg of DM/kg of gain). Given these results, males are superior to females in weight gain, feed conversion and also have lower feed costs in feedlot. Considering these same aspects, crossbred Caracu x Nellore calves have better performance than calves of these pure breeds. The worst performance was of the Nellore Calves.

intensive rearing

nutritional strategy

seed straw.

The rearing phase of beef calves in tropical regions coincides with the dry season, which implies low quality of pastures. This leads to an inadequate supply of nutrients, compromising the performance of the cattle (Nishimura, et al., 2023; Poppi, et al., 2018).

Therefore, confining calves during the rearing phase in dry seasons is a strategy that can accelerate the growth of these animals and increase profitability (Pacheco, et al., 2020). In addition, it can contribute to increasing the longevity of pastures, since pastures will have enough time for more vigorous regrowth (Pereira et al., 2020).

Higher costs with feed and feedlot management may be a limiting factor for adopting this practice. However, the economic viability of an activity should not be assessed solely by the magnitude of its cost. Increased productivity, a factor directly associated with revenue generation, should also be taken into consideration when making decisions. In the case of beef cattle farming, this productivity is measured by body weight gain and reproductive rates. In young animals, the age at reproduction is also directly related to this weight gain.

Several factors can affect the productive performance of young cattle, including breed and sex (Daza et al., 2014; Bureš et al., 2012). This is because variables such as dry matter intake, weight gain and feed conversion ratio can be influenced by the breed and sex of the calves (Daza et al., 2014; Bureš et al., 2012). Therefore, correct decision-making about the advantages of confining cattle after weaning depends on a performance analysis accompanied by some economic evaluation. Breed and sex factors should be studied, since the viability of this practice for a given breed or sex does not necessarily imply generalization of the strategy for both sexes and several breeds.

The Nellore and Caracu breeds are the most adapted to tropical environments that are characterized by distinct wet and dry seasons, in addition to nutritionally poor pastures (McManus et. al, 2009; Fraga et al., 2003). Therefore, dry season calves’ feedlots studies of these breeds and their crossbreeds are necessary. Thus, our objective was to evaluate the effect of sex and genetic group on the productive performance of beef calves subjected to confinement after weaning in the dry season.

Experimental conditions, animals and analyzes

54 calves (uncastrated males and females) aged 7 ± 1 months were used. The average initial body weights were: Caracu male: 191 ± 6 kg; Caracu female: 183 ± 8; Nellore male: 185 ± 9; Nellore female: 172 ± 12; crossbreed Caracu x Nellore male: 208 ± 9 and crossbreed Caracu x Nellore female: 194 ± 11 kg. Calves started the experimental protocol immediately after traditional weaning. There were 18 calves (nine males and nine females) from each genetic group (Caracu, Nellore and crossbred Caracu x Nellore).

The genetic group and sex were distributed in a completely randomized design, in a 3x2 factorial (three genetic groups, two sexual classes), being: T1: Caracu male; T2: Caracu female; T3: Nellore male; T4: Nellore female; T5: Caracu x Nellore crossbreed male and T6: Caracu x Nellore crossbreed.

The calves were housed in 18 collective pens, with 15 m² per calf. Three calves of the same genetic group and sex were housed in each pen equipped with feeders with1 linear meter/calf and drinking troughs

All calves received the same diet, formulated to meet the requirements of an animal with a body weight of 200 kg and an expected gain of 0.5 kg/day, in accordance with the NASEM recommendations (2016). The roughage was waste from forage seeds crop (Brachiaria brizantha cv. MG4), processed industrially. This waste is made up of stems, leaves and remains of inflorescences, which are finely ground and, through pressure and temperature, are densified in the form of "briquettes" (briquettes of hay - Briqfeno®). Corn bran, soybean meal, urea and premix made up the concentrate. The chemical composition of the diet and its components are presented in Table 1.

