Effect of some non-genetic factors on the productivity and profitability of Holstein Friesian dairy cows

Background and Aim: Milk yield (MY) is one of the main factors that affect the economic profitability of dairy farms. Thus, increasing the MY per animal and decreasing the feed cost can lead to economic gains, so the objective of this study was to evaluate the effect of dry period length (DPL), days open (DO), and days in milk (DIM) on the productivity and profitability of dairy cow farms. Materials and Methods: Data used in this study were taken from 3095 lactation records of Friesian dairy cows of private and governmental sectors. The data were classified into 4 DPL categories: DPL1 <45 days; DPL2 45-60 days; DPL3 61-75 days, and DPL4 >75 days, 3 DO categories: DO1 ≤90 days; DO2 91-110 days and DO3 >111 days, and 8 DIM categories: DIM1 180-210 days; DIM2 211-240 days; DIM3 241-270 days; DIM4 271-300 days; DIM5 301-330 days; DIM6 331-360 days; DIM7 361-447 days; and DIM8 >447 days. Results: The average net profit (NP) was significantly different (p<0.05) among different categories of DPL, DO, and DIM in both production sectors, where high estimates of NP were calculated for DPL3 (30667.3 EGP), and it was the lowest for DPL1 (19690.6 EGP). DO2 had the highest NP (30754.1 EGP), while DO3 had the lowest NP (24875.5 EGP). DIM3 had the highest NP (29569.3 EGP), while DIM8 had the lowest NP (19528.4 EGP). Conclusion: Finally, we can conclude that DPL 61-75 days, DO 91-110 days, and DIM 241-270 days had the highest level of total MY, total return, and NP. Private dairy cow farms achieve a higher level of NP than governmental ones under subtropical Egyptian conditions.


Introduction
Cow is a dairy animal that plays a great role in milk production all over the world [1]. The performance of dairy cows in terms of fertility and milk production is the key to farm profitability [2]. Major environmental factors that may affect milk production and animal performance are production sector, calving season, and management [3]. Several studies showed that the dairy production sector affects milk yield (MY) significantly [4,5]. This might be due to variations in the level of management [6]. Milk production during a specified period of lactation is usually used as an indicator for dairy cow performance. A common measure is MY per lactation (total milk yield within 305 days [305-MY]) or daily milk yield (DMY). Furthermore, days in milk (DIM) can be of interest [7]. Lactation length is the period between two successive calvings during which cows are able to produce milk or lactate [8]. Lactation length is an important production trait as it affects the total MY. A lactation period of 305 days is commonly accepted as a standard [9]. Furthermore, the dry period length (DPL) plays an important role in preparations for calving, milk production, and dairy cow health. Dry period is called a resting period in which the udder is prepared for the next lactation. Enough management of this period optimizes the mammary gland and fetus development in the last month of pregnancy, as well as the milk production of the next lactation. This also has a positive effect on cows' metabolic health and reproductive performance [10]. Number of days open (DO) was reduced, and first ovulation occurred earlier in cows with a shortened DPL [11]. Increasing the DPL leads to decreasing the total returns (TR) and increasing production costs and lowering the net profit (NP) [12]. However, optimal DPL may differ depending on herd size, parity number, and level of milk production among other factors [13,14]. Longer DPL decreases the annual production of animal by increasing it's DO [15]. DO is the period between calving and successful mating [16]. It is used to assess the reproductive performance and to make an economical decision in the dairy herd [17]. It is a complex trait that is affected by many factors such as season of calving, parity, management policies, herd size, production level, and artificial insemination (AI) techniques [18].
Copyright: Abd-El Hamed and Kamel. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/ by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Available at www.veterinaryworld.org/Vol.14/January-2021/31.pdf Conception rate (CR) (S/C) directly determines the total herd profitability. Hence, to maximize the farm profitability, it is very important to increase the CR up to maximum level [19], reduce the cost of AI, and shorten the DO [20]. Improving the level of management is required for optimal reproduction performance [21].
To improve the productivity and profitability of dairy cows, it is necessary to study some variables that affect animal's performance and farm economy. The aim of this study was to evaluate the effect of DPL, DO, and DIM on the productivity and profitability of governmental and private dairy cow farms under subtropical Egyptian conditions.

Ethical approval
The study was approved by the Committee of Animal Care and Welfare, Benha University, Faculty of Veterinary Medicine, Egypt (BUFVTM:03-07-20).

Study period and location
The study was carried out through field surveys in different regions of dairy cow farms (Cairo and EL Sharkia governorates) during the period that extended from summer 2016 to winter 2019 on random samples of private and governmental production sectors.

Animals and management
Data used in this study were estimated from 3095 lactation records of Holstein Friesian dairy cows. All animals on the farm were housed in free-stall shaded open yards, bedded with sand floor, and supplied with a cool spraying system during the summer season. Animals were grouped according to average DMY into fresh (from calving day till 60 days postpartum), high, medium, and low milk-producing cows. All groups of cows were fed a balanced total mixed ration, although the diet composition differed according to the region, sector, and management. Water was freely available at all times. Lactating cows were machine-milked 2 times per day, and milk production was recorded at each milking. The collected data were milk production records and reproduction records.

Productive traits
They included 305-MY, DIM, DMY, DPL, and calves sales. 305-MY=305×Total MY/DIM [22,23]. DMY=Total MY per cow per lactation/DIM. DPL is defined as the number of days between the dry-off date and the subsequent parturition date [24,25]. Calves sales is the price of 1-day-old calf or calves added to a herd.

Reproductive traits
They included S/C (number of insemination doses till conception) calculated individually for each cow and DO.

Economic indices
They included calculations of costs and returns: 1. Fixed costs=Depreciation cost of building+Depreciation cost of animal+Depreciation cost of parlor [23].

Statistical analysis
All statistical procedures were performed using the computer programs IBM SPSS/PC + "version 23" [31]. Preliminary Levene's test was performed to ensure the homogeneity of variances among groups. The general linear model procedure was used to analyze the productive, reproductive, and economic measures for each animal according to fixed continuous variables (DPL, DO, and DIM). Duncan's multiple range test was used to test differences among means.

Effect of DPL on subsequent MY and reproductive traits of Holstein Friesian dairy cows
Data summarizing results for the effect of DPL on subsequent DMY, 305-MY, DO, and S/C are included in DPL within both production sectors had a significant effect on S/C. Reproductive indices of cows were decreased as the DPL increased. According to the four DPL categories, S/C was 3.6, 3.7, 4.0, and 4.7, respectively. The highest value was for private sector cows at DPL >75 days (S/C value was 5.2), while the lowest value was for the governmental sector at DPL <45 days (S/C value was 3.1). Concerning the results of the effect of DPL on the current DO, the DPL within both production sectors had a significant effect on current DO. Regarding the four DPL categories, current DO values were 170.1, 198.1, 211.1, and 246.7 days, respectively. The longest DO value was for the governmental sector at DPL >75 days (265.4 days), while the shortest value was for governmental sector at DPL <45 days (163.4 days).

Effect of DPL on economic indices
Data summarizing results for the effect of DPL on total variable cost (TVC), TC, TR, and NP are represented in Table- DO within both production sectors had a significant effect on TR and NP. According to the three DO categories, TR and NP were 62675.7,