There were 21 days of adaptation to the diet, then the 90-day experimental period began, in which weighing was carried out every 30 days. The diet was composed of 66% processed seed residue (briquettes of hay) and 34% concentrate and was offered ad libitum to the calves with weekly adjustment to have leftovers in the feeders in the proportion of 5% of the quantity offered. The diet was fed to the calves in two daily meals (one at 8:00 am and the other at 3:00 pm. The leftovers were collected and weighed the next day in the morning.

Samples of the ingredients and the total mixed ration and leftovers were collected to determine the dry matter (DM) and crude protein (CP) according to the AOAC methodology (1990). Total digestible nutrients (TDN) were estimated according to the equation proposed by Weiss et al. (1992).

The body weight gain in the period was obtained by the difference between the initial and final body weight of each animal during the 90 days, and the average daily gain (kg/calf/day) was calculated using the following formula: (Final Weight – Initial Weight/90 days). The dry matter intake by the animals was determined by the difference between the amount offered and the leftovers from each pen with three animals. Feed conversion ratio was obtained by follows: F.C.R. = feed given/body weight gain, both in kg/day.

Statistical analysis

The statistical models were as follows: $\:{y}_{ijk}=\:\mu\:+\:{\alpha\:}_{i}+\:{\tau\:}_{j}+\:{\alpha\:\tau\:}_{ij}+\:{e}_{ijk}$, where:

$\:{y}_{ijk}$ is the response variable for the i-th genetic group in the j-th sex in the k-th repetition, $\:\mu\:$ represets the unknown population mean, $\:{\alpha\:}_{i}$ is the effect of factor genetic group, $\:{\tau\:}_{j}$ is the effect of factor sex, $\:{\alpha\:\tau\:}_{ij}$represents the interaction of the two factors and $\:{e}_{ijk}$ is the independent errors.

The data was subjected to analysis of variance and, when significant, comparisons between means were performed using the Student-Newman-Keuls (SNK) test at a 5% level of significance.

Economic assessment

An evaluation of the cost per kg of calf produced was carried out depending on the cost of the diet, dry matter intake and feed conversion of calves of different genetic groups and sex. For food cost composition, the price of each ingredient, the inclusion of the ingredient in the diet and the dry matter intake were used.

The cost of diet per calf/day was obtained using the following formula: DMI x DMC, where DMI: dry matter intake and DMC: diet dry matter cost. Multiplying the daily cost of food calf by 90 days, the cost/calf in the experimental period was obtained.

The calculation of the diet cost per kg of weight gained for the genetic group and sex was obtained as follows: Diet cost per calf (of each genetic group and each sex) in the period/Weight gain per calf in the period.

To calculate the cost of food, the prices for corn and soybean meal in July 2023, data made available by CEPEA/ESALQ/USP was considered. The prices of premix, urea and briquettes of hay were those purchased for the experiment. All prices are calculated in Brazilian currency BRL.

There was interaction (p<0.05) between genetic group and sex only for the average daily gain (ADG). The crossbred Caracu x Nellore male calves had the highest (p<0.05) gain. The Caracu males and crossbred Caracu x Nellore females did not differ (p>0.05) from each other and had a higher (p<0.05) ADG than the Caracu females. The lowest gains (p<0.05) were from the Nellore male and female calves, which did not differ from each other (p>0.05) (Table 2).

Dry matter intake (DMI) and feed conversion (FCR) were affected (p<0.05) by both the genetic group and the sex of the calves (Table 5), and the DMI of males was higher (p<0.05) than that of females. The Caracu calves and those from Caracu x Nellore crossbreeding did not differ (p>0.05) from each other and had higher (p<0.05) DMI than the Nellore calves (Table 3).

The feed conversion ratio (FCR) of males was better (p<0.05) than that of females, regardless of the genetic group. Also, regardless of the sex, the calves from the Caracu x Nellore cross had better conversion (p<0.05), followed, respectively, by the Caracu and Nellore (Table 4).

The diets of males were more expensive than the diets of females. However, the females had lower cost per kg of body weight produced. Among the genetic groups, the more expensive feeding cost was with F1 calves (Caracu x Nellore), followed by Caracu and then Nellore. However, despite these higher costs with feeding, the Caracu x Nellore crossbreed was cheapest per kg of body weight produced (Table 5).

Generally, the greater weight gain of males compared to females is due to sexual dimorphism. Physiologically, this greater gain in non-castrated males occurs due to the greater deposition of protein and less fat in tissue (PURCHAS, 1991), a process stimulated by testosterone (FLETCHER et al., 1986). The hormonal relationship for the better performance of males was also reported by BERG & BUTTERFIELD (1976), who attributed the differences in the growth form, distribution and composition of tissues to androgenic hormones.

We observed this better performance of males in the crossbred Caracu x Nellore and Caracu groups, which was also reported by Gottschall et al. (2018) and Marcondes et al. (2008). However, we did not find any difference in weight gain according to sex for Nellore animals, which may be attributed to the late puberty of zebu animals, which normally occurs between 14 and 21 months (CARDOSO, 1977). These steroid hormones, which affect body development to a different extent between sexes, are expressed more pronouncedly after puberty. This may explain the similar weight gain between male and female Nellore calves.

The similar performance between crossbred Caracu x Nellore females and Caracu males can be attributed to heterosis and the high genetic value of the Caracu animals used in this study, reflecting the ADG capacity of the crossbred females.

Maximum heterosis resulting from the crossing of two pure breeds can promote the improvement of the average performance of the parental breeds. The role of heterosis in improving the performance of beef cattle is well understood and reported in the literature (Mendonça et al., 2021; Perotto et al., 2000; Vaz et al., 2001; Leal et al., 2018). Restle et al. (2000) evaluated the performance during the growth phase of pure Charolais, Nellore and Charolais x Nellore crossbred animals and found that the crossbred animals were superior to the average of the pure breeds. The gain of 0.70 kg/calf/day found in our study is similar to that reported by Fernandes et al. (2004), who worked with Caracu x Zebu crossbreds with body weight close to 205 kg, in a confinement system.

One of the explanations for the greater dry matter intake by males may be the greater requirement of nutrients to support greater body weight gain compared to females (Bailey and Duff, 2005). This could be corroborated with the DMI and ADG found in this study. However, sex is not the only determining factor on DMI in beef cattle (NRC, 2000), since there are reports in the literature where no differences were found in the DMI of males and females or even greater DMI in females. It seems that DMI is more closely linked to weight and body composition, which makes it challenging to compare DMI between different studies.

The higher DMI of Caracu calves compared to Nellore calves can be attributed to differences in nutritional requirements, since taurine breeds have a higher net energy requirement for maintenance, due to their greater body weight.

Regardless of sex or genetic group, the dry matter intake was higher than the predicted (5 kg/calf/day), which can be attributed to the characteristics of the roughage used. Due to the smaller particle size of the hay briquettes (due to the fine grinding of the hay for the briquetting process), its passage rate through the rumen is accelerated, resulting in greater DMI.

Regarding feed conversion, males required a smaller amount of feed ingested on a dry matter basis to obtain 1 kg of live weight gain. Other authors have also demonstrated a better conversion for males compared to females (SANTOS, 2014). This result can be attributed to factors related to the composition of the gain, as males deposit a greater proportion of muscle tissue than females, especially in the growth phase in which the animals were in this study (LANNA, 1997).

For genetic groups, when relating gain to feed intake, it was found that crossbred animals showed greater efficiency compared to Caracu animals. Although both groups had similar DMI, crossbred calves converted more dry matter into body weight, which is justified by the greater ADG. Permigiani (2018) evaluated feed efficiency in genetic groups: taurine, zebu and adapted taurine with an average age of 8 ± 2 months and reported greater feed efficiency for taurine followed, respectively, by adapted taurine and zebu. These results are consistent with ours, evidencing the superiority of Caracus (adapted breed) in relation to Nellore.