Discussion
The aim of this study is to evaluate the effect of DPL, DO, and DIM on the productivity and profitability of dairy cow farms. Regarding the effect of  DPL within production sectors on the subsequent MY and reproductive traits, there was a significant effect of DPL within different production sectors on DMY and 305-MY. The greatest yield was attained for the private sector cows at DPL 61-75 days , while the lowest yield was for the governmental sector cows at the shortest drying period length DPL <45 days. These results might be because a short dry period does not provide enough mammary gland regeneration; also very long DPL extends the time with no milk income and increases the possibility of over-conditioned cows [32]. This result agreed with Van Knegsel et al. [10], who found that shortening the drying period reduces milk production. Furthermore, El-Tarabany [29], O'Hara et al. [33] showed that there was a reduction in the MY at either extremely short or long DPL. On the other hand, some studies concluded that postpartum MY is not affected by a shortened DPL [34]. A longer DPL reduced the MY in that lactation, thus allowing the diversion of dietary energy to tissue gain, which give higher MY in the next lactation [35], also Metin Kıyıcı et al. [36] recorded that longer DPL have a positive effect on 305-MY, although shorter DPL practices have a better outcome for pregnancy ratios of the first insemination. Regarding the significant effect of DPL within both production sectors on S/C, the reproductive indices of cows were decreased as the DPL increased; the highest value was for private sector cows at DPL >75 days, while the lowest value was for governmental sector at DPL <45 days. This result is in accordance with Grummer et al. [37], who explained that reducing DPL to 28 or zero days, decreases days to first ovulation, and increases first service CR. Furthermore, Metin Kıyıcı et al. [36] concluded that DPL had a significant effect on the S/C (p<0.01). The greatest pregnancy ratio (53.0%) in the first insemination was obtained from DPL group ≤40 days and the lowest pregnancy ratio (30.8%) was obtained from DPL group 61 to 70 days. DPL significantly affected current DO in private and governmental sectors. The longest DO value was for the governmental sector at DPL >75 days, while the shortest value was for the governmental sector at DPL <45 days. This result agreed with Watters et al. [38] and Chen et al. [39], who concluded that shortening the DP increases the reproductive efficiency by shortening the time to first ovulation, reducing numbers of ovular cows, shortening DO, and improving fertility.
Abdeltawab et al. [40] recorded that cows with DPL <40 days had the best intervals reproductive indices compared with that recorded for both standard and long DP. Concerning the effect of DPL on the economic indices, DPL within both production sectors had a significant effect on TVC and TC. The highest TVC value was for the private sector at DPL 61-75 days. Furthermore, the highest TC value was for private sector at DPL 45-60 days, while the lowest TVC and TC values were estimated for governmental sector at DPL <45 days . These results might be due to short DPL had a lower milk production in the next lactation due to less developed mammary glands, as the early involution of the mammary gland might be inhibited when the cow is dried off later in lactation and closer to parturition [41], consequently the feed cost will decrease, which represents the highest level of TVC. This result agreed with Sosa et al. [12], who recorded that short DP had a lower TVC than long DPL. DPL significantly affected TR and NP in private and governmental sectors. DPL 61-75 days for the private sector had the highest TR and NP values, while DPL <45 days for the governmental sector had the lowest TR and NP values. These results were attributed to the high level of milk production for cows within DPL 61-75 days. This result in accordance with Sosa et al. [12], who concluded that DPL 60-91 days had the highest TR and NP. In responding to the production sector, the private sector had a higher level of NP than governmental one; this might be due to managemental variation. Regarding the effect of DO within both production sectors on the MY, and reproductive traits. Current DO have a significant effect on DMY and 305-MY, the greatest yield was attained for private sector cows at DO 91-110 days, while the lowest  [42], who concluded that the total MY of a lactation was affected by DO. [20] Found that, when CR increased, number of AIs, DO, and DIM decreased, while annual MY increased. On the contrary Němečková et al. [43] recorded that the calving interval (CI) higher than 440 days (DO higher than 110 days) had the highest level of milk production than short CI. DO affected economic indices in private and governmental sectors. Current DO had a significant effect on TVC and TC. TVC value was the highest for the private sector at DO ≤90 days, while the lowest value was for the governmental sector at DO >111 days; on the other hand, TC for the private sector had the highest value at DO 91-110 days, while the lowest TC value was for the governmental sector at DO >111 days. These results in the same line with Meadows et al. [44], who explained that TVC and TC increased due to increasing the expenditures that were spent on infertility treatments, costs of feed consumption, and costs of decreasing DMY per extended DO especially after 110 days after calving. In responding to a dairy farm, the highest cost is the animal feed cost [45]. In responding to the significant effect of current DO within both production sectors on TR and NP, private sector at DO 91-110 days had the highest TR and NP, while governmental sector had the lowest values at the longest DO length DO >111 days. These results might be due to increasing costs of infertility problems treatment, costs of feed consumption, and costs of decreasing DMY per extended DO especially after 110 days after calving, at which the break-even point occurred. This result in accordance with Ahme [23], who concluded that the average profit of Holstein Friesian cow increased gradually till reach to maximum level around 110 days after calving then decreased again. Furthermore, Mengistu and Wondimagegn [21], Lehmann et al. [46], and Kidane et al. [47] reported that DO is the part of the CI, and longer DO reduced the farm profitability. Zahed et al. [48] concluded that farm profitability increased by shortening CI, and prolonging this period for 1 day causes a financial loss for the dairy farm. This may be due to the increasing value in milk income. Milk production is a major source of income for the farm. TVC for long CI is higher (p<0.01) than that of medium and short CI. This difference is mainly due to the feed cost, as it is the main component of TVC and therefore long CI more expensive than other levels. This agreed with Kidane et al. [47], who explained that DO is a part of the CI, longer DO associated with decreased profitability. DIM [49] and Hossen et al. [50] who found that MY increased by increasing the lactation length.

Conclusion
The results of our study concluded that DPL 61-75 days, DO 91-110 days, and DIM 241-270 days had the highest level of total MY, TR, and NP. Private dairy cow farms achieve a higher level of NP than governmental ones under subtropical Egyptian conditions.