Despite the lower dry matter intake by females, the cost per body weight gain was higher, at R$15.69/kg of gain, while for males this cost was R$14.63. This difference in cost per kg of body weight gain is reflected in profitability, giving an advantage to confinement of males. However, females also showed good performance when compared to performance in pasture systems in the dry season.

For the genetic groups, we observed that crossbred calves had the highest daily cost with the diet (R$ 8.37). This was due to consumption, however, statistically the Caracu and crossbred calves did not differ in this regard. Therefore, it is possible to infer that the crossbred calves demonstrated a better relationship between cost and weight gain, since they also presented better feed conversion. On the other hand, although the diet of the Nellore calves was cheaper, they had the lowest weight gain, as a result of the lower feed conversion efficiency.

Considering the feedlot strategy for rearing in the dry season in tropical climates, the ADGs were satisfactory. They were higher than the average gains obtained in rearing calves grazing during the dry season receiving protein supplementation with an intake of 1g/kg of body weight. Evangelista et al. (2020) reported an ADG of 0.316 kg and Cordeiro et al. (2022) an ADG of 0.182 kg. Feedlot at the beginning of the rearing phase can be an alternative to enable greater gains during this period, which coincides with low forage availability (dry season). It is also a strategy to shorten the production cycle through increasing of performance.

Efficient rearing during the dry season eliminates the need for compensatory gain during the wet season. The practice of compensatory gain in beef cattle farming is not always effective, since a considerable part of this gain comes from the increase in organs and viscera and not in the carcass. In addition, the feedlot during the rearing phase can result in an increase in carcass gain and better performance of the animals during the finishing phase, as demonstrated by Nascimento (2021). However, it is essential that the nutritional plan after the first dry season that calves have experienced is designed to achieve greater weight gains (ROTH et al., 2017). Therefore, adopting confinement during the dry season can reduce the time until slaughter and the mating age of females by at least one year, regardless genetic group or sex.

Males are superior to females in weight gain, feed conversion and also have lower feed costs in feedlot. Considering these same aspects, crossbred Caracu x Nellore calves have better performance than calves of these pure breeds. The worst performance was of the Nellore Calves.

ACKNOWLEDGMENTS

The authors thank the Coordination for the Improvement of Higher Education Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES), for support with scholarship to graduate student.

Data Availability

“The datasets generated during and/or analysed during the current study are not publicly but are available from the corresponding author on reasonable request.”

Author contributions

“All authors whose names appear on the submission: 1) made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work; 2) drafted the work or revised it critically for important intellectual content; 3) approved the version to be published; and 4) agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.”

“Conceptualization: [Ana Clara da Silva Severino, Severino Delmar Junqueira Villela, Fernando de Paula Leonel]; Data curation: [Bruna Cardoso Braga, Raphael dos Santos Gomes, Cláudio Manoel Teixeira Vitor, Fernando de Paula Leonel]; Formal Analysis: [Raphael dos Santos Gomes, Cláudio Manoel Teixeira Vitor, Fernando de Paula Leonel]; Funding acquisition: [Ana Clara da Silva Severino, Fernando de Paula Leonel]; Investigation: [Ana Clara da Silva Severino, Raphael dos Santos Gomes, Severino Delmar Junqueira Villela, Fernando de Paula Leonel]; Methodology: [Ana Clara da Silva Severino, Bruna Cardoso Braga, Cláudio Manoel Teixeira Vitor, Fernando de Paula Leonel]; Project administration: [Ana Clara da Silva Severino]; Resources: [Fernando de Paula Leonel]; Software: [Bruna Cardoso Braga]; Supervision: [Severino Delmar Junqueira Villela, Cláudio Manoel Teixeira Vitor]; Validation: [Severino Delmar Junqueira Villela, Raphael dos Santos Gomes, Fernando de Paula Leonel]; Visualization: [Severino Delmar Junqueira Villela, Fernando de Paula Leonel]; Writing - original draft preparation: [Ana Clara da Silva Severino, Bruna Cardoso Braga, Fernando de Paula Leonel]; Writing - review and editing: [Ana Clara da Silva Severino, Bruna Cardoso Braga, Raphael dos Santos Gomes, Cláudio Manoel Teixeira Vitor, Severino Delmar Junqueira Villela, Fernando de Paula Leonel].”

Compliance with Ethical Standards

“The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.”

Funding

“The authors thank the Coordination for the Improvement of Higher Education Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES), for support with scholarship to graduate student.”

“The authors have no relevant financial or non-financial interests to disclose.”

Competing interests

“The authors declare they have no financial interests.”

Ethics approval

“This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Committee on Animal Use and Care at the Minas Gerais Agricultural Research Company (CEUA EPAMIG01/2019)”.

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Table 1– Chemical composition of the concentrate, roughage and diet

Items	DM (g/kg)	CP (g/kg)	TDN(g/kg)	Fiber (g/kg)
Concentrate	913	220	780	131
Roughage	918	50.5	450	735
Diet (total mixed ration)	916	108	562	530

DM: dry matter; CP: crude protein; TDN: total nutrients digestive (estimate); Fiber: aFDNmo:

Table 2 - Average daily gain (ADG), in kg, of calves according to genetic group and sex class during the 90-day confinement period

Genetic group	Sex	ADG	95% lower limit	95% upper limit
Nellore	Female	0.38^d	0.34	0.42
Nellore	Male	0.42^d	0.37	0.46
Caracu	Female	0.52^c	0.49	0.55
Caracu	Male	0.66^b	0.62	0.70
F1 Caracu x Nellore	Female	0.63^b	0.54	0.72
F1 Caracu x Nellore	Male	0.75 ^a	0.69	0.81

F1: crossbreed Caracu x Nellore;

*Within column, values followed by different letters are significantly different (P < 0.05) by Newman-Keuls test.

Table 3 - Dry matter intake (DMI) during 90 days of the experiment according to the genetic group and sex of the calves

Genetic group	DMI (kg/calf/day)	95% lower limit	95% upper limit
Nellore	5.91^b	5.63	6.20
Caracu	6.43^a	6.18	6.68
F1:Caracu x Nellore	6.80^a	6.47	7.13
Sex
Female	5.86^b	5.61	6.11
Male	6.58^a	6.31	6.84

F1: crossbreed Caracu x Nellore;

*Within column, values followed by different letters are significantly different (P < 0.05) by Newman-Keuls test.

Table 4 - Feed conversion ratio (FCR) during 90 days of experiment according to genetic group and sex of calves

Genetic group	FCR	95% lower limit	95% upper limit
Nellore	14.95^a	14.43	15.47
Caracu	11.16^b	10.46	11.86
F1:Caracu x Nellore	9.83^c	9.32	10.34
Sex
Female	13.76^a	12.67	14.86
Male	12.39^b	11.18	13.59

F1: crossbreed Caracu x Nellore; FCR: Feed given / Animal weight gain, both in kg.

*Within column, values followed by different letters are significantly different (P < 0.05) by Newman-Keuls test.

Table 5- Daily dry matter intake, body weight gain, daily feed cost, feed cost during the period and cost per kilo of body weight gained according to genetic group and sex

Genetic Group	Dry matter intake (kg/calf/day)	Body weight gain (kg)	Calf diet cost (BRL/day)	Calf diet cost/period (BRL/90 days)	Cost of gain (BRL/kg of BW)
Nellore	6.45	36.9	7.28	655.03	17.75
Caracu	7.02	52.2	7.92	712.66	13.65
F1: Caracu x Nellore	7.42	63.0	8.37	753.67	11.96
Sex
Male	7.18	49.5	8.10	729.29	14.73
Female	6.39	41.4	7.22	649.49	15.69

Performance of calves in dry season feedlot according to genetic group and sex

Status:

Version 1

Abstract

INTRODUCTION

MATERIAL AND METHODS

Experimental conditions, animals and analyzes

Statistical analysis

Economic assessment

RESULTS

DISCUSSION

Declarations

References

Tables

Status:

Version 